Magnetic resonance imaging method for acquiring flux-compensated, T2 -w

Claim 1

A method for obtaining an image in a nuclear magnetic resonance imaging apparatus comprising the steps of: (a) disposing an examination subject in a fundamental static magnetic field; (b) subjecting said examination subject in said fundamental magnetic field to a plurality of radio frequency pulses at a pulse repetition interval T r which is less than the T 2 relaxation time, said radio frequency pulses exciting nuclear spins in said examination subject and thereby generating magnetic resonance signals; (c) generating a magnetic gradient field pulse in the y-direction before and after each radio frequency pulse, each gradient pulse in the y-direction being graphically representable as a curve with an area beneath said curve, and the respective gradient pulses in the y-direction before and after a radio frequency pulse having respective areas associated therewith which sum to zero; (d) generating a magnetic gradient field pulse in the x-direction chronologically symmetrically between two of said radio frequency pulses and preceding and following said gradient pulse in the x-direction with inverted magnetic field gradient pulses in the x-direction having a polarity opposite to said gradient in the x-direction, said gradient pulse and said inverted gradient pulses in the x-direction in combination having a time integral equal to zero; (e) reading out said magnetic resonance signals during said gradient in the x-direction; (f) repeating steps (b), (c), (d) and (e) a first n times with the radio frequency pulses in each repetition having the same phase relation and varying the time integral of the gradient pulses in the y-direction in a chronologically equidistant step for each repetition, thereby obtaining a read-out magnetic resonance signal for each of the first n repetitions; (g) repeating steps (b), (c), (d) and (e) a second n times alternating the phase relation of the radio frequency pulses by 180° from repetition-to-repetition and varying the time integral of the gradients in the y-direction in a chronologically equidistant step for each repetition, thereby obtaining a read-out magnetic resonance signal for each of the second n repetitions; (h) adding said magnetic resonance signals obtained in steps (f) and (g) to obtain a first data set; (i) subtracting said magnetic resonance signals obtained in steps (f) and (g) to obtain a second data set; and (j) reconstructing an image of said examination subject from said first and second data sets.

Claim 2

A method for obtaining an image in a nuclear magnetic resonance imaging apparatus comprising the steps of: (a) disposing an examination subject in a fundamental static magnetic field; (b) subjecting said examination subject in said fundamental magnetic field to a plurality of radio frequency pulses at a pulse repetition interval T r which is less than the T 2 relaxation time, said radio frequency pulses exciting nuclear spins in said examination subject and thereby generating magnetic resonance signals; (c) generating a magnetic gradient field pulse in the y-direction before and after each radio frequency pulse, each gradient pulse in the y-direction being graphically representable as a curve with an area beneath said curve, and the respective gradient pulses in the y-direction before and after a radio frequency pulse having respective areas associated therewith which sum to zero; (d) generating a magnetic gradient field pulse in the x-direction chronologically symmetrically between two of said radio frequency pulses and preceding and following said gradient pulse in the x-direction with inverted magnetic field gradient pulses in the x-direction having a polarity opposite to said gradient in the x-direction, said gradient pulse and said inverted gradient pulses in the x-direction in combination having a time integral equal to zero; (e) reading out said magnetic resonance signals during said gradient in the x-direction; (f) repeating steps (b), (c), (d) and (e) a first n times with the radio frequency pulses in each repetition having the same phase relation and varying the time integral of the gradient pulses in the y-direction in a chronologically equidistant step for each repetition, thereby obtaining a read-out magnetic resonance signal for each of the first n repetitions; (g) repeating steps (b), (c), (d) and (e) a second n times alternating the phase relation of the radio frequency pulses by 180° from repetition-to-repetition and varying the time integral of the gradients in the y-direction in a chronologically equidistant step for each repetition, thereby obtaining a read-out magnetic resonance signal for each of the second n repetitions; (h) adding said magnetic resonance signals obtained in steps (f) and (g) to obtain a first data set; (i) subtracting said magnetic resonance signals obtained in steps (f) and (g) to obtain a second data set; and (j) reconstructing an image of said examination subject from said first and second data sets.