Dynamic liver imaging with iron oxide agents: effects of size and biodistribution on contrast.
In vivo effective relaxation rates in normal rat liver were evaluated for four dextran coated iron oxide agents: monocrystalline iron oxide nanocolloid (MION) with a mean particle diameter of 3.9 nm, a polycrystalline agent (PION) with a larger mean diameter of 12 nm, and these two agents labeled with the asialofetuin (ASF) protein for high hepatocytic receptor binding affinity (MION-ASF and PION-ASF). Using echo planar imaging at 2 Tesla, dose response was measured with measured with high temporal resolution for 3 h after injection of agent, and by comparing with relaxivities in vitro and in brain, dominant in vivo contrast phenomena were elucidated. While transverse relaxivity for PION-ASF exceeded that for MION-ASF by almost a factor of 2 in solution, relaxation rates in vivo became equivalent. Liver relaxation using non-ASF agents was consistent with rapid water exchange between vascular and extravascular compartments, which dominated relaxation as a result of agent accumulation in Kupffer cells.
Mandeville
J B
JB
MGH-NMR Center, Charlestown, MA 02129, USA.
Moore
J
J
Chesler
D A
DA
Garrido
L
L
Weissleder
R
R
Weisskoff
R M
RM
D000818:Animals; D001212:Asialoglycoproteins; D003287:Contrast Media / Q000493:pharmacokinetics; D017352:Echo-Planar Imaging; D005290:Ferric Compounds / Q000493:pharmacokinetics; D060748:Fetuins; D007091:Image Processing, Computer-Assisted; D066298:In Vitro Techniques; D008099:Liver / Q000033:anatomy & histology*; D008279:Magnetic Resonance Imaging; D008297:Male; D010316:Particle Size; D051381:Rats; D017207:Rats, Sprague-Dawley; D000509:alpha-Fetoproteins
D001212:Asialoglycoproteins; D003287:Contrast Media; D005290:Ferric Compounds; D060748:Fetuins; D000509:alpha-Fetoproteins; C017029:asialofetuin; C000499:ferric oxide