Experienced radiologists speed-read virtual colonoscopy exams

June 1, 2005

Radiologists may face a dramatic increase in workload if they get what they want and virtual colonoscopy becomes the modality of choice for colon cancer screening. Reading exams in less than five minutes with only a minor drop in sensitivity is feasible, however, according to a study presented at the American Roentgen Ray Society meeting.

Radiologists may face a dramatic increase in workload if they get what they want and virtual colonoscopy becomes the modality of choice for colon cancer screening. Reading exams in less than five minutes with only a minor drop in sensitivity is feasible, however, according to a study presented at the American Roentgen Ray Society meeting.

Researchers led by Dr. Philippe Lefere of the radiology department at the Stedelijk Ziekenhuis in Belgium studied the accuracy of two readers examining virtual colonoscopies from 180 patients.

Patients prepared for virtual colonoscopy with low-fiber diets and a reduced cathartic cleansing with magnesium citrate and bisacodyl as well as stool tagging with barium. Researchers obtained CT studies in both the prone and supine positions.

Two readers interpreted studies on CT colonography workstations equipped to handle primary 2D reads with fast 3D correlation. The first reader worked under a five-minute limit for interpreting exams. The second reader took as much time as needed to complete an interpretation.

The readers detected a total of 42 lesions 6 to 9 mm in size and 30 that were larger than 1 cm. The first reader took an average of four minutes and 32 seconds to complete exam interpretations, compared with nine minutes and 15 seconds for the second reader.

Sensitivity for the first reader was 76.2% for lesions greater than or equal to 6 mm and 100% for lesions 1 cm or larger, resulting in an 86.1% overall sensitivity, according to Lefere. The second reader exhibited an 85.7% sensitivity for 6-mm or larger lesions and 100% sensitivity for lesions larger than 1 cm, for an overall sensitivity of 91.6%.

Of course, even if a radiologist could routinely and accurately read virtual colonoscopy exams in less than five minutes, the study did not examine the affects of reader fatigue, Lefere said. Reading exams at the end of a long day may yield different results than interpreting exams first thing in the morning.

To perform a good exam regardless of speed, radiologists need intensive training and a quiet and comfortable reading environment, he said. In the future, computer-aided detection may help reduce perceptual errors.

For more information from the online Diagnostic Imaging archives:

Large CT colonography trial opens with mixed reactions

CT colonography dose varies little over years

CT colonography standards foster exam's legitimacy

Electronic subtraction fools CAD, leads to false positives

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