MULTIPOLAR LAMINATED ELECTROMAGNET FOR LOW-FIELD MAGNETIC-RESONANCE-IMAGING AND ELECTRON-PARAMAGNETIC-RESONANCE IMAGING

A cylindrical 16-pole electromagnet (EM) for electron paramagnetic res onance imaging (EPRI) and low-field magnetic resonance imaging (MRI) h as been designed by means of two-dimensional and three-dimensional (3- D) finite element analysis (FEA). The use of an automatic procedure th at combines FEA with a minimization routine allowed the optimization o f the design, in order to improve the homogeneity along the axis of th e EM. A prototype has been built by using electrical steel sheets that were cut by laser; this solution reduced significantly the manufactur ing cost. The Ehl operates with a maximum flux density, in the bore, o f 0.08 T and has a homogeneity along the axis of about 40 parts per mi llion (ppm) in a spherical region 10 cm in diameter. It generates the main field and two of the three field gradients required in the 3-D im age reconstruction. Good agreement was found between the results of si mulation and the measured values.