Ultrasound fusion imaging of hepatocellular carcinoma: a review of current evidence.

With advances in technology, imaging techniques that entail fusion of sonography and CT or MRI have been introduced in clinical practice. Ultrasound fusion imaging provides CT or MRI cross-sectional multiplanar images that correspond to the sonographic images, and fusion imaging of B-mode sonography and CT or MRI can be displayed simultaneously and in real time according to the angle of the transducer. Ultrasound fusion imaging helps us understand the three-dimensional relationship between the liver vasculature and tumors, and can detect small liver tumors with poor conspicuity. This fusion imaging is attracting the attention of operators who perform radiofrequency ablation (RFA) for the treatment of hepatic malignancies because this real-time, multimodality comparison can increase monitoring and targeting confidence during the procedure. When RFA with fusion imaging was performed on small hepatocellular carcinomas (HCCs) with poor conspicuity, it was reported that the rates of technical success and local tumor progression were 94.4-100% and 0-8.3%. However, there have been no studies comparing fusion imaging guidance and contrast-enhanced sonography, CT or MRI guidance in ablation. Fusion imaging-guided RFA has proved to be effective for HCCs that are poorly defined on not only conventional B-mode sonography but also contrast-enhanced sonography. In addition, fusion imaging could be useful to assess the treatment response of RFA because of three-dimensional information. Here, we give an overview of the current status of ultrasound fusion imaging for clinical application in the liver.