Fig. 3.

(a) PTV modeling of target rotational uncertainty. The results show the minimum PTV margin (PTV_min; x-axis) to cover ≥ CTV_min of the CTV_fx volume (individual colored lines) in ≥ Fx_min of fractions (individual plots) in ≥ Pt_min of patients (y-axis). For example, point A depicts that a 3.0 mm PTV margin is required to cover 98 % of the CTV_fx volume in 95 % of fractions in 95 % of patients. Similarly, point B illustrates that a 1.5 mm margin is required to cover 95 % of the CTV_fx volume in 90 % of fractions in 90 % of patients. (b) PTV modeling of intrafraction motion. The solid lines denote PTV modeling of residual setup uncertainty for the 60 patient/412 fraction subset with end of fraction repeat T1 imaging. The dashed lines repeat this modeling after the inclusion of intrafraction motion. An additional PTV margin of 0.5 and 0.2 mm (horizontal distance between the solid and dashed lines) is needed to accommodate intrafraction motion for scenarios A and B, respectively.