Fig. 3.

(a) Distribution of measured mean CW displacements for all patients. A positive CW displacement denoted that the measured CW position was anterolateral of the planned position, while a negative value represented a posteromedial position. The red dotted lines represent the ±5 mm CTV-PTV margin thresholds. (b) An EPID frame for patient 04 with the CW position during treatment (light blue) well aligned to the planned position (red). (c) An EPID frame from another treatment arc for patient 04 in which the treatment and planned CW positions were misaligned. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)