ESTRO 2025 - Abstract Book

S2574

Physics - Detectors, dose measurement and phantoms

ESTRO 2025

828

Digital Poster Comparison of dose response and energy dependent of the new LD-V1 with XR-QA2 GafChromicTM film models Nada Tomic 1,2,3 , Slobodan Devic 1,2,3 1 Radiation Oncology, Jewish General Hospital, Montreal, Canada. 2 Medical Physics Unit, McGill University, Montreal, Canada. 3 Segal Cancer Center, Jewish General Hospital, Montreal, Canada Purpose/Objective: An XR-Q2 film model, designed a decade ago, in combinations with inexpensive document scanners have been used as convenient and precise 2D reference dosimeters for dosimetry applications at low photon energies used in diagnostic radiology and for imaging procedures in radiation therapy[1,2]. Dose response and energy dependence of the latest LD-V1 GafChromic TM film model was compared to its predecessor XR-QA2 model in a dose rage up to 15 cGy for two beam qualities: 80 kVp (3.18 mm Al) and 140 kVp (5.37 mm Al) photon beams. The latest LD-V1 GafChromic TM film model was designed by manufacturer to extend measuring dose range to be from 0.2 to 20 cGy. Material/Methods: Radiation source used was an imaging x-ray tube on Varian TrueBeam linear accelerator. Reference dosimeter (RaySafeX2, Sweden) and pieces of two film models with 2”x3” in size were placed at the surface of Styrofoam phantom (irradiation in air) at a distance 65 cm from the kV X-ray source. Collimator jaws of kV X-ray source were set at 13 cm x 13 cm at the surface of the phantom and we used large focal spot. Based on the measured air Kerma in air (K air air ) by our reference dosimeter, pieces of film were irradiated to different values of K air air in range from 0.2 to 15 cGy. Film pieces were scanned 24 hours after irradiation with Epson Expression 11000 document scanner and saved as 48 bit RGB tiff images . Film response was calculated as reflectance change: DR(K air air ) = (1/2 16 )(PV_unexposed PV_exposed(K air air )). Results: Figure 1 a) and b) indicate that sensitivity of the latest LD-V1 film model is lower than its predecessor XR-QA2 model. On the other hand, figure 1 c) and d) show that energy dependent response of the LD-V1 is less pronounced than in the case of XR-QA2 film model.