Which statement about the air gap technique is true?

• A. Works Because X-Rays Are Absorbed In The Air Between The Patient And The IR
• B. Should Occur When Possible
• C. May Cause Some Magnification Because Of Decreased OID
• D. Works Because Scatter Radiation Travels In Divergent Paths And Misses The IR Due To Increased OID

Answer: (D)

The air gap technique relies on geometry to reduce scatter, not on absorbing photons in air. By increasing the distance between the patient and the image receptor, scatter photons produced inside the patient travel in many directions, and more of them miss the detector because of the larger object-to-image distance. This divergence means less scatter reaches the IR, improving image contrast. Keep in mind that increasing this distance also causes magnification, which is a trade-off of the technique. The idea that it works because X-rays are absorbed in air is incorrect since air absorption is minimal. The statement about decreasing OID causing magnification is also off, since magnification increases with increased OID, which is exactly what the air gap uses.