EVALUATION OF PORTAL MR-ANGIOGRAPHY USING SUPERPARAMAGNETIC IRON-OXIDE

The purpose of our research was to determine the effects of superparam agnetic iron oxide on MR imaging of the portal venous system. Eight pi glets were examined in deep anaesthesia and respiratory arrest using a time-of-flight magnetic resonance fast low angle shot, two-dimensiona l angiography sequence at 1.5T. MR angiograms were acquired precontras t and after intravenous administration of a cumulative dose of 10, 20 and 40 mu mol/kg SHU 555A, a superparamagnetic iran oxide contrast age nt for MR imaging with a particle size of 60 nm, For each dose, two su bsequent sets of scans were obtained and reconstructed by a maximum-in tensity-projection algorithm. Hepatic parenchymal and portal venous si gnal intensities were measured, and portal vein contrast calculated fo r each set of scans. All examinations were visually rated as to portal vein contrast and homogeneity by two blinded observers. Receiver oper ating characteristics of both observers were analyzed. The contrast ag ent reduced hepatic parenchymal signal in a dose-dependent way. After a cumulative dose of 10 mu mol iron oxide, hepatic parenchymal signal intensity decreased to 63 +/- 6% (average of measurements at 4 and 14 minutes, mean +/- standard error of the mean), after 20 mu mol to 24 /- 3%, and after 40 mu mol to 12 +/- 1% of control. Intravascular sign al in the left main portal vein branch increased to 117 +/- 6%, 127 +/ - 10%, and 133 +/- 9% of control, respectively. The contrast-to-noise ratio of the portal vein improved (521 +/- 90%, 891 +/- 178%, and 995 +/- 201% of control in the left portal vein main branch). Intravascula r signal intensities increased slightly. The combined effect improved contrast of the portal vein stem and its branches. Receiver operating characteristics analysis documented dose-dependency of contrast medium effects on portal venous contrast and intravascular homogeneity. Visu al rating also indicated a positive effect on portal venous contrast. The superparamagnetic iron oxide agent improved portal venous contrast with surrounding hepatic parenchyma in this normal animal model, and could potentially result in more accurate diagnosis of portal venous p athology.