Computed Tomographic Colonography: Assessment of Radiologist Performance With and Without Computer-Aided Detection

Department of Specialist Radiology, University College Hospital, London, England.
Gastroenterology (Impact Factor: 16.72). 01/2007; 131(6):1690-9. DOI: 10.1053/j.gastro.2006.09.051
Source: PubMed

ABSTRACT In isolation, computer-aided detection (CAD) for computed tomographic (CT) colonography is as effective as optical colonoscopy for detection of significant adenomas. However, the unavoidable interaction between CAD and the reader has not been addressed.
Ten readers trained in CT but without special expertise in colonography interpreted CT colonography images of 107 patients (60 with 142 polyps), first without CAD and then with CAD after temporal separation of 2 months. Per-patient and per-polyp detection were determined by comparing responses with known patient status.
With CAD, 41 (68%; 95% confidence interval [CI], 55%-80%) of the 60 patients with polyps were identified more frequently by readers. Per-patient sensitivity increased significantly in 70% of readers, while specificity dropped significantly in only one. Polyp detection increased significantly with CAD; on average, 12 more polyps were detected by each reader (9.1%, 95% CI, 5.2%-12.8%). Small- (< or =5 mm) and medium-sized (6-9 mm) polyps were significantly more likely to be detected when prompted correctly by CAD. However, overall performance was relatively poor; even with CAD, on average readers detected only 10 polyps (51.0%) > or =10 mm and 24 (38.2%) > or =6 mm. Interpretation time was shortened significantly with CAD: by 1.9 minutes (95% CI, 1.4-2.4 minutes) for patients with polyps and by 2.9 minutes (95% CI, 2.5-3.3 minutes) for patients without. Overall, 9 readers (90%) benefited significantly from CAD, either by increased sensitivity and/or by reduced interpretation time.
CAD for CT colonography significantly increases per-patient and per-polyp detection and significantly reduces interpretation times but cannot substitute for adequate training.

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    • "Computer aided diagnosis (CAD) tools are software applications designed for assisting the radiologist in the diagnosis of several conditions; for detection of lung nodules on chest X-ray or CT, breast nodules in screening mammography, and polyps in CT colonography.39–41 "
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    • "The Colon CAD software for CT Colonography may potentially improve readers’ detection performance and reduce variability among readers [11]. The CAD software can be used in a concurrent reading (CAD findings highlighted during the radiologist’s primary read) or a sequential/second reading paradigm (CAD findings highlighted only after the radiologist’s primary read is complete). "
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    ABSTRACT: 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. 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. Readers' manual measurements (diameters) and automatic measurements from CAD (diameters and volume) were compared to actual polyp sizes as measured by mechanical calipers. 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 readers' 3D measurements overestimated the size of polyps to variable extent. Both over- and underestimation of polyp sizes were observed in the readers' manual 2D measurements. Overall, Reader 1 (expert) had smaller mean error than Reader 2 (non-expert). CAD provided accurate size measurements for all polyps, and results were comparable to the two readers' manual measurements.
    Biomedical Imaging and Intervention Journal 07/2009; 5(3):e15. DOI:10.2349/biij.5.3.e15
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    • "CTC is safer than colonoscopy [17,18] while being more sensitive than barium enema, and appears to be more acceptable to patients than either of the other tests [8]. CTC may also be performed by technicians and in principle the data could be read by computer-assistance [19], accelerating diagnosis and throughput. "
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