Design of a Local Shim Coil to Improve B0 Homogeneity in the Cervical Spine Region

Stephan Biber¹, Katrin Wohlfarth¹, John Kirsch¹, Andreas Schmidt¹

B0 variation induced by the spatially inhomogeneous susceptibility distribution of the patient are a major challenge for application that rely heavily on B0 homogeneity such as EPI or spectral fat suppression techniques. In the abdomen, the major sources of B0-inhomogeneity are the lungs and the strongly asymmetric anatomy of the heart, while in the head, the sinuses and mouth generate major inhomogeneities. Another vulnerable region for B0 problems that has hardly been addressed is the transition from the upper thorax to the neck and head region. The shoulders are a strong discontinuity for the z-oriented B0 field and generate spatially large inhomogeneity. If the patients anatomy does not allow the ability to place the neck region completely flat on the table, B0 fields penetrating in and out of the patient in the posterior neck region generate additional B0 inhomogeneity. This can become an issue, e.g. for spectral fat suppression techniques applied to cervical spine imaging.