Which grid type should not be used when tube angulation is required?

The correct answer indicates that a crossed grid should not be used when tube angulation is required. A crossed grid, also known as a rhombic or cross-hatch grid, consists of two sets of lead strips that intersect at right angles. This design was created to maximize the degree of scatter radiation that the grid can absorb. However, because the lead strips are oriented in both the vertical and horizontal directions, any angulation of the X-ray tube can lead to significant grid cut-off. This means that the X-ray photons will not be accurately filtered through the grid due to its configuration, resulting in unacceptable imaging quality.

In contrast, focused grids and linear grids are designed to work effectively even with some tube angulation. Focused grids are constructed with lead strips that converge to a specific point at the distance they are designed to be used, making them suitable for tube angulation at that particular focus distance. Linear grids, on the other hand, consist of parallel lead strips aligned in one direction, allowing for greater flexibility with angulation since there is minimal grid cut-off if the tube is angled along the same direction as the strips.

Therefore, when considering the impact of tube angulation on image quality, the crossed grid is not suitable, which justifies