To decrease receptor exposure in a portable chest radiograph when the technique is limited, which action is most appropriate?

• A. Decrease SID
• B. Increase filtration
• C. Increase SID
• D. Increase grid ratio

Answer: (C)

Increasing the source-to-image distance is the most effective way to lower receptor exposure when you’re limited by technique. The x-ray beam intensity drops with distance according to the inverse square law, so a larger SID means fewer photons reach the image receptor, reducing exposure (and patient dose) without needing to change mA or exposure time.

Decreasing the distance would do the opposite and raise receptor exposure. Increasing filtration can reduce receptor exposure too by removing low-energy photons, but it’s less predictable in the portable setting and can impact image quality. Increasing grid ratio would attenuate more of the primary beam and is not a practical adjustment during a portable exam, and it can necessitate a higher exposure to maintain density.