MRI apparatus and a method of reducing imaging time

1. An MRI apparatus, comprising:

a static magnetic field magnet configured to generate a static magnetic field;

a gradient coil configured to generate a gradient magnetic field;

a transmission and reception coil configured to transmit an RF signal and receive a magnetic resonance signal; and

processing circuitry configured to

set an imaging condition of a diagnostic scan,

determine whether or not a prescan is skippable or reducible based on the set imaging condition of the diagnostic scan, wherein the prescan is performed to obtain data for calculating a correction value that corrects a phase error of the diagnostic scan, and the diagnostic scan is performed to obtain a diagnostic image after the prescan, and

execute the diagnostic scan without the prescan or with the reduced prescan, when it is determined that the prescan is skippable or reducible based on the imaging condition of the diagnostic scan.

2. The MRI apparatus according to claim 1 , wherein

the processing circuitry is further configured to determine whether the prescan is skippable or reducible, in accordance with a similarity between the imaging condition of the diagnostic scan and a specified imaging condition.

3. The MRI apparatus according to claim 2 , wherein

the processing circuitry is further configured to determine whether the prescan is skippable or reducible in accordance with at least one of a similarity between a center of the diagnostic scan and a magnetic field center, a similarity in a parameter relating to resolution, and a similarity relating to a prepulse.

4. The MRI apparatus according to claim 1 , further comprising

a memory that stores a correction value corresponding to a specified imaging condition, wherein

the processing circuitry is further configured to use the imaging condition of the diagnostic scan to refer to the correction value corresponding to the imaging condition in the memory and determine whether the prescan is skippable in accordance with a size of the correction value.

5. An MRI apparatus, comprising:

a static magnetic field magnet configured to generate a static magnetic field;

a gradient coil configured to generate a gradient magnetic field;

a transmission and reception coil configured to transmit an RF signal and receive a magnetic resonance signal;

processing circuitry; and

a memory that stores, for each type of correction value that corrects the phase error, a correction value acquired by a first prescan performed at a time of installation of the MRI apparatus, wherein

the processing circuitry is configured to

determine whether a second prescan, which is performed prior to a diagnostic scan for obtaining a diagnostic image, is skippable or reducible based on the stored correction value, and

execute the diagnostic scan without the second prescan or with the reduced second prescan, when it is determined that the second prescan is skippable or reducible based on the stored correction value.

6. The MRI apparatus according to claim 5 , wherein

the processing circuitry is further configured to determine whether the prescan is skippable or reducible in accordance with a similarity between an imaging condition of the diagnostic scan and a specified imaging condition.

7. The MRI apparatus according to claim 6 , wherein

the processing circuitry is further configured to determine whether the prescan is skippable or reducible in accordance with at least one of a similarity between a center of the diagnostic scan and a magnetic field center, a similarity in a parameter relating to resolution, and a similarity relating to a prepulse.

8. The MRI apparatus according to claim 5 , wherein

the memory stores a changed imaging condition that is changed based on the correction value, together with the correction value, and

the processing circuitry is further configured to determine whether the prescan is skippable or reducible based on the correction value corresponding to the changed imaging condition, when executing a scan including at least the diagnostic scan using the changed imaging condition.

9. The MRI apparatus according to claim 1 , wherein the processing circuitry is further configured to:

when the prescan is skipped, execute the diagnostic scan corrected with all the correction values acquired before the prescan; and

when the prescan is reduced, execute the diagnostic scan corrected with the correction values acquired in the reduced prescan and with part of the correction values acquired the before the prescan.

10. The MRI apparatus according to claim 5 , wherein the processing circuitry is further configured to:

when the prescan is skipped, execute the diagnostic scan corrected with all the correction values acquired before the prescan; and

when the prescan is reduced, execute the diagnostic scan corrected with the correction values acquired in the reduced prescan and with part of the correction values acquired the before the prescan.

11. The MRI apparatus according to claim 5 , wherein the types of correction values include:

a correction value that corrects a zero-order phase error in a readout direction;

a correction value that corrects a first-order phase error in a slice direction; and

a correction value that corrects a first-order phase error component in the readout direction.

12. The MRI apparatus according to claim 1 , wherein

the processing circuitry is further configured to execute the diagnostic scan with a reduced number of slices, when the prescan is reduced.

13. The MRI apparatus according to claim 5 , wherein

the processing circuitry is further configured to execute the diagnostic scan with a reduced number of slices, when the prescan is reduced.