What happens to spatial resolution as the object-to-image distance (OID) increases?

As the object-to-image distance (OID) increases, spatial resolution decreases. This is due to the geometric principles of imaging and how they affect the clarity and detail of the image produced.

When the OID increases, the X-rays must travel a greater distance from the object being imaged to the imaging receptor. This increase in distance can lead to more scatter and less sharpness because of the divergence of the X-ray beam as it spreads out. As a result, finer details in the image can become blurred or less defined, negatively impacting the spatial resolution.

Furthermore, the increased distance amplifies the effects of any motion or positioning errors, which can contribute to a further reduction in image quality. Overall, maintaining as short an OID as practical helps to optimize the sharpness and detail within the image, thereby enhancing spatial resolution.