Reliability of magnetic resonance enterographyand diffusion weighted imagingin assessment of active chronsdisease in children

Background: Chrons is a relapsing remitting disease that affects children and demands a reliable diagnostic tool to detect active episode with minimum hazards. Objectives: i- to assess the reliability of MR enterography, quantitative and qualitative DWI measurements done by radiologists of different experiences in assessment of disease activity in children, ii to explore if diffusion weighted imaging (DWI) can substitute contrast enhanced images. Methods: Post contrast MR Enterography with DWI of 32 patients suspected to have active chron's disease were retrospectively evaluated by 3 radiologists with different years of experience. Magnetic resonance score ≥7 was used as reference of activity. Results: 21 patients had active lesions. There was almost perfect inter-reader agreement regarding graded DWI hyperintensity (ICC)= 0.93. There was significant moderate correlation between graded DWI hyperintensity and MaRIA (r = 0.64),mMaRIA (r=0.65). DWI hyperintensity had sensitivity of 100%, specificity of 95.5% in detecting active disease. Mean ADC for active lesions was 1.4 ± 0.2 × 10-3 mm2 /s. A proposed cut-off 1.67 x10-3 mm2/sec had sensitivity of 100%, specificity 62.5. There was significant moderate inverse correlation between ADC values and MaRIA, mMaRIA, mural thickness and wall edema, while there was no significant correlation between ADC and ulcers or relative contrast enhancement. The 3 readers did not find significant difference in lesion visibility between (DWI + ADC) and (post contrast images). Conclusions: MRE with DWI is a reliable tool that accurately assessed activity of chron's disease, regardless the experience of readers. DWI is comparable to post contrast images in detection of active disease.