Magnetic resonance imaging apparatus and analysis method for fat suppression effect in magnetic resonance imaging apparatus

1. A magnetic resonance imaging apparatus (MRI) comprising:

an imaging unit which performs MR imaging more than once with respect to an imaging target while changing a central frequency of a fat suppression pulse sequence utilized in an MRI scan each time imaging is performed;

a generation unit which generates a plurality of reconstructed MR images based on magnetic resonance signals obtained by MR imaging being performed more than once; and

a calculation unit which calculates factor information, which contributes to spatial inhomogeneity of a fat suppression effect based on the plurality of reconstructed MR images, and storing or outputting said factor information.

2. The magnetic resonance imaging apparatus according to claim 1 , wherein the calculation unit obtains information related to inhomogeneity of a static magnetic field and information indicative of the fat suppression effect, which has no relation to a frequency shift of a fat suppression spectrum as the factor information contributing to the spatial inhomogeneity of the fat suppression effect.

3. The magnetic resonance imaging apparatus according to claim 2 , wherein the calculation unit calculates a shift amount between two frequency spectrums obtained at a magnetic field central position and a position other than the magnetic field central position based on the plurality of MR images as the information related to inhomogeneity of the static magnetic field.

4. The magnetic resonance imaging apparatus according to claim 1 , wherein the MR imaging unit performs MR imaging more than once while changing a polarity of at least one of a slice selective gradient magnetic field, a frequency read-out gradient magnetic field, and a phase encoding gradient magnetic field, and the calculation unit calculates at least one of information related to eddy magnetic field and information related to inhomogeneity of a static magnetic field based on a plurality of MR images obtained by the gradient magnetic field having a changed polarity as the factor information which contributes to the spatial in homogeneity of the fat suppression effect.

5. The magnetic resonance imaging apparatus according to claim 1 , wherein the calculation unit calculates information related to inhomogeneity of a radio-frequency pulse as the factor information which contributes to the spatial inhomogeneity of the fat suppression effect.

6. The magnetic resonance imaging apparatus according to claim 1 , further comprising a display unit which generates and displays an image representing spatial inhomogeneity of the fat suppression effect in a contour pattern as the factor information which contributes to the spatial in homogeneity of the fat suppression effect.

7. The magnetic resonance imaging apparatus according to claim 1 , further comprising a correction unit which corrects at least one of a central frequency of a fat suppression pulse at the time of actual imaging and a gradient magnetic field pulse at the time of application of the fat suppression pulse based on the factor information which contributes to the spatial inhomogeneity of the fat suppression effect.

8. The magnetic resonance imaging apparatus according to claim 1 , wherein the imaging unit obtains an echo without performing phase encoding in each of said imaging processes, which is performed more than once, and the generation unit subjects the echo obtained in each of said imaging processes, which is performed more than once to a one-dimensional Fourier transformation in order to generate each of said the plurality of MR images.

9. The magnetic resonance imaging apparatus according to claim 1 , wherein the imaging unit also uses a short T1 inversion recovery (STIR) method in order to carry out MR imaging more than once.

10. An analysis method of a fat suppression effect in magnetic resonance imaging, (MRI), said method comprising:

performing MR imaging more than once with respect to an imaging target while changing a central frequency of a fat suppression pulse sequence utilized in an MRI scan each time imaging is performed;

generating a plurality of reconstructed MR images based on MR signals obtained by MR imaging performed more than once; and

calculating factor information, which contributes to spatial inhomogeneity of the fat suppression effect based on the plurality of reconstructed MR images, and storing or outputting said factor information.