Two-dimensional real-time quality assurance dosimetry system using μ-Al 2 O 3 :C,Mg radioluminescence films

• Published in: Physics and imaging in radiation oncology Vol. 16; p. 26
• Main Authors: F Nascimento, Luana, Verellen, Dirk, Goossens, Jo, Struelens, Lara, Vanhavere, Filip, Leblans, Paul, Akselrod, Mark
• Format: Journal Article
• Language: English
• Published: Netherlands 01.10.2020
• ISSN: 2405-6316

There is a continual need for more accurate and effective dosimetric systems for quality assurance (QA) as radiotherapy evolves in complexity. The purpose of this project was to introduce a new system that minimally perturbs the main beam, while assessing its real time 2D dose-rate and field shapes. The system combined reusability, linear dose-rate response, and high spatial and time resolution in a single radiation detection technology that can be applied to surface dose estimation and QA. We developed a 2D prototype system consisting of a camera, focusing lenses and short pass filter, placed on the head of a linear accelerator, facing an Al O :C,Mg radioluminescent film. To check the appropriateness of multi-leaf collimator, stability/reproducibility QA tests were prepared using the treatment planning system: including the routinely used alternating leaves, chair and pyramid checks. The Al O :C,Mg film did not perturb the dose vs depth dose curves determined with a point detector (-0.5% difference). Our results showed a dose-rate linear film response (R  = 0.999), from 5 to 600 MU/min. Measured output factors agreed with reference data within ~1%, indicating a potential for small field dosimetry. Both chair and pyramid measured profiles were comparable with those obtained with the treatment planning system within 1%. The alternating leaves test showed an average discrepancy in the valleys of 14%. The prototype demonstrated promising results. It obviated the need for corrections regarding the relative position of the camera, confirming accurate dose-rate delivery and detection of radiation fields.