The uptake mechanisms of infection and inflammation imaging agents

Scintigraphic visualization of the localization of infection and inflammation is a challenging problem in clinical practice, because it may have important implications for the management of patients with infectious or inflammatory disorders. In order to enable clinicians to install rapidly the most appropriate treatment, adequate delineation and diagnosis of inflammatory foci in these patients is of critical importance. If the clinical history and physical examination are indecisive, the clinician can choose from several diagnostic modalities to determine the localization, the extent and the severity of the disease. New highly sensitive radiological investigations like magnetic resonance imaging (MRI) and spiral computerized tomography (CT) are able to locate relatively small focal abnormalities. However, these radiological methods rely on morphological changes, and as a result they are less accurate in early stages of infection or inflammation and are unable to discriminate active processes from anatomical changes due to a cured infection or after surgery. In contrast, radiopharmaceuticals used for imaging infection and inflammation accumulate in the infectious/inflammatory lesion due to the locally changed physiological condition, such as enhanced blood flow, enhanced vascular permeability, or influx of leukocytes. Thus, scintigraphic imaging does not depend on morphological changes, but is based on physiochemical processes in tissues. Therefore, scintigraphic techniques can also visualize infectious foci in their early phases, when morphological changes are not yet apparent. In addition, scintigraphic imaging is an excellent noninvasive method of whole-body scanning that can determine the extent of the infectious or inflammatory disease throughout the body. Here the characteristics of the radiopharmaceuticals that are currently used for infection and inflammation imaging are reviewed.