Time course of nodal enhancement with CT X-ray nanoparticle contrast agents: effect of particle size and chemical structure.
OBJECTIVE
Levels of CT enhancement in rabbit lymph nodes were followed with time after subcutaneous injection of four iodinated, insoluble nanoparticle contrast agents to provide experimental support for the hypothesis that clearance of these agents is related to the chemical structure of the agent itself. The impact of particle size was also studied.


METHODS
Subcutaneous injections (2 x 0.25 mL) were made in the dorsum of rabbit paws with 15% suspensions of four nanoparticle contrast agents. Images were obtained at 4, 10, 24, 48, and 72 hours and 5, 7, and 14 days after injection. Average attenuation (in Hounsfield units [HU]), node volume, and total iodine uptake were estimated from the CT scans for each lymph node at each time point.


RESULTS
All the agents provided adequate enhancement of both the popliteal and axillary lymph nodes of the rabbit (ie, > delta100 HU). Lymph node volume appears to be related to the persistence of enhancement, with long-lived agents demonstrating the greatest increase in size. The rate of clearance from the lymph nodes is related to the structure of the agent.


CONCLUSIONS
Clearance of insoluble, iodinated nanoparticle contrast agents from lymph nodes can be modulated by changes in the structure of the agent itself. Using the same agent, smaller particles deliver material to the lymph nodes more quickly and clear more quickly.
McIntire
G L
GL
Nycomed Amersham, PLC, Wayne, Pennsylvania, USA. mcintire11@aol.com
Bacon
E R
ER
Illig
K J
KJ
Coffey
S B
SB
Singh
B
B
Bessin
G
G
Shore
M T
MT
Wolf
G L
GL
D000818:Animals; D001565:Benzoates / Q000737:chemistry; D003287:Contrast Media / Q000737:chemistry; D008198:Lymph Nodes / Q000000981:diagnostic imaging*; D010316:Particle Size; D011817:Rabbits; D013997:Time Factors; D014057:Tomography, X-Ray Computed
D001565:Benzoates; D003287:Contrast Media; C112667:NC 67722