PET Imaging of Infection

Nuclear medicine has played an important part in the diagnosis of infection for 50 years. Gallium-67 citrate was one of the first radionuclides used for diagnosing and localizing infection. The development of techniques for radiolabeling leukocytes and monitoring their migration to foci of infection was a significant advance. More recently, investigators have worked on developing positron-emitting radiopharmaceuticals for diagnosing infection. Positron emission tomography (PET) provides high-resolution three-dimensional images, facilitating precise localization of radiopharmaceutical uptake. Semiquantitative analysis could facilitate the differentiation of infectious from noninfectious conditions and could be used to monitor treatment response. Not surprisingly, the first PET agent investigated was fluorine 18-fluorodeoxyglucose (18F-FDG). Although 18F-FDG has proved to be invaluable for diagnosing infection, it is not specific, and also accumulates in neoplasms, and noninfectious inflammatory conditions. Considerable effort has been devoted to developing PET radiopharmaceuticals that are specific, or at least more specific than 18F-FDG, for infection. Investigators have explored the potential of leukocytes labeled in vitro with various PET radiopharmaceuticals, gallium-68 citrate, gallium-68 labeled peptides, iodine-124 fialuridine, and 18F-fluorodeoxysorbitol. This chapter reviews the role of 18F-FDG for diagnosing infection and monitoring treatment response and other PET agents whose potential for diagnosing infection has been studied.