The use of iron oxide as a superparamagnetic contrast agent for magnet
ic resonance imaging of the liver has been described previously, When
administered intravenously, superparamagnetic iron oxide (SPIO) is seq
uestered by the reticuloendothelial system causing significant shorten
ing of the T2-relaxation time. The majority of the contrast is taken u
p by the reticuloendothelial tissue of the liver. Since tumours have r
educed or absent reticuloendothelial tissue the effect on relaxation t
ime is minimal and signal intensity differences between tumour and liv
er are increased, AMI 25 (Laboratoire Guerbet, Paris) is a colloidal s
olution of ferrous and ferric oxides, We have performed MR examination
of the liver in 16 patients with focal liver lesions using AMI 25 as
a superparamagnetic contrast agent, Our results indicate that SPIO sig
nificantly increases the conspicuity of focal lesions and the effect i
s greatest in malignant tumours. We observed no adverse reaction to th
is contrast agent.