2D color ultrasound, i.e. general color ultrasound with cross-sectional imaging, has a wide range of applications and can be divided into the following areas according to different purposes of examination: 1. fetal examination: it is used to check the size of the fetus, fetal position, placental position, placental maturity, amniotic fluid volume, fetal heart, etc. It also includes screening of heart, limbs, head, abdominal organs, spine and other organs for malformations, mainly including anencephaly, brain bulge, severe open spina bifida, 2. Gynecological examination: it can check whether there are abnormal masses or cysts in the uterine adnexa, determine the amount of pelvic fluid, and also be used to observe the size, shape and internal structure of the uterus and ovaries; 3. Parenchymal organ examination: such as liver, gallbladder, spleen, pancreas and kidney, which can detect lesions according to the echo of tissue structure. In addition, 2D ultrasound can also observe the direction and function of parenchymal or cavernous organs, etc. It can also perform fine needle aspiration and contrast examination under ultrasound guidance.