Figure 1c:

Example of ablative margin measurement in a 74-year-old man with a 2.7-cm tumor. (a) Axial portal venous phase CT image shows the tumor before RFA; distances 1, 2, and 3 were measured from the edges of the tumor to the chosen landmarks. (b) Axial portal venous phase CT image obtained 5 weeks after RFA shows the ablation defect; the same distances 1, 2, and 3 were measured from the edge of the ablation defect to the same landmarks. The corresponding distances were subtracted, and the smallest value was chosen as the minimal margin—that is, distance 1 (16.3 mm – 12.5 mm = 3.8 mm). (c) Axial portal venous phase CT image obtained 4.5 months after RFA shows LTP (arrow) at the same site of the insufficient margin (distance 1).