ESTRO 2025 - Abstract Book

S3687

Physics - Quality assurance and auditing

ESTRO 2025

3866

Digital Poster Initial results of a dosimetry audit campaign in Italy

Christian Fiandra 1 , Serenella Russo 2 , Carlo Cavedon 3 , Benjamin Kellogg 4 , Liset De La Fuente 4 , Michele Stasi 5 1 Department of Oncology, University of Turin, AOU Città della Salute e della Scienza, Turin, Italy. 2 AUSL Toscana Centro, Health Physics, Florence, Italy. 3 Department of Pathology and Diagnostics, Azienda Ospedaliera Universitaria Integrata, Verona, Italy. 4 Department of Human Health, International Atomic Energy Agency, Vienna, Austria. 5 Medical Physics Department, Ordine Mauriziano Hospital, Turin, Italy Purpose/Objective: To assess the accuracy of reference dosimetry in photon and electron beams of Italian radiotherapy centers during the period of National Recovery and Resilience Plan (PNRR) from the end of 2023 to 2026. Material/Methods: The PNNR in Italy allocated funding for 65 C-arms linacs across the country. The call for tenders required each machine to be checked at five different beam energies. Unfortunately, ENEA-INMRI, a long-standing source of support for AIFM, has temporarily suspended the national audit service. The IAEA exceptionally agreed with AIFM to provisionally support the Italian radiotherapy centers (RT) within the framework of IAEA/WHO postal dosimetry audit program. Audits were provided for photon (energy range 6-18 MV) and electron (energy range 6-12 MeV) beams including flattening filter free C-arm Linac and Tomotherapy beams. For each beam audited, irradiation of two Radiophotoluminescent Dosimeters (RPLDs) with 2 Gy was required in reference conditions, according to the international dosimetry protocols such as TRS 398. Audit results were reported in terms of the Dratio (IAEA mean dose/User stated dose); a result within 5% deviation was considered acceptable with no further action required from the user. The uncertainty in the RPLD dose measurement was 1.5% (1 standard deviation). Results: Audit was successfully performed for 116 photon and electron beams in 28 newly installed linacs in 28 Italian RT centers. The beam qualities analyzed were 6MV WFF (27%), 6MV FFF (25%), 10MV WFF (17%), 10MV FFF (13%), 15MV WFF (6%) and 18MV WFF (3%) for photons; 6MeV (4%), 8MeV (1.0%), 9MeV (4%) and 12MeV (2%) for electrons. The Dratio were normally distributed with 95% of data between 0.971 and 1.028; 94% of values were in the range [0.95,1.05] while 88.7% were in the range [0.98,1.02]. Seven results were identified as unsatisfactory (outside the range 0.95-1.05) due to a potential setup or irradiation error. These high discrepancies were solved (one is pending) with follow-up measurements performed with a second batch of dosimeters. Analysis of variance (ANOVA) showed no significant differences of Dratio between energies.