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Image-guided Radiofrequency Ablation

Dr Ruchira Marwah, Senior Consultant and Chief, Department of Radiodiagnosis and Imaging, Umrao Hospitals, Mumbai on the myriad aspects of radiofrequency (RF) ablation and its varied advantages

Radiofrequency (RF) ablation is based on the principal of passing RF (˜500 kHz) electrical currents, through biological tissue, to achieve controlled heating of a specific location, with the highest power density [maximal specific absorption rate (SAR)] for a specific time, resulting in the death of unwanted tissue, by causing thermal coagulation necrosis.

The early beginnings of today's RF ablation stretch back to 1980s, when the concept of percutaneous treatment of cancer was first introduced by the modern day pioneers of interventional radiology. It started 30 years back by percutaneous injections of ethanol. Slowly, a number of alternatives have come into existence. Numerous minimally invasive ablative therapies available today are; radiofrequency ablation (RFA), microwave ablation, high intensity focussed ultrasound (HIFU), laser-induced interstitial thermotherapy (LITT), cryoablation and percutaneous ethanol injection. The most common ablative technique, currently in use, with the greatest numbers of procedures performed is RFA.

An important advantage of RF current (over previously used low frequency AC or pulses of DC) is that it does not directly stimulate nerves or heart muscle and can therefore, often be used, without the need for general anaesthetic. RFA has become increasingly accepted in the last 15 years with promising results.

Its main use has been in the treatment of cancers, leading to the addition of another weapon in the anticancer arsenal, attempting to cure cancer, reduce its size or relieve symptoms (palliative treatment). It can be given alone or in conjunction with other anticancer treatment. RFA may be used when surgery is not possible due to any reason, like associated co-morbid conditions, the tumour is difficult to reach or when the tumour is near an important body structure or a major blood vessel. It is also a viable and safe option for tumours that have not responded to chemotherapy or have recurred after being surgically removed. It aims at destroying cancer cells while preserving surrounding healthy cells. RFA is commonly performed to treat tumours in the lung, liver, kidney, bone, breast, thyroid, uterus and rarely in other body organs as well.

RFA can usually be administered as an out-patient procedure, that may at times require a brief hospital stay. RF ablation can be done under ultrasound guidance, CT guidance, fluoroscopy guidance, laparoscopy or by open method. Imaging helps to detect treatable lesions, guide the placement of the probe, and assess the effect of therapy. Most often, guided

Dr Ruchira Marwah
Sr. Consultant & Chief,
Dept. of Radiodiagnosis & Imaging,
Umrao Hospitals, Mumbai

by imaging techniques, the doctor, invariably an interventional radiologist, inserts a thin needle through the skin into the tumour. The ultrasound and CT scans help the doctor-guide the electrode into the right position and keep a close eye on what's happening inside the body during the treatment.

Whether a patient is a good candidate for RFA depends on several issues, such as the size and location of the tumour. RFA can be given with a local anaesthetic to numb the area and a sedative to make the patient drowsy. If a larger area needs to be treated, RFA is usually done under a general anaesthetic. How long the current will be applied, will depend on the size of the tumour. An area of healthy tissue around the tumour is usually also treated, as there may be cancer cells around the tumour that can't be seen. The treated tissue is not removed, but it slowly shrinks and heals over time.

High-frequency electrical energy delivered through this needle heats and destroys the tumour. Months after the procedure, dead cells turn into a harmless scar. RFA does not always manage to destroy all the cancer cells. Some patients may need to be treated more than once. RFA can be repeated if the tumour starts to grow again

The risk of complications with RFA is low. The main complications that can occur include bleeding from the site, infection, pneumothorax and damage to adjacent organs. Some of the side effects that may occur for a few days after RFA include pain or discomfort, feeling unwell with a raised temperature, blood in the urine after RFA to the kidney.

Follow up imaging is generally required. Computed tomography (CT) is used most frequently to determine whether the ablation is complete and to screen for early recurrences that may benefit from re-ablation.

In the context of managing various neoplasms, radiofrequency ablation has assumed varying roles. Radiofrequency ablation does not promise to cure cancer. Although this may be expected with some renal cell carcinomas and possibly non-small cell lung carcinomas, in patients with hepatocellular carcinoma radiofrequency ablation is in essence a bridge to a liver transplantation rather than a cure; and in patients with hepatic metastases, prolonging disease-free survival with a reasonable quality of life is the goal. RFA to date has been extremely successful in a short time in achieving these goals.

With every passing day, the scope of RFA is constantly increasing. The lesions that would not previously have been considered potential candidates for ablation are now being treated. In a short span of time, the spectrum of its clinical applications has expanded immensely. Due to its vast safety profile, today it is being used in cardiology, in the treatment of varicose veins and in pain management as well.

By selectively destroying nerves that carry pain impulses, the painful structure can be effectively denervated and the pain reduced or eliminated for anywhere from a few months to up to 12 months. There are a multitude of chronic pain conditions that respond well to this treatment. Chronic spinal pain, including spinal arthritis (spondylosis), post-traumatic pain (whiplash), pain after spine surgery, and other spinal pain conditions are those most commonly treated with RFA. Other conditions that are known to respond well to RFA include some neuropathic pain conditions like complex regional pain syndrome (CRPS or RSD), peripheral nerve entrapment syndromes, and other assorted chronic pain conditions. A patient's candidacy for RFA is usually determined by the performance of a diagnostic nerve block. This procedure will help to confirm whether a patient's pain improves just for the duration of the local anaesthetic (or not). Patients who have little to no pain relief after a diagnostic nerve block are not candidates for a neurodestructive procedure like RFA.

RFA provides safe and effective local treatment of some cancers, with very small complication rates and survival curves similar to surgery. Studies are still being conducted in this very dynamic modality to further expand the scope of clinical indications, in covering larger areas and having better long term results. An important area which needs special focus in this context is good patient selection, to be able to better identify those patients who will benefit from radiofrequency ablation and to show that the procedure has indeed benefited the patient. With the constantly expanding horizons of RFA, the future of radiofrequency ablation is 'today'.

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