Magnetic resonance imaging apparatus and method thereof

Patent metadata

Field	Value
Publication number	US-2016363643-A1
Application number	US-201615168913-A
Country	US
Kind code	A1
Filing date	May 31, 2016
Priority date	Jun 9, 2015
Publication date	Dec 15, 2016
Grant date	—

Abstract

A magnetic resonance imaging apparatus according to an embodiment includes a calculation unit, a collecting unit, and an execution unit. The calculation unit calculates, based on a pulse sequence used in data collection by fast spin echo method, a phase shift amount on at least one echo component included in each of a plurality of echo signals. The correcting unit corrects, based on the calculated phase shift amount, phases of refocusing pulses applied in the pulse sequence such that phases match at least one of between spin echo components, between stimulated echo components, and between a spin echo component and a stimulated echo component. The execution unit executes the pulse sequence in which the refocusing pulses of the corrected phases are applied.

First claim

What is claimed is:

1 . A magnetic resonance imaging apparatus comprising
a processing circuitry configured to: calculate, based on a pulse sequence used in data collection by fast spin echo method, a phase shift amount on at least one echo component included in each of a plurality of echo signals collected by the pulse sequence; correct, based on the calculated phase shift amount, phases of refocusing pulses applied in the pulse sequence such that phases match at least one of between spin echo components, between stimulated echo components, and between a spin echo component and a stimulated echo component; and execute the pulse sequence in which the refocusing pulses of the corrected phases are applied.

2 . The magnetic resonance imaging apparatus according to claim 1 , further comprising:
memory circuitry configured to store therein in advance a phase shift amount per a certain unit concerning an application condition of a gradient magnetic field, on a phase shift that arises by application of the gradient magnetic field, wherein the processing circuitry refers to the stored phase shift amount, and calculates the phase shift amount for each echo component based on the application condition of a gradient magnetic field applied in a pulse sequence used in the data collection.

3 . The magnetic resonance imaging apparatus according to claim 1 , wherein the processing circuitry holds, for each echo component, a relational expression that indicates relation of phase shift amount between time points at which each of the echo signals is generated, and calculates a phase shift amount for each echo component based on the relational expression.

4 . The magnetic resonance imaging apparatus according to claim 1 , wherein the processing circuitry further corrects a reception phase when the echo signals are sampled.

5 . The magnetic resonance imaging apparatus according to claim 1 , wherein the processing circuitry calculates, based on a phase shift amount of a spin echo component placed near a center of k-space out of calculated phase shift amounts, a correction amount for a phase of a refocusing pulse applied immediately before that spin echo component and, by using in common the calculated correction amount, corrects the phase of each of a plurality of refocusing pulses applied in the pulse sequence.

6 . The magnetic resonance imaging apparatus according to claim 1 , wherein the processing circuitry:
calculates, based on a pulse sequence used in a pre-scan for phase correction that is executed before a main scan, a phase shift amount on at least one echo component included in each of a plurality of echo signals collected by the pulse sequence; corrects, based on the calculated phase shift amount, phases of refocusing pulses applied in the pulse sequence used in the pre-scan; and executes the pre-scan by using the pulse sequence in which the refocusing pulses of the corrected phases are applied, and then executes the main scan by using the pulse sequence to which the phase correction has been applied based on data collected by the pre-scan.

7 . The magnetic resonance imaging apparatus according to claim 1 , wherein the processing circuitry calculates the phase shift amount by calculating a phase shift amount caused by at least one of a Maxwell term and an eddy current component that are generated by a gradient magnetic field applied in the pulse sequence.

8 . The magnetic resonance imaging apparatus according to claim 1 , wherein the processing circuitry calculates the phase shift amount by simulation calculation in which phase variation of an echo component included in an echo signal is modeled.

9 . The magnetic resonance imaging apparatus according to claim 8 , wherein the processing circuitry calculates the phase shift amount by the modeling in which a spin echo component and a stimulated echo component included in an echo signal are distinguished and time points at which the echo signals are generated are distinguished.

10 . The magnetic resonance imaging apparatus according to claim 1 , wherein the processing circuitry calculates the phase shift amount without executing a pre-scan.

11 . A magnetic resonance imaging apparatus comprising:
processing circuitry configured to: calculate a phase shift amount of echo signals collected by fast spin echo method by simulation calculation in which phase variation of an echo component included in the echo signal is modeled; correct, based on the calculated phase shift amount, phases of refocusing pulses applied in a pulse sequence such that the phases match at each time point at which the respective echo signals are generated; and executes the pulse sequence in which the refocusing pulses of the corrected phases are applied.

12 . The magnetic resonance imaging apparatus according to claim 11 , wherein the processing circuitry calculates the phase shift amount by the modeling in which a spin echo component and a stimulated echo component included in an echo signal are distinguished and time points at which the echo signals are generated are distinguished.

13 . The magnetic resonance imaging apparatus according to claim 11 , wherein the processing circuitry calculates the phase shift amount without executing a pre-scan.

14 . The magnetic resonance imaging apparatus according to claim 11 , further comprising:
memory circuitry configured to store therein in advance a phase shift amount per a certain unit concerning an application condition of a gradient magnetic field, on a phase shift that arises by application of the gradient magnetic field, wherein the processing circuitry refers to the stored phase shift amount and, based on the application condition of a gradient magnetic field applied when the echo signals are collected, calculates the phase shift amount by the simulation calculation.

15 . The magnetic resonance imaging apparatus according to claim 11 , wherein the processing circuitry holds a relational expression that indicates relation of phase shift amount between time points at which the echo signals are generated, and calculates the phase shift amount by the simulation calculation based on the relational expression.

16 . The magnetic resonance imaging apparatus according to claim 11 , wherein the processing circuitry further corrects a reception phase when the echo signals are sampled.

17 . The magnetic resonance imaging apparatus according to claim 11 , wherein the processing circuitry calculates, based on a phase shift amount of a spin echo component placed near a center of k-space out of calculated phase shift amounts, a correction amount for a phase of a refocusing pulse applied immediately before that spin echo component and, by using in common the calculated correction amount, corrects the phase of each of a plurality of refocusing pulses applied in the pulse sequence.

18 . The magnetic resonance imaging apparatus according to claim 11 , wherein the processing circuitry:
calculates, based on a pulse sequence used in a pre-scan for phase correction that is executed before a main scan, a phase shift amount of echo signals collected by the pulse sequence; corrects, based on the calculated phase shift amount, phases of refocusing pulses applied in the pulse sequence used in the pre-scan; and executes the pre-scan by using the pulse sequence in which the refocusing pulses of the corrected phases are applied, and then executes the main scan by using the pulse sequence to which the phase correction has been applied based on data collected by the pre-scan.

Assignees

• Toshiba Medical Sys Corp

Inventors

• Umeda Masaaki

Classifications

• G01R33/565 Primary

  Correction of image distortions, e.g. due to magnetic field inhomogeneities · CPC title

• G01R33/4828

  Resolving the MR signals of different chemical species, e.g. water-fat imaging · CPC title

• G01R33/4824

  using a non-Cartesian trajectory · CPC title

• G01R33/56581

  due to Maxwell fields, i.e. concomitant fields · CPC title

• G01R33/482

  using a Cartesian trajectory · CPC title