Figure 26. Misregistration artifact. FDG PET-CT was performed for staging in a patient with carcinoma of the left breast. Axial fused FDG PET-CT image shows a lymph node in the left axilla (straight arrow). Focal hypermetabolism in the node (curved arrow) appears lateral to its expected location in the axilla and overlies axillary fat instead of the node. Misregistration between the CT and PET images is due to patient motion between the CT and PET portions of the examination.