In diagnostic radiography, adding aluminum filtration to the X-ray beam primarily serves to:

• A Increase the overall intensity of the beam
• B Harden the beam by removing low-energy photons, thereby reducing patient skin dose ✓
• C Improve spatial resolution by narrowing the focal spot
• D Increase image contrast by enhancing photoelectric absorption

Explanation

Added filtration (typically aluminum) absorbs low-energy photons that would otherwise be absorbed superficially in the patient without contributing to image formation. This 'hardens' the beam (increases average energy), reducing skin dose while maintaining useful beam intensity. It does not increase overall intensity, alter focal spot size, or directly enhance contrast. Total filtration must meet regulatory minimums (e.g., 2.5 mm Al equivalent for tubes >70 kVp).

Reference: Bushberg, The Essential Physics of Medical Imaging, 3rd ed.

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Written and medically reviewed by the StethoPrep medical team.