1.CT diagnosis of T stage T1: submucosal hypodense zone is visible or the thickness of cancer does not exceed 50% of the whole gastric wall. T2: The submucosal hypodense zone is not visible or the thickness of the cancer exceeds 50% of the whole gastric wall, but the plasma line is clear. T3: The cancer was demarcated from the outermost layer of the gastric wall or involved the entire distinguishable layer of the gastric wall, but the plasma membrane surface was smooth. T4a: The plasma membrane surface is not smooth or shows nodular outgrowth, and/or the perigastric fatty layer appears as a corded burr shadow or high-density banded infiltration. stage T4b: The perigastric fatty layer disappears, and the boundary with the surrounding organs is indistinct. Note: Tumor penetrating the muscular layer and entering the gastrocolic or hepatogastric ligament, or entering the greater or lesser omentum, but not penetrating the visceral peritoneum covering these structures, defined as T3, and if penetrating the visceral peritoneum tumor is defined as T4. 2. CT diagnosis of N stage The number of perigastric lymph nodes is innate, with an average of 36.2±15.2 and an average diameter of 87.5px, mainly distributed along the arterial vessels of the stomach. Criteria for determining lymph node metastasis: (1) lymph node size: ≥5-10 mm, short/long diameter ratio (≥0.7); (2) morphology (round or spherical); (4) distribution: distribution along blood vessels; (3) reinforcement characteristics: presence of non-reinforcing necrotic go or irregular reinforcement in the center of marginal reinforcement. N-stage (number of lymph node metastases): N1: 1-2; N2: 3-6; N3: ≥7 (N3a: 7-15; N3b: ≥16). 3.CT diagnosis of M stage (intra-abdominal) (1) thickening and irregular nodularity of mural peritoneum; (2) thickening and density increase of large omentum and mesentery; (3) omental cake; (4) parachute sign (increased density of small intestinal mesentery, thickening and straightening of intra-systemic vascular bundles in a fan-shaped extension, which is the result of cancer cells metastasizing to the mesenteric vessels via bloodstream, invading the vessel wall and making it thickened and stiff); (5) metastasis of intestinal canal (5) metastasis in the intestinal canal, manifested as nodules in the intestinal wall, thickening of the intestinal wall, stiffening and deformation of intestinal collaterals, and increased density of the intestinal mesentery and encapsulation of the intestinal canal; (6) metastatic carcinoma of the ovary (also called Krukenberg tumor); (7) ascites.