The CAD system evaluated has a high level of performance in the detection of adenomatous polyps with CTC data from a polyp-enriched cohort different from that used to train the system.
Results with the QA software agreed with radiologists' assessment of colonic distention and residual fluid coverage but were a more objective assessment. Use of this QA software can help standardize two important factors, distention and residual fluid coverage, that affect the quality of CTC, reducing two known causes of poor CTC performance.
Purpose-To investigate the variability of CT colonography (CTC) scan quality obtained within and between institutions by using previously validated automated quality assessment (QA) software that assesses colonic distention and surface area obscured by residual fluid.Methods-The CTC scans of 120 patients were selected retrospectively, 30 from each of 4 institutions. The bowel preparation included oral contrast for fecal and fluid tagging. Patients at one institution (Institution 4) drank ½ the amount of oral contrast compared to the patients at the other 3 institutions. Fifteen of the CTC scans were from the beginning of the protocol studied at each institution and 15 scans were from the same protocol acquired approximately one year later in the study. We used previously validated QA software to automatically measure the mean distention and residual fluid of each of five colonic segments (ascending, transverse, descending, sigmoid, and rectum). Adequate distention was defined as a colonic diameter of at least 2 cm. Residual fluid was determined by the percentage of colonic surface area covered by fluid. We compared how the quality varied across multiple institutions and over time within the same institution.Results-No significant difference in the amount of colonic distention amongst the 4 institutions was found (p = 0.19). However, the distention in the prone position was significantly greater than the distention in the supine position (p < 0.001). Patients at Institution 4 had about ½ the amount of residual colonic fluid compared to patients at Institutions 1-3 (p < 0.01). The sigmoid and descending colons were the least distended segments, and the transverse and descending colon contained the most fluid on the prone and supine scans, respectively. More recently acquired studies had greater distention and less residual fluid but the differences were not statistically significant (p=0.30 and p=0.96, respectively).Conclusion-Across institutions, a significant difference can exist in bowel preparation quality for CTC. This study reaffirms the need for standardized bowel preparation and quality monitoring of CTC exams to reduce poor CTC performance.
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