JNM: Low-dose FDG PET/CT enterography improves assessment in Crohn's

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Combining 18F-FDG PET and CT enterography (CTE) in a low-dose PET/CTE protocol provides a comprehensive imaging assessment of both disease activity and disease morphology in patients with Crohn's disease, according to a study published in the December issue of the Journal of Nuclear Medicine.

Thirteen patients with Crohn's disease were prospectively enrolled in the pilot study and underwent abdominal-pelvic PET/CTE using neutral oral and intravenous contrast medium. Paul B. Shyn, MD, from the department of radiology at Brigham and Women’s Hospital and Harvard Medical School in Boston led the study.

The effective dose from PET/CTE was 17.7 mSv for the first four patients and 8.31 mSv for the last nine patients, according to the researchers. Six patients underwent surgical resection of the bowel, and seven patients underwent colonoscopy with biopsies within 27 days of PET/CTE.

PET/CTE images and CTE images alone were each visually assessed for Crohn's disease involvement in 54 bowel segments with pathology correlation.

In three (23.1 percent) of 13 patients, FDG uptake using PET/CTE revealed active inflammation in a bowel segment not evident using CTE alone or revealed an enterocolic fistula missed with CTE. Visual interpretation of both PET/CTE and CTE images detected the presence of disease in all bowel segments with more than mild inflammation (sensitivity, 100 percent; specificity, 89.7 percent; positive predictive value, 78.9 percent; and negative predictive value, 100 percent), according to Shyn and colleagues.

The researchers noted that the correlation to inflammation grade per patient was the strongest for the SUVmax ratio (0.735) and SUVmax (0.67), as compared with the CTE score (0.62). Correlation with inflammation per bowel segment was higher for the CTE score (0.79) than the SUVmax ratio (0.62) or SUVmax (0.48). SUVmax correlated strongly with serum C-reactive protein (0.82), but CTE score did not.

“18F-FDG PET/CTE appears to improve the assessment of patients with Crohn's disease by confirming the presence of active inflammation when CTE findings alone are nonspecific,” wrote Shyn and colleagues.

The authors also noted that SUVmax and SUVmax ratio offer semiquantitative assessment of active inflammation that correlated well with histopathology grading of inflammation and serum C-reactive protein.

Low-dose 18F-FDG PET/CTE, compared with CTE, may improve the detection and grading of active inflammation in patients with Crohn's disease. PET/CTE also may reveal clinically significant findings, such as enterocolic fistula, not evident on PET or CTE alone, concluded Shyn and colleagues.