Focal liver masses: Enhancement patterns on contrast-enhanced images - Concordance of US scans with CT scans and MR images

Purpose: To assess prospectively the concordance of enhancement patterns of focal liver masses on contrast material enhanced ultrasonographic (US) scans with patterns on contrast-enhanced computed tomographic (CT) scans or magnetic resonance (MR) images. Materials and Methods: This study was approved by the institutional review board; patients gave informed consent. Contrast-enhanced US and contrast-enhanced CT or MR imaging were performed in 135 patients (62 men, 73 women; mean age, 51 years) with 144 confirmed liver masses. Masses included 49 hepatocellular carcinomas, 13 metastases, 30 hemangiomas, 41 lesions of focal nodular hyperplasia, and 11 others. Randomized image sets from each modality were shown independently to three blinded readers, who answered identical questions about enhancement of the lesion and liver in the arterial and portal venous phases and changes with time. Concordance for modalities was calculated from answers of readers and consensus answers between readers, with 95% confidence intervals (CIs). The kappa values were calculated for interreader agreement. Results: Features of arterial phase enhancement showed concordance of more than 76% for modalities. The highest concordance of 92% (132 of 144), with 95% CI of 86% and 95% (kappa > 0.84), was for the presence of peripheral pools and centripetal progression. Concordance in the portal venous phase was lower, with agreement for predominant enhancement of the lesion in 61% (86 of 142), with 95% CI of 52% and 68% (kappa > 0.83). Portal venous phase washout occurred in 75% (106 of 142), with 95% CI of 67% and 81% (kappa > 0.81). The majority of discordances were for malignancies for which only US depicted no sustained enhancement in the portal venous phase. Conclusion: US shows high concordance with CT or MR imaging, especially for the arterial phase. Discordance in the portal venous phase may reflect the tendency of CT and MR contrast agents, unlike microbubbles, to diffuse into interstitium.