Which two variables affect the spatial resolution recorded in the radiographic image?

Which two variables affect the spatial resolution recorded in the radiographic image?

• A. Source-to-image distance (SID) and Object-to-image distance (OID)
• B. Focal spot size and kVp
• C. Grid ratio and exposure time
• D. Patient age and height

Answer: (A)

Spatial resolution is about how clearly fine details can be distinguished in an X-ray image, and it is governed by the geometry of the imaging setup. The distances from the X-ray source to the image receptor (SID) and from the object to the image receptor (OID) directly influence how much geometric blur ends up recorded. Increasing SID reduces blur and sharpens details, while increasing OID increases blur and reduces sharpness. Therefore, these two distances are the primary factors among the options that determine the recorded spatial resolution. The other factors affect image quality in other ways—focal spot size also matters for sharpness, but kVp mainly changes contrast; grid ratio and exposure time affect scatter and exposure, not sharpness directly; patient age or height don’t set the geometric sharpness of the image.

Spatial resolution is about how clearly fine details can be distinguished in an X-ray image, and it is governed by the geometry of the imaging setup. The distances from the X-ray source to the image receptor (SID) and from the object to the image receptor (OID) directly influence how much geometric blur ends up recorded. Increasing SID reduces blur and sharpens details, while increasing OID increases blur and reduces sharpness. Therefore, these two distances are the primary factors among the options that determine the recorded spatial resolution. The other factors affect image quality in other ways—focal spot size also matters for sharpness, but kVp mainly changes contrast; grid ratio and exposure time affect scatter and exposure, not sharpness directly; patient age or height don’t set the geometric sharpness of the image.