X-rays belong to several types of radioactive sources.

According to the degree that radiation devices may cause harm to human health and the environment, radiation devices are divided into class I, class II and class III from high to low. Medical radiation devices and non-medical radiation devices are classified according to their uses.

(1) Class I is a high-risk radiation device, which can cause serious radiation damage or even death to people exposed for a short time or have a serious impact on the environment when an accident occurs;

(2) Class II is a moderately dangerous radiation device, which can cause serious radiation damage to the exposed personnel in case of accident, and even lead to death due to large dose irradiation;

(3) Class III is a low-risk radiation device, which generally does not cause radiation damage to the exposed personnel in case of accident.

X-ray digital real-time imaging detection depends on voltage, which is greater than 160kV, and generally belongs to Class II ray devices.

At present, there are three kinds of radioactive sources used in radiotherapy: ① A, 3 and 7 rays produced by radionuclides; ②X-rays with different energies produced by X-ray therapy machines and various accelerators; (3) Electron beams, proton beams and neutron beams generated by various accelerators.