ESTRO 2024 - Abstract Book

S3345

Physics - Detectors, dose measurement and phantoms

ESTRO 2024

Conclusion:

Time-resolved in vivo dosimetry during proton PBS therapy can be used to both determine the dose and give a 3D positional verification with submillimetre accuracy. This was used to explain the reason for an underdosage of six mice. Information that could be used to e.g. omit these mice. It should be noted that the determined position is for the detector, which must be related to the target in the mouse.

Keywords: In vivo dosimetry, scintillators, Time-resolved

References:

1 Kanouta E et al. Time-resolved dose rate measurements in pencil beam scanning proton FLASH therapy with a fiber coupled scintillator detector system. Med Phys. 2023 Apr;50(4):2450-2462.

2 Bortfeld T. An analytical approximation of the Bragg curve for therapeutic proton beams. Med Phys. 1997 Dec;24(12):2024-33.

2455

Digital Poster

A novel phantom to verify geometric accuracy of single-isocentre multiple-target SRS dose delivery

Jonathan M Lane, Pratik Samant, Harkirat Singh

Oxford University Hospitals NHS Foundation Trust, Radiotherapy Physics, Oxford, United Kingdom

Purpose/Objective:

Stereotactic Radiosurgery (SRS) typically features a very high dose per fraction and a small or zero PTV expansion from the clinical target(s). The geometric accuracy of dose delivery is therefore crucial for treatment efficacy and the protection of healthy tissues. The increasing prevalence of single-isocentre multiple-target (SIMT) treatment delivery for multiple brain metastases presents a particular challenge for Quality Assurance (QA): the measurement of the geometric accuracy of dose delivery in 3D for multiple targets simultaneously.

Material/Methods:

A novel phantom is presented for SIMT SRS QA that allows measurement of 3D geometric dose delivery error for multiple targets simultaneously by comparing the dose distribution on orthogonal radiochromic film pairs with the planned dose. The phantom is finitely configurable to simulate a wide range of clinically realistic metastasis distributions for up to ten targets and has been designed to be compatible with any treatment platform.