The Application Of Monoexponential,biexponential And Stretched-Exponential Diffusion-weighted MR Imaging In Evaluation Of Breast Lesions

Breast cancer is the top of the female malignant tumors in the developed countries like Europe and America,which is fairly common in women. But in recent years, the incidence of breast cancer increased year by year in big cities with a trend of younger age.Early detection and the accuracy for differentiating malignant breast tumors from benign breast tumors affected largely the choice of operation mode and prognosis.MRI is the most sensitive imaging technique for the detection of breast cancer.DWI as a noninvasive MRI technique can provide the informations about Brownian motion of water molecules and reflect the microscopic organization and cellularity of biologic tissue.The value of ADC obtained by the Monoexponential fitting model can quantitatively reflect the degree of water molecular limited diffusion,but its accuracy have been challenged because it is influenced easily by perfusion of microcirculation.The diffusion of water molecules(ADC-slow) and blood perfusion(ADC-fast) can be separated by Biexponential fitting model based the intravoxel incoherent motion(IVIM) theory,the value of f is the proportion of fast componant of diffusion.But the Biexponential fitting model has some limitations.There could be more diffuse component exists in addition to the composition of fast and slow diffusion,and the exchange between rapid composition and slow component also can not ignore.the Streched-exponential fitting model,which included the distributed diffusion coefficient(DDC) and the heterogeneity of intravoxel diffusion(?),which reflect the mean diffused rate and the complexity of tissues in vivo.The purpose of this study is to investigate the values of these parameters derived from Monoexponential,Biexponential and Stretched-Exponential Diffusion-weighted MR imaging in differentiation of breast lesions and the correlation of these parameters with prognostic factors for breast cancer to guide the treatment of breast cancer through the analysis of multi-b DWI and corresponding pathological datas in 54 patients. Materials and Methods:A total of 54 patients with pathologically confirmed included 30 malignant tumors,34 benign lesions and 30 normal fibroglandular tissues.ALL patients underwent T1 WI,T2WI,Dynamic enhancement and diffusion weighted magnetic resonance imaging(MRI) with multi-b values at a 3.0T magnetic resonance imaging unit.All parameters were measured at a workstation(Advantage Windows 4.5). Apparent diffusion coefficient(ADC)was calculated by using monoexponential analysis(b=0,800sec/mm2).Slow apparent diffusion coefficient(ADC-slow), fast apparent diffusion coefficient(ADC-fast), and perfusion fraction(f) were calculated using the biexponential model. Distributed diffusion coefficient(DDC) and water molecular diffusion heterogeneity index(?)were obtained from diffusion-weighted images using the stretched exponential model.All parameters were statistically compared among normal breast tissues, benign tumors and malignant tumors using Kruskal-Wallis rank sum test,Mann-Whitney U were used for further comparisons between specific group pairs.ADC values were compared with ADC-slow and DDC for different groups by paired Wilcoxon test.Correlations between ADC-value and ADC-slow?DDC were assessed by using Spearman rank correlation.The ability of these parameters in differentiation of benign and malignant breast lesions were analyzed by Receiver operating characteristic curve. Results:The ADC,ADC-slow,f,DDC and ? values were significantly different among the normal breast tissues,benign tumors and malignant tumors(P < 0.05).Further differential comparisons of the four parameters between each pair showed that the ADC,ADC-slow,f,DDC and ? values were significantly lower in malignant tumors than both in normal fibroglandular tissues and benign tumors(P<0.0167). The f and DDC had higher AUC(area under the receiver operating characteristic curve)values(0.688,0.657,respectively).The optimal cutoff values for ADC,ADC-slow,f,DDC were1.235×10-3mm2/s,0.428×10-3mm2/s,0.578,1.175×10-3mm2/s,0.721,respectively.T he DDC value showed higher specificity(0.636)and the f value had higher sensitivity(0.829).The ADC values of normal breast tissues,benign tumors and malignant tumors were significantly higher than ADC-slow and DDC.There were strong positive correlation between ADC and ADC-slow?DDC. Conclusion:The parameters derived from Biexponential and Stretched Exponential DWI could be helpful for differentiation between benign and malignant breast tumors.