Events Calendar

MRI Coils: Theory and Practice

Speaker: Professor Cecil Hayes, University of Washington

Talk Title: MRI Coils: Theory and Practice

Abstract: Radio frequency coils provide the interface between patient and the electronics in an MRI scanner. All the information conveyed between the subject and the scanner passes through and is conditioned by the RF coils. Thus, the design of the RF coils is a critical element in the overall performance of an MRI scanner. Transmit coils produce the radio frequency field B1, which excites and manipulates the nuclear spins. Most often, the transmit coil is a large volume coil that produces a homogeneous RF field so that all spins are excited equally. The primary function of a receive coil is to pick up the magnet field generated by the precessing spins and convert it to an electronic signal. The receive coil also picks up noise emanating from the sample material such as tissue. A well designed receive coil and its preamplifier should add very little additional noise to the desired signal. A small surface coil can produce a higher signal-to-noise ratio (SNR) than a larger volume coil but only in localized region. The surface coil couples strongly to the signal locally but not to the noise originating from more distance tissue. The larger field-of-view of a volume coil can be recovered by using a phased array of smaller coils that retain their higher SNR. The amplitude and phase of the signal induced in a surface coil is dependent on the relative location of the voxel and the coil. A technique called parallel imaging exploits this added spatial information of an array to shorten the imaging time by substituting for some of the gradient encoding.

Biography: Prof. Cecil Hayes obtained his Ph.D. in physics from Harvard in 1973. His thesis used NMR to study internal fields in zinc chalcogenides. Post doctorates at Rutgers and University of Utah applied NMR to critical phenomena of xenon and ionic motion in sodium beta alumina. While at Utah, he built a small magnetic resonance imager to quantify lung water in rats. In 1982, he joined GE Medical Systems in Milwaukee and helped developed their 1.5T Signa scanner. He is best known as the inventor of the birdcage coil that is commonly used as the volume coil in most scanners. Since 1991, he has been at University of Washington, where he developed specialized phased arrays for diagnostic imaging and research on humans and animals.

Host: Professor Krishna Nayak and Dr. Yoon Chul Kim

Location: Hughes Aircraft Electrical Engineering Center (EEB) - 248

Audiences: Everyone Is Invited

Contact: Mary Francis