Calculating the movement of MRI coils, and minimizing their noise

Abstract

The design of gradient coils within Magnetic Resonance Imaging equipment is considered. These coils produce linear magnetic fields in each of the three orthogonal directions in physical space. In addition, they are turned on and off repeatedly to enhance the clarity of the image, but this produces a great deal of noise within the coil, as its shape distorts under the influence of Lorentz forces. We present a method for calculating the movement of the coil in the background magnetic field, and estimating the consequent noise levels. This involves solving for the current density in the coil coupled with equations for its elastic deformation, along with acoustic equations for the pressure in the surrounding air. Winding patterns are designed to minimize the noise produced by the Magnetic Resonance Imaging coil.