Feasibility of computer-aided detection for low-dose CT colonography

Objective To assess the capability of the colon computer-aided-detection(CAD) for the detection of colonic neoplasm on low-dose CT colonography with changing sphericity filter values. Methods Low dose (50 mA) CT colonography data from 56 patients with 159 colonic neoplasms confirmed by conventional colonoscopy and surgery were divided into four groups: colorectal cancer, ≥ 10 mm polyps,5. 1 to 9. 9 mm polyps and ≤ 5.0 mm polyps. The golden standard was established by matching the neoplasms on CT colonography images. The datasets analyzed subsequently by the Colon CAD system at four discrete sphericity filter settings (SFV): 0. 25, 0. 50, 0. 75 and 1.00. The location and size of highlight lesions by the colon CAD were recorded. Comparison was made with the known golden standard in order to determine the detective rate of colonic neoplasms. Chi-square tests were used to compare the detection rates of four groups by CAD SFV at four settings. Results Fifty six patients had 159 colonic neoplasms including 44 colonic cancers, 45 large polyps (max diameter≥ 10. 0 mm), 32 median polyps (max diameter 5. 1 to 9. 9 mm) and 38 small polyps ( max diameter ≤5.0 mm). The colon CAD had the detective rate of 85.5%( 136/159), 85.5% ( 136/159 ), 79. 2% ( 126/159 ) and 56. 0% (89/159) for all colonic neoplasms at four sphericity filter settings 0. 25, 0. 50, 0. 75 and 1.00 respectively. There was statistically significant difference between the sphericity filter settings at 0. 25 and 1.00 ( P ＜ 0. 05). Detective rate was highest at lower sphericity, false-positive rate increased at same time, however, 91.4% ( 138/151 )to 93.9% (31/33 )of false-positives were rapidly dismissible with 2D axial images, only 6. 1% (2/33)to 8.6% (13/151)of false-positives needed to discriminate with multiplanar reconstruction or 3D virtual colonoscopy. Conclusion The Colon CAD system can detect colonic neoplasms satisfactorily in low dose CT colonography and may satisfy the needs of radiologists with different experience by changing sphericity filter settings. Key words: Colonic neoplasms;  Diagnosis,computer-assisted;  Tomography,X-ray computed