ESTRO 2023 - Abstract Book

S1412

Digital Posters

ESTRO 2023

attached to the moving part of the accelerator. The analysis of the recorded images with the software allows for determining the average center (isocenter) of rotation and the curve along which the rotating element moves. The precision of the system has been verified by measurements carried out with a device simulating the rotation of the arm, collimator, and therapeutic table. The results of the accelerator’s isocenter measurements are presented on a 3D chart. We performed isocenter measurements for 5 linear accelerators installed at the National Research Institute. Results The optical system enables determination of isocenter with the accuracy of < 0.1 mm. The diameter of the isocenter spheres for all accelerators installed at the NRI did not exceed 1.0 mm. The smallest isocenter sphere was obtained for Edge accelerator. In Fig. 1 the positions of actual rotation axis for gantry, collimator and treatment table for Edge accelerator are presented in 3D. For other accelerators, Clinac 2300 CD and TrueBeam, however, the diameter of isocenter spheres were less than 1 mm, little larger changes of axes of therapeutic table rotation were obtained. The measurement time of accelerator’s isocenter was shorter than 20 minutes.

Fig 1 Edge’s sphere isocenter for gantry (red), treatment table (blue) and collimator (green).

Conclusion All our accelerators fulfill the requirements of the AAPM TG 142 recommendation, the isocenter spheres were < 1mm, however, mechanically the most precise was the Edge accelerator. All accelerators had a similar deflection of the arm. The difference was obtained for the axes of rotation of treatment tables. The optical system enables to the measurement of the isocenter with a precision of better than 0.1 mm within 20 minutes.

PO-1701 STereotactic Arrhythmia Radioablation in Europe–Treatment Unit QA Audit of the STOPSTORM Consortium

Ł . Dolla 1 , A. Grz ą dziel 1 , A. Bekman 2 , S. Blamek 3 , T. Latusek 3 , M. Miszczyk 4 , J.J. Verhoeff 5 , M. Grehn 6 , O. Blanck 6

1 Maria Sk ł odowska-Curie National Research Institute of Oncology, Gliwice branch, Radiotherapy Planning Department, Gliwice, Poland; 2 Maria Sk ł odowska-Curie National Research Institute of Oncology, Gliwice branch, Medical Physics Department, Gliwice, Poland; 3 Maria Sk ł odowska-Curie National Research Institute of Oncology, Gliwice branch, Radiotherapy Department, Gliwice, Poland; 4 Maria Sk ł odowska-Curie National Research Institute of Oncology, Gliwice branch, IIIrd Department of Radiotherapy and Chemotherapy, Gliwice, Poland; 5 University Medical Center Utrecht, Department of Radiotherapy, Utrecht, The Netherlands; 6 University Medical Center Schleswig-Holstein, Department of Radiation Oncology, Kiel, Germany Purpose or Objective In patients with refractory ventricular tachycardia (VT), STereotactic Arrhythmia Radioablation (STAR) showed promising results for otherwise untreatable patients. The STOPSTORM project coordinates European efforts to validate STAR and refine protocols and guidelines for treatment harmonization. Major impact on harmonization results from treatment unit quality control procedures and we now present the current SBRT and STAR practice in Europe for machine and patient specific quality assurance (QA) based on a comprehensive audit survey. Materials and Methods The treatment unit QA audit survey included comprehensive items on machine characteristics and commissioning, dosimetric and geometric QA, imaging system QA, end-2-end tests and patient-specific plan verification. The audit was