This is the principle setting. A generator establishes the high frequency power, which is then passed through a special needle into the tumor. A grounding pad closes the electric circuit.

The current causes the ions (charged atoms in tissues) to vibrate at very high speeds. The ions move back and forth so rapidly that they create friction, which produces heat. Heat is a very effective means of killing tissue. As tissue temperature rises above 45° C (113° F), protein is permanently damaged and cell membranes fuse.

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The process is rapid, requiring less than 15 minutes exposure time.

Thermosensors at the tip of the needle measures the temperature during the delivery of energy and after one ablation. In this example, the 4 needle tips were pushed back in the tissue after the ablation (the jump at 10.2 minutes). Without delivering energy, the thermosensores then show the temperature in the dead tissue.

As tissue is heated, dissolved gases (primarily nitrogen) are released from cells forming micro-bubbles within the tissue. These microbubbles are visible by ultrasound as a hyperechoic (bright) image allowing visual confirmation of the ablated area.

Ablation Zone:
Due to the extensive blood surgery of the liver, heat is dissipated very effectively. Therefore, at the periphery (outside) of the "Ablation Zone," the heat delivered from the needle is rapidly absorbed by the cooling effect of flowing blood through the liver; cell damage ceases at this specfic distance from the needle, which correlates closely to the extended dimension or diameter of the prongs.

As you can see in the picture to the left, there is a sharp boundary between the killed tumor and unaffected surrounding tissue. Thus liver tumors can be ablated without much sacrifice of surrounding normal liver tissue. However, to kill the tumor completely, we ablate a small rim of healthy tissue around the lesion.

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After the operation, tumors are controlled by sequential CT scans. A successfully ablated lesion shows an increased volume in the first week. After three months the ablated lesion shrinks in size and sometimes are completely absorbed, disappearing completely on CT scans. Other times, a residual cystic cavity remains..
An immunologic reaction and the liquidation of the dead tumor cells through macrophages (large cells that digest dead tissue) accounts for these changes.