Percutaneous radiofrequency ablation of sonographically unidentifiable liver tumors. Feasibility and usefulness of a novel guiding technique with an integrated system of computed tomography and sonographic images

The purpose of this study was to evaluate the safety and feasibility of a real-time integrated system with computed tomography (CT) and sonographic images for radiofrequency (RF) ablation of hepatic malignancies poorly defined on B-mode sonography, and to clarify the suitable phase of CT images for using this virtual sonography.Between September 2004 and December 2004, 12 patients with 16 hepatocellular carcinomas and two metastatic lesions arising from colorectal adenocarcinoma (n = 1) and rectal carcinoid (n = 1) were treated. The maximum diameter of nodules ranged from 1.0 to 2.5 cm (mean +/- SD; 1.5 +/- 0.6 cm) on CT images.Complete tumor necrosis was achieved in a single session in 19 lesions (90%), while a second session was required for the remaining two lesions (10%). Portal phase multi-planar reconstruction images were displayed under a suitable position corresponding to the ultrasound images in 9 patients (HCC = 7, metastasis = 2), and arterial phase multi-planar reconstruction images were displayed in the 3 remaining patients with hepatocellular carcinoma.Percutaneous RF ablation guidance using virtual sonography is an effective treatment for patients with hepatic malignancies. The portal phase of CT images may be the most suitable to indicate the 3-dimensional relationship between the liver vasculature and tumors on virtual sonography.