Distance between flat panel detector and grid

When we use X-ray machines to take pictures of patients, the distance between the flat-panel detector and the grid should be as small as possible. Under what circumstances can a flat-panel detector with a wire grid improve the quality of filming? The role of the wire grid is to filter scattered rays, reduce fog and improve contrast.
In the case where the thickness and density of the object being photographed is relatively large, the use of a grid can improve the quality of the film.
It is recommended to use a grid for filming with a high-frequency machine, and the effect will be better.

Author：Lillian