DETERMINATION OF SUSCEPTIBILITY- INDUCED MAGNETIC FIELD GRADIENTS BY MAGNETIC RESONANCE

摘要

The invention relates to a device for magnetic resonance imaging of a body (7). The device (1) comprises means (2) for establishing a substantially homogeneous main magnetic field in the examination volume, means (3, 4, 5) for generating switched magnetic field gradients superimposed upon the main magnetic field, means (6) for radiating RF pulses towards the body (7), control means (12) for controlling the generation of the magnetic field gradients and the RF pulses, means (10) for receiving and sampling magnetic resonance signals, and reconstruction means (14) for forming MR images from the signal samples. In accordance with the invention, the device is arranged to a) generate a series of MR echo signals (20) by subjecting at least a portion of the body (7) to an MR imaging sequence of RF pulses and switched magnetic field gradients, b) acquire the MR echo signals for reconstructing an MR image data set (21) therefrom, c) calculate a gradient map (22) by computing echo shift parameters (SP_x, SP_y, SP_z) from subsets of the MR image data set, the echo shift parameters (SP_x, SP_y, SP_z) indicating magnetic field gradient induced shifts of the echo positions in k-space, wherein each subset comprises a number (n) of spatially adjacent pixel or voxel values of the MR image data set (21).