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The aim of the present study was to investigate a new, monomer-coated superparamagnetic contrast medium for magnetic resonance angiography. This was done by magnetic resonance imaging (MRI) and histologic examinations performed to characterize the contrast medium VSOP-C63 in the rat model. A total of 101 rats were examined to determine the optimal dose and the blood half-life as well as the distribution and degradation of the contrast medium in connection with a histopathologic evaluation.
The MRI results obtained with a high-resolution 3D FLASH sequence showed a prolonged intravascular signal increase for all dosages (15, 30, 45, 60, 75 and 90 mmol/kg body mass (BM)) tested in 36 rats. The observed signal increase allowed for even delineating small, second- and third-order vessels. Blood half-lives were found to be dose-dependant. Significant differences in signal increase among the dosages tested were observed for doses up to 75 mmol/kg BM. The dose of 90 mmol/kg BM produced an overdose effect which was superimposed on the signal-enhancing effect at the early time points. With a time-optimized acquisition technique, bolus injection of VSOP-C63 at a dose of 45 mmol/kg produces the same signal-enhancing effect in the aorta as the injection of 0.2 mmol Gd/kg (Magnevistý). This is due to the favorable R2-to-R1 ratio of VSOP-C63, which is 1.3 as determined at 37°C in 0.9% NaCl using a field strength of 0.47 T.