This technique is very similar to any other outpatient percutaneous surgical procedure. Appropriate imaging and appropriate labs must be obtained to make sure the patient is a candidate for this procedure.

Preparation
First, the patient has to be adequately evaluated for the type of problem he or she has, which in general is a tumor. Imaging studies such as Computed Tomography (CT), Magnetic Resonance Imaging (MRI), or ultrasound need to be obtained to identify the location of the area to be treated and to determine if the doctor can get to it safely with RFA. The patient must also be evaluated for major medical problems that could prevent him or her from undergoing the procedure. The patient has to have a relatively normal coagulation status and can not be on blood-thinning medications, in order to reduce the risk of bleeding. A history of heart problems or kidney problems does not necessarily mean the patient is not a candidate for RFA, but doctors must be aware of these conditions so they can take appropriate precautions as necessary.

Patients usually do not eat anything after midnight the night before the RFA procedure, although they do take routine medications with a small sip of water, with the exception of blood thinners. Blood thinners must be stopped befor the procedure in order to prevent excessive bleeding from the needle puncture. When the patient arrives, he or she is evaluated by either anesthesiology or radiology, depending on whether the patient will have general anesthesia or conscious sedation. The patient then undergoes the sedation process before the ablation.

Anesthesia
RFA can be done under conscious sedation or general anesthesia. Doctors decide which is best for an individual patient based on the size of the tumor, the expected time for the procedure, the number of placements to be utilized with the device, the patient’s tolerance of pain, and other considerations. At UAMS, we most often employ general anesthesia. The procedure itself is moderately painful. The patient is stuck with a very large needle, which is then heated. Patients do have some sensation of the heat involved, especially if the tumors are near areas with numerous nerve endings. For instance, if the tumor is close to a surface that tends to have a lot of nerve endings, like the capsule of the liver, it can be somewhat more painful than if it is deeper in the liver.

Procedure

A needle is inserted into tumor, and a probe is threaded through needle.

Wires (or tines) are deployed and tips are heated.

Heat energy travels along the tines, killing the surrounding tissue.

Heat spreads outward, killing tissue in the gaps between the tines.

A complete thermal lesion destroys all the cells in the target area.

RFA can also be done laparoscopically, most often by surgeons in the operating room as opposed to by interventional radiologists. A laparoscopy is when a very tiny incision is made for the physician to insert a minute camera inside the body to visualize the structures, rather than using external imaging techniques from outside the body. Sometimes laparoscopic RFA is used in conjunction with an interoperative ultrasound because with laparoscopy you can only see the surface of the organs, whereas most of the time you will be ablating tumors within the organ (e.g. the liver), so you will need some sort of imaging technique that can penetrate to see beneath the surface of the organ.

Once the patient is sedated, the interventional radiologist localizes (finds) the tumor area he wishes to destroy and threads the needle into the tumor under CT (or ultrasound) guidance, adjusting the needle to the right spot. A small, thin needle (localizing needle or guiding needle) is inserted first to ensure the physician can reach the tumor area safely with the appropriate pathway, and then the physician inserts a larger needle alongside the guiding needle. This larger needle is big enough to allow a probe to go through it. The probe is a little device with an array of wires, and when the physician deploys the probe, those wires unfold and deposit themselves throughout the tissue at the end of the needle.

The probe’s electrode is hooked to a radiofrequency generator, which creates a form of energy that is ultimately converted to heat in the body. By monitoring temperature or impedance (flow of electrical current around the probe), the doctor can determine how much energy is being transmitted into the tumor. Ultimately the energy is being deployed as heat, and the concept is to heat the cells to a temperature that is incompatible with cell life. Above a certain temperature, the metabolic processes and other processes coagulate and the cells cannot continue surviving, so they will die. Thus, essentially the doctor kills the unwanted cells with heat.

The probes come in different sizes so the physician can ablate different sizes of tumors; however, there is an upper limit to probe size because probes cannot deploy a very large array of wires and still conduct such intense energy in a focal manner. Frequently, the tumor is larger than any available probe, such that the physician must perform multiple ablations to destroy a single tumor. In that case, the physician deploys the probe in one area and ablates a small portion of the tumor, and then he repositions the probe to another area and does the ablation in that area, and so on, repeating the process until he kills the entire tumor.

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