Which single factor listed will increase spatial resolution?

Which single factor listed will increase spatial resolution?

• A. Long SID
• B. Short SID
• C. Large focal spot
• D. High kVp

Answer: (A)

Spatial resolution improves when the distance between the X-ray source and the image receptor increases. This is because the geometric blur, or penumbra, created by the finite size of the focal spot becomes smaller on the receptor as the source-to-image distance grows. In other words, moving the source farther away reduces the projection of the focal spot onto the image, making edges crisper and details more distinct. The other factors do not increase resolution in the same way: a shorter source-to-image distance increases magnification and blur, a larger focal spot expands the penumbra and lowers sharpness, and higher kVp affects image contrast and exposure rather than edge sharpness directly.

Spatial resolution improves when the distance between the X-ray source and the image receptor increases. This is because the geometric blur, or penumbra, created by the finite size of the focal spot becomes smaller on the receptor as the source-to-image distance grows. In other words, moving the source farther away reduces the projection of the focal spot onto the image, making edges crisper and details more distinct.

The other factors do not increase resolution in the same way: a shorter source-to-image distance increases magnification and blur, a larger focal spot expands the penumbra and lowers sharpness, and higher kVp affects image contrast and exposure rather than edge sharpness directly.