Discovery st

All patients underwent an initial contrast-enhanced CT scan for radiation therapy planning. After receiving ~30–36 Gy radiation dose, patients went through a second contrast-enhanced CT scan for radiation re-planning, to account for potential anatomic change due to tumor regression, node shrinkage, or weight loss. Two types of CT scanners were used including General Electric Discovery ST (n=52) and Siemens Biograph (n=88). CT scans were acquired at a tube potential of 120 kV and a tube current of 190–600 mA. CT images were reconstructed at a slice thickness of 1.5–2.5 mm, and in-plane spatial resolution of 0.98×0.98 – 1.17×1.17 mm².

The chest CT and PET/CT scans were acquired using various protocols and scanners at our medical center across a ten-year time frame. The CT scanners used during the study years included GE Medical Systems (models: Optima-CT660, LightSpeed-VCT, LightSpeed-Ultra) and Siemens (models: Emotion and Emotion-Duo). The CT images were consistently reconstructed to encompass the entire lung field in a 512×512 pixel matrix. The in-plane pixel dimensions ranged from 0.55 to 0.81 mm, depending on participant body size. The image thickness ranged from 0.625 mm to 2.5 mm. The PET/CT scanners were manufactured by GE Medical Systems (model: Discovery ST), CPS (model: 1023), and Siemens (Emotion and Emotion-Duo). PET/CT scans were typically obtained from the head to the upper portion of the thigh on an integrated PET/CT scanner. The PET images had a matrix size of 128 × 128 with an in-plane resolution ranging from 4.1 mm to 5.5 mm. The image thickness of the PET images ranged from 2.5 mm to 3.38 mm.