Discovery ste

All patients fasted for at least six hours and blood glucose level was < 200 mg/dL at the time of PET/CT. Whole-body PET and CT images were acquired 60 min after injection of 5.0 MBq/kg FDG without intravenous or oral contrast on a Discovery LS, a Discovery STE, or a Discovery MI DR PET/CT scanner (GE Healthcare, Milwaukee, WI). Continuous spiral CT was performed with an eight-slice helical CT (140 keV, 40–120 mA, Discovery LS) or 16-slice helical CT (140 keV, 30–170 mA, Discovery STE; 120 keV, 30–100 mA, Discovery MI DR). An emission scan was performed from head to thigh for 4 min per frame in two-dimensional mode (Discovery LS), 2.5 min per frame in three-dimensional mode (Discovery STE), or 2 min per frame in three-dimensional mode (Discovery MI DR). PET images were reconstructed using CT for attenuation correction using the ordered-subsets expectation maximization algorithm with 28 subsets and 2 iterations (matrix 128 × 128, voxel size 4.3 × 4.3 × 3.9 mm, Discovery LS), ordered-subsets expectation maximization algorithm with 20 subsets and two iterations (matrix 128 × 128, voxel size 3.9 × 3.9 × 3.3 mm, Discovery STE), or ordered-subsets expectation maximization algorithm with 18 subsets and four iterations (matrix 192 × 192, voxel size 3.9 × 3.9 × 3.3 mm, Discovery MI DR). The SUV was calculated by adjusting for administered FDG dose and patient body weight.

Tumor size was measured by magnetic resonance imaging. If tumor size was reported in three axes, the largest diameter was considered to be the tumor size.
All ¹⁸F-FDG PET/CTs were performed with dedicated PET/CT scanners (Discovery STe, GE Healthcare at Kyungpook National University Chilgok Hospital and Daegu Catholic University School of Medicine, Discovery ST/Discovery VCT, GE Healthcare at Yeungnam University Medical Center). All patients fasted for at least 6 h before the PET/CT. Blood glucose levels were measured and were required to be less than 150 mg/dL. A dose of approximately 5.5 MBq/kg of FDG was intravenously administered. At all institutions, PET/CT was performed from the thigh to the head, about 60 min after intravenous administration of FDG. Whole-body CT was performed without contrast enhancement using the following standard protocols: 140 kVp, 30 to 170 mAs adjusted to the patient’s body weight, and 3-mm slice thickness (Discovery STe); 100–120 kVp, 100–120 mAs, and 3.75-mm slice thickness (Discovery ST and Discovery VCT). An emission scan was performed in 3D mode after the CT scan. The acquisition time was 3 min per bed position. PET images were reconstructed by an iterative ordered subset expectation maximization algorithm using CT images for attenuation correction (Discovery STe, 4 iterations, 8 subsets; Discovery ST/Discovery VCT, 2 iterations, 8 subsets).