Author(s):
1. Drazan Jaros, University Medical Center Groningen, Netherlands
2. Abel Bregman, 1. Department of Radiation Oncology, University Medical Center Groningen, University of Groningen, G, Netherlands

Abstract:
Introduction Patients that undergo electron irradiation sometimes require individual electron inserts that fit the corresponding applicator. In some cases, the blockage of the individual insert is large enough to cause dose differences between open field and the occluded field with the mould. In this project we aimed to establish at what occlusion percentage more than 5% dose difference occurred. Methods Absolute dose measurements were done with two different types of ion chambers, a plan parallel type chamber, PPC40 (PTW, Germany) and a cylindrical type chamber, cc13 (IBA, Germany). Measurements were performed under the same conditions. We used moulds from 10% to 90% field occlusion. In our institute, a 5% difference between delivered and prescribed dose for electron irradiation is considered clinically relevant. Therefore, results of more than 5% difference were recorded Results The next five tables show the measurement results where a dose difference of 5% was recorded between the open and occluded measurement for the range of occlusion percentages measured. Conclusion The dose difference of 5% between prescribed and delivered dose was already observed at small applicator sizes (6x6 cm) and a 50% blockage of the mould. Both ion chambers showed similar results. A workflow was implemented to measure every individual electron treatment for cases where the dose was expected to differ by more than 5%. The results from this study can be used to decide whether additional measurements and thereafter corrections to the number of MU prescribed are required.  

Thematic field:
SYMPOSIUM B - Biomaterials and nanomedicine

Date of abstract submission:
14.08.2025.

Conference:
Contemporary Materials 2025 - Savremeni Materijali

Applied paper from author