Korean J Radiol.  2020 Mar;21(3):290-297. 10.3348/kjr.2019.0217.

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

Affiliations
  • 1Department of Radiology, The First Affiliated Hospital, Sun Yat-Sen University, Guangzhou, China. lixuehua803@163.com
  • 2Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, MO, USA.
  • 3Department of Gastroenterology, The First Affiliated Hospital, Sun Yat-Sen University, Guangzhou, China.

Abstract


OBJECTIVE
To establish a novel standardized magnetization transfer ratio (MTR) parameter which considers the element of the normal bowel wall and to compare the efficacy of the MTR, normalized MTR, and standardized MTR in evaluating intestinal fibrosis in Crohn's disease (CD).
MATERIALS AND METHODS
Abdominal magnetization transfer imaging from 20 consecutive CD patients were analyzed before performing elective operations. MTR parameters were calculated by delineating regions of interest in specified segments on MTR maps. Specimens with pathologically confirmed bowel fibrosis were classified into one of four severity grades. The correlation between MTR parameters and fibrosis score was tested by Spearman's rank correlation. Differences in MTR, normalized MTR, and standardized MTR across diverse histologic fibrosis scores were analyzed using the independent sample t test or the Mann-Whitney U test. The area under the receiver operating characteristic curve (AUC) was computed to test the efficacies of the MTR parameters in differentiating severe intestinal fibrosis from mild-to-moderate fibrosis.
RESULTS
Normalized (r = 0.700; p < 0.001) and standardized MTR (r = 0.695; p < 0.001) showed a strong correlation with bowel fibrosis scores, followed by MTR (r = 0.590; p < 0.001). Significant differences in MTR (t = −4.470; p < 0.001), normalized MTR (Z = −5.003; p < 0.001), and standardized MTR (Z = −5.133; p < 0.001) were found between mild-to-moderate and severe bowel fibrosis. Standardized MTR (AUC = 0.895; p < 0.001) had the highest accuracy in differentiating severe bowel fibrosis from mild-to-moderate bowel wall fibrosis, followed by normalized MTR (AUC = 0.885; p < 0.001) and MTR (AUC = 0.798; p < 0.001).
CONCLUSION
Standardized MTR is slightly superior to MTR and normalized MTR and therefore may be an optimal parameter for evaluating the severity of intestinal fibrosis in CD.

Keyword

Magnetization transfer imaging; Crohn's disease; Fibrosis; Magnetic resonance imaging

MeSH Terms

Crohn Disease*
Fibrosis*
Humans
Magnetic Resonance Imaging
ROC Curve

Figure

  • Fig. 1 Correlation between three MTRs and histologic bowel fibrosis scores. Normalized MTR (r = 0.700; p < 0.001) (A) and standardized MTR (r = 0.695; p < 0.001) (B) were strongly correlated with bowel fibrosis scores, followed by MTR (r = 0.590; p < 0.001) (C). MTR = magnetization transfer ratio

  • Fig. 2 36-year-old woman with severe Crohn's disease in terminal ileum. A. Axial T2-weighted image and (B) axial contrast-enhanced T1-weighted image show marked bowel wall thickening and luminal stenosis with hyper-enhancement at terminal ileum (arrows). C–E. Axial MT imaging without (C) and with (D) MT pulse as well as pseudo-color MTR map <(E) indicate that MT effect of terminal ileum (arrows; ROIs, 1–3; MTR, 44.2%; yellow-blue) is higher than that of normal small intestinal wall (hollow arrows; ROIs, 4–6; MTR, 26.0%; dark blue) and close to that of skeletal muscles (arrowheads; ROIs, 7–9; MTR, 52.0%; yellow). Averages of standardized MTR and normalized MTR of involved bowel wall are 0.70 and 0.85, respectively. F. Gross specimen from surgical excision demonstrates marked thickening of bowel wall with obvious luminal stenosis (arrows). G. Masson's trichrome staining (magnification: × 20) displays severe intestinal fibrosis (arrow; blue area) with fibrosis score of 3. MT = magnetization transfer, ROI = region of interest

  • Fig. 3 Box plots showing differences of three MTRs between mild-to-moderate and severe bowel fibrosis. Significant differences in MTR (t = −4.470; p < 0.001) (A), normalized MTR (Z = −5.003; p < 0.001) (B), and standardized MTR (Z = −5.133; p < 0.001) (C) were found between mild-to-moderate and severe bowel fibrosis.

  • Fig. 4 ROC curve analysis for differentiating severe bowel fibrosis from mild-to-moderate fibrosis. ROC curve analysis shows that standardized MTR is highly accurate with AUC of 0.895 in distinguishing severe intestinal fibrosis from mild-to-moderate intestinal fibrosis, followed by normalized MTR (AUC = 0.885) and MTR (AUC = 0.798). AUC = area under ROC curve, ROC = receiver operating characteristic


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