LIVER-LESION TISSUE CONTRAST ON MR IMAGES - EFFECT OF IRON-OXIDE CONCENTRATION AND MAGNETIC-FIELD STRENGTH

This study assessed the enhancement of liver-lesion contrast by using low levels of iron oxide contrast agent at four common magnetic resonance (MR) imaging field strengths: 0.15, 0.35, 0.5, and 1.5 T. Adenocarcinomas were percutaneously inserted into the livers of 15 rats. Iron oxide was given intravenously in concentrations of 0 (control group), 2.5, 5, 10, and 20 μmol/kg to three rats in each concentration group. All images were acquired between 1 and 24 hours after injection. Liver-lesion contrast ratios and contrast-to-noise ratios (C/Ns) were calculated. Results showed increased liver-lesion contrast and C/Ns with increased iron oxide concentration up to 10-20 μmol/kg at all four magnetic field strengths. At 0.15 T, iron oxide produced lower gains in tumor-liver contrast. At middle and high magnetic field strengths, liver-lesion contrast was similar for each level of iron oxide concentration, but C/Ns were markedly higher at 1.5 T than at middle field strength. Low levels of iron oxide contrast agent are effective at magnetic field strengths of 0.35 T and above, producing the greatest increase in C/N at middle field strengths.