Which of the following grid types uses a specific source-to-image distance (SID) range?

The focused grid uses a specific source-to-image distance (SID) range due to its design, which incorporates angled lead strips that converge at a particular point. This design enhances the grid's effectiveness in reducing scattered radiation at that specified distance, thereby improving image quality by increasing contrast. The SID range is vital; if the x-ray tube is positioned outside this range, the grid may not perform optimally, leading to potential image degradation and increased artifacts.

In contrast, parallel grids maintain lead strips that are straight and parallel to each other, which makes them more forgiving regarding distance but not as effective as focused grids in minimizing scatter. Crossed grids also have a specific SID, but their design is less frequently used due to their limitations, such as higher sensitivity to misalignment and a more complex setup. Virtual grids are a newer technology used digitally but do not have physical structures that rely on specific SID ranges like the focused grid does.