ESTRO 2024 - Abstract Book

S4193

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

ESTRO 2024

As correct range prediction is a crucial requirement for plan adaptation, PGI can serve as an online treatment verification tool which is highly desirable in an online-adaptive proton therapy workflow. Furthermore, the results indicate that PGI could also be used to detect range prediction errors resulting from uncertainties in CT numbers of CBCT data. We are currently extending the study to patient data.

Keywords: prompt-gamma imaging, online-adaptive PT, CBCT

References:

[1] E. Sterpin et al., “Physics in Medicine & Biology Analytical computation of prompt gamma ray emission and detection for proton range verification,” Phys. Med. Biol, vol. 60, pp. 4915–4946, 2015, doi: 10.1088/0031 9155/60/12/4915.

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Dosimetric Impact of intra- and inter-fraction motion in liver pencil beam scanning proton therapy

Saber Nankali 1,2 , Esben Schjødt Worm 3 , Jakob Borup Thomsen 1 , Line Bjerregaard Stick 1 , Morten Høyer 1 , Britta Weber 1,3 , Hanna Rahbek Mortensen 1 , Per Rugaard Poulsen 1,3 1 Aarhus University Hospital, Danish Centre for Particle Therapy, Aarhus, Denmark. 2 Aarhus University, Department of Clinical Medicine, Aarhus, Denmark. 3 Aarhus University Hospital, Department of Oncology, Aarhus, Denmark

Purpose/Objective:

Hepatocellular carcinoma (HCC) patients with cirrhosis face high risks of radiation induced liver disease, necessitating minimal liver tissue dose [1]. Pencil-beam-scanning (PBS) proton therapy is favored over photon-therapy for HCC treatment due to its superior dose precision [2]. However, tumor motion monitoring is not well-established for proton therapy. In this study, we monitor tumor motion during HCC PBS proton therapy and investigate the dosimetric impact of both intra-fraction tumor motion and inter-fraction anatomical changes.

Material/Methods:

Ten HCC patients received 58GyRBE (n=9) or 67.5GyRBE (n=1) gated proton therapy in 15 fractions. A 3-field IMPT plan was made on the exhale phase of a 10-phase 4DCT using an iCTV that encompassed the five phases closest to full exhale (50%-duty-cycle). Single-field robust optimization with ±5mm (LR/AP), ±7mm (CC) shifts and ±4.5% range uncertainty was applied. A control 4DCT was recorded during the first and second treatment week. Daily setup was based on a CBCT in which the exhale positions of 2-3 implanted fiducial markers were matched with the planning CT. For all patients, a post-treatment control CBCT was acquired at 4-8 fractions in the same couch position as the treatment. For patient 6-10, a pre-CBCT was additionally acquired immediately before treatment in the same couch