Collimator leaves must be constructed of which material?

Collimator leaves must be constructed of which material?

• A. Aluminum
• B. Carbon
• C. Plastics
• D. Lead

Answer: (D)

Efficiently shaping the X-ray beam relies on a material that can block most of the primary photons with only a small thickness. Lead fits this requirement because its high atomic number and high density give it a large attenuation coefficient for diagnostic X-ray energies. That means a relatively thin lead leaf can absorb the majority of photons that would otherwise pass through, producing sharp beam edges and reducing leakage to minimize patient dose. Materials like aluminum, carbon, or plastics don’t attenuate as effectively; using them would force much thicker or heavier leaves, compromising beam geometry and image quality. So the leaves are made of lead to provide strong attenuation in a compact, workable form.

Efficiently shaping the X-ray beam relies on a material that can block most of the primary photons with only a small thickness. Lead fits this requirement because its high atomic number and high density give it a large attenuation coefficient for diagnostic X-ray energies. That means a relatively thin lead leaf can absorb the majority of photons that would otherwise pass through, producing sharp beam edges and reducing leakage to minimize patient dose. Materials like aluminum, carbon, or plastics don’t attenuate as effectively; using them would force much thicker or heavier leaves, compromising beam geometry and image quality. So the leaves are made of lead to provide strong attenuation in a compact, workable form.