Why should the small focal spot be used as much as possible?

Using a small focal spot is important primarily because it provides greater detail in the imaging process. The small focal spot reduces the size of the area from which the x-rays are emitted, which minimizes the penumbra effect, or the less-defined edges of an image. This improved sharpness and resolution allow for finer details in the structures being imaged, making it easier to distinguish between adjacent tissues or abnormalities.

While there are benefits associated with using a small focal spot, such as potentially influencing image contrast or exposure time, these do not directly address the primary advantage of detail enhancement that the small focal spot uniquely offers. Greater detail can significantly improve diagnostic accuracy, which is a critical aspect of radiographic imaging.