Spatial resolution is directly related to which of the following factors?

Spatial resolution refers to the ability to accurately distinguish small features and details within an image. It is primarily influenced by several factors, one of which is the focal spot size. A smaller focal spot size leads to better spatial resolution because it minimizes the blurring of images and allows for finer detail to be captured. Thus, the focal spot size is crucial because it directly impacts the sharpness of the image.

Source-image distance (SID) also plays a significant role in spatial resolution. A longer SID tends to reduce image blur and enhance resolution, as it decreases the effect of geometric unsharpness. When the X-ray source is further away from the image receptor, the rays converge more towards the focal spot and project a sharper image.

While tube current can impact the overall image quality, including factors like noise and exposure, it does not have a direct relationship with spatial resolution in the same way that focal spot size and SID do.

Therefore, the correct choice illustrates that spatial resolution is notably tied to both the focal spot size and the source-image distance. Hence, it would be more accurate to reflect that both those factors are significant contributors to spatial resolution, alongside the influence of tube current in a more indirect manner.