Radiofrequency ablation is the most widely used method of percutaneous tumorablation. It has been predominantly used to destroy tumors of the liver, withgood results. Current research indicates that RFA treatment of small primarytumors of the liver is as effective as surgical resection. Some investigatorsrecommend using RFA as a first line of treatment for liver tumors. In addition,RFA is being used to shrink or destroy tumors of the lung, kidney, breast, andadrenal glands.

How RFA Works
A needle electrode with an insulated shaft and uninsulated tip is inserted underthe skin and guided to the tumor, using ultrasound or CT imaging. Some arraysexpand, like an umbrella, after they are positioned.

When the needle electrode is in the correct position, a generator causes radiowaves to be emitted from the tip. The radio waves make the molecules in thetissue around the tip vibrate, causing friction that heats and kills thediseased tissue. That effect is localized; healthy tissue farther from theneedle electrode is not destroyed. Depending on the size of the tumor, theneedle electrode may be moved and the process repeated until all of the diseasedtissue is destroyed. The dead tissue does not need to be removed surgically—itwill shrink and gradually be absorbed by the body and replaced with scar tissue.

RFA can be performed under general or local anesthesia and can often be anoutpatient procedure. Patients should be able to resume normal activity within aday or two.

RFA Equipment
• Generator and grounding pads
The patient's body is made into an electrical circuit. A generator produces theenergy that causes the heat, while grounding pads on the patient's body completethe circuit, allowing the needle electrode to destroy the tumor.

current flow chart
Chart illustrates the flow of current during the RFA procedure. (Provided by Valleylab)

• Imaging
Ultrasound is the most popular imaging method for guiding the needle electrodeinto the tumor in liver tumor ablation, the most common use of RFA. CT is thesecond most frequently used technique, followed by MRI.

• Needle electrode
Most RFA treatments use a 14 to 17.5-gauge needle that comprises an insultedshaft and an uninsulated tip. Some RFA needles have umbrella-like prongs thatextend from the tip after the needle electrode is placed, penetrating a greaterarea of the tumor. Some needles are also water- or saline-cooled, which allowsfor more even heating and reduces the risk of charring the tissue. Finally, somenew apparatuses contain multiple needles on one array, allowing physicians totreat a larger volume of tissue in one session.

RFA three needle electrode
A cluster of three needle electrodes can be used to ablate a larger volume of tissue than a single needle electrode. (Provided by Valleylab)

The Procedure
• Patients may be given a local or general sedative.
• Grounding pads are placed near the insertion site.
• The tumor is located with imaging, and the needle electrode is guided into thetumor.
• A generator activates the array, causing the needle electrode to emit radiowaves that cause molecular agitation. The friction generated from the agitationheats the tissue.
• The heat must reach at least 50 degrees C.
• The destruction process may take between 10 and 60 minutes.
• If necessary, the needle electrode is relocated to treat another tumor oranother area of the same tumor. Most researchers recommend treating no more thanthree tumors in one session.
• After the treatment, the needle electrode is withdrawn and the insertion siteis bandaged. • The tumor will not be removed—the dead tissue will shrink overtime and be absorbed into the body and replaced with scar tissue.
• Follow-up imaging monitors that process and reveals any recurrence at thesite.

Pros of RFA
• Fast, inexpensive, and effective
• Most widely studied form of tumor ablation
• Reduced risk of bleeding, as the method cauterizes blood vessels as itdestroys the tumor
• Can be performed multiple times without major risk
• Can be used to treat patients who are not eligible for surgery
• As effective as surgical resection for eliminating some tumors
• Can treat tumors up to 3 cm in size
• Can treat up to three tumors per organ

Cons of RFA
• The "heat sink effect": Tumors near major blood vessels may not be properlytreated because the relatively cool blood transports the heat away from thetreatment area.
• Imaging and monitoring during the procedure can be difficult: As the tumorheats, vapor is released, which obscures the image.
• Tumors may be located near structures or nerves that are vulnerable to heatdamage.
• RFA cannot completely treat tumors larger than 3 cm.
• RFA is less successful in treating more than three tumors per organ.
• Charring is a risk: RFA is a conductive heat method, so some tissue may heattoo quickly, causing water in the tissue to vaporize. The water is needed toconduct energy into the tumor, and without it there is a risk that tissue withina tumor will be left untreated.