What is a grid made of?

• A. Lead plates with air gaps
• B. A single sheet of metal
• C. Strips of plastic with no lead
• D. Strips of lead separated by strips of plastic

Answer: (D)

In radiography, a grid is used to improve image contrast by reducing scattered X-rays that fog the image. It does this with alternating lead strips, which absorb scatter, and radiolucent interspace material that lets the primary beam pass through with minimal attenuation. The best description is strips of lead separated by strips of plastic, because this arrangement provides the necessary contrast enhancement while allowing the useful X-rays to reach the detector. The other ideas don’t fit: a grid isn’t just a single metal sheet, and using plastic without any lead wouldn’t block scatter; and lead plates with air gaps describe a different, non-grid construction.