What is the primary purpose of a thyroid collar in dental radiography?

• A. Protect the clinician's neck
• B. Shield the patient's thyroid from scatter radiation
• C. Support the patient's head
• D. Improve image sharpness

Answer: (B)

The main idea here is protecting sensitive tissues from radiation. The thyroid collar’s purpose is to shield the patient's thyroid gland from scatter radiation during dental radiography. The thyroid is highly radiosensitive, and photons scattered by the X-ray beam can reach the neck even if the thyroid isn’t in the direct beam. A lead or lead-equivalent collar placed around the neck absorbs much of those scattered photons, reducing the radiation dose to the thyroid without noticeably affecting image quality when positioned properly. It isn’t meant to protect the clinician, nor to support the head or improve sharpness. Its role is specifically to minimize thyroid exposure while allowing the radiograph to be taken accurately.