[진단측정기술]General Electric Company 대 University of Virginia Patent Foundation 간의 진단측정기술 관련 특허 분쟁

발생일자 2014.12.08

사건번호 2:14-cv-01529

법원국가 UNITED STATES OF AMERICA

관할법원명 D.C.E.D.Wisconsin(지방법원)

침해권리 특허

원고명 General Electric Company ( 미국 / 외국기업 )

피고명 University of Virginia Patent Foundation ( 미국 / 외국기업 )

소송유형 Declaratory Judgement

분쟁내용

[General Electric Company v. University of Virginia Patent Foundation] 사건번호 2:14-cv-01529에 따르면 원고 General Electric Company는 피고 University of Virginia Patent Foundation을 상대로 특허 USRE44644, US7164268을 침해하지 않았다는 이유로 미국 위스콘신 동부 지방법원에 소를 제기하였다.

분쟁결과 분쟁중

산업분류 장치산업 > 진단측정기술

계쟁제품 Signa HDxt 1.5T and 3T platforms - Cube products (Magnetic resonance imaging ("MRI") systems) (Declaratory Judgment)

지재권번호/명칭

USRE44644 Method and apparatus for spin-echo-train MR imaging using prescribed signal evolutions

US7164268 Method and apparatus for spin-echo-train MR imaging using prescribed signal evolutions 

Method and apparatus for spin-echo-train MR imaging using prescribed signal evolutions

A magnetic resonance imaging "MRI" method and apparatus for lengthening the usable echo-train duration and reducing the power deposition for imaging is provided. The method explicitly considers the t1 and t2 relaxation times for the tissues of interest, and permits the desired image contrast to be incorporated into the tissue signal evolutions corresponding to the long echo train. The method provides a means to shorten image acquisition times and/or increase spatial resolution for widely-used spin-echo train magnetic resonance techniques, and enables high-field imaging within the safety guidelines established by the Food and Drug Administration for power deposition in human MRI. 

We claim:

1. A method for generating a spin echo pulse sequence for operating a magnetic resonance imaging apparatus for imaging an object .[.that permits at least one of lengthening usable echo-train duration, reducing power deposition and incorporating desired image contrast into the tissue signal evolutions.]., said method comprising: a) providing contrast-preparation, said contrast-preparation comprising generating at least one of at least one radio-frequency pulse, at least one magnetic-field gradient pulse, and at least one time delay, whereby said contrast preparation encodes the magnetization with at least one desired image contrast; b) calculating flip angles and phases of refocusing radio-frequency pulses that are applied in a data-acquisition step, wherein said calculation provides desired prescribed signal evolution and desired overall signal level .Iadd.that permit, during said data-acquisition step, at least one of lengthening usable echo-train duration, reducing power deposition and incorporating desired image contrast into the tissue signal evolutions.Iaddend., said calculation comprises: i) selecting values of T1 and T2 relaxation times and selecting proton density; ii) selecting a prescribed time course of the amplitudes and phases of the radio-frequency magnetic resonance signals that are generated by said refocusing radio-frequency pulses; and iii) selecting characteristics of said contrast-preparation step, said data-acquisition step and a magnetization-recovery step, with the exception of the flip angles and phases of the refocusing radio-frequency pulses that are to be calculated; and c) providing said-data acquisition step based on a spin echo train acquisition, said data-acquisition step comprises: i) an excitation radio-frequency pulse having a flip angle and phase; ii) at least two refocusing radio-frequency pulses, each having a flip angle and phase as determined by said calculation step; and iii) magnetic-field gradient pulses that encode spatial information into at least one of said radio-frequency magnetic resonance signals that follow at least one of said refocusing radio-frequency pulses; d) providing magnetization-recovery, said magnetization-recovery comprises a time delay to allow magnetization to relax; and e) repeating steps (a) through (d) until a predetermined extent of spatial frequency space has been sampled.

2. The method of claim 1, wherein said calculation of the flip angles and phases is generated using an appropriate analytical or computer-based algorithm.

3. The method of claim 1, wherein said calculation of the flip angles and phases is generated to account for.[.,.]. the effects of multiple applications of.[.:.]. said contrast-preparation, said data-acquisition and said magnetization-recovery steps, which are required to sample the desired extent of spatial-frequency space.

4. The method of claim 1, wherein a two-dimensional plane of spatial-frequency space is sampled.

5. The method of claim 1, wherein a three-dimensional volume of spatial-frequency space is sampled.

.[.6. The method of claim 1, wherein at least one of said contrast-preparation and magnetization-recovery steps is omitted..].

7. The method of claim 1, wherein said calculation step is performed once before one of said first contrast-preparation step and said first data-acquisition step.

8. The method of claim 1, wherein at least one of at least one said contrast-preparation step, at least one said data-acquisition step and at least one said magnetization-recovery step is initiated by a trigger signal to .[.synchronizes.]. .Iadd.synchronize .Iaddend.the pulse sequence with at least one of at least one external temporal event and at least one internal temporal event.

9. The method of claim 8, wherein said external and internal events comprise at least one of at least one voluntary action, at least one involuntary action, at least one respiratory cycle and at least one cardiac cycle.

10. The method of claim 1, wherein at least one of at least one radio-frequency pulse and at least one magnetic-field gradient pulse is applied as part of at least one of at least one said magnetization-preparation step and at least one said data-acquisition step is for the purpose of stabilizing the response of at least one of magnetization related system and said apparatus related hardware system.

11. The method of claim 1, wherein time duration varies between repetitions for at least one of at least one said contrast-preparation step, at least one said data-acquisition step and at least one said magnetization-recovery step.

12. The method of claim 1, wherein the time periods between consecutive refocusing radio-frequency pulses applied during said data-acquisition steps are all of equal duration.

13. The method of claim 1, wherein time periods between consecutive refocusing radio-frequency pulses applied during said data-acquisition steps vary in duration amongst pairs of refocusing radio-frequency pulses during at least one said data-acquisition step.

14. The method of claim 1 wherein all the radio-frequency pulses are at least one of non-spatially selective and non-chemically selective.

15. The method of claim 1, wherein at least one of the radio-frequency pulses is at least one of spatially selective in one of one, two and three dimensions, chemically selective, and adiabatic.

16. The method of claim 1, wherein during each said data-acquisition step, the phase difference between the phase for the excitation radio-frequency pulse and the phases for all refocusing radio-frequency pulses is .[.about.]. .Iadd.substantially .Iaddend.90 degrees.

17. The method of claim 1, wherein during each data-acquisition step, the phase difference between the phase for any refocusing radio-frequency pulse and the phase for the immediately subsequent refocusing radio-frequency pulses is .[.about.]. .Iadd.substantially .Iaddend.180 degrees, and the phase difference between the phase for the excitation radio-frequency pulse and the phase for the first refocusing pulse is one of .[.about.]. .Iadd.substantially .Iaddend.0 degrees and .[.about.]. .Iadd.substantially .Iaddend.180 degrees.

18. The method of claim 17, wherein the flip angle for the excitation radio-frequency pulse is .[.about.]. .Iadd.substantially .Iaddend.one-half of the flip angle for the first refocusing radio-frequency pulse.

19. The method of claim 1, wherein the spatial-encoding magnetic-field gradient pulses applied during each said data-acquisition step are configured so as to collect data, following each of at least one of the refocusing radio-frequency pulses, for one line in spatial-frequency space which is parallel to all other lines of data so collected, so as to collect the data using a magnetic resonance imaging technique selected from the group consisting of rapid acquisition with relaxation enhancement (RARE), fast spin echo (FSE), and turbo spin echo (TSE or TurboSE).

20. The method of claim 1, wherein the spatial-encoding magnetic-field gradient pulses applied during each said data-acquisition step are configured so as to collect data, following each of at least one of the refocusing radio-frequency pulses, for two or more lines in spatial-frequency space which are parallel to all other lines of data so collected, so as to collect the data using a magnetic resonance imaging technique selected from the group consisting of gradient and spin echo (GRASE) and turbo gradient spin echo (TGSE or TurboGSE).

21. The method of claim 1, wherein the spatial-encoding magnetic-field gradient pulses applied during each said data-acquisition step are configured so as to collect data, following each of at least one of the refocusing radio-frequency pulses, for one or more lines in spatial-frequency space, each of which pass through one of a single point in spatial-frequency space and a single line in spatial-frequency space, so as to collect the data using a magnetic resonance imaging technique selected from the group consisting of radial sampling or projection-reconstruction sampling.

22. The method of claim 21, wherein the single point in spatial-frequency space is .[.about.]. .Iadd.substantially .Iaddend.zero spatial frequency.

23. The method of claim 21, wherein the single line in spatial-frequency space includes zero spatial frequency.

24. The method of claim 1, wherein the spatial-encoding magnetic-field gradient pulses applied during each said data-acquisition step are configured so as to collect data, following each of at least one of the refocusing radio-frequency pulses, along a spiral trajectory in spatial-frequency space, each trajectory of which is contained in one of two dimensions and three dimensions, and each trajectory of which passes through one of a single point in spatial-frequency space and a single line in spatial-frequency space.

25. The method of claim 24, wherein the single point in spatial-frequency space is .[.about.]. .Iadd.substantially .Iaddend.zero spatial frequency.

26. The method of claim 24, wherein the single line in spatial-frequency space includes zero spatial frequency.

27. The method of claim 1, wherein the spatial-encoding magnetic-field gradient pulses applied during at least one of said data-acquisition steps are configured to collect sufficient spatial-frequency data to reconstruct at least two image sets, each of which exhibits contrast properties different from the other image sets.

28. The method of claim 27, wherein at least some of the spatial-frequency data collected during at least one of said data-acquisition steps is used in the reconstruction of more than one image set, whereby the data is shared between image sets.

29. The method of claim 1, wherein the spatial-encoding magnetic-field gradient pulses applied during at least one of said data-acquisition steps are configured so that, for the echo following at least one of the refocusing radio-frequency pulses, at least one of the first moment, the second moment and the third moment corresponding to at least one of the spatial-encoding directions is approximately zero.

30. The method of claim 1, wherein the spatial-encoding magnetic-field gradient pulses applied during at least one of said data-acquisition steps are configured so that, following at least one of the refocusing radio-frequency pulses, the zeroth moment measured over the time period between said refocusing radio-frequency pulse and the immediately consecutive refocusing radio-frequency pulse is approximately zero for at least one of the spatial-encoding directions.

31. The method of claim 1, wherein during all said data-acquisition steps the duration of all data-sampling periods are equal.

32. The method of claim 1, wherein during at least one of said data-acquisition steps at least one of the data-sampling periods has a duration that differs from the duration of at least one other data-sampling period.

33. The method of claim 1, wherein the spatial-encoding magnetic-field gradient pulses applied during said data-acquisition steps are configured so that the extent of spatial-frequency space sampled along at least one of the spatial-encoding directions is not symmetric with respect to zero spatial frequency, whereby a larger extent of spatial-frequency space is sampled to one side of zero spatial frequency as compared to the opposite side of zero spatial frequency.

34. The method of claim 33 wherein said spatial-frequency data is reconstructed using a partial-Fourier reconstruction algorithm.

35. The method of claim 1, wherein during at least one of said data-acquisition steps the temporal order in which spatial-frequency space data is collected for at least one of the spatial-encoding directions is based on achieving at least one of selected contrast properties in the image and selected properties of the corresponding point spread function.

36. The method of claim 1, wherein during at least one of said data-acquisition steps the temporal order in which spatial-frequency space data is collected is different from that for at least one other data-acquisition step.

37. The method of claim 1, wherein during at least one of said data-acquisition steps the extent of spatial-frequency space data that is collected is different from that for at least one other data-acquisition step.

38. The method of claim 1, wherein during at least one of said data-acquisition steps spatial encoding of the radio-frequency magnetic resonance signal that follows at least one of the refocusing radio-frequency pulse is performed using only phase encoding so that said signal is received by the radio-frequency transceiver in the absence of any applied magnetic-field gradient pulses and hence contains chemical-shift information.

39. The method of claim 1, wherein at least one navigator radio-frequency pulse is incorporated into the pulse sequence for the purpose of determining the displacement of a portion of the object.

40. A magnetic resonance imaging apparatus generating a spin echo pulse sequence .[.in order.]. .Iadd.configured .Iaddend.to operate the apparatus .[.in.]..Iadd.that is configured for .Iaddend.imaging an object .[.that permits at least one of lengthening usable echo-train duration, reducing power deposition and incorporating desired image contrast into the tissue signal evolutions.]., the apparatus comprising: a main magnet system generating a steady magnetic field; a gradient magnet system generating temporary gradient magnetic fields; a radio-frequency transmitter system generating radio-frequency pulses; a radio-frequency receiver system receiving magnetic resonance signals; a reconstruction unit reconstructing an image of the object from the received magnetic resonance signals; and a control unit generating signals controlling the gradient magnet system, the radio-frequency transmitter system, the radio-frequency receiver system, and the reconstruction unit, wherein the control unit generates signals causing: a) providing contrast-preparation, said contrast-preparation comprising generating at least one of at least one radio-frequency pulse, at least one magnetic-field gradient pulse, and at least one time delay, whereby said contrast preparation encodes the magnetization with at least one desired image contrast; b) calculating flip angles and phases of refocusing radio-frequency pulses that are applied in a data-acquisition step, wherein said calculation provides desired prescribed signal evolution and desired overall signal level .Iadd.that permit, during said data-acquisition step, at least one of lengthening usable echo-train duration, reducing power deposition and incorporating desired image contrast into the tissue signal evolutions.Iaddend., said calculation comprises: i) selecting values of T1 and T2 relaxation times and selecting proton density; ii) selecting a prescribed time course of the amplitudes and phases of the radio-frequency magnetic resonance signals that are generated by said refocusing radio-frequency pulses; and iii) selecting characteristics of said contrast-preparation step, said data-acquisition step and a magnetization-recovery step, with the exception of the flip angles and phases of the refocusing radio-frequency pulses that are to be calculated; and c) providing said-data acquisition step based on a spin echo train acquisition, said data-acquisition step comprises: i) an excitation radio-frequency pulse having a flip angle and phase, ii) at least two refocusing radio-frequency pulses, each having a flip angle and phase as determined by said calculation step, and iii) magnetic-field gradient pulses that encode spatial information into at least one of said radio-frequency magnetic resonance signals that follow at least one of said refocusing radio-frequency pulses; d) providing magnetization-recovery, said magnetization-recovery comprises a time delay to allow magnetization to relax; and e) repeating steps (a) through (d) until a predetermined extent of spatial frequency space has been sampled.

