Characterization of Degree of Intestinal Fibrosis in Patients with Crohn Disease by Using Magnetization Transfer MR Imaging

Abstract

Purpose To evaluate the role of magnetization transfer (MT) magnetic resonance (MR) imaging for the characterization of intestinal fibrosis compared with contrast material-enhanced and diffusion-weighted MR imaging and its capability for differentiating fibrotic from inflammatory strictures in humans with Crohn disease (CD) by using surgical histopathologic analysis as the reference standard. Materials and Methods Institutional review board approval and informed consent were obtained for this prospective study. Abdominal MT imaging, contrast-enhanced imaging, and diffusion-weighted imaging of 31 consecutive patients with CD were analyzed before elective surgery. The bowel wall MT ratio normalized to skeletal muscle, the apparent diffusion coefficient (ADC), and the percentage of enhancement gain were calculated; region-by-region correlations with the surgical specimen were performed to determine the histologic degree of fibrosis and inflammation. The performance of MT imaging was validated in five new patients. One-way analysis of variance test, Spearman rank correlation, and receiver operating characteristic curve were used for statistical analysis. Results Normalized MT ratios strongly correlated with fibrosis scores (r = 0.769; P = .000) but did not correlate with inflammation scores (r = -0.034; P = .740). Significant differences (F = 49.002; P = .000) in normalized MT ratios were found among nonfibrotic, mildly, moderately, and severely fibrotic walls. The normalized MT ratios of mixed fibrotic and inflammatory bowel walls were significantly higher than those of bowel walls with only inflammation present (t = -8.52; P = .000). A high accuracy of normalized MT ratios was shown with an area under the receiver operating characteristic curve (AUC) of 0.919 (P = .000) for differentiating moderately to severely fibrotic bowel walls from nonfibrotic and mildly fibrotic bowel walls, followed by ADC (AUC, 0.747; P = .001) and the percentage of enhancement gain (AUC, 0.592; P = .209). The sensitivity, specificity, and AUC of MT imaging for diagnosing moderate to severe fibrosis in the validation data set were 80% (12 of 15), 100% (three of three), and 0.9 (P = .033), respectively. Conclusion MT imaging outperforms ADC and contrast-enhanced imaging in detecting and distinguishing varying degrees of bowel fibrosis with or without coexisting inflammation. MT imaging could potentially be used as a method to differentiate fibrotic from inflammatory intestinal strictures in patients with CD. RSNA, 2018 Online supplemental material is available for this article.

Fibrostenotic strictures in Crohn’s disease

“…However, the low performance in discriminating among none, mild, and moderate fibrosis might limit the use of delayed enhancement MRE. 1,124,127 Novel magnetic resonance (MR) techniques to detect fibrotic stricture include diffusion-weighted imaging (DWI)-MRE and magnetization transfer-MR (MT-MR). DWI can be completed quickly without intravenous contrast and provide a quantitative index, for example, apparent diffusion coefficient (ADC), which reflects the rate of water diffusion through the tissues.…”

Differentiation of fibrotic and inflammatory component of Crohn’s disease-associated strictures

“…20 Table 1 summarizes the main characteristics of novel imaging modalities that had been investigated to detect and quantify fibrosis in CD, whereas Table 2 provides the evidence obtained in studies testing the techniques against histopathology. [9][10][11][13][14][15][21][22][23][24][25] To date, all the evidence comes from single-center studies with relatively small samples. Before these noninvasive quantitative imaging biomarkers can be widely implemented, further multicenter large-scale studies are needed to establish cutoff values, test their reproducibility, and determine their degree of interobserver agreement.…”

Comparison of Three Magnetization Transfer Ratio Parameters for Assessment of Intestinal Fibrosis in Patients with Crohn's Disease

“…The quantitative parameters of MTI (MTR and normalized MTR) were both reported to be capable of characterizing the severity of bowel fibrosis in animal or human CD (2,3,7,9). Our preliminary results and those of other studies showed that a higher MTR or normalized MTR of the thickened intestinal wall, similar to that of the muscle presenting the highest MTR in human tissue, indicated a higher fibrotic composition of the lesion (2,3,9). However, in clinical practice, sometimes a relatively higher MTR or normalized MTR might be observed in the normal intestinal wall, which may hinder interpretations of the result.…”

“…However, a low MTR may be detected in severely fibrotic bowel walls with a similarly low MTR of muscle in some cases due to individual differences. To facilitate the comparison between individual cases, the MTR of the affected bowel wall was divided by the MTR of the muscles on the same image to obtain a normalized MTR to minimize individual variation (3,9). This normalized MTR also showed a high accuracy in detecting and further stratifying bowel fibrosis in CD (9).…”

“…To facilitate the comparison between individual cases, the MTR of the affected bowel wall was divided by the MTR of the muscles on the same image to obtain a normalized MTR to minimize individual variation (3,9). This normalized MTR also showed a high accuracy in detecting and further stratifying bowel fibrosis in CD (9). However, the approach using MTR or normalized MTR on the pathologic bowel wall to directly assess fibrosis does not take into account the already existing MTR of the normal intestine.…”