PET/MRI for evaluating subclinical inflammation of ulcerative colitis

To explore the utility of integrated positron emission tomography (PET) / magnetic resonance imaging (MRI) for evaluating subclinical inflammation in patients with ulcerative colitis (UC).

This prospective study was approved by the Institutional Review Board and informed consent was obtained. Between November 2015 and April 2016, 19 consecutive patients with UC in clinical remission were enrolled. These patients underwent 18F-fluorodeoxyglucose PET/MRI (3T) and colonoscopy. Serum high-sensitivity C-reactive protein (hs-CRP) and fecal calprotectin (FC) levels were also obtained. The findings of colonoscopy were graded using the Mayo endoscopic subscore. Quantitative (minimum apparent diffusion coefficient [ADC_min ] and maximum standardized uptake value [SUV_max ]), semiquantitative, and qualitative parameters of PET/MRI were evaluated and correlated with colonoscopic findings.

In per-segment analysis, ADC_min was significantly lower and SUV_max and ratio of SUV_max to ADC_min were significantly higher in the colonic segments with active inflammation (Mayo endoscopic subscore ≥2) (P < 0.05). Qualitative MRI score, PET activity grade, and PET/MRI score were also significantly higher in the colonic segments with active inflammation (P < 0.05). Among these parameters, the ratio of SUV_max to ADC_min exhibited the highest area under the receiver operating characteristic curve (AUC) (0.763). In per-patient analysis, the AUC of PET activity grade was 0.778, higher than those of hs-CRP (0.589) and FC (0.722). Using a combined index of FC and PET, an even higher AUC (0.867) was achieved.

PET/MRI is a potentially useful tool in identifying subclinical inflammation in patients with UC.

1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:737-745.