ESTRO 2024 - Abstract Book

S3501

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

ESTRO 2024

distance is shortened to 80 cm and the electron beams with insufficient range to reach the target or impinging on the table before reaching the patient are also excluded. A DAO algorithm is applied to determine the most promising aperture, for all photon and electron candidates, based on the gradient of the objective function. This most promising aperture is used as a starting beam direction from which the path will “grow”, allowing further selection of beam directions with the same table angle. The selection of a beam direction with a different table angle (thus starting a new path with a different table angle) is only possible when the pre-defined m start is reached. The addition of beam directions stops when the user-defined total gantry angle range is reached. Subsequently, the determined paths are resampled to a finer resolution and a second DAO along the paths is performed, simultaneously modulating photon and electron beam intensities along the photon and electron arcs, both modulated using the photon MLC. A final dose calculation is performed and followed by weight re optimization, generating a colli-DYMBER plan. To test the method, we have created a colli-DYMBER plan for a clinically motivated case (post-operative pelvis case, 28 x 1.8 Gy). The input parameters are set to have a resolution of 10° along gantry and table axes, an m start of 4, a maximum of 7 arcs, and 720° total gantry angle range. The colli-DYMBER paths are resampled with 5° resolution along the gantry axis. The colli-DYMBER plan was compared to a coplanar VMAT plan with 720° total gantry angle range.