Microwave Ablation Therapy

What is Microwave Ablation?

Microwave ablation therapy is a medical procedure which uses microwave energy to kill cancerous cells in the body and to reduce the size of other tissues. It uses a minimally invasive process which requires the insertion of a single probe directly into the cells and this is imaged using an ultrasound.

It is similar in principle to the Radiofrequency Ablation Technique as it utilises heat energy to kill the cells of the tumour or tissue, however, it is a much more recent technique than RF ablation which displays a range of practical and safety benefits. This technique is most commonly used as a treatment for lung and liver cancers but it is also a therapy for patients who suffer from Menorrhagia in the uterus (Microwave Endometrial Ablation) [MW1] and an oversized prostate (Transurethral Urethral Microwave Therapy) [MW2].

An X-ray image of a Microwave Ablation Therapy on a cancerous lung cells. The single probe .Treatment was performed with 75 ohms, 1.4 amps, 150 W for a total of 5 minutes and a maximal temperature of 86°C [MW3].

How does it work?

Microwaves are produced using a magnetron in a generator box. These microwaves are then channelled through a special probe called a microwave antenna where they will enter the body.

The antenna is the only probe which enters the body and it is guided by ultrasound imaging to make sure it reaches the correct site of treatment.

Once the antenna is inserted into either the tumour or tissues it begins to transfer energy to these cells. The energy received by the cells causes a heating process by vibrating the water molecules present in the cell and they heat to temperatures between 60°C - 100°C where the tumours cells will die.

This heating process is contained to a small area of the tumour and will not spread due to the antenna’s shape and design. The ablation process only takes around 60 seconds when focused on a cell and so it is a relatively quick procedure. This is much quicker than radiofrequency ablation. [MW4].

Safety

The MWA Therapy is a low dose of energy at around 45 000 Joules which is equivalent to heating 54% of a cup of tea! This low energy means that the energy is non-ionising and so will only destroy the cells at which it is targeted.
Unlike Radio frequency ablation, this therapy does not rely on the flow of electrical current through human tissue. If an electrical current flows through the body, its nerve cells will be stimulated and pain will be experienced. Without this current, the treatment feels less painful. [MW3]

People who are able to undergo CT-scanning, are able to use this treatment.

Some side effects of this treatment may be experienced. Post-ablation Syndrome has been observed in patients between 1 day and 1 week after the therapy; this caused fever, nausea and in some cases anorexia.

Patients fitted with a pacemaker will have to be handled with care as these devices are sensitive to microwave frequencies.

Microwave Ablation Therapy applies an energy of around 45 kilojoules to the body. This energy is the equivalent of the energy required to heat 0.54 of one cup of tea.

Diagram of the Transurethral Microwave Therapy (TUMT) where the Microwaves are heating the enlarged prostate. Image Source(EAU Patient Information)