Method and apparatus for spin-echo-train MR imaging using prescribed signal evolutions
DC CAFCFirst 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 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, 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.
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Abstract
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.
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Citations
260 Claims
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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:
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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, 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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 42, 47, 48, 49, 50)
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40. A magnetic resonance imaging apparatus generating a spin echo pulse sequence in order configured to operate the apparatus inthat is configured 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, the apparatus comprising:
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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, 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. - View Dependent Claims (44, 54, 55, 56, 57)
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41. A magnetic resonance imaging apparatus generating a spin echo pulse sequence in order configured to operate the apparatus in that is configured 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, the apparatus comprising:
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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, 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. - View Dependent Claims (45, 61, 62, 63, 64)
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43. A computer program provided on a non-transitory 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:
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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-acquistion 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, 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. - View Dependent Claims (46, 68, 69, 70, 71)
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51. A method for generating a spin echo pulse sequence for operating a magnetic resonance imaging apparatus for imaging an object, said method comprising:
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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. - View Dependent Claims (52)
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53. A method for generating a spin echo pulse sequence for operating a magnetic resonance imaging apparatus for imaging an object, said method comprising:
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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.
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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:
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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. - View Dependent Claims (59)
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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:
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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.
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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:
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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. - View Dependent Claims (66)
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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:
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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.
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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:
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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. - View Dependent Claims (73)
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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:
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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.
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75. A method for generating a spin-echo pulse sequence for operating a magnetic resonance imaging apparatus for imaging an object, said method comprising:
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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. - View Dependent Claims (76, 77, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 169, 170, 171, 172, 173, 174, 175)
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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.
- 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.
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140. A method for generating a spin-echo pulse sequence for operating a magnetic resonance imaging apparatus for imaging an object, said method comprising:
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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.
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141. A method for generating a spin-echo pulse sequence for operating a magnetic resonance imaging apparatus for imaging an object, said method comprising:
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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. - View Dependent Claims (142, 143, 144, 145, 146, 147, 148, 149, 150, 151)
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152. A method for generating a spin-echo pulse sequence for operating a magnetic resonance imaging apparatus for imaging an object, said method comprising:
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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.
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153. A method for generating a spin-echo pulse sequence for operating a magnetic resonance imaging apparatus for imaging an object, said method comprising:
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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. - View Dependent Claims (154, 155)
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156. A method for generating a spin-echo pulse sequence for operating a magnetic resonance imaging apparatus for imaging an object, said method comprising:
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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.
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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:
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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. - View Dependent Claims (178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241, 254, 255, 256, 257, 258, 259, 260)
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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:
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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.
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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:
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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. - View Dependent Claims (242, 243, 244, 245, 246, 247, 248, 249, 250, 251)
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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:
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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.
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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:
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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. - View Dependent Claims (252, 253)
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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:
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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.
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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:
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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.
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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:
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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.
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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:
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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.
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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:
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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.
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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:
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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.
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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:
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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.
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176. A method for generating a spin-echo pulse sequence for operating a magnetic resonance imaging apparatus for imaging an object, said method comprising:
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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.
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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:
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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.
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- 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.
Specification