Usefulness of power doppler ultrasound for evaluating vascularity of hepatocellular carcinoma

The development of ultrasound equipment employing color Doppler energy (CDE) has allowed recent progress in the detectability of blood flow in hepatocellular carcinoma (HCC). We evaluated the detectability and reliability of CDE in the imaging diagnosis of vascularity in HCC by comparing its images with those obtained with ultrasonography using color Dopplerfl velocity (CDV), computed tomography using helical scanning (helical CT), ultrasound angiography using CO₂ microbubbles (USAG), and other imaging modalities in 120 nodular-type HCCs. To measure detectability, we compared rate of detection of blood flow signals in CDE and CDV. To evaluate reliability, we analyzed the overlap ratio of detection of vascularity in HCC by imaging diagnosis based on CDE, helical CT, and USAG. We used the Acuson 128 XP/10 ART System (Acuson Corporation: Mountain View, CA) with 4.0 MHz vecta probes and 5.0 MHz convex probes for the CDE evaluation. When CDE and CDV were compared, CDE detected blood flow signals in 95 (79%) HCCs; CDV, in 83 (69%) HCCs. CDE detected blood flow signals in only 30 (57%) of 53 HCCs that were less than 2 cm in diameter, while CDV detected blood flow signals in only 20 (38%). To compare CDE, helical CT, and USAG, we divided HCCs into two groups according to detection of blood flow signals by CDE: HCCs in which CDE detected blood flow signals (group A, n = 93) and HCCs in which CDE did not detect blood flow signals (group B, n = 18). Evaluation with helical CT showed hypervascularity in 90 (96.8%) of the HCCs in group A and in 10 (55.5%) of the HCCs in group B; the overlap ratio was 88%. The overlap ratio between CDE and USAG was 90% when evaluated by USAG. The result of comparison between CDE and CDV suggested the superiority of CDE over CDV in the detectability of blood flow signals of HCC. Comparison of CDE, helical CT, and USAG suggested that CDE imaging can reliability diagnose HCC. Blood flow signals were hard to evaluate in some HCCs in deep locations, because of attenuation of the sonic beam and, in the case of HCCs located in the left lobe of the liver, because of the motion of artifacts. These two areas that warrant further study.