DR examination, i.e. X-ray digital photography examination, the main difference between DR examination and CT examination lies in the different imaging characteristics, different number of pictures displayed, different radiation dose, and so on. 1.DR is to replace the traditional X-ray film with a flat detector as the carrier of X-ray information through the human body, applying subtraction technology to pixelate and digitize the X-ray information through the human body, and ultimately converted to analog X-ray images by the computer system. The CT image is a tomographic image, which overcomes the shortcomings of overlapping images of various tissue structures in ordinary X-ray examination, so that the tissue structures of various organs can be clearly displayed, with higher density resolution and hierarchy, significantly improving the detection rate of lesions. 2. The number of pictures displayed is different: the image displayed by DR is a slice, while the image displayed by CT is a multi-layer image. 3. The radiation dose is different: the radiation dose of DR and CT is also different, the radiation dose of DR is low and the radiation dose of CT is high. In addition, patients can be selected by the doctor according to different needs of the corresponding examination methods.