Imaging equipment: German Siemens Biograph mCT (64) PET/CT scanner. Image acquisition: the patients were required to fast for 4–6 h before examination, and the height, weight, and blood sugar on the day of examination were recorded; PET/CT whole-body imaging was performed 1 h after the imaging agent (18F-FDG, 3.70–5.55 MBq/kg) injection, and was imaged first with low-dose CT and then PET scan. PET imaging was performed at 2 min/bed, about six to seven beds per patient according to their heights. The TrueX + TOF (ultraHD-PET) method was used for image reconstruction, with two iterations and 21 subsets; the matrix was 200 × 200, and the image acquisition mode was 3D. The post-processing workstation TrueD system (Siemens) was used for image evaluation (lung window width 1,200 HU, window level −600 HU, mediastinal window width 350 HU, window level 40 HU).
Then, the HRCT scan was performed on the GGN site under a breath-hold condition. The collection and reconstruction conditions were as follows: the tube voltage was 140 kV, and the tube current was automatically adjusted by caredose software according to human anatomy and tissue density; the rotation time was 0.5 s, the pitch was 0.6, the layer thickness was 1.0 mm, the layer interval was 0.5 mm, the matrix was 512 × 512, and the lung and mediastinal windows were set as before.
Then, the HRCT scan was performed on the GGN site under a breath-hold condition. The collection and reconstruction conditions were as follows: the tube voltage was 140 kV, and the tube current was automatically adjusted by caredose software according to human anatomy and tissue density; the rotation time was 0.5 s, the pitch was 0.6, the layer thickness was 1.0 mm, the layer interval was 0.5 mm, the matrix was 512 × 512, and the lung and mediastinal windows were set as before.