ESTRO 2024 - Abstract Book

S3208

Physics - Detectors, dose measurement and phantoms

ESTRO 2024

Moritz Schneider 1,2 , Joshua Schilz 2 , Michael Schürer 1,3 , Sebastian Gantz 1,4 , Anne Dreyer 4 , Gerd Rothe 5 , Falk Tillner 1,4,5 , Elisabeth Bodenstein 1,4 , Felix Horst 1,4 , Elke Beyreuther 1,2 1 OncoRay, National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus- Technische Universität Dresden- Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany. 2 Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiation Physics, Dresden, Germany. 3 National Center for Tumor Diseases Dresden (NCT/UCC), Germany: German Cancer Research Center (DKFZ), Heidelberg, Germany, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany; Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Dresden, Germany. 4 Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiooncology - OncoRay, Dresden, Germany. 5 Department of Radiotherapy and Radiation Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany Proton therapy is a popular treatment modality in radiooncology due to its high spatial dose conformity compared to conventional radiotherapy, allowing it to spare normal tissue. Although patient treatment is already established, there is still a need for preclinical in vivo experiments on proton RBE, regional sensitivities and new treatment modalities such as FLASH. A well-established setup for proton irradiation at the University Proton Therapy Dresden (UPTD) [1,2] , as well as a separate setup for photon irradiation of small animals [3] , have already facilitated numerous successful experiments [4,5,6,7] . However, the new challenge was to establish a setup capable of accommodating both proton and photon irradiation within the same framework to enable comparable experiments. Additionally, the incorporation of onboard imaging minimizes experimental uncertainties and reduces movements due to positioning changes between imaging and irradiation, ensuring the reproducibility of experimental investigations [8] . Here we describe the establishment of SAPPHIRE, a setup using the small animal imaging and irradiation device SmART+ IB for preclinical image-guided proton and photon therapy experiments to bridge the gap between preclinical studies and clinical applications. Purpose/Objective:

Material/Methods:

The SmART+ IB features a 225 kV X-ray tube, a flat panel detector, gantry, and X-Y-Z animal stage as well as an adaptable window for integrating a proton beam (see Figure).

Four CBCT imaging protocols were evaluated for image quality including CBCT homogeneity within phantoms, contrast-to-noise ratio (CNR), and visibility of notable structures in a mouse skull. Additionally, the imaging dose per mouse was quantified. For mouse brain irradiation with protons, it is necessary to open the window and install the in-house built aluminum collimator and polymethylmethacrylat (PMMA) range shifter. Their placement was optimized trough Monte Carlo simulations to minimize scattered dose distributions. To position all components precisely, a custom-made QA phantom was employed to ensure the accurate alignment of the proton beam, collimator, and mouse target before each experiment.