MAGNETIC RESONANCE IMAGING APPARATUS AND METHOD

• US 20160299208A1
• Filed: 04/11/2016
• Published: 10/13/2016
• Est. Priority Date: 04/13/2015
• Status: Active Grant

• Current Assignee: Toshiba Medical Systems Corporation (Canon Inc.)
• Original Assignee: Toshiba Medical Systems Corporation (Canon Inc.), Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Kusahara, Hiroshi, SHIGETA, Takashi, Kassai, Yoshimori, Machii, Yutaka
• Granted Patent: US 10,295,641 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01R 33/5616 using gradient refocusing, e.g. EPI
• CPC Class Codes: G01R 33/56308 Characterization of motion or flow; Dynamic imaging
• CPC Class Codes: G01R 33/56554 caused by acquiring plural, differently encoded echo signals after one RF excitation, e.g. correction for readout gradients of alternating polarity in EPI

Abstract

A magnetic resonance imaging apparatus according to one embodiment includes a sequence controller, a correction map generator, an image generator, and a corrector. The sequence controller executes first data acquisition to acquire data for a phase correction map, and second data acquisition to acquire data of a cluster of images corresponding to a plurality of time phases. The correction map generator generates the phase correction map by using echo signals acquired through the first data acquisition. The image generator generates the cluster of images corresponding to the time phases by using echo signals acquired through the second data acquisition. The corrector corrects a phase of each image included in the cluster of images, based on the phase correction map and changes in phase of echo signals that occur between time phases.

Claims

1. A magnetic resonance imaging apparatus comprising processing circuitry configured to:

execute first data acquisition to acquire data for a phase correction map, and second data acquisition to acquire data for a cluster of images corresponding to a plurality of timephases;

generate the phase correction map by using at least one echo signal acquired through the first data acquisition;

generate the cluster of images corresponding the time phases by using echo signals acquired through the second data acquisition; and

based on the phase correction map and changes in phase of echo signals that occur between time phases, correct phases of the respective images included in the cluster of images.

2. The magnetic resonance imaging apparatus according to claim 1, wherein, based on the phase correction map and changes in phase of echo signals that occur between time phases, the processing circuitry corrects the phases of the respective images included in the cluster of images, the changes in phase having been obtained by using the echo signals acquired through the second data acquisition.

3. The magnetic resonance imaging apparatus according to claim 1, wherein the processing circuitry:

in the second data acquisition, acquires additional echo signals each time k-space data corresponding to one time phase is acquired; and

by using the additional echo signals acquired in the respective time phases, obtains the change in phase of echo signals that occur between time phases.

4. The magnetic resonance imaging apparatus according to claim 3, wherein, in the second data acquisition, the processing circuitry acquires the additional echo signals with a readout gradient magnetic field applied and with no phase-encoding gradient magnetic field applied.

5. The magnetic resonance imaging apparatus according to claim 3, wherein, when acquiring echo signals to be filled in the k-space data while polarity inversion of a readout gradient magnetic field is caused to occur, the processing circuitry acquires as the additional echo signals at least two echo signals under different polarities of the readout gradient magnetic field.

6. The magnetic resonance imaging apparatus according to claim 1, wherein the processing circuitry:

executes the first data acquisition at a time point before the time phases; and

based on the changes in phase of echo signals that occur between the time phases, corrects the phase correction map with respect to each of the time phases, and corrects changes in phase between the images by using the corrected phase correction map.

7. The magnetic resonance imaging apparatus according to claim 6, wherein the processing circuitry:

acquires echo signals in such a manner that, among the echo signals acquired through the second data acquisition, at least one echo signal acquired at the beginning of each of the time phases is acquired with readout gradient magnetic field applied and with no phase-encoding gradient magnetic field applied; and

based on changes in phase of echo signals each being the at least one echo signal, corrects changes in phase of the phase correction map in the readout direction for the respective time phases.

8. The magnetic resonance imaging apparatus according to claim 6, wherein, based on changes in center frequency of echo signals acquired during an effective echo time (TE) among the echo signals acquired through the second data acquisition, the processing circuitry corrects the phase correction map with respect to each of the time phases.

9. The magnetic resonance imaging apparatus according to claim 6, wherein the processing circuitry:

executes the second data acquisition for each of a plurality of adjacent slices with a readout gradient magnetic field and a phase-encoding gradient magnetic field both applied;

based on echo signals regarding at least one slice of the slices, generates a phase correction map for each of the time phases; and

based on changes in phase in the phase correction map generated with respect to the respective time phases, corrects changes in the phase correction map in phase in the readout direction and in the phase-encoding direction with respect to each of the time phases.

10. The magnetic resonance imaging apparatus according to claim 1, wherein the processing circuitry:

executes the first data acquisition with respect to each of the time phases;

based on echo signals acquired through the first data acquisition, generates phase correction maps with respect to the respective time phases; and

by using the phase correction map generated with respect to the respective time phases, corrects the changes in phase between the images.

11. The magnetic resonance imaging apparatus according to claim 1, wherein the processing circuitry:

executes the first data acquisition at a first time point before the time phases and at a second time point after time phases;

generates a first phase correction map based on echo signals acquired at the first time point, and generates a second phase correction map based on echo signals acquired at the second time point; and

based on a change in phase between the first phase correction map and the second phase correction map, corrects changes in phase between the images.

12. A magnetic resonance imaging method comprising:

executing first data acquisition to acquire data for a phase correction map, and second data acquisition to acquire data for a cluster of image corresponding to a plurality time phases;

generating the phase correction map by using at least one echo signal acquired through the first data acquisition;

generating the cluster of images corresponding to the time phases by using echo signals acquired through the second data acquisition; and

based on the phase correction map and changes in phase of echo signals that occur between time phases, correcting phases of the respective images included in the cluster of images.