Pacemaker response to scattered radiation of different dose rates

Objective.AAPM Task Group Report 203 (TG203) recommends implantable cardiac pacemaker (ICP) dependent patients receive elevated precautions and that maximum dose rates to ICPs should be less than 0.2 Gy min^-1. Unfortunately, there is little quantitative data published about how ICPs are impacted by radiation dose rates near 0.2 Gy min^-1. The objective of this paper is to report on modern ICP behavior in response to dose rates near this suggested limit.Approach.Five single chamber (Azure XT SR) and five dual chamber (Azure XT DR) ICPs were submerged in 0.45% saline solution and placed 1 cm outside the field edge of a 10 × 10 cm²beam. Photon beams of energies 6 MV, 6FFF, 10 MV, and 10FFF were tested, with dose rates ranging from 0.15 to 0.92 Gy min^-1on Varian True Beam and Ethos LINACs. Real-time electrogram data were collected and analyzed for any malfunctions while the beam was on and off. Battery life of each ICP was also checked before irradiation and 6 months post-irradiation.Main results.No ICP malfunctions or artifacts were observed, even as dose rate increased. Battery life showed normally expected depletion 6 months post irradiation.Significance.This work studies ICP functionality in clinically relevant radiation therapy conditions and measures the performance of the devices in the context of an ICP dependent patient.