What is the amount of x-rays in photography?

Unit: horse s? Example: The amount of X-rays required for one shot is 20mA, and 400mA×0.05s can be selected.

Reflect the mass (penetration) and photon energy of X-rays. With the increase of tube voltage, the sensitivity of the detector increases and the image levels are rich. With the increase of noise, the contrast between different tissue structures decreases; When the scattered line content increases, the fog feeling of the photo increases (it can be eliminated by filter grid or cross grid with high grid ratio); The corresponding required tube current (tube current and exposure time) decreases, the motion blur decreases and the radiation dose decreases; Masking is reduced and small focus exposure can be used to improve image clarity.

The adjustment of tube voltage mainly depends on the thickness of the car body, and there is a variable tube voltage method (for every increase or decrease of thickness 1cm, the tube voltage increases or decreases by 2KV, and the thickness deviation is too large, so the tube voltage needs to increase or decrease by 3 ~ 4 kV); Fixed tube voltage method (generally, the tube voltage is higher than 10 ~ 20kV, but the mAs is doubled, which improves the image level but also increases the scattering line).

Reflects the number of x-rays. The greater the tube current, the greater the sensitivity, the smaller the quantum dot and the greater the X-ray dose.

At present, most DRs have AEC (Automatic Exposure Control) device, and the detector will automatically change the exposure parameters (tube voltage is fixed and tube current changes) according to the detection of X-ray dose value during pre-exposure to obtain relatively stable image quality.

The main purpose of the grid is to reduce scattered rays reaching the detector. Use when the body thickness is ≥ 15cm or the tube voltage is ≥60. Most of them are movable (can eliminate lead shadow).

Three parameters: the gate ratio-generally110 of the tube voltage; Grating focal length-the distance from the grating plane to the focal point, which can give the adjustment range of SID; Grid density —— the number of lead bars in the range of1cm.

The larger the irradiation field, the thicker the body thickness and the more scattering lines. It is best to reduce the irradiation field to the minimum including the irradiated part (special patients need flexibility); Generally, the irradiation field is smaller than the size of the detector, so that its periphery does not accept X-rays, and the photo quality is improved.