| Title:The optimized b value of Breast Diffusion Weighted MRIPurpose:To optimize the b value of breast Diffusion-weighted MRI(DW-M RI) at 1.5T by comparing the apparent diffusion coefficient(ADC) of disease-free contralateral breast tissue and benign and malignant lesions and the signal-to-noise ratio(SNR) of images using different b value in the same patient.Materials and Methods:32 women with confirmed malignant(18) and benign (14)lesions were examined using EPI-DWI with different b values at 1.5T MR scanner.DW images were acquired in the transverse plane covering both breasts, TR/TE=8400ms/93.8ms,FOV=30cm;NEX=2,matrix=128×128;slice thickness=4mm,b= 0,50,100,200,400,600,800,1000,1200,1400,1600,1800, 2000,2200,2400,2600 s/mm2 respectively,The ADCs of the phantom and the disease-free contralateral breast tissues and benign and malignant lesions were calculated from the ADC map.SNR was calculated on DW images.The relation between SNR of images and the b value were analyzed.One-way analysis of variance was applied to compare the ADCs of malignant lesions with benign lesions and disease-free contralateral breast tissues.The difference in ADCs was compared between different b value.Results:The SNR of DWI dropped as b value increasing which responsible for the poor image quality,and there was an inverse correlation between SNR and b value.The ADCs of phantom stayed invariable when b value was in the range of 0～1400 s/mm2,while the ADCs of normal breast tissue dropped gradually as b value increasing,which may be explained by the effect of perfusion in breast tissue.Significant difference was observed in ADCs between malignant and benign lesions using the same b value.The difference was magnified when b value was set in the range of 800～1000s/mm2,while it become smaller in the condition of b value＞1400 s/mm2.Conclusion:For good image quality and valid differentiation between malignant and benign lesion,the optimized b value of DWI is in the range of 800～1000s/mm2.PartⅡDiffusion-weighted MR Imaging of breast mass and non-mass lesionPurpose:To evaluate Diffusion-weighted MR Imaging of breast mass and non-mass lesion in lesion characterization by comparing ADCs of malignanty with benignancy.Materials and Methods:236 pathology-confirmed breast lesions(155 malignanty,81 benignancy) and 221 disease-free contralateral breast tissues were examined using EPI-DWI(b values=0,1000 s/mm2);TR/TE=8400ms/93.8ms; FOV=30×30cm;matrix=128×128;ASSET=2,slice thickness=4mm.DCE-MR imaging was also performed for accurate location of the lesion using VIBRANT sequence.The mean ADC values of malignant and benign lesions and the disease-flee contralateral breast tissues were calculated from the ADC map for each patient.One-way analysis of variance was applied to compare the mean ADCs of malignant lesions with benign lesions and disease-flee contralateral breast tissues.The threshold ADC value for malignant lesion was determined using a receiver operating characteristic(ROC) curve analysis.Each lesion was classified into two major types:mass and non-mass lesion.The diagnostic performance of DWI was compared in breast mass and non-mass lesions.Results:155 malignant and 81 benign lesions were confirmed in 236 lesions. The mean ADCs of malignant lesions(1.08±0.32×10-3mm2/s) were statistically lower than that of benign lesions(1.48±0.35×10-3mm2/s) and normal tissues (1.95±0.30×10-3mm2/s).The sensitivity and specificity of the ADCs for malignant lesions with a threshold of less than 1.25×10-3mm2/s was 78.2%and 77.5% respectively.105 malignant and 56 benign lesions were included in 161 mass lesions.The mean ADCs of malignant lesions(1.04±0.3×10-3mm2/s) were statistically lower than that of benign lesions(1.47±0.33×10-3mm2/s).The sensitivity and specificity of the ADCs for malignant lesions with a threshold of less than 1.15×10-3mm2/s was 79.8%and 81.8%respectively.50 malignant and 25 benign lesions were included in 75 non-mass lesions.The mean ADCs of malignant lesions(1.18±0.34×10-3mm2/s) were statistically lower than that of benign lesions(1.51±0.4×10-3mm2/s).The sensitivity and specificity of the ADCs for malignant lesions with a threshold of