Which option would most directly increase spatial resolution?

Which option would most directly increase spatial resolution?

• A. Increase SID
• B. Increase OID
• C. Increase focal spot size
• D. Decrease focal spot size

Answer: (D)

Spatial resolution improves most directly when the focal spot size is reduced because the finite size of the focal spot creates geometric unsharpness (penumbra) on the image receptor. A smaller focal spot shrinks this blur, so edges between structures appear crisper and the image can resolve finer details. Increasing the source-to-image distance helps reduce blur too, but its effect is indirect and comes with trade-offs like lower image brightness. Increasing the object-to-image distance worsens blur by enlarging penumbra, so it degrades resolution. Increasing the focal spot size increases blur, directly reducing sharpness. Therefore, the change that most directly increases spatial resolution is decreasing the focal spot size.

Spatial resolution improves most directly when the focal spot size is reduced because the finite size of the focal spot creates geometric unsharpness (penumbra) on the image receptor. A smaller focal spot shrinks this blur, so edges between structures appear crisper and the image can resolve finer details.

Increasing the source-to-image distance helps reduce blur too, but its effect is indirect and comes with trade-offs like lower image brightness. Increasing the object-to-image distance worsens blur by enlarging penumbra, so it degrades resolution. Increasing the focal spot size increases blur, directly reducing sharpness. Therefore, the change that most directly increases spatial resolution is decreasing the focal spot size.