Fig. 1.

Left: Illustration of the different regions of interest investigated in this study: the four breast quadrants and the axilla. The nipple area was excluded from the analysis. Right: Figure indicating how shape changes were assessed from the extracted CT and CBCT contours. The distance between each contour element in the planning CT contour and the nearest neighbor contour element in the CBCT contour was calculated. A negative distance value indicates that the corresponding CBCT contour element lies closer to the ribs than the CT contour element and a positive distance value indicates that the CBCT contour element lies further away from the ribs than the CT contour element.