Modulation indices
REGRESSION
We developed several Python scripts to compute complexity metrics consisting of the following components for each segment: The aperture area was calculated as the total area of all MLC openings; the aperture perimeter (AP) is the length of the boundary of the total area of all MLC openings; and the aperture irregularity (AI) represents the deviation of aperture shape from the circle, and it equals one if the aperture is a perfect circle. For each beam, the beam area (BA) is the total area of all MLC openings of the beam, and the beam irregularity (BI) is computed using AI. For each plan, the plan‐averaged beam area (PA) and the plan‐averaged beam irregularity (PI) are calculated by averaging the BA and BI values using the beam MUs as weighting factors.Moreover, LT/arc length (AL) was calculated due to LT being originally formulated for the VMAT plan with one single arc.The extracted features used in the random forest regression modelAbbreviations: MLC, multileaf collimator; MU, monitor unit.