ESTRO 2025 - Abstract Book

S3615

Physics - Quality assurance and auditing

ESTRO 2025

Figure 2: EAM of “L”-insert with marked target in white (top) and target transfer to planning-CT with CARDIO-RT in axial, sagittal and coronal views (bottom). Conclusion: First full end-to-end-tests for STAR were performed with different treatment machines and different motion compensation strategies. Some adaptions are necessary for the next version of the customized dynamic-cardiac phantom to better fulfil the special requirements for this novel treatment.

Keywords: STAR, Ventricular Tachycardia, Quality Assurance

References: [1] Grehn et al. STereotactic Arrhythmia Radioablation (STAR): the Standardized Treatment and Outcome Platform for Stereotactic Therapy Of Re-entrant tachycardia by a Multidisciplinary consortium (STOPSTORM.eu) and review of current patterns of STAR practice in Europe. Europace. 2023 [2] Stevens et al. STereotactic Arrhythmia Radioablation (STAR): Assessment of cardiac and respiratory heart motion in ventricular tachycardia patients - A STOPSTORM.eu consortium review. Radiother Oncol. 2023 [3] Mayinger et al. Quality assurance process within the RAdiosurgery for VENtricular TAchycardia (RAVENTA) trial for the fusion of electroanatomical mapping and radiotherapy planning imaging data in cardiac radioablation. Phys Imaging Radiat Oncol. 2022

1455

Proffered Paper HDR brachytherapy end-to-end dose audit for CT/MRI-based cervical treatments using a novel phantom

with film, microDiamond and virtual structures Antony L Palmer 1,2,3 , Sarah Wilby 1 , Wojciech Polak 1

1 Medical Physics, Portsmouth Hospitals University NHS Trust, Portsmouth, United Kingdom. 2 Medical Physics and Biomedical Engineering, University College London, London, United Kingdom. 3 Physics, University of Portsmouth, Portsmouth, United Kingdom Purpose/Objective: NHS England Brachytherapy Service Specification [1] requires radiotherapy centres to have external dosimetry audit. A novel end-to-end brachytherapy dosimetry system has been developed with IPEM (Institute of Physics and Engineering in Medicine), to fulfil this need; uniquely using virtual structures, MRI or CT-based planning and allowing interstitial needles, a significant improvement on previous techniques [2,3]. The new system assesses TPS-planned to measured dose agreement, target coverage, and OAR avoidance. The system has been tested at three pilot sites, prior to a UK-wide dose audit. Material/Methods: The novel Solid Water (Gammex HE) phantom (fig. 1) uses two complementary dosimetry systems: 1) Two interlocking sagittal and coronal Gafchromic films (Ashland), covering CTV and OARs, and 2) Real-time point dose measurement using a microDiamond detector (PTW) at ICRU Point A. Film-dose analysed using triple channel dosimetry (FilmQAPro) was a) compared to TPS RTDose using isodose overlay and gamma calculation, and b) using 3D Slicer software [4,5] for CTV/OAR gamma, dose plane histograms (DPHs), and calculation of D90% and D0.02 sq cm (equivalent to D2 cc DVH for non-cubic structure). Characterisation of the microDiamond HDR response was also included.