CT imaging of intrathoracic lymph nodes in dogs with bronchoscopically administered iodinated nanoparticles

The purpose of the study was to determine if airway instillation of iodinated nanoparticles results in contrast material enhancement of tracheobronchial lymph nodes in dogs. Eight dogs underwent intrabronchial instillation of iodinated nanoparticles; six dogs received 900 mg each, and two dogs received 450 mg each. Spiral computed tomography (CT) was then performed 2–34 days later. CT scans obtained 2 days after instillation showed the presence of contrast material within the lung parenchyma but no nodal enhancement. Scans obtained 6–34 days after instillation showed enhancement of the right, left, and middle tracheobronchial lymph nodes (analogous to the mediastinal nodes in humans). Mean nodal attenuation on CT images was 117 HU ± 43, and the mean nodal volume was 129 mm 3 ± 113. Histologic specimens of the nodes showed macrophage hyperplasia. Iodinated nanoparticles instilled into small airways are transported to the tracheobronchial lymph nodes, where they result in contrast enhancement.