ESTRO 2021 Abstract Book

S461

ESTRO 2021

criteria of 1 %/1mm and 10% threshold were used to better discriminate differences among plans. For every plan the average of the passing rates, mean gamma values, maximum gamma values and percentage of points with gamma superior to 0.8 and 1.2 of each field, were calculated. Trajectory logs of the 5065 treatment fractions delivered for all plans were analyzed with home-made Python scripts, based on the pylinac package [https://pylinac.readthedocs.io/en/stable/]. Maximum and average RMS errors, 95 th percentile of MLC errors, and leaf speed (maximum, mean, median and 95 th percentile) were extracted for each log, and averaged for the whole treatment. Mean pre-treatment QA parameters were compared with mean MLC parameters. Results The table shows the results obtained in the gamma analysis using 1%/1 mm criteria.

The mean passing rate for all treatment sites was above 90% with a 1%/1 mm criteria. Although differences were found amongst different class solution for each pre-treatment QA parameter, none of them can be detected with less restrictive gamma criteria.

No point-by-point correlation was found between RMS and patient-specific QA parameters. Nevertheless, the average values of the mean maximum RMS are correlated (r 2 =0.92) with the gamma passing rates for each treatment site. Similar correlations were found for the rest of MLC and patient specific QA parameters. Conclusion A solid correlation between MLC performance and pre-treatment QA parameters has been found for different class solutions. MLC and pre-treatment QA parameters have distinct average values depending on the class solution. These parameters can help to develop and organize class solutions. PH-0597 Commissioning and clinical implementation of myQAiON for proton independent dose calculation (IDC) L. Grevillot 1 , R. Dreindl 1 , R. Fayos-Solà Capilla 2 , A. Elia 1 , M. Bolsa-Ferruz 1 , J. Gora 1 , A. Amico 1 , F. Padilla- Cabal 3 , A. Carlino 1 , M. Stock 1 1 MedAustron Ion Therapy Center, Medical Physics, Wiener Neustadt, Austria; 2 Hospital Universitario La Princesa, Medical Physics and Radiation Protection, Madrid, Spain; 3 Medical University of Vienna / AKH, Medical Physics, Vienna, Austria Purpose or Objective Measurement-based Patient Specific QA (mPSQA) is known to be a bottleneck, which limits the patient treatment capacity of Light Ion Beam Therapy (LIBT) facilities. In addition, IDC-based PSQA is more sensitive than mPSQA in identifying dose calculation issues from the TPS [1]. So far and to our best knowledge, the use of IDC for scanned ion beam delivery systems was only performed in addition to mPSQA. We believe that IDC- based PSQA is a valid measure to substitute mPSQA, assuming LIBT facilities are set-up with a comprehensive beam delivery and patient alignment QA program. This work presents the commissioning and clinical implementation of myQAiON (IBA-dosimetry) for scanned proton beam delivery systems at our facility. Materials and Methods myQAiON version 1.2 was installed, configured and accepted on site. Commissioning was divided in 3 parts: 1) Dosimetric commissioning (ranges, beam sizes, cubic/irregular targets in water); 2) Hounsfield Unit (HU) curves definition and validation against Water Equivalent Thickness (WET) measurements in tissue-equivalent