Superparamagnetic iron oxides as positive MR contrast agents: in vitro and in vivo evidence.
The ability of superparamagnetic iron oxides (SPIO) and ultrasmall superparamagnetic iron oxides (USPIO) to act as positive contrast enhancers due to a marked T1 relaxivity was investigated. At low concentrations, an important signal enhancement was observed in vitro, reaching 120% for SPIO and 140% for USPIO in a spin echo 500/22 sequence. The more heavily the sequence was T1-weighted the greater the enhancement. As the concentration increased, the signal dropped. The in vivo study of USPIO in the rat showed that at low doses (14 mumol Fe/kg), the myocardial signal was enhanced by 30%, whereas at high doses (77 mumol Fe/kg), it fell by -50%. These results indicate that in T1-weighted spin echo sequences, the MR signal can be enhanced by low concentrations of superparamagnetic compounds. This effect could be useful in perfusion imaging, and is also important for a better understanding of any possible paradoxical positive enhancement which could occur in perfused organs.
Chambon
C
C
Laboratoire Guerbet, Aulnay-Sous-Bois, France.
Clement
O
O
Le Blanche
A
A
Schouman-Claeys
E
E
Frija
G
G
D000818:Animals; D003287:Contrast Media; D003911:Dextrans; D052203:Ferrosoferric Oxide; D006321:Heart / Q000033:anatomy & histology*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D066298:In Vitro Techniques; D007501:Iron; D008099:Liver / Q000033:anatomy & histology*; D008279:Magnetic Resonance Imaging; D058185:Magnetite Nanoparticles; D008297:Male; D008961:Models, Structural; D010087:Oxides; D051381:Rats; D017207:Rats, Sprague-Dawley
D003287:Contrast Media; D003911:Dextrans; D058185:Magnetite Nanoparticles; D010087:Oxides; C097921:ferumoxtran-10; D007501:Iron; C065507:ferumoxides; D052203:Ferrosoferric Oxide