Characterization of liver hemangiomas with pulse inversion harmonic imaging

The purpose of this study was to determine if pulse inversion harmonic imaging (PIHI) can characterize liver hemangiomas. We retrospectively evaluated 39 consecutive patients with liver hemangiomas, 20 typical on conventional US (hyperechoic, homogeneous, or slightly inhomogeneous and with sharp margins) and 19 atypical (11 inhomogeneous with different echogenicity larger than 3 cm, 6 hypoechoic, and 2 isoechoic smaller than 3 cm). Each liver hemangioma was firstly evaluated by PIHI and then confirmed by dynamic helical CT (28 patients) or by 6 months of US follow-up (11 patients). The PIHI was performed by two distinct sweeps on a marker lesion, 30 s (vascular phase) and from 3 to 5 min (late phase) after bolus injection of Levovist (2.5 g, 300 mg/ml). Scans were digitally stored and reviewed using a dedicated software. Contrast enhancement features of marker lesion were subjectively evaluated. Typical hemangiomas on conventional US revealed on PIHI a characteristic rim-like or peripheral globular enhancement on 30-s scan in 4 of 20 cases (20%) and a characteristic isoechoic pattern on late phase in 16 of 20 cases (80%). On PIHI, all (11 of 11) atypical hemangiomas larger than 3 cm and 4 of 8 atypical liver hemangiomas smaller than 3 cm revealed a characteristic rim-like or peripheral globular enhancement on vascular phase with a characteristic centripetal fill-in on late phase. In 4 of 8 atypical liver hemangiomas smaller than 3 cm no characteristic pattern was revealed by PIHI. Pulse inversion harmonic imaging revealed a typical pattern in the majority of liver hemangiomas typical and atypical on conventional US. In few liver hemangiomas atypical on conventional US PIHI did not identify a characteristic pattern and helical CT was necessary for final characterization.