CT colonography data interpretation: effect of different section thicknesses--preliminary observations.
OBJECTIVE
To evaluate if differences exist in the interpretation of thin- and thick-section reconstructions at computed tomographic (CT) colonography.


METHODS
Twenty-five patients underwent multi-detector row CT colonography prior to colonoscopy. CT images were reconstructed with two methods: 1.25-mm sections reconstructed every 1 mm (thin) and 5-mm sections reconstructed every 2 mm (thick). Two independent readers interpreted thin sections, then waited a minimum of 15 days before interpreting thick sections. With colonoscopy as the reference standard, comparisons were made between interpretation of thin and thick sections, including sensitivity, specificity, and number of false-positive observations. Interpretation times were recorded, and comparisons were made by using repeated measures analysis of variance. For all tests, P <.05 indicated a statistically significant difference.


RESULTS
At colonoscopy, 10 patients had 12 polyps (< or =5 mm, n = 7; 6-9 mm, n = 2; > or =10 mm, n = 3). Sensitivity for polyp detection was statistically indistinguishable for thin and thick sections. Reader 1 had three false-positive findings with thin sections and six with thick sections. Reader 2 had six false-positive findings with thin sections and 11 with thick sections. For both readers, the number of false-positive findings was significantly lower for thin sections than for thick sections (P =.035). Specificity was 93.3% with thin sections and 80.0% with thick sections for reader 1 and 80.0% with thin sections and 73.3% with thick sections for reader 2. Mean interpretation time for reader 1 was significantly longer with thin sections (P <.001). Mean interpretation time for reader 2 was 13.0 minutes for both thin and thick sections.


CONCLUSIONS
Specificity improved for both readers with thin sections, with no difference in sensitivity.
Department of Radiology, Division of Abdominal Imaging, NYU Medical Center, 560 First Ave, Suite HW 207, New York, NY 10016, USA.
Yvonne W
YW
Lui
Michael
M
Macari
Gary
G
Israel
Edmund J
EJ
Bini
Hao
H
Wang
James
J
Babb
D000368:Aged; D000704:Analysis of Variance; D003111:Colonic Polyps / Q000175:diagnosis; D023881:Colonography, Computed Tomographic / Q000379:methods*; D003113:Colonoscopy; D005189:False Positive Reactions; D006801:Humans; D008297:Male; D008875:Middle Aged; D012680:Sensitivity and Specificity