ESTRO 2022 - Abstract Book

S1536

Abstract book

ESTRO 2022

Tomotherapy, and Accuray Precision TPS. Both linacs have 6 MV nominal energy. For organs at risk (OAR), in the treatment planned with Monaco, a single cost function named conformality was used to conform the dose, whereas in the treatment planned with tomotherapy, multiple auxiliary volumes were created and several cost functions were used for each one of them, which makes this planning more complex. The dose objective is that 100% of the PTV is covered by at least 95% of the prescribed dose. Conformality (CI) and homogeneity (HI) indices are compared between HT and VMAT, as well as doses to OAR. Results The PTV coverage requirement was met for both treatment planning systems (V100% ≥ 95%), being slightly higher for VMAT, 96.6% (VMAT) vs 95% (HT). The treatment planned in HT presents better CI (1.05 (HT) vs 1.34 (VMAT)) and the dose slightly more homogeneous (HI= 0.09 (TH) vs 0.14 (VMAT)). The doses to OARs, shown in the table (in cGy), were similar for both planning systems. Treatment time was significantly longer in HT, 20.2 min (TH) vs 13.7 min (VMAT).

Conclusion Planning with HT showed better dose distribution conformity and homogeneity compared to planning with VMAT. HT planning was superior in terms of reduction of mean and maximum doses in practically all the OAR. However, the differences between both are small, with the mean dose in some OARs slightly lower with VMAT, such as in the left kidney. Longer treatment time in HT could increase uncertainty due to intrafraction motion.

PO-1734 Automated treatment planning using dose mimicking for biologically guided dose prescription

A. Ureba 1,2 , J. Öden 3 , I. Toma-Dasu 1,4 , M. Lazzeroni 1,4

1 Stockholm University, Department of Physics, Stockholm, Sweden; 2 Karolinska Institute, Oncology and Pathology department, Solna, Sweden; 3 RaySearch Laboratories AB, Research department, Stockholm, Sweden; 4 Karolinska Institute, Oncology and Pathology Department, Solna, Sweden

Purpose or Objective