[Evaluation of thin section CT scanning in the prone position of metastatic axillary lymph nodes for breast cancer].

A retrospective study was performed to determine whether thin section CT scanning in the prone position of the breast and the axilla yielded useful information regarding the status of axillary lymph nodes in patients with breast cancer. Thirty-six patients with breast carcinomas were scanned preoperatively from the supraclavicular regions to the breast in the prone position with 5 mm sections. Axillary lymph nodes measuring > or = 5 mm on the short axis were considered abnormal. Correlation with axillary dissection was obtained in all patients, giving a positive predictive value for axillary metastases of 83.3%, with 88.2% sensitivity, 84.2% specificity, and 88.8% negative predictive value. We concluded that thin section CT scan in the prone position was an accurate predictor of axillary lymph node involvement. We made a phantom with lymph node swelling to evaluate whether CT scanning with 5 mm sections was necessary for detecting 5 mm swollen lymph nodes. We scanned the phantom with 5 mm and 10 mm sections. Twelve radiologists counted the swollen lymph nodes on 5 mm section images and 10 mm section images of the phantom. The average number of miscounts was 1.1 (miscount rate 6.8%) on 5 mm section and 2.8 (15%) on 10 mm sections. We concluded that 5 mm section CT scanning is superior for detecting 5 mm lymph nodes.