American Registry of Radiologic Technologists (ARRT) Practice Exam

Selecting the appropriate Source-to-Image Distance (SID) is crucial primarily for managing radiation dosage. The SID plays a significant role in determining the intensity of the X-rays that reach the patient and ultimately the detector or film. As the distance between the X-ray source and the image receptor increases, the radiation intensity diminishes due to the inverse square law, which states that radiation intensity is inversely proportional to the square of the distance from the source. Therefore, increasing the SID reduces the radiation dose to the patient while still achieving the desired image quality.

Additionally, while SID can influence factors like image resolution and exposure time, its most immediate and critical impact relates to controlling how much radiation the patient receives during the exposure. That’s why choosing the correct SID is integral in ensuring both safety and effectiveness in radiologic procedures.