41. A magnetic resonance imaging apparatus generating a spin echo pulse sequence .[.in order.]. .Iadd.configured .Iaddend.to operate the apparatus .[.in.]. .Iadd.that is configured for .Iaddend.imaging an object .[.that permits at least one of lengthening usable echo-train duration, reducing power deposition and incorporating desired image contrast into the tissue signal evolutions.]., the apparatus comprising: main magnet means generating a steady magnetic field; gradient magnet means generating temporary gradient magnetic fields; radio-frequency transmitter means generating radio-frequency pulses; radio-frequency receiver means receiving magnetic resonance signals;.[...]. reconstruction means reconstructing an image of the object from the received magnetic resonance signals; and control means generating signals controlling the gradient magnet means, the radio-frequency transmitter means, the radio-frequency receiver means, and the reconstruction means, wherein the control means generates signals causing: a) providing contrast-preparation, said contrast-preparation comprising generating at least one of at least one radio-frequency pulse, at least one magnetic-field gradient pulse, and at least one time delay, whereby said contrast preparation encodes the magnetization with at least one desired image contrast; b) calculating flip angles and phases of refocusing radio-frequency pulses that are applied in a data-acquisition step, wherein said calculation provides desired prescribed signal evolution and desired overall signal level .Iadd.that permit, during said data-acquisition step, at least one of lengthening usable echo-train duration, reducing power deposition and incorporating desired image contrast into the tissue signal evolutions.Iaddend., said calculation comprises: i) selecting values of T1 and T2 relaxation times and selecting proton density; ii) selecting a prescribed time course of the amplitudes and phases of the radio-frequency magnetic resonance signals that are generated by said refocusing radio-frequency pulses; and iii) selecting characteristics of said contrast-preparation step, said data-acquisition step and a magnetization-recovery step, with the exception of the flip angles and phases of the refocusing radio-frequency pulses that are to be calculated; c) providing said-data acquisition step based on a spin echo train acquisition, said data-acquisition step comprises: i) an excitation radio-frequency pulse having a flip angle and phase, ii) at least two refocusing radio-frequency pulses, each having a flip angle and phase as determined by said calculation step, and iii) magnetic-field gradient pulses that encode spatial information into at least one of said radio-frequency magnetic resonance signals that follow at least one of said refocusing radio-frequency pulses; d) providing magnetization-recovery, said magnetization-recovery comprises a time delay to allow magnetization to relax; and e) repeating steps (a) through (d) until a predetermined extent of spatial frequency space has been sampled.

42. A .Iadd.non-transitory .Iaddend.computer readable media carrying encoded program instructions for causing a programmable magnetic resonance imaging apparatus to perform the method of claim 1.

43. A .[.computer program provided on a.]. .Iadd.non-transitory .Iaddend.computer .[.useable.]. readable medium having computer program logic enabling at least one processor in a magnetic resonance imaging apparatus to generate a spin echo pulse sequence .[.that permits at least one of lengthening usable echo-train duration, reducing power deposition and incorporating desired image contrast into the tissue signal evolutions.]., said computer program logic comprising: a) providing contrast-preparation, said contrast-preparation comprising generating at least one of at least one radio-frequency pulse, at least one magnetic-field gradient pulse, and at least one time delay, whereby said contrast preparation encodes the magnetization with at least one desired image contrast; b) calculating flip angles and phases of refocusing radio-frequency pulses that are applied in a data-acquisition step, wherein said calculation provides desired prescribed signal evolution and desired overall signal level .Iadd.that permit, during said data-acquistion step, at least one of lengthening usable echo-train duration, reducing power deposition and incorporating desired image contrast into the tissue signal evolutions.Iaddend., said calculation comprises: i) selecting values of T1 and T2 relaxation times and selecting proton density; ii) selecting a prescribed time course of the amplitudes and phases of the radio-frequency magnetic resonance signals that are generated by said refocusing radio-frequency pulses; and iii) selecting characteristics of said contrast-preparation step, said data-acquisition step and a magnetization-recovery step, with the exception of the flip angles and phases of the refocusing radio-frequency pulses that are to be calculated; and c) providing said-data acquisition step based on a spin echo train acquisition, said data-acquisition step comprises: i) an excitation radio-frequency pulse having a flip angle and phase; ii) at least two refocusing radio-frequency pulses, each having a flip angle and phase as determined by said calculation step; and iii) magnetic-field gradient pulses that encode spatial information into at least one of said radio-frequency magnetic resonance signals that follow at least one of said refocusing radio-frequency pulses; d) providing magnetization-recovery, said magnetization-recovery comprises a time delay to allow magnetization to relax; and e) repeating steps (a) through (d) until a predetermined extent of spatial frequency space has been sampled.

.[.44. The method of claim 40, wherein at least one of said contrast-preparation and magnetization-recovery steps is omitted..].

.[.45. The method of claim 41, wherein at least one of said contrast-preparation and magnetization-recovery steps is omitted..].

.[.46. The method of claim 43, wherein at least one of said contrast-preparation and magnetization-recovery steps is omitted..].

.Iadd.47. The method of claim 1, wherein said calculation of the flip angles and phases occurs once prior to execution of the pulse sequence. .Iaddend.

.Iadd.48. The method of claim 1, wherein said calculation of the flip angles and phases occurs substantially simultaneous with the execution of the pulse sequence. .Iaddend.

.Iadd.49. The method of claim 1, wherein at least two of the calculation sub-steps are performed substantially simultaneously. .Iaddend.

.Iadd.50. The method of claim 1, wherein the performance of at least one of the calculation sub-steps (b) i through (b) iii in step (b) implicitly performs at least one of the other said calculation sub-steps. .Iaddend.

.Iadd.51. A method for generating a spin echo pulse sequence for operating a magnetic resonance imaging apparatus for imaging an object, said method comprising: a) calculating flip angles and phases of refocusing radio-frequency pulses that are applied in a data-acquisition step, wherein said calculation provides desired prescribed signal evolution and desired overall signal level that permit, during said data-acquisition step, at least one of lengthening usable echo-train duration, reducing power deposition and incorporating desired image contrast into the tissue signal evolutions, said calculation comprises: i) selecting values of T1 and T2 relaxation times and selecting proton density; ii) selecting a prescribed time course of the amplitudes and phases of the radio-frequency magnetic resonance signals that are generated by said refocusing radio-frequency pulses; and iii) selecting characteristics of said data-acquisition step and a magnetization-recovery step, with the exception of the flip angles and phases of the refocusing radio-frequency pulses that are to be calculated; and b) providing said data-acquisition step based on a spin echo train acquisition, said data-acquisition step comprises: i) an excitation radio-frequency pulse having a flip angle and phase; ii) at least two refocusing radio-frequency pulses, each having a flip angle and phase as determined by said calculation step; and iii) magnetic-field gradient pulses that encode spatial information into at least one of said radio-frequency magnetic resonance signals that follow at least one of said refocusing radio-frequency pulses; c) providing magnetization-recovery, said magnetization-recovery comprises a time delay to allow magnetization to relax; and d) repeating at least one of steps (a) through (c) until a predetermined extent of spatial frequency space has been sampled. .Iaddend.

.Iadd.52. The method of claim 51, wherein said calculation of the flip angles and phases occurs either prior to or substantially simultaneous with execution of the pulse sequence, and wherein the performance of at least one of the calculation sub-steps (a) i through (a) iii in step (a) implicitly performs at least one of the other said calculation sub-steps. .Iaddend.

.Iadd.53. A method for generating a spin echo pulse sequence for operating a magnetic resonance imaging apparatus for imaging an object, said method comprising: a) providing contrast-preparation, said contrast-preparation comprising generating at least one of at least one radio-frequency pulse, at least one magnetic-field gradient pulse, and at least one time delay, whereby said contrast preparation encodes the magnetization with at least one desired image contrast; b) calculating flip angles and phases of refocusing radio-frequency pulses that are applied in a data-acquisition step, wherein said calculation provides desired prescribed signal evolution and desired overall signal level that permit, during said data-acquisition step, at least one of lengthening usable echo-train duration, reducing power deposition and incorporating desired image contrast into the tissue signal evolutions, said calculation comprises: i) selecting values of T1 and T2 relaxation times and selecting proton density; ii) selecting a prescribed time course of the amplitudes and phases of the radio-frequency magnetic resonance signals that are generated by said refocusing radio-frequency pulses; and iii) selecting characteristics of said contrast-preparation step and said data-acquisition step, with the exception of the flip angles and phases of the refocusing radio-frequency pulses that are to be calculated; c) providing said data-acquisition step based on a spin echo train acquisition, said data-acquisition step comprises: i) an excitation radio-frequency pulse having a flip angle and phase; ii) at least two refocusing radio-frequency pulses, each having a flip angle and phase as determined by said calculation step; and iii) magnetic-field gradient pulses that encode spatial information into at least one of said radio-frequency magnetic resonance signals that follow at least one of said refocusing radio-frequency pulses; and d) repeating at least one of steps (a) through (c) until a predetermined extent of spatial frequency space has been sampled. .Iaddend.

.Iadd.54. The apparatus of claim 40, wherein said calculation of the flip angles and phases occurs once prior to execution of the pulse sequence. .Iaddend.

.Iadd.55. The apparatus of claim 40, wherein said calculation of the flip angles and phases occurs substantially simultaneous with the execution of the pulse sequence. .Iaddend.

.Iadd.56. The apparatus of claim 40, wherein at least two of the calculation sub-steps are performed substantially simultaneously. .Iaddend.

.Iadd.57. The apparatus of claim 40, wherein the performance of at least one of the calculation sub-steps (b) i through (b) iii in step (b) implicitly performs at least one of the other said calculation sub-steps. .Iaddend.

.Iadd.58. A magnetic resonance imaging apparatus generating a spin echo pulse sequence configured to operate the apparatus that is configured for imaging an object, the apparatus comprising: a main magnet system generating a steady magnetic field; a gradient magnet system generating temporary gradient magnetic fields; a radio-frequency transmitter system generating radio-frequency pulses; a radio-frequency receiver system receiving magnetic resonance signals; a reconstruction unit reconstructing an image of the object from the received magnetic resonance signals; and a control unit generating signals controlling the gradient magnet system, the radio-frequency transmitter system, the radio-frequency receiver system, and the reconstruction unit, wherein the control unit generates signals causing: a) calculating flip angles and phases of refocusing radio-frequency pulses that are applied in a data-acquisition step, wherein said calculation provides desired prescribed signal evolution and desired overall signal level that permit, during said data-acquisition step, at least one of lengthening usable echo-train duration, reducing power deposition and incorporating desired image contrast into the tissue signal evolutions, said calculation comprises: i) selecting values of T1 and T2 relaxation times and selecting proton density; ii) selecting a prescribed time course of the amplitudes and phases of the radio-frequency magnetic resonance signals that are generated by said refocusing radio-frequency pulses; and iii) selecting characteristics of said data-acquisition step and a magnetization-recovery step, with the exception of the flip angles and phases of the refocusing radio-frequency pulses that are to be calculated; b) providing said data-acquisition step based on a spin echo train acquisition, said data-acquisition step comprises: i) an excitation radio-frequency pulse having a flip angle and phase, ii) at least two refocusing radio-frequency pulses, each having a flip angle and phase as determined by said calculation step, and iii) magnetic-field gradient pulses that encode spatial information into at least one of said radio-frequency magnetic resonance signals that follow at least one of said refocusing radio-frequency pulses; c) providing magnetization-recovery, said magnetization-recovery comprises a time delay to allow magnetization to relax; and d) repeating at least one of steps (a) through (c) until a predetermined extent of spatial frequency space has been sampled. .Iaddend.

.Iadd.59. The method of claim 58, wherein said calculation of the flip angles and phases occurs either prior to or substantially simultaneous with execution of the pulse sequence, and wherein the performance of at least one of the calculation sub-steps (a) i through (a) iii in step (a) implicitly performs at least one of the other said calculation sub-steps. .Iaddend.

.Iadd.60. A magnetic resonance imaging apparatus generating a spin echo pulse sequence configured to operate the apparatus that is configured for imaging an object, the apparatus comprising: a main magnet system generating a steady magnetic field; a gradient magnet system generating temporary gradient magnetic fields; a radio-frequency transmitter system generating radio-frequency pulses; a radio-frequency receiver system receiving magnetic resonance signals; a reconstruction unit reconstructing an image of the object from the received magnetic resonance signals; and a control unit generating signals controlling the gradient magnet system, the radio-frequency transmitter system, the radio-frequency receiver system, and the reconstruction unit, wherein the control unit generates signals causing: a) providing contrast-preparation, said contrast-preparation comprising generating at least one of at least one radio-frequency pulse, at least one magnetic-field gradient pulse, and at least one time delay, whereby said contrast preparation encodes the magnetization with at least one desired image contrast; b) calculating flip angles and phases of refocusing radio-frequency pulses that are applied in a data-acquisition step, wherein said calculation provides desired prescribed signal evolution and desired overall signal level that permit, during said data-acquisition step, at least one of lengthening usable echo-train duration, reducing power deposition and incorporating desired image contrast into the tissue signal evolutions, said calculation comprises: i) selecting values of T1 and T2 relaxation times and selecting proton density; ii) selecting a prescribed time course of the amplitudes and phases of the radio-frequency magnetic resonance signals that are generated by said refocusing radio-frequency pulses; and iii) selecting characteristics of said contrast-preparation step and said data-acquisition step, with the exception of the flip angles and phases of the refocusing radio-frequency pulses that are to be calculated; c) providing said data-acquisition step based on a spin echo train acquisition, said data-acquisition step comprises: i) an excitation radio-frequency pulse having a flip angle and phase, ii) at least two refocusing radio-frequency pulses, each having a flip angle and phase as determined by said calculation step, and iii) magnetic-field gradient pulses that encode spatial information into at least one of said radio-frequency magnetic resonance signals that follow at least one of said refocusing radio-frequency pulses; and d) repeating at least one of steps (a) through (c) until a predetermined extent of spatial frequency space has been sampled. .Iaddend.

.Iadd.61. The apparatus of claim 41, wherein said calculation of the flip angles and phases occurs once prior to execution of the pulse sequence. .Iaddend.

.Iadd.62. The apparatus of claim 41, wherein said calculation of the flip angles and phases occurs substantially simultaneous with the execution of the pulse sequence. .Iaddend.

.Iadd.63. The apparatus of claim 41, wherein at least two of the calculation sub-steps are performed substantially simultaneously. .Iaddend.

.Iadd.64. The apparatus of claim 41, wherein the performance of at least one of the calculation sub-steps (b) i through (b) iii in step (b) implicitly performs at least one of the other said calculation sub-steps. .Iaddend.

