CT colonography: Protocol optimization with multi-detector row CT--study in an anthropomorphic colon phantom.
OBJECTIVE
To determine optimal detector collimation, section thickness, and tube current for multi-detector row computed tomography (CT) colonography.


METHODS
An anthropomorphic colon phantom with simulated polyps of varying size (2, 6, 8, 10, and 12 mm) was examined by using multi-detector row CT with varying combinations of detector collimation (4 x 1.0 mm and 4 x 2.5 mm), dose per section (10, 20, 40, 60, 80, 100, and 140 mAs), and section thickness/reconstruction interval (1.25/0.6, 2.0/1.0, 3.0/1.0, and 5.0/2.0 mm). Polyp depiction, longitudinal polyp distortion, and presence of rippling artifacts were assessed on reformatted three-dimensional endoluminal images by three reviewers.


RESULTS
Longitudinal distortion and rippling artifacts increased with increasing section thickness and use of broader detector collimation. Polyps 8 mm or larger were depicted with any combination of section thickness, detector collimation, and tube current. Depiction of polyps 6 mm or smaller depended on the detector collimation/reconstructed section thickness and was rated optimal for the 4 x 1.0-mm detector collimation with a section thickness of 1.25 mm. This was also observed for low-dose protocols. Polyps 6 mm or smaller that were not detected with 3-mm section thickness and 4 x 2.5-mm detector collimation were detected with 1.25-mm section thickness and 10 mAs.


CONCLUSIONS
A narrow detector collimation with thin-section imaging (4 x 1.0-mm detector collimation, 1.25-mm section thickness) is a prerequisite for low-dose (10-mAs) multi-detector row CT colonography.
Wessling
Johannes
J
Department of Clinical Radiology, University of Muenster, Albert-Schweitzer-Strasse 33, 48 149 Muenster, Germany. weslingj@uni-muenster.de
Fischbach
Roman
R
Meier
Norbert
N
Allkemper
Thomas
T
Klusmeier
Jutta
J
Ludwig
Karl
K
Heindel
Walter
W
D016477:Artifacts; D023881:Colonography, Computed Tomographic / Q000379:methods*; D007417:Intestinal Polyps / Q000000981:diagnostic imaging*; D019047:Phantoms, Imaging; D014057:Tomography, X-Ray Computed / Q000379:methods*