Biological Imaging for the Diagnosis of Inflammatory Conditions

Radiopharmaceuticals used for in vivo imaging of inflammatory conditions can be conveniently classified into six categories according to the different phases in which the inflammatory process develops. The trigger of an inflammatory process is a pathogenic insult (phase I) that causes activation of endothelial cells (phase II); there is then an increase of vascular permeability followed by tissue oedema (phase III). Phase IV is characterised by infiltration of polymorphonuclear cells, and a self-limiting regulatory process called apoptosis is observed (phase V). If the inflammatory process persists, late chronic inflammation takes place (phase VI). In some pathological conditions, such as organ-specific autoimmune diseases, chronic inflammation is present early in the disease.