What is the primary function of the collimator in radiography?

• A. Collimator narrows and filters the X-ray beam so that only parallel rays reach the patient.
• B. It converts X-rays to visible light.
• C. It rotates the patient table.
• D. It measures exposure time.

Answer: (A)

The collimator shapes and limits the X-ray beam to the area of clinical interest. By narrowing the beam, it reduces the amount of tissue exposed, which lowers patient dose and decreases scatter radiation that can blur the image. This field limitation helps ensure consistent technique and better image quality by concentrating the exposure on the necessary anatomy. The other functions listed belong to different components (converting X-rays to visible light, moving the table, or measuring exposure time), not to the collimator.