.Iadd.65. A magnetic resonance imaging apparatus generating a spin echo pulse sequence configured to operate the apparatus that is configured for imaging an object, the apparatus comprising: main magnet means generating a steady magnetic field; gradient magnet means generating temporary gradient magnetic fields; radio-frequency transmitter means generating radio-frequency pulses; radio-frequency receiver means receiving magnetic resonance signals; reconstruction means reconstructing an image of the object from the received magnetic resonance signals; and control means generating signals controlling the gradient magnet means, the radio-frequency transmitter means, the radio-frequency receiver means, and the reconstruction means, wherein the control means generates signals causing: a) calculating flip angles and phases of refocusing radio-frequency pulses that are applied in a data-acquisition step, wherein said calculation provides desired prescribed signal evolution and desired overall signal level that permit, during said data-acquisition step, at least one of lengthening usable echo-train duration, reducing power deposition and incorporating desired image contrast into the tissue signal evolutions, said calculation comprises: i) selecting values of T1 and T2 relaxation times and selecting proton density; ii) selecting a prescribed time course of the amplitudes and phases of the radio-frequency magnetic resonance signals that are generated by said refocusing radio-frequency pulses; and iii) selecting characteristics of said data-acquisition step and a magnetization-recovery step, with the exception of the flip angles and phases of the refocusing radio-frequency pulses that are to be calculated; b) providing said data-acquisition step based on a spin echo train acquisition, said data-acquisition step comprises: i) an excitation radio-frequency pulse having a flip angle and phase, ii) at least two refocusing radio-frequency pulses, each having a flip angle and phase as determined by said calculation step, and iii) magnetic-field gradient pulses that encode spatial information into at least one of said radio-frequency magnetic resonance signals that follow at least one of said refocusing radio-frequency pulses; c) providing magnetization-recovery, said magnetization-recovery comprises a time delay to allow magnetization to relax; and d) repeating at least one of steps (a) through (c) until a predetermined extent of spatial frequency space has been sampled. .Iaddend.

.Iadd.66. The apparatus of claim 65, wherein said calculation of the flip angles and phases occurs either prior to or substantially simultaneous with execution of the pulse sequence, and wherein the performance of at least one of the calculation sub-steps (a) i through (a) iii in step (a) implicitly performs at least one of the other said calculation sub-steps. .Iaddend.

.Iadd.67. A magnetic resonance imaging apparatus generating a spin echo pulse sequence configured to operate the apparatus that is configured for imaging an object, the apparatus comprising: main magnet means generating a steady magnetic field; gradient magnet means generating temporary gradient magnetic fields; radio-frequency transmitter means generating radio-frequency pulses; radio-frequency receiver means receiving magnetic resonance signals; reconstruction means reconstructing an image of the object from the received magnetic resonance signals; and control means generating signals controlling the gradient magnet means, the radio-frequency transmitter means, the radio-frequency receiver means, and the reconstruction means, wherein the control means generates signals causing: a) providing contrast-preparation, said contrast-preparation comprising generating at least one of at least one radio-frequency pulse, at least one magnetic-field gradient pulse, and at least one time delay, whereby said contrast preparation encodes the magnetization with at least one desired image contrast; b) calculating flip angles and phases of refocusing radio-frequency pulses that are applied in a data-acquisition step, wherein said calculation provides desired prescribed signal evolution and desired overall signal level that permit, during said data acquisition step, at least one of lengthening usable echo-train duration, reducing power deposition and incorporating desired image contrast into the tissue signal evolutions, said calculation comprises: i) selecting values of T1 and T2 relaxation times and selecting proton density; ii) selecting a prescribed time course of the amplitudes and phases of the radio-frequency magnetic resonance signals that are generated by said refocusing radio-frequency pulses; and iii) selecting characteristics of said contrast-preparation step and said data-acquisition step, with the exception of the flip angles and phases of the refocusing radio-frequency pulses that are to be calculated; c) providing said data-acquisition step based on a spin echo train acquisition, said data-acquisition step comprises: i) an excitation radio-frequency pulse having a flip angle and phase, ii) at least two refocusing radio-frequency pulses, each having a flip angle and phase as determined by said calculation step, and iii) magnetic-field gradient pulses that encode spatial information into at least one of said radio-frequency magnetic resonance signals that follow at least one of said refocusing radio-frequency pulses; and d) repeating at least one of steps (a) through (c) until a predetermined extent of spatial frequency space has been sampled. .Iaddend.

.Iadd.68. The non-transitory computer readable medium of claim 43, wherein said calculation of the flip angles and phases occurs once prior to execution of the pulse sequence. .Iaddend.

.Iadd.69. The non-transitory computer readable medium of claim 43, wherein said calculation of the flip angles and phases occurs substantially simultaneous with the execution of the pulse sequence. .Iaddend.

.Iadd.70. The non-transitory computer readable medium of claim 43, wherein at least two of the calculation sub-steps are performed substantially simultaneously. .Iaddend.

.Iadd.71. The non-transitory computer readable medium of claim 43, wherein the performance of at least one of the calculation sub-steps (b) i through (b) iii in step (b) implicitly performs at least one of the other said calculation sub-steps. .Iaddend.

.Iadd.72. A non-transitory computer readable medium having computer program logic enabling at least one processor in a magnetic resonance imaging apparatus to generate a spin echo pulse sequence, said computer program logic comprising: a) calculating flip angles and phases of refocusing radio-frequency pulses that are applied in a data-acquisition step, wherein said calculation provides desired prescribed signal evolution and desired overall signal level that permit, during said data-acquisition step, at least one of lengthening usable echo-train duration, reducing power deposition and incorporating desired image contrast into the tissue signal evolutions, said calculation comprises: i) selecting values of T1 and T2 relaxation times and selecting proton density; ii) selecting a prescribed time course of the amplitudes and phases of the radio-frequency magnetic resonance signals that are generated by said refocusing radio-frequency pulses; and iii) selecting characteristics of said data-acquisition step and a magnetization-recovery step, with the exception of the flip angles and phases of the refocusing radio-frequency pulses that are to be calculated; b) providing said data-acquisition step based on a spin echo train acquisition, said data-acquisition step comprises: i) an excitation radio-frequency pulse having a flip angle and phase; ii) at least two refocusing radio-frequency pulses, each having a flip angle and phase as determined by said calculation step; and iii) magnetic-field gradient pulses that encode spatial information into at least one of said radio-frequency magnetic resonance signals that follow at least one of said refocusing radio-frequency pulses; c) providing magnetization-recovery, said magnetization-recovery comprises a time delay to allow magnetization to relax; and d) repeating at least one of steps (a) through (c) until a predetermined extent of spatial frequency space has been sampled. .Iaddend.

.Iadd.73. The non-transitory computer readable medium of claim 72, wherein said calculation of the flip angles and phases occurs either prior to or substantially simultaneous with execution of the pulse sequence, and wherein the performance of at least one of the calculation sub-steps (a) i through (a) iii in step (a) implicitly performs at least one of the other said calculation sub-steps. .Iaddend.

.Iadd.74. A non-transitory computer readable medium having computer program logic enabling at least one processor in a magnetic resonance imaging apparatus to generate a spin echo pulse sequence, said computer program logic comprising: a) providing contrast-preparation, said contrast-preparation comprising generating at least one of at least one radio-frequency pulse, at least one magnetic-field gradient pulse, and at least one time delay, whereby said contrast preparation encodes the magnetization with at least one desired image contrast; b) calculating flip angles and phases of refocusing radio-frequency pulses that are applied in a data-acquisition step, wherein said calculation provides desired prescribed signal evolution and desired overall signal level that permit, during said data-acquisition step, at least one of lengthening usable echo-train duration, reducing power deposition and incorporating desired image contrast into the tissue signal evolutions, said calculation comprises: i) selecting values of T1 and T2 relaxation times and selecting proton density; ii) selecting a prescribed time course of the amplitudes and phases of the radio-frequency magnetic resonance signals that are generated by said refocusing radio-frequency pulses; and iii) selecting characteristics of said contrast-preparation step and said data-acquisition step, with the exception of the flip angles and phases of the refocusing radio-frequency pulses that are to be calculated; c) providing said data-acquisition step based on a spin echo train acquisition, said data-acquisition step comprises: i) an excitation radio-frequency pulse having a flip angle and phase; ii) at least two refocusing radio-frequency pulses, each having a flip angle and phase as determined by said calculation step; and iii) magnetic-field gradient pulses that encode spatial information into at least one of said radio-frequency magnetic resonance signals that follow at least one of said refocusing radio-frequency pulses; and d) repeating at least one of steps (a) through (c) until a predetermined extent of spatial frequency space has been sampled. .Iaddend.

.Iadd.75. A method for generating a spin-echo pulse sequence for operating a magnetic resonance imaging apparatus for imaging an object, said method comprising: providing a data-acquisition step based on a spin-echo-train pulse sequence, said data-acquisition step comprises: providing an excitation radio-frequency pulse having a flip angle and phase angle; providing at least two refocusing radio-frequency pulses, each having a flip angle and phase angle, wherein, to permit during said data-acquisition step at least one of lengthening usable echo-train duration, reducing power deposition and incorporating desired image contrast into the signal evolutions, at least one of said angles is selected to vary among pulses to yield a signal evolution for the associated train of spin echoes for at least one first substance of interest in said object, with corresponding T1 and T2 relaxation times and spin density of interest, and to yield a signal evolution for the associated train of spin echoes for at least one second substance of interest in said object, with corresponding T1 and T2 relaxation times and spin density of interest, wherein said signal evolutions result in T2-weighted contrast in the corresponding image(s) that is substantially the same as T2-weighted contrast that would be provided by imaging said object by using a turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence that has constant flip angles, with values of 180 degrees, for the refocusing radio-frequency pulses, and wherein at least one of the duration of the spin-echo trains for said signal evolutions for said substances is at least twice the duration of the spin-echo train for said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence and an effective echo time corresponding to said spin-echo trains for said signal evolutions for said substances is at least twice an effective echo time for said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence; providing magnetic-field gradient pulses that perform at least one of encoding spatial information into at least one of the radio-frequency magnetic resonance signals that follow at least one of said refocusing radio-frequency pulses and dephasing transverse magnetization associated with undesired signal pathways to reduce or eliminate contribution of said transverse magnetization to sampled signals; and providing data sampling, associated with magnetic-field gradient pulses that perform spatial encoding; and repeating said data-acquisition step until a predetermined extent of spatial frequency space has been sampled. .Iaddend.

.Iadd.76. The method of claim 75, wherein at least one of a time delay and at least one magnetic-field gradient pulse occurs between the end of at least one spin-echo train and the excitation radio-frequency pulse associated with the next spin-echo train. .Iaddend.

.Iadd.77. The method of claim 75, wherein at least one repetition of said data-acquisition step is for the purpose of stabilizing the response of at least one of magnetization related system and apparatus related hardware system. .Iaddend.

.Iadd.78. The method of 75, wherein for at least one repetition of said data-acquisition step at least one of at least a fraction of the sampled data is discarded and no data is sampled. .Iaddend.

.Iadd.79. The method of claim 75, wherein said flip angles and phase angles for the refocusing radio-frequency pulses are calculated using an appropriate analytical or computer-based algorithm, either prior to or substantially simultaneous with the execution of the pulse sequence. .Iaddend.

.Iadd.80. The method of claim 75, wherein said flip angles for said refocusing radio-frequency pulses decrease, within the first approximately 15% of the total number of echoes, to a value that is no more than approximately one-third of the initial flip angle for said refocusing radio-frequency pulses, and said flip angles then increase for the remaining echoes in said train of spin echoes. .Iaddend.

.Iadd.81. The method of claim 80, wherein said flip angles for said refocusing radio-frequency pulses reach, at 50% of the total number of echoes in said train of spin echoes, a value approximately midway between said initial flip angle and the lowest flip angle. .Iaddend.

.Iadd.82. The method of claim 75, wherein said flip angles and phase angles for said refocusing radio-frequency pulses are, in addition, selected to reduce power deposition compared to power deposition that would be achieved by using constant flip angles, with values of 180 degrees, for the refocusing radio-frequency pulses. .Iaddend.

.Iadd.83. The method of claim 82, wherein the power deposition at a magnetic field strength of 3 Tesla for the method of claim 75 is below regulatory limits while power deposition that would be achieved by using constant flip angles, with values of 180 degrees, for the refocusing radio-frequency pulses exceeds regulatory limits. .Iaddend.

.Iadd.84. The method of claim 75, wherein said effective echo time corresponding to said spin-echo trains for said signal evolutions for said substances is at least twice said effective echo time for said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence and said duration of the spin-echo trains for said signal evolutions for said substances is at least twice said duration of the spin-echo train for said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence. .Iaddend.

.Iadd.85. The method of claim 75, wherein at least one of said effective echo time corresponding to said spin-echo trains for said signal evolutions for said substances is at least on the order of 300 milliseconds and said duration of the spin-echo trains for said signal evolutions for said substances is at least on the order of 600 milliseconds. .Iaddend.

.Iadd.86. The method of claim 75, wherein said effective echo time corresponding to said spin-echo trains for said signal evolutions for said substances is at least on the order of 300 milliseconds and said duration of the spin-echo trains for said signal evolutions for said substances is at least on the order of 600 milliseconds. .Iaddend.

.Iadd.87. The method of claim 75, wherein said effective echo time for said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence has a value typical for T2-weighted clinical magnetic resonance imaging. .Iaddend.

.Iadd.88. The method of claim 75, wherein said duration of the spin-echo trains for said signal evolutions for said substances is greater than approximately four times the T2 relaxation time for at least one of said substances. .Iaddend.

.Iadd.89. The method of claim 75, wherein said effective echo time corresponding to said spin-echo trains for said signal evolutions for said substances is greater than approximately two times the T2 relaxation time for at least one of said substances. .Iaddend.

.Iadd.90. The method of claim 75, wherein said first and second substances of interest are brain white matter and brain gray matter. .Iaddend.

.Iadd.91. The method of claim 90, wherein at least one of said duration of the spin-echo train for said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence is less than 300 milliseconds and said effective echo time for said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence has a value typical for T2-weighted clinical magnetic resonance imaging of the brain. .Iaddend.

.Iadd.92. The method of claim 75, wherein said first and second substances of interest are spinal cord white matter and spinal cord gray matter. .Iaddend.

.Iadd.93. The method of claim 75, wherein at least one of said substances of interest is at least one of cartilage, ligament and muscle. .Iaddend.

.Iadd.94. The method of claim 90, wherein said duration of the spin-echo train for said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence is less than 300 milliseconds and said effective echo time for said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence has a value typical for T2-weighted clinical magnetic resonance imaging of the brain. .Iaddend.

.Iadd.95. The method of claim 75, wherein the number of refocusing radio-frequency pulses following at least one said excitation radio-frequency pulse is greater than 50. .Iaddend.

.Iadd.96. The method of claim 75, wherein the number of refocusing radio-frequency pulses following at least one said excitation radio-frequency pulse is greater than 100. .Iaddend.

.Iadd.97. The method of claim 75, wherein a contrast preparation comprising generating at least one of at least one radio-frequency pulse, at least one magnetic-field gradient pulse, and at least one time delay, whereby said contrast preparation encodes the magnetization with at least one desired image contrast, immediately precedes at least one of said excitation radio-frequency pulses. .Iaddend.

.Iadd.98. The method of claim 97, wherein said contrast preparation comprises at least an inversion radio-frequency pulse followed by a time delay. .Iaddend.

.Iadd.99. The method of claim 98, wherein said time delay is chosen so that the longitudinal magnetization associated with fluid, such as cerebrospinal fluid, is passing through substantially zero when at least one said excitation radio-frequency pulse is applied. .Iaddend.

