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[Benign hepatic tumors: MRI features before and after administration of superparamagnetic contrast media].

PURPOSE
To assess the yield of superparamagnetic iron oxide (SPIO)-enhanced MR images in the detection and characterization of benign hepatic tumors and to evaluate the potential role and safety of SPIO administration in the diagnosis of these tumors.


MATERIAL AND METHODS
Eighteen patients underwent MRI before and after administration of SPIO particles. Spin echo (SE) T1, DP, T2 and Gradient echo (GE) T2* images were acquired with a.5 T superconductive unit. MR diagnosis was bioptically proved in 12 patients. In the remaining six patients, who had hemangiomas only, diagnosis was confirmed by at least two imaging techniques-such as MR, CT, ultrasonography, radio-labeled red cells scintigraphy-and by both clinical and imaging follow-up.


RESULTS
Thirthy-four tumors were detected on the MR images: 29/34 (85,3%) before and 33/34 (97%) after SPIO administration - 6 focal nodular hyperplasias (FNH), 6 adenomas and 22 hemangiomas. One small tumor (adenoma) was detected on the unenhanced MR images only, while 4 lesions (3 adenomas, 1 FNH) were detected after SPIO administration only.


DISCUSSION
SPIO-enhanced MRI increased the detection rate of benign hepatic tumors compared to non-enhanced MRI. Iron oxide was also useful in the characterization of such lesions as it was able to demonstrate any heterogeneity resulting from the presence of central scars or septa. Nevertheless, in our experience it was useful to compare baseline with SPIO-enhanced MRI, even if time consuming. Indeed the uptake of iron oxide particles by well-differentiated lesions and normal hepatic parenchyma, is comparable, so that well-differentiated lesions appear isointense and therefore undetectable.


CONCLUSIONS
In our experience, although numerically limited, SPIO-enhanced MRI was clinically safe and more effective than non-enhanced MRI in both the detection and characterization of benign hepatic tumors, providing useful clues for diagnosis.