Mediastinal lymph node detection and sizing at CT and autopsy

Although CT has assumed a major role in the preoperative evaluation of the mediastinum in patients with lung carcinoma, there is no consensus as to its accuracy or efficacy in this setting. A potential source of CT error is inaccurate detection or sizing of lymph nodes in particular mediastinal locations because of inadequate contrast with surrounding tissue or partial volume effects. We imaged five cadavers with CT and then meticulously dissected the mediastinal nodes. The nodes were measured and categorized by using the lymph node mapping scheme of the American Thoracic Society. The short axis nodal diameter was the best CT predictor of nodal volume. Excellent correlation was found between CT and autopsy for lymph node detection in right-sided mediastinal lymph nodes; poorer CT/autopsy correlation was found for left-sided lymph nodes, especially in the lower left peribronchial region. These findings suggest that CT may be less accurate in identifying left-sided mediastinal metastases.