HIGH-ENERGY (511-KEV) IMAGING WITH THE SCINTILLATION CAMERA

A dual-head scintillation camera has been adapted for high-energy (511 -keV) imaging by extending the useful energy range and linearity maps to 560 keV, implementing high-energy sensitivity maps, and developing high-energy collimators. High-energy parallel-hole collimators have in ferior spatial resolution and sensitivity relative to the low-energy, high-resolution collimators commonly in use, With high-energy parallel -hole collimators, phantom studies show that the limit for detectabili ty of ''hot'' lesions is 1.5 cm and 1.3 cm in diameter or larger for 2 -[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) uptake ratios of 5:1 and 10:1, respectively, if one assumes adequate counting statistics. Dual- isotope, single-acquisition techniques for using technetium-99m methox y isobutyl isonitrile and FDG have been developed and proved useful in identification of ischemic but viable myocardium. High-energy fan-bea m collimators have superior spatial resolution but inferior sensitivit y relative to low-energy, high-resolution collimators, Metabolic image s of the brain obtained with FDG demonstrate spatial resolution compar able with that of positron emission tomography, but such studies are o ften Limited by inadequate counting statistics.