Establishing radiation therapy treatment planning effects involving implantable pacemakers and implantable cardioverter-defibrillators

Abstract

It has been of late interest to pursue methods of improving upon the functionality and stability of implantable pacemakers and cardioverter-defibrillators by evolving them to include efficient battery power consumption and radiation hardened electrical circuits. It has also been of continued interest for manufacturers to pursue MRI compatibility for these devices. While such newer models of pacemakers and cardioverter-defibrillators are similar in construction to previously marketed devices, even for the recently FDA approved MRI compatible designs currently in clinical trials, an increased interest is now being seen with regard to radiation therapy dose effects when a device is directly in the field of radiation. Specifically, the limitation on dose to the device from therapeutic radiation beams is being investigated for a possible elevation in limit. Adjacent to that interest, we promulgate here the first ever study with issuance to determine dosimetric effects from implantable pacemakers and implantable cardioverter-defibrillators in high energy x-ray beams from a medical accelerator. Treatment plan simulations were analyzed for 4 different pacemakers and 5 different implantable cardioverter-defibrillators and intercompared with direct measurements from a miniature ionization chamber in water. All defibrillators were seen to exhibit the same results and all pacemakers were seen to display the same consequences, within only a ± 1.8 % deviation for all x-ray energies studied. Attenuation, backscatter and lateral scatter were determined to be -13.4 %, 2.1 % and 1.5 % at 6 MV and -6.1 %, 3.1 % and 5.1 % at 18 MV for the defibrillator group. For the pacemaker group, this research concluded results of -15.9 %, 2.8 % and 2.5 % at 6 MV and -9.4%, 3.4 % and 5.7 % at 18 MV, respectively. Limited results were discovered from scattering processes through computer modeling. Strong verification from measurements was concluded with respect to simulating attenuation characteristics.