ESTRO 2024 - Abstract Book

S3181

Physics - Detectors, dose measurement and phantoms

ESTRO 2024

the dose rate. But if we focus on one dose rate and one probe, we notice that the signals for all the energies are not superimposed. This underlines the effect of Scintillation Quenching [2].

Conclusion:

The small diameter of the fiber could permit a high spatial resolution, but by decreasing the sensitive volume we get a signal that is more sensitive to the background noise. We can measure entrance dose rate with silica fiber because the signal is linear with flux. As the energy of the proton changes with the penetration depth, the dependence in energy needs to be corrected if we want to measure Bragg peak properly. Next step is to investigate the response with high dose rate up to 100 Gy/s.

Keywords: Dosimetry, Proton, Optical fiber

References:

[1] J. Vidalot et al., ‘Monitoring of Ultra-High Dose Rate Pulsed X-ray Facilities with Radioluminescent Nitrogen-Doped Optical Fiber’, Sensors, vol. 22, no. 9, Art. no. 9, Jan. 2022, doi: 10.3390/s22093192.

[2] L. Archambault et al., ‘Characterizing the response of miniature scintillation detectors when irradiated with proton beams’, Phys. Med. Biol., vol. 53, no. 7, pp. 1865–1876, Apr. 2008, doi: 10.1088/0031-9155/53/7/004.

159

Digital Poster

Measurement of output factor for Cyberknife using scintillation dosimetry and deep learning

Geoff Heyes 1 , Jeremy Ocampo 2 , Hami Dehghani 3 , Tim Scanlon 2 , Simon Jolly 2 , Adam Gibson 4

1 Queen Elizabeth Hospital Birmingham, Radiotherapy Physics, Birmingham, United Kingdom. 2 University College London, Physics and Astronomy, London, United Kingdom. 3 University of Birmingham, School of Computer Science, Birmingham, United Kingdom. 4 University College London, Medical Physics and Biomedical Engineering, London, United Kingdom

Purpose/Objective:

We have developed a system to enable fast and efficient verification and quality assurance of small field (<30mm diameter) radiotherapy data without the need for an ionisation chamber. We analyse images of the light produced in a scintillating sheet when exposed to megavoltage radiotherapy x-rays of varying beam diameters. The system can accurately measure output factors for a CyberKnife system utilising fixed collimator diameters of 5mm to 60mm, and compare profiles and depth-dose measurements against reference data acquired classically with a small field detector in a watertank. This image based acquisition technique, which utilises machine learning to process, can