Magnetic resonance imaging apparatus with correction of magnetic field gradient waveform distortion

摘要

In order to improve image quality, a technique for obtaining information for eliminating distortions of the k-space in the readout direction and the phase encoding direction caused by the waveform distortion of the gradient magnetic field pulse is provided. A pulse sequence for the main scan is used to repeatedly measure echoes with changing the time integral value of the dephasing pulse for the readout gradient magnetic field. In the above measurement, the phase encoding pulse is not made zero, but two-dimensional data are measured in the same manner as that of the main scan. By using the measured two-dimensional data, correction information for eliminating distortions of the k-space in the readout direction and the phase encoding direction caused by the waveform distortion of the gradient magnetic field pulse is calculated in each of the readout direction and the phase encoding direction.

主权项

1. A magnetic resonance imaging apparatus comprising a signal measurement part for applying a radio frequency magnetic field and a gradient magnetic field to a subject placed in a static magnetic field and measuring magnetic resonance signals generated from the subject, and a processor for controlling the signal measurement part and processing the magnetic resonance signals measured by the signal measurement part, wherein,
the processor comprises a correction information calculator for calculating correction information used for eliminating distortion of the measured magnetic resonance signals, and the correction information calculator comprises: a reference measurement part for controlling the signal measurement part to repeat a unit measurement of applying a readout gradient magnetic field and a phase encoding gradient magnetic field with changing phase encoding amount to repeatedly obtain echoes, and arranging a plurality of the obtained echoes in the k-space to obtain one set of k-space data with changing dephase readout amount to obtain a plurality of sets of k-space data, and a shift amount calculator for calculating shift amounts of peak positions of the echoes in the application direction of the readout gradient magnetic field and the application direction of the phase encoding gradient magnetic field from the plurality of sets of the k-space data, and the correction information calculator calculates the correction information by using the calculated shift amounts.