Hybrid trajectory and beam angle optimization for external beam radiation therapy

A method of determining treatment geometries for a radiotherapy treatment, the method comprising:

• providing a patient model including one or more regions of interest (ROIs) for the radiotherapy treatment;
• defining a delivery coordinate space (DCS) having a set of candidate vertices, each respective candidate vertex defining a respective beam's eye view (BEV) plane;
• for each respective BEV plane of a respective candidate vertex in the DCS:
• for each respective ROI of the one or more ROIs:
• evaluating a respective dose of the respective ROI from a respective beamlet incident from the respective candidate vertex and passing through a respective pixel of the respective BEV plane using transport solutions of the respective beamlet;
• evaluating a respective BEV score of the respective pixel using the doses of the one or more ROIs evaluated for the respective beamlet;
• and
• determining one or more BEV regions in the respective BEV plane based on the BEV scores of the pixels of the BEV planes corresponding to the set of candidate vertices in the DCS;
• determining a BEV region connectivity manifold based on the BEV regions of the BEV planes of the set of candidate vertices in the DCS, the BEV region connectivity manifold representing connections between contiguous BEV regions between adjacent vertices;
• determining a set of treatment trajectories based on the BEV region connectivity manifold, each treatment trajectory defining a respective path through a respective set of vertices in the DCS;
• and
• determining one or more intensity modulated radiotherapy (IMRT) fields, each respective IMRT field defines a respective direction of incidence corresponding to a respective vertex in the DCS.