Mechanisms of accumulation of small particles of iron oxide in experimentally induced osteosarcomas of rats: a correlation of magnetic resonance imaging and histology. Preliminary results.
OBJECTIVE
This study was conducted to investigate the distribution and kinetics of small particles of iron oxide in osteosarcoma-like tumors.


METHODS
Magnetic resonance (MR) imaging was performed in eight athymic nude rats with an experimentally induced osteosarcoma of the right hind leg immediately after intravenous injection of a superparamagnetic iron oxide preparation. Five animals received 150 mumol iron oxide/ kg and three received 50 mumol iron oxide/kg. The iron oxide preparation consisted of polythylenglycol-coated particles with a core diameter of 6 to 8 nm. The MR images were correlated with histologic slices of the tumors.


RESULTS
The tumors accumulated iron oxide rapidly. A marked decrease in signal intensity, preferentially along the periphery of the tumor, was followed by a partial return of the signal intensity within the first minute. The maximum signal decrement throughout the entire tumor exceeded 41% and 21% with one dose each of 150 mumol iron/kg and 50 mumol iron/kg, respectively. The rate of return depended on the injected dose and tumor area, with the signal intensity approaching the initial value before the injection of iron oxide after 45 minutes. Histologic correlation only showed deposition of contrast medium in the proliferative areas of the tumors, mainly confined to the tumor margin. In addition to a predominantly extracellular deposition, intracellular storage could be detected.


CONCLUSIONS
The findings help to advance the understanding of the distribution and kinetics of intravenous-injected small particles of iron oxide in osteosarcoma-like tumors. A first-pass accumulation of iron oxide could be documented by MR imaging in the periphery of osteosarcomas. Due to sieving of iron oxide particles by liver, spleen, and bone marrow, the signal intensity at 45 minutes after the injection of iron oxide returned to 89% (150 mumol iron oxide/kg) and 95% (50 mumol iron oxide/kg) of the preinjection intensity.
Axmann
C
C
Institute of Radiology, University of Luebeck, Germany.
Bohndorf
K
K
Gellissen
J
J
Prescher
A
A
Lodemann
K P
KP
D000818:Animals; D005290:Ferric Compounds / Q000008:administration & dosage / Q000493:pharmacokinetics*; D007275:Injections, Intravenous; D008279:Magnetic Resonance Imaging; D012516:Osteosarcoma / Q000175:diagnosis* / Q000378:metabolism* / Q000473:pathology; D051381:Rats; D011923:Rats, Nude; D012983:Soft Tissue Neoplasms / Q000175:diagnosis* / Q000378:metabolism* / Q000473:pathology
D005290:Ferric Compounds; C000499:ferric oxide