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Validation and cross-comparison of MRI temperature mapping against fibre optic thermometry for microwave heating of foods


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The heating of a 5% starch gel in a standard domestic microwave oven has been measured using a combination of magnetic resonance imaging (MRI) ‘offline’, and fibre optic thermometry ‘online’. MRI was used to locate potential hot and cold spots for optimal placement of the fibre optic probes used to measure temperatures both during microwave heating and for the subsequent 100 s which is the time required for transfer of the sample to the magnet (38–48 s) and the acquisition of the 32 × 32 × 128 pixel MRI temperature map (52 s). The MRI data have a systematic offset because of the finite transferral time and duration of the MRI scan, but not to the detriment of high spatial resolution which is necessary to resolve the high temperature gradients induced. It is believed that 3D MRI temperature mapping will be invaluable to further studies of microwave heating as optimized placement of fibre optic thermometry probes is difficult, and the spatial distribution of microwave absorption is highly variable.