Which of the following does not affect spatial resolution in imaging?

Spatial resolution in imaging refers to the ability to differentiate between closely spaced objects and is influenced by several factors in the imaging process. The correct choice indicates that grid ratio does not impact spatial resolution.

Grid ratio pertains to the relationship between the height of the lead strips in a grid and the distance between them, primarily serving to improve image contrast by reducing the amount of scatter radiation that reaches the film or detector. While grids enhance overall image quality, their primary function is not to affect spatial resolution but rather to control scatter.

In contrast, film grain size, detector element size, and source-to-image distance directly relate to the spatial resolution. Film grain size determines the level of detail the film can record; smaller grain sizes allow for greater resolution due to finer detail capture. Detector element size influences how well the system can resolve different spatial frequencies; smaller elements yield better resolution by capturing finer details. Lastly, source-to-image distance affects geometric unsharpness; increased distance generally leads to sharper images due to reduced penumbra effects.

Thus, the grid ratio stands out as being unrelated to the spatial resolution, while the other factors directly contribute to the precision and clarity of the resulting images.