Which of the following materials is NOT typically used as a filter in fluoroscopy?

In fluoroscopy, filters are used to remove low-energy photons from the x-ray beam, which helps to improve the overall image quality and reduce patient dose. The most commonly used materials for filtering in fluoroscopy include aluminum, copper, and rhodium, as these materials have the appropriate atomic properties to efficiently absorb the unwanted low-energy x-rays.

Aluminum is widely used due to its effectiveness in removing low-energy radiation and is a standard component in the protective filters found in many fluoroscopic systems. Copper also serves effectively as a filter, particularly in certain applications where additional beam hardness is required. Rhodium is less common than aluminum but can be utilized for specific applications, enhancing image contrast and quality.

In contrast, plastic is not typically used as a filter in fluoroscopy. While it might serve in certain contexts, it lacks the necessary density and atomic number to effectively attenuate x-rays, especially in comparison to metals like aluminum, copper, and rhodium. Therefore, plastic does not provide the filtering characteristics needed to improve image quality or patient safety in fluoroscopic procedures.