S2124
Physics - Inter-fraction motion management and daily adaptive radiotherapy
ESTRO 2026
Digital Poster 1222
Implementation and first clinical experience of in vivo dosimetry using EPID-based systems in head and neck and lung radiotherapy clara navarro ibarra, Francisco Clemente Gutiérrez, Maria Paz García de Acilu Laa, Eduardo Pardo Pérez, Miguel Ángel Díez Gallego, Noelia SolísPreciado, José ángel Merino Gestoso, Angel Forner Forner, María Luisa Chapel Gómez, Ángela Fonseca Siles, Samuel Díaz del Álamo Sánchez Crespo, Isabel Castro Rizos, María Mercedes Fustes Sanjuán Radiotherapy, University Hospital Toledo, Toledo, Spain Purpose/Objective: To report the implementation and first clinical results of in vivo dosimetry (IVD) using the SunCHECK PerFRACTION (Sun Nuclear) EPID-based system for patients treated with volumetric modulated arc therapy (VMAT) in head and neck (HN) and lung cancer. The aim was to evaluate the pass rates, investigate potential correlations with plan complexity, and assess the ability of the system to detect relevant setup or anatomical variations during treatment. Material/Methods: IVD was prospectively implemented for 40 patients: 20 HN and 20 lung, all treated with VMAT. Each patient received 2–3 arcs, resulting in a total of approximately 100 treatment arcs analyzed. Local gamma analysis was performed with the following criteria: 5%/3 mm, 95% pass rate, and 20% dose threshold for HN; and 5%/5 mm, 95% pass rate, and 20% threshold for lung. Plan complexity was quantified using the Plan Average Modulation (PAM) index. Deviations were analyzed in relation to anatomical or setup changes detected during treatment (e.g., patient weight loss, shoulder positioning, or tumor shrinkage). Results: The average gamma passing rate (5%/5 mm, local 20%) for patients without anatomical or setup issues was 98.2% ± 0.7 for lung and 97.6% ± 0.2 for HN cases. The PAM was 0.66 ± 0.9 for HN and 0.56 ± 0.13 for lung treatments. When applying a common 5%/5 mm local gamma analysis, more complex plans tended to show slightly lower passing rates in both HN and lung groups. However, these differences may be partly related to the higher inhomogeneity and steeper dose gradients typical of HN rather than to plan modulation itself. In HN cases, reduced gamma values were occasionally associated with unblocked or mispositioned shoulders and patient weight loss, confirmed by image guidance. In lung cases, changes in lesion size or density during treatment were identified as possible sources of discrepancy. Figure 1 and table 1 illustrates the gamma results of a lung lesion that decreased in volume during treatment.
Conclusion: Our findings emphasise the feasibility of an MR-guided daily adaptive particle therapy workflow for liver SBRT treatments, enabling a more precise daily imaging of the lesion. We have shown that the target coverage achieved with a DIR-generated dCT is in accordance with a daily CT image, with some deviations observed on the near-maximum dose delivered to the OAR. In the future, our goal is to transfer this automated pipeline to a shuttle-based “quasi-online” MR-guided adaptive workflow. References: [1] P. Hoegen-Saßmannshausen et al., ‘Carbon ion radiotherapy of hepatocellular carcinoma provides excellent local control: The prospective phase I PROMETHEUS trial’, JHEP Rep, vol. 6, no. 6, p. 101063, June 2024, doi: 10.1016/j.jhepr.2024.101063.[2] E. Gkika et al., ‘Excellent local control and tolerance profile after stereotactic body radiotherapy of advanced hepatocellular carcinoma’, Radiat Oncol, vol. 12, no. 1, p. 116, July 2017, doi: 10.1186/s13014-017- 0851-7.[3] O. Weistrand and S. Svensson, ‘The ANACONDA algorithm for deformable image registration in radiotherapy’, Med Phys, vol. 42, no. 1, pp. 40–53, Jan. 2015, doi: 10.1118/1.4894702. Keywords: MR-guided particle therapy, Adaptive liver SBRT
Made with FlippingBook - Share PDF online