Lymph node extraction of radiopaque nanoparticulates in the rabbit as measured in vivo with CT.

RATIONALE AND OBJECTIVES: The purpose of this study was to estimate in vivo extraction of lymphographic material in the popliteal node of the rabbit. MATERIALS AND METHODS: Serial quantitative computed tomography (CT) of target tissues in four legs of two rabbits was performed after subcutaneous injection of an improved lymphographic contrast agent. Massage was used as a lymphotrophic intervention. RESULTS: At 15 minutes, the mean change in Hounsfield units measured 815 in the popliteal node, 219 in afferent lymphatic vessels, and 127 in efferent lymphatic vessels. The nodal extraction of nanoparticulates from the lymph was approximately 55%. Nodal massage allowed the amount of nanoparticulate remaining in sinusoidal lymph to be estimated. CONCLUSION: Functional CT performed with timed studies, proper radiopaque materials, and physiologic interventions can depict in vivo lymphatic physiology under minimally invasive conditions.

Time-lapse quantitative computed tomography lymphography: assessing lymphatic function in vivo.

RATIONALE AND OBJECTIVES: Immobility and massage produce different local limb lymph flow rates. We studied their influence on accumulation of radiopaque nanoparticulates in regional lymph nodes of normal rabbits. METHODS: Quantitative lymphography at 10-min intervals was used to follow the transport of subcutaneous (s.c.) nanoparticulates produced from insoluble esters of diatrizoic acid. In one design, both hindpaws received 0.5 ml of nanoparticulate s.c., and one hindpaw was massaged. In a second design, one hindpaw was injected and massaged while imaging the popliteal, presacral, and paraaortic nodes every 10 min. RESULTS: Gentle massage rapidly increased popliteal node accumulation in comparison with the immobile limb. On the massaged side, mean Hounsfield (HU) units, maximum Hounsfield units, and calculated iodine were significantly greater at 10 min and all subsequent times. In the node transfer experiments, it took 12, 30, and 45 min, respectively, to obtain 100-HU mean attenuation; 200-HU maximum attenuation thresholds were achieved at 20, 47, and 69 min, respectively. CONCLUSION: Quantitative computed tomography lymphography reflects local lymph physiology. Gentle massage of the s.c. injection site is a powerful lymphotropic stimulus.

Nanoparticulate computed tomography contrast agents for blood pool and liver-spleen imaging.

RATIONALE AND OBJECTIVES: We investigated the properties of a group of iodine-containing, insoluble compounds formulated as nanoparticles for use as potential blood pool and liver-spleen contrast agents. METHODS: High-resolution, quantitative computed tomography (CT) was performed prior to and at intervals following the intravenous administration of the contrast agents to rabbits. Time-density characteristics for three organs were evaluated. RESULTS: Excellent enhancement of blood (< or = 232 Hounsfield units [HU]), liver (< or = 263 HU), and spleen (< or = 350 HU) was achieved at the administered dose of 3.0 ml/kg. The composition of the agents influenced the biodistribution, as well as the residence time in blood, and time to peak enhancement in liver. CONCLUSION: Iodinated nanoparticulate compounds are promising CT contrast agents. Development of agents with desirable pharmacokinetic and biodistribution profiles may permit application-specific contrast enhancement.