RES-specific imaging of the liver and spleen with iron oxide particles designed for blood pool MR-angiography.
The purpose of this study was to determine the dependency of liver- and spleen-enhancement on particle size and dose of bolus-injectable iron oxides designed for blood-pool MR-angiography (MRA). The superparamagnetic iron oxide SHU 555 A [particle size 65 nm (group 1)] and three derivatives designed for blood-pool MRA (groups 2-4) with smaller hydrodynamic diameters (46/33/21 nm) were i.v. injected in New Zealand White rabbits at doses of 10, 20, or 40 micromol Fe/kg bw. MRI was performed before, 2, and 24 hours after contrast application using T1-weighted SE and T2-weighted TSE sequences. In addition splenic tissue was harvested post mortem and scanned ex vivo. All iron oxides significantly decreased the SI of liver and spleen in T1- and T2-weighted images at 2 and 24 hours after application of contrast media (P < 0.01). The signal intensity was inversely related to the dose applied. Decreasing particle size resulted in a lower signal enhancement in liver and spleen. However, ultra-small superparamagnetic iron oxides suited for blood-pool MRA (USPIOs, group 4) still revealed a significant signal enhancement in the liver and spleen even 24 hours after contrast application (< - 60%, 40 micromol Fe/kg bw). They might thus be used for comprehensive abdominal studies including contrast enhanced MR-angiography and RES-specific imaging.
Bremer
C
C
Department of Clinical Radiology, Westfaelische Wilhelms-Universitaet Muenster, Albert-Schweitzer-Strasse 33, D-48129 Muenster, Germany. bremerc@uni-muenster.de
Allkemper
T
T
Baermig
J
J
Reimer
P
P
D000704:Analysis of Variance; D000818:Animals; D003287:Contrast Media / Q000008:administration & dosage* / Q000737:chemistry; D003911:Dextrans; D005260:Female; D052203:Ferrosoferric Oxide; D007089:Image Enhancement / Q000379:methods; D007501:Iron / Q000008:administration & dosage* / Q000737:chemistry; D008099:Liver / Q000033:anatomy & histology*; D018810:Magnetic Resonance Angiography / Q000379:methods*; D058185:Magnetite Nanoparticles; D012157:Mononuclear Phagocyte System / Q000033:anatomy & histology*; D010087:Oxides / Q000008:administration & dosage* / Q000737:chemistry; D010316:Particle Size; D019047:Phantoms, Imaging; D011817:Rabbits; D011897:Random Allocation; D013154:Spleen / Q000033:anatomy & histology*
D003287:Contrast Media; D003911:Dextrans; D058185:Magnetite Nanoparticles; D010087:Oxides; D007501:Iron; C065507:ferumoxides; D052203:Ferrosoferric Oxide