ESTRO 2024 - Abstract Book

S3350

Physics - Detectors, dose measurement and phantoms

ESTRO 2024

2530

Digital Poster

Spatially resolved dosimetry and LET mapping using optically stimulated luminescence

Mads L. Jensen 1 , Camilla L. Nielsen 1 , Brain Julsgaard 1,2 , Rosana M. Turtos 1 , Morten B. Jensen 3,4,5 , Peter S. Skyt 3,5 , Liliana Stolarczyk 3,5 , Simon H. Vindbæk 3,5 , Ludvig P. Muren 3,5 , Peter Balling 1,2 1 Aarhus University, Department of Physics and Astronomy, Aarhus, Denmark. 2 Aarhus University, Interdisciplinary Nanoscience Center, Aarhus, Denmark. 3 Aarhus University Hospital, Centre for Particle Therapy, Aarhus, Denmark. 4 Aarhus University Hospital, Department of Medical Physics, Aarhus, Denmark. 5 Aarhus University, Department of Clinical Medicine, Aarhus, Denmark

Purpose/Objective:

The complexity of the treatment modalities used in contemporary radiotherapy (RT) imposes increasingly rigorous requirements for the dosimetry systems used for the verification and development of treatment. Among these requirements are high spatial resolution in 2D and/or 3D, high precision over a wide dose range, and correction of any quenching caused by, e.g., high linear energy transfer (LET). While some dosimetry systems with 3D capabilities exist, they rely on a chemical response to ionizing radiation and are thus inherently one-time use and suffer from LET quenching, and no 3D dosimeters have yet made their way to widespread clinical deployment. In this contribution, we present the latest efforts in our development of clinically relevant, reusable 2D and 3D optically-stimulated luminescence (OSL)-based dosimeters, featuring readout allowing for mapping of LET in 2D.

Material/Methods:

A novel laser-based optical readout system has been developed to retrieve 2D information from films and 3D information from bulk OSL-active materials. The working principle of the 3D system was to use a light sheet for stimulating OSL from a specific layer of an irradiated 3D dosimeter and measure the 2D distribution of the OSL emission using a CCD camera. By scanning the laser sheet through the volume of the dosimeter, the entire volume of the dosimeter could be read out and the acquired 2D images could be stacked to yield a 3D dose distribution. A cerium-doped yttrium oxyorthosilicate (YSO:Ce) crystal measuring 50x50x50 mm 3 was read out following irradiation by both photons and protons. The system also features a set of light-emitting diodes (LEDs), which were used for bleaching the 3D dosimeter and as a stimulating light source for the readout of 2D OSL-based films. A 100x110 mm 2 film consisting of a silicone matrix with embedded in-house-synthesized LiF and LiBaF3 nanoparticles was developed. Operating the LEDs in a pulsed mode, enabled high-temporal-resolution readout of the films facilitating a separation of the contributions from the two components due to their distinctly different OSL decay times. As the LET quenching behavior of the components was likewise found to be distinctly different, the ratio between the OSL signal from the two components could be used as a proxy for LET. The film was calibrated using a series of proton irradiations with known, homogeneous LET values.

Results: