PET/MRI in paediatric inflammatory bowel disease - a prospective accuracy study

Abstract

Cross-sectional imaging supplements endoscopy in detecting disease manifestations in inflammatory bowel diseases (IBD). This study aimed to evaluate the accuracy of PET/MRI in a paediatric population suspected of IBD. This prospective study consecutively included patients aged 8-17 years under diagnostic evaluation for IBD. Forty-three patients underwent a PET/MRI scan and subsequent ileocolonoscopy, of whom 26 patients diagnosed with IBD participated in a follow-up scan, hereof 19 with Crohn's disease (CD), five with Ulcerative colitis and two with unclassified IBD. The results of PET alone, MRI alone, and PET/MRI combined were compared to a reference standard of endoscopy and histopathology. Of the 208 intestinal segments analysed, 109 showed inflammation, and 99 had no inflammation. In the per-segment analysis PET had a sensitivity of 0.83 (95% CI 0.73-0.93), specificity of 0.59 (95% CI 0.47-0.71), and area under the receiver operating characteristic curve (AUROC) of 0.73 (95% CI 0.67-0.80). MRI had a sensitivity of 0.52 (95% CI 0.41-0.64), specificity 0.89 (95% CI 0.82-0.96), and AUROC of 0.72 (95% CI 0.66-0.77). PET/MRI had a sensitivity of 0.83 (95% CI 0.74-0.94), specificity of 0.57 (95% CI 0.44-0.69), and AUROC of 0.77 (95% CI 0.71-0.84). At follow-up, PET and MRI scores decreased, and the change in MRI was able to identify patients with a clinical response. The accuracy of the PET/MRI scan in detecting inflammation in the terminal ileum and colon was moderate and not superior to either modality alone. With technological advances and combined reading, PET/MRI may still be valuable in selected cases.

Keywords: Crohn's disease; Positron emission tomography; Ulcerative colitis; adolescents; children; magnetic resonance imaging.

Figure 1

Flowchart for study participation.

Figure 2

Illustrative abdominal images. Example of increased PET uptake and bowel wall thickening in the colon of a 14‐year‐old patient diagnosed with CD. (a) PET image with grade 3 uptake in the transverse colon (arrow); (b) Coronal MRI images with increased bowel wall thickness in the transverse colon (arrow); (c) Hybrid PET/MRI images with signs of inflammation (arrow).

Figure 3

Receiver operating characteristic curves. PET, MRI, and PET/MRI. PET/MRI is defined as PET grade zero (+0) if PICMI ≤5 and plus one (+1) if PICMI >5.

Figure 4

Changes PET, MRI and PET/MRI according to response to treatment. Change in ΔPET, ΔMRI and ΔPET/MRI in clinical responders (R) and non‐responders (NR) respectively. The circles represent individual patients, while the box represents median and IQR.