Measurement of axillary lymph nodes in a patient with invasive ductal carcinoma in the left breast. A. ALN sizes were measured in the maximum sectioned surface of the CT image with 3-mm slices: (1) Longest transverse diameter of the oval lymph node; (2) Shortest transverse diameter of the oval lymph node; B. To measure mean HU, we selected a range of interest (ROI) such that the line did not protrude from the ALN edge. C. ROI surrounded the lymph node, and the maximum HU inside of the ROI was measured. We took extra care not to include bone or blood vessels near the ROI.