FIGURE 3.

Surface imaging (SI) residual error for no pod block mean (red dot) and standard deviation (red error bar) of vertical, longitudinal, lateral directions in mm, roll, pitch and rotation in degree is shown for couch angles 90°, 45°, 0°, 315°, 270°. Left pod block data are shown in green diamonds, and right pod block data are shown in blue squares. Longitudinal and lateral residual errors were analyzed from IDENTIFY logs and megavolt (MV) imaging data, whereas the other four degrees were from IDENTIFY logs and linac trajectory logs