title: Minimum maximum temperature gradient coil design.
abstract: Ohmic heating is a serious problem in gradient coil operation. A method is presented for redesigning cylindrical gradient coils to operate at minimum peak temperature, while maintaining field homogeneity and coil performance. To generate these minimaxT coil windings, an existing analytic method for simulating the spatial temperature distribution of single layer gradient coils is combined with a minimax optimization routine based on sequential quadratic programming. Simulations are provided for symmetric and asymmetric gradient coils that show considerable improvements in reducing maximum temperature over existing methods. The winding patterns of the minimaxT coils were found to be heavily dependent on the assumed thermal material properties and generally display an interesting "fish-eye" spreading of windings in the dense regions of the coil. Small prototype coils were constructed and tested for experimental validation and these demonstrate that with a reasonable estimate of material properties, thermal performance can be improved considerably with negligible change to the field error or standard figures of merit.
authors.affiliation: School of Mathematics and Physics, Faculty of Science, Engineering and Technology, University of Tasmania, Hobart, Tasmania, Australia. peter.while@imtek.unifreiburg.de
authors.forename: Peter T
authors.initials: PT
authors.lastname: While
authors.forename: Michael S
authors.initials: MS
authors.lastname: Poole
authors.forename: Larry K
authors.initials: LK
authors.lastname: Forbes
authors.forename: Stuart
authors.initials: S
authors.lastname: Crozier
mesh_terms: D016477:Artifacts; D003198:Computer Simulation; D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006358:Hot Temperature; D007089:Image Enhancement / Q000295:instrumentation*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D008280:Magnetics / Q000295:instrumentation*; D008962:Models, Theoretical; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014159:Transducers