The biggest difference between CBCT and somatic CT (spiral CT) is that the projection data of somatic CT is one-dimensional, and the reconstructed image data is two-dimensional, and the reconstructed three-dimensional image is stacked up with consecutive two-dimensional slices, and its image metal artifacts are heavier. In contrast, the projection data of CBCT is two-dimensional, and the reconstructed three-dimensional image is obtained directly. From their imaging structure, CBCT uses three-dimensional cone-beam X-ray scanning to replace the two-dimensional fan-beam scanning of body CT; correspondingly, CBCT adopts a two-dimensional faceted detector to replace the line detector of body CT. Obviously, CBCT using cone-beam X-ray scanning can significantly improve the utilization of X-rays, only need to rotate 360 degrees to obtain all the raw data required for reconstruction, and the use of a surface detector to acquire projection data can accelerate the data acquisition speed; CBCT has another advantage is a very high isotropic spatial resolution.