Figure 6c: A 1.6-cm sessile adenoma in the transverse colon of a 52-year-old woman with a –0.5 grid line difference. (a) On supine CT scan, the polyp (thick arrow) is in the dependent location. (b) On prone CT scan, the polyp (thick arrow) has moved to the lateral location. In a and b, a small amount of dependent contrast material–enhanced residual fluid (thin arrows) is present. Corresponding (c) supine and (d) prone measurements on 3D endoluminal images obtained by using our circumferential localization method show polyp (arrow) positions at 8.6 and 8.1 grid lines, respectively.