ESTRO 2023 - Abstract Book

S1421

Digital Posters

ESTRO 2023

systematic positioning errors at the gamma criteria LA2%/2mm while the other criteria gave values above 90%. Works are in progress: to study the dosimetric impacts on conformity/homogeneity indices and the 3D GPR of each organ; to perform portal imager measurements on the TrueBeam and TrueBeam STx; to analyze the correlations between the results of pretreatment controls and all these dosimetric indices combined with a predictive approach.

PO-1707 Use of an automated software module for monthly routine Machine QA tests

E. Bonanno 1 , G. Borzì 2 , N. Cavalli 2 , M. Pace 2 , G. Stella 3 , C. Marino 2

1 Humanitas-Istituto Clinico Catanese, Medical Physics Department, Misterbianco (CT), Italy; 2 Humanitas Istituto Clinico Catanese, Medical Physics Department, Misterbianco (CT), Italy; 3 University of Catania, Physics and Astronomy Department E. Majorana, Catania, Italy Purpose or Objective The goal of this work is to investigate the feasibility of implementing an automated module of a commercial software for monthly routine Linac QA tests. Materials and Methods The AAPM TG 142 report is a reference document which includes recommendations for general Quality Assurance (QA) tests for medical linear accelerators. DoseLab software includes an AutoQA module for users to run TG-142’s Machine QA tests in an automated sequence. The execution of the individual monthly tests (without DoseLab) is compared with AutoQA in terms of time consuming, reproducibility, additional data and user friendliness. Results The total time required was 195 minutes for single test mode, without DoseLab, and 80 minutes for AutoQA. (Table I). The times are averaged over the time taken by 4 different users. Auto QA allows the user to analyze more parameters than single-test mode, especially for kV and MV images (Figure1). Different profiles in s and energies are examined in minor time. The analysis of the MLC strip test allows to know exactly the number of the leaf that does not work correctly. In the Winston-Lutz test, the predicted accuracy of DoseLab is 1/3rd of a pixel, due to the centroid algorithm used. In addition, it is more quickly, complete and no user-dependent, because not manually measured. VMAT/DMLC tests images are checked automatically and in less time. CBCT QA test is less laborious and no user-dependent. Reproducibility of results is verified: the coefficient of variation over 5 consecutive repeated measurements is less than 5%. The software database makes it possible to monitor the trend of different parameters over time (Figure2). TABLE I. Comparison between single test mode and Auto QA, in term of time consuming. For AutoQA, the analysis time is given by the processing time from DoseLab software plus manual review of results. Procedure Machine Time Analysis Time Total Time Conventional Approach (Single test Mode) 80 min 115 min 195 min Auto QA 60 min 20 min 80 min

Figure 1. Number parameters measured for QA separated by procedure. * 2 s for each beam energy for Auto QA, 1 for each beam energy for Single Test Mode. ** tests for 3 beam energies for Auto QA, for 2 beam energies for Single Test Mode.