Objective    To study the correlation of CT perfusion imaging (CTPI) of induced rat breast cancer with tumor pathological grade and microvascular density (MVD)，and the diagnostic value of CTPI for breast cancer.      Methods    Breast cancer was induced in 35 Wister male rats with intragastric 7，12-dimethyl-1，2-benzanthracene (DMBA) treatment. Routine breast CT scanning and CTPI were performed. After processed at a workstation

CTPI parameters were obtained including blood flow (BF)，blood volume (BV)，mean transit time (MTT)，permeability surface (PS)，and time density curve (TDC). The rats were sacrificed and breast tumor tisue samples were collected. Breast tumor tisue samples were stained with HE and factor Ⅷ-related antigen immunohistochemistry to observe the pathological type and MVD of tumor.     Results    Breast tumor was successfully induced in 30 rats (including 8 with breast hyperplasia and 22 with breast cancer). The BF and BV were higher in rats with breast cancer than in those with breast hyperplasia [151.72±93.43 vs 42.96±32.42 ml/(min·100 g)

9.55±7.88 vs 2.17±1.36 ml/100 g

P0.05] . The BF and BV were lower in patients with moderatelelydifferentiated breast cancer than in those with poorlydifferentiated breast cancer [115.30±15.46 vs 256.52±132.19 ml/（min·100 g）

9.76±9.00  vs 10.34±4.56 ml/（min·100 g）

P0.05] . The MTT was significantly shorter in rats with breast cancer than in those with breast hyperplasia (P0.05)

but showed no significant difference in tumor differentiation (P0.05). The positive correlation of MVD with BF

BV and PS was increased with the decreased tumor differentiation with a correlation coefficient of 0.701

0.441 and 0.521

respectively (P0.05).     Conclusion    Induced breast cancer in rats is a suitable model for CT perfusion study. CTPI can help to distinguish between benign and malignant breast diseases and show tumor differentiation，and is closely associated with MVD of tumor.