IVIM with fractional perfusion as a novel biomarker for detecting and grading intestinal fibrosis in Crohn's disease.

OBJECTIVES: Intravoxel incoherent motion (IVIM) diffusion-weighted magnetic resonance imaging (MRI) provides information on both perfusion and diffusion and has been used to evaluate Crohn's disease (CD) activity and fibrosis in children; however, there are no reports on its use in adults. We aimed to determine its value for detecting and grading intestinal fibrosis in adults with CD compared with contrast-enhanced imaging and traditional diffusion-weighted imaging using surgical histopathology as a reference standard. METHODS: Twenty-four adults with CD underwent preoperative IVIM, traditional diffusion-weighted, and contrast-enhanced imaging. Region-by-region correlations between MRI findings and histologic findings of the surgical specimens were performed. Imaging parameters including fractional perfusion, perfusion coefficient, and diffusion coefficient for IVIM and apparent diffusion coefficient value for traditional diffusion-weighted imaging and contrast-enhanced parameter of 95 bowel lesions were measured. Intestinal fibrosis was histologically scored from 0 to 3. RESULTS: The fractional perfusion (r = - 0.629, p < 0.001) and apparent diffusion coefficient values (r = - 0.495, p < 0.001) were significantly correlated with fibrosis scores. Fractional perfusion decreased following increases in fibrosis severity from mild, to moderate, to severe (p < 0.001). The area under the receiver operating characteristic curve for distinguishing moderate-severe from mild fibrosis was 0.876 (p < 0.001) for fractional perfusion, followed by 0.802 for apparent diffusion coefficient value (p < 0.001). Perfusion coefficient, diffusion coefficient, and contrast-enhanced parameter were uncorrelated with histological fibrosis. CONCLUSIONS: IVIM diffusion-weighted magnetic resonance imaging outperforms traditional diffusion-weighted and contrast-enhanced imaging in grading bowel fibrosis, and fractional perfusion may be a promising biomarker for fibrosis severity in adults with CD. KEY POINTS: • Intravoxel incoherent motion diffusion-weighted MRI outperforms contrast-enhanced imaging and traditional diffusion-weighted MRI for detecting and grading intestinal fibrosis in adult Crohn's disease. • The parameter fractional perfusion, a promising biomarker for fibrosis severity, may be beneficial for treatment planning and monitoring of bowel fibrosis in adult Crohn's disease. • Perfusion coefficient, diffusion coefficient, and the percentage of enhancement gain between 70 s and 7 min were uncorrelated with histological fibrosis.