Which factor directly affects geometric magnification in x-ray imaging?

Which factor directly affects geometric magnification in x-ray imaging?

• A. Focal spot size
• B. Exposure time
• C. Source-to-image distance
• D. mA

Answer: (C)

Geometric magnification comes from the setup geometry: how far the object is from the image receptor compared to how far the x-ray source is from the receptor. The magnification factor is determined by the ratio of the source-to-image distance (SID) to the source-to-object distance (SOD), M = SID / SOD. Increasing SID makes rays diverge more before hitting the detector, enlarging the projected image on the receptor. Exposing time and mA control how much radiation and image brightness you get, not the image size, while focal spot size mainly affects sharpness rather than magnification.

Geometric magnification comes from the setup geometry: how far the object is from the image receptor compared to how far the x-ray source is from the receptor. The magnification factor is determined by the ratio of the source-to-image distance (SID) to the source-to-object distance (SOD), M = SID / SOD. Increasing SID makes rays diverge more before hitting the detector, enlarging the projected image on the receptor. Exposing time and mA control how much radiation and image brightness you get, not the image size, while focal spot size mainly affects sharpness rather than magnification.