.Iadd.100. The method of claim 97, wherein at least one of the radio-frequency pulses is at least one of spatially selective in one of one, two and three dimensions, chemically selective, and adiabatic. .Iaddend.

.Iadd.101. The method of claim 97, wherein at least one said contrast preparation is initiated by a trigger signal to synchronize the pulse sequence with at least one of at least one external temporal event and at least one internal temporal event. .Iaddend.

.Iadd.102. The method of claim 101, wherein said external and internal events comprise at least one of at least one voluntary action, at least one involuntary action, at least one respiratory cycle and at least one cardiac cycle. .Iaddend.

.Iadd.103. The method of claim 97, wherein at least one of at least one radio-frequency pulse and at least one magnetic-field gradient pulse is applied as part of at least one said contrast preparation for the purpose of stabilizing the response of at least one of magnetization related system and apparatus related hardware system. .Iaddend.

.Iadd.104. The method of claim 75, wherein the flip angle for at least one of the refocusing radio-frequency pulses in the first half of at least one spin-echo train is chosen to be sufficiently low to cause the signal from flowing or pulsating fluid in resulting images to be suppressed. .Iaddend.

.Iadd.105. The method of claim 104, wherein said flip angle is less than 30 degrees. .Iaddend.

.Iadd.106. The method of claim 75, wherein a two-dimensional plane of spatial-frequency space is sampled. .Iaddend.

.Iadd.107. The method of claim 75, wherein a three-dimensional volume of spatial-frequency space is sampled. .Iaddend.

.Iadd.108. The method of claim 75, wherein at least one said data-acquisition step is initiated by a trigger signal to synchronize the pulse sequence with at least one of at least one external temporal event and at least one internal temporal event. .Iaddend.

.Iadd.109. The method of claim 108, wherein said external and internal events comprise at least one of at least one voluntary action, at least one involuntary action, at least one respiratory cycle and at least one cardiac cycle. .Iaddend.

.Iadd.110. The method of claim 75, wherein at least one of at least one radio-frequency pulse and at least one magnetic-field gradient pulse is applied as part of at least one said data-acquisition step for the purpose of stabilizing the response of at least one of magnetization related system and apparatus related hardware system. .Iaddend.

.Iadd.111. The method of claim 75, wherein the time periods between consecutive refocusing radio-frequency pulses applied during said data-acquisition steps are all of equal duration. .Iaddend.

.Iadd.112. The method of claim 75, wherein the time periods between consecutive refocusing radio-frequency pulses applied during said data-acquisition steps vary in duration amongst pairs of refocusing radio-frequency pulses during at least one said data-acquisition step. .Iaddend.

.Iadd.113. The method of claim 75 wherein all radio-frequency pulses are at least one of non-spatially selective and non-chemically selective. .Iaddend.

.Iadd.114. The method of claim 75, wherein at least one of the radio-frequency pulses is at least one of spatially selective in one of one, two and three dimensions, chemically selective, and adiabatic. .Iaddend.

.Iadd.115. The method of claim 75, wherein during at least one said data-acquisition step, the phase difference between the phase angle for the excitation radio-frequency pulse and the phase angles for all refocusing radio-frequency pulses is substantially 90 degrees. .Iaddend.

.Iadd.116. The method of claim 75, wherein during at least one said data-acquisition step, the phase difference between the phase angle for any refocusing radio-frequency pulse and the phase angle for the immediately subsequent refocusing radio-frequency pulse is substantially 180 degrees, and the phase difference between the phase angle for the excitation radio-frequency pulse and the phase angle for the first refocusing pulse is one of substantially 0 degrees and substantially 180 degrees. .Iaddend.

.Iadd.117. The method of claim 75, wherein the flip angle for the excitation radio-frequency pulse is substantially one-half of the flip angle for the first refocusing radio-frequency pulse. .Iaddend.

.Iadd.118. The method of claim 75, wherein the spatial-encoding magnetic-field gradient pulses applied during each said data-acquisition step are configured so as to collect data, following each of at least one of the refocusing radio-frequency pulses, for one line in spatial-frequency space which is parallel to all other lines of data so collected, so as to collect the data using a magnetic resonance imaging technique selected from the group consisting of rapid acquisition with relaxation enhancement (RARE), fast spin echo (FSE), and turbo spin echo (TSE or TurboSE). .Iaddend.

.Iadd.119. The method of claim 75, wherein the spatial-encoding magnetic-field gradient pulses applied during each said data-acquisition step are configured so as to collect data, following each of at least one of the refocusing radio-frequency pulses, for two or more lines in spatial-frequency space which are parallel to all other lines of data so collected, so as to collect the data using a magnetic resonance imaging technique selected from the group consisting of gradient and spin echo (GRASE) and turbo gradient spin echo (TGSE or TurboGSE). .Iaddend.

.Iadd.120. The method of claim 75, wherein the spatial-encoding magnetic-field gradient pulses applied during each said data-acquisition step are configured so as to collect data, following each of at least one of the refocusing radio-frequency pulses, for one or more lines in spatial-frequency space, each of which pass through one of a single point in spatial-frequency space and a single line in spatial-frequency space, so as to collect the data using a magnetic resonance imaging technique selected from the group consisting of radial sampling and projection-reconstruction sampling. .Iaddend.

.Iadd.121. The method of claim 120, wherein the single point in spatial-frequency space is substantially zero spatial frequency. .Iaddend.

.Iadd.122. The method of claim 120, wherein the single line in spatial-frequency space includes substantially zero spatial frequency. .Iaddend.

.Iadd.123. The method of claim 75, wherein the spatial-encoding magnetic-field gradient pulses applied during each said data-acquisition step are configured so as to collect data, following each of at least one of the refocusing radio-frequency pulses, along a spiral trajectory in spatial-frequency space, each trajectory of which is contained in one of two dimensions and three dimensions, and each trajectory of which passes through one of a single point in spatial-frequency space and a single line in spatial-frequency space. .Iaddend.

.Iadd.124. The method of claim 123, wherein the single point in spatial-frequency space is substantially zero spatial frequency. .Iaddend.

.Iadd.125. The method of claim 123, wherein the single line in spatial-frequency space includes substantially zero spatial frequency. .Iaddend.

.Iadd.126. The method of 75, wherein the spatial-encoding magnetic-field gradient pulses applied during at least one of said data-acquisition steps are configured to collect sufficient spatial-frequency data to reconstruct at least two image sets, each of which exhibits contrast properties different from the other image sets. .Iaddend.

.Iadd.127. The method of claim 126, wherein at least some of the spatial-frequency data collected during at least one of said data-acquisition steps is used in the reconstruction of more than one image set, whereby the data is shared between image sets. .Iaddend.

.Iadd.128. The method of claim 75, wherein the spatial-encoding magnetic-field gradient pulses applied during at least one of said data-acquisition steps are configured so that, for the echo following at least one of the refocusing radio-frequency pulses, at least one of the first moment, the second moment and the third moment corresponding to at least one of the spatial-encoding directions is approximately zero. .Iaddend.

.Iadd.129. The method of claim 75, wherein the spatial-encoding magnetic-field gradient pulses applied during at least one of said data-acquisition steps are configured so that, following at least one of the refocusing radio-frequency pulses, the zeroth moment measured over the time period between said refocusing radio-frequency pulse and the immediately consecutive refocusing radio-frequency pulse is approximately zero for at least one of the spatial-encoding directions. .Iaddend.

.Iadd.130. The method of claim 75, wherein during all said data-acquisition steps the duration of all data-sampling periods are equal. .Iaddend.

.Iadd.131. The method of claim 75, wherein during at least one of said data-acquisition steps at least one of the data-sampling periods has a duration that differs from the duration of at least one other data-sampling period. .Iaddend.

.Iadd.132. The method of claim 75, wherein the spatial-encoding magnetic-field gradient pulses applied during said data-acquisition steps are configured so that the extent of spatial-frequency space sampled along at least one of the spatial-encoding directions is not symmetric with respect to zero spatial frequency, whereby a larger extent of spatial-frequency space is sampled to one side of zero spatial frequency as compared to the opposite side of zero spatial frequency. .Iaddend.

.Iadd.133. The method of claim 132 wherein said spatial-frequency data is reconstructed using a partial-Fourier reconstruction algorithm. .Iaddend.

.Iadd.134. The method of claim 75, wherein during at least one of said data-acquisition steps the temporal order in which spatial-frequency data is collected for at least one of the spatial-encoding directions is based on achieving at least one of selected contrast properties in the image and selected properties of the corresponding point spread function. .Iaddend.

.Iadd.135. The method of claim 75, wherein during at least one of said data-acquisition steps the temporal order in which spatial-frequency data is collected is different from that for at least one other data-acquisition step. .Iaddend.

.Iadd.136. The method of claim 75, wherein during at least one of said data-acquisition steps the extent of spatial-frequency data that is collected is different from that for at least one other data-acquisition step. .Iaddend.

.Iadd.137. The method of claim 75, wherein during at least one of said data-acquisition steps spatial encoding of the radio-frequency magnetic resonance signal that follows at least one of the refocusing radio-frequency pulses is performed using only phase encoding so that said signal is received by the radio-frequency transceiver in the absence of any applied magnetic-field gradient pulses and hence contains chemical-shift information. .Iaddend.

.Iadd.138. The method of claim 75, wherein at least one navigator radio-frequency pulse is incorporated into the pulse sequence for the purpose of determining the displacement of a portion of the object. .Iaddend.

.Iadd.139. The method of claim 75, wherein said flip angles and phase angles for said refocusing radio-frequency pulses are, in addition, selected to increase the number of echoes in at least one spin-echo train compared to the number which would be achieved by using said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence. .Iaddend.

.Iadd.140. A method for generating a spin-echo pulse sequence for operating a magnetic resonance imaging apparatus for imaging an object, said method comprising: calculating flip angles and phase angles of refocusing radio-frequency pulses that are applied in a data-acquisition step, wherein, to permit during said data-acquisition step at least one of lengthening usable echo-train duration, reducing power deposition and incorporating desired image contrast into the signal evolutions, said calculation provides flip angles and phase angles to yield a signal evolution for the associated train of spin echoes for at least one first substance of interest in said object, with corresponding T1 and T2 relaxation times and spin density of interest, and to yield a signal evolution for the associated train of spin echoes for at least one second substance of interest in said object, with corresponding T1 and T2 relaxation times and spin density of interest, wherein said signal evolutions result in T2-weigthed contrast in the corresponding image(s) that is substantially the same as T2-weighted contrast that would be provided by imaging said object by using a turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence that has constant flip angles, with values of 180 degrees, for the refocusing radio-frequency pulses, and wherein at least one of the duration of the spin-echo trains for said signal evolutions for said substances is at least twice the duration of the spin-echo train for said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence and an effective echo time corresponding to said spin-echo trains for said signal evolutions for said substances is at least twice an effective echo time for said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence; providing said data-acquisition step based on a spin-echo-train pulse sequence, said data-acquisition step comprises: providing an excitation radio-frequency pulse having a flip angle and phase angle; providing at least two refocusing radio-frequency pulses, each having a flip angle and phase angle as determined by said calculation step; providing magnetic-field gradient pulses that perform at least one of encoding spatial information into at least one of the radio-frequency magnetic resonance signals that follow at least one of said refocusing radio-frequency pulses and dephasing transverse magnetization associated with undesired signal pathways to reduce or eliminate contribution of said transverse magnetization to sampled signals; and providing data sampling, associated with magnetic-field gradient pulses that perform spatial encoding; and repeating at least one of said calculating flip angles and phase angles and said data-acquisition step until a predetermined extent of spatial frequency space has been sampled. .Iaddend.

.Iadd.141. A method for generating a spin-echo pulse sequence for operating a magnetic resonance imaging apparatus for imaging an object, said method comprising: providing a data-acquisition step based on a spin-echo-train pulse sequence, said data-acquisition step comprises: providing an excitation radio-frequency pulse having a flip angle and phase angle; providing at least two refocusing radio-frequency pulses, each having a flip angle and phase angle, wherein, to permit during said data-acquisition step at least one of lengthening usable echo-train duration, reducing power deposition and incorporating desired image contrast into the signal evolutions, said flip angles for said refocusing radio-frequency pulses are selected to vary among pulses to yield a signal evolution for the associated train of spin echoes for at least one substance of interest in said object, with corresponding T1 and T2 relaxation times and spin density of interest, and wherein said flip angles for said refocusing radio-frequency pulses decrease, within the first approximately 15% of the total number of echoes, to a value that is no more than approximately one-third of the initial flip angle for said refocusing radio-frequency pulses, and said flip angles then increase for the remaining echoes in said train of spin echoes; providing magnetic-field gradient pulses that perform at least one of encoding spatial information into at least one of the radio-frequency magnetic resonance signals that follow at least one of said refocusing radio-frequency pulses and dephasing transverse magnetization associated with undesired signal pathways to reduce or eliminate contribution of said transverse magnetization to sampled signals; and providing data sampling, associated with magnetic-field gradient pulses that perform spatial encoding; providing a magnetization-recovery step, said magnetization-recovery step comprises at least one of a time delay and at least one magnetic-field gradient pulse; and repeating at least one of said data-acquisition step and said magnetization-recovery step until a predetermined extent of spatial frequency space has been sampled. .Iaddend.

.Iadd.142. The method of claim 141, wherein said flip angles for said refocusing radio-frequency pulses are also selected to vary among pulses to yield a signal evolution for the associated train of spin echoes for at least one additional substance of interest in said object, with corresponding T1 and T2 relaxation times and spin density of interest, and wherein said signal evolutions corresponding to said substance in the method of claim 141 and said additional substance result in T2-weighted contrast in the corresponding image(s) that is substantially the same as T2-weighted contrast that would be provided by imaging said object by using a turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence that has constant flip angles, with values of 180 degrees, for the refocusing radio-frequency pulses, and that has an effective echo time typical for T2-weighted clinical magnetic resonance imaging. .Iaddend.

.Iadd.143. The method of claim 142, wherein the duration of the spin-echo trains for said signal evolutions for said substances is at least twice the duration of the spin-echo train for said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence and an effective echo time corresponding to said spin-echo trains for said signal evolutions for said substances is at least twice said effective echo time for said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence. .Iaddend.

.Iadd.144. The method of claim 142, wherein the duration of the spin-echo trains for said signal evolutions for said substances is greater than approximately four times the T2 relaxation time for at least one of said substances. .Iaddend.

.Iadd.145. The method of claim 142, wherein an effective echo time corresponding to said spin-echo trains for said signal evolutions for said substances is greater than approximately two times the T2 relaxation time for at least one of said substances. .Iaddend.

.Iadd.146. The method of claim 141, wherein said flip angles and phase angles for the refocusing radio-frequency pulses are calculated using an appropriate analytical or computer-based algorithm, either prior to or substantially simultaneous with the execution of the pulse sequence. .Iaddend.

.Iadd.147. The method of claim 141, wherein a contrast preparation comprising generating at least one of at least one radio-frequency pulse, at least one magnetic-field gradient pulse, and at least one time delay, whereby said contrast preparation encodes the magnetization with at least one desired image contrast, immediately precedes at least one of said excitation radio-frequency pulses. .Iaddend.

