ESTRO 2024 - Abstract Book

S3324

Physics - Detectors, dose measurement and phantoms

ESTRO 2024

2295

Digital Poster

Experimental platform for the investigation of the FLASH effect with drosophila melanogaster

Riccardo Dal Bello 1 , Marvin Kreuzer 2 , Irene Vetrugno 2 , Jamie Little 3 , Rafael Kranzer 4 , Stefan Schischke 5 , Lily Bossin 6 , Eduardo Gardenali Yukihara 6 , Matthias Guckenberger 1 , Martin Pruschy 2 , Stephanie Tanadini-Lang 1 1 University Hospital Zurich and University of Zurich, Department of Radiation Oncology, Zurich, Switzerland. 2 University Hospital Zurich and University of Zurich, Laboratory for Applied Radiobiology, Department of Radiation Oncology, Zurich, Switzerland. 3 University of Zurich, Institute of Molecular Life Sciences, Zurich, Switzerland. 4 PTW Freiburg, -, Freiburg, Germany. 5 RadPro International GmbH, -, Wermelskirchen, Germany. 6 Paul Scherrer Institute, Department of Radiation Safety and Security, Villingen, Switzerland

Purpose/Objective:

The experimental investigation of ultra-high dose rate (UHDR) in radiotherapy is of growing interest due to the FLASH sparing effect, i.e. a biological effect with the potential of sparing normal tissue while being iso-effective in tumour control. The FLASH sparing effect has been demonstrated in several animal models for extremely hypofractionated treatments [1]. However, the scarce access to UHDR irradiation facilities and complex animal handling are limiting factors for a widespread investigation of the FLASH effect, which is required to provide solid radiobiological modelling towards clinical applicability. In this work we aim to tackle these two issues by presenting an experimental platform based on a commonly available electron linac [2] for irradiation of drosophila melanogaster [3], which compared to laboratory rodents requires less sophisticated equipment for maintenance and reproduction while also presenting uncomplicated ethical approval.

Material/Methods:

This study has been performed on a clinical TrueBeam linac (Varian, USA), which was decommissioned and upgraded to deliver electron beams of 16 MeV in UHDR mode. The study also included the delivery of 16 MeV UHDR onto the W-target in order to investigate the generation of photon UHDR radiation. Three different setups have been designed to deliver either conventional (CONV) or UHDR electron radiation to vials containing drosophila melanogaster at different source to surface distances (SSD): (A) irradiation at the linac isocenter (SSD ~ 100 cm), (B) at the faceplate (SSD ~ 60 cm) and (C) within the jaws (SSD ~ 40 or 20 cm) as shown in Figure 1. Each setup was based on a custom 3D printed phantom providing inserts for irradiation of one to ten vials simultaneously and a slot for positioning a prototype ultra-thin ion chamber (UTIC) [4] for dose monitoring and reporting. The commissioning of the phantoms has been performed with redundant dosimetry based on three independent methods, all proven to be dose rate independent, to measure dose at the location of the drosophila melanogaster: (i) Gafchromic EBT3 Films (Ashland, USA), (ii) Gafchromic HD-V2 Films (Ashland, USA) and (iii) OSL chips based on BeO read out with myOSLchip (RadPro, Germany). The dose measured by (i) - (iii) was then used to determine the calibration N [Gy/nC] for the UTIC in the specific setup for the 16 MeV electron irradiations.