ESTRO 2023 - Abstract Book

S1482

Digital Posters

ESTRO 2023

1 University of Florence, Dept. of Experimental and Clinical Biomedical Sciences "Mario Serio", Florence, Italy; 2 Azienda Ospedaliero Universitaria Careggi, Medical Physics Unit, Florence, Italy; 3 Azienda Ospedaliero Universitaria Città della Salute e della Scienza, Medical Physics Unit, Torino, Italy; 4 Azienda USL Toscana Centro, S.C. Fisica Sanitaria, Florence, Italy; 5 Azienda Ospedaliero Universitaria Città della Salute e della Scienza, Medical Physics Unit , Florence, Italy Purpose or Objective The focus of this study was a definition of a consistent dataset for small fields dosimetry in tomotherapy in order to harmonize the expertise of different Italian radiotherapy centers and encouraging data standardization. The preliminary data of the reference department (Florence Hospital) and of the pilot center (Torino Hospital) were here presented. Materials and Methods A specific set of 12 small fields was defined by the MLC (1.25, 2.5, 3.75, 5 cm) and by the jaws (1, 2.5, 5 cm). For all fields, output factors (OFs) in a 3D water phantom (Blue Phantom Helix) were measured at the reference department for an Hi Art tomotherapy equipment by using two detectors: Razor Chamber (RC) and Razor Diode (RD). A protocol with the instructions was prepared by the reference site together with the sinograms of the open fields. Measurements in a solid water phantom were performed at the pilot center for a Radixact tomotherapy equipment by using the same RC and RD detectors. OFs were assessed at a reference 10x5 cm2 field at 85 cm SSD and 10 cm of depth. Measurements with EBT3 film (GAF) were also acquired in a solid water phantom by both departments to establish a preliminary reference dataset. Moreover an evaluation of effective equivalent fields s was done. The pilot center reviewed the final procedure. Results In the figure 1, OFs of both departments were plotted vs measured equivalent fields s. RC and RD showed a good inter department agreement with deviations less than 1% for 5 cm and 2.5 cm jaws positions. For 1 cm jaw’s , deviations within 5% were observed.