PROCEDURE
A needle electrode is advanced into the targeting tumors via either a percutaneous, laparoscopic, or open (operation) route. The needle electrode used most frequently is a 14-gauge, 15- to 25-cm long insulated cannula containing 10 individual hook-shaped electrode arms or tines. Upon deplopment, the array of tines extends out to a diameter of either 2.0, 3.0, or 3.5 cm. Using ultrasound or CT to guide placement, the needle electrode is advanced to the area of the tumor to be treated. Once the tines have been extended or deployed into the tissue, the needle electrode is attached to a RF generator and treatment is performed.
Tumors less than 3 cm in greatest diameter can be ablated with the placement of a needle electrode with an array diameter of 3.5 cm when the electrode is positioned in the center of the tumor. Tumor larger than 3 cm requires more than one deployment of needle electrode. Typically, the array is placed first at the interface of one side between the tumor and nondiseased parenchyma, and then the array is reposited and re-deployed on another side at 2.0- to 2.5 cm intervals within the tissue. To completely destroy cancerous tussue, the needle electrode is used produce a thermal lesion that incorporates not only the tumor, but also nondiseased tissue in a zone 1 cm wide surrounding the tumor.
CLINICAL APPLICATION
RF ablation has shown excellent results in treating primary liver tumors such as hepatoma or hepatocellular carcinoma, since these types of tumors tend to be slow-growing and encapsulated (enclosed within a capsule inside the liver).
It is especially useful for patients who are not ideal surgical candidates, cannot undergo surgery, have recurrent tumors or don't respond to conventional therapies.
The following types of cancers that originate in the liver are most likely to be successfully treated with RF ablation: