Figure 2: PTV margins for real-time correction strategies for which 90% or 99% of patients receive a minimum dose greater than 95% or 99% of the prescription dose, respectively. Margins based on (c) prefraction, (d) prebeam correction (i) alone, or with further correction at thresholds of (ii) 5 mm and (iii) 3 mm are shown. Margins decrease with increased levels of corrective action.