A decrease in the source-to-image distance (SID) will result in which two outcomes?

A decrease in the source-to-image distance (SID) primarily leads to decreased spatial resolution and increased penumbra. When the SID is reduced, the x-ray beam diverges more as it travels from the source to the image receptor, which compromises image sharpness. This phenomenon results in spatial resolution suffering because the detail in structures becomes less distinct.

Additionally, a shorter SID can increase the penumbra, which refers to the blurred edges around an image due to the geometric unsharpness of the x-ray beam. This increase in penumbra also affects the definition of the image and contributes to the overall degradation of spatial resolution.

The stability of contrast doesn't particularly relate to changes in SID, and it generally remains constant unless other factors, like patient thickness or exposure conditions, are altered. Increased spatial resolution is typically associated with a larger SID due to reduced penumbra and improved beam collimation. Therefore, the outcomes of decreased SID are accurately described by decreased spatial resolution and increased penumbra.