Value of Diffusion-weighted Imaging with Different b Values in the Diagnosis of Breast Lesions at 3.0T MRI

Purpose:To evaluate the value of diffusion-weighted imaging with different b values in the diagnosis of breast lesions at 3.0T MRI.Methods: Twenty normal controls and 34 patients with 20 benign breast lesions and 16 malignant ones underwent diffusion-weighted imaging at 3.0T MRI with different b values of 0,750,1000 and 1250s/mm2.The other conventional sequences(T2WI and T1WI dynamic contrast-enhanced MRI)were performed at 3.0T or 1.5T MRI.Image quality score,contrast-to-noise ratio(CNR) and apparent diffusion coefficient(ADC) of normal breast,benign lesions and malignant ones with the same b value and different b values were compared and analyzed.Sensitivity,specificity and accuracy for the diagnosis of breast cancer with different b values were calculated respectively,as well as the ROC curves.Results:(1) The difference of the image quality score among the different b values was not statistically significant(F=3.02,P=0.05160.05).(2) The difference of CNR of the breast lesion among the different b values was statistically significant(F=10.69,P=0.00010.01).Higher CNR was obtained when b value was 750s/mm2 than those when b value was 1000s/mm2 and 1250s/mm2,and the differences were statistically significant(P values were 0.004 and 0.000),but the difference of CNR between the b value of 1000s/mm2 and 1250s/mm2 was not statistically significant(P=0.8000.05).(3) Average ADC value of normal breast was higher than benign lesion,while that of benign lesion was higher than that of malignant ones at the same b value.Among them the differences were statistically significant(P values were all 0.000).(4) The cutoff ADC value was 1.33×10-3mm2,1.25×10-3mm2/s,and 1.16×10-3mm2/s when b value was 0,750s/mm2,0,1000 and 0,1250s/mm2.Sensitivity,specificity and accuracy for diagnosis of breast cancer was 81.25%,87.5%,85.71%;81.25%,77.5%,78.57% and 81.25%,82.5%,82.14% respectively.And the area under ROC curve(AUC) was 0.8781,0.8672 and 0.8828 respectively.The difference among them was not statistically significant(P0.05).Conclusion:(1) Better image quality and CNR score were obtained when b value was 750s/mm2 than those when b value was 1000s/mm2 and 1250s/mm2 at 3.0T.(2) Diagnosis of breast lesions with diffusion-weighted imaging must be made in combination with ADC value.(3) Accuracy in the detection of breast cancer at 3.0T was high with all b values.However we believe the best b value was 0,750s/mm2 because of its highest image quality and CNR.