Radiologic Technologist Practice Exam

What factors affect the spatial resolution of an image?

1. mAs and object-to-image distance (OID)

2. Source-to-image distance (SID) and focal spot size

3. kVp and mAs

4. Tube angle and kVp

The correct answer is: Source-to-image distance (SID) and focal spot size

Spatial resolution in radiographic imaging refers to the ability to visualize fine details within an image. Several factors can influence this critical aspect, enhancing or diminishing the clarity and quality of the captured image. The correct choice highlights two important factors: source-to-image distance (SID) and focal spot size. Increasing the SID improves spatial resolution because it reduces the effect of magnification and geometric unsharpness. When the distance between the x-ray tube and the image receptor (such as a film or digital detector) is greater, the x-rays diverge less as they travel, resulting in sharper images. This is crucial in radiography, as it allows for clearer delineation of anatomical structures, thereby improving diagnostic capability. Focal spot size also plays a critical role; a smaller focal spot size produces less blur and enhances resolution because it limits the amount of divergence of the x-ray beam at the point of origin. A small focal spot can provide improved image detail, especially for high-resolution imaging applications, because it reduces the inherent geometric blur associated with larger focal spots. So, the combination of manipulating the SID and optimizing focal spot size is fundamental in achieving superior spatial resolution, making this choice the appropriate answer to the question. Other factors listed in the other choices contribute to