Fig. 2.

A. Histograms of the applied online cone-beam CT corrections in the pre-SGRT group, in anterior-posterior (left), cranial-caudal (middle) and medio-lateral (right) directions. B. Online treatment monitor, showing the projection of the breast contour (green) and the lung contour ± 4 mm margin (red and green) from the DRRs on top of individual, real-time acquired portal imaging frames. In this case, image registration revealed a residual offset after online CBCT correction of −4 mm in cranial-caudal direction (V). c. Cumulative histogram of the residual 2D systematic setup error projected on the UV-plane of the medio-lateral beam: without correction protocol (black triangles), with online corrections (blue circles), with a no-action-level protocol (NAL N = 3, red stars), and with the extended NAL protocol (cyan line). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)