What impact does a longer SID have on patient exposure?

A longer source-to-image distance (SID) results in decreased patient exposure. This phenomenon occurs due to the inverse square law, which states that the intensity of radiation (and therefore the exposure to the patient) is inversely proportional to the square of the distance from the radiation source. As the SID increases, the X-ray beam spreads over a larger area, which effectively reduces the intensity of the radiation that reaches the patient.

Therefore, with a longer SID, there will be less radiation exposure to the patient's tissues, making it a critical consideration for optimizing patient safety during imaging procedures. This aspect of radiation physics is essential in radiographic practice, as it helps in balancing the need for diagnostic quality images with minimizing patient dose.