Fig. 1.
Schematic ten fraction illustration of PTV margin modelling to accommodate target rotational and intrafraction motion uncertainties. Due to these uncertainties, the fractional CTVs (CTVfx; orange ellipses) are misaligned relative to the planning CTV (CTVplan; green ellipse); nine fractions with small rotational errors and one exaggerated outlier fraction are illustrated. The PTV margin model uses these empirically derived CTVs to generate a parametric family of margins, two such margins are delineated in the dashed black ellipses. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)