Increasing which factor related to distance will increase spatial resolution?

Increasing which factor related to distance will increase spatial resolution?

• A. Source-to-object distance (SOD)
• B. Source-to-image distance (SID)
• C. Object-to-detector distance
• D. Table-to-detector distance

Answer: (A)

Spatial resolution is limited by geometric blur from the finite size of the X‑ray focal spot. The amount of blur that appears on the image depends on the projection geometry: how far the object sits from the source and how far the image plane sits from the source. If you increase the distance from the X-ray source to the object, you move the object farther away from the focal spot. This reduces the angular spread of rays that reach the detector from different parts of the focal spot, so the projected blur on the image decreases and edges become crisper. In other words, the geometric unsharpness gets reduced when the source–object distance is larger, which improves spatial resolution. The other options tend to increase blur or not reduce it as effectively. Increasing the distance from the object to the detector (or table to detector distance) raises the object–detector distance, which increases geometric blur. Adjusting the overall source–image distance without changing the relationship that keeps blur low has less direct benefit for sharpness. So the distance you want to increase to sharpen the image is the distance from the source to the object.

Spatial resolution is limited by geometric blur from the finite size of the X‑ray focal spot. The amount of blur that appears on the image depends on the projection geometry: how far the object sits from the source and how far the image plane sits from the source. If you increase the distance from the X-ray source to the object, you move the object farther away from the focal spot. This reduces the angular spread of rays that reach the detector from different parts of the focal spot, so the projected blur on the image decreases and edges become crisper. In other words, the geometric unsharpness gets reduced when the source–object distance is larger, which improves spatial resolution.

The other options tend to increase blur or not reduce it as effectively. Increasing the distance from the object to the detector (or table to detector distance) raises the object–detector distance, which increases geometric blur. Adjusting the overall source–image distance without changing the relationship that keeps blur low has less direct benefit for sharpness. So the distance you want to increase to sharpen the image is the distance from the source to the object.