Numerical and Experimental Study of Pacemaker Safety under MRI

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Pacemaker safety issues with MRI (Magnetic Resonance Imaging) are discussed in this thesis. In order to analyze the electromagnetic compatibility issue of pacemaker/defibrillator with MRI RF (radio frequency) coil and human body model, novel techniques for the evaluation of MRI-induced heating or induced voltage in the vicinity of implanted metallic lead have been developed based on the reciprocity theorem. The measurement configurations have been described in detail. The technique was validated in both numerical and experimental studies on different lead structures. More than one hundred transfer functions of real practical pacemakers are measured, and hundreds of validation tests were performed on those transfer functions. In addition, the effects of human body/phantom were also discussed based on the measured transfer functions and human body simulations. This approach allows one to decouple the micro-scale metallic lead simulation/measurement from the macro-level phantom human simulations within the MRI scanners. Consequently, the estimation of MRI-induced heating on an implanted lead, and the induced voltage on the pacemaker device can be greatly simplified. The analysis about the pacemaker safety issue will become very efficient. In addition, this method clearly explains the induced lead heating mechanism during MRI procedures.

MRI, Pacemaker, EMC, Synthetic aperture radar (SAR), Induced voltage, FDTD, Reciprocity