Enhancement of the Spatial Resolution for the Temperature Sensing System of the 7 Tesla Magnetic Resonance Imaging Scanner

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The MRI scanner with an ultrahigh magnetic field of 7T not only increases the image resolution but it also increases the Specific Absorption Rate (SAR) of the patient. In other words, the body temperature of the patient increases due to the absorption of heat produced by the 7T MRI scanner. This is dangerous for the health of the patient. In order to ensure that the SAR level of the patient does not exceed the acceptable limit, the body temperature of the patient should be monitored during the scan with a spatial resolution as small as possible. This way safety measures can be taken immediately if the body temperature increases. In order to monitor the temperature during the MRI scan, fiber optic sensors (FOS) can be used. The fiber optic sensors (FOS) are immune from electromagnetic interference and there is no electrical connection to the patient and thus it is safe to monitor the temperature during an MRI scan by using FOS [1]. However, the FOS may have a spatial resolution which is not acceptable for medical purposes. This study focuses on methods to increase the spatial resolution of an existing fiber optic temperature sensing system of a 7T MRI scanner. To increase the spatial resolution of the existing temperature sensing system two methods are evaluated, namely the total variation deconvolution method and the blind deconvolution method. This study shows that the total variation deconvolution method gives the best results for the input temperature estimate. The blind deconvolution method strongly depends on the initial guess of the impulse response of the temperature sensing system, which is difficult to find. Therefore the results of the input temperature and the impulse response are less reliable when using the blind deconvolution method. Also it is shown that the machine resolution gets worse when increasing the spatial resolution by interpolating the input temperature in the Fourier domain.