MRI compatible lead designs for implantable medical devices

Abstract

It is currently estimated that 600,000 cardiac pacemakers are implanted per year worldwide. It is expected that the usage of other stimulators such as deep brain stimulators (DBS) will reach this number in a short period. On the other hand, 2,000,000 MRI examinations are carried out each year worldwide and usage of MRI is expected to increase.

Unfortunately, people with metallic implants have significant risks in the MRI scanners. It is known that radio frequency and gradient fields of the MRI scanners may induce harmful currents on the implant leads. Radio frequency pulses may cause excessive heating and burns. In addition to this, time-varying gradient magnetic field induced currents on the leads can cause nerve stimulation. In case of cardiac pacemakers, this nerve stimulation may cause cardiac arrest. In this thesis, novel MRI compatible lead designs were proposed. Lead designs are presented to ensure safe magnetic resonance scanning of patients with active metallic implants such as pacemakers, neurostimulators, and implantable cardio defibrillators. Semiconductor components such as transistors and diodes are used to prevent these undesired induced currents on the implant leads. Circuits on the implants are designed such that while the induction of currents is prevented, the desired signal transmission in between the implanted pulse generator and the body part is maintained. The designs were tested by using experiments and computer stimulation. It was seen that the new techniques are effective in making MRI safe implantable devices. Benefits and problems of each design will be discussed in this text. It is believed that using this or similar techniques, patients with the implants will be able to be examined safely in MRI scanners.