Distortion of Gradient Coils Performances in Presence of Iron

Alice Borceto¹, Andrea Viale¹, Franco Bertora¹, Leonardo Bertora², Richard Bowtell³

The performances of an unshielded gradient system can be heavily affected by the presence of an iron yoke, increasing the non-linearity and non-uniformity of the field in the region of interest. This departure from ideal performance causes image distortions. It is therefore important to study the interaction between unshielded gradient coils and the iron yoke. Here, three different techniques for modelling the effect of iron (mirror coils, boundary element method and full finite element simulation) are presented and the results compared. Among the three the boundary element method offers the best compromise between accuracy and calculation time.