MAGNETIC RESONANCE IMAGING DEVICE AND TIMING MISALIGNMENT DETECTION METHOD THEREOF

摘要

A magnetic resonance imaging device produces a magnetic field gradient with parallel driving of positive-side subcoils and negative-side subcoils with different power sources in the magnetic field gradient direction, to detect a misalignment in drive timing of the positive side and the negative side. Pulse sequences for timing misalignment detection having a slice magnetic field gradient pulse and a read-out magnetic field gradient pulse in the same direction as a magnetic field gradient of interest are executed. A positive-side slice echo and a negative-side slice echo of the magnetic field gradient are acquired. A phase difference between a positive-side projection image and a negative-side projection image is derived by computation with phase error from other factors being removed. From the slope of the phase difference with respect to a location, the drive timing misalignment between the positive-side subcoil and the negative-side subcoil of the magnetic field gradient production is detected.

主权项

1. A magnetic resonance imaging device comprising:
a unit for generating a static magnetic field in a predetermined direction in a predetermined inspection space; a magnetic field gradient generator for generating magnetic field gradients in three directions, imparting a gradient to a magnetic field intensity in the inspection space along each of three axes orthogonal to one another; a unit for applying a high frequency magnetic field to a subject laid in the inspection space; a sequencer for controlling generation of the magnetic field gradients in the three directions, application of the high frequency magnetic field to the subject, and reception of a magnetic resonance signal generated from the subject by the preceding components; and a computing unit for processing the detected magnetic resonance signal, wherein the magnetic field gradient generator includes a positive-side subcoil and a negative-side subcoil for generating the magnetic field gradients in the three directions through composition, and power sources each for supplying current to the positive-side subcoil and the negative-side subcoil; the sequencer executes a plurality of pulse sequences used for detecting a drive timing misalignment between the positive-side subcoil and the negative-side subcoil, generating the magnetic field gradient in a first direction among the three directions through composition, and for measuring an echo of one of a first slice at a position shifted to the positive-side subcoil from an origin of the magnetic field gradient, and a second slice at a position shifted to the negative-side subcoil from the origin under a read-out magnetic field gradient pulse in the first direction, and the computing unit determines the drive timing misalignment between the positive-side subcoil and the negative-side subcoil by deriving projection images of the first slice and the second slice from application of an inverse-Fourier transformation on echo signals measured by the pulse sequences, obtaining a phase difference between the projection images of the first slice and the second slice, and computing a change width of a drive timing of one of the positive-side subcoil and the negative-side subcoil, which is required to allow a slope of the phase difference with respect to a location along the first direction to become zero.