Magnetic resonance imaging device, magnetic resonance imaging method and susceptibility calculation program

A magnetic resonance imaging method, comprising,

• measuring a nuclear magnetic resonance signal including effects of magnetic field inhomogeneity,
• creating a complex image by using the nuclear magnetic resonance signal, and
• creating a magnetic field reflected image by using the complex image, and creating a susceptibility image by using the magnetic field reflected image,
• wherein a low-signal region mask and a high-signal mask are generated by using an absolute value image created from the complex image, and a first region mask and a second region mask are created from the high-signal mask, the first region mask representing a first region where a pixel value of a certain discriminant image is larger than a predetermined threshold and the second region mask representing a second region where the pixel value of the discriminant image is equal to or smaller than the predetermined threshold, and
• wherein by using the magnetic field reflected image, the low-signal region mask, and the first and the second region masks, a first region susceptibility image is calculated under a first constraint that a region defined by the low-signal region mask is set as a background, and a second constraint that the susceptibility of the second region is set to a specific value, and a second region susceptibility image is calculated under the constraint that the region defined by the low-signal region mask and the first region are set as the background.

A non-transitory computer readable medium storing a susceptibility calculation program causing a computer to execute steps comprising:

• creating a complex image using a nuclear magnetic resonance signal including effects of magnetic field inhomogeneity, measured by a magnetic resonance imaging apparatus,
• creating a magnetic field reflected image by using the complex image,
• creating an absolute value image from the complex image, creating a low-signal region mask and a high-signal mask by using the absolute value image, and further creating from the high-signal mask, a plurality of region masks associated with a plurality of regions,
• calculating the first susceptibility of a region excluding a specific region, by using the magnetic field reflected image, the low-signal region mask, and the plurality of region masks, under a first constraint that a region defined by the low-signal mask is set as a background, and a second constraint that the susceptibility of the specific region among the plurality of regions is set to a specific value,
• calculating the second susceptibility of the specific region, under a third constraint for setting as the background, the region defined by the low-signal region mask and the region defined by the region mask associated with a region excluding the specific region, and
• combining the first susceptibility and the second susceptibility to generate a susceptibility image.