Fig. 1

Treatment planning study. Schematics of the four treatment planning approaches. While the conventional, worst case, and SFUD approaches only perform one optimization on the planning CT (pCT), the adaptive approach facilitates a re-optimization on every fractional CT (f1,…). Consequently, we only have one set of pencil beam weights \(w_{j}^{pCT}\) for the conventional, worst case, and SFUD approach that are used to compute the fractionally delivered dose on every CT. For the adaptive approach, we have multiple sets of pencil beam weights \(\{w_{j}^{pCT},w_{j}^{f1},\dots \}\) - one for each CT