What are the two types of filtration used in radiology?

In radiology, the two main types of filtration that are used to improve image quality and reduce the patient's exposure to unnecessary radiation are inherent filtration and added filtration.

Inherent filtration refers to the filtration that is built into the X-ray tube itself. This includes the glass or metal envelope of the tube and any other materials that are an integral part of the X-ray machine. These components naturally absorb lower-energy photons from the X-ray beam, which do not contribute to image formation and would add to the patient's dose without providing diagnostic information.

Added filtration, on the other hand, consists of additional materials placed in the path of the X-ray beam outside the tube housing. Common materials used for added filtration include aluminum sheets. By incorporating added filtration, radiologists can further eliminate low-energy photons from the beam. This increases the overall quality of the X-ray image and ensures that the radiation dose to the patient is as low as reasonably achievable (ALARA principle).

Together, inherent and added filtration work to optimize the X-ray beam, enhance image quality, and minimize patient exposure to radiation, making this answer the most appropriate choice in the context of how filtration operates in radiology.