.Iadd.148. The method of claim 141, wherein a three-dimensional volume of spatial-frequency space is sampled. .Iaddend.

.Iadd.149. The method of claim 141, wherein at least one said data-acquisition step is initiated by a trigger signal to synchronize the pulse sequence with at least one of at least one external temporal event and at least one internal temporal event. .Iaddend.

.Iadd.150. The method of claim 141, wherein the spatial-encoding magnetic-field gradient pulses applied during each said data-acquisition step are configured so as to collect data, following each of at least one of the refocusing radio-frequency pulses, for one line in spatial-frequency space which is parallel to all other lines of data so collected, so as to collect the data using a magnetic resonance imaging technique selected from the group consisting of rapid acquisition with relaxation enhancement (RARE), fast spin echo (FSE), and turbo spin echo (TSE or TurboSE). .Iaddend.

.Iadd.151. The method of claim 141, wherein said flip angles for said refocusing radio-frequency pulses reach, at 50% of the total number of echoes in said train of spin echoes, a value approximately midway between said initial flip angle and the lowest flip angle. .Iaddend.

.Iadd.152. A method for generating a spin-echo pulse sequence for operating a magnetic resonance imaging apparatus for imaging an object, said method comprising: calculating flip angles of refocusing radio-frequency pulses that are applied in a data-acquisition step, wherein, to permit during said data-acquisition step at least one of lengthening usable echo-train duration, reducing power deposition and incorporating desired image contrast into the signal evolutions, said calculation provides flip angles to yield a signal evolution for the associated train of spin echoes for at least one substance of interest in said object, with corresponding T1 and T2 relaxation times and spin density of interest, wherein said flip angles for said refocusing radio-frequency pulses decrease, within the first approximately 15% of the total number of echoes, to a value that is no more than approximately one-third of the initial flip angle for said refocusing radio-frequency pulses, and said flip angles then increase for the remaining echoes in said train of spin echoes; providing said data-acquisition step based on a spin-echo-train pulse sequence, said data-acquisition step comprises: providing an excitation radio-frequency pulse having a flip angle and phase angle; providing at least two refocusing radio-frequency pulses, each having a flip angle and phase angle with said flip angles determined by said calculation step; providing magnetic-field gradient pulses that perform at least one of encoding spatial information into at least one of the radio-frequency magnetic resonance signals that follow at least one of said refocusing radio-frequency pulses and dephasing transverse magnetization associated with undesired signal pathways to reduce or eliminate contribution of said transverse magnetization to sampled signals; and providing data sampling, associated with magnetic-field gradient pulses that perform spatial encoding; providing a magnetization-recovery step, said magnetization-recovery step comprises at least one of a time delay and at least one magnetic-field gradient pulse; and repeating at least one of said calculating flip angles, said data-acquisition step and said magnetization-recovery step until a predetermined extent of spatial frequency space has been sampled. .Iaddend.

.Iadd.153. A method for generating a spin-echo pulse sequence for operating a magnetic resonance imaging apparatus for imaging an object, said method comprising: providing a data-acquisition step based on a spin-echo-train pulse sequence, said data-acquisition step comprises: providing an excitation radio-frequency pulse having a flip angle and phase angle; providing at least two refocusing radio-frequency pulses, each having a flip angle and phase angle, wherein, to permit during said data-acquisition step at least one of lengthening usable echo-train duration, reducing power deposition and incorporating desired image contrast into the signal evolutions, at least one of said angles is selected to vary among pulses to yield a signal evolution for the associated train of spin echoes for at least one substance of interest in said object, with corresponding T1 and T2 relaxation times and spin density of interest, and wherein, for said signal evolution for said substance, the signal amplitude decreases, within the first approximately 20% of the total number of echoes, to a value that is no more than approximately two-thirds of the initial value for said signal evolution, and the signal amplitude is then substantially constant up to at least approximately 50% of the total number of echoes; providing magnetic-field gradient pulses that perform at least one of encoding spatial information into at least one of the radio-frequency magnetic resonance signals that follow at least one of said refocusing radio-frequency pulses and dephasing transverse magnetization associated with undesired signal pathways to reduce or eliminate contribution of said transverse magnetization to sampled signals; and providing data sampling, associated with magnetic-field gradient pulses that perform spatial encoding; providing a magnetization-recovery step, said magnetization-recovery step comprises at least one of a time delay and at least one magnetic-field gradient pulse; and repeating at least one of said data-acquisition step and said magnetization-recovery step until a predetermined extent of spatial frequency space has been sampled. .Iaddend.

.Iadd.154. The method of claim 153, wherein at least one of said signal amplitude decreases within the first approximately 15% of the total number of echoes and said signal amplitude decreases to a value that is no more than approximately one-half of the initial value for said signal evolution. .Iaddend.

.Iadd.155. The method of claim 153, wherein said signal amplitude decreases within the first approximately 15% of the total number of echoes and said signal amplitude decreases to a value that is no more than approximately one-half of the initial value for said signal evolution. .Iaddend.

.Iadd.156. A method for generating a spin-echo pulse sequence for operating a magnetic resonance imaging apparatus for imaging an object, said method comprising: calculating flip angles and phase angles of refocusing radio-frequency pulses that are applied in a data-acquisition step, wherein, to permit during said data-acquisition step at least one of lengthening usable echo-train duration, reducing power deposition and incorporating desired image contrast into the signal evolutions, said calculation provides flip angles and phase angles to yield a signal evolution for the associated train of spin echoes for at least one substance of interest in said object, with corresponding T1 and T2 relaxation times and spin density of interest, and wherein, for said signal evolution for said substance, the signal amplitude decreases, within the first approximately 20% of the total number of echoes, to a value that is no more than approximately two-thirds of the initial value for said signal evolution, and the signal amplitude is then substantially constant up to at least approximately 50% of the total number of echoes; providing said data-acquisition step based on a spin-echo-train pulse sequence, said data-acquisition step comprises: providing an excitation radio-frequency pulse having a flip angle and phase angle; providing at least two refocusing radio-frequency pulses, each having a flip angle and phase angle as determined by said calculation step; providing magnetic-field gradient pulses that perform at least one of encoding spatial information into at least one of the radio-frequency magnetic resonance signals that follow at least one of said refocusing radio-frequency pulses and dephasing transverse magnetization associated with undesired signal pathways to reduce or eliminate contribution of said transverse magnetization to sampled signals; and providing data sampling, associated with magnetic-field gradient pulses that perform spatial encoding; providing a magnetization-recovery step, said magnetization-recovery step comprises at least one of a time delay and at least one magnetic-field gradient pulse; and repeating at least one of said calculating flip angles and phase angles, said data-acquisition step and said magnetization-recovery step until a predetermined extent of spatial frequency space has been sampled. .Iaddend.

.Iadd.157. A magnetic resonance imaging apparatus generating a spin-echo pulse sequence configured for operating said magnetic resonance imaging apparatus that is configured for imaging an object, the apparatus comprising: a main magnet system generating a steady magnetic field; a gradient magnet system generating temporary gradient magnetic fields; a radio-frequency transmitter system generating radio-frequency pulses; a radio-frequency receiver system receiving magnetic resonance signals; a reconstruction unit reconstructing an image of the object from the received magnetic resonance signals; and a control unit generating signals controlling the gradient magnet system, the radio-frequency transmitter system, the radio-frequency receiver system, and the reconstruction unit, wherein the control unit generates signals causing: providing a data-acquisition step based on a spin-echo-train pulse sequence, said data-acquisition step comprises: providing an excitation radio-frequency pulse having a flip angle and phase angle; providing at least two refocusing radio-frequency pulses, each having a flip angle and phase angle, wherein, to permit during said data-acquisition step at least one of lengthening usable echo-train duration, reducing power deposition and incorporating desired image contrast into the signal evolutions, at least one of said angles is selected to vary among pulses to yield a signal evolution for the associated train of spin echoes for at least one first substance of interest in said object, with corresponding T1 and T2 relaxation times and spin density of interest, and to yield a signal evolution for the associated train of spin echoes for at least one second substance of interest in said object, with corresponding T1 and T2 relaxation times and spin density of interest, wherein said signal evolutions result in T2-weighted contrast in the corresponding image(s) that is substantially the same as T2-weighted contrast that would be provided by imaging said object by using a turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence that has constant flip angles, with values of 180 degrees, for the refocusing radio-frequency pulses, and wherein at least one of the duration of the spin-echo trains for said signal evolutions for said substances is at least twice the duration of the spin-echo train for said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence and an effective echo time corresponding to said spin-echo trains for said signal evolutions for said substances is at least twice an effective echo time for said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence; providing magnetic-field gradient pulses that perform at least one of encoding spatial information into at least one of the radio-frequency magnetic resonance signals that follow at least one of said refocusing radio-frequency pulses and dephasing transverse magnetization associated with undesired signal pathways to reduce or eliminate contribution of said transverse magnetization to sampled signals; and providing data sampling, associated with magnetic-field gradient pulses that perform spatial encoding; and repeating said data-acquisition step until a predetermined extent of spatial frequency space has been sampled. .Iaddend.

.Iadd.158. A magnetic resonance imaging apparatus generating a spin-echo pulse sequence configured for operating said magnetic resonance imaging apparatus that is configured for imaging an object, the apparatus comprising: a main magnet system generating a steady magnetic field; a gradient magnet system generating temporary gradient magnetic fields; a radio-frequency transmitter system generating radio-frequency pulses; a radio-frequency receiver system receiving magnetic resonance signals; a reconstruction unit reconstructing an image of the object from the received magnetic resonance signals; and a control unit generating signals controlling the gradient magnet system, the radio-frequency transmitter system, the radio-frequency receiver system, and the reconstruction unit, wherein the control unit generates signals causing: calculating flip angles and phase angles of refocusing radio-frequency pulses that are applied in a data-acquisition step, wherein, to permit during said data-acquisition step at least one of lengthening usable echo-train duration, reducing power deposition and incorporating desired image contrast into the signal evolutions, said calculation provides flip angles and phase angles to yield a signal evolution for the associated train of spin echoes for at least one first substance of interest in said object, with corresponding T1 and T2 relaxation times and spin density of interest, and to yield a signal evolution for the associated train of spin echoes for at least one second substance of interest in said object, with corresponding T1 and T2 relaxation times and spin density of interest, wherein said signal evolutions result in T2-weighted contrast in the corresponding image(s) that is substantially the same as T2-weighted contrast that would be provided by imaging said object by using a turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence that has constant flip angles, with values of 180 degrees, for the refocusing radio-frequency pulses, and wherein at least one of the duration of the spin-echo trains for said signal evolutions for said substances is at least twice the duration of the spin-echo train for said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence and an effective echo time corresponding to said spin-echo trains for said signal evolutions for said substances is at least twice an effective echo time for said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence; providing said data-acquisition step based on a spin-echo-train pulse sequence, said data-acquisition step comprises: providing an excitation radio-frequency pulse having a flip angle and phase angle; providing at least two refocusing radio-frequency pulses, each having a flip angle and phase angle as determined by said calculation step; providing magnetic-field gradient pulses that perform at least one of encoding spatial information into at least one of the radio-frequency magnetic resonance signals that follow at least one of said refocusing radio-frequency pulses and dephasing transverse magnetization associated with undesired signal pathways to reduce or eliminate contribution of said transverse magnetization to sampled signals; and providing data sampling, associated with magnetic-field gradient pulses that perform spatial encoding; and repeating at least one of said calculating flip angles and phase angles and said data-acquisition step until a predetermined extent of spatial frequency space has been sampled. .Iaddend.

.Iadd.159. A magnetic resonance imaging apparatus generating a spin-echo pulse sequence configured for operating said magnetic resonance imaging apparatus that is configured for imaging an object, the apparatus comprising: a main magnet system generating a steady magnetic field; a gradient magnet system generating temporary gradient magnetic fields; a radio-frequency transmitter system generating radio-frequency pulses; a radio-frequency receiver system receiving magnetic resonance signals; a reconstruction unit reconstructing an image of the object from the received magnetic resonance signals; and a control unit generating signals controlling the gradient magnet system, the radio-frequency transmitter system, the radio-frequency receiver system, and the reconstruction unit, wherein the control unit generates signals causing: providing a data-acquisition step based on a spin-echo-train pulse sequence, said data-acquisition step comprises: providing an excitation radio-frequency pulse having a flip angle and phase angle; providing at least two refocusing radio-frequency pulses, each having a flip angle and phase angle, wherein, to permit during said data-acquisition step at least one of lengthening usable echo-train duration, reducing power deposition and incorporating desired image contrast into the signal evolutions, said flip angles for said refocusing radio-frequency pulses are selected to vary among pulses to yield a signal evolution for the associated train of spin echoes for at least one substance of interest in said object, with corresponding T1 and T2 relaxation times and spin density of interest, and wherein said flip angles for said refocusing radio-frequency pulses decrease, within the first approximately 15% of the total number of echoes, to a value that is no more than approximately one-third of the initial flip angle for said refocusing radio-frequency pulses, and said flip angles then increase for the remaining echoes in said train of spin echoes; providing magnetic-field gradient pulses that perform at least one of encoding spatial information into at least one of the radio-frequency magnetic resonance signals that follow at least one of said refocusing radio-frequency pulses and dephasing transverse magnetization associated with undesired signal pathways to reduce or eliminate contribution of said transverse magnetization to sampled signals; and providing data sampling, associated with magnetic-field gradient pulses that perform spatial encoding; providing a magnetization-recovery step, said magnetization-recovery step comprises at least one of a time delay and at least one magnetic-field gradient pulse; and repeating at least one of said data-acquisition step and said magnetization-recovery step until a predetermined extent of spatial frequency space has been sampled. .Iaddend.

.Iadd.160. A magnetic resonance imaging apparatus generating a spin-echo pulse sequence configured for operating said magnetic resonance imaging apparatus that is configured for imaging an object, the apparatus comprising: a main magnet system generating a steady magnetic field; a gradient magnet system generating temporary gradient magnetic fields; a radio-frequency transmitter system generating radio-frequency pulses; a radio-frequency receiver system receiving magnetic resonance signals; a reconstruction unit reconstructing an image of the object from the received magnetic resonance signals; and a control unit generating signals controlling the gradient magnet system, the radio-frequency transmitter system, the radio-frequency receiver system, and the reconstruction unit, wherein the control unit generates signals causing: calculating flip angles of refocusing radio-frequency pulses that are applied in a data-acquisition step, wherein, to permit during said data-acquisition step at least one of lengthening usable echo-train duration, reducing power deposition and incorporating desired image contrast into the signal evolutions, said calculation provides flip angles to yield a signal evolution for the associated train of spin echoes for at least one substance of interest in said object, with corresponding T1 and T2 relaxation times and spin density of interest, wherein said flip angles for said refocusing radio-frequency pulses decrease, within the first approximately 15% of the total number of echoes, to a value that is no more than approximately one-third of the initial flip angle for said refocusing radio-frequency pulses, and said flip angles then increase for the remaining echoes in said train of spin echoes; providing said data-acquisition step based on a spin-echo-train pulse sequence, said data-acquisition step comprises: providing an excitation radio-frequency pulse having a flip angle and phase angle; providing at least two refocusing radio-frequency pulses, each having a flip angle and phase angle with said flip angles determined by said calculation step; providing magnetic-field gradient pulses that perform at least one of encoding spatial information into at least one of the radio-frequency magnetic resonance signals that follow at least one of said refocusing radio-frequency pulses and dephasing transverse magnetization associated with undesired signal pathways to reduce or eliminate contribution of said transverse magnetization to sampled signals; and providing data sampling, associated with magnetic-field gradient pulses that perform spatial encoding; providing a magnetization-recovery step, said magnetization-recovery step comprises at least one of a time delay and at least one magnetic-field gradient pulse; and repeating at least one of said calculating flip angles, said data-acquisition step and said magnetization-recovery step until a predetermined extent of spatial frequency space has been sampled. .Iaddend.

