MRI simulator with static field inhomogeneity

This paper describes a new MRI simulator that provides realistic images for arbitrary pulse sequences executed in the presence of static field inhomogeneities including those due to magnetic susceptibility, errors in the applied field, and chemical shift. In contrast to previous simulators, this system generates object-specific inhomogeneity patterns from first principles and propagates the consequent frequency offsets and intravoxel dephasing through the acquisition protocols to produce images with realistic artifacts. The simulator consists of two parts. Part 1 calculates a frequency offset for each voxel. It calculates the size of the static field offset at each voxel in the image based on the known magnetic susceptibility of each of the components at all voxels. It uses a novel implementation of the ?Boundary Element Method? and takes advantage of the superposition principle of magnetism to include voxels with mixtures of substances of differing susceptibilities. Part 2 produces both a signal and a reconstructed image. Its inputs include the 3D digital brain phantom introduced by the McConnell Brain Imaging Centre, frequency offsets computed by part 1, applied static field errors, chemical shift values, and a description of the acquisition protocol.