Detection of liver metastases with superparamagnetic iron oxide in 15 patients: results of MR imaging at 1.5 T.

The first clinical results of using superparamagnetic ferrite particles as a tissue-specific contrast agent for MR of the liver are reported at high fields (1.5 T). Fifteen patients with proved secondary liver malignancies were studied with plain and contrast-enhanced MR. Superparamagnetic iron oxide was administrated IV in a dose of 20 mumol/kg. Intermediate TR, 820/30, 60 (TR/TE), and long TR, 2200/22, 70, spin-echo sequences were used before and 1 hr after injection of contrast material. Before injection, the largest number of lesions (437) was detected with the T2-weighted sequence. Lesion-to-liver contrast, expressed as the difference between the tumor and liver signal-to-noise, improved after ferrite administration in both sequences from -1 to 20 and from 7 to 15 for the 820/30, 60 sequence and from 9 to 34 and 15 to 21 for the 2200/22, 70 sequence. Despite this significant improvement in terms of the number of lesions detected, contrast-enhanced images did not show significantly more metastases than the unenhanced T2-weighted images did (383, 421, 407, and 407 vs as many as 437, respectively). In this limited study at 1.5 T, the benefit of ferrite enhancement was only marginal when postcontrast images were compared with heavily T2-weighted precontrast scans.