Colorectal polyps on portal phase contrast-enhanced CT colonography: lesion attenuation and distinction from tagged feces.
OBJECTIVE
The purpose of our study was to determine the attenuation of colorectal polyps on portal phase contrast-enhanced CT colonography (CTC) and evaluate whether enhanced polyps can be clearly distinguished from tagged feces during CTC review.


METHODS
Our institutional review board approved this study and waived patient informed consent. Forty-eight colonoscopy-proven polyps (6-20 mm) and 41 polypoid tagged feces (6-19 mm) were selected from contrast-enhanced CTC performed without (n = 37 examinations) and with (n = 10 examinations) fecal tagging, respectively. Scanning was performed 72 seconds after i.v. injection of 150 mL of contrast material at a rate of 2.5 mL/s. Fecal tagging consisted of three doses of 200 mL of 5% weight/volume (w/v) barium sulfate suspension taken at each meal the day before CTC. Attenuation of the polyps and tagged feces was measured. Four independent blinded radiologists reviewed the polyps and tagged feces at both wide (width, 1,500 H; level -400 H) and soft-tissue (width, 400 H; level, 20 H) window settings to distinguish them by using subjective visual assessment.


RESULTS
Polyp attenuation on the portal phase was not correlated with size (R = -0.003; p = 0.99) and was not different between histologic types (p = 0.884). Enhanced polyps (mean +/- SD, 119.9 +/- 25.3 H; range, 50-173 H) showed significantly lower attenuation than did tagged feces (1,521.4 +/- 683.6 H; range, 495-2,683 H) without any overlap (p < 0.0005). An 8-mm sessile adenomatous polyp was misinterpreted as tagged feces by one reviewer. The rest of the lesions were correctly interpreted by all reviewers, resulting in high interobserver agreement (kappa value, 0.988).


CONCLUSIONS
Polyp attenuation on portal phase contrast-enhanced CTC ranges from 50 to 173 H. Contrast-enhanced polyps are clearly and consistently distinguished from barium-tagged polypoid feces.
Lee
Seung Soo
SS
Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, 388-1 Poongnap2-Dong, Songpa-Gu, Seoul 138-040, Korea.
Park
Seong Ho
SH
Choi
Eugene K
EK
Kim
So Yeon
SY
Kim
Min-Ju
MJ
Lee
Kyoung Ho
KH
Kim
Young Hoon
YH
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003111:Colonic Polyps / Q000000981:diagnostic imaging*; D023881:Colonography, Computed Tomographic / Q000379:methods*; D003287:Contrast Media / Q000008:administration & dosage*; D005243:Feces; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011856:Radiographic Image Enhancement / Q000379:methods*; D012002:Rectal Diseases / Q000000981:diagnostic imaging*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D003287:Contrast Media