ESTRO 2024 - Abstract Book

S3703

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

ESTRO 2024

Using the proposed approach, we created step-and-shoot non-coplanar IMRT plans for three patients with multiple BMs (patient 1: 29 metastases/14.7 cc; patient 2: 27 metastases/22.6 cc; patient 3: 30 metastases/20.3 cc). These plans (hereafter referred to as IMRT opt ) were then benchmarked against corresponding IMRT plans obtained by utilizing a fixed collimator angle at 0° for all apertures (hereafter referred to as IMRT 0 ). The number of apertures was set to 100 for all plans, which were delivered from 46 non-coplanar beam orientations. The allowed collimator angles for the IMRT opt plans ranged from 0° to 175° in 5° steps. A dose of 30 Gy in 6 fractions was prescribed to the 80% isodose line of the PTV, and both the brain volume V 26Gy receiving a dose larger than 26 Gy and the mean brain dose were minimized.

Results:

The dose distributions for the IMRT opt and IMRT 0 plans for patient 1 are shown in Figure 2, together with a comparison of the dose-volume histograms (DVH) evaluated for the PTV and the healthy brain (defined as brain without PTV), respectively. By optimizing the collimator angle for each individual aperture, both dose conformity and sparing of the healthy brain could be improved. For patient 1, brain V 26Gy was reduced from 19.5 cc to 18.7 cc (-4.1%), the mean brain dose was reduced from 5.83 Gy to 5.72 Gy (-1.9%) and the conformity index (CI RTOG )