Prediction of the ablation effect of ultrapulsed CO2 laser systems in clinical procedures

Matthijs C. M. Grimbergen; Rudolf M. Verdaasdonck; Christiaan F. P. van Swol

doi:10.1117/12.275485

16 June 1997 Prediction of the ablation effect of ultrapulsed CO2 laser systems in clinical procedures

Matthijs C. M. Grimbergen, Rudolf M. Verdaasdonck, Christiaan F. P. van Swol

Proceedings Volume 2975, Laser-Tissue Interaction VIII; (1997) https://doi.org/10.1117/12.275485
Event: BiOS '97, Part of Photonics West, 1997, San Jose, CA, United States

Abstract

Despite the superficial penetration of the light, the continuous wave (cw) CO₂ laser may induce a relatively large area of thermal damage in tissue next to the ablation crater. Ultra-pulsed laser systems, however, deliver pulse energies above the ablation threshold for tissue within a few hundred microsecond(s) , which instantly vaporize tissue. Since cw ablation models cannot be applied on pulsed ablation, a new model is introduced which is validated experimentally on phantom tissue. It discriminates between the cross section of the laser beam above the ablation threshold and the flanks of beam below threshold inducing thermal effects. Depending on pulse energy and beam diameter, the shape of the ablation crater in the tissue was calculated and validated experimentally in phantom tissue using a pulsed CO₂ laser and an Erbium laser. The diameter of the spot varied from 0.1 to 2.5 mm and the pulse energy from 25 to 250 mJ, 10-100 mJ. In the experimental crater depths up to 40 mm could be obtained in one pulse. The theoretical model agreed within 10 to 50 percent with the experimental data for spot sizes form 0.5 to 0.1 mm for the CO₂ laser. Although, the thermal effect of these pulses are minimal compared to cw lasers, the sub-threshold part of the laser beam can contribute to undesired thermal damage when repetitive pulses are applied within the thermal relaxation time. The model can serve as a good tool for predicting the depth of ablation for current clinical applications in dermatology, ENT and cardiac-surgery.

Citation Download Citation

Matthijs C. M. Grimbergen, Rudolf M. Verdaasdonck, and Christiaan F. P. van Swol "Prediction of the ablation effect of ultrapulsed CO2 laser systems in clinical procedures", Proc. SPIE 2975, Laser-Tissue Interaction VIII, (16 June 1997); https://doi.org/10.1117/12.275485

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