Positive beam limitation is a safety feature that ensures the size of the x-ray field is no larger than the:

• A. Source-to-image distance
• B. Detector dimensions
• C. Patient anatomy
• D. Exposure field size

Answer: (B)

Positive beam limitation automatically restricts the x-ray field to the active imaging area. The system ties the field size to the detector dimensions, so the beam cannot exceed the size of the image receptor. This helps protect the patient from unnecessary radiation and ensures the receptor is fully covered for a good image. The distance, the patient’s anatomy, or the manually set exposure field don’t set this maximum—the detector size does. So the x-ray field is no larger than the detector dimensions.