MAGNETIC RESONANCE IMAGING APPARATUS AND SYNCHRONOUS MEASUREMENT METHOD

• US 20120141007A1
• Filed: 08/02/2010
• Published: 06/07/2012
• Est. Priority Date: 08/12/2009
• Status: Active Grant

• Current Assignee: FUJIFILM Healthcare Corp. (Fujifilm Holdings Corporation)
• Original Assignee: Shenzhen Trony Science & Technology Development Co., Ltd.
• Inventors: Takizawa, Masahiro, Takahashi, Tetsuhiko, Goto, Tomohiro, Abe, Takayuki
• Granted Patent: US 8,855,392 B2
• Time in Patent Office: Days
• US Class Current: 382/131
• CPC Class Codes: A61B 5/055 involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]
• CPC Class Codes: A61B 5/7207 of noise induced by motion artifacts
• CPC Class Codes: A61B 5/7285 for synchronising or triggering a physiological measurement or image acquisition with a physiological event or waveform, e.g. an ECG signal A61B6/5205, A61B6/541, A61B8/5207, A61B8/543 take precedence
• CPC Class Codes: G01R 33/482 using a Cartesian trajectory
• CPC Class Codes: G01R 33/4824 using a non-Cartesian trajectory
• CPC Class Codes: G01R 33/5617 using RF refocusing, e.g. RARE
• CPC Class Codes: G01R 33/5673 Gating or triggering based on a physiological signal other than an MR signal, e.g. ECG gating or motion monitoring using optical systems for monitoring the motion of a fiducial marker

Abstract

An image with a desired contrast is obtained while suppressing body motion artifacts caused by both random motion and periodic motion of an object. In order to do so, an imaging sequence using a non-Cartesian sampling method is executed so as to synchronize with a biological signal only at the start time and a repetition time (TR), which is an execution interval between shots within the imaging sequence, is maintained. In addition, a time difference between a delay time and a start time of each shot is calculated, and a shot with a predetermined time difference or more is executed again after the TR time.

Claims

1. A magnetic resonance imaging apparatus comprising:

an imaging control unit that repeats a shot using an imaging sequence, in which one or more echo signals corresponding to a partial region of a measurement space are collected, at predetermined repetition intervals on the basis of a non-Cartesian sampling method while changing the partial region; and

a biological signal receiving unit that receives a periodic biological signal of an object,

wherein the imaging control unit starts the imaging sequence after a predetermined delay after the biological signal receiving unit receives the biological signal and repeats the imaging sequence while maintaining the repetition interval.

2. The magnetic resonance imaging apparatus according to claim 1,

wherein the biological signal receiving unit includes a biological signal receiving time storage unit which stores a corresponding receiving time as a biological signal receiving time whenever a biological signal is received while the imaging control unit is executing the imaging sequence, and

the imaging control unit includes a time difference calculating unit which calculates a minimum value of a time between a start time of a corresponding shot and a delay time after elapse of the delay time from each biological signal receiving time, as a time difference, in each shot and an adoption determining unit which determines that an echo signal collected in a corresponding shot is not adopted when the time difference exceeds a threshold value set in advance, and executes again the shot determined not to be adopted by the adoption determining unit after the repetition time elapses from the start of the shot.

3. The magnetic resonance imaging apparatus according to claim 1,

wherein the biological signal receiving unit includes a biological signal receiving time storage unit which stores a corresponding receiving time as a biological signal receiving time whenever a biological signal is received while the imaging control unit is executing the imaging sequence, and

the imaging control unit includes a time difference calculating unit which calculates a minimum value of a time between a start time of a corresponding shot and a delay time after elapse of the delay time from each biological signal receiving time, as a time difference, in each shot and a signal strength correcting unit which acquires a corrected echo signal by multiplying an echo signal collected in the shot by a weighting coefficient which decreases as the time difference increases.

4. The magnetic resonance imaging apparatus according to claim 2,

wherein the imaging control unit further includes a signal strength correcting unit, which acquires a corrected echo signal by multiplying an echo signal collected in the shot by a weighting coefficient which decreases as the time difference increases, and executes again the shot determined not to be adopted by the adoption determining unit after the repetition time elapses from the start of the shot.

5. The magnetic resonance imaging apparatus according to claim 3,

wherein the imaging control unit further includes a second signal strength correcting unit which multiplies the corrected echo signal by a second weighting coefficient which increases as a distance from an origin in the measurement space of the echo signal increases.

6. The magnetic resonance imaging apparatus according to claim 1,

wherein the imaging sequence is for measuring a three-dimensional measurement space including a slice encoding gradient magnetic field,

the biological signal receiving unit includes a biological signal receiving time storage unit which stores a corresponding receiving time as a biological signal receiving time whenever a biological signal is received while the imaging control unit is executing the imaging sequence, and

the imaging control unit further includes a second time difference calculating unit which calculates a time between a time after elapse of the delay time from a latest biological signal receiving time and a start time of a corresponding shot, as a second time difference, in each shot and an amplitude control unit which determines an amplitude of the slice gradient magnetic field pulse such that an echo signal collected in a shot with the smaller second time difference is disposed at a position closer to a central portion of the measurement space in a slice direction.

7. The magnetic resonance imaging apparatus according to claim 2,

wherein the imaging sequence is for measuring a three-dimensional measurement space including a slice encoding gradient magnetic field, and

the imaging control unit further includes a second time difference calculating unit which calculates a time between a time after elapse of the delay time from a latest biological signal receiving time and a start time of a corresponding shot, as a second time difference, in each shot and an amplitude control unit which determines an amplitude of the slice gradient magnetic field pulse such that an echo signal collected in a shot with the smaller second time difference is disposed at a position closer to a central portion of the measurement space in a slice direction.

8. The magnetic resonance imaging apparatus according to claim 1,

wherein the partial region is a blade including a plurality of trajectories which are parallel to each other and each of which corresponds to one echo signal, and

the imaging control unit measures one or more echo signals corresponding to one blade by one imaging sequence and repeats the imaging sequence while changing an angle of the blade with respect to a predetermined axis of the measurement space.

9. The magnetic resonance imaging apparatus according to claim 8,

wherein the imaging sequence is based on an FSE sequence.

10. A synchronous measurement method in a magnetic resonance imaging apparatus comprising:

an imaging step of repeating an imaging sequence, in which one or more echo signals corresponding to a partial region of a measurement space are collected, at predetermined repetition intervals on the basis of a non-Cartesian sampling method while changing the partial region; and

a biological signal receiving step of receiving a periodic biological signal of an object,

wherein in the imaging step, the imaging sequence starts after a predetermined delay time after the biological signal is received and the imaging sequence is repeated while maintaining the repetition interval.