الفهرس 
Anatomy Of The LiverOnly 14 pages are availabe for public view
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Abstract
Hepatic tumors remain a difficult management challenge for all clinicians. In 2005, it was predicted that there would be more than 667,000 new cases of liver cancer throughout the world with more than 17,000 of the cases occurring in the United States alone, 25% of these patients will have underlying metastatic disease at the time of clinical presentation, with an additional 20-25% developing metastases within a 5-year interval . only (10-20%) of these patients with hepatic colorectal carcinoma (CRC) metastases will be candidates for liver resection. Many ablation modalities have been used, including cryoablation, ethanol ablation, laser ablation, and radiofrequency ablation (RFA). The most recent development has been the use of microwave (MW) energy in tumor ablation.
Radiofrequency ablation is the most frequently used of these methods. However, RF ablation is fundamentally restricted by the need to conduct electric energy into the body. As temperatures reach 100°C and boiling occurs, increased impedance limits further deposition of electricity into tissue. A number of different algorithms of energy deposition and several different types of electrodes are used to minimize this effect. Electrode types include multitined expandable electrodes, perfusion electrodes, and cooled-tip RF probes.
A further limitation of RF ablation is the relatively small zone of active heating created by ionic agitation.The majority of tissue heating is thus due to thermal conduction, which decreases exponentially away from the source, especially at tissue-vessel interfaces where flowing blood thermally protects perivascular tissue and tumor. The high rate of local recurrence is almost certainly caused in part by the heat-sink effect ).
Microwave ablation offers many of the advantages of RF ablation while possibly overcoming some of the limitations. Since MW ablation does not rely on conduction of electricity into tissue, it is not limited by charring. Therefore, temperatures greater than 100°C are readily achieved, which potentially results in a larger zone of ablation, faster treatment time, and more complete tumor kill. In addition, MW ablation has a much broader power field than does RF ablation—up to 2 cm in diameter. This may allow for larger zones of thermal ablation and a more uniform tumor kill. Because the cooling effect of blood flow is most pronounced within the zone of conductive rather than active heating, a larger power field may also enhance treatment of perivascular tissue.