The relation between the blood glucose level and the FDG uptake of tissues at normal PET examinations

BACKGROUND: The influence of the blood glucose level on the tracer uptake of normal tissues at [(18)F]-2-fluoro-2-deoxy-d-glucose (FDG) positron emission tomography (PET) was retrospectively studied in examinations in clinical patients. METHODS: Five hundred examinations were evaluated in retrospect. The inclusion criteria were studies with a normal or near-normal FDG distribution. Patients who had been subjected to chemotherapy (including GSF treatment) or radiotherapy <4 weeks prior to the examination were excluded; we cannot exclude, however, that in a very few patients the available information might have been incomplete. Otherwise, patients were included regardless of concurrent diseases and/or therapy. In one evaluation, the mean standardized uptake value of the liver, spleen, lungs, peripheral blood, selected muscles and bone marrow of all 500 individuals was correlated to the blood glucose level. In another evaluation, a subgroup of 62 patients with increased blood glucose levels (≥7.0 mmol/l) was compared with another subgroup of 62 patients paired with regard to age and gender with blood glucose levels within normal range (≤6.0 mmol/l). RESULTS: There was a weak positive correlation between the blood glucose level and the muscular uptake of FDG, while there was no correlation with the tracer uptake of the liver, spleen, lungs, peripheral blood or bone marrow. The patient group with increased blood glucose levels showed a slightly, but significantly, higher muscular FDG uptake compared with the matched subgroup of patients with normal blood glucose levels. When comparing the other assessed tissues/organs, there were no differences between these two patient groups. CONCLUSIONS: The effect of hyperglycaemia at FDG PET on the studied normal tissues is restricted to a slightly increased muscular uptake. The effect of the blood glucose level on the blood activity at the time of examination is negligible.