Positive beam limitation is also known as:

• A. Use of collimators
• B. Beam limitation used for all exams
• C. Use of beam restrictors
• D. Automatic collimation

Answer: (D)

Positive beam limitation is the automatic sizing of the x-ray field to the size of the image receptor or the selected IR. This automatic adjustment is achieved by the collimation system and sensors, so the beam is limited to cover only the area being imaged. That’s why it’s best described as automatic collimation. The other terms describe collimation in a more general or hardware-oriented sense (like simply using collimators or beam restrictors) and don’t capture the automatic, self-adjusting aspect that PBL refers to.