ESTRO 2022 - Abstract Book

S243

Abstract book

ESTRO 2022

Figure 1: Optimized scanning patterns with initial (green) and final (red) positions, overlaid with the resulting PBS-DR distribution in a beam transverse plane through the PTV. Population median and quartiles of the PBS-DR-volume histograms are displayed in figure 2. Optimized patterns result in a significantly (p<0.01) larger FLASH coverage at 8 Gy, 40Gy/s, with a median increase of 198% (86cc) relative to the snake pattern.

Figure 2: Median, 1st and 3rd quartiles of PBS-DR volume histograms for the ipsilateral lung, including the 5mm PTV margin, irradiated to >8Gy with snake and optimized scanning patterns. Conclusion Significant improvements on the PBS-DR and, hence on the FLASH coverage and the potential healthy-tissue sparing are obtained by sequential scanning-pattern optimization. The patterns depend on the FLASH dose and DR thresholds and on the PBS-DR threshold. Therefore, it is critical to determine the dose and delivery time structure for which FLASH occurs.

OC-0283 Diamond detectors as a powerful real-time tool for commissioning UHDR electron beams in water

A. Gasparini 1,2 , G. Felici 3 , F. Galante 3 , F. Gomez 4 , R. Kranzer 5 , G. Mariani 3 , M. Marinelli 6 , M. Pacitti 7 , J. Paz-Martin 4 , V. Vanreusel 2,8 , G. Verona Rinati 6 , D. Verellen 1,2 1 Iridium Netwerk, Radiotherapy, Antwerp, Belgium; 2 University of Antwerp, Faculty of Medicine and Health Sciences, Antwerp, Belgium; 3 SIT, R&D, Aprilia, Italy; 4 University of Santiago de Compostela, MOLECULAR IMAGING AND MEDICAL PHYSICS, Santiago de Compostela, Spain; 5 PTW, R&D, Freiburg, Germany; 6 University of Rome Tor Vergata, Industrial Engineering, Rome, Italy; 7 SIT, R1D, Aprilia, Italy; 8 SCK CEN, Research in dosimetric applications, Mol, Belgium Purpose or Objective Ultra-high dose rate (UHDR) systems are currently extensively used for Flash RT in preclinical experiments. The commissioning of these systems is non-standard, yet of extreme importance for a correct comparison of preclinical results. Commercially available ion chambers (ICs) suffer from non-correctable saturation effects at UHDR (Di Martino, Front. Phys. 2020) and most commissioning procedures are based on passive dosimeters, such as Gafchromic films and alanine (Jaccard, Med. Phys. 2017, Montay-Gruel, Radiother. Oncol. 2017, Jorge, Radiother. Onc., 2019). Here we report the use of a novel diamond based Schottky diode detector (fDiamond) for real-time, in water tank commissioning of a dedicated preclinical UHDR system (ElectronFlash (SIT, Italy)).

Materials and Methods