چكيده لاتين :
Purpose: The purpose of this study is to assess the performance of computer-aided detection (CAD) software in
detecting and measuring polyps for CT Colonography, based on an in vitro phantom study.
Material and methods: A colon phantom was constructed with a PVC pipe of 3.8 cm diameter. Nine simulated
polyps of various sizes (3.2mm-25.4mm) were affixed inside the phantom that was placed in a water bath. The phantom
was scanned on a 64-slice CT scanner with tube voltage of 120 kV and current of 205 mAs. Two separate scans were
performed, with different slice thickness and reconstruction interval. The first scan (thin) had a slice thickness of 1mm
and reconstruction interval 0.5mm. The second scan (thick) had a slice thickness of 2mm and reconstruction interval of
1mm. Images from both scans were processed using CT Colonography software that automatically segments the colon
phantom and applies CAD that automatically highlights and provides the size (maximum and minimum diameters,
volume) of each polyp. Two readers independently measured each polyp (two orthogonal diameters) using both 2D and
3D views. Readersי manual measurements (diameters) and automatic measurements from CAD (diameters and volume)
were compared to actual polyp sizes as measured by mechanical calipers.
Results: All polyps except the smallest (3.2mm) were detected by CAD. CAD achieved 100% sensitivity in
detecting polyps .6mm. Mean errors in CAD automated volume measurements for thin and thick slice scans were 8.7%
and 6.8%, respectively. Almost all CAD and manual readersי 3D measurements overestimated the size of polyps to
variable extent. Both over- and underestimation of polyp sizes were observed in the readersי manual 2D measurements.
Overall, Reader 1 (expert) had smaller mean error than Reader 2 (non-expert).
Conclusion: CAD provided accurate size measurements for all polyps, and results were comparable to the two
readersי manual measurements.
