Subtraction CT colonography: feasibility in an animal model.
OBJECTIVE
To determine, in an in vitro animal model, the feasibility of subtracting residual faecal material, during virtual colonoscopy, by uniform mixing of the colonic contents with barium.


METHODS
Segments of animal colon containing simulated soft-tissue polyps, measuring 3-10 mm, were filled with a faecal substitute consisting of a barium and peanut butter mix that had an attenuation value greater than 200 Hounsfield units. The colonic segments were then examined by CT using 3-10 mm beam collimations, and at pitch factors of 1 and 2. Using subtraction cut-off levels varying from 100-250 Hounsfield units, the barium and peanut butter mix was then subtracted to reveal the underlying polyps.


RESULTS
Our optimal technical parameters required 3-mm beam collimation, a helical pitch factor of 2, reconstruction intervals of 3 mm, and a subtraction cut-off level of 150 Hounsfield units. The subtraction technique, in this animal model, had a sensitivity of 94% and a specificity of 80% for polyps measuring greater than 3 mm.


CONCLUSIONS
In this limited animal model, the subtraction technique utilized was technically feasible and had an acceptable sensitivity.
Department of Radiology, The University of Texas, M.D. Anderson Cancer Center, Houston 77030, USA.
D G
DG
Sheppard
R B
RB
Iyer
D
D
Herron
C
C
Charnsangavej
D000818:Animals; D001466:Barium Sulfate; D003111:Colonic Polyps / Q000000981:diagnostic imaging*; D003113:Colonoscopy; D003287:Contrast Media; D004195:Disease Models, Animal; D004285:Dogs; D005240:Feasibility Studies; D005243:Feces; D012680:Sensitivity and Specificity; D013552:Swine; D014057:Tomography, X-Ray Computed / Q000379:methods*
D003287:Contrast Media; D001466:Barium Sulfate