Which of the following best describes a "collimator" used during radiography?

A collimator is an essential component in radiography that plays a critical role in the quality of the radiographic image by focusing the beam of radiation. It narrows the divergent rays of the X-ray beam into a more manageable and precise area. This focusing ensures that only the necessary portion of the body is irradiated, thereby reducing the dose of radiation exposure to surrounding tissues and enhancing image quality by minimizing scatter radiation. The focused beam can result in clearer images and improved diagnostic capabilities.

Using a collimator also helps in aligning the radiation beam with the specific area that requires imaging, which is crucial for accurate diagnosis and treatment planning. Its design typically involves lead shutters that can be adjusted to shape the beam according to the needs of the procedure being performed.