Late-Phase Pulse-Inversion Sonography Using the Contrast Agent Levovist: Differentiation Between Benign and Malignant Focal Lesions of the Liver

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Abstract
OBJECTIVE. We assessed the ability of contrast-enhanced sonography to reveal differences between benign and malignant focal hepatic lesions. SUBJECTS AND METHODS. We examined 67 patients with focal hepatic lesions in a prospective study. The causes of the lesions were confirmed by histology, CT, MR imaging, or scintigraphy. The liver was screened for focal lesions using sonography. Thereafter, 2 g of Levovist (300 mg/mL; 1 mL/sec) was injected IV as a bolus. After a delay of at least 2.5 min without scanning, the liver was examined via three different scans using pulse-inversion sonography. RESULTS. For the discrimination of malignant versus benign liver lesions, contrast-enhanced sonography improved sensitivity from 85% to 100% and specificity from 30% to 63%, as compared with baseline sonography. Receiver operating characteristic analysis revealed a significant improvement in this discrimination (Az = 0.692 ± 0.065 at baseline sonography, Az = 0.947 ± 0.037 with contrast-enhanced sonography, p < 0.001). Furthermore, a lower interobserver variability was found for contrast-enhanced sonography (weighted κ = 0.947), as compared with baseline sonography (weighted κ = 0.469). All lesions that had homogeneous enhancement in the late phase of Levovist enhancement were benign. In distinction, 90% of lesions without contrast enhancement in the late phase were malignant. All lesions were malignant that were isoechoic (invisible) on baseline sonography but visible because of lack of enhancement after injection. CONCLUSION. Contrast-enhanced sonography has greater specificity and sensitivity than baseline sonography for the differentiation of benign and malignant liver lesions.