Can diffusion weighted imaging be used as an alternative to contrast-enhanced imaging on magnetic resonance enterography for the assessment of active inflammation in Crohn disease?

Abstract

The present study aimed to investigate the potential use of T2-weighted sequences with diffusion weighted imaging (DWI) in magnetic resonance (MR) enterography instead of conventional contrast-enhanced MR imaging (MRI) sequences for the evaluation of active inflammation in Crohn disease.Two-hundred thirteen intestinal segments of 43 patients, who underwent colonoscopy within 2 weeks before or after MR enterography were evaluated in this retrospective study. DWI sequences, T2-weighted sequences, and contrast-enhanced T1-weighted sequences were acquired in the MR enterography scan after cleaning of the bowel and using an oral contrast agent. First, the intestinal segments that had active inflammation in MR enterography were qualitatively evaluated in T2-weighted and contrast-enhanced T1-weighted sequences and then MR activity index (MRAI 1) and MRAI 2 were formed with and without contrast-enhanced sequences in 2 separate sessions.The correlation coefficient between contrast enhanced and DWI MR enterography scores (MRAI 1 and MRAI 2) of intestinal inflammation was 0.97 for all segments. In addition, separate correlation coefficients were calculated for terminal ileum, right colon, transverse colon, left colon, and rectum, and there was a strong correlation between the MRAI 1 and MRAI 2 scores of each segment (r = 0.86-0.97, P < .001). On the other hand, MR enterography had 88.7% sensitivity, 97.9% specificity, 95.5% positive predictive value, 94.6% negative predictive value, and 94.8% accuracy for detection of active inflammation in all intestinal segments in Crohn disease.DWI and T2-weighted sequences acquired with cleaning of the bowel can be used instead of contrast-enhanced MRI sequences for the evaluation of active inflammation in Crohn disease.

Figure 1

Graph showing the correlation between MRAI 1 and MRAI 2. MRAI = magnetic resonance activity index.

Figure 2

MR enterography images of an 18-yr-old female patient with severe active Crohn disease. Diffusion restriction is observed in the sigmoid colon in the coronal DWI (A) and ADC map (B) (arrows). Because the DWI signal increase is higher than in the lymph nodes, it scored 3 points on the MRAI. On the contrast-enhanced coronal T1-weighted image (C) of the same patient, mural thickening of the sigmoid colon and hyperenhancement that is more apparent in mucosa are seen (arrow). Because contrast enhancement is similar to that of the nearby vascular structures, it was scored as 3 points. Moreover, comb sign is observed on the coronal TRUFI sequence (D) (dashed arrow). ADC = apparent diffusion coefficient, DWI = diffusion weighted imaging, MR = magnetic resonance.

Figure 3

A 30-yr-old male patient with active Crohn disease. Diffusion restriction is observed in the distal and terminal ileum in the coronal DWI (A) and ADC map (B) (arrows) (scored 2 points on the MRAI). On the axial T2-weighted images (C) of the same patient, wall thickness, signal increase secondary to oedema, and perimural fluid ring are observed in the terminal ileum (arrow). On the coronal contrast-enhanced T1-weighted images (D), mucosal hyperenhancement is seen (scored 2 points on the MRAI). ADC = apparent diffusion coefficient, DWI = diffusion weighted imaging, MR = magnetic resonance.

Figure 4

MR enterography findings of a 37-yr-old male patient show active inflammation in the right colon (arrows). Marked diffusion restriction is observed in the intestinal wall in the right colon on axial DWI (A) and ADC map (B) (scored 3 points). Mucosal hyperenhancement is observed on contrast-enhanced axial T1-weighted image (C), and wall thickness is observed on axial fat-suppressed T2-weighted image (D). Because contrast enhancement was less than the nearby vascular structure, it was scored as 2 points. ADC = apparent diffusion coefficient, DWI = diffusion weighted imaging, MR = magnetic resonance.

Figure 5

A 30-yr-old male patient with active Crohn disease on a chronic basis in the descending colon. Diffusion restriction is observed in the colon wall on coronal DWI (A) and the ADC map (B) (arrows). Wall thickness, increased contrast enhancement, and strictures are observed on the coronal contrast-enhanced T1-weighted sequence (C) (arrows). Fibrofatty proliferation exists neighbouring the pathological intestinal segment on the coronal T2-weighted images (D) (dashed arrow). ADC = apparent diffusion coefficient, DWI = diffusion weighted imaging.