Systems and methods for shim current calculation

摘要

A method includes receiving a forward spatial encoding polarity magnetic resonance (MR) coil image and a reverse spatial encoding polarity MR coil image generated from data obtained with a magnetic field gradient that is reversed with respect to the magnetic field gradient with which the forward spatial encoding polarity MR coil image is acquired. The method also includes performing an iterative shift map calculation algorithm to determine a pixel shift map corresponding to a minimized difference between the forward and reverse spatial encoding polarity MR coil images, converting the pixel shift map into a magnetic field shift map by determining a magnetic field value corresponding to each pixel in the pixel shift map, and providing the magnetic field shift map as an input to a shim calculation process that includes determining a level of at least one shim current.

主权项

1. A method of shimming a magnetic resonance (MR) magnet of an MR imaging system, comprising:
receiving a forward spatial encoding polarity magnetic resonance coil image and a reverse spatial encoding polarity MR coil image, the reverse spatial encoding polarity MR coil image being generated from data obtained with a magnetic field gradient that is reversed with respect to the magnetic field gradient with which the forward spatial encoding polarity MR coil image is acquired; performing an iterative shift map calculation algorithm in order to determine a pixel shift map based in part on the forward spatial encoding polarity MR coil image, the reverse spatial encoding polarity MR image, and a cost function quantifying pixel displacements between the forward and reverse spatial encoding polarity MR coil images in order to stabilize at least linear first and second order spatial features of the pixel shift map; converting the pixel shift map into a magnetic field shift map by determining a magnetic field value corresponding to each pixel in the pixel shift map; and providing the magnetic field shift map as an input to a shim calculation process in order to determine a level of at least one shim current passed through at least one shim coil in order to shim the MR magnet.