S1667
Physics - Detectors, dose measurement and phantoms
ESTRO 2026
measurements at exact locations can be made with minimal perturbation of the beam (5).An electron treatment with a shielding mask was simulated with a field close to the eye of a phantom patient. A patch was produced to measure doses: at the eye under the mask, in the treatment field and across the penumbra of the field, Figure 1a.
A et al 2024. Exploring properties of 3D-Printed Bolus: Optimal choices for radiation therapy. Keywords: in-vivo, electron, TLD
Proffered Paper 3366 Online Anomaly Detection using Radiation Acoustic Imaging (iRAI) in Conventional and FLASH Proton Radiotherapy Ali Ajdari 1,2 , Glebys Gonzalez 3 , Maria Teresa Rodriguez Gonzalez 1,2 , Wei Zhang 4 , Jiyeon Park 5 , Ibrahim Oraiqat 6 , Xueding Wang 4 , Jan Schuemann 1,2 , Issam El Naqa 3 , Thomas Bortfeld 1,2 1 Department of Radiation Oncology, Massachusetts General Hospital, Boston, USA. 2 Department of Radiation Oncology, Harvard Medical School, Boston, USA. 3 Department of Machine Learning, Moffitt Cancer Center, Tampa, USA. 4 Department of Radiology, University of Michigan, Ann Arbor, USA. 5 Department of Radiation Oncology, University of Florida Health Proton Therapy Institute, Jacksonville, USA. 6 Department of Radiation Oncology, Moffitt Cancer Center, Tampa, USA Purpose/Objective: Ensuring precise delivery of radiation dose is of utmost importance in radiotherapy (RT), especially in high intensity/high dose rate settings where the price of even small deviations from planned delivery can be extremely high. Current dose verification methods operate on signals that are already delivered, preventing online error detection. We propose a proof-of-principle fast, fully automated in vivo dose monitoring and anomaly detection algorithm on real- time signals from Radiation Acoustic Imaging (iRAI)1,2 for online verification of conventional and FLASH proton radiation delivery. Material/Methods: A custom 2D planar matrix array (Imasonic; 32x32 elements, 0.35 MHz) recorded acoustic signals from incoming proton beams. Experiments were conducted on an oil phantom (Fig 1A) using (a) proton pencil beam generated from an IBA proton synchrocyclotron (230 MeV) at the University of Florida Proton Therapy Institute (UFPTI) and (b) an experimental FLASH pseudo-continuous beam (40 μs of 106 MHz micro- bunches; FLASH > 100 Gy/s) at the Massachusetts General Hospital (MGH). Two statistical anomaly detection (AD) algorithms were developed to automatically detect significant deviations and shifts from expected signal morphology: a timeseries (1D) optimal change point detection (OCD)3 algorithm (Fig 1B) and a 2D (full array) matrix comparison using single value decomposition (SVD) and Shannon entropy. The algorithms’ performance was evaluated in terms of (1) automatic localization of the Bragg peak
Figure 1a. Bead Placement in the Patch, 1b. Patch and Mask on a patientMeasurements were made on the phantom with a 9MeV beam on two Varian accelerators. 2Gy was delivered to the position of maximum dose on the Central Axis..This established sufficient confidence for a patch dosimeter to be used clinically for in-vivo measurements for a treatment field in close proximity to the patient’s eye. The prescribed dose to the skin was 5Gy. Results: The Phantom and patient’s doses are given in Table1. The Patch conformed and fitted well to the Phantom. Careful fitting of the Mask ensured the Patch and the dosimeters were in the required location.
In clinical use, the routine surface scan taken to produce the plaster cast for the shielding mask was used. The patch was designed, printed, loaded with dosimeters and available at the Treatment Centre within 48 hours. The Patch was located on the patient with ease and the dosimeter location visually verified, Figure 1b. The measurements are given in Table1. Conclusion: In-vivo electron treatment measurement with micro- bead dosimeters embedded into a 3D printed surface patch is accurate and expedient. References: 1. Masterson et al 2022. A review of micro silica beads in radiation dosimetry applications.2. Jafari et al 2024. Characterisation of micro silica glass bead TLDs in electron radiotherapy.3. Barley, S et al 2024. Improving patient experience with surface scanning for a printed mould.4. Mills, JA 2024. Producing low melting point alloy masks with 3D printing. 5. Ciobanu,
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