Automated measurement of colorectal polyp height at CT colonography: hyperplastic polyps are flatter than adenomatous polyps.
OBJECTIVE
Hyperplastic polyps are more difficult to detect than adenomatous polyps at CT colonography (CTC), and it has been theorized that this difference in detectability is because hyperplastic polyps are flatter. Using automated software that computes polyp height, we determined whether hyperplastic colonic polyps on CTC are indeed flatter than adenomatous polyps of comparable width.


METHODS
At three medical centers, 1,186 patients underwent oral contrast-enhanced CTC and same-day optical colonoscopy (OC) with segment unblinding for colorectal cancer screening. One hundred eighty-five of the patients had at least one hyperplastic or adenomatous polyp 6-10 mm visible at both OC and CTC, where size was determined by a calibrated guidewire at OC. To assess flatness, the heights of the polyps at CTC were measured using a validated automated software program. The heights and height-to-width ratios of the hyperplastic polyps were compared with those of the adenomatous polyps using a Student's t test (two-tailed, unpaired, unequal variance).


RESULTS
There were 176 adenomatous and 83 hyperplastic polyps visible at segment-unblinded OC. The fraction of these polyps that were measurable at CTC using the automated software was not significantly different for adenomatous versus hyperplastic polyps (158/176 [89.8%] vs 73/87 [83.9%], respectively; p = 0.2). The average height-to-width ratios using automated width measurements were 15% less for hyperplastic polyps: 0.39 +/- 0.20 (n = 158) and 0.33 +/- 0.19 (n = 73) for adenomatous and hyperplastic polyps, respectively (p = 0.03). When polyps of comparable OC size or CTC width were considered, the heights of hyperplastic polyps were up to 27% less than those of adenomatous polyps.


CONCLUSIONS
For 6-10 mm polyps of a given size as determined by OC or a given width at CTC, hyperplastic polyps tend to be flatter (i.e., have lower height) compared with adenomatous polyps.
Summers
Ronald M
RM
Radiology and Imaging Sciences, National Institutes of Health Clinical Center, Bethesda, MD 20892-1182, USA. rms@nih.gov
Liu
Jiamin
J
Yao
Jianhua
J
Brown
Linda
L
Choi
J Richard
JR
Pickhardt
Perry J
PJ
D018256:Adenomatous Polyps / Q000000981:diagnostic imaging / Q000473:pathology; D000368:Aged; D000704:Analysis of Variance; D001331:Automation; D003111:Colonic Polyps / Q000000981:diagnostic imaging* / Q000473:pathology; D023881:Colonography, Computed Tomographic; D003113:Colonoscopy; D003287:Contrast Media; D005260:Female; D006801:Humans; D006965:Hyperplasia; D008297:Male; D008875:Middle Aged; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D012189:Retrospective Studies; D012984:Software
D003287:Contrast Media