In microwave ablation, electromagnetic waves are sent into the tissue, just like in the microwave devices we use in our kitchens. These waves move the water molecules in the tissue in the form of waves (oscillation) and friction of these molecules creates heat at an average of 100-140 degrees. This heat, just like in radiofrequency, leads to tissue death in an area about 3cm in diameter around the needle. This area may be increased or decreased depending on the duration of ablation or the type and number of the needles used. In microwave ablation, electromagnetic waves are used instead of electricity, so there is no need to place electrodes on the patient's legs as in radiofrequency.
Microwave is a newer percutaneous ablation method than radiofrequency. In humans, its first use for tumor treatment took place in the 2000s. Microwave differs from RF ablation in two aspects: First, heat generation is faster and stronger, so the ablation is more rapid. Achieving high temperatures in a short time increases the intensity of ablation, but may also increase the complication rate in some critical locations. Second, the effectiveness of the ablation is not dependent on the conductivity of the tissue (as opposed to radiofrequency) because the electrical current is not used for ablation. Therefore, microwave ablation can be used more effectively than RF in relatively insulating tissues such as bone and lung.
The special needles placed in the tumor during microwave ablation are called "antennas". As in RF, there is a cold air or water circulation system in the needles that prevents carbonization. Due to this cooling system, microwave ablation is effective in a larger area, but because the shaft of the antenna remains cold, there are no problems such as burns at the puncture site on the skin.
Like radiofrequency, the microwave can also provide complete ablation in an area of approximately 3cm in diameter. There is no umbrella type needle in the microwave, only straight-shaped antennas are used. Some systems can expand the ablation area using up to three antennas simultaneously.
Microwave ablation, like radiofrequency, is most commonly used in liver tumors, especially in hepatocellular cancer (HCC) and liver metastases. Since it is not affected by the electrical conductivity of the tissue it is also a suitable ablation method in the lung and bone. In recent years, microwave have also been widely used in benign thyroid nodules.
Interventional oncology in cancer management
Prof Saim Yilmaz, MD