Method for rapid acquisition of spin resonance data for a spatially resolved investigation of an object

Claim 1

A method of rapid acquisition of spin resonance data for a space-resolved investigation of a region of an object which comprises atomic spins exhibiting a predetermined spin-lattice relaxation time T 1 , a predetermined spin-spin relaxation time T 2 and a predetermined effective spin-spin relaxation time T 2 *, said method comprising (a) positioning said region in a homogeneous magnetic field to align said spins into a predetermined direction, (b) applying a selective radio-frequency pulse (RF) to said region to tilt said spins by a predetermined flip angle out of said predetermined direction, (c) applying to said region at least a slice-selection magnetic field gradient (G-slice) in a first (slice) direction and an encoding magnetic field gradient (G-phase) in a second (phase) direction, (d) performing at least once the following series of steps after the termination of said radio frequency pulse: (aa) reversing the polarity of the slice selection gradient, (bb) maintaining the reversed slice selection gradient for a predetermined period of time to refocus dephased magnetization during radio frequency excitation, (cc) switching off the slice selection gradient before detection of a gradient echo (step e), (dd) applying a read gradient (G-read) of a predetermined polarity and a predetermined duration to said object region, (ee) reversing the polarity of said read gradient to produce a gradient echo signal, (ff) maintaining the read gradient of reversed polarity for a predetermined period of time; (e) detecting the gradient echo produced by the polarity reversal of the read gradient, (f) switching off the read gradient, said steps (b) to (f) comprising one partial experiment, (g) repeating a plurality n of times the steps (b) to (f), wherein (gg) a predetermined interval is allowed between the read gradient switching off time (step f) of a given partial experiment, and the application of the radio-frequency pulse (RF) of a subsequent partial experiment, said interval being essentially shorter than said spin-lattice relaxation time (T 1 ), (hh) no more than three magnetic field gradients are applied which are essentially normal to each other, (ii) each encoding gradient (G-phase and/or G-slice for three-dimensional measurements) is switched off before the detecting step (e), characterized in that (h) an additional slice gradient pulse (SP) is applied after the detecting step e) of a partial experiment and before the radio frequency pulse (RF) of the next following partial experiment, said additional slice gradient pulse (SP) having a predetermined amplitude-time integral, and (i) said amplitude-time integral of said additional slice gradient pulse (SP) is varied monotonically step by step in the course of said repeating of said partial experiments to partial experiment within at least a portion of a total experiment.

Claim 2

A method of rapid acquisition of spin resonance data for a space-resolved investigation of a region of an object which comprises atomic spins exhibiting a predetermined spin-lattice relaxation time T 1 , a predetermined spin-spin relaxation time T 2 and a predetermined effective spin-spin relaxation time T 2 *, said method comprising (a) positioning said region in a homogeneous magnetic field to align said spins into a predetermined direction, (b) applying a selective radio-frequency pulse (RF) to said region to tilt said spins by a predetermined flip angle out of said predetermined direction, (c) applying to said region at least a slice-selection magnetic field gradient (G-slice) in a first (slice) direction and an encoding magnetic field gradient (G-phase) in a second (phase) direction, (d) performing at least once the following series of steps after the termination of said radio frequency pulse: (aa) reversing the polarity of the slice selection gradient, (bb) maintaining the reversed slice selection gradient for a predetermined period of time to refocus dephased magnetization during radio frequency excitation, (cc) switching off the slice selection gradient before detection of a gradient echo (step e), (dd) applying a read gradient (G-read) of a predetermined polarity and a predetermined duration to said object region, (ee) reversing the polarity of said read gradient to produce a gradient echo signal, (ff) maintaining the read gradient of reversed polarity for a predetermined period of time; (e) detecting the gradient echo produced by the polarity reversal of the read gradient, (f) switching off the read gradient, said steps (b) to (f) comprising one partial experiment, (g) repeating a plurality n of times the steps (b) to (f), wherein (gg) a predetermined interval is allowed between the read gradient switching off time (step f) of a given partial experiment, and the application of the radio-frequency pulse (RF) of a subsequent partial experiment, said interval being essentially shorter than said spin-lattice relaxation time (T 1 ), (hh) no more than three magnetic field gradients are applied which are essentially normal to each other, (ii) each encoding gradient (G-phase and/or G-slice for three-dimensional measurements) is switched off before the detecting step (e), characterized in that (h) an additional slice gradient pulse (SP) is applied after the detecting step e) of a partial experiment and before the radio frequency pulse (RF) of the next following partial experiment, said additional slice gradient pulse (SP) having a predetermined amplitude-time integral, and (i) said amplitude-time integral of said additional slice gradient pulse (SP) is varied monotonically step by step in the course of said repeating of said partial experiments to partial experiment within at least a portion of a total experiment.

