Computed Tomographic Colonography: Assessment of Radiologist Performance With and Without Computer-Aided Detection
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.
- SourceAvailable from: Alain Nchimi
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ABSTRACT: MDCT has a leading role in the diagnostic process of colorectal cancer (CRC), including early diagnosis (i.e., screening), staging, follow-up, and assessment of therapy response. Imaging protocols need to be tailored according to clinical requirements. Thus, CT colonography (CTC) is necessary for early diagnosis of CRC and polyps. Technical protocol needs preliminary bowel cleansing and air distension, although new developments include prepless approaches, without the use of laxative agents, and CO2 automatic insufflation. Low-dose scanning protocols are routinely implemented for screening subjects, and image-reviewing software now offers new visualization tools that help decrease perceptual errors. CTC has a definite role in screening, being one of the official screening options suggested by major international societies. Contrast-enhanced MDCT, performed according to standard scanning protocols, is still the imaging modality of choice for staging and follow-up of CRC, although there is an emerging role of the hybrid PET–CT scanner, particularly in the follow-up. In addition, new information may arise from new PET–CT colonography examinations, whose role is still to be defined. Finally, in the assessment of therapy response, CT perfusion is required. CT perfusion offers functional information (blood flow, blood volume, mean transit time, and permeability surface), which correlate with tumor neoangiogenesis. Very preliminary results of few clinical studies using perfusion CT before and after radiochemotherapy treatment show a potential important clinical application in rectal cancer management. Monitoring the response to therapy may lead clinicians to customize treatment to the response of the individual patient, and reliable prediction of the response may improve patient selection and avoid nonproductive, costly treatments.