ESTRO 2025 - Abstract Book

S2667

Physics - Detectors, dose measurement and phantoms

ESTRO 2025

Conclusion: The optimized dosimeter enables precise low-dose dosimetry applications requiring high sensitivity, as well as an extended measurement range up to 30 Gy, which could be useful for irradiation with high doses as in FLASH radiotherapy.

Keywords: Chemical Dosimetry, Low-Dose, Fricke Dosimeter

4009

Digital Poster Film dosimetry for surface irradiation without physical bolus, calculated in RayStation for Radixact x9 Edwin Rozo 1 , Ronald F Velasco 2 1 Radiotherapy, Fundación Santa Fe de Bogotá, Bogota, Colombia. 2 Physics, Universidad Nacional de Colombia, Bogotá, Colombia Purpose/Objective: The objective of this work is to verify the dose of a surface irradiation treatment with photons, calculated in RayStation without the usage of physical bolus, using the Cheese Phantom and irradiated with Radixact X9. Material/Methods: The Cheese Phantom was used for a helical treatment in the Radixact X9, verifying the dose with previously calibrated GafChromic EBT3 radiochromic film [1,2]. These were placed in three positions (anterior, left, and right) corresponding to the center of the phantom (see Figure 1a). Images were acquired with ClearRT and planned in RayStation, using a pitch of 0.23, fixed jaws, a field size of 5.04 cm, a gantry period of 29.2 s, and a total treatment time of 357 s. The PTV surrounded the phantom surface with a thickness of 0.5 cm, and a virtual 1cm bolus [3] was included, along with three auxiliary contours at the plate positions to average the calculated doses (see Figure 1b). The dose per session was 200 cGy over 12 sessions. The plates were scanned with an EPSON Expression 12000XL and analyzed using the software RIT v6.11.

Figure 1: a) Corresponds to the Cheese Phantom with radiochromic films in the anterior, left and right positions. b) Contours made in RayStation, orange color corresponds to PTV and green color to virtual bolus