MR-enterography with diffusion weighted imaging: ADC values in normal and pathological bowel loops, a possible threshold ADC value to differentiate active from inactive Crohn's disease

OBJECTIVE: The aim of our study was to compare the apparent diffusion coefficient (ADC) values of pathological bowel loops wall (pADC) with the ADC values of normal appearing ones (naADC) and to determine a discriminating threshold.PATIENTS AND METHODS: 60 patients were studied at our Institution through a MR-enterography that included free-breathing axial Diffusion Weighted Imaging (DWI) with two b (0 and 800 s/mm2) after histological diagnosis of active Crohn's disease (CD). The one (when unique) or the best analyzable (when multiple) pathological bowel loop was identified in each patient, on the basis of the MRI features: wall thickness, presence of mural oedema and wall contrast enhancement after contrast medium administration. A normal appearing bowel loop was used for comparison. ADC values were measured in consensus by two radiologists, and they were compared with t-test. The ADC threshold value for the differentiation between pathological and normal appearing bowel loops was determined.RESULTS: The pADC values were significantly lower than the naADC values (1.48 +/- 0.058 x 10(-3) mm(2)/s versus 3.525 +/- 0.07 x 10(-3) mm(2)/s; p < 0.05). A threshold of 2.416 x 10(-3) mm(2)/s showed 100% sensitivity and 100% specificity for the discrimination between normal and pathological bowel loops.CONCLUSIONS: In patients with active CD the ADC values of the pathological bowel wall are significantly lower than those of normal appearing bowel loops. A threshold of ADC value of 2.416 10(-3) mm(2)/s could discriminate normal from pathological bowel loops.