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PET/CT Enterography in Crohn Disease: Correlation of Disease Activity on CT Enterography with 18F-FDG Uptake

We combined 18F-FDG PET and CT enterography in a single examination and compared the level of 18F-FDG uptake measured by maximal standardized uptake value (SUVmax) with the CT enterography patterns of disease activity found in patients with Crohn disease (CD). Methods: Twenty-eight patients (mean age, 37.5 y; 11 male and 17 female) suspected of having active CD underwent PET/CT enterography. Abnormal bowel segments recognized on CT enterography were graded qualitatively for the presence of perienteric fat infiltration, the comb sign, and intramural attenuation and by quantitative measurements of mural enhancement (Hounsfield units) and thickness (mm). Also, for each patient, normal segments of the ileum and colon were noted, and CT enterography measurements of thickness and enhancement were obtained. For segments detected on CT enterography, a volume of interest was placed on the fused 18F-FDG PET scan, and the SUVmax was obtained. Results: Of the 28 patients with suspected active CD, 22 had 85 abnormal segments and 6 had no abnormal segments. SUVmax was significantly higher in the abnormal segments than in the normal segments (5.0 ± 2.5 [95% confidence interval, 4.5–5.5] and 2.1 ± 0.69 [95% confidence interval, 1.9–2.2], respectively; P < 0.0001). A good correlation was found between SUVmax with CT enterography measurements of mural thickness and enhancement (P < 0.00001). There was a significant difference in SUVmax between the 3 levels of disease activity found by intramural attenuation, perienteric fat infiltration, and the comb sign on CT enterography. SUVmax was significantly higher when there were intense CT enterography findings of active disease (P < 0.001). Conclusion: SUVmax assessment may allow an objective, reliable indication of the grade and severity of inflammation activity in abnormal segments of the bowel detected by CT enterography.