Radiofrequency ablation with the real-time virtual sonography system for treating hepatocellular carcinoma difficult to detect by ultrasonography

Abstract

Radiofrequency ablation has been applied to treat hepatocellular carcinoma, with favorable therapeutic outcomes. Nevertheless, practitioners have approached radiofrequency ablation with some reluctance due to the difficulty of identifying isoechoic tumors and recurrent tumors. The aim of the present study is to investigate the efficacy of Real-time Virtual Sonography to treat hepatocellular carcinoma difficult to detect by conventional ultrasonography. Real-time Virtual Sonography is a system generating multiplanar reconstruction images in real-time using the Hitachi medico EUB-8500 equipped with a probe. The system included following components: 1) digital imaging and communications in medicine (DICOM) data from dynamic CT, 2) a magnetic field generator to match the multiplanar reconstruction image on the monitor and the actual ultrasonography image, 3) the cross section with the tumor displayed as a multiplanar reconstruction image. Total twenty-five nodules of twenty-one patients underwent radiofrequency ablation monitored by Real-time Virtual Sonography. All nodules difficult to detect via conventional ultrasonography were clearly visualized in real-time. The average nodule diameter was 2.4 +/- 1.6 cm, and punctures and coagulation were performed an average of 2.2 and 3 times per session. Dynamic CT after session confirmed effective coagulation of each nodule. In conclusion, this study demonstrates that the present system is capable of effectively and accurately treating tumors difficult to detect by conventional ultrasonography.

Keywords: HCV; coagulation; dynamic CT; hepatic tumor; multiplanar reconstruction image.

Fig. 1

Summary of the Real-time Virtual Sonography system (Hitachi Medical, partially modified). Step 1: Using the xiphoid process as a reference point, match positional coordinates for positional synchronization. Step 2: Gather positional information from the magnetic sensor attached to the probe. Step 3: An MPR image matching the positional information from the probe is reconstructed based on CT volume data and displayed on the workstation monitor. A: Magnetic field generator. B: Magnetic sensor. C: Probe. D: Magnetic position detecting unit.

Fig. 2

Flow diagram of subjects enrollment. TACE, transarterial chemo-embolization; RFA, radiofrequency ablation; PEI, percutaneous ethanol injection.

Fig. 3

Images displayed on the workstation monitor. Moving images are displayed in real-time. Upper left: An MPR image reconstructed during scanning. Arrow head: Hepatocellular carcinoma detected by CTAP. Upper right: Actual ultrasound image. The hepatocellular carcinoma was isoechoic and difficult to detect. Lower: A reconstructed image of the trunk region based on CT volume data. The arrow indicates the location of probe scanning ascertained from positional information gathered by the magnetic sensor (arrow). The cross section of this area was reconstructed as an MPR image. MPR: multiplanar reconstruction, CTAP: CT during arterial portography.

Fig. 4

CT during arterial portography (CTAP) and CT during hepatic arteriography (CTHA) of pre-treatment and dynamic CT of post-treatment of HCC. A: CTAP. Area with a absence of portal flow is shown in segment 4 (arrow head). B: Early-phase CTHA. High hepatic arterial flow and enhanced hepatocellular carcinoma. C: Delayed-phase CTHA. Corona enhancement around the tumor. D: Tumor accurately coagulated under RVS guidance.