ESTRO 2024 - Abstract Book

S3325

Physics - Detectors, dose measurement and phantoms

ESTRO 2024

Results:

The field size and beam divergence allow the simultaneous irradiation with electron beams of up to: (A) 10 vials for both CONV and UHDR, (B) 10 or 3 vials respectively for CONV or UHDR and (C) 1 vial in UHDR. These limits guarantee homogeneous dose within 5% (std/avg) to all vials included in the phantom. The different setups allow irradiating up to the following UHDR average dose rates when varying the SSD: 250 Gy/s (100 cm), 700 Gy/s (60 cm), 3000 Gy/s (40 cm) and 7000 Gy/s (20 cm). Figure 2 reports the calibration values for the UTIC obtained from the independent detectors (i) - (iii). The results show consistency between the investigated methods, which prompted the adoption of the calibration value N as the average of (i) - (iii). One unique value was chosen for (A) and (B) for both CONV and UHDR, exploiting the superior linearity of the UTIC over a wide dose rate range. SSD-specific calibration factors were adopted for (C) due to the off-centre location of the UTIC with respect to the vial, varying jaw positions and different secondary radiation scattering within the linac head. The presented setups allow dose reporting to the drosophila melanogaster within 5% accuracy, while the converted linac has been shown to provide precision better than 1% for CONV and 2.5% for UHDR irradiations. Finally, preliminary results for delivery of 16 MeV UHDR onto the W-target to generate photon UHDR radiation demonstrate that an average dose rate of 40 Gy/s (measured with (iii)) can be achieved with the setup (C) at SSD = 20 cm.