What is the principle of X-ray imaging?

The basic principle of X-ray imaging, on the one hand, is based on X-ray penetration, fluorescence effect and photosensitive effect; On the other hand, it is based on the difference in density and thickness between human tissues. When X-rays pass through different tissues and structures of human body, the absorption degree is different, so the amount of X-rays reaching the screen or film is also different. In this way, images with different light and dark or black and white contrast are formed on the screen or X-ray film.

1895, German physicist Roentgen applied tens of thousands of volts to the electrodes at both ends of a vacuum glass tube embedded with two metal electrodes (cathode and anode), and found that a piece of cardboard impregnated with barium platinum cyanide solution gave off bright fluorescence at a distance of two meters from the glass tube. When I reached for this cardboard with my hand, I saw the image of the upper hand bone on the cardboard. At that time, Roentgen decided that it was a kind of invisible ray, but it could penetrate the object. Because its principle and nature could not be explained at that time, it borrowed the unknown "X" in mathematics as the code name and called it X-ray.

The formation of extended data X-ray images is based on the following three basic conditions:

First of all, X-rays have a certain penetrating power, which can penetrate human tissues and structures.

Secondly, there are differences in density and thickness of the penetrated tissue structure, and the amount of X-rays absorbed during penetration is different, so the amount of remaining X-rays is also different;

Third, this differential residual X-ray is invisible. Through the imaging process, such as X-ray film, screen or TV screen display, X-ray images with black-and-white contrast and hierarchical differences can be obtained.

X-ray is essentially an electromagnetic wave, which has the same properties as electromagnetic wave. In addition, it has unique properties in physics, chemistry and biology. I. Physical characteristics:

1 and X-rays are invisible electromagnetic waves propagating in a uniform isotropic medium. X-ray has no charge, so it is not affected by external magnetic field or electric field.

3. Penetration: X-ray has high wavelength energy and weak material absorption, so it has strong penetration ability.

4. Fluorescence: Some substances can stimulate visible fluorescence after being irradiated by X-rays.

5. Ionization: X-ray photons with enough energy can hit orbital electrons in atoms, causing them to ionize once. The knocked electrons still have enough energy to ionize more atoms.

References:

Baidu encyclopedia-the basic principle of x-ray imaging