ABSTRACT
Objective To explore the value of various diffusion parameters obtained from monoexponential, biexponential and stretched exponential diffusion-weighted imaging models in assessing hepatic fibrosis in chronic hepatitis B(CHB). Methods A total of 52 patients who were diagnosed hepatitis B by the markers of hepatitis and were confirmed by liver biopsy pathology were prospectively recruited between June 2014 and May 2016 in People's Hospital of Henan Province. Concomitantly, 30 healthy volunteers who had no history of hepatitis B and liver dysfunction were enrolled in the control group. All patients underwent multi-b values DWI on a 3.0 T MRI unit. ADC was calculated by using the monoexponential model. True diffusion coefficient(Dt),pseudo diffusion coefficient(Dp)and fraction of perfusion(f)were calculated by using the biexponential model.Distributed diffusion coefficient(DDC)and water molecular diffusion heterogeneity index(α)were calculated by using the stretched exponential model. Liver biopsy specimens were staged according to the degree of hepatic fibrosis (S0 to S4). The Kruskal-Wallis test was employed for the comparison of each parameter among the control group and the fibrosis stage groups. The Mann-Whitney U test was adopted to compare each parameter between fibrosis stage≤S1and≥S2,between≤S2 and≥S3.Spearman rank correlation coefficients were obtained to assess the correlation of the parameters with the fibrosis stages.ROC analysis was used to evaluate the performance of various parameters in predicting stage≥S2 and≥S3.Results The hepatic fibrosis stage distributions were as follows:1 cases with S0,9 cases with S1,22 cases with S2,11 cases with S3,9 cases with S4.ADC,Dt,f and DDC values all showed significant difference among the control group and groups S1,S2,S3,S4(all P<0.05), while Dp and α values showed no significant difference(P>0.05). Dt, DDC and ADC showed a moderate negative correlation with the fibrosis stage(r=-0.630,-0.603 and-0.464,respectively,all P<0.01),and f showed a mild negative correlation with the fibrosis stage(r=-0.379,P<0.05),while Dp and α values showed no correlation with the fibrosis stages(all P>0.05).The ADC, Dt, f and DDC values all showed significant difference between stage≥S2 and≤S1,between stage≥S3 and≤S2(all P<0.05),and the parameter values of the former were greater than those of the latter. While Dp and α values showed no significant difference among both groups(all P>0.05).The AUCs of ADC,Dt,f and DDC values for detecting fibrosis stage ≥S2 were 0.738,0.835,0.740 and 0.831, and the AUCs of ADC, Dt, f and DDC values for detecting fibrosis stage≥S3 were 0.716, 0.811, 0.672 and 0.798. Conclusion The Dt derived from biexponential and DDC derived from stretched exponential DWI could be useful for the staging of hepatic fibrosis in CHB.
ABSTRACT
Objective To investigate the value of stretched-exponential model of DWI in differential diagnosis of benign and malignant breast lesions.Methods Totally 58 patients with 63 breast lesions (33 benign,30 malignant lesions) were enrolled.All the patients underwent multiple b value DWI and dynamic contrast enhancement MRI (DCE-MRI) scans.The values of ADC,DDC and water molecular diffusion heterogeneity index (α) were calculated,and the time signal intensity curve (TIC) was obtained.All the parameters were compared between benign and malignant breast lesions.The diagnostic performance of different parameters was evaluated with ROC curve.Results ADC,DDC and α value of malignant lesions was (1.01±0.19)×10-3 mm2/s,(0.89±0.23)×10-3 mm2/s and 0.75±0.09,while of benign lesions was (1.41±0.27)× 10-3 mm2/s,(1.49±0.29)× 10-3mm2/s and 0.87±0.07,respectively.All 3 parameters in malignant lesions were lower than those in benign lesions (all P＜0.01).Taking 1.22 × 10-3 mm2/s as the optimal threshold,the area under the curve (AUC) of DDC was the largest as 0.958,and the corresponding diagnostic sensitivity and specificity was 96.67％ and 81.82％,respectively.AUC value was 0.976 by combining DDC with TIC,and the corresponding diagnostic sensitivity and specificity was 93.33％ and 93.94％,respectively.Conclusion The stretched-exponential model DWI can differentiate breast lesions,and diagnostic performance of combination of DDC and TIC is better than ADC or DCE.