Which term describes image size distortion in radiography?

• A. Geometric distortion
• B. Noise
• C. Magnification
• D. Contrast

Answer: (C)

Image size distortion in radiography is magnification. This happens because the geometry of the setup—the distance from the X-ray source to the object (SOD) and from the source to the image receptor (SID)—affects how large the object appears on the film or detector. When the object sits farther from the receptor (smaller SOD) or closer to the tube, the projected image grows larger, creating magnification. The magnification factor is roughly SID divided by SOD, so increasing SID or decreasing SOD reduces magnification and yields a truer-sized image. Geometric distortion is the broader category that includes magnification plus other size/shape distortions from misalignment, while noise and contrast refer to different image quality aspects. Magnification specifically explains the size change observed.