ESTRO 2024 - Abstract Book

S3664

Physics - Dose prediction, optimisation and applications of photon and electron planning

ESTRO 2024

optimised have been then evaluated using the DVHs and the absorbed dose maps and the results have been compared against VMAT and PT approaches.

Results:

Particularly interesting cases for the study of VHEE treatments delivered in conventional and FLASH conditions are the pancreatic and lung cancers. In these cases the dose per fraction can be high (larger than 6 Gy) resulting in an enhanced FLASH effect and the OARs sparing plays a crucial role, as for example in the case of pancreatic cancer the effectiveness of the treatment is limited by the toxicity induced in duodenum, that can lead to its rupture and consequently to the death of the patient. In both cases, to quantify the FLASH-related decrease in radiation-induced toxicity in normal tissues we implemented the Flash Modifying Factor (FMF) dependence on the absorbed dose according to [4]. The obtained results demonstrate that it is possible, with the same number of fields used in RT, to optimise a treatment satisfying the PTV coverage constraints while achieving a satisfaing sparing of the OARs even in absence of FLASH effect, see table 1.

Table 1. Comparison between VMAT and IMRT VS VHEE treatment, for PZ2 (pancreatic tumor).

As electrons proved to be usable in conventional conditions, their delivery in FLASH conditions makes them valuable to exploit the FLASH gain to improve the treatment efficacy achieving a better PTV coverage or allowing a dose escalation not affecting the OARs, see figure 1.