Radiofrequency thermal ablation of hepatocellular carcinomas

Abstract

Although surgical resection remains the best option as potentially curative therapy for hepatocellular carcinoma, radiofrequency thermal ablation has begun to receive much attention as an effective minimally invasive technique for the local control of unresectable malignant hepatic tumors. Most recent radiofrequency devices equipped with a powerful generator and larger needle electrode permit larger thermal lesions, up to 5 cm in diameter, with a single ablation. In this article, the author reviews the technical developments and early clinical results obtained with radiofrequency ablation techniques.

Fig. 1

Radiofrequency needle electrodes of varying design manufactured by three different companies. The first three needle electrodes, 15-gauge in external diameter and insulated except for 0.6-1 cm of their tip, have 4, 9, or 10 retractable hook-like prongs which serve as active electrodes during RF ablation. The fourth and fifth have a single 17-gauge straight-tip and triple-cluster electrodes, internally cooled with chilled saline solution during ablation. The needles have active exposed tips 2-4 cm in length

Fig. 2

HCC located in the mid-zone of the liver surrounded by normal hepatic tissue in a 62-year-old man. A. Transverse helical CT scan obtained during the hepatic arterial phase prior to RF ablation shows a 2.5-cm HCC (arrow), with homogenous contrast enhancement in liver segment 5. B. Transverse helical CT scan obtained one month after RF ablation depicts a round ablated area of low attenuation (arrows), representing complete necrosis of the tumor. Note that the ablated area covers the entire tumor and the cuff of surrounding normal hepatic tissue.

Fig. 3

HCC in a 45-year-old man. A. Longitudinal US scan of left hepatic lobe shows a 2.8-cm low echogenic HCC (arrows) which is fusiform in shape. The mass abuts on both liver capsules. Note the 3-cm active tip (arrowheads) of the straight cooled-tip electrode, which conforms to the shape of the mass. A single ablation lasted for 12 minutes. B. Portal-phase CT scan obtained 30 minutes after RF ablation reveals the presence of an oval low-attenuating lesion (arrows), with absence of contrast enhancement within the ablated area. This indicates complete necrosis.

Fig. 4

HCC in a 57-year-old man. A. Hepatic arterial-phase CT scan depicts a 4-cm HCC (arrows) in the subcapsular area of the right hepatic lobe, which shows an outward bulge. Using a 3-cm expandable needle electrode, four ablations were performed. The deep portion of the mass was treated first, and then the exophytic portion. B. Portal-phase CT scan obtained 13 months after RF ablation shows an ablated lesion (arrows) with no contrast enhancement, indicating complete necrosis.

Fig. 5

Hepatic arterial-phase CT scan obtained 1 month after RF ablation of a 4-cm HCC surrounded by large branches of the hepatic artery and portal vein shows a low attenuating ablated lesion (arrows) near the hepatic hilum. Although the tumor has become mostly necrotic, thin enhancing viable tumor (arrowheads) remains along the posterior branch of the right hepatic artery.

Fig. 6

Oblique US scan of the liver obtained during RF ablation shows an echogenic ablated lesion (arrows), the result of numerous microbubbles produced by thermal ablation.

Fig. 7

Hepatic arterial-phase CT scan obtained one month after RF ablation of a 4-cm HCC in the left hepatic lobe reveals the presence of a round low-attenuating lesion (arrows). Note the focal contrast enhancement (arrowhead) in the posterior aspect of the ablated lesion, indicative of viable untreated tumor. Additional RF ablation was subsequently performed.

Fig. 8

Reactive hyperemia revealed by immediate post-treatment CT. Hepatic arterial-phase CT scan obtained 30 minutes after RF ablation shows uniform rim-like contrast enhancement (arrows) around the ablated lesion, a phenomenon frequently occurring immediately after RF ablation and usually resolving prior to follow-up CT at one month.

Fig. 9

HCC in a 67-year-old woman. A. Hepatic arterial-phase CT scan shows an oval enhancing HCC (arrows), 4 cm in its greatest diameter, at the periphery of the right hepatic lobe. B. Unenhanced oblique power Doppler US scan obtained 18 hours after RF ablation shows a subtle flow signal (arrowhead) in the antero-superior aspect of the ablated lesion. C. Contrast-enhanced oblique power Doppler US scan obtained immediately after B, above, shows peripheral flow signals (arrows) within the anterior aspect of the RF-ablated lesion, representing residual tumor. The residual flow signals seen on this contrast-enhanced scan are better appreciated than on nonenhanced power Doppler US scan. D. Hepatic arterial-phase CT scan obtained 2 hours after RF ablation shows focal nodular contrast enhancement (arrowheads), indicative of residual tumor, in the anterior aspect of the ablated lesion (arrows). The enhanced area corresponds to that in which residual flow signals are present in the image described in C, above.