Protocol optimization of multidetector computed tomography colonography using pig colonic phantoms.
OBJECTIVE
The introduction of multidetector computed tomography (CT) increases the possibility of enhanced polyp detection using CT colonography. The effects of collimation and tube currents on polyp detection were investigated in pig colonic phantoms to determine the optimal scanning parameters.


METHODS
Twenty pig colons were prepared, and polyps with diameters ranging from 3 mm to 15 mm were created and randomly distributed. There was a total of 60 polyps; 20 polyps were 3 to 5 mm in size, 21 polyps 6 to 9 mm, and 19 polyps 10 to 15 mm. The pig colons were sealed, distended with air, submerged in water, and were arranged to mimic the in vivo arrangement. CT was performed using a 4-row multidetector CT scanner with collimations of 1, 2.5, and 5 mm, a pitch of 1.75, and mA of 100. A low-dose protocol (mA of 50) was added with a collimation of 1 mm. Two blinded observers independently analyzed the datasets.


RESULTS
: The overall sensitivities of CT colonography were 94.2% with 1-mm collimation, 80% with 2.5-mm collimation, and 75% with 5-mm collimation. Considering the sensitivity of each protocol for the size of the polyps, the 1-mm collimation protocol had a sensitivity of 87.5% for 3- to 5-mm polyps, 95.2% sensitivity for 6- to 9-mm polyps, and 100% sensitivity for 10- to 15-mm polyps; the 2.5-mm protocol had 50%, 92.9%, and 97.4% sensitivities, respectively; and the 5-mm protocol had 47.5%, 88.1%, and 89.5% sensitivities, respectively, for the respective polyp size group. A significant difference in sensitivity among the protocols was present in the 3- to 5-mm polyps. No significant difference was seen between the standard- and the low-dose protocols.


CONCLUSIONS
The sensitivity of multidetector CT colonography for detecting polyps larger than 5 mm is robust over a range of collimation in pig colonic phantoms. However, reliable detection of polyps 5 mm or smaller requires a 1-mm collimation. Sensitivity is not influenced by lowering the mA from 100 to 50.
Won
Hyung Jin
HJ
Department of Radiology, Asan Medical Center, University of Ulsan, College of Medicine, Seoul, Korea.
Choi
Byung Ihn
BI
Kim
Se Hyung
SH
Kim
Young Il
YI
Youn
Byung Jae
BJ
Han
Joon Koo
JK
D000818:Animals; D003111:Colonic Polyps / Q000000981:diagnostic imaging*; D023881:Colonography, Computed Tomographic; D012680:Sensitivity and Specificity; D013552:Swine