.Iadd.161. A magnetic resonance imaging apparatus generating a spin-echo pulse sequence configured for operating said magnetic resonance imaging apparatus that is configured for imaging an object, the apparatus comprising: a main magnet system generating a steady magnetic field; a gradient magnet system generating temporary gradient magnetic fields; a radio-frequency transmitter system generating radio-frequency pulses; a radio-frequency receiver system receiving magnetic resonance signals; a reconstruction unit reconstructing an image of the object from the received magnetic resonance signals; and a control unit generating signals controlling the gradient magnet system, the radio-frequency transmitter system, the radio-frequency receiver system, and the reconstruction unit, wherein the control unit generates signals causing: providing a data-acquisition step based on a spin-echo-train pulse sequence, said data-acquisition step comprises: providing an excitation radio-frequency pulse having a flip angle and phase angle; providing at least two refocusing radio-frequency pulses, each having a flip angle and phase angle, wherein, to permit during said data-acquisition step at least one of lengthening usable echo-train duration, reducing power deposition and incorporating desired image contrast into the signal evolutions, at least one of said angles is selected to vary among pulses to yield a signal evolution for the associated train of spin echoes for at least one substance of interest in said object, with corresponding T1 and T2 relaxation times and spin density of interest, and wherein, for said signal evolution for said substance, the signal amplitude decreases, within the first approximately 20% of the total number of echoes, to a value that is no more than approximately two-thirds of the initial value for said signal evolution, and the signal amplitude is then substantially constant up to at least approximately 50% of the total number of echoes; providing magnetic-field gradient pulses that perform at least one of encoding spatial information into at least one of the radio-frequency magnetic resonance signals that follow at least one of said refocusing radio-frequency pulses and dephasing transverse magnetization associated with undesired signal pathways to reduce or eliminate contribution of said transverse magnetization to sampled signals; and providing data sampling, associated with magnetic-field gradient pulses that perform spatial encoding; providing a magnetization-recovery step, said magnetization-recovery step comprises at least one of a time delay and at least one magnetic-field gradient pulse; and repeating at least one of said data-acquisition step and said magnetization-recovery step until a predetermined extent of spatial frequency space has been sampled. .Iaddend.

.Iadd.162. A magnetic resonance imaging apparatus generating a spin-echo pulse sequence configured for operating said magnetic resonance imaging apparatus that is configured for imaging an object, the apparatus comprising: a main magnet system generating a steady magnetic field; a gradient magnet system generating temporary gradient magnetic fields; a radio-frequency transmitter system generating radio-frequency pulses; a radio-frequency receiver system receiving magnetic resonance signals; a reconstruction unit reconstructing an image of the object from the received magnetic resonance signals; and a control unit generating signals controlling the gradient magnet system, the radio-frequency transmitter system, the radio-frequency receiver system, and the reconstruction unit, wherein the control unit generates signals causing: calculating flip angles and phase angles of refocusing radio-frequency pulses that are applied in a data-acquisition step, wherein, to permit during said data-acquisition step at least one of lengthening usable echo-train duration, reducing power deposition and incorporating desired image contrast into the signal evolutions, said calculation provides flip angles and phase angles to yield a signal evolution for the associated train of spin echoes for at least one substance of interest in said object, with corresponding T1 and T2 relaxation times and spin density of interest, and wherein, for said signal evolution for said substance, the signal amplitude decreases, within the first approximately 20% of the total number of echoes, to a value that is no more than approximately two-thirds of the initial value for said signal evolution, and the signal amplitude is then substantially constant up to at least approximately 50% of the total number of echoes; providing said data-acquisition step based on a spin-echo-train pulse sequence, said data-acquisition step comprises: providing an excitation radio-frequency pulse having a flip angle and phase angle; providing at least two refocusing radio-frequency pulses, each having a flip angle and phase angle as determined by said calculation step; providing magnetic-field gradient pulses that perform at least one of encoding spatial information into at least one of the radio-frequency magnetic resonance signals that follow at least one of said refocusing radio-frequency pulses and dephasing transverse magnetization associated with undesired signal pathways to reduce or eliminate contribution of said transverse magnetization to sampled signals; and providing data sampling, associated with magnetic-field gradient pulses that perform spatial encoding; providing a magnetization-recovery step, said magnetization-recovery step comprises at least one of a time delay and at least one magnetic-field gradient pulse; and repeating at least one of said calculating flip angles and phase angles, said data-acquisition step and said magnetization-recovery step until a predetermined extent of spatial frequency space has been sampled. .Iaddend.

.Iadd.163. A magnetic resonance imaging means generating a spin-echo pulse sequence configured for operating said magnetic resonance imaging means that is configured for imaging an object, the imaging means comprising: a main magnet means for generating a steady magnetic field; a gradient magnet means for generating temporary gradient magnetic fields; a radio-frequency transmitter means for generating radio-frequency pulses; a radio-frequency receiver means for receiving magnetic resonance signals; a reconstruction means for reconstructing an image of the object from the received magnetic resonance signals; and a control means for generating signals controlling the gradient magnet means, the radio-frequency transmitter means, the radio-frequency receiver means, and the reconstruction means, wherein the control means generates signals causing: providing a data-acquisition step based on a spin-echo-train pulse sequence, said data-acquisition step comprises: providing an excitation radio-frequency pulse having a flip angle and phase angle; providing at least two refocusing radio-frequency pulses, each having a flip angle and phase angle, wherein, to permit during said data-acquisition step at least one of lengthening usable echo-train duration, reducing power deposition and incorporating desired image contrast into the signal evolutions, at least one of said angles is selected to vary among pulses to yield a signal evolution for the associated train of spin echoes for at least one first substance of interest in said object, with corresponding T1 and T2 relaxation times and spin density of interest, and to yield a signal evolution for the associated train of spin echoes for at least one second substance of interest in said object, with corresponding T1 and T2 relaxation times and spin density of interest, wherein said signal evolutions result in T2-weighted contrast in the corresponding image(s) that is substantially the same as T2-weighted contrast that would be provided by imaging said object by using a turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence that has constant flip angles, with values of 180 degrees, for the refocusing radio-frequency pulses, and wherein at least one of the duration of the spin-echo trains for said signal evolutions for said substances is at least twice the duration of the spin-echo train for said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence and an effective echo time corresponding to said spin-echo trains for said signal evolutions for said substances is at least twice an effective echo time for said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence; providing magnetic-field gradient pulses that perform at least one of encoding spatial information into at least one of the radio-frequency magnetic resonance signals that follow at least one of said refocusing radio-frequency pulses and dephasing transverse magnetization associated with undesired signal pathways to reduce or eliminate contribution of said transverse magnetization to sampled signals; and providing data sampling, associated with magnetic-field gradient pulses that perform spatial encoding; and repeating said data-acquisition step until a predetermined extent of spatial frequency space has been sampled. .Iaddend.

.Iadd.164. A magnetic resonance imaging means generating a spin-echo pulse sequence configured for operating said magnetic resonance imaging means that is configured for imaging an object, the imaging means comprising: a main magnet means for generating a steady magnetic field; a gradient magnet means for generating temporary gradient magnetic fields; a radio-frequency transmitter means for generating radio-frequency pulses; a radio-frequency receiver means for receiving magnetic resonance signals; a reconstruction means for reconstructing an image of the object from the received magnetic resonance signals; and a control means for generating signals controlling the gradient magnet means, the radio-frequency transmitter means, the radio-frequency receiver means, and the reconstruction means, wherein the control means generates signals causing: calculating flip angles and phase angles of refocusing radio-frequency pulses that are applied in a data-acquisition step, wherein, to permit during said data-acquisition step at least one of lengthening usable echo-train duration, reducing power deposition and incorporating desired image contrast into the signal evolutions, said calculation provides flip angles and phase angles to yield a signal evolution for the associated train of spin echoes for at least one first substance of interest in said object, with corresponding T1 and T2 relaxation times and spin density of interest, and to yield a signal evolution for the associated train of spin echoes for at least one second substance of interest in said object, with corresponding T1 and T2 relaxation times and spin density of interest, wherein said signal evolutions result in T2-weighted contrast in the corresponding image(s) that is substantially the same as T2-weighted contrast that would be provided by imaging said object by using a turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence that has constant flip angles, with values of 180 degrees, for the refocusing radio-frequency pulses, and wherein at least one of the duration of the spin-echo trains for said signal evolutions for said substances is at least twice the duration of the spin-echo train for said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence and an effective echo time corresponding to said spin-echo trains for said signal evolutions for said substances is at least twice an effective echo time for said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence; providing said data-acquisition step based on a spin-echo-train pulse sequence, said data-acquisition step comprises: providing an excitation radio-frequency pulse having a flip angle and phase angle; providing at least two refocusing radio-frequency pulses, each having a flip angle and phase angle as determined by said calculation step; providing magnetic-field gradient pulses that perform at least one of encoding spatial information into at least one of the radio-frequency magnetic resonance signals that follow at least one of said refocusing radio-frequency pulses and dephasing transverse magnetization associated with undesired signal pathways to reduce or eliminate contribution of said transverse magnetization to sampled signals; and providing data sampling, associated with magnetic-field gradient pulses that perform spatial encoding; and repeating at least one of said calculating flip angles and phase angles and said data-acquisition step until a predetermined extent of spatial frequency space has been sampled. .Iaddend.

.Iadd.165. A magnetic resonance imaging means generating a spin-echo pulse sequence configured for operating said magnetic resonance imaging means that is configured for imaging an object, the imaging means comprising: a main magnet means for generating a steady magnetic field; a gradient magnet means for generating temporary gradient magnetic fields; a radio-frequency transmitter means for generating radio-frequency pulses; a radio-frequency receiver means for receiving magnetic resonance signals; a reconstruction means for reconstructing an image of the object from the received magnetic resonance signals; and a control means for generating signals controlling the gradient magnet means, the radio-frequency transmitter means, the radio-frequency receiver means, and the reconstruction means, wherein the control means generates signals causing: providing a data-acquisition step based on a spin-echo-train pulse sequence, said data-acquisition step comprises: providing an excitation radio-frequency pulse having a flip angle and phase angle; providing at least two refocusing radio-frequency pulses, each having a flip angle and phase angle, wherein, to permit during said data-acquisition step at least one of lengthening usable echo-train duration, reducing power deposition and incorporating desired image contrast into the signal evolutions, said flip angles for said refocusing radio-frequency pulses are selected to vary among pulses to yield a signal evolution for the associated train of spin echoes for at least one substance of interest in said object, with corresponding T1 and T2 relaxation times and spin density of interest, and wherein said flip angles for said refocusing radio-frequency pulses decrease, within the first approximately 15% of the total number of echoes, to a value that is no more than approximately one-third of the initial flip angle for said refocusing radio-frequency pulses, and said flip angles then increase for the remaining echoes in said train of spin echoes; providing magnetic-field gradient pulses that perform at least one of encoding spatial information into at least one of the radio-frequency magnetic resonance signals that follow at least one of said refocusing radio-frequency pulses and dephasing transverse magnetization associated with undesired signal pathways to reduce or eliminate contribution of said transverse magnetization to sampled signals; and providing data sampling, associated with magnetic-field gradient pulses that perform spatial encoding; providing a magnetization-recovery step, said magnetization-recovery step comprises at least one of a time delay and at least one magnetic-field gradient pulse; and repeating at least one of said data-acquisition step and said magnetization-recovery step until a predetermined extent of spatial frequency space has been sampled. .Iaddend.

.Iadd.166. A magnetic resonance imaging means generating a spin-echo pulse sequence configured for operating said magnetic resonance imaging means that is configured for imaging an object, the imaging means comprising: a main magnet means for generating a steady magnetic field; a gradient magnet means for generating temporary gradient magnetic fields; a radio-frequency transmitter means for generating radio-frequency pulses; a radio-frequency receiver means for receiving magnetic resonance signals; a reconstruction means for reconstructing an image of the object from the received magnetic resonance signals; and a control means for generating signals controlling the gradient magnet means, the radio-frequency transmitter means, the radio-frequency receiver means, and the reconstruction means, wherein the control means generates signals causing: calculating flip angles of refocusing radio-frequency pulses that are applied in a data-acquisition step, wherein, to permit during said data-acquisition step at least one of lengthening usable echo-train duration, reducing power deposition and incorporating desired image contrast into the signal evolutions, said calculation provides flip angles to yield a signal evolution for the associated train of spin echoes for at least one substance of interest in said object, with corresponding T1 and T2 relaxation times and spin density of interest, wherein said flip angles for said refocusing radio-frequency pulses decrease, within the first approximately 15% of the total number of echoes, to a value that is no more than approximately one-third of the initial flip angle for said refocusing radio-frequency pulses, and said flip angles then increase for the remaining echoes in said train of spin echoes; providing said data-acquisition step based on a spin-echo-train pulse sequence, said data-acquisition step comprises: providing an excitation radio-frequency pulse having a flip angle and phase angle; providing at least two refocusing radio-frequency pulses, each having a flip angle and phase angle with said flip angles determined by said calculation step; providing magnetic-field gradient pulses that perform at least one of encoding spatial information into at least one of the radio-frequency magnetic resonance signals that follow at least one of said refocusing radio-frequency pulses and dephasing transverse magnetization associated with undesired signal pathways to reduce or eliminate contribution of said transverse magnetization to sampled signals; and providing data sampling, associated with magnetic-field gradient pulses that perform spatial encoding; providing a magnetization-recovery step, said magnetization-recovery step comprises at least one of a time delay and at least one magnetic-field gradient pulse; and repeating at least one of said calculating flip angles, said data-acquisition step and said magnetization-recovery step until a predetermined extent of spatial frequency space has been sampled. .Iaddend.

