S2016
Physics - Dose prediction/calculation, optimisation and applications for photon and electron planning
ESTRO 2026
treatment. For this study, no other simulation imaging was done aside from the CBCT for the initial animal. Subsequent animals underwent the same contrast- enhanced, gated CBCT for alignment and delivery only. OAR contours were rigidly transferred to the treatment-day CBCT and recontoured as needed. Dose was then recalculated on this dataset. OAR constraints were adapted from Knutson et al.(2). The plan was reviewed by a medical physicist and radiation oncologist. QA was performed using EPID gamma analysis and an IROC Houston phantom to perform end-to-end testing of the full workflow.
estimation. This first analysis demonstrated robustness of EQD against MR uncertainties, opening the door for combined evaluation and planning of radiotherapy and hyperthermia. References: [1] van der Zee J, et al. Comparison of radiotherapy alone with radiotherapy plus hyperthermia in locally advanced pelvic tumors. Lancet 2000;355:1119–25. [2] van der Zee J, González González D. The Dutch deep hyperthermia trial: results in cervical cancer. I J Hyperther 2002;18:1–12.[3] Franckena M, et al. Long- term improvement in treatment outcome after radiotherapy and hyperthermia in locoregionally advanced cervix cancer: an update of the Dutch deep
hyperthermia trial. I J Radiat Oncol Biol Phys 2008;70:1176–82.[4] van Leeuwen CM, et al.
Measurement and analysis of the impact of time- interval, temperature and radiation dose on tumour cell survival and its application in thermoradiotherapy plan evaluation. I J Hyperther2018;34:30–8. Keywords: Hyperthermia, Equivalent Radiation Dose, TCP Digital Poster 4893 Direct to Unit Large-Animal SBRT workflow using Contrast-Enhanced Gated CBCT Luke Marut 1 , Eric Morris 1 , Geoffrey Hugo 1 , Clifford Robinson 1 , Phillip Cuculich 2 , Pamela Samson 1 , Timothy Smith 2 , Stephanie Hicks 2 , Stacey Rentschler 2 , Brian Zenger 2 , Christian Zemlin 3 , Yao Hao 1 , Michael Prusator 1 , Guilherme Ferreira 1 , Nels Knutson 1 1 Radiation Oncoloy, Washington University, St Louis, USA. 2 Cardiology, Washington University, St Louis, USA. 3 Surgery, Washington University, St Louis, USA Purpose/Objective: Large-animal studies of stereotactic arrhythmia radiotherapy (STAR) are essential to validate mechanisms suggested by murine models but are constrained by cost, logistics, and access to clinical equipment(1). We implemented a single-platform porcine STAR workflow on an o-ring linac using contrast-enhanced CBCT and end-exhalation gating and evaluated whether this streamlined workflow could achieve target coverage, OAR sparing, and QA standards. Material/Methods: The initial animal was intubated, sedated, and imaged with IV contrast-enhanced, manually gated CBCT on the linac to generate a template 6-MV FFF, 4-arc VMAT plan. The transmural-scar CTV and a 5 mm PTV expansion were defined on this dataset with margins for inter-animal variability. The prescription was 25 Gy to the PTV and 35 Gy to the CTV in a single fraction. This initial animal was a control and did not receive
Results: A total of three animals were successfully treated with this workflow. Templated PTV and CTV volumes were 98.7 cc and 35.2 cc. The template plan achieved CTV D95%=35.52 Gy and PTV D95%=26.17 Gy. OAR doses were within outlined constraints. On treatment-day CBCT recalculations were median PTV D95%=25.88 Gy and median CTV D95%=35.13 Gy. The median Dmax was 42.48 Gy, confined to the CTV. Again, OAR limits were achieved. Highest observed values across all three treated animals were: esophagus Dmax=3.64 Gy, stomach Dmax=5.47 Gy, spinal cord Dmax=2.29 Gy, liver Dmax=2.36 Gy, lungs mean dose=2.65 Gy, and heart–PTV mean dose=4.95 Gy. Beam-on time was 12 minutes, 22 seconds for all treatments. EPID gamma analysis achieved gamma value 97.4% (3%/3mm). IROC phantom dosimetry passed, with TLD measurements within 2% of expected and film measurements passing with a 100% gamma index
(7%/5 mm).
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