JNM: Nonlaxative PET/CT colonography shows promise

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Simultaneous PET acquisition during nonlaxative CT colonography is technically feasible, well tolerated and potentially improves diagnostic specificity for patients at higher risk of colonic neoplasia, according to a study published in the June issue of the Journal of Nuclear Medicine.

In the pilot study, 56 patients at high risk of colonic neoplasia underwent nonlaxative PET/CT colonography with barium fecal tagging within two weeks of scheduled colonoscopy.

Stuart A. Taylor, MD, from the department of medicine at the University College London in the U.K., and colleagues graded the colonic segmental distension from 1 (poor) to 3 (good).

The datasets were analyzed by a radiologist, experienced in CT colonography, and nuclear medicine physician in consensus and the diagnostic performance for standalone CT colonography and combined PET/CT colonography was compared with the reference colonoscopy.

Taylor and colleagues canvassed patient experience for 25 items pertaining to satisfaction, worry, and physical discomfort after both PET/CT colonography and colonoscopy.

The results showed that distension was good in 298 of 334 segments (89 percent), according to Taylor and colleagues.

Patients experienced more physical discomfort during colonoscopy than during PET/CT colonography and were more willing to undergo PET/CT colonography again, wrote Taylor and colleagues.

In the study, 21 patients had 54 polyps according to colonoscopy (10 with at least 1 polyp greater than 6 mm and 8 with at least 1 polyp greater than 10 mm). Taylor and colleagues found that of the 14 polyps 6 mm or greater, 12 were 18F-FDG–avid, including all those 10 mm or greater.

“CT colonography sensitivity for polyps 6 mm or larger was 92 percent and was not improved by the addition of PET. However, combined PET/CT colonography review improved per-patient positive predictive value for a polyp 10 mm or greater from 73 percent to 100 percent,” according to Taylor and colleagues.

“Use of this specialized technology will likely be reserved for patients intolerant of full bowel laxation in whom a sensitive and highly specific test is required to exclude significant colonic pathology,” concluded Taylor and colleagues.