.Iadd.167. A magnetic resonance imaging means generating a spin-echo pulse sequence configured for operating said magnetic resonance imaging means that is configured for imaging an object, the imaging means comprising: a main magnet means for generating a steady magnetic field; a gradient magnet means for generating temporary gradient magnetic fields; a radio-frequency transmitter means for generating radio-frequency pulses; a radio-frequency receiver means for receiving magnetic resonance signals; a reconstruction means for reconstructing an image of the object from the received magnetic resonance signals; and a control means for generating signals controlling the gradient magnet means, the radio-frequency transmitter means, the radio-frequency receiver means, and the reconstruction means, wherein the control means generates signals causing: providing a data-acquisition step based on a spin-echo-train pulse sequence, said data-acquisition step comprises: providing an excitation radio-frequency pulse having a flip angle and phase angle; providing at least two refocusing radio-frequency pulses, each having a flip angle and phase angle, wherein, to permit during said data-acquisition step at least one of lengthening usable echo-train duration, reducing power deposition and incorporating desired image contrast into the signal evolutions, at least one of said angles is selected to vary among pulses to yield a signal evolution for the associated train of spin echoes for at least one substance of interest in said object, with corresponding T1 and T2 relaxation times and spin density of interest, and wherein, for said signal evolution for said substance, the signal amplitude decreases, within the first approximately 20% of the total number of echoes, to a value that is no more than approximately two-thirds of the initial value for said signal evolution, and the signal amplitude is then substantially constant up to at least approximately 50% of the total number of echoes; providing magnetic-field gradient pulses that perform at least one of encoding spatial information into at least one of the radio-frequency magnetic resonance signals that follow at least one of said refocusing radio-frequency pulses and dephasing transverse magnetization associated with undesired signal pathways to reduce or eliminate contribution of said transverse magnetization to sampled signals; and providing data sampling, associated with magnetic-field gradient pulses that perform spatial encoding; providing a magnetization-recovery step, said magnetization-recovery step comprises at least one of a time delay and at least one magnetic-field gradient pulse; and repeating at least one of said data-acquisition step and said magnetization-recovery step until a predetermined extent of spatial frequency space has been sampled. .Iaddend.

.Iadd.168. A magnetic resonance imaging means generating a spin-echo pulse sequence configured for operating said magnetic resonance imaging means that is configured for imaging an object, the imaging means comprising: a main magnet means for generating a steady magnetic field; a gradient magnet means for generating temporary gradient magnetic fields; a radio-frequency transmitter means for generating radio-frequency pulses; a radio-frequency receiver means for receiving magnetic resonance signals; a reconstruction means for reconstructing an image of the object from the received magnetic resonance signals; and a control means for generating signals controlling the gradient magnet means, the radio-frequency transmitter means, the radio-frequency receiver means, and the reconstruction means, wherein the control means generates signals causing: calculating flip angles and phase angles of refocusing radio-frequency pulses that are applied in a data-acquisition step, wherein, to permit during said data-acquisition step at least one of lengthening usable echo-train duration, reducing power deposition and incorporating desired image contrast into the signal evolutions, said calculation provides flip angles and phase angles to yield a signal evolution for the associated train of spin echoes for at least one substance of interest in said object, with corresponding T1 and T2 relaxation times and spin density of interest, and wherein, for said signal evolution for said substance, the signal amplitude decreases, within the first approximately 20% of the total number of echoes, to a value that is no more than approximately two-thirds of the initial value for said signal evolution, and the signal amplitude is then substantially constant up to at least approximately 50% of the total number of echoes; providing said data-acquisition step based on a spin-echo-train pulse sequence, said data-acquisition step comprises: providing an excitation radio-frequency pulse having a flip angle and phase angle; providing at least two refocusing radio-frequency pulses, each having a flip angle and phase angle as determined by said calculation step; providing magnetic-field gradient pulses that perform at least one of encoding spatial information into at least one of the radio-frequency magnetic resonance signals that follow at least one of said refocusing radio-frequency pulses and dephasing transverse magnetization associated with undesired signal pathways to reduce or eliminate contribution of said transverse magnetization to sampled signals; and providing data sampling, associated with magnetic-field gradient pulses that perform spatial encoding; providing a magnetization-recovery step, said magnetization-recovery step comprises at least one of a time delay and at least one magnetic-field gradient pulse; and repeating at least one of said calculating flip angles and phase angles, said data-acquisition step and said magnetization-recovery step until a predetermined extent of spatial frequency space has been sampled. .Iaddend.

.Iadd.169. The method of claim 80, wherein at least one of said effective echo time corresponding to said spin-echo trains for said signal evolutions for said substances is at least on the order of 300 milliseconds and said duration of the spin-echo trains for said signal evolutions for said substances is at least on the order of 600 milliseconds. .Iaddend.

.Iadd.170. The method of claim 169, wherein said effective echo time for said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence has a value typical for T2-weighted clinical magnetic resonance imaging. .Iaddend.

.Iadd.171. The method of claim 170, wherein a three-dimensional volume of spatial-frequency space is sampled. .Iaddend.

.Iadd.172. The method of claim 171, wherein at least one of said duration of the spin-echo train for said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence is less than 300 milliseconds and said effective echo time for said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence has a value typical for T2-weighted clinical magnetic resonance imaging of the brain. .Iaddend.

.Iadd.173. The method of claim 172, wherein said angles, selected to vary for said refocusing radio-frequency pulses, reduce power deposition by at least 30% compared to power deposition that would be achieved by using constant flip angles, with values of 180 degrees, for the refocusing radio-frequency pulses. .Iaddend.

.Iadd.174. The method of claim 173, wherein the number of refocusing radio-frequency pulses following at least one said excitation radio-frequency pulse is greater than 50. .Iaddend.

.Iadd.175. The method of claim 174, wherein said flip angles and phase angles for the refocusing radio-frequency pulses are calculated using an appropriate analytical or computer-based algorithm, either prior to or substantially simultaneous with the execution of the pulse sequence. .Iaddend.

.Iadd.176. A method for generating a spin-echo pulse sequence for operating a magnetic resonance imaging apparatus for imaging an object, said method comprising: providing a data-acquisition step based on a spin-echo-train pulse sequence, said data-acquisition step comprises: providing an excitation radio-frequency pulse having a flip angle and phase angle; providing at least two refocusing radio-frequency pulses, each having a flip angle and phase angle, wherein, to permit during said data-acquisition step at least one of lengthening usable echo-train duration, reducing power deposition and incorporating desired image contrast into the signal evolutions, at least one of said angles is selected to vary among pulses to yield a signal evolution for the associated train of spin echoes for at least one first substance of interest in said object, with corresponding T1 and T2 relaxation times and spin density of interest, and to yield a signal evolution for the associated train of spin echoes for at least one second substance of interest in said object, with corresponding T1 and T2 relaxation times and spin density of interest, wherein said signal evolutions result in T2-weighted contrast in the corresponding image(s) that is substantially the same as T2-weighted contrast that would be provided by imaging said object by using a conventional spin-echo pulse sequence, and wherein an effective echo time corresponding to said spin-echo trains for said signal evolutions for said substances is at least twice an echo time for said conventional spin-echo pulse sequence; providing magnetic-field gradient pulses that perform at least one of encoding spatial information into at least one of the radio-frequency magnetic resonance signals that follow at least one of said refocusing radio-frequency pulses and dephasing transverse magnetization associated with undesired signal pathways to reduce or eliminate contribution of said transverse magnetization to sampled signals; and providing data sampling, associated with magnetic-field gradient pulses that perform spatial encoding; and repeating said data-acquisition step until a predetermined extent of spatial frequency space has been sampled. .Iaddend.

.Iadd.177. A magnetic resonance imaging apparatus generating a spin-echo pulse sequence configured for operating said magnetic resonance imaging apparatus that is configured for imaging an object, the apparatus comprising: a main magnet system generating a steady magnetic field; a gradient magnet system generating temporary gradient magnetic fields; a radio-frequency transmitter system generating radio-frequency pulses; a radio-frequency receiver system receiving magnetic resonance signals; a reconstruction unit reconstructing an image of the object from the received magnetic resonance signals; and a control unit generating signals controlling the gradient magnet system, the radio-frequency transmitter system, the radio-frequency receiver system, and the reconstruction unit, wherein the control unit generates signals causing: providing a data-acquisition step based on a spin-echo-train pulse sequence, said data-acquisition step comprises: providing an excitation radio-frequency pulse having a flip angle and phase angle; providing at least two refocusing radio-frequency pulses, each having a flip angle and phase angle, wherein, to permit during said data-acquisition step at least one of lengthening usable echo-train duration, reducing power deposition and incorporating desired image contrast into the signal evolutions, at least one of said angles is selected to vary among pulses to yield a signal evolution for the associated train of spin echoes for at least one first substance of interest in said object, with corresponding T1 and T2 relaxation times and spin density of interest, and to yield a signal evolution for the associated train of spin echoes for at least one second substance of interest in said object, with corresponding T1 and T2 relaxation times and spin density of interest, wherein said signal evolutions result in T2-weighted contrast in the corresponding image(s) that is substantially the same as T2-weighted contrast that would be provided by imaging said object by using a conventional spin-echo pulse sequence, and wherein an effective echo time corresponding to said spin-echo trains for said signal evolutions for said substances is at least twice an echo time for said conventional spin-echo pulse sequence; providing magnetic-field gradient pulses that perform at least one of encoding spatial information into at least one of the radio-frequency magnetic resonance signals that follow at least one of said refocusing radio-frequency pulses and dephasing transverse magnetization associated with undesired signal pathways to reduce or eliminate contribution of said transverse magnetization to sampled signals; and providing data sampling, associated with magnetic-field gradient pulses that perform spatial encoding; and repeating said data-acquisition step until a predetermined extent of spatial frequency space has been sampled. .Iaddend.

.Iadd.178. The apparatus of claim 157, wherein at least one of a time delay and at least one magnetic-field gradient pulse occurs between the end of at least one spin-echo train and the excitation radio-frequency pulse associated with the next spin-echo train. .Iaddend.

.Iadd.179. The apparatus of claim 157, wherein at least one repetition of said data-acquisition step is for the purpose of stabilizing the response of at least one of magnetization related system and apparatus related hardware system. .Iaddend.

.Iadd.180. The apparatus of claim 157, wherein for at least one repetition of said data-acquisition step at least one of at least a fraction of the sampled data is discarded and no data is sampled. .Iaddend.

.Iadd.181. The apparatus of claim 157, wherein said flip angles and phase angles for the refocusing radio-frequency pulses are calculated using an appropriate analytical or computer-based algorithm, either prior to or substantially simultaneous with the execution of the pulse sequence. .Iaddend.

.Iadd.182. The apparatus of claim 157, wherein said flip angles for said refocusing radio-frequency pulses decrease, within the first approximately 15% of the total number of echoes, to a value that is no more than approximately one-third of the initial flip angle for said refocusing radio-frequency pulses, and said flip angles then increase for the remaining echoes in said train of spin echoes. .Iaddend.

.Iadd.183. The apparatus of claim 182, wherein said flip angles for said refocusing radio-frequency pulses reach, at 50% of the total number of echoes in said train of spin echoes, a value approximately midway between said initial flip angle and the lowest flip angle. .Iaddend.

.Iadd.184. The apparatus of claim 157, wherein said flip angles and phase angles for said refocusing radio-frequency pulses are, in addition, selected to reduce power deposition compared to power deposition that would be achieved by using constant flip angles, with values of 180 degrees, for the refocusing radio-frequency pulses. .Iaddend.

.Iadd.185. The apparatus of claim 184, wherein the power deposition at a magnetic field strength of 3 Tesla for the apparatus of claim 157 is below regulatory limits while power deposition that would be achieved by using constant flip angles, with values of 180 degrees, for the refocusing radio-frequency pulses exceeds regulatory limits. .Iaddend.

.Iadd.186. The apparatus of claim 157, wherein said effective echo time corresponding to said spin-echo trains for said signal evolutions for said substances is at least twice the effective echo time for said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence and said duration of the spin-echo trains for said signal evolutions for said substances is at least twice said duration of the spin-echo train for said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence. .Iaddend.

.Iadd.187. The apparatus of claim 157, wherein at least one of said effective echo time corresponding to said spin-echo trains for said signal evolutions for said substances is at least on the order of 300 milliseconds and said duration of the spin-echo trains for said signal evolutions for said substances is at least on the order of 600 milliseconds. .Iaddend.

.Iadd.188. The apparatus of claim 157, wherein said effective echo time corresponding to said spin-echo trains for said signal evolutions for said substances is at least on the order of 300 milliseconds and said duration of the spin-echo trains for said signal evolutions for said substances is at least on the order of 600 milliseconds. .Iaddend.

.Iadd.189. The apparatus of claim 157, wherein said effective echo time for said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence has a value typical for T2-weighted clinical magnetic resonance imaging. .Iaddend.

.Iadd.190. The apparatus of claim 157, wherein said duration of the spin-echo trains for said signal evolutions for said substances is greater than approximately four times the T2 relaxation time for at least one of said substances. .Iaddend.

.Iadd.191. The apparatus of claim 157, wherein said effective echo time corresponding to said spin-echo trains for said signal evolutions for said substances is greater than approximately two times the T2 relaxation time for at least one of said substances. .Iaddend.

.Iadd.192. The apparatus of claim 157, wherein said first and second substances of interest are brain white matter and brain gray matter. .Iaddend.

.Iadd.193. The apparatus of claim 192, wherein at least one of said duration of the spin-echo train for said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence is less than 300 milliseconds and said effective echo time for said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence has a value typical for T2-weighted clinical magnetic resonance imaging of the brain. .Iaddend.

.Iadd.194. The apparatus of claim 157, wherein said first and second substances of interest are spinal cord white matter and spinal cord gray matter. .Iaddend.

.Iadd.195. The apparatus of claim 157, wherein at least one of said substances of interest is at least one of cartilage, ligament and muscle. .Iaddend.

.Iadd.196. The apparatus of claim 192, wherein said duration of the spin-echo train for said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence is less than 300 milliseconds and said effective echo time for said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence has a value typical for T2-weighted clinical magnetic resonance imaging of the brain. .Iaddend.

.Iadd.197. The apparatus of claim 157, wherein the number of refocusing radio-frequency pulses following at least one said excitation radio-frequency pulse is greater than 50. .Iaddend.

.Iadd.198. The apparatus of claim 157, wherein the number of refocusing radio-frequency pulses following at least one said excitation radio-frequency pulse is greater than 100. .Iaddend.

.Iadd.199. The apparatus of claim 157, wherein a contrast preparation comprising generating at least one of at least one radio-frequency pulse, at least one magnetic-field gradient pulse, and at least one time delay, whereby said contrast preparation encodes the magnetization with at least one desired image contrast, immediately precedes at least one of said excitation radio-frequency pulses. .Iaddend.

.Iadd.200. The apparatus of claim 199, wherein said contrast preparation comprises at least an inversion radio-frequency pulse followed by a time delay. .Iaddend.

.Iadd.201. The apparatus of claim 200, wherein said time delay is chosen so that the longitudinal magnetization associated with fluid, such as cerebrospinal fluid, is passing through substantially zero when at least one said excitation radio-frequency pulse is applied. .Iaddend.

