CT colonography may improve colorectal cancer screening compliance.

OBJECTIVE: While colonoscopy is currently the preferred test for colorectal cancer (CRC) screening, the invasive and time-consuming characteristics of the test are often cited as reasons for noncompliance with screening. CT colonography (CTC) is a less invasive screening method that is comparable to colonoscopy for the detection of advanced neoplasia. The aim of this project was to assess patient preferences between colonoscopy and CTC in an open access system. MATERIALS AND METHODS: Two hundred fifty consecutive average-risk patients undergoing CRC screening completed a survey that assessed reasons for choosing CTC in lieu of colonoscopy, compliance with CRC screening if CTC was not offered, and which of the two tests they preferred. RESULTS: The most common reasons for undergoing CTC included convenience (33.6%), recommendation by referring provider (13.2%), and perceived safety (10.8%). Had CTC not been an available option, 91 of the 250 patients (36%) would have foregone CRC screening. Among the 57 patients who had experienced both procedures, 95% (n = 54) preferred CTC. CONCLUSION: These findings show the importance of providing CTC as an alternative screening option for CRC at our institution, which may increase CRC adherence screening rates.

CT colonography computer-aided polyp detection: Effect on radiologist observers of polyp identification by CAD on both the supine and prone scans.

RATIONALE AND OBJECTIVES: To determine whether the display of computer-aided detection (CAD) marks on individual polyps on both the supine and prone scans leads to improved polyp detection by radiologists compared to the display of CAD marks on individual polyps on either the supine or the prone scan, but not both. MATERIALS AND METHODS: The acquisition of patient data for this study was approved by the Institutional Review Board and was Health Insurance Portability and Accountability Act-compliant. Subsequently, the use of the data was declared exempt from further institutional review board review. Four radiologists interpreted 33 computed tomography colonography cases, 21 of which had one adenoma 6-9 mm in size, with the assistance of a CAD system in the first reader mode (ie, the radiologists reviewed only the CAD marks). The radiologists were shown each case twice, with different sets of CAD marks for each of the two readings. In one reading, a true-positive CAD mark for the same polyp was displayed on both the supine and prone scans (a double-mark reading). In the other reading, a true-positive CAD mark was displayed either on the supine or prone scan, but not both (a single-mark reading). True-positive marks were randomized between readings and there was at least a 1-month delay between readings to minimize recall bias. Sensitivity and specificity were determined and receiver operating characteristic (ROC) and multiple-reader multiple-case analyses were performed. RESULTS: The average per polyp sensitivities were 60% (38%-81%) versus 71% (52%-91%) (P = .03) for single-mark and double-mark readings, respectively. The areas (95% confidence intervals) under the ROC curves were 0.76 (0.62-0.88) and 0.79 (0.58-0.96), respectively (P = NS). Specificities were similar for the single-mark compared with the double-mark readings. CONCLUSION: The display of CAD marks on a polyp on both the supine and prone scans led to more frequent detection of polyps by radiologists without adversely affecting specificity for detecting 6-9 mm adenomas.

Colorectal and extracolonic cancers detected at screening CT colonography in 10,286 asymptomatic adults.

PURPOSE: To retrospectively determine the detection rates, clinical stages, and short-term patient survival for all unsuspected cancers identified at screening computed tomographic (CT) colonography, including both colorectal carcinoma (CRC) and extracolonic malignancies. MATERIALS AND METHODS: From April 2004 through March 2008, prospective colorectal and extracolonic interpretation was performed in 10,286 outpatient adults (5388 men, 4898 women; mean age, 59.8 years) undergoing screening CT colonography at two centers in this institutional review board-approved, HIPAA-compliant study. For all histologically proved, clinically unsuspected cancers detected at CT colonography that were identified at retrospective review of the medical records, the stage of disease, treatment, and clinical outcome were analyzed. Benign neoplasms (including advanced colorectal adenomas), symptomatic lesions, and tumors without pathologic proof were excluded. Statistical analysis was performed with Fisher exact test and two-sample z test. RESULTS: Unsuspected cancer was confirmed in 58 (0.56%) patients (33 women, 25 men; mean age, 60.8 years), which included invasive CRC in 22 patients (0.21%) and extracolonic cancer in 36 patients (0.35%). Extracolonic malignancies included renal cell carcinoma (n = 11), lung cancer (n = 8), non-Hodgkin lymphoma (n = 6), and a variety of other tumors (n = 11). Cancers in 31 patients (53.4%) were stage I or localized. At the most recent clinical follow-up (mean, 30.0 months +/- 11.8 [standard deviation]; range, 12-56 months), three patients (5.2%) had died of their cancer. CONCLUSION: The overall detection rate of unsuspected cancer is approximately one per 200 asymptomatic adults undergoing routine screening CT colonography, including about one invasive CRC per 500 cases and one extracolonic cancer per 300 cases. Detection and treatment at an early presymptomatic stage may have contributed to the favorable outcome.

