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Radiofrequency ablation of liver tumors


Medical editor Knut Brabrand MD
Radiologist
Oslo University Hospital

General

During radiofrequency ablation, the tumor is destroyed by radiofrequency energy. High-frequency alternating current (400,000 –1,250,000 Hz) is charged through the tumor via a needle electrode either by percutaneous, laparoscopic or open access, with the help of ultrasound guidance.

The needle consists of the outer part and one inner moveable part. When the inner part is pushed forward, multiple expanding metal rays come forward like an umbrella. The needle is isolated, except for the apical centimeter and the expanding rays. Current is applied to the needle from a generator. This produces high-frequency alternating current, which moves back and forth between the needle and 4 disc-shaped electrodes attached to both thighs of the patient.  When the generator is turned on, ionic agitation occurs in the tissue, as a result of the ions attempting to follow the directional changes caused by the alternating current. Frictional heat occurs close to the needle leading to necrosis of cells.  

It is assumed that all tumor tissue heated above 50–55 ºC for 5–10 minutes becomes necrotic.

Radiofrequency ablation is different from other types of tissue ablation in that the tissue around the needle warms up, not the needle itself.

Radiofrequency ablation is used as a supplement to liver resection or as primary treatment.

Indications

  • Liver tumors which are less than 4 cm in diameter.
  • Patients who either have too poor liver function or too poor general health.
  • Patients with liver metastases from colorectal cancer or neuroendocrine tumors where metastasis is limited in size and number.

Goal

  • Cure the disease
  • Palliation

Equipment

  • Radiofrequency generator
  • Electrode needles
  • Grounding pads on the patient

Preparation

  • The patient lies in the supine or lateral position.
  • The procedure is performed under general anesthesia.

Implementation

Radiofrequency ablation is carried out using ultrasound guidance either by percutaneous, laparoscopic, or open access.

  • 2 grounding pads are attached to each thigh and connected to the alternating current generator.
  • A small active needle electrode is inserted in the tumor.
  • The needle electrode is connected to the generator and establishes a circuit through the patient.
  • The alternating current leads to frictional heating of the tissue near the active electrode.
  • The liver tissue is heated twice for 5-10 minutes. The tumor and a small border of normal tissue are destroyed.
  • Ultrasound contrast is given to evaluate if the amount of necrotic tissue is adequate compared to the original tumor. About 1 cm margins of necrotic tissue around the tumor is the goal.

Follow-up

  • A few days of fever is normal due to breakdown products after tissue damage. If the fever occurs/lasts after the 3rd postoperative day, this may be due to an abscess (rare). 
  • A CT scan is performed the day after the ablation procedure to assure complete tumor destruction.

Follow-up

The patient should be seen 1 month after the procedure. The patient is followed-up every 3 months for 2 years and thereafter annually.


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