Traditional radiological characteristics analysis
tumor, calcification, necrosis
CORTEX, TUMOR, LYMPH NODE METASTASIS, NECROSIS
Two radiologists, Reader 1 and Reader 2, with 5 and 10 years of experience in diagnostic abdominal radiology, respectively, conducted a thorough review of the CT images. In cases where there was a disagreement between the two radiologists, they would engage in joint discussions to reach a consensus. The evaluation of the CT findings, including the maximum diameter of the tumor on axial CT images, shape (on axial slice), location, boundary, calcification, necrosis, renal vein invasion and lymph node metastasis, was performed by the radiologists without access to clinicopathologic information.To determine the CT value of the tumor, a region of interest (ROI) was selected within the parenchyma of the tumor, excluding necrosis, calcification and vascularity. The ROIs in the study were chosen based on NP images as the tumor was clearly contrasted with the renal parenchyma in these images. Reader 1 selected three non-overlapping ROIs, took individual CT measurements for each, and then averaged the results. As CT scans are performed by different operators and on different patients, systematic inaccuracies in tumor CT value measurement may occur. To mitigate errors, the CT values of the cortex were measured in the cortical region of the kidney on the side of the tumor. Figure 
Selection of ROI and reference region. The average tumor attenuation value (TAV) for UP, CMP and NP was obtained from the ROI. The CT value measured in the renal cortex at each phase is known as the cortical attenuation value (CAV). The tumor enhancement value (TEV) and the cortex enhancement value (CEV) were calculated by subtracting the CT value of the UP: TEV