A Theoretical Basis for Coupling via Induced Currents to Biological Systems for Ultra Fast Switched Magnetic Field a

The development of new fast imaging NMR systems leads to the exposure of a significant fraction of the population to larger transient magnetic fields and thus to larger values of induced currents in the human body than have previously concerned designers of NMR systems. These currents may be as large as or larger than the natural currents that are flowing in the same region of the body. It is important to be able to estimate these currents in order to predict their impact on the biological system. The magnitude, time, and spatial distributions of these currents are all likely to be important in determining the biological impact. In this short report, we will review the basic equations and work out a number of examples that may help to illuminate possible side effects of the large transient magnetic fields.