CT evaluation of mediastinal lymphadenopathy: noncontrast 5 mm vs postcontrast 10 mm sections

Two CT techniques were compared in the assessment of mediastinal lymph nodes: 5 mm thick sections without intravenous contrast medium and 10 mm thick sections with intravenous contrast medium.

Seventy-nine adult patients were examined by chest CT. From the level of the aortic arch through the level of the right middle lobe bronchus 5 mm thick sections were performed without intravenous contrast medium, followed by 10 mm thick sections of the same region with intravenous contrast medium. Two chest radiologists separately reviewed each CT method for each patient. Mediastinal lymph nodes were localized according to the American Thoracic Society scheme. Lymph node diameter was measured on the short axis.

The 5 mm thick noncontrast sections permitted identification of more mediastinal lymph nodes than the 10 mm thick contrast enhanced sections (p < 0.01, signed rank test). The 5 mm thick unenhanced sections tended to show slightly (1-2 mm) larger nodes than the 10 mm thick contrast enhanced sections (stations 7, 10R, both reviewers, p < 0.05, signed rank test). Nodes with a short axis diameter > or = 8 mm were identified comparably well using either CT technique.

The present study indicates that CT of the mediastinum using 5 mm thick sections, without intravenous contrast medium, is an appropriate scanning technique for evaluation of mediastinal lymphadenopathy.