CLINICAL MEDICINE

Detailed explanation-1: -The X-ray beam shall be restricted to a diameter of not more than 7 cm (2.75 inches) in diameter at the surface of the skin. This size of the X-ray beam is sufficient to allow for reasonable alignment errors.

Detailed explanation-2: -Specifically, federal regulations require internal and external cylindrical collimators to restrict the intraoral X-ray beam exiting the position-indicating device (PID) to a diameter of no more than 2.75 inches (7 cm) on the patient’s skin. Rectangular collimation can help practitioners comply with these regulations.

Detailed explanation-3: -When using a circular collimator, federal regulations require that the x-ray beam be collimated to a diameter of no more than 2.75 inches as it exits from the position-indicating device and reaches the skin of the patient.

Detailed explanation-4: -a diaphragm, usually made of lead, used to restrict the size and shape of the xray beam.