less than 1.35×10-3mm2/s was 78%and 72%respectively.The means ADCs of DCIS is higher than that of IDC.In IDC, the mean ADC value of mass lesion(0.98±0.20×10-3mm2/s) is lower than that of non-mass lesion(1.09±0.25×10-3mm2/s).Conclusion:The ADCs would be an effective parameter in distinguishing between malignant and benign breast lesions.The diagnostic performance of DWI is better for mass lesion compared to non-mass lesions.The cut-off value for ADCs is different between mass and non-mass lesions.The ADCs varied with the histophathologic features.PartⅢDiagnostic strategy of Breast Lesion using combination of dynamic contrast-enhanced and diffusion-weighted imagingPurpose:To evaluate the diagnostic accuracy of a combination of dynamic contrast-enhanced MR imaging(DCE-MRI) and diffusion-weighted MR imaging (DWI) in characterization of breast lesion and to find the strongest discriminators between malignancy and benignancy.Materials and Methods:223 patients with 236 pathology-confirmed breast lesions were examined using EPI-DWI,FSE-T2WI,SE-T1WI,DCE-MR imaging were performed using VIBRANT sequence.The breast MR images were reviewed by two radioligists experienced in breast MR imaging.Based on the American College of Radiology Breaast Imaging Reporting and Date System MR imaging criteria(BI-RADS MRI),each lesion was classified into two major types:mass and non-mass lesion.MR images was analyzed include tumor shape,margin, internal enhancement characteristics,distribution,and time-signal intensity curves (TIC),maximam enhancement ratio,early enhancement ratio and so on.The ADCs of lesions were calculated on ADC maps.Univariate and multivariate analysis of MR imaging data were performed to find the strongest discriminators and the Logestic regression model was established to predict the probabilities for malignancy.The sensitivity,specificity,accuracy,positive predictive value,and negative predictive value were calculated respectively. Results:155 malignant and 81 benign lesions were confirmed in 236 lesions include 159 mass lesions and 75 non-mass lesions.Irregular and spiculated margin,heterogeneous internal enhancement,washout TIC pattern,and the ADC value＜1.15×10-3mm2/s and the early enhancement ratio＞105%were the strongest indicators of malignancy for mass lesion.Washout TIC pattern and the ADC value＜1.35×10-3mm2/s and the early enhancement ratio＞75%were the strongest indicators of malignancy for non-mass lesion.The sensitivity,specificity, accuracy,positive predictive value,and negative predictive value for mass lesion were 85.3%,84.6%,91.6%,74.6%and 85.1%respectively.The sensitivity, specificity,accuracy,positive predictive value,and negative predictive value for non-mass lesion were 82%,83.3%,91.1%,69%and 82.4%,respectively.Conclusion:The combination of DCE-MRI and DWI could produce high diagnostic accuracy in distinguishing malignant from benign breast lesions.The diagnostic strategy is different for mass and non-mass lesions.PartⅣEvaluation by diffusion-weighted imaging of tumor response to neoadjuvant chemotherapyPurpose:To evaluate diffusion-weighted imaging(DWI) in assessing tumor response to neoadjuvant chemotherapy.Materials and Methods:36 patients with confirmed malignancy were examined using DWI before and after 1st～8th cycles of neoadjuvant chemotherapy(NACT).Tumors were classified into 2 groups:responder and non-responder according to pathologic evaluations.The changes in ADCs were analyzed between responder and non-responder before and after each cycle of NACT.The contralateral normal breast tissures were also investigated as controls.Results:24 responders and 12 non-responders were included in 36 tumors. No statistical difference was found between the mean ADCs of responder(0.98±0.18×10-3mm2/s) and non-responder(0.95±0.15×10-3mm2/s) before therapy (t=0.694,P=0.411).The ADCs of responders significantly increased after each cycle of NACT.while the ADCs of non-responder and the contralateral disease-free breast tissure stayed invariable after therapy.Conclusion:ADC is more useful for predicting early tumor response to the neoadjuvant chemotherapy.
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