Low-Dose ¹⁸F-FDG PET/CT Enterography: Improving on CT Enterography Assessment of Patients with Crohn Disease

Abstract

The purpose of this study was to evaluate the diagnostic efficacy of low-dose, combined 18 F-FDG PET/CT enterography (PET/CTE), compared with CT enterography (CTE) alone, in the assessment of patients with Crohn disease. Methods: Thirteen patients with Crohn disease were prospectively enrolled in this pilot study and underwent abdominal-pelvic 18 F-FDG PET/CTE using neutral oral and intravenous contrast medium. The effective dose from PET/CTE was 17.7 mSv for the first 4 patients and 8.31 mSv for the last 9 patients. Six patients underwent surgical resection of the bowel, and 7 patients underwent colonoscopy with biopsies within 27 d (mean, 12 d) of PET/CTE. PET/CTE and CTE images were each visually assessed for Crohn disease involvement in 54 bowel segments with pathology correlation. Extraintestinal findings were recorded. A CTE severity score, maximum standardized uptake value (SUVmax), SUVmax ratio, simplified endoscopic score, and clinical parameters were correlated with pathology inflammation grade, on a per-patient basis and on a per-bowel-segment basis, using Spearman correlation. Results: In 3 (23.1%) of 13 patients, 18 F-FDG uptake using PET/CTE revealed active inflammation in a bowel segment not evident using CTE (n 5 2) or revealed an enterocolic fistula missed with CTE (n 5 1). 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%; specificity, 89.7%; positive predictive value, 78.9%; and negative predictive value, 100%). Correlation to inflammation grade per patient was the strongest for the SUVmax ratio (0.735, P 5 0.004) and SUVmax (0.67, P 5 0.013), as compared with the CTE score (0.62, P 5 0.024). Correlation with inflammation per bowel segment was higher for the CTE score (0.79, P , 0.0001) than the SUVmax ratio (0.62, P , 0.0001) or SUVmax (0.48, P , 0.0001). SUVmax correlated strongly with serum C-reactive protein (0.82, P 5 0.023), but CTE score did not. Conclusion: Low-dose 18 F-FDG PET/CTE, compared with CTE, may improve the detection and grading of active inflammation in patients with Crohn disease. PET/CTE also may reveal clinically significant findings, such as enterocolic fistula, not evident on PET or CTE alone.

Role of 18F-fluorodeoxyglucose Positron Emission Tomography in the Monitoring of Inflammatory Activity in Crohnʼs Disease

“…The FDG dose of 185MBq was selected as the lowest dose that has provided meaningful data in a CD study 24 . Optimisation of radiation exposure was the reasoning behind the use of a low-dose CT for attenuation correction and segment localization, instead of a fulldose CT enterography protocol.…”

“…A target dose of 185MBq of 18 F-FDG in 10ml of normal saline was administered intravenously, followed by a saline flush. The patients then were asked to rest semi-recumbently in a quiet room, and, in keeping with similar protocols in the literature 10,11,[21][22][23][24] , they were given between 800-1200ml of an oral bowel distension, agent. 2.5% mannitol was used according to local protocol in our institution.…”

Imaging of the small bowel: Crohn’s disease in paediatric patients

“…Combining the morphologic patterns obtained by CT enterography with the 18 F-FDG metabolic activity obtained by PET, PET-CT enterography as a single test may provide accurately fused morphologic, physiologic, and metabolic imaging, useful in the diagnosis, evaluation of activity, follow-up, and objective assessment of CD [92] . Groshar et al [93] showed a statistically significant difference in mean SUV max among the different mural patterns revealed on CT enterography: intramural edema (active inflammation), intramural soft tissue attenuation (inflammatory infiltrate), and intramural fat (chronic inflamma- tion).…”

“…However, physiologic uptake of FDG by the intestine can lead to false positive results [94,95] . Moreover, the effective dose from PET-CT is actually too high for pediatric patients [92] .…”

The Role of Positron Emission Tomography in Inflammatory Bowel Disease

“…There is still limited evidence on these imaging methods both in adult and in pediatric IBO patients, but there is a good correlation between PET findings and disease activity (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29).…”