The potential of seven tracers for the metabolic imaging of
tumors by positron emission tomography was studied using five experimental
tumor models. The tracers examined were 2-deoxy-2-[18F]fluoro-
D-glucose ([18F]FDG), 2-deoxy-2-[18F]fluoro-
D-galactose (2-[18F]
FdGal) and 2-deoxy-2-[18F]fluoro-L-
fucose (2-[18F]FdFuc) for investigating energy metabolism. L-[methyl-11C]
Methionine ([11C]Met) and 6-[18F]fluoro-L-
fucose (6-[18F]FFuc) were used for assessing
protein and
glycoprotein synthesis, while [3H]
thymidine ([3H]Thd) and 2-deoxy-5'-[18F]fluorouridine ([18F]FdUrd) were used to investigate
nucleic acid metabolism. The highest mean uptake by the five different
tumors was found for [3H]Thd, followed in order by [18F]FDG, [11C]Met, 2-[18F]
FdGal, [18F]FdUrd, 2-[18F]FdFuc and 6-[18F]FFuc. The
tumor-to-tissue uptake ratios indicated that the
nucleosides, [11C]Met and 6-[18F]FFuc were better tracers in the brain region. All the tracers except for the
fucose analogs were suitable for the thoracic region, while [11C]Thd and [18F]FDG were superior in the abdominal region. In comparison with the primary
tumor model of
Lewis lung carcinoma (3LL), [3H]Thd uptake in the artificial metastatic 3LL model showed the maximum enhancement, followed by [18F]FDG, [11C]Met and the other tracers. The [18F]FDG uptake correlated with the [3H]Thd uptake. [18F]FdUrd, 6-[18F]FFuc and 2-[18F]
FdGal could be used for distinguishing different types of
tumors. The combined use of these radiotracers can possibly allow the assessment of
tumor metabolism, and this indicates the viability of
tumors.