Double-cavity open permanent magnet for dedicated MRI

A new 0.2 T magnetic structure for dedicated (extremities) Magnetic Resonance Imaging is presented. The main features are: magnetic circuit based on rare-earth permanent magnet material and iron, ergonomic double-height cavity shape (optimized to allow shoulder, legs and joints examinations in a very compact magnet with respect to traditional whole body systems), special design of split pole plates to improve magnetic field homogeneity and reduce eddy current effects. The typical magnetic field homogeneity (a few parts per million inside the imaging volume) necessary for MRI is achieved with a special shimming procedure, also outlined in the paper. The presented magnet is part of a commercial scanner produced by Esaote S.p.A (E-SCAN/sup TM/).