Objective To explore the relationship between the menstrual cycle and apparent diffusion coefficient(ADC)values of MR diffusion weighted imaging(DWI). To investigate the evaluation of DWI and dynamic contrast-enhanced MRI(DCE-MRI)in distinguishing benign from malignant breast lesions.

Methods Thirty-four healthy, premenopausal female volunteers who had regular menstrual cycles and 96 breast disease patients who proved by surgery or Needle aspiration pathology were included in the study. Of the 96 patients, there were 36 cases with 44 benign breast lesions and 60 cases with 70 malignant breast lesions. The healthy volunteers were scanned by conventional T1 weighted MRI, T2 weighted MRI and DWI once a week for 4 weeks with Siemens Sonata 1.5T MRI(b=1000s/mm²). The patients were examined by conventional MRI, DCE-MRI and DWI. DWI using Echo planar imaging technique and frequency selection suppression technology were used in DWI(b=1000 s/mm² )and fast low angle shot sequence was used in DCE-MRI. The data of DWI and DCE-MRI were sent to Leonardo workstation.

Results ① ADC values of normal breast in the second week of the menstrual cycle reduced to minimum and then slowly increased, a comparison between the mean was not significant(F=1.029, P > 0.05). ② In DCE-MRI, type III curve is the typical type of breast cancer, type I and IV curve are the typical type of breast benign lesions. ③When b=1000 s/mm², the diagnostic threshold of ADC values between the benign breast lesions and malignant lesions was 1.25×10^-3 mm²/s.

Conclusions ADC values were less influenced by the menstrual cycle in normal breasts. The specificity and accuracy in the diagnosis of benign and maglinant breast lesions were improved with the combination of DCE-MRI and DWI.