Foreshortening on a radiograph is most likely caused by which exposure error?

• A. Collimator not straight
• B. Fogged film
• C. Collimator angulation too steep
• D. Reversed film

Answer: (C)

Foreshortening happens when the X-ray beam is not perpendicular to the part or the part is not parallel to the image receptor, causing the projection of structures to appear shorter than they actually are. If the collimator is angled too steeply, the beam reaches the limb obliquely. This oblique projection compresses the length of the anatomical structure on the film, producing a foreshortened image. To avoid this, align the beam to be perpendicular to the part and keep the part parallel to the image receptor so the true length is accurately represented.

Fogged film would reduce visibility but not distort length; a reversed film would flip the image; a non-straight collimator field could crop or unevenly expose but doesn’t specifically cause foreshortening.