Brain ablation in the rat cerebral cortex using a tunable-free electron laser.
BACKGROUND AND OBJECTIVES: We used the MARK III free electron laser (FEL) tuned to molecular vibrational absorbance maxima in the infrared (IR) wavelength range of 3.0-6.45 microm to study the effect of these various wavelengths and a power level of 5 mJ/2 microseconds macropulse on photoablation of CNS tissue. STUDY DESIGN/MATERIALS AND METHODS: Laser lesions were produced in the parietal cortex of anesthetized rats using thermal confined mid-IR (infrared) laser pulses tuned to the -OH, -CH, amide 1, and amide 2 absorbance bands. Histological assessments following recovery periods of 4 hours, 4 days, and 3 weeks were performed to determine the size, shape, and character of the photoablative lesions. Cell density studies were done in adjacent edematous tissue. RESULTS: Significant differences in lesion size and shape were observed as a function of wavelength. Although maximum ablation and collateral damage seemed to coincide with spectral peaks in the mid-IR, area and depth/width ratios did not. CONCLUSIONS: It was found in these experiments that wavelengths in the mid-IR could be selected for optimal ablative properties. Using tunable, high-peak-power pulsed lasers, it will be possible to produce well-defined photoablative lesions that conform to small, irregularly shaped neurosurgical targets.
Ovelmen-Levitt, J; Straub, KD; Hauger, S; Szarmes, E; Madey, J; Pearlstein, RD; Nashold, BS
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