Positron emission tomography with fluorodeoxyglucose in fever of unknown origin and infectious and non-infectious inflammatory diseases.

In management of patients with fever of unknown origin (FUO) or suspected infectious or inflammatory disease, timely identification and localization of infectious and inflammatory lesions is essential for optimal treatment. Since activated inflammatory cells take up large amounts of glucose as a result of an increased metabolic rate, 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) represents a promising imaging technique in these patients. The aim of the studies presented in this thesis was to further investigate the clinical value of FDG-PET in diagnosis of FUO and several infectious and inflammatory diseases. It is shown that FDG-PET is a useful diagnostic technique as part of a structured diagnostic protocol in all patients with FUO. FDG-PET contributed to the final diagnosis in 33% of all FUO patients in whom the chance of reaching a diagnosis was only 50%. In patients with bacteremia or candidemia and a high risk of metastatic infection, FDG-PET was also able to identify metastatic infectious foci, which were, in many cases, not found by conventional diagnostic techniques. Identification of these metastatic infections led to a change of treatment in most patients. Lipodystrophy, a serious complication of antiretroviral therapy in HIV-infected patients, is accompanied by adipose tissue inflammatory activity and by mitochondrial toxicity resulting in metabolic stress. FDG-PET was able to visualize lipodystrophy in HIV-infected patients. In addition, FDG-PET showed promising results in the imaging of different types of vasculitis, including giant cell arteritis, polyarteritis nodosa, Takayasu arteritis, Churge-Strauss syndrome, and Wegener's granulomatosis. However, at present, the diagnostic value of FDG-PET is only sufficiently studied in patients with FUO to recommend its use as part of a structured diagnostic protocol in clinical practice. Although results were invariably promising, in most other cases results of larger prospective studies should be awaited before widespread clinical use can be recommende