Theory of gradient coil design methods for magnetic resonance imaging

The process to produce an MR image includes nuclear alignment, RF excitation, spatial encoding, and image formation. In simple terms, an magnetic resonance imaging (MRI) system consists of five major components: a magnet, gradient systems, an RF coil system, a receiver, and a computer system. To form an image, it is necessary to perform spatial localization of the MR signals, which is achieved using gradient coils. In modern MRI, gradient coils able to generate high gradient strengths and slew rates are required to produce high imaging speeds and improved image quality. MRI also requires the use of gradient coils that generate magnetic fields, which vary linearly with position over the imaging volume. Gradient coils for MRI must therefore have high current efficiency (defined as the ratio of gradient generated to current drawn), short switching time (i.e., low inductance), gradient linearity over a large volume, low power consumption, and minimal interaction with any other equipment, which would otherwise result in eddy currents. Over the last two decades new methods of gradient coil design have been developed, and a combination of these methods can be a mixture of them trying to avoid discomforts to patients that at the end is the center of all the technological efforts in the art of MRI. © 2010 Wiley Periodicals, Inc. Concepts Magn Reson Part A 36A: 223–242, 2010.