What is the primary purpose of diagnostic filtration in radiography?

• A. Increase image contrast
• B. Increase receptor exposure
• C. Decrease patient dose
• D. Decrease occupational dose

Answer: (C)

Diagnostic filtration removes low-energy photons from the X-ray beam before it reaches the patient. These soft photons are readily absorbed by superficial tissues and add to patient dose without meaningfully contributing to image formation. By filtering them out, the beam becomes more penetrating (hardened), so the same image quality can be achieved with less patient exposure, or you can maintain image quality with a lower dose. That’s why the primary purpose is to decrease patient dose. Any changes to image contrast or receptor exposure come as a consequence of the beam hardening, and while there may be indirect effects on occupational dose from reduced scatter, reducing patient dose is the main goal.