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The purpose of this study was to evaluate the ability of the new liver-specific magnetic resonance contrast agent gadolinium-ethoxybenzyl-diethylenetriamine penta-acetic acid (Gd-EOB-DTPA) to detect hepatocellular carcinoma (HCC). Seventeen mice with 66 chemically induced HCCs underwent magnetic resonance imaging with both Gd-EOB-DTPA (30 mumol/kg) and superparamagnetic iron oxide (SPIO; 10 mumol/kg). After enhancement, lesion-to-liver contrast-to-noise ratios (CNRs) of 47 detected HCCs increased negatively from 3.7 +/- 10.7 (mean +/- SD) to -55.1 +/- 25.8 with Gd-EOB-DTPA (P < .001) and increased positively from 10.4 +/- 10.4 to 26.1 +/- 16.3 with SPIO (P < .001). The improvement of CNR after administration of SPIO was less in smaller lesions (< 4 mm), whereas that after administration of Gd-EOB-DTPA was independent of lesion size. However, Gd-EOB-DTPA positively enhanced four HCCs (8.5%), both highly differentiated (grade 1) and moderately differentiated (grade 2). Gd-EOB-DTPA allows the conspicuous detection of small HCCs; however, moderately differentiated HCCs occasionally may be positively enhanced.

To determine whether paradoxic uptake of gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) occurs only with highly differentiated hepatocellular carcinomas, quantitative image analysis was performed in 37 mice with 133 hepatocellular carcinomas. The results of lesion/ liver signal intensity measurement and relative enhancement calculation indicate that paradoxic positive enhancement occurs independently of cellular differentiation.

Apparent diffusion coefficients (ADCs) of tissue water were determined in chronic brain lesions of a rat stroke model, stroke-prone spontaneously hypertensive rats and compared with histology. ADCs increased in the order control < edema < gliosis < cyst. The differences between individual groups were statistically significant. The increase in ADC is thought to mainly reflect a relative increase in the extracellular space in brain tissue. ADC values may be a clinically useful parameter for tissue characterization.