Eddy Current Heating of Metallic Shells and Plates: Application to Gradient-Induced Conductor Heating in MRI

We consider eddy current heating of thin conductive objects that are placed in time-varying magnetic fields generated by multiple, independent field coils. This setting is particularly relevant to passive heating of metallic objects, such as radio frequency (RF) shields, in the bore of a magnetic resonance imaging (MRI) device. Previous studies have primarily focused on eddy current induced by a single driving coil or in a spatially uniform field. When multiple coils act on an object simultaneously, electric field interference needs to be properly accounted for in order to obtain accurate prediction of heating. Motivated by eddy current from MRI gradient coils, we focus on the low-frequency regime, where the conductive objects’ response is predominantly resistive. Based on the time-domain Maxwell’s equations, we derive a systematic method to calculate spatially resolved heating power density inside a conductive object. The method was tested against experimental measurement of temperature rise of stainless steel mesh in the bore of a human brain MRI scanner. The proposed method can be used to predict and mitigate heating of metallic components used in medical and scientific instruments that employ time-dependent and spatially varying magnetic fields.