The noise caused by the change of X-ray quantity in cr system is as follows

The noise caused by the change of X-ray quantity in cr system is quantum noise.

CR is computer X-ray photography, which takes laser as the carrier and imaging plate (IP) which can record and read X-ray imaging information as the carrier. After X-ray exposure, scanning reading and digital processing, images with digital information are formed.

Imaging principle: After X-ray irradiates IP, X-ray quantum is absorbed by fluorescent particles in IP imaging layer, releasing electrons, and some of them are scattered in the imaging layer in a semi-stable state, forming a latent image. This is mainly the collection of information. When the scanner irradiates the latent image formed by laser, the semi-stable electrons are transformed into light quantum, and the phenomenon of photoluminescence (PSL) occurs.

Optical quantum is detected by photomultiplier tube and converted into analog electrical signal, which is converted into digital signal after A/D conversion. This part is mainly about reading information. Finally, the computer acquires and stores the image for further processing, and processes and records the information.

The quality of medical images depends on the imaging method, equipment characteristics, parameters selected by the operator and the cooperation of patients. Image quality is comprehensively reflected by contrast, blur, noise, artifacts, distortion and other factors.

Clinically, it is often necessary to consider the relationship between an organization and its surrounding organizations. In fact, the visibility of most imaging methods to a certain tissue and organ depends on this relationship rather than the overall characteristics of the whole image. The task of each imaging system is to transform specific tissue features into gray gradient and color of the image. If medical radiology technology has enough contrast, these tissues and organs will become visible.

Classification of CR system noise;

Intrinsic noise: noise unrelated to X-rays generated during the operation of CR system. Including: the structural noise of IP: playing a leading role; Laser noise; Circuit system noise; Quantum noise of analog-to-digital conversion. Quantum noise: including X-ray quantum noise and optical quantum noise.