Dynamic contrast-enhanced magnetic resonance imaging and diffusion-weighted imaging in the activity staging of terminal ileum Crohn's disease

Figure 1 A 41-year-old male with moderate active Crohn’s disease in the terminal ileum and a Crohn’s Disease Activity Index of 267 and Crohn’s Disease Endoscopic Index of Severity of 12. A: Terminal ileum demonstrates wall thickening and increased signal on axial T2-weighted image; B: Terminal ileum wall has a high signal. Axial diffusion-weighted imaging image (b = 800 s/mm²) demonstrates high signal (arrow) in the same bowel segment. Region of interest (ROI) for the inflammatory bowel wall shows that apparent diffusion coefficient = 1.11×10^-3 mm²/s; C: ROI for the inflammatory bowel wall shows that K^trans = 0.10 min^-1 (K_ep = 0.87 min^-1, V_e = 0.11); D: In contrast, ROI of the normal appearing ileal loop shows that K^trans = 0.01 min^-1 (K_ep = 0.80 min^-1, V_e = 0.02); E: The contrast concentration curve of inflammatory bowel is plotted as ROI (line with circle) and fitted with the model (line); F: The contrast concentration curve of normal loop is plotted as ROI (line with circle) and fitted with the model (line). ROI: Region of interest.

Figure 2 A 42-year-old male with remission of Crohn’s disease in the terminal ileum and a Crohn’s Disease Activity Index of 108 and Crohn’s Disease Endoscopic Index of Severity of 2. A: Axial T2-weighted image shows mural thickening and hyperintensity in the terminal ileum (arrow); B: Axial diffusion-weighted imaging image (b = 800 s/mm²) demonstrates high signal (arrow) in the same bowel segment. Regions of interest (ROI) for the inflammatory bowel wall shows that apparent diffusion coefficient = 1.89×10^-3 mm²/s; C: K^trans map is obtained through the relevant phase. The perfusion parameters of the ROI placed in the terminal ileum is calculated by TCM (K^trans = 0.18 min^-1); D: K_ep map is obtained through the relevant phase. The K_ep of the ROI placed is 0.98 min^-1; E: V_e map is obtained through the relevant phase. The V_e of the ROI placed is 0.19; F: The contrast concentration curve is plotted as ROI (line with circle) and fitted with the model (line). ROI: Region of interest.

Figure 3 The K^trans, K_ep, V_e and apparent diffusion coefficient among the three groups. A: Bar charts show increasing K^trans, between the normal ileal loop (NIL) and the inflamed terminal ileum (ITI) and pairwise comparisons of them is different (all P < 0.001); B: K_ep between the NIL and the ITI is different (all P < 0.001); C: V_e between the NIL and the ITI is different (all P < 0.001); D: Apparent diffusion coefficient between the NIL and the ITI is different (all P < 0.001). Furthermore, increasing K^trans, K_ep and V_e are shown with activity of CD in remission, mild and moderate-severe CD while decreasing apparent diffusion coefficients are shown (all P < 0.001). ^aP indicate difference with P < 0.001. NIL: Normal ileal loop; ITI: Inflamed terminal ileum.

Figure 4 Correlations of inflamed terminal ileum with Crohn’s Disease Activity Index and Crohn’s Disease Endoscopic Index of Severity in Crohn’s disease. A and C: Scatterplots show positive correlation of K^trans, K_ep and V_e and negative correlation of apparent diffusion coefficient in inflamed terminal ileum of Crohn’s disease patients with Crohn’s Disease Activity Index score; B and D: Positive correlation of K^trans, K_ep and V_e and negative correlation of apparent diffusion coefficient in inflamed terminal ileum of Crohn’s disease patients with Crohn’s Disease Endoscopic Index of Severity score. CDAI: Crohn’s Disease Activity Index; CDEIS: Crohn’s Disease Endoscopic Index of Severity; ADC: Apparent diffusion coefficient.

Figure 5 Receiver operating characteristic curve analysis. Receiver operating characteristic curve analysis shows high accuracy of K^trans (areas under the curve [AUC] = 0.76), V_e (AUC = 0.78), K_ep (AUC = 0.68), apparent diffusion coefficient (AUC = 0.89) and Magnetic Resonance Index of Activity (AUC = 0.91) for differentiating inactive from active Crohn’s disease. Accuracy of combining the K^trans, K_ep and V_e (AUC = 0.80) is higher than the individual dynamic contrast-enhanced magnetic resonance imaging parameters. The highest AUC is observed when combining dynamic contrast-enhanced magnetic resonance imaging and diffusion-weighted imaging parameters (AUC = 0.95). ROC: Receiver operating characteristic; ADC: Apparent diffusion coefficient; DCE-MRI: Dynamic contrast-enhanced magnetic resonance imaging; MaRIA: Magnetic Resonance Index of Activity.

Figure 6 Bland-Altman analysis for the intraclass and interclass coefficients. A: Bland-Altman analysis of the difference between the two observers’ average results for K^trans; B: Bland-Altman analysis of the difference between the two observers’ average results for apparent diffusion coefficient; C: Bland-Altman analysis of the difference between the two observers’ average results for K_ep. ADC: Apparent diffusion coefficient; SD: Standard deviation.