CT colonography predictably overestimates colonic length and distance to polyps compared with optical colonoscopy.

OBJECTIVE: The purpose of this study was to determine the discrepancy between CT colonography (CTC) and optical colonoscopy (OC) measurements for both anus-to-cecum length and anus-to-polyps distance and then determine whether a conversion factor could be generated to equate these CTC and OC distances. MATERIALS AND METHODS: We retrospectively reviewed CTC and OC reports from patients who had undergone both procedures as part of an established protocol. The anus-to-cecum measurement recorded on a single proprietary CTC workstation was compared with the OC cecal length for each patient. Likewise, anus-to-polyp distances were compared as measured by the radiologist and endoscopist. RESULTS: Three hundred thirty-eight patients and 437 polyps were identified with complete data from both CTC and same-day OC. The average anus-to-cecum distance measured at CTC was 189 cm (range, 75-257 cm) and at OC, 108 cm (range, 65-150 cm). For polyps proximal to the splenic flexure (n = 145), the CTC anus-to-polyp measurement was on average 1.7 times that measured at OC. For left-sided polyps (n = 292), the CTC measurement was, on average, within 12 cm or 1.3 times that of the OC anus-to-polyp measurement. All the differences between CTC and OC measurements of cecal length and polyp distances were found to be statistically significant using a paired Student's t test of means (p < 0.001). CONCLUSION: Anus-to-cecum and anus-to-polyp distances are disparate but comparable using a conversion factor of 0.57 for the CTC anus-to-cecum measurement and 0.59 for right-sided CTC anus-to-polyp or 0.78 for left-sided CTC anus-to-polyp measurements. These anus-to-polyp conversion factors could potentially augment current CTC guidelines for accurate and precise polyp localization and removal at endoscopy.

Conspicuity of colorectal polyps at CT colonography: visual assessment, CAD performance, and the important role of polyp height.

RATIONALE AND OBJECTIVES: The factors that influence the conspicuity of polyps on computed tomographic (CT) colonography (CTC) are poorly understood. The aim of this study is to compare radiologists' visual assessment of polyp conspicuity to quantitative image features and show the relationship between visual conspicuity and the detection of colonic polyps by computer-aided detection (CAD) on CTC. METHODS: One polyp (size range 6-10 mm) was selected from the CTC examination of each of 29 patients from a larger cohort. All patients underwent oral contrast-enhanced CTC with same-day optical colonoscopy with segmental unblinding. The polyps were analyzed by a previously validated CAD system and placed into one of two groups (detected [n = 12] or not detected [n = 17] by CAD). The study population was intentionally enriched with polyps that were not detected by the CAD system. Four board-certified radiologists, blinded to the CAD results, reviewed two- and three-dimensional CTC images of the polyps and scored the conspicuity of the polyps using a 4-point scale (0 = least conspicuous, 3 = most conspicuous). Polyp height and width were measured by a trained observer. A t-test (two-tailed, unpaired equal variance) was done to determine statistical significance. Intra- and interobserver variabilities of the conspicuity scores were assessed using the weighted kappa test. Regression analysis was used to investigate the relationship of conspicuity to polyp height and width. RESULTS: A statistically significant difference was found between the average conspicuity scores for polyps that were detected by CAD compared to those that were not (2.3 +/- 0.6 vs. 1.4 +/- 0.8) (P = .004). There was moderate intraobserver agreement of the conspicuity scores (weighted kappa 0.57 +/- 0.09). Interobserver agreement was fair (average weighted kappa for six pair-wise comparisons, 0.38 +/- 0.15). Conspicuity was correlated with manual measurement of polyp height (r(2) = 0.38-0.56, P < .001). CONCLUSIONS: This CAD system tends to detect 6-10 mm polyps that are more visually conspicuous. Polyp height is a major determinant of visual conspicuity. The generalizability of these findings to other CAD systems is currently unknown. Nevertheless, CAD developers may need to specifically target flatter and less conspicuous polyps for CAD to better assist the radiologist to find polyps in this clinically important size category.