ESTRO 2024 - Abstract Book

S3594

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

ESTRO 2024

Results:

Increasing the number of beams in the lung plans improved target coverage (V95%) from 91.6% (3-beam plan) to 95.8% (12-beam plan) and achieved a more homogeneous dose distribution (HI = 0.09) for the 12-beam plan (Figure 1). OARs showed reduced irradiation for the lung and oesophagus, while the heart and spinal cord experienced slightly elevated dose with higher beam numbers due to increased low dose splash, as seen in VMAT.

Energy comparison for lung and prostate plans showed consistently high target coverage across all energy levels, suggesting that coverage is relatively independent of energy. Mean doses to critical organs remained similar within acceptable limits, with the lung benefiting from lower energies (110-130 MeV) and the prostate taking advantage of the sharper penumbra seen at higher energies (180-200 MeV), all remaining within clinically acceptable limits. In the comparison between VHEE, photons and protons, all three achieved comparable target coverage (Figure 2). However, after anatomical changes were induced, the VHEE plan maintained both target coverage and a more uniform dose distribution, while photon plans saw much larger changes, on average, in dose to both the target and OARs, which rendered some plans unsuitable for clinical use. Protons exhibited the largest differences due to the inherent shift of the spread-out Bragg peak (SOBP).