What is the main purpose of using a rectangular collimator during radiography?

The main purpose of using a rectangular collimator during radiography is to reduce radiation exposure to the patient. The collimator shapes and narrows the x-ray beam to the area of interest, which helps ensure that only the necessary tissues are exposed to radiation. By limiting the size of the x-ray beam, the dose of radiation that the patient receives can be significantly minimized, ultimately enhancing safety and reducing the risk of unnecessary exposure to surrounding tissues.

While other options might seem relevant, they do not align with the primary function of a rectangular collimator. For example, although a collimator can assist in lining up the receptor with the x-ray source, its main impact on patient safety is through reducing unnecessary radiation exposure. Similarly, while it may help in reducing exposure time by limiting the area needing imaging, its design fundamentally focuses on beam size and patient protection.