QUIET GRADIENT COILS - ACTIVE ACOUSTICALLY AND MAGNETICALLY SCREENED DISTRIBUTED TRANSVERSE GRADIENT DESIGNS

The principle of active acoustic screening, recently introduced by Mansfield, Glover and Bowtell into the design of gradient coils for MRI, utilizes Lorentz force balancing to reduce acoustic noise. In this paper, the active acoustic screening principle is used to design cylindrical transverse gradients with distributed conductor or fingerprint designs for the primary. A second distributed conductor on a second surface is used to balance ail Lorentz forces on the coil system. A third conductor wound on a third surface is employed to provide active magnetic screening of the whole system. Alternative distributed conductor arrangements are analysed in terms of their practical performance.