<prompt> The dental x-ray beam is collimated to a circle of:7 cm in diameter5 cm in diameter6 cm in diameter9 cm in diameter  <response>: Collimation is a process by which x-ray beam size is reduced and thereby decrease the patient exposure. It is made up of metallic barrier usually Pb with an aperture in the middle to reduce the size of the x-ray beam.Most state regulations require that the x-ray beam used in intraoral radiography be collimated so that the field of radiation at the patients skin surface is no more than 7 cm 2.75 inches in diameter. 