Magnetic resonance imaging apparatus
A magnetic resonance imaging apparatus according to the present embodiment includes sequence control circuitry and processing circuitry. The sequence control circuitry controls execution of a pulse sequence which includes a first segment and a second segment being provided prior to the first segment. The first segment is where signal acquisition is performed. The second segment is where longitudinal magnetization and transverse magnetization are reduced by applying a plurality of RF magnetic field pulses while changing a magnitude and/or a phase thereof and a plurality of spoiler gradient field pulses.
1. A magnetic resonance imaging apparatus comprising:
sequence control circuitry configured to control execution of a pulse sequence which includes a first segment and a second segment being provided prior to the first segment, the first segment being where signal acquisition is performed, the second segment being where an orientation of each proton within an imaging area being three-dimensionally dispersed and macroscopic longitudinal magnetization and transverse magnetization are reduced to substantially zero by applying a plurality of RF magnetic field pulses while changing a magnitude and/or a phase thereof and a plurality of spoiler gradient field pulses; and
processing circuitry configured to generate an image based on signals acquired by the pulse sequence.
2. The magnetic resonance imaging apparatus according to claim 1 , wherein the pulse sequence includes the second segment prior to the first segment for each phase encode line.
3. The magnetic resonance imaging apparatus according to claim 1 , wherein the sequence control circuitry applies the plurality of RF magnetic field pulses while randomly changing the magnitude and the phase thereof in the second segment.
4. The magnetic resonance imaging apparatus according to claim 1 , wherein the sequence control circuitry applies the RF magnetic field pulses and the spoiler gradient field pulses alternately without any other pulses being added in-between in the second segment.
5. The magnetic resonance imaging apparatus according to claim 1 , wherein the second segment is provided to set the longitudinal magnetization and the transverse magnetization to be approximately zero.
6. The magnetic resonance imaging apparatus according to claim 1 , wherein the sequence control circuitry executes a pulse sequence for MRF in the first segment.
7. The magnetic resonance imaging apparatus according to claim 6 , further comprising storage circuitry configured to store a dictionary in which a plurality of quantitative values are respectively associated with a plurality of predictive signal value waveforms obtained by simulation performed based on each of the plurality of quantitative values,
wherein the processing circuitry is configured to generate an image relating to the quantitative values by performing matching between a signal value waveform based on MR signals acquired by the pulse sequence for the MRF and the dictionary.
8. The magnetic resonance imaging apparatus according to claim 7 , wherein the plurality of predictive signal value waveforms are obtained by simulation based on a condition where an initial value of longitudinal magnetization and transverse magnetization is zero.
9. The magnetic resonance imaging apparatus according to claim 1 , wherein the sequence control circuitry applies the plurality of RF magnetic field pulses while changing the magnitude to gradually increase from zero from a starting point of the second segment to a predetermined point of the first segment.
10. The magnetic resonance imaging apparatus according to claim 1 , wherein the second segment is provided after application of a navigator echo, and the first segment is provided subsequent to the second segment.