ESTRO 2025 - Abstract Book

S3053

Physics - Image acquisition and processing

ESTRO 2025

3463

Digital Poster Beam hardening and accuracy quantification of virtual monoenergetic images for dual-energy CT and photon-counting CT Lasse Bassermann 1 , Kyriakos Fotiou 1 , Jens Edmund 2 , Stine Elleberg Petersen 1 , Jesper Thygesen 3 , Weronika Elżbieta Olech 4 , Ludvig P Muren 1 , Vicki T Taasti 1 1 Danish Centre for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark. 2 Department of Oncology, Herlev and Gentofte University Hospital, Herlev, Denmark. 3 Department of Clinical Engineering, Aarhus University Hospital, Aarhus, Denmark. 4 Department of Radiology, Herlev and Gentofte University Hospital, Herlev, Denmark Purpose/Objective: CT scans form the basis for treatment planning in proton therapy. The CT numbers are dependent on their position in the body and the patient size due to beam hardening. This study investigated the influence of beam hardening in virtual monoenergetic images (VMIs) as well as VMI CT number accuracy for different dual-energy CT (DECT) acquisition modes as well as photon-counting CT (PCCT). Material/Methods: The Gammex Advanced Electron Density phantom, simulating the abdomen and head of an adult patient, was scanned at different DECT scanners in different modes, including Twin-Beam (TB), Dual-Spiral (DS), and Dual-Layer (DL) operated at different tube voltages, as well as PCCT. In each scan mode, four different bone inserts were scanned in different insert positions and phantom sizes (Figure 1A). VMIs were created with vendor software in steps of 10 keV from 50 to 190 keV. Beam hardening was evaluated as the averaged difference in CT numbers for the different insert configurations. Moreover, the VMI accuracy was evaluated as the root-sum-square of the difference between measured and theoretically calculated CT numbers, with the latter being calculated using NIST data and insert composition.