QUANTITATIVE METHODS FOR INDIRECT CT LYMPHOGRAPHY

In this investigation, we applied quantitative CT methods to character ize contrast enhanced lymph nodes opacified using iodinated contrast m edia for indirect CT lymphography. Iodinated nanoparticles were inject ed into the buccal submucosa and SQ into the metatarsus and metacarpus of four normal swine (1.0-4.0 ml/site, 76 mg I/ml). Attenuation (HU), volume (cm(3)), iodine concentration (mg I/cm(3)), total iodine uptak e (mg I), contrast-to-noise ratio (CNR), and percent injected dose (%I D) were estimated in opacified inguinal, cervical and parotid/mandibul ar lymph nodes using manual image segmentation techniques on 24 hour p ost-contrast CT images. Lymph node volumes estimated by multiple slice ROI analysis were compared with estimates obtained by post-excisional weight measurements. HU and iodine concentration increased 5-20 fold in opacified nodes (p < 0.01) and CNR increased more than four-fold (p < 0.001), %ID ranged between 3.5 and 11.9% and did not appear dose re lated. ROI estimated lymph node volumes approximated volumes calculate d from weight measurements. (R-2 = 0.94, p < 0.0001). We conclude that interstitially injected iodinated nanoparticles increase attenuation and conspicuity of targeted nodes on CT images. Quantitative methods c ould play an important clinical role in more accurate metastasis detec tion.