In radiography, the use of a grid is recommended for body parts thicker than how many centimeters to reduce scatter radiation and improve image quality?

• A. 5 cm
• B. 2 cm
• C. 10 cm
• D. 15 cm

Answer: (D)

When a body part is thick, more x-ray photons interact and scatter within the tissues. That scattered radiation reaches the image receptor and washes out image contrast, making details harder to see. A grid sits between the patient and the receptor and absorbs much of that scatter before it can reach the image, improving contrast and image quality.

As parts reach the threshold where scatter becomes appreciable—about 15 cm in this context—the benefit of using a grid outweighs the downside of the increased exposure needed due to the grid’s presence. For thinner parts, the scatter is less significant, so the grid adds dose without a proportional improvement in image quality. This is why grids are recommended for thicknesses beyond roughly 15 cm in this approach.