Clinical Application Value Of MRI In The Diagnosis Of Breast Lesions

Objective:Our study aimed to explore the clinical application value of magnetic resonance imaging(MRI)in the diagnosis of breast lesions.Materials and methods:1.Patients data:A total of 39 women(mean age 43.4 years,range from 13 to 65 years)with suspected breast cancer based on clinical examination,were included in the study from November 2006 to February 2008.All patients underwent mammography and or ultrasonography.In order to make the diagnosis more correctly, MRI scanning was performed in a week before the operation.All lesions were identified by histopathology.2.Scanning protocol:Using Philips Achieva 1.5T Nova Dual MR with SENSE-breast coil,all the patients were placed in prone position on the magnetic bores,and their breasts suspended in the breast coils.The MRI sequences include T₁ weighted imaging turbo spin echo(T₁WI/TSE),T₂ weighted imaging turbo spin echo (T₂WI/TSE),short TI inversion recovery(STIR),diffusion weighted whole body imaging with background body signal suppression(DWIBS),diffusion weighted imaging(DWI)and dynamic contrast-enhanced MR imaging(DCE-MRI). 2.1 DCE-MRI:For dynamic contrast-enhanced MR imaging,T₁ high resolution isotropic volume excitation(THRIVE)sequence was used in the transverse plane.The unenhanced T₁ weighted imaging was followed by 15 dynamic contrast-enhanced sequences,after the intravenous bolus injection of 0.15 mmol/kg body weight of GD-DTPA(Magnevist)into a dorsal vein of hand at the rate of 2.5ml/s and a 15 ml saline solution flush at the rate of 2.0ml/s.2.2 DWI:Echo planar imaging(EPI)sequence was performed on four b values (125 s/mm²,250 s/mm²,375 s/mm² and 500 s/mm²)with the parameters as follows: repetition time(TR)/echo time(TE),2500ms/62ms;slice thickness,4 mm;slice gap, 1mm;field of view,220 min×220 mm;matrix,126×240;scan time,137s.3.Evaluation methods:3.1 DCE-MRh We acquired the breast lesions' morphologic features,time-signal intensity curve(TIC)and early enhancerhent rate respectively.According to their shapes,TIC was classified into typeâ… ,typeâ…¡and typeâ…¢.Typeâ… is steady enhancement.Typeâ…¡is plateau of signal intensity.Typeâ…¢is washout of signal intensity.3.2 DWI:DWI was obtained from the workstation.The ADC values were calculated according to ADC =[In(S₂/S₁)]/(b₂-b₁),where S₁ and S₂ are the low and high signal intensities in the regions of interest(ROI)obtained with different b values (125～0,250～0,375～0,500～0 s/mm²).4.Statistical assay:The Student t-test was used to test the significance between the enhancement rates of benign and malignant lesions.And the x²-test was used to test the significance of the curve type distributions on the benign and malignant lesions.One-way ANOVA and SNK(Student-Newman-Keuls)were used to analyze the differences among the mean ADC values of the malignant lesions,benign lesions and normal fibro glandular tissue.The data was analyzed using the software of SPSS 11.0, P<0.05 was used to indicate significance.Results:1.48 breast lesions were revealed on MR imaging in 39 cases including solitary lesions in 33 cases,multiple lesions in 6 cases.Of multiple lesions,unilateral multiple lesions in 4 cases,bilateral multiple lesions in 2 cases.31 lesions in 26 cases were malignant.17 lesions in 13 cases were benign.All lesions were identified by histopathology.2.Most of the breast lesions were low signal intensity on T₁ WI.Benign lesions' signal intensities range form high to low on T₂ WI,while higher T₂ signal intensity for a malignant lesion.The detection rates of breast lesions of the six sequences were 64.58%(31/48),72.92%(35/48),81.25%(39/48),93.75%(45/48),93.75%(45/48), 100%(48/48),respectively.3.The typical malignant features were irregular shape,spiculated margin and rim enhancement.With irregular shape,speculated margin or rim enhancement for a malignant lesion,the following diagnostic indices emerge:sensitivity were 90.32%, 83.87%,67.74%,respectively;specificity were 64.71%,82.35%,94.12%,respectively; accuracy were 81.25%,89.66%,95.45%,respectively;positive predictive value were 82.35%,89.66%,95.45%.4.The mean early enhancement rates(the first,second,third minute after injection of contrast agent)of benign and malignant lesions were 65.64%±436.45%, 133.81%±50.68%;101.46%±44.87%,141.61%±50.88%;116.48%±45.29%, 146.20%±50.59%.The early post-contrast signal intensity increase was stronger in malignant lesions.The mean early enhancement rates have significant differences between the malignant lesions and benign lesions(P < 0.05).With the first minute enhancement rate(after the injection of contrast agent)more than 90%for a malignant lesion,the sensitivity,specificity,accuracy and positive predictive value were 83.87%,76.47%,81.25%and 86.67%,respectively.5.The distribution of curve types for breast cancers was typeâ… 3.23%; typeâ…¡35.48%;typeâ…¢61.29%.The distribution of curve types for benign lesions was typeâ… 88.24%,typeâ…¡11.76%,typeâ…¢0%.The distributions proved significantly different(P < 0.05).The diagnostic indices for signal intensity time course were the sensitivity,specificity,and accuracy,which were 96.77%,88.24%,93.75%, respectively.6.There were significant differences among the ADC values of malignant lesions,benign lesions,and normal fibro glandular tissue(P<0.05).With the increasing of the b values,the mean signal intensities of all the lesions become lower on the DWI.The ADC values of malignant lesions were much lower than those of normal fibro glandular tissue and benign lesions,and the ADC values of benign lesions were lower than that of normal fibro glandular tissue.The malignant or benign lesions' ADC values have significant differences among the b values(P<0.05).If the upper bound of 95%confidence interval of the malignant lesions' ADC values was set as a differential level,when b value is 500 s/mm²,the sensitivity,specificity, accuracy and positive predictive value were 83.87%,88.24%,85.42%,92.86%, respectively,.Conclusion:1.Using 1.5T MR scanner with SENSE breast coils,breast lesions could be demonstrated clearly and the characteristic of the lesions could also be diagnosed correctly.2.DCE-MRI can not only demonstrate the morphologic features of the lesions (including size,shape,margin,numbers and so on),but also reflect local microcirculation information.The type of TIC is an important criterion in differentiating malignant lesions from benign lesions in dynamic breast MR imaging.3.With the b value increases,the ADC values of all lesions decreases;the ADC values of the malignant lesions are much lower than the benign lesions.DWI is an effective and sensitive imaging technique for detecting breast lesions,especially for malignant lesions.As an assistant technique to routine scanning and DCE-MRI,DWI can improve the accuracy of diagnosis.ADC value is an important parameter to distinguish malignant lesions from benign lesions.