ESTRO 2024 - Abstract Book

S3256

Physics - Detectors, dose measurement and phantoms

ESTRO 2024

The images of the sphere in the first plan isocenter, showed similar results to the traditional WL, this suggest that this phantom can be used as a tool for this purpose.

Even using Exactrac the farer the BB is from the ISO the greater the deviation is between the radiation and the mechanical field.

When using treatment of multiple brain metastases with a single isocenter, this test must be performed in order to evaluate the concordance between the mechanical and the radiation field and decide if make greater PTV or decide that lesions that are at certain distances may need an extra isocenter[P1] .

Keywords: WL, Radiosugery, Linac

References:

Szweda H, Graczyk K, Radomiak D, Matuszewski K, Pawałowski B. Comparison of three different phantoms used for Winston-Lutz test with Artiscan software. Rep Pract Oncol Radiother. 2020 May-Jun;25(3):351-354. doi: 10.1016/j.rpor.2020.03.003. Epub 2020 Mar 4. PMID: 32214910; PMCID: PMC7083885.

P A K Oliver et al 2022 Biomed. Phys. Eng. Express 8 065005

1351

Proffered Paper

Absolute time-resolved in vivo dosimetry during proton Bragg peak FLASH irradiation of mice

Sky R Rohrer 1 , Eleni Kanouta 1 , Line Kristensen 1,2 , Brita S Sørensen 1,2 , Jacob G Johansen 1 , Per R Poulsen 1

1 Aarhus University Hospital, Danish Centre for Particle Therapy, Aarhus N, Denmark. 2 Aarhus University Hospital, Department of Experimental Clinical Oncology, Aarhus N, Denmark

Purpose/Objective:

Pre-clinical mouse studies have shown that ultra-high dose rate proton pencil beam scanning can effectively reduce normal tissue toxicity while maintaining tumour control (FLASH effect). However, these studies were limited to treatments in the entrance plateau of the proton beam, leaving the full potential of proton therapy untapped. To explore this further, new mouse studies were recently conducted in a spread-out Bragg peak (SOBP) in order to study the FLASH effect of acute and late toxicity: skin toxicity on the mouse foot (acute effect) and fibrosis around the foot joint (late effect). To validate accurate dose delivery during the mouse irradiations, time-resolved in vivo dosimetry was performed using a scintillation-based detector system. This process involved two key components: a dosimetric validation that the field was delivered with the intended dose and dose rate, and a geometric validation that the mouse legs were correctly placed within the high-dose area of the field.