Native and signal-enhanced power Doppler sonography for characterization of liver lesions

To evaluate the characterisation of liver lesions using power Doppler sonography before and after intravenous injection of the ultrasound contrast agent Levovist. 39 patients with 41 liver lesions (10 haemangiomas, 2 focal nodular hyperplasias (FNH), 2 focal fatty infiltrations, 1 echinococcal lesion, 11 hepatocellular carcinomas, 14 metastases and one cholangiocarcinoma) were evaluated prospectively. Power Doppler images before and after intravenous injection of the ultrasound contrast agent Levovist were analysed by two radiologists and one gastroeterologist, who subjectively classified the distribution (peripheral, central, diffuse) and amount (none, minimal, moderate and strong) of flow pattern in each sonographic examination. Histological verification was obtained in all liver lesions, except in haemangiomas, where MR imaging and in one FNH where scintigraphy was regarded as sufficient proof. On the whole, power Doppler sonography after contrast injection was superior to unenhanced power Doppler-sonography in 20 liver lesions and equal in 7. After contrast injection, previously visible flow was enhanced in 14 patients, in 6 lesions flow was detected, which was not seen before in the power mode. Moderate or strong flow signals were detected before contrast injection in 8/26, post contrast injection in 18/26 malignant tumours. Contrawise, 13/15 benign lesions did show any or only minimal flow signals before and 10/15 after contrast injection. Intratumoural flow signals favour a malignant tumour. The absence of flow signals is a frequent finding in benign lesions but does not rule out malignancy.