Comparison of the Brain Tissue Response in Rats to Injury by Argon and Carbon Dioxide Lasers

Abstract

This study compares the acute and chronic response of brain tissue to injury by equal power density, focused argon (Ar) and carbon dioxide (CO2) laser beams. A cortical incision from 0.2-second laser pulses of 12.5 X 10(3) W/cm2 power density was made in the exposed cortex of 32 rats using either the CO2 or the Ar laser. The brains were examined at intervals from 1/2 hour to 1 month after injury. Histologically, all brain incisions were sharply demarcated hemispheroidal defects with a vaporized center bordered by a zone of coagulation necrosis surrounded by edema. The laser incisions were found to be of equal depth (less than 1 mm). The average cortical surface diameter of the CO2 laser incision was 0.86 mm for a focused beam spot size 0.45 mm in diameter, compared with 0.65 mm with the Ar laser, which had a focused beam spot size 0.15 mm in diameter. In both incisions, some delayed depth effect was observed. A progression of the tissue necrosis by approximately 17% was observed during the first 24 hours after injury. During the first 4 hours after injury, the Evans blue blood-brain barrier defect (EBBD) surrounding the cortical incisions averaged 5.80 mm2 for the CO2 incision and 0.888 mm2 for the Ar incision. In both types of brain incision, the EBBD appeared to resolve by 24 hours after injury. At 1 month after injury, a core of coagulation necrosis surrounded by mild fibrillary gliosis was observed. At the power density and focused beam spot sizes used, there was no significant difference in the overall brain tissue response to Ar and CO2 laser lesions.

Argon Laser Surgery of Pediatric Neural Neoplasms

“…Compared to the C 0 2 laser, the argon laser beam has a lower tissue absorption coefficient; but because of other variables (scattering, tissuetissue interfaces, pigments, subcellular particles), it produces a lesion of an almost identical size in neural tissue [1], The argon laser beam is highly absorbed by hemoglobin, and its laser-tissue interaction is significantly more hemostatic than is that of the C 0 2 laser.…”

Lasers in Pediatric Neurosurgery

“…The C 0 2 laser beam is absorbed in only a small amount oflissuc, allowing the surgeon to visualize the effects of the laser radiation. There is almost no spread of heat to the surrounding tis sue, facilitating an extremely gentle 'no-touch' technique [2,3],…”

“…The zone of injury surrounding the area o fC 0 2 laser and brain tissue interaction has been shown to be less than I mm in width under most circumstances [2,3], The reasons for this are twofold: there is little spread of heat because of the precisely focused laser beam; and heat is dissipated by the 'heat sink' effect of human tis sue. Blood flowing through tissue helps to dissipate heat rapidly.…”

“…The smaller spot size and de creased power make the argon laser less useful in debulking tumor tissue than the C 0 2 laser. The smaller spot size, however, allows for very precise destruction in vital areas [2].…”

Ablation of neural tissue by short-pulsed lasers ? a technical report

“…This leads to tissue heating resulting in tissue damage [4,10]. The histopathological appearance of lesions that have been induced by photothermal interaction of different lasers with neural tissue is described [2,3].…”