3-dimension scintillation dosimetry for small irradiation fields in proton therapy

by My Hoang Hoa BUI

Due to physical advantages compared to conventional method of radiotherapy with external photon beams, protons has been considered as a better resort in several types of cancer treatment. The distinctive Bragg curve of protons’ dose profile when traversing materials allows them to increase local dose on the targeted tumor but at the same time spare surrounding critical structures [1]. However, existing uncertainty in treatment planning restricts the full exploitation of proton beams, especially in case of small volume targets [2].

Modeling Platform for Radiotherapy (Plateforme Modélisation pour la RT (PMRT) in French) is a project aiming to contribute to the development of proton therapy, mainly in the mission of building and developing a new detector for small irradiation fields. This ongoing studied detector, known as Scicopro, potentially yields better attributes than current proton beam detectors, including faster quality checks and better spatial resolution.

Thanks to previous work, the dosimetry system has shown a satisfactory agreement in the beam characteristics between planned and delivered beams. In particular, the beam location and intensity measurement were both under the threshold of tolerance, i.e. lower than 1 mm for position and lower than 2% for the delivered dose [3]. However, it was also indicated that the deviation in the reproducibility examination became more significant when the dose distributed was lowered.

This internship is a continuity of the PMRT project, which desires to improve the assessment of pencil beams irradiated in the low energy region and concurrently to optimize the computational complexity. Besides solving two underlying problems that are ignored in the previous study, namely hot pixels survival after filtering and optical reflections, new approaches are proposed based on specific light distribution on each view acquired by the camera in order to better quantify the beam measurement.

[1] “Acceptance tests and quality control (QC) procedures for the clinical implementation of intensity modulated radiotherapy (IMRT) using inverse planning and the sliding window technique: experience from five radiotherapy departments”; Van Esch, J. Bohsung, P. Sorvari, M. Tenhunen, M. Paiusco, M. Iori, P. Engström, H. Nyström, and D. Huyskens; Radiotherapy and Oncology, 2002
[2] “Material assignment for proton range prediction in Monte Carlo patient simulations using stopping-power datasets”; Felicia Fibiani Permatasari, Jan Eulitz, Christian Richter , Patrick Wohlfahrt and Armin Luhr, Physics in Medicine and Biology.
[3] « Dosimetrie par scintillation en 3 dimensions pour le controle des petits champs d’irradiation en protontherepie”; Erwan MAINGUY; Année Universitaire 2020-2021.