ESTRO 2025 - Abstract Book

S3344

Physics - Intra-fraction motion management and real-time adaptive radiotherapy

ESTRO 2025

Results:

PSD1 and PSD2 were as follows. 1. The total accumulated doses received by the PSDs are close to the planned dose [Fig2a] for static and gated cases with a dose difference of [0.7-5.9]%, while a higher dose difference [4.3-11.2]% was reported for the motion case. These differences are consistent with the periodic displacement of the PSDs – around 2mm and 3mm in HF and AP direction, respectively. 2. The dose rates measured by the two PSDs are stable over time for the static case [Fig2b] but oscillate in phase with the waveform applied in the motion case [Fig2c], as expected for both cases. 3. For the gating case, we validated that the dose rates oscillate when the beam is on and drop to 0cGy/min periodically when the beam is off [Fig2d]. Consistent results were obtained for PSD3 and PSD4. Conclusion: We successfully demonstrated time-resolved and multi-point dose measurements in a beating heart phantom on the MR-linac.

Keywords: Real-time Dosimetry,Deformable Heart,MRI-guidance

References: [1] M. Mayinger et al 2020, Radiotherapy and Oncology 152, 203-207, DOI: j.radonc.2020.01.008 [2] P. Uijtewaal et al 2023, Phys. Med. Biol. 68, 04NT01, DOI: 10.1088/1361-6560/acb30c