Abstract: To evaluate the application value of IVIM-DWI in differentiating different molecular subtypes of breast cancer. The clinical data of 121 patients with breast cancer who were hospitalized in our hospital from July 2016 to March 2019,and 32 patients with benign breast masses were retrospectively analyzed. All patients underwent MRI assessment and IVIM-DWI imaging. The ADC value and the IVIM-DWI multi-parameter values were obtained.The quantitative detection of ADC and IVIM-DWI multiple parameter values among different molecular subtypes of breast cancer was compared. (1) The ROC curve shows that in the identification of benign and malignant breast lumps, The area under the curve of D value is larger than ADC, D^* and f (P<0.05); The area under the curve predicted by the four indexes was significantly higher than that predicted by the four indexes alone (P<0.05).(2) The D value in the tumor tissues of the ER and PR negative groups was lower than that of the positive group, and the D^* value was higher than that of the positive group (P<0.05). The ADC value and D value in the tumor tissues of Ki67<14% group were higher than those in Ki67 ≥ 14% group, and the D^* value was lower than that in Ki67 ≥ 14% group (P<0.05); In the HER-2 positive group tumor, the f value in the tissue was higher than that in the HER-2 negative group (P<0.05); (3) There were differences in ADC value, D value, D^* value and f value between different types of breast cancer, among which the three negative breast cancer group showed lower ADC value, D value and higher f value (P<0.05). IVIM is a valuable magnetic resonance technique that can be used to identify benign and malignant breast masses and to differentiate breast cancer molecular subtypes. Understanding the characteristics of breast cancer through IVIM parameters provides a new way to accurately assess breast cancer.

Key words: intravoxel incoherent motion diffusion-weighted imaging, breast cancer, molecular subtype, differential diagnosis