A diffusion kurtosis imaging based nomogram for assessment of bowel fibrosis in patients with Crohn disease / 中华放射学杂志

Objective:To explore the diagnostic efficacy of nomogram based on multi-parameter MRI for assessment of bowel fibrosis in patients with Crohn disease（CD).Methods:The clinical and imaging data of CD patients diagnosed by surgical histopathology in the First Affiliated Hospital of Sun Yat-sen University from June 2015 to March 2018 were prospectively collected. All the patients underwent conventional MRI and diffusion kurtosis imaging（DKI) within 2 weeks before surgery. Patients who underwent surgery between June 2015 and September 2017 were included in the model building group, and those who underwent surgery between October 2017 and March 2018 were included in the model validation group. We measured the apparent diffusion coefficient（ADC) from monoexponential model of diffusion-weighted imaging（DWI), apparent diffusional kurtosis（K app), and apparent diffusion for non-Gaussian distribution（D app) from non-Gaussian DKI model, and observed T 2WI signal intensity and enhancement pattern of the same segment. One to three intestinal specimens per patient were stained with Masson′s trichrome for the histological grading of fibrosis. Correlations between qualitative/quantitative MRI indexes and histological grades were evaluated using the Spearman rank test. Multivariate logistic regression analysis was performed to identify independent factors to be included into the nomogram for predicting the degree of bowel fibrosis and its diagnostic performance was assessed by internal and external validation. Results:A total of 40 CD patients were included, including 31 in the model construction group and 9 in the model verification group. A total of 81 intestinal specimens from 31 patients were graded as none-to-mild bowel fibrosis（ n=32) and moderate-to-severe bowel fibrosis（ n=49) according to a scoring system of fibrosis. In the training cohort, the K app value of moderate-to-severely fibrotic bowel walls was significantly higher than that of none-to-mildly fibrotic bowel walls, and the D appand ADC values of moderate-to-severely fibrotic bowel walls were significantly lower than those of none-to-mildly fibrotic bowel walls（ Z=-5.999, -4.521 and -3.893; P<0.001). There was no significant difference in T 2WI signal intensity or enhancement pattern between these two groups（χ2=1.571 and 0.103; P>0.05). Moderate and mild correlations of histological fibrosis grades with K appand D app( r=0.721 and -0.483; P<0.001), and a mild correlation with ADC（ r=-0.445, P<0.001) were found. Independent factors derived from multivariate logistic regression analysis to predict the degree of bowel fibrosis were K app and D app. Internal and external validation revealed good performance of the nomogram with concordance index of 0.901（95% confidence interval, 0.824-0.978) and 1.000, respectively, for differentiating none-to-mild from moderate-to-severe fibrosis. Conclusion:The DKI-based nomogram can be used to evaluate the bowel fibrosis in CD patients and provides a visual and simple prediction method for clinic.

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

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.

The correlation between intravoxel incoherent motion diffusion weighted MRI and intestinal inflammation and fibrosis in Crohn disease / 中华放射学杂志

Objective To determine the correlation between intravoxel incoherent motion (IVIM) parameters and both histologic inflammatory and fibrotic grades of Crohn disease (CD) in adults. Methods Prospectively, 17 patients (77 lesions) with a clinical and pathological diagnosis of CD in the first affiliated hospital of sun yat-sen university from July 2015 to June 2016 underwent MRE 15 days before surgery. All patients underwent T2WI, IVIM and enhanced MRI and calculated IVIM parameters include diffusion-related coefficient (D), perfusion-related coefficient (D*) and perfusion-related fraction (f). Histological intestinal inflammation and fibrosis was scored using the surgical histopathology as reference standard and further divided into mild-moderate (score 1 to 2) and severe (score 3 to 4) groups. Intestinal microvessel density (MVD) were also analyzed. Differences in IVIM parameters among different histological inflammation and fibrosis grades were assessed with the Kruskal-Wallis test. The Wilcoxon test was used for assessing differences in f between mild-moderate and severe fibrosis. The bivariate correlations between IVIM parameters and histological inflammation and fibrosis grades were analyzed using partial correlation . The bivariate correlations between IVIM parameters and MVD were analyzed using Spearman rank correlation. The areas under the receiver operating characteristics curves (AUROC) were analyzed to evaluate the efficacy for distinguishing severe from mild-moderate fibrosis. Results Of 77 surgical specimens, there were 41 mild-moderate and 36 severe inflammatory bowel segments, along with 22 mild-moderate and 55 severe fibrotic bowel segments. Positive correlation was shown between histologic inflammatory and fibrotic scores (r=0.592, P<0.01). MVD (42.7 ± 39.9)/HP presented weak positive correlation with histologic inflammatory scores (r=0.332, P=0.003) while no correlation with histologic fibrotic scores (r=0.129, P=0.262) was presented. Neither the D nor the D* values significantly correlated with histologic inflammation or fibrosis (P>0.05) while the f value significantly correlated with both histologic inflammation and fibrosis (P<0.05). Significant correlation was present between the f value and histologic inflammatory and fibrotic scores, respectively (r=-0.280, -0.520;P<0.05). There was significant difference in the f value between mild-moderate and severe fibrosis(Z=-5.255,P<0.01). The AUROC for the f value to distinguish between patients with mild-moderate fibrosis and severe fibrosis were 0.885. Using a threshold fractional perfusion of 0.33, the sensitivity and specificity values were 95.5％ and 81.8％, respectively. No correlation between f, D and D*value with histologic fibrotic scores (r=0.129, P=0.262) was presented. Conclusion The f value derived from IVIM could help to evaluate the severity of intestinal inflammation and fibrosis CD in adults.