Breast cancer screening is an effective measure for early detection of breast cancer, and the 2013 Breast Cancer Diagnosis and Treatment Guidelines of the Chinese Anti-Cancer Society recommend screening for asymptomatic women with a view to early detection, early diagnosis and early treatment. For those who are not at high risk of breast cancer (general population), it is recommended that clinical checkups after the age of 40 be combined with an annual mammogram, and for dense breast it is recommended to combine with ultrasound examination. In addition to clinical examination, B-ultrasound and mammography, new imaging methods such as MRI can be used. Definition of high-risk group for breast cancer: 1. Those who have a clear genetic predisposition for breast cancer. 2. Patients with previous moderate to severe atypical hyperplasia or lobular carcinoma in situ in the ducts or lobules of the breast. 3. Patients with previous history of chest radiotherapy.