A clinical positron emission tomography facility. 2-[18-F]FDG studies: development and results

Positron emission tomography (PET) is a tracer technique used for quantitative in vivo studies of physiological and biochemical processes. Because of the use of positron-emitting radionuclides such as 11-C, 13-N, 15-O and 18-F, which are isotopes of the biologically ubiquitous elements, it is possible to label radiopharmaceuticals which trace biochemical processes precisely. In order to be able to utilize these useful positron-emitting radiopharmaceuticals without state-of-the-art PET systems, it is interesting to develop alternatives to standard commercial PET facilities.

Two different types of nuclear physics research accelerators have been used for the production of [18-F]fluoride, and the isotope produced has been used for radiolabelling of 2-[18F]fluoro-2-deoxy-D-glucose (2-18FDG). A rotating PET scanner, based on two scintillation camera heads, has been developed and used for human 2-18FDG studies. The suitability of an energy window in the Compton region for imaging 511 keV photons in scintillation camera systems has been evaluated. A new simplified method of normalizing clinical 2-18FDG PET results has been developed and validated, using erythrocytes as a reference tissue, requiring only one blood sample in the middle of the PET scan to calculate the integrated 2-18FDG input function with an accuracy better than ± 8%. An investigation using 2-18FDG PET to monitor the effect of therapy in advanced head and neck cancer patients has been performed. We found that low initial metabolic rate of glucose (MRgl ) predicted a complete local response. The second PET examination gave no further information for this group. In the group of primary tumours and lymph node metastases representing a combination of high initial MRgl and a small decrease in MRgl at the second PET examination, the outcome was unfavourable. An accurate normalization of 2-18FDG uptake was essential to evaluate the results of this study.