ESTRO 2024 - Abstract Book

S4137

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

ESTRO 2024

Germany. 6 Department of Radiotherapy and Radiation Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany. 7 RaySearch Laboratories AB, Research, Stockholm, Sweden

Purpose/Objective:

Range deviations due to anatomical variations are a major limitation to proton therapy accuracy. The instantaneous evaluation of in vivo treatment verification data (e.g., from Prompt Gamma Imaging (PGI)) may reveal relevant deviations and trigger an online-adaptive proton therapy (OAPT) workflow. For example, if a deviation is detected for the first field delivery, the remaining fields may be adapted online considering current anatomy and the delivered dose from the first field in a so-called partial adaptation. In this study we investigated the potential of online partial adaptation triggered by PGI to recover the total planned fraction dose after the suboptimal dose contribution from the first delivered field. The new concept of PGI-triggered partial adaptation was simulated for selected prostate cancer patients whose PBS treatment had been monitored with PGI within a clinical study [1].

Material/Methods:

In the envisioned workflow (Fig.1), the fraction dose delivery is started after standard patient setup and is monitored by PGI. If PGI detects a relevant treatment deviation, supposedly during the first field delivery, the treatment is stopped, 3D in-room patient imaging is triggered and the delivered dose from the first field is calculated on the current anatomy. This suboptimal background dose is considered in the online adaptation of the remaining fields, specific for the delivery in the current fraction.

Data from 15 prostate cancer patients of the “Clinical study for the evaluation of Prompt gamma IMAging (PRIMA)” including in-room control CTs (cCTs) from 105 fractions with PGI measurements (201 fields) were available. For this