Laser ablation of skull tissue using transverse excited 9.6-um CO2 lasers with pulse durations of 1-100 us

Nathaniel M. Fried; Daniel Fried

doi:10.1117/12.388033

13 June 2000 Laser ablation of skull tissue using transverse excited 9.6-μm CO₂ lasers with pulse durations of 1-100 μs

Nathaniel M. Fried, Daniel Fried

Proceedings Volume 3914, Laser-Tissue Interaction XI: Photochemical, Photothermal, and Photomechanical; (2000) https://doi.org/10.1117/12.388033
Event: BiOS 2000 The International Symposium on Biomedical Optics, 2000, San Jose, CA, United States

Abstract

Craniotomy using a drill and saw frequently results in fragmentation of the skull plate. Lasers have the potential to remove the skull plate intact. TE CO₂ lasers operating at the peak absorption wavelength of bone ((lambda) equals 9.6 micrometer) and with pulse durations of 5 - 10 microseconds, approximately the thermal relaxation time in hard tissue, produced high ablation rates and minimal peripheral thermal damage. Both thick (2 mm) and thin (250 micrometer) bovine skull samples were perforated and the ablation rates calculated. Results were compared with Q-switched and free- running Er:YAG lasers ((lambda) equals 2.94 micrometer, (tau) _p equals 150 ns and 150 microseconds). The CO₂ laser perforated thick sections at ablation rates of 10 - 15 micrometer per pulse and fluences of approximately 6 J/cm². There was no discernible thermal damage and no need for water irrigation during ablation. Pulse durations >= 20 microseconds resulted in significant tissue charring which increased with the pulse duration. Although the Er:YAG laser produced ablation rates of approximately 100 micrometer per pulse, fluences > 30 J/cm² were required to perforate thick samples, and thermal damage measured 25 - 40 micrometer. In summary, the novel 5 - 10 microsecond pulse length of the TE CO₂ laser is long enough to avoid a marked reduction in the ablation rate due to plasma formation and short enough to avoid peripheral thermal damage through thermal diffusion during the laser pulse. Further studies with the TE CO₂ laser are warranted for potential clinical application craniotomy procedures.

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Nathaniel M. Fried and Daniel Fried "Laser ablation of skull tissue using transverse excited 9.6-μm CO₂ lasers with pulse durations of 1-100 μs", Proc. SPIE 3914, Laser-Tissue Interaction XI: Photochemical, Photothermal, and Photomechanical, (13 June 2000); https://doi.org/10.1117/12.388033

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KEYWORDS

Laser ablation

Carbon dioxide lasers

Skull

Laser tissue interaction

Pulsed laser operation

Er:YAG lasers

Bone

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