ESTRO 2023 - Abstract Book

S1418

Digital Posters

ESTRO 2023

Results Daily QA time was a total of 10-15 minutes. Setting parameter of 8 pF was selected for the routine setup and measurement. The energy characteristic of range and distal fall off of 100 MeV, 150 MeV and 200 MeV showed the difference of about 2 mm with the beam data commissioning results. Spot and field homogeneity were compared with EBT3 film measurement and the differences were within 2%. Proton beam coincidence was well-defined and accurate compared to the Logos system. Three months monitoring showed the constancy of the daily QA results and were within the tolerances recommended by the AAPM TG 224 reports Conclusion The QA tool was successfully commissioned. Implementation of the QA device for proton pencil beam scanning was fast and suitable in routine daily QA procedures, and results were reliable to monitor the constancy of proton therapy system.

PO-1705 Cone beam CT-based dose recalculation as plan-specific QA in online adaptive radiotherapy

G. Razinskas 1 , R. Schindhelm 1 , K. Breuer 1 , S. Weick 1 , J. Tamihardja 1 , S. Wegener 1

1 University Hospital Wuerzburg, Department of Radiation Oncology, Wuerzburg, Germany

Purpose or Objective On-couch adaptive radiotherapy provides the ability to alter treatment plans on a daily basis to account for interfractional anatomical variations. The AI-driven Varian Ethos solution is able to deliver personalized patient care based on daily cone beam computed tomography (CBCT) images. Artifacts and uncertainties in Hounsfield Units (HU) due to photon scattering are known limitations of this imaging modality making its use for direct dose calculation challenging. To this end, a synthetic CT (sCT) is utilized by employing a CBCT-based deformable image registration of the planning CT (pCT) with its high image