Electromagnetics in magnetic resonance imaging

Magnetic resonance imaging (MRI) is a powerful new imaging method, which produces cross-sectional tomographic and three-dimensional images similar to those of x-ray computed tomography (CT). However, rather than relying on harmful ionizing radiation, MRI is based on the interaction between RF fields and certain atomic nuclei in the body, when they are in the presence of a strong magnetic field. An MRI system is one of the few complete systems in which the design relies heavily upon a knowledge of electromagnetics. In this article, we give a tutorial on the electromagnetic analysis and design of three key components of an MRI system, namely, the magnet, the gradient coil, and the radiofrequency (RF) coil. We will also discuss the analysis and characterization of the interactions of RF electromagnetic fields with biological subjects.