This paper examines the measurement of the specific absorption rate (SAR) of radio frequency energy during magnetic resonance imaging using an optical electric field sensor (OEFS). The sensor was used to measure SAR in a simple phantom during a 3-Tesla MRI scan and the results compared to computer simulations and also those obtained through temperature measurements. Good agreement is demonstrated. The optical electric field sensor has much higher sensitivity for SAR measurement than thermometers and the measurements are much quicker. The application of this technology allows the spatial distributions of SAR within phantoms during MRI to be measured.

This study investigates the importance of accurate sensor placement when assessing implant safety during MRI scans experimentally. A combination of measurement and finite element modelling was used to assess sensitivity of measurement to sensor placement, for temperature rises at the ends of a set of calibration cylinders. The simulations used a coupled thermal-electromagnetic model created using COMSOL Multiphysics to replicate the measurement conditions virtually. Thermal gradients in parametric models of cylindrical implants of varying length and diameter were evaluated to quantify the sensor placement accuracy required for the measurement of implant heating within the estimated temperature measurement uncertainty. In this way we aim to enhance the understanding of the requirements for experimental procedures and safety standards dealing with implant heating in MRI.

E-field probes used for measurement of worker exposure are usually calibrated in continuous wave (CW) conditions. For many types of probe, the response in realistic environments (modulated signals, multi-frequency and pulsed signals) differs from the response to CW conditions. However, to fully characterize a field probe in all possible environments would be an infinite task.In this paper we consider the effect of multiple CW signals and of several common communications formats on the indication given by a field probe with the objective of identifying simple tests which could act as a predictor of the performance alteration in non-CW environments.

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