Matters needing attention when using the grid

1. Tube voltage compensation

Since the main component material of the wire grid is lead foil, it not only blocks the scattered rays, but also inevitably blocks a part of the original emission line, which reduces the sensitivity of the film, so it should be appropriate to use the wire grid when photographing. Increase the exposure conditions, that is, increase the X-ray penetration ability by increasing the tube voltage to achieve the purpose of compensation. Specific compensation data should be obtained in conjunction with clinical use. Under normal circumstances, the low grid ratio grid is suitable for low KV tube voltage, and the high grid ratio is suitable for high KV tube voltage.

2. The influence of focus deviation and focal length mismatch

The lead bars of the converging grid are arranged in the focal direction. The converging line should be coincident with the focal point of the X-ray tube during photography, so that the original emission line is parallel to the lead bar and can pass through smoothly, while the direction of the scattering line is random. It is in the same direction as the lead strip, so most of it is absorbed by the lead strip, and the obtained image has better clarity. If the focus of the X-ray tube and the filter grid deviate from the convergence, or the filter grid is not placed at the specified focal length, the loss of the original emission line will inevitably occur. The percentage of the loss is proportional to the amount of deviation and the focal length difference. At the same time, it has a direct multiple relationship with the grid ratio of the grid. So it should be possible to place the grid in the required position. However, in actual clinical use, some deviations are inevitable, so there is a regulation for the deviation of the boss wire grid.

Center deviation should be avoided as much as possible. In the case of static grids, there should be no deviation: when using movable grids, center deviation will inevitably occur, but the deviation should be designed to be as small as possible.

In some occasions, the distance from the focal point to the cassette needs to be changed

Author：X Ray Grids Maker