Mechanisms of laser-induced thermal coagulation of whole blood in vitro

T. Joshua Pfefer; Bernard Choi; Gracie Vargas; Karen M. McNally-Heintzelman; Ashley J. Welch

doi:10.1117/12.350970

22 June 1999 Mechanisms of laser-induced thermal coagulation of whole blood in vitro

T. Joshua Pfefer, Bernard Choi, Gracie Vargas, Karen M. McNally-Heintzelman, Ashley J. Welch

Proceedings Volume 3590, Lasers in Surgery: Advanced Characterization, Therapeutics, and Systems IX; (1999) https://doi.org/10.1117/12.350970
Event: BiOS '99 International Biomedical Optics Symposium, 1999, San Jose, CA, United States

Abstract

Quantitative data regarding photothermal and damage processes during pulsed laser irradