The applied SPECT system was an Infinia 8+Hawkeye 4 (GE Healthcare, Milwaukee, WI, USA), equipped with ultra-high-energy, high-resolution collimators. The spatial resolution (full width at half maximum value) of this system was 8.6 mm at 140.5 keV and 11.8 mm at 511 keV. The rotation orbit was circular, the matrix size was 64×64, and the image reconstruction pixel size was 3.2×3.2 mm. The energy was set at 140.5±10.0% keV for 99mTc and 511.0±7.5% keV for 18F. Xeleris (GE Healthcare, Milwaukee, WI, USA) was employed for data processing, and reconstruction was based on the implementation of the ordered subset expectation maximization algorithm (OSEM) (6 (link), 7 (link)).
The number of iterations in OSEM was set at 10, and five subsets were used (7 (link)). A Butterworth filter (order 7, cut-off frequency=0.37 cycle/cm) was used as the pre-filter. The same pre-filter was used for both radionuclides, since myocardial accumulation of 18F-FDG is not constant; in fact, image quality is not fixed when the pre-filter changes in each case.
The number of iterations in OSEM was set at 10, and five subsets were used (7 (link)). A Butterworth filter (order 7, cut-off frequency=0.37 cycle/cm) was used as the pre-filter. The same pre-filter was used for both radionuclides, since myocardial accumulation of 18F-FDG is not constant; in fact, image quality is not fixed when the pre-filter changes in each case.