Controlled E-field gradient coils

• Published in: Magma (New York, N.Y.) Vol. 16; no. 3; pp. 113 - 120
• Main Authors: Mansfield, P., Bowley, R. M., Haywood, B.
• Format: Journal Article
• Language: English
• Published: Germany Springer Nature B.V 01.11.2003
• Subjects: Computer Simulation; Computer-Aided Design; Equipment Design; Equipment Failure Analysis; Equipment Safety - instrumentation; Equipment Safety - methods; Evoked Potentials - radiation effects; Humans; Magnetic fields; Magnetic Resonance Imaging - adverse effects; Magnetic Resonance Imaging - instrumentation; Magnetic Resonance Imaging - methods; Magnetics - adverse effects; Magnetics - instrumentation; Models, Biological; Neurons - radiation effects; Radiation Dosage; Radiometry - methods
• ISSN: 0968-5243; 1352-8661; 1352-8661
• DOI: 10.1007/s10334-003-0015-7

Peripheral neural stimulation is a major problem in current gradient coil designs. Induced current problems in patients relate directly to gradient strength and modulation frequency. Current designs of gradient coil tend to limit ultra-high-speed imaging methods such as echo-planar imaging through the effect of induced currents which produce tingling sensations and involuntary muscle twitch. Neural stimulation could also trigger epileptic fits and/or cardiac fibrillation. For reduction of induced currents, an important aspect is the coil geometry. It is desirable to design the gradient coil in such a way as to prevent closed loop circulating currents within the body. Preliminary results using a four-sector gradient coil with rectangular geometry, operating in a low mutual coupling mode, indicate significant reduction in the E-field within the subject volume of the coil. Reduction in induced currents in the patient allows safer operation at higher magnetic field strengths together with faster scans currently prohibited through neural stimulation effects in standard coil geometries.