American Society of Radiologic Technologist (ASRT) Practice Exam

Primary shielding refers to protective measures implemented to prevent radiation exposure to personnel and the public during radiologic procedures. It is designed to intercept radiation before it has the chance to reach areas where exposure could occur.

Collimation is considered a type of primary shielding because it involves the use of a device that narrows the beam of radiation to a specific area, thereby limiting unnecessary exposure to surrounding tissues and reducing scatter radiation. By carefully shaping and directing the radiation beam, collimation serves as a barrier, effectively protecting individuals in the vicinity from radiation.

In contrast, while lead aprons, shadow shields, and shaped contact shields are important protective measures, they are classified as secondary shielding. These options are used to protect against radiation that has already been emitted and is in the process of scattering. Therefore, collimation specifically functions as a primary method of shielding by controlling and limiting the radiation emitted from the source.