Magnetic starch microspheres in the MR imaging of hepatic metastases. A preclinical study in the nude rat.
OBJECTIVE
To evaluate reticular endothelial system-specific magnetic starch microspheres (MSM) as an i.v. contrast agent for MR imaging in a model of experimental liver metastases.


METHODS
The study comprised 15 nude rats, 7 of which were carrying hepatic metastases from a human colonic cancer. The 15 rats were examined at 0.5 T using a T1-weighted spin-echo (SE) sequence and a gradient-echo sequence. The examinations were performed before and 15 min after the administration of accumulated doses of MSM at 0.25-2.5 mg Fe/kg b.w. The images were compared with corresponding serial liver specimens.


RESULTS
A loss of liver signal intensity was obtained at all MSM dose levels. No metastases were detected in the pre-contrast images. The optimum detection rate of hepatic metastases was reached with the SE sequence at a dose of 1.0 mg Fe/kg b.w. MSM and the diameters of the smallest lesions depicted were 1 mm. However, in the SE sequence, the measured lesion-to-liver contrast and liver signal damping were highest at the largest dose, indicating a possible image degrading effect of MSM at high doses. Administration of MSM as a short bolus over 30 s resulted in congestion of the liver with dilatation of the hepatic veins. When MSM was instead injected slowly over 5 min, this adverse effect was not seen.


CONCLUSIONS
The use of MSM dramatically increased the detection of experimental hepatic metastases.
Sundin
A
A
Department of Diagnostic Radiology, University Hospital, Uppsala, Sweden.
Wang
C
C
Ericsson
A
A
Fahlvik
A K
AK
D000818:Animals; D003110:Colonic Neoplasms / Q000473:pathology; D003287:Contrast Media; D008099:Liver / Q000473:pathology; D008114:Liver Neoplasms, Experimental / Q000175:diagnosis* / Q000556:secondary*; D008279:Magnetic Resonance Imaging; D008297:Male; D009368:Neoplasm Transplantation; D051381:Rats; D011923:Rats, Nude; D014407:Tumor Cells, Cultured
D003287:Contrast Media