Utility Of Diffusion Weighted Mr Enterography In The Assessment Of Ileocecal Crohn's Disease

Part 1 Qualitative analysis of Diffusion Weighted MR Enterography with different b values in ileocecal Crohn's Disease and the selection of optimal b valuePurpose:To evaluate the different b values diffusion weighted image(DWI)in the ileocecal Crohn's disease(CD),and compare the image quality of different b values DWI to determine the optimal b value for the clinic application.Materials and Methods:Among October 2015 to December 2016,a total of 30 ileocecal Crohn's disease patients were underwent MR Enterography with 5 b values(400,600,800,1000,1200 s/mm~2)DWI in a 3.0T MR scanner.All the b values DWI images were sent to a workstation for analysis.Two abdominal radiologists who were blind to the message of DWI sequence and clinic data independently assessed the 5 b values DWI images:(1)imaging quality scores;(2)scores of the background signal intensity suppression;(3)the bowel visualization scores.Another experienced abdominal radiologist measured the lesions signal to noise ratio(SNR),lesion to psoas muscle contrast to noise ratio(CNR)and lesion to psoas muscle signal intensity ratio(SR)of the 5 b values DWI images.The DWI scores between different b values was compared by the Friedman test,and the one way ANOVA was used for the comparisons of SNR,CNR and SR.Results:The scores of the image quality were declined as the b value increased,while the scores of background signal intensity suppression were improved;the scores of image quality and background signal intensity suppression were different statistically between different b values DWI.When b value was 800 s/mm~2,the score of bowel visualization was the largest,different with other 4 b value DWI.The SNR and CNR were decreased apparently in the high b value DWI.When b value was increased from 400 to 800 s/mm~2,SR went up similarly;while as the further increasement of b value,the SR was decreased.Conclusions:In the diffusion weighted MR Enterography,when b value was 800 s/mm~2,the scores of image quality and background signal intensity suppression were superior;and the DWI image contrast was the largest.So the selection of b=800 s/mm~2 could contribute to the assessment of CD lesions.Part 2 Quantitative diffusion-weighted MR Enterography in ileal Crohn's disease: a systematic analysis of intra and interobserver reproducibilityPurpose: To evaluate intra and interobserver reproducibility of quantitative analysis for DW-MR Enterography in ileal CD.Materials and Methods: Forty-four subjects(21 with CD,and 23 control subjects)who undergone ileocolonoscopy and DW-MR Enterography(b=800s/mm~2)within one week were included.Two radiologists independently measured apparent diffusion coefficients(ADC)of terminal ileum and signal intensity ratio(SR)of terminal ileum to ipsilateral psoas muscle on b=800 s/mm~2 DWI images.Between and within reader agreements were assessed using intraclass correlation coefficients(ICC),coefficients of variation(Co V),and Bland-Altman plots 95% limits of agreement(BA-LA Lo A).Diagnostic performances of ADC and SR for identifying inflamed terminal ileum from normal were evaluated by receiver operating characteristic(ROC)curve.Results: The intra and interobserver reproducibility of ADC(ICC: 0.952-0.984,Co V: 3.73-6.28%)and SR(ICC: 0.969-0.989,Co V: 3.51-4.64%)was excellent for CD.Agreement of ADC measurements was slightly less in control subjects(ICC: 0.641-0.736,Co V: 10.47-11.43%).SR of normal terminal ileum demonstrated high intra and interobserver reproducibility(ICC: 0.944-0.974,Co V: 3.73-6.28%).ADC and SR of two readers had outstanding diagnostic efficiencies(area under ROC: 0.923-0.988).Conclusions: Quantitative parameters derived from DW-MR Enterography(ADC and SR)achieved good to excellent intra and interobserver agreement with high diagnostic accuracy in assessment of the terminal ileum,and could serve as robust and efficient quantitative biomarkers for the evaluation of CD.Part 3 Comparison of standard and high b value diffusion-weighted MR Enterography for quantitative differentiation of ileocecal Crohn's disease and tumorsPurpose: To explore the quantitative analysis of diffusion-weighted imaging(DWI)in patients with Crohn's disease and intestinal tumors.Materials and Methods: Sixty-six patients with 30 tumors and 36 inflammations underwent MR Enterography with standard b value(800 s/mm~2)and high b value(2000 s/mm~2)DWI.Quantitative apparent diffusion coefficient(ADC)values and signal contrast ratio(SR)of lesions to psoas muscle were measured from the two b values DWI for all patients.The receiver operating characteristic(ROC)curve analysis was applied to determine diagnostic performances of ADC and SR for differentiating tumors from inflamed lesions.Results: ADC values of tumors were statistically lower than those of inflammatory lesions in 800 s/mm~2(P = 0.001)and 2000 s/mm~2(P < 0.001)DWI;while tumors demonstrated significantly higher SR values(800s/mm~2: 6.13±1.42;2000s/mm~2: 5.61±1.25)compared with inflammations(800s/mm~2: 4.31±1.05;2000s/mm~2: 3.45±0.79)(P < 0.001 in 800 and 2000 s/mm~2).Areas under ROC(AUC)of ADC and SR derived from high b value(0.849 for ADC,0.946 for SR)were superior to those from standard b value DWI(0.731 and 0.828,respectively).Comparing with ADC,SR values achieved better AUCs in both two b values DWI.Conclusions: The quantitative ADC and SR values could be used as the noninvasive modality to distinguish ileocecal tumors from inflammatory lesions.Utility of high b value DWI would improve the differentiation,and SR obtained from high b value DWI was the most promising quantitative parameter.