ESTRO 2024 - Abstract Book

S4684

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

ESTR0 2024

Ten high-risk prostate cancer patients were included in the study. For each patient, two treatment plans were made in RayStation 12A (RaySearch Laboratories AB, Sweden) based on the conventional planning CT (pCT): a volumetric modulated arc therapy (VMAT) photon plan, and an intensity-modulated proton therapy (IMPT) proton plan using two parallel opposed lateral fields. The plans were prescribed to 60 Gy (20 fractions of 3 Gy) to the clinical target volume (CTV), which consisted of prostate and seminal vesicles. An example of field setups and dose distributions of VMAT and IMPT plans is presented in Figure 1. sCTs were generated from T2-weighted MRI images using MRI planner software (Spectronics, Sweden) and registered to the pCT based on bony anatomy. Delineated structures were copied from the pCT to the sCT, and each RT plan was recalculated on the sCT. Doses were exported in DICOM format and analyzed using Python. Dosimetric evaluation and comparison were performed by dose volume histogram (DVH) analysis and gamma index analysis. Visual assessments of line doses for single and combined proton fields were also done.

Figure 1: Example of proton IMPT plan (top) and photon VMAT plan (bottom) for one patient. Field setup for VMAT plan is one full arc, and for IMPT plan two parallel opposed lateral fields.

Results: