What are fixed grids

The fixed grid is an anti-scatter grid that does not move relative to the X-ray beam. The more common fixed grid is the convergence grid. The lead strips of the convergence grid are arranged to focus. The convergence line should coincide with the focus of the X-ray tube during photography, so that the original emission line is parallel to the lead strip and can pass through smoothly. , And the direction of the scattered rays is random and rarely coincides with the direction of the lead strips, so most of the images obtained by the absorption of the lead strips have better clarity. If the focal point of the X-ray tube deviates from the convergence line of the fixed grid, or the fixed grid is not placed at the specified focal length, the original emission line will inevitably be lost. The percentage of the loss is proportional to the deviation and the focal length difference. It is proportional to the grid ratio, and has a direct multiple relationship with the grid ratio of the fixed grid. Therefore, the fixed grid should be placed in the required position as much as possible.

Author：Lillian