Diagnostic Value of Diffusion-Weighted Imaging and Apparent Diffusion Coefficient in Assessment of the Activity of Crohn Disease: 1.5 or 3 T

Abstract

Objective: The objective of this study is to evaluate the role of diffusion-weighted imaging (DWI) in assessment of the activity of Crohn disease (CD) and to explore differences between DWI in 3 T and 1.5 T.

Methods: Postcontrast magnetic resonance enterography with DWI of 72 patients with pathological proof of CD was retrospectively evaluated for restricted diffusion qualitatively and quantitavely in 3 T (n = 40) and 1.5 T (n = 32). Magnetic resonance activity score of 7 or higher was used as reference of activity.

Results: Fifty-five patients had active lesions. Diffusion-weighted imaging hyperintensity showed sensitivity (100%, 100%) and specificity (88.89%, 100%) in 1.5/3 T for activity assessment. Mean ± SD apparent diffusion coefficient for active lesions was 1.21 ± 0.42 and 1.28 ± 0.59 × 10 mm/s in 1.5 and 3 T, respectively. The proposed cutoff values of 1.35 and 1.38 × 10 mm/s in 1.5 and 3 T, respectively, had sensitivity (80%, 93%), specificity (100%, 90%), accuracy (88%, 93%), and no significant difference in accuracy between 1.5/3 T (P = 0.48).

Conclusions: Diffusion-weighted imaging hypersensitivity and apparent diffusion coefficient values accurately assessed the activity of CD. No significant statistical difference in diagnostic accuracy was detected between 1.5 and 3 T.

FIGURE 1

A 19-year-old female with active CD of terminal ileum. A, The axial T2- and (B) contrast-enhanced T1-weighted images show marked mural T2 hyperintensity and contrast enhancement with thickened bowel wall in the terminal ileum (white arrows). Grade 3 hyperintensity on the axial diffusion-weighted MRI with b = 800 s/mm² (white arrow in C) and hypointensity on corresponding ADCs map (black arrow in D). The mean ADC in the inflamed bowel wall to be 0.66 × 10⁻³ mm²/s.

FIGURE 2

A 31-year-old female with inactive CD. A, The axial T2- and (B) contrast-enhanced T1-weighted images showed mural thickness of terminal ileum (3 mm). Grade 2 hyperintensity on the axial diffusion-weighted MRI with b = 800 s/mm² (white arrow in C), yet no significant hypointensity on corresponding ADCs map (white arrow in D). The mean ADC in the inflamed bowel wall to be 1.8 × 10⁻³ mm²/s.

FIGURE 3

Receiver operating characteristics curve of DWI hyperintensity in 1.5 T; area under the ROC curve, 0.99. Figure 3 can be viewed online in color at www.jcat.org.

FIGURE 4

Receiver operating characteristics curve of DWI hyperintensity in 3 T; area under the ROC curve, 1. Figure 4 can be viewed online in color at www.jcat.org.

FIGURE 5

Receiver operating characteristics curve of mean ADC in 1.5 T; area under the ROC curve, 0.97. Figure 5 can be viewed online in color at www.jcat.org.

FIGURE 6

Receiver operating characteristics curve of mean ADC in 3 T; area under the ROC curve, 0.98. Figure 6 can be viewed online in color at www.jcat.org.