Purpose: Detection of a focal liver lesion which appears uncharacteristic at conventional ultrasonography (US) as first imaging modality, is a common situation. Subsequent contrast enhanced multi-phase spiral CT is an established and often used method to further characterize these lesions. The purpose of this study was to evaluate if contrast enhanced dynamic US is able to replace contrast enhanced multi-phase spiral CT in cases of uncharacteristic focal liver lesions at conventional US.
Methods and Materials: In a prospective study, 58 consecutive focal liver lesions (51 adult patients) with unspecific appearance at conventional US as first imaging modality, underwent additional contrast enhanced US and contrast enhanced CT to further characterize the lesions. To determine the dynamic contrast behavior US investigations were performed continuously for 5 minutes at a low mechanical index after a 2.4-4.8 ml SonoVue (Bracco, Italy BYK Gulden, Germany) bolus injection using high quality (1-6 MHz) curved transducers. CT exams were carried out in 4 phases (native, arterial, porto-venous, late) after a 120-150 ml Ultravist 370 (Schering, Berlin, Germany) bolus injection at a flow rate of 3-5 ml/sec using 4-row helical scanners (4 x 2.5 mm collimation, 5 mm image thickness, 5 mm reconstruction interval, 150-200 mAs). The results of the exams were categorized as being either confidently diagnostic, probably diagnostic, or uncharacteristic.
Results: The 58 focal liver lesions included the following entities: 23 hemangiomas, 10 focal nodular hyperplasias, 12 metastases, 5 primary malignancies of the liver, 4 inhomogeneous steatoses, 2 cysts, 2 malignant lymphomas. US was confidently diagnostic in 42 of 58 cases (72%), probably diagnostic in 8 of 58 cases (14%), and uncharacteristic in 8 of 58 cases (14%). CT was found to be confidently diagnostic in 33 of 58 cases (57%), probably diagnostic in 15 of 58 cases (26%), and uncharacteristic in 10 of 58 cases (17%). US and CT were of the same value concerning lesion characterization in 34 of 58 cases (59%), US was superior to CT in 15 of 58 cases (26%), and CT was superior to US in 9 of 58 cases (15%).
Conclusion: In the majority of uncharacteristic focal liver lesions at conventional US (72%) contrast enhanced US enables a definite diagnosis. In most cases contrast enhanced US is of the same value or superior to contrast enhanced CT (85%) in lesion characterization and can therefore in these cases replace subsequent CT.
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