What does the term differential absorption relate to in radiography?

The term differential absorption in radiography refers to the variation in the absorption of X-rays by different tissues or materials based on their atomic number and density. When X-rays pass through the body, various tissues absorb different amounts of radiation, leading to varying levels of exposure on the radiographic film or digital detector. This difference in absorption helps to enhance the contrast between different tissues, which is crucial for identifying structures and anomalies within the body.

While it is true that beam intensity can affect the final image, and that subject contrast relates to the ability to distinguish between different tissues, the concept of differential absorption is most fundamentally linked to the specific interaction of X-rays with various types of tissue due to their unique properties. Thus, it primarily pertains to the differences in how various pathologies or normal anatomy absorb X-rays, making it most closely associated with pathology. When diagnosing medical conditions, understanding differential absorption is essential as it can highlight areas of interest, such as tumors or lesions, which may present differently due to their composition in comparison to surrounding tissue.