.Iadd.202. The apparatus of claim 199, wherein at least one of the radio-frequency pulses is at least one of spatially selective in one of one, two and three dimensions, chemically selective, and adiabatic. .Iaddend.

.Iadd.203. The apparatus of claim 199, wherein at least one said contrast preparation is initiated by a trigger signal to synchronize the pulse sequence with at least one of at least one external temporal event and at least one internal temporal event. .Iaddend.

.Iadd.204. The apparatus of claim 203, wherein said external and internal events comprise at least one of at least one voluntary action, at least one involuntary action, at least one respiratory cycle and at least one cardiac cycle. .Iaddend.

.Iadd.205. The apparatus of claim 199, wherein at least one of at least one radio-frequency pulse and at least one magnetic-field gradient pulse is applied as part of at least one said contrast preparation for the purpose of stabilizing the response of at least one of magnetization related system and apparatus related hardware system. .Iaddend.

.Iadd.206. The apparatus of claim 157, wherein the flip angle for at least one of the refocusing radio-frequency pulses in the first half of at least one spin-echo train is chosen to be sufficiently low to cause the signal from flowing or pulsating fluid in resulting images to be suppressed. .Iaddend.

.Iadd.207. The apparatus of claim 206, wherein said flip angle is less than 30 degrees. .Iaddend.

.Iadd.208. The apparatus of claim 157, wherein a two-dimensional plane of spatial-frequency space is sampled. .Iaddend.

.Iadd.209. The apparatus of claim 157, wherein a three-dimensional volume of spatial-frequency space is sampled. .Iaddend.

.Iadd.210. The apparatus of claim 157, wherein at least one said data-acquisition step is initiated by a trigger signal to synchronize the pulse sequence with at least one of at least one external temporal event and at least one internal temporal event. .Iaddend.

.Iadd.211. The apparatus of claim 210, wherein said external and internal events comprise at least one of at least one voluntary action, at least one involuntary action, at least one respiratory cycle and at least one cardiac cycle. .Iaddend.

.Iadd.212. The apparatus of claim 157, wherein at least one of at least one radio-frequency pulse and at least one magnetic-field gradient pulse is applied as part of at least one said data-acquisition step for the purpose of stabilizing the response of at least one of magnetization related system and apparatus related hardware system. .Iaddend.

.Iadd.213. The apparatus of claim 157, wherein the time periods between consecutive refocusing radio-frequency pulses applied during said data-acquisition steps are all of equal duration. .Iaddend.

.Iadd.214. The apparatus of claim 157, wherein the time periods between consecutive refocusing radio-frequency pulses applied during said data-acquisition steps vary in duration amongst pairs of refocusing radio-frequency pulses during at least one said data-acquisition step. .Iaddend.

.Iadd.215. The apparatus of claim 157 wherein all radio-frequency pulses are at least one of non-spatially selective and non-chemically selective. .Iaddend.

.Iadd.216. The apparatus of claim 157, wherein at least one of the radio-frequency pulses is at least one of spatially selective in one of one, two and three dimensions, chemically selective, and adiabatic. .Iaddend.

.Iadd.217. The apparatus of claim 157, wherein during at least one said data-acquisition step, the phase difference between the phase angle for the excitation radio-frequency pulse and the phase angles for all refocusing radio-frequency pulses is substantially 90 degrees. .Iaddend.

.Iadd.218. The apparatus of claim 157, wherein during at least one said data-acquisition step, the phase difference between the phase angle for any refocusing radio-frequency pulse and the phase angle for the immediately subsequent refocusing radio-frequency pulse is substantially 180 degrees, and the phase difference between the phase angle for the excitation radio-frequency pulse and the phase angle for the first refocusing pulse is one of substantially 0 degrees and substantially 180 degrees. .Iaddend.

.Iadd.219. The apparatus of claim 157, wherein the flip angle for the excitation radio-frequency pulse is substantially one-half of the flip angle for the first refocusing radio-frequency pulse. .Iaddend.

.Iadd.220. The apparatus of claim 157, wherein the spatial-encoding magnetic-field gradient pulses applied during each said data-acquisition step are configured so as to collect data, following each of at least one of the refocusing radio-frequency pulses, for one line in spatial-frequency space which is parallel to all other lines of data so collected, so as to collect the data using a magnetic resonance imaging technique selected from the group consisting of rapid acquisition with relaxation enhancement (RARE), fast spin echo (FSE), and turbo spin echo (TSE or TurboSE). .Iaddend.

.Iadd.221. The apparatus of claim 157, wherein the spatial-encoding magnetic-field gradient pulses applied during each said data-acquisition step are configured so as to collect data, following each of at least one of the refocusing radio-frequency pulses, for two or more lines in spatial-frequency space which are parallel to all other lines of data so collected, so as to collect the data using a magnetic resonance imaging technique selected from the group consisting of gradient and spin echo (GRASE) and turbo gradient spin echo (TGSE or TurboGSE). .Iaddend.

.Iadd.222. The apparatus of claim 157, wherein the spatial-encoding magnetic-field gradient pulses applied during each said data-acquisition step are configured so as to collect data, following each of at least one of the refocusing radio-frequency pulses, for one or more lines in spatial-frequency space, each of which pass through one of a single point in spatial-frequency space and a single line in spatial-frequency space, so as to collect the data using a magnetic resonance imaging technique selected from the group consisting of radial sampling and projection-reconstruction sampling. .Iaddend.

.Iadd.223. The apparatus of claim 222, wherein the single point in spatial-frequency space is substantially zero spatial frequency. .Iaddend.

.Iadd.224. The apparatus of claim 222, wherein the single line in spatial-frequency space includes substantially zero spatial frequency. .Iaddend.

.Iadd.225. The apparatus of 157, wherein the spatial-encoding magnetic-field gradient pulses applied during each said data-acquisition step are configured so as to collect data, following each of at least one of the refocusing radio-frequency pulses, along a spiral trajectory in spatial-frequency space, each trajectory of which is contained in one of two dimensions and three dimensions, and each trajectory of which passes through one of a single point in spatial-frequency space and a single line in spatial-frequency space. .Iaddend.

.Iadd.226. The apparatus of claim 225, wherein the single point in spatial-frequency space is substantially zero spatial frequency. .Iaddend.

.Iadd.227. The apparatus of claim 225, wherein the single line in spatial-frequency space includes substantially zero spatial frequency. .Iaddend.

.Iadd.228. The apparatus of claim 157, wherein the spatial-encoding magnetic-field gradient pulses applied during at least one of said data-acquisition steps are configured to collect sufficient spatial-frequency data to reconstruct at least two image sets, each of which exhibits contrast properties different from the other image sets. .Iaddend.

.Iadd.229. The apparatus of claim 228, wherein at least some of the spatial-frequency data collected during at least one of said data-acquisition steps is used in the reconstruction of more than one image set, whereby the data is shared between image sets. .Iaddend.

.Iadd.230. The apparatus of claim 157, wherein the spatial-encoding magnetic-field gradient pulses applied during at least one of said data-acquisition steps are configured so that, for the echo following at least one of the refocusing radio-frequency pulses, at least one of the first moment, the second moment and the third moment corresponding to at least one of the spatial-encoding directions is approximately zero. .Iaddend.

.Iadd.231. The apparatus of claim 157, wherein the spatial-encoding magnetic-field gradient pulses applied during at least one of said data-acquisition steps are configured so that, following at least one of the refocusing radio-frequency pulses, the zeroth moment measured over the time period between said refocusing radio-frequency pulse and the immediately consecutive refocusing radio-frequency pulse is approximately zero for at least one of the spatial-encoding directions. .Iaddend.

.Iadd.232. The apparatus of claim 157, wherein during all said data-acquisition steps the duration of all data-sampling periods are equal. .Iaddend.

.Iadd.233. The apparatus of claim 157, wherein during at least one of said data-acquisition steps at least one of the data-sampling periods has a duration that differs from the duration of at least one other data-sampling period. .Iaddend.

.Iadd.234. The apparatus of claim 157, wherein the spatial-encoding magnetic-field gradient pulses applied during said data-acquisition steps are configured so that the extent of spatial-frequency space sampled along at least one of the spatial-encoding directions is not symmetric with respect to zero spatial frequency, whereby a larger extent of spatial-frequency space is sampled to one side of zero spatial frequency as compared to the opposite side of zero spatial frequency. .Iaddend.

.Iadd.235. The apparatus of claim 234 wherein said spatial-frequency data is reconstructed using a partial-Fourier reconstruction algorithm. .Iaddend.

.Iadd.236. The apparatus of claim 157, wherein during at least one of said data-acquisition steps the temporal order in which spatial-frequency data is collected for at least one of the spatial-encoding directions is based on achieving at least one of selected contrast properties in the image and selected properties of the corresponding point spread function. .Iaddend.

.Iadd.237. The apparatus of claim 157, wherein during at least one of said data-acquisition steps the temporal order in which spatial-frequency data is collected is different from that for at least one other data-acquisition step. .Iaddend.

.Iadd.238. The apparatus of claim 157, wherein during at least one of said data-acquisition steps the extent of spatial-frequency data that is collected is different from that for at least one other data-acquisition step. .Iaddend.

.Iadd.239. The apparatus of claim 157, wherein during at least one of said data-acquisition steps spatial encoding of the radio-frequency magnetic resonance signal that follows at least one of the refocusing radio-frequency pulses is performed using only phase encoding so that said signal is received by the radio-frequency transceiver in the absence of any applied magnetic-field gradient pulses and hence contains chemical-shift information. .Iaddend.

.Iadd.240. The apparatus of claim 157, wherein at least one navigator radio-frequency pulse is incorporated into the pulse sequence for the purpose of determining the displacement of a portion of the object. .Iaddend.

.Iadd.241. The apparatus of claim 157, wherein said flip angles and phase angles for said refocusing radio-frequency pulses are, in addition, selected to increase the number of echoes in at least one spin-echo train compared to the number which would be achieved by using said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence. .Iaddend.

.Iadd.242. The apparatus of claim 159, wherein said flip angles for said refocusing radio-frequency pulses are also selected to vary among pulses to yield a signal evolution for the associated train of spin echoes for at least one additional substance of interest in said object, with corresponding T1 and T2 relaxation times and spin density of interest, and wherein said signal evolutions corresponding to said substance in apparatus of claim 159 and said additional substance result in T2-weighted contrast in the corresponding image(s) that is substantially the same as T2-weighted contrast that would be provided by imaging said object by using a turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence that has constant flip angles, with values of 180 degrees, for the refocusing radio-frequency pulses, and that has an effective echo time typical for T2-weighted clinical magnetic resonance imaging. .Iaddend.

.Iadd.243. The apparatus of claim 242, wherein the duration of the spin-echo trains for said signal evolutions for said substances is at least twice the duration of the spin-echo train for said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence and an effective echo time corresponding to said spin-echo trains for said signal evolutions for said substances is at least twice said effective echo time for said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence. .Iaddend.

.Iadd.244. The apparatus of claim 242, wherein the duration of the spin-echo trains for said signal evolutions for said substances is greater than approximately four times the T2 relaxation time for at least one of said substances. .Iaddend.

.Iadd.245. The apparatus of claim 242, wherein an effective echo time corresponding to said spin-echo trains for said signal evolutions for said substances is greater than approximately two times the T2 relaxation time for at least one of said substances. .Iaddend.

.Iadd.246. The apparatus of claim 159, wherein said flip angles and phase angles for the refocusing radio-frequency pulses are calculated using an appropriate analytical or computer-based algorithm, either prior to or substantially simultaneous with the execution of the pulse sequence. .Iaddend.

.Iadd.247. The apparatus of claim 159, wherein a contrast preparation comprising generating at least one of at least one radio-frequency pulse, at least one magnetic-field gradient pulse, and at least one time delay, whereby said contrast preparation encodes the magnetization with at least one desired image contrast, immediately precedes at least one of said excitation radio-frequency pulses. .Iaddend.

.Iadd.248. The apparatus of claim 159, wherein a three-dimensional volume of spatial-frequency space is sampled. .Iaddend.

.Iadd.249. The apparatus of claim 159, wherein at least one said data-acquisition step is initiated by a trigger signal to synchronize the pulse sequence with at least one of at least one external temporal event and at least one internal temporal event. .Iaddend.

.Iadd.250. The apparatus of claim 159, wherein the spatial-encoding magnetic-field gradient pulses applied during each said data-acquisition step are configured so as to collect data, following each of at least one of the refocusing radio-frequency pulses, for one line in spatial-frequency space which is parallel to all other lines of data so collected, so as to collect the data using a magnetic resonance imaging technique selected from the group consisting of rapid acquisition with relaxation enhancement (RARE), fast spin echo (FSE), and turbo spin echo (TSE or TurboSE). .Iaddend.

.Iadd.251. The apparatus of claim 159, wherein said flip angles for said refocusing radio-frequency pulses reach, at 50% of the total number of echoes in said train of spin echoes, a value approximately midway between said initial flip angle and the lowest flip angle. .Iaddend.

.Iadd.252. The apparatus of claim 161, wherein at least one of said signal amplitude decreases within the first approximately 15% of the total number of echoes and said signal amplitude decreases to a value that is no more than approximately one-half of the initial value for said signal evolution. .Iaddend.

.Iadd.253. The apparatus of claim 161, wherein said signal amplitude decreases within the first approximately 15% of the total number of echoes and said signal amplitude decreases to a value that is no more than approximately one-half of the initial value for said signal evolution. .Iaddend.

.Iadd.254. The apparatus of claim 182, wherein at least one of said effective echo time corresponding to said spin-echo trains for said signal evolutions for said substances is at least on the order of 300 milliseconds and said duration of the spin-echo trains for said signal evolutions for said substances is at least on the order of 600 milliseconds. .Iaddend.

.Iadd.255. The apparatus of claim 254, wherein said effective echo time for said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence has a value typical for T2-weighted clinical magnetic resonance imaging. .Iaddend.

.Iadd.256. The apparatus of claim 255, wherein a three-dimensional volume of spatial-frequency space is sampled. .Iaddend.

.Iadd.257. The apparatus of claim 256, wherein at least one of said duration of the spin-echo train for said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence is less than 300 milliseconds and said effective echo time for said turbo-spin-echo or fast-spin-echo spin-echo-train pulse sequence has a value typical for T2-weighted clinical magnetic resonance imaging of the brain. .Iaddend.

.Iadd.258. The apparatus of claim 257, wherein said angles, selected to vary for said refocusing radio-frequency pulses, reduce power deposition by at least 30% compared to power deposition that would be achieved by using constant flip angles, with values of 180 degrees, for the refocusing radio-frequency pulses. .Iaddend.

.Iadd.259. The apparatus of claim 258, wherein the number of refocusing radio-frequency pulses following at least one said excitation radio-frequency pulse is greater than 50. .Iaddend.

.Iadd.260. The apparatus of claim 259, wherein said flip angles and phase angles for the refocusing radio-frequency pulses are calculated using an appropriate analytical or computer-based algorithm, either prior to or substantially simultaneous with the execution of the pulse sequence. .Iaddend.

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