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KMID : 0377619760310030273
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Korean Jungang Medical Journal
1976 Volume.31 No. 3 p.273 ~ p.280
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Effect of the Radiofrequency on the Brain Tissue
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Abstract
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To destroy discrete, circumscribed, areas of nervous system in constant fashion is a prerequisite for stereotaxic surgery. Many methods including mechanical, cutting or crushing5), chemical destruction8)15), cooling20), radiation3)10) and ultrasound4)12)have been used but each, of above methods have some shortness to fulfill the prerequisite for stereotaxic surgery completely.
In 1960, Saul Aronow2) devised a radio frequency lesion generator which could make a discrete, predicted lesion in human nervous tissue. Recently, this is widely employed, in neurosurgery19) Radio frequency coagulation of tissue satisfactory for stereotaxic lesions occurs when the current passed is between frequencies of 0.2 MHz, and 4 MHz over a wide range of current values1). Most commonly a radio frequency of 2 MHz is employed. While the dimensions of the lesion are related to the power input, specifically temperature obtained, the current, and the duration of current, and other specific characteristics such as the geometry of the electrode and the character, of the tissue are also operative in determining the final result.
In general, the size of the lesion may be more reliably adjusted by changing the electrode than by substituting other parameters9). Within the range of frequencies just mentioned, only a minor portion. of the tissue destruction is due to resistive heating of the electrode and is dependent on the frequency. The major tissue destruction is the result of a frequency-dependent dielectric effect in the tissues when electric energy is converted into heat18). The most important factors appear to be the density and the ohmic resistency of the tissue.
Cerebral lesions dependent upon heat for their production are influenced by the presence of blood vessels, the spatial relationship to the cerebrospinal fluid pathways, and the tissue resistivity9). The greater vascularity of the gray matter and its greater ability to dissipate heat will require more power, than is, needed to produce a lesion of equal size in the white matter2,9,10)
The histologic examination of the lesions after radiofrequency coagulation in animal central nervous system was reported by Petty and Edsal17) and Sweet et al18) Carpenter. and Whittiers6) inserted magnetic wires into subcortical structures in the experimental animal and the head was placed in an electromagnetic field generated by a high-frequency induction heating unit. Resultant lesions were of uniform size and shape with a circular configuration and were unaccompanied by a distant intracerebral injury.
The present study is an attempt to evaluate histologic changes after radio frequency coagulation in the dog brain.
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