[Magnetic resonance imaging and spectrometric study of the distribution of thermotherapeutic magnetofluid after intra-arterial administration in an experimental model of liver metastases].

OBJECTIVE To use imaging and laboratory techniques to evaluate the vascular distribution of magnetofluid in a rat model of liver metastases. MATERIAL AND METHODS The livers of 33 WAG/Rij Crl rats were seeded with CC-531 colorectal cancer cells. After we checked tumor development, 10 rats received hepatic intra-arterial infusions of Lipiodol(®) with nanoparticles of Fe(3)O(4) in suspension, and 5 were reserved as controls. Axial STIR (TR: 3,600 ms/TE: 29 ms/TI: 130 ms) and gradient-echo (GE) (120/4 and 120/14) MRI sequences were acquired on a 1.5 T scanner. After necropsy, rats were classified into one of two stages according to tumor development: early (<10 metastases, each < 3mm) or advanced (>10 metastases, each >3 mm). Samples of liver and of metastases were taken from the 15 animals for quantification of iron concentrations by inductively coupled plasma mass spectrometry (ICP-MS). The data were analyzed using nonparametric tests; values of p < 0.05 were considered significant. RESULTS Five animals had early tumor development and five had advanced tumor development. In the GE sequences, early stage metastases showed homogeneous signal reduction attributable to the presence of magnetofluid. Spectrometry found significant differences between the iron concentration in rats with early stage metastases and controls (p=0.002) as well as between rats with early stage metastases and those with late stage metastases (p=0.001). The ratio of exogenous iron in metastases and in liver in early stage rats was 2.6:1. The concentration of exogenous iron in the liver was significantly different from that in tumors only in early stage animals (p=0.043). CONCLUSIONS MRI and spectrometry made it possible to evaluate the vascular distribution of magnetofluid in the liver and revealed the differences in its affinity for metastases in different stages of disease.