Diagnosis of early colorectal cancer invasion depth by quantitative evaluation of the basal indentation in CT colonography

Objective To investigate the feasibility of diagnosing the invasion depth of early colorectal cancer (CRC) by quantitatively evaluating the basal indentation (BI)—i.e., the intestinal lateral deformity—in CT colonography (CTC). Materials and methods 34 early CRCs (13 Tis CRCs and 21 T1 CRCs) in 32 patients who underwent a preoperative CTC were retrospectively examined. Two radiologists calculated the depth of the BI on a computed tomographic air-contrast enema (CT enema) image, the depth of the BI due to the geometric function (BI-G) on a cross-sectional multiplanar reconstruction (CS-MPR) image, and the ratio of the BI to the BI-G (i.e., the “BI ratio”) for each lesion. The BI ratios of the Tis and T1 CRCs were compared. Results The BI ratios were significantly higher in the T1 CRCs than in the Tis CRCs ( p