What effect does increased collimation have on an elbow?

What effect does increased collimation have on an elbow?

• A. Increases exposure
• B. Has no effect
• C. Increases scatter
• D. Decreases the patient’s exposure to primary radiation

Answer: (D)

Limiting the x-ray field around the elbow reduces how much tissue is irradiated. When you increase collimation, the beam is focused tightly on the elbow, so a smaller volume of tissue is exposed to primary radiation. That means fewer photons interact with the patient’s tissues, resulting in lower entrance skin dose and less scattered radiation overall. In short, tighter collimation lowers the patient’s exposure to primary radiation while still allowing a diagnostic image of the elbow; exposure factors can be adjusted as needed to maintain image quality, but the dose-saving effect comes from irradiating less tissue.

Limiting the x-ray field around the elbow reduces how much tissue is irradiated. When you increase collimation, the beam is focused tightly on the elbow, so a smaller volume of tissue is exposed to primary radiation. That means fewer photons interact with the patient’s tissues, resulting in lower entrance skin dose and less scattered radiation overall. In short, tighter collimation lowers the patient’s exposure to primary radiation while still allowing a diagnostic image of the elbow; exposure factors can be adjusted as needed to maintain image quality, but the dose-saving effect comes from irradiating less tissue.