Routine testing of magnetic field homogeneity on clinical MRI systems.

Poor main magnetic field (B0) homogeneity (H(B)) leads to artifacts and signal losses in magnetic resonance imaging (MRI). The American College of Radiology's MRI quality control manual mandates annual checks of H(B), suggesting tests using spectral linewidth and phase-difference (delta phi) maps. A new method, the bandwidth-difference (deltaBW) method, which compares the distortion for small and large BW acquisitions to determine the HB, is proposed.