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Irreversible electroporation (IRE or NTIRE for ''non-thermal irreversible electroporation'') is a soft tissue ablation technique using ultra short but strong electrical fields to create permanent and hence lethal nanopores in the cell membrane, to disrupt the cellular homeostasis. The resulting cell death results from apoptosis and not necrosis as in all other thermal or radiation based ablation techniques. The main use of IRE lies in tumor ablation in regions where precision and conservation of the extracellular matrix, blood flow and nerves are of importance. The technique is in an experimental stage and has not been approved for use outside of clinical trials. == Mechanism == Utilizing ultra short pulsed but very strong electrical fields, micropores and nanopores are induced in the phospholipid bilayers which form the outer cell membranes. Two kinds of damage can occur: # Reversible electroporation (RE): Up to a certain degree of damage induced by nanoporation, the cell can be completely repaired and survive. This is called reversible electroporation or just electroporation. Medical applications are, for example, local introduction of intracellular cytotoxic pharmaceuticals such as bleomycin (electroporation and electrochemotherapy). # Irreversible electroporation (IRE): After a certain degree of damage to the cell membranes by electroporation, healthy and cancerous cells are irreversibly damaged. They die by apoptosis, which is unique to this ablation technique, in opposition to all other ablation systems which induce necrosis either by heat or radiation. It should be stated, that even though the ablation method is generally accepted to be apoptosis, some findings seem to contradict a pure apoptotic cell death, making the exact process by which IRE causes cell death unclear. The mechanism of IRE is not completely understood. The current theory is as follows: When an electrical field of more than 0.5 V/nm is applied to the resting trans-membrane potential, it is proposed that water enters the cell during this dielectric breakdown. Hydrophilic pores are formed. A molecular dynamics simulation by Tarek illustrates this proposed pore formation in two steps:〔 # after the application of an electrical field, water molecules line up in single file and penetrate the hydrophobic center of the bilayer lipid membrane; # these water channels continue to grow in length and diameter and expand into water-filled pores, at which point they are stabilized by the lipid head groups that move from the membrane-water interface to the middle of the bilayer. It is proposed that as the applied electrical field increases, the greater is the perturbation of the phospholipid head groups, which in turn increases the number of water filled pores. This entire process can occur within a few nanoseconds.〔 Average sizes of nanopores are likely cell-type specific. In swine livers, they average around 340-360 nm, as found using SEM.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Irreversible electroporation」の詳細全文を読む スポンサード リンク
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