ESTRO 2024 - Abstract Book

S4596

Physics - Optimisation, algorithms and applications for ion beam treatment planning

ESTR0 2024

2 opposing LR fields (90° and -90°) as dose boost fields for HypoxiaVOI. Furthermore, in order to investigate the effects of different ions, we choose 2 groups of heavy particles ( 12 C + 4 He, 16 O + 4 He) and designed 2 LEOPARD-MULTIION plans: 12 C in arc boost fields with 4 He in IMPT fields, and 16 O in arc boost fields with 4 He in IMPT fields, respectively. LET increases strongly with the weight of the ion, multiple ions therefore offer the chance to remove high LET from the tissue surrounding the tumor, while further increasing it in the HypoxiaVOI. Biological effective dose (D RBE ), and dose averaged linear energy transfer (LET d ) of plans were calculated and compared.

Results:

Carbon-only LEOPARD increased the mean LET d inside the HypoxiaVOI by 23.5% from 79.6 to 98.3 keV/µm. While the volume of very low doses outside the target was increased, all dose constraints were kept, and high LET was better concentrated inside the target, see Figure 1. Figure 2 shows the results for multi-ion LEOPARD, which eliminated high LET outside the target entirely and concentrated high LET to the HypoxiaVOI and its surrounding. Mean LET d in the HypoxiaVOI was 71.3 keV/µm and 104 keV/µm for 12 C and 16 O arcs, respectively.