Figure 7.

Using bony anatomy as registration landmark. The original two CT images (A, C) are $15.0\pm 0.1\text{mm}$ apart laterally and the registered images (B, D) are obtained with a lateral shift of 15.00 mm. A minor superior‐inferior shift of 0.3 voxel (0.23 mm) is made to compensate the couch positioning error. Note: the local color inhomogeneity (contour pattern) shown in (B, D) is caused by limited imaging resolution and visualization with slightly different R/G‐LUT settings, rather than global image misalignment.