What is the main purpose of a filter?

• A. Reduce High-Energy X-Rays Reaching The Patient
• B. Reduce Low-Energy X-Rays Reaching The Patient
• C. Improve The Quality Of The Radiograph
• D. Decreases The Load On The Generator

Answer: (B)

The main idea behind a filter is to harden the X-ray beam by removing the lowest energy photons before they reach the patient. Those low-energy photons are mostly absorbed in the superficial tissues and contribute to patient dose without significantly improving image formation. By filtering them out, the beam becomes more penetrating, so you can achieve the same image receptor exposure with less patient dose, and image quality is improved because the remaining photons carry more useful information. High-energy photons aren’t being targeted for removal, so the filter doesn’t aim to reduce high-energy radiation; it also doesn’t directly reduce the generator’s load—the exposure settings may be adjusted to compensate, but the primary purpose is reducing dose by removing low-energy X-rays.