Browsing by Subject "Pacemaker"

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    Piezoelectric power generation using heart motion
    (2006) Afacan, Onur
    The presence of pacemakers and implantable cardioverter-defibrillators (ICD) is considered historically a contraindication to magnetic resonance (MR) imaging. Main reason behind this contraindication is the current induced on the pacing leads during the MRI examination which may damage the cardiac tissues by heating or the pulse generator of the pacemaker with a reverse current. In this thesis an approach towards the solution of this problem is stated. It has been shown in previous work that replacing the pacing leads with fiber-optic cables minimizes the current induced on the leads. Drawback of this system is the increase in the power consumption of the pacemaker because of the fiber-optic cables and also necessity of an additional pulse generator circuitry near the heart. In this thesis, feasibility of using a piezoelectric power generator for compensating the increased power consumption is investigated. A novel piezoelectric geometry increasing the effective length in a given volume is designed. With this device the resonance frequency of the generator was decreased and the power output for a given volume is increased compared to standard rectangular piezoelectric bimorphs. When connected to a simple heart phantom the novel design produced 2.83 microwatts power whereas the standard rectangular bimorphs produced less than 1 microwatts. Although the output power is increased with the novel design, it was not sufficient to power a pulse generator circuitry that will be used to pace the heart.
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    Safety of metallic implants in magnetic resonance imaging
    (2005) Ferhanoğlu, Onur
    Magnetic Resonance Imaging (MRI) is safe only if we take safety precautions. In the presence of a metallic implant inside the body, three types of magnetic fields encountered in MRI (Static magnetic field, radiofrequency field, gradient field) may become the sources of safety problems. In this thesis, temperature increase created by a pacemaker under MRI is investigated. Electromagnetic simulations are performed, in-vivo, phantom experiments are conducted and finally bioheat equation is solved to find the corresponding temperature increase. Using this temperature increase the input power can be limited to ensure safe scans. MRI compatible lead design is the essential innovation of this thesis which is directly applicable to any kind of metallic, wire shaped interventional MRI device.