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Abstract

Pancreatic cancer is an aggressive tumor, with approximately 50 % of cases diagnosed at an advanced and metastasized stage and a five-year survival rate ranging only from 5 % to 10 %. Conventional therapies for this type of cancer encounter significant challenges due to pancreatic tumor resistance to radiation and complications arising from organ motion. To overcome these obstacles, this thesis proposes the combination of carbon ion radiotherapy (CIRT) and mini-beam radiotherapy (MBRT). However, both methods are susceptible to organ motion, therefore it is essential to investigate its impact on dose distribution, simultaneously considering the target and the organs at risk (OARs). An anthropomorphic abdominal Pancreas Phantom for Ion beam Therapy (PPIeT) was developed aiming at investigating the organ motion impact. Constructed from 3D-printed anatomical structures with realistic imaging contrasts for CT and MRI, PPIeT can simulate breathing-induced organ motion and gastrointestinal movement. Different dosimeters, including ionization chambers and radiochromic films, were employed to measure doses within the pancreatic tumor and OARs, including the duodenum, kidneys, spine, and spinal cord. In parallel, an affordable and versatile mini-beam collimator was constructed using a 3D-printed scaffold to position metal plates for various configurations. The performance of the mini-beam collimator was validated during in vitro studies with x-ray irradiations. Subsequent irradiations of PPIeT involved conventional and spatially fractionated CIRT during different breathing-induced organ motion conditions. For conventional irradiation of PPIeT with CIRT a significant under-dosage of the tumor was observed when breathing was applied, while dose fluctuations in the OARs varied. When using the mini-beam collimator, precise mini-beam pattern generation was achieved, with an accuracy higher than 98 % for the 1 mm peak and 1 mm valley configuration. This configuration was selected for irradiating PPIeT with carbon ions, leading to uniform irradiation of the tumor even during organ motion. However, organ motion blurred mini-beam patterns within the kidneys, potentially compromising the tissue-sparing mini-beam effect. This research contributes to advance carbon ion-based cancer treatments, highlighting the need for tailored strategies considering motion-induced risks in pancreatic cancer radiotherapy.