Ultrasound is an imaging method that applies ultrasound technology to the medical field to achieve real-time imaging of the internal structure of the body, formerly known as B-ultrasound, but now mostly upgraded to color ultrasound. Color ultrasound is not a color image, but an ultrasound based on B ultrasound with more advanced technology, more powerful and clearer images, and the ability to apply Doppler technology to display the blood flow in the lumen of blood vessels in real time. For example, ultrasound examination of the liver is mainly to check the size, shape and texture of the liver (the technical term is the internal echo of the liver), as well as the presence of masses, the course and diameter of the blood vessels in the liver, but not the function of the liver (it is necessary to draw fasting blood for transaminases). It does not show the function of the liver (a fasting blood test such as transaminases is required to reflect liver function).