Increasing OID generally results in

• A. Improved spatial resolution
• B. Unchanged spatial resolution
• C. Decreased spatial resolution
• D. Increased patient dose

Answer: (C)

Increasing the distance from the object to the image receptor makes the image blurrier and less sharp. When the object sits farther away, the projection of the focal spot onto the receptor becomes more spread out, increasing geometric unsharpness. This is captured by the idea that geometric blur grows with the object-to-image distance, and magnification also increases as OID grows, both contributing to reduced spatial resolution.

In practice, keeping receptor exposure consistent might require higher exposure factors because the X-ray beam has to travel a longer path, which can raise patient dose. But the direct, most consistent effect of increasing OID is worse spatial resolution, not an improvement.