Indirect computed tomography lymphography using iodinated nanoparticles to detect cancerous lymph nodes in a cutaneous melanoma model

Rationale and Objectives. To evaluate differences in contrast uptake in normal and cancerous lymph nodes on indirect computed tomography (CT) in swine, we conducted lymphographic examinations after subcutaneous injection of a lymphotropic iodinated nanoparticle suspension. Methods. Perilesional subcutaneous contrast injections (2 ml per lesion) of a 15% wt/vol iodinated nanoparticle suspension were made in immature Sinclair miniature swine (n = 5) with cutaneous melanomas, Average attenuation, iodine concentration, node volume, and total iodine uptake were estimated on the CT scans for each opacified lymph node 24 hr after injection. Nodes were classified as normal or cancerous microscopically, and the percentage of tumor replacement was estimated in cancerous nodes. Results. Average attenuation and iodine concentration were higher in normal nodes, and total iodine uptake was higher in cancerous nodes with greater than 25% replacement (p < .05). Architectural alterations in opacified cancerous nodes included medullary filling defects, expansile cortical lesions, and disruption of corticomedullary junctions. Conclusion. Quantitative and qualitative differences in iodinated nanoparticle enhancement characteristics are useful in distinguishing between normal and cancerous lymph nodes on indirect CT lymphography examinations.