According to China Education Network, the X-ray quantity is perpendicular to the unit area of X-ray beam, and the number of photons passing through per unit time is called X-ray quantity. In X-ray diagnosis, the amount of X-rays is expressed in milliamperes (mAs). X-ray machine is the equipment that produces X-rays, which is mainly composed of X-ray tube, X-ray machine power supply and control circuit.