Classification of ultrasonographic images of small hepatocellular carcinoma using galactose-based contrast agent: relation between image patterns and histologic features.

Purpose: The aim of this study was to establish the relation between observed ultrasonographic (US) images produced with a galactose-based contrast agent and histologic characteristics of small hepatocellular carcinomas (HCCs).

Materials And Methods: A total of 64 nodules in 64 patients, 22 well differentiated and 42 moderately differentiated with a histologically proven HCC, smaller than 3.0 cm in diameter and who had undergone hepatectomy were consecutively examined by contrast-enhanced US using a galactose-based contrast agent. Perfusion images were acquired by intermittent high-intensity, harmonic power Doppler sonography using a high pulse-repetition frequency and high-pass filter setting. Perfusion images of the arterial and late phases were classified into several patterns and compared with the histologic findings obtained from resected specimens.

Results: Most of the well- and moderately differentiated resected HCCs showed hyperechoic change during the arterial phase. However, 13 (59%) of the well-differentiated HCCs showed isoechoic change and 27 (64%) of the moderately differentiated HCCs showed hypoechoic change during the late phase. The difference is statistically significant (P < 0.0001). In a comparison of microscopic portal invasion (vp) of HCCs using enhanced US patterns, both vp(-) and vp(+) groups showed a high incidence of the hypervascular pattern during the arterial phase; in contrast, during the late phase 11 (73%) of 15 vp(+) nodules showed hypoechoic change with spotty signals. This difference is statistically significant (P < 0.0001) when compared with a high incidence (52%) of signal defect in the vp(-) group. The existence of well-differentiated components associated with the periphery of moderately differentiated HCCs also correlated closely with patterns during the late phase (P < 0.01).

Conclusions: Late-phase contrast-enhanced US images of small HCCs with a galactose-based contrast agent are useful for predicting specific histologic characteristics.