ESTRO 2025 - Abstract Book

S2661

Physics - Detectors, dose measurement and phantoms

ESTRO 2025

3948

Digital Poster Dose estimation to the pacemaker using OSL dosimetry in anthropomorphic phantom for brain cancer treatment plans Romanski Piotr 1 , Skrobala Agnieszka 2,1 , Bajon Barbara 1 , Stys Sara 1 , Matuszewski Krzysztof 1 , Jasiewicz Paulina 1 , Kruszyna-Mochalska Marta 2,1 1 Department of Medical Physics, Greater Poland Cancer Center, Poznan, Poland. 2 Department of Electroradiology, University of Medical Science, Poznan, Poland Purpose/Objective: Over the last few years, the number of patients with cardiac implantable electronic devices (CIEDs) undergoing radiotherapy has steadily increased, highlighting the need to evaluate the radiation absorbed by these devices. This study aimed to develop a method for measuring and estimating the radiation dose in close proximity to the pacemaker during brain cancer treatments.

Material/Methods:

Fig. 1. Six OSL detectors were placed around the pacemaker. One OSL detector was placed under the pacemaker. Twenty-four brain cancer VMAT plans were simulated in an Alderson Radiation Therapy phantom (Gardena, USA). The treatment plans targeted the whole brain (n=8), the left hemisphere (n=8), and the right hemisphere (n=8) of the brain. The prescribed dose per fraction ranged from 1.8-4 Gy. An example of a pacemaker (Biotronic, Berlin, Germany) was placed on the left side of the phantom and surrounded by a 5 mm super-flex bolus. The OSL dosimeters (RadPro International GmbH, Fraiburg, Germany) were adapted to out-of-field measurement and positioned around the pacemaker (Fig. 1). Results: The highest radiation dose was measured at the point, in close proximity to the edge of the treatment volume. The mean doses at that point were 5.04 ± 1.28 mGy, 2.43 ± 0.66 mGy, and 2.17 ± 0.46 mGy per 1 Gy of prescribed dose to the target for the whole brain, left hemisphere, and right hemisphere treatment plans, respectively. At the other OSL detector’s locations around the pacemaker, the measured doses were 24.07-49.79 %, 23.04-45.67 %, and 10.27 46.92 % lower than at the maximum dose point. Across all 24 treatment plans, the total estimated dose to any part of the pacemaker was less than 0.38 Gy. Conclusion: The OSL detectors, due to their characteristics, allow for the measurement of low doses out of the radiation field. The total estimated dose to any part of the pacemaker based on phantom measurements for brain cancer