Claim 20

A method of rapid acquisition of spin resonance data according to a projection-reconstruction algorithm, for a space-resolved investigation of a region of an object which comprises atomic spins exhibiting a predetermined spin-lattice relaxation time T 1 , a predetermined spin-spin relaxation time T 2 and a predetermined effective spin-spin relaxation time T 2 *, said method comprising (a) positioning said region in a homogeneous magnetic field to align said spins into a predetermined direction, (b) applying a selective radio-frequency pulse (RF) to said region to tilt said spins by a predetermined flip angle out of said predetermined direction, (c) applying to said region magnetic field gradients in mutually essentially normal directions, said gradients including a slice selection gradient, (d) performing at least once the following series of steps after the termination of said radio frequency pulse: (aa) reversing the polarity of said slice selection gradient, (bb) maintaining the reversed slice selection gradient for a predetermined period of time to refocus dephased magnetization during rf excitation, (cc) switching off the slice selection gradient before detection of a gradient echo (step e), (dd) applying a first and a second read gradient (G-Read, G-Phase) of predetermined polarities and predetermined durations to said object region, (ee) reversing polarities of said read gradients to produce a gradient echo signal, (ff) maintaining the read gradients of reversed polarities for a predetermined period of time; (e) detecting the gradient echo produced by the polarity reversal of the read gradients, (f) switching off each read gradient, said steps (b) to (f) comprising one partial experiment, (g) repeating a plurality n of times the steps (b) to (f), wherein (gg) a predetermined interval is allowed between the read gradient switching off time (step f) of a given partial experiment, and the application of the radio-frequency pulse (RF) of the next following partial experiment, said interval being essentially shorter than said spin-lattice relaxation time (T 1 ), (hh) no more than three magnetic field gradients are applied which are essentially normal to each other, (ii) the amplitudes of said first and second read gradients are synchronously varied according to sine and cosine functions, respectively from partial experiment to partial experiment to rotate a resulting read gradient around said object region, and wherein an additional slice gradient pulse (SP) having a predetermined amplitude-time integral is applied after the detecting step (e) of a partial experiment and before the radio frequency pulse (RF) of the next following partial experiment, and the amplitude-time integral of the additional slice gradient pulse (SP) is varied monotonically step by step in the course of the repetitions of said partial experiments within at least a portion of a total experiment.

Claim 21

A method of rapid acquisition of spin resonance data according to a projection-reconstruction algorithm, for a space-resolved investigation of a region of an object which comprises atomic spins exhibiting a predetermined spin-lattice relaxation time T 1 , a predetermined spin-spin relaxation time T 2 and a predetermined effective spin-spin relaxation time T 2 *, said method comprising (a) positioning said region in a homogeneous magnetic field to align said spins into a predetermined direction, (b) applying a selective radio-frequency pulse (RF) to said region to tilt said spins by a predetermined flip angle out of said predetermined direction, (c) applying to said region magnetic field gradients in mutually essentially normal directions, said gradients including a slice selection gradient, (d) performing at least once the following series of steps after the termination of said radio frequency pulse: (aa) reversing the polarity of said slice selection gradient, (bb) maintaining the reversed slice selection gradient for a predetermined period of time to refocus dephased magnetization during rf excitation, (cc) switching off the slice selection gradient before detection of a gradient echo (step e), (dd) applying a first and a second read gradient (G-Read, G-Phase) of predetermined polarities and predetermined durations to said object region, (ee) reversing polarities of said read gradients to produce a gradient echo signal, (ff) maintaining the read gradients of reversed polarities for a predetermined period of time; (e) detecting the gradient echo produced by the polarity reversal of the read gradients, (f) switching off each read gradient, said steps (b) to (f) comprising one partial experiment, (g) repeating a plurality n of times the steps (b) to (f), wherein (gg) a predetermined interval is allowed between the read gradient switching off time (step f) of a given partial experiment, and the application of the radio-frequency pulse (RF) of the next following partial experiment, said interval being essentially shorter than said spin-lattice relaxation time (T 1 ), (hh) no more than three magnetic field gradients are applied which are essentially normal to each other, (ii) the amplitudes of said first and second read gradients are synchronously varied according to sine and cosine functions, respectively from partial experiment to partial experiment to rotate a resulting read gradient around said object region, and wherein an additional slice gradient pulse (SP) having a predetermined amplitude-time integral is applied after the detecting step (e) of a partial experiment and before the radio frequency pulse (RF) of the next following partial experiment, and the amplitude-time integral of the additional slice gradient pulse (SP) is varied monotonically step by step in the course of the repetitions of said partial experiments within at least a portion of a total experiment.