In-vitro investigation of cardiac implantable electronic device malfunction during and after direct photon exposure: A three-centres experience.

PURPOSE: Radiotherapy may cause malfunction of implantable cardioverter-defibrillators (ICDs) and pacemakers (PMs). We carried-out a multicentre randomized in-vitro study on 65 ICDs and 145 PMs to evaluate malfunctions during and after direct irradiation to doses up to 10 Gy. METHODS: Three centres equipped with different linear accelerator and treatment-planning systems participated in the study. Computed Tomography (CT) acquisitions were performed to build the treatment plans. All devices were exposed to dose of 2, 5, or 10 Gy (6 MV). All devices underwent a baseline examination and 64 wireless real-time telemetry-transmissions (47 ICDs and 17 PMs) were monitored during photon exposures. All devices were interrogated after exposure and once monthly for six subsequent months. RESULTS: Fifty-four of the 64 wireless-enabled CIEDs (84.4%) recorded noise-related interferences during exposure. In detail, 40/47 ICDs (85.1%) reported interference, of which 16 ICDs (34%) reported potentially clinically relevant pacing inhibition and inappropriate detections. Following exposure, a soft reset occurred in 1/145 PM (0.7%) while 7/145 PMs (4.8%) reported battery issues. During the six-month follow-up, 1/145 PM (0.7%) reported a soft reset, while 12/145 more PMs (8.3%) and 1/64 ICD (1.5%) showed abnormal battery depletion. All reported issues occurred independently of exposure dose. Finally, irreversible effects on software and battery life occurred in only non-MRI-compatible devices. CONCLUSION: ICDs mostly featured real-time transient sensing issues, while PMs mostly experienced long-term battery or software issues that were observed immediately following radiation exposure and during follow-up. Irreversible effects on battery life and software occurred in only non-MRI-compatible devices.

Dose calculation accuracy in proximity of a pacemaker: A multicenter study with threecommercial treatment planning systems.

This study compares Treatment Planning System (TPS) out of field dose calculation on a pacemaker (PMK) during external beam radiotherapy treatment. We consider four TPSs (Elekta-Monaco, Oncentra- Masterplan and two Philips-Pinnacle3) commissioned for two linacs (Elekta Sinergy and Varian Clinac) delivering two test beams (a highly modulated one and a square field) and two clinical breast plans. To calculate and measure dose to a PMK we built a Real Water3 phantom with a PMK embedded in it. Measures are performed with thermo-luminescent dosimeters and Mosfet dosimeters. We evaluate differences between TPS calculated values for the dose to the PMK (both point dose and dose-volume histogram parameters) when the PMK is positioned in the first 10 cm outside the radiation fields. TPS calculation accuracy is evaluated comparing such values with measures. Differences in TPS calculations are on average 3.5 cGy Gy-1 for the modulated beam, and always lower than 2 cGy Gy-1 for the square beam. TPS dose calculation depends mostly on the TPS algorithm and model rather than the linac commissioned. TPSs considered show different degrees of calculation accuracy. In the first 4 cm to the field edge three out of four TPSs are in good agreement with measurements in the square beam, but only one keeps the agreement in the modulated beam: the others show over and underestimations up to +20% -40%. The same accuracy is found considering a homogeneous phantom. Our results confirm what reported in previous studies and highlight the impact of TPS commissioning.