Magnetic resonance imaging apparatus and image generation method

1. A magnetic resonance imaging apparatus comprising:

first processing circuitry configured to execute a pulse sequence in an acquisition pattern set such that reduction factors in a plurality of pieces of k space data are made different in accordance with a predetermined imaging parameter when the pieces of k space data having different values of the imaging parameter are acquired while changing the values of the imaging parameter; and

second processing circuitry configured to generate an image based on the pieces of k space data, wherein

when the imaging parameter is included in a first range, the first processing circuitry acquires the pieces of k space data in a first region including a center in a k space with a first reduction factor and acquires the pieces of k space data in a second region that differs from the first region with a second reduction factor that differs from the first reduction factor, and

when the imaging parameter is included in a second range that differs from the first range, the first processing circuitry acquires the pieces of k space data in the first region with a reduction factor higher than the first reduction factor and acquires the pieces of k space data in the second region with a reduction factor lower than the second reduction factor.

2. The magnetic resonance imaging apparatus according to claim 1 , wherein the second processing circuitry generates a mapping image for the imaging parameter.

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

the imaging parameter is inversion time (TI),

the first processing circuitry acquires the pieces of k space data by controlling execution of the pulse sequence including pulse control for emitting radio frequency (RF) pulses of greater than 90 degrees, and

the second processing circuitry generates a T 1 mapping image based on the pieces of k space data.

4. The magnetic resonance imaging apparatus according to claim 1 , wherein

the imaging parameter is echo time (TE),

the first processing circuitry acquires the pieces of k space data by controlling execution of the pulse sequence including pulse control for acquiring multi echo, and

the second processing circuitry generates a T 2 mapping image based on the pieces of k space data.

5. The magnetic resonance imaging apparatus according to claim 1 , wherein

the imaging parameter is spin lock time (TSL),

the first processing circuitry acquires the pieces of k space data by controlling execution of the pulse sequence including pulse control for emitting spin lock pulses, and

the second processing circuitry generates a T 1 ρ mapping image based on the pieces of k space data.

6. The magnetic resonance imaging apparatus according to claim 1 , wherein the first range is a range in which degree of variation in a corresponding pixel value is equal to or higher than a predetermined value and the second range is a range in which the degree of the variation in the corresponding pixel value is lower than the predetermined value.

7. The magnetic resonance imaging apparatus according to claim 1 , wherein the second processing circuitry generates, in at least one region of the first region and the second region, first k space data at a k-space position at which k-space data is not acquired, using second k-space data at the k-space position, the first k-space data and the second k-space data corresponding to a different value of the imaging parameter.

8. The magnetic resonance imaging apparatus according to claim 1 , wherein the second processing circuitry generates, in at least one region of the first region and the second region, first k space data at a first k-space position at which k-space data is not acquired, using second k-space data at a second k-space position that is within a predetermined range from the first k-space position, the first k-space data and the second k-space data corresponding to a different value of the imaging parameter.

9. The magnetic resonance imaging apparatus according to claim 1 , wherein the first processing circuitry acquires the pieces of k space data in the first region with the first reduction factor and acquires the pieces of k space data in the second region with the second reduction factor, and then acquires the pieces of k space data in the first region with a reduction factor higher than the first reduction factor and acquires the pieces of k space data in the second region with a reduction factor lower than the second reduction factor.

10. The magnetic resonance imaging apparatus according to claim 1 , wherein the first processing circuitry executes the pulse sequence in the acquisition pattern set such that a sampling density over the entire k space data is a predetermined value.

11. An image generation method comprising:

executing a pulse sequence in an acquisition pattern set such that reduction factors in a plurality of pieces of k space data are made different in accordance with a predetermined imaging parameter when the pieces of k space data having different values of the imaging parameter are acquired while changing the values of the imaging parameter; and

generating an image based on the pieces of k space data, wherein

when the imaging parameter is included in a first range, the method comprises:

acquiring the pieces of k space data in a first region including a center in a k space with a first reduction factor, and

acquiring the pieces of k space data in a second region that differs from the first region with a second reduction factor that differs from the first reduction factor; and

when the imaging parameter is included in a second range that differs from the first range, the method comprises:

acquiring the pieces of k space data in the first region with a reduction factor higher than the first reduction factor, and

acquiring the pieces of k space data in the second region with a reduction factor lower than the second reduction factor.