DETECTION OF FOCAL LIVER-LESIONS WITH SUPERPARAMAGNETIC IRON-OXIDE - VALUE OF STIR AND SE IMAGING

Objective: We assessed the value of superparamagnetic iron oxide (SPIO ) particles on the detection of focal liver lesions by MRI. Materials and Methods: Twenty patients with one to five focal liver lesions, pri marily detected with ultrasonography and/or contrast-enhanced CT, were evaluated further with unenhanced and iron oxide-enhanced MRI at 1.0 T. Superparamagnetic iron oxide particles were administered intravenou sly as a slow infusion. Then T1-, T2-, and proton density-weighted SE images were obtained. In addition, the performance of a short TI inver sion recovery (STIR) sequence was evaluated. Results: The iron oxide c ontrast medium had marked effects on liver signal-to-noise (S/N) and t umor-to-liver contrast-to-noise (C/N) ratios but only minimal effects on tumor S/N ratios in cases of malignant tumor foci. Lesion-to-liver contrast, expressed as differences between the tumor and liver S/N rat ios, improved very significantly after SPIO infusion with all four pul se sequences. Contrast enhancement of the liver parenchyma was best in T2-weighted SE images, but the tumor-to-liver C/N values were highest with the postcontrast STIR sequence. The SPIO enhancement revealed a number of additional focal lesions (31%), also foci under 1 cm in diam eter. In three benign focal lesions, SPIO infusion produced a definite reduction in the S/N ratio of the lesions in contrast to the minimal change measured in malignant foci. The favorable performance of the ST IR sequence contradicts the disappointing results previously obtained at 0.6 T. Conclusion: Superparamagnetic iron oxide is a promising new contrast medium for MR examinations of the liver, increasing the consp icuity and reducing the detectability threshold of focal hepatic lesio ns.