Figure 3.

Mean absolute centroid LE in the LR, AP, and SI directions and in three-dimensional (3D) magnitude after individual registration of (a) the primary tumor and (b) involved lymph nodes. Standard normalized mutual information (NMI) and transitive-based registrations were fully automatic, whereas seeded NMI and rereferenced registrations required varying degrees of manual interaction and were considered semi-automatic. Single asterisks denote significantly improved target localization relative to the initial bony-anatomy alignment, and double asterisks show additional significant improvement relative to other automatic registration techniques. Nominal centroid alignment of individual target volumes (GTV_P or GTV_LN) resulted in perfect centroid overlap, corresponding to zero centroid LE.