S1668
Physics - Detectors, dose measurement and phantoms
ESTRO 2026
Conclusion: We have developed and tested a fast, fully automatic method for detecting incidental errors in proton dose delivery using 1D (timeseries) and 2D (matrix decomposition) anomaly detection techniques, enabling online dose verification and error detection in advanced, high-stake proton and proton FLASH RT. References: 1. Zhang, W. et al. Real-time, volumetric imaging of radiation dose delivery deep into the liver during cancer treatment. Nature Biotechnology 2023 41:841, 1160–1167 (2023).2. Oraiqat, I. et al. An Ionizing Radiation Acoustic Imaging (iRAI) Technique for Real- Time Dosimetric Measurements for FLASH Radiotherapy. Med Phys47, 5090 (2020).3. Verzelen, N., Fromont, M., Lerasle, M. & Reynaud-Bouret, P. Optimal Change-Point Detection and Localization. Ann Stat51, 1586–1610 (2020). Keywords: Acoustic imaging, anomaly detection, proton, FLASH
within the iRAI signal and (2) real-time error detection due to dose delivery changes. Results: Experimental variables included changes in peak-to- array distance (5–15 cm), beam energy (70–150 MeV), and beam current (0.05–0.5 nA). Acoustic measurements included Bragg peaks at 13, 11, 9, and 2 cm and different distances between the beam-to- transducer through the target medium. Figure 2A shows the automatic dose localization within the 1D (averaged) proton FLASH signal using the OCD method, decomposing the signal into dose entrance, dose deposition at Bragg peak, and dose exit(bounce back) phases. Figure 2B shows the performance of the AD methods in distinguishing between normal (random noise) and abnormal (systematic errors) deviations. Across 27 paired (expected vs. observed) experiments, the AD algorithm successfully detected 25 of the deviations in the dose delivery pattern, yielding 93% error detection accuracy.
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Comparative Assessment of microDiamond, microMOSFET and Gafchromic Film for Small Animal Irradiator Dosimetry Md Nurul Amin 1 , Rita Chen 2 , Bern Norrlinger 1 , Raanan Marants 1 , Naz Chaudary 2 , Patricia Lindsay 1 , Jan Seuntjens 1,3 1 Radiation Physics, Princess Margaret Cancer Center, University Health Network, Toronto, Canada. 2 STTARR Innovation Centre, Princess Margaret Cancer Research Tower, University Health Network, Toronto, Canada. 3 Department of Radiation Oncology and Medical Biophysics, University of Toronto, Toronto, Canada Purpose/Objective: Small animal image-guided irradiation systems play a crucial role in preclinical and translational radiotherapy research. In recent years, their use has become increasingly widespread. However, small-field dosimetry presents significant challenges, as the use of inappropriate detectors can lead to reduced measurement accuracy. When selecting a suitable detector for small-field dosimetry, several factors must be considered, including long-term stability, linearity with respect to dose and dose-rate, as well as energy and angular dependence. In this study, a comparative dosimetric assessment was performed using a microDiamond detector, microMOSFET, and Gafchromic film for a small animal irradiator. Material/Methods: Measurements were performed using a 225kVp photon beam from a small-animal image-guided irradiation system. The Gafchromic film, microMOSFET, and microDiamond detectors were
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