ESTRO 2023 - Abstract Book

S636

Monday 15 May 2023

ESTRO 2023

Conclusion Our study confirms the pulmonary safety of breast 3D RT in CANTO RT, with an incidence of ≥ grade 3 RILI of 0.1% and all grade RILI of 2.4%. Further analysis in large cohorts with modern radiotherapy techniques such as IMRT are needed. Our results argue in favour of a dose constraint to the ipsilateral lung using the threshold of V30Gy<10-13%, especially in patients presenting pulmonary medical history. Pulmonary disease record should be taken into account for RT planning.

Proffered Papers: Detectors and dose verififcation

OC-0770 Anthropomorphic pancreas phantom with real-time breathing motion for Carbon-Ion radiotherapy C. Stengl 1,2,3 , I.D. Munoz 4,1,3 , K. Panow 1 , E. Arbes 4,5 , A. Neuholz 6 , S. Brons 6 , A. Runz 1,3 , G. Echner 1,3 , J. Liermann 6,7 , O. Jäkel 1,3,6 1 German Cancer Research Center, Medical Physics in Radiation Oncology, Heidelberg, Germany; 2 University of Heidelberg, Faculty of Medicine, Heidelberg, Germany; 3 National Center for Radiation Research in Oncology (NCRO), Heidelberg Institute for Radiation Oncology (HIRO), Heidelberg, Germany; 4 University of Heidelberg, Department for Physics and Astronomy, Heidelberg, Germany; 5 German Cancer Research Center, Biomedical Physics in Radiation Oncology, Heidelberg, Germany; 6 Heidelberg University Hospital, Heidelberg Ion Beam Therapy Center (HIT), Heidelberg, Germany; 7 Heidelberg University Hospital, Department of Radiation Oncology, Heidelberg, Germany Purpose or Objective Pancreatic cancer is the 7th leading cause of cancer related death and its five-year survival rate is only 9% [1]. Treatment options are scarce and the best curable chance is by resection. However, pancreatic cancer patients are often diagnosed in an advanced state, suffering from unresectable cancer. Therefore, novel therapeutic methods are required to improve survival rates. Recently, carbon-ion radiotherapy revealed a favorable oncological outcome [2]. However, results regarding this newly evolving technique are contradicting and require further analysis [3]. For this, we developed an anthropomorphic pancreas phantom with real-time breathing motion and realistic CT/MRI-contrasts for carbon-ion radiotherapy that allows investigating motion induced uncertainties of the delivered dose. Materials and Methods The proposed pancreas phantom resembling the abdomen, contains a deformable diaphragm and peritoneum, a pancreas, two kidneys, a duodenum and a spine segment (Fig. 1 A-D). 3D printed pancreas and kidney models were prepared with NiDTPA-KCl-agarose mix [4] to achieve human-equivalent CT and MRI contrasts. The duodenum was 3D printed with elastic material to enable morphological changes during emptying. Breathing motion with an amplitude of 10mm, 20mm and 30mm was applied by means of a computer-controlled hydraulic system to quantify organ motion. Carbon-ion irradiation was realized with a 4Gy (RBE) single fraction irradiation schedule to resemble standard patient plan geometry. For dosimetric measurements, a PinPoint ionization chamber and EBT3 films were inserted in the organs via an easy plug-in mechanism. Thereafter, breathing motion with 30mm amplitude was compared with static setup during irradiation. Results Our pancreas phantom presented reproducible motion for the breathing patterns with increasing amplitude. The pancreas motion revealed (3.98±0.36)mm, (11.38±0.41)mm and (18.19±0.44)mm for 10mm, 20mm and 30mm input amplitude, respectively, presenting a linear fit with an R ² of 0.996 (Fig. 1 E, F). Therewith, any motion amplitude can be calculated and applied according to individual patient pancreas motion. By clearing the duodenum, its volume decreased by 37%. Measurements with the ionization chamber revealed dose deviations of 15% during pancreas motion, which was significantly higher than in static case (0.26%). Also with films, inhomogeneous dose distributions at the target site were observed.