When the source-to-image distance (SID) is altered, which two aspects are affected?

When the source-to-image distance (SID) is altered, size distortion and image receptor exposure are the two aspects that are impacted.

Changing the SID directly affects the amount of radiation that reaches the image receptor. A greater SID will result in less radiation hitting the receptor, thereby affecting image receptor exposure. Conversely, a shorter SID increases exposure due to radiation impacting the receptor more directly, potentially resulting in an overexposed image.

Size distortion is also influenced by SID. When the SID is increased, the object being imaged will appear closer to its actual size because the x-ray beam divergence is reduced. In contrast, decreasing the SID can create a larger-than-actual size appearance of the object being imaged due to increased beam divergence, resulting in size distortion.

Understanding the relationship between SID and these two factors is essential for producing high-quality diagnostic images while minimizing distortion and ensuring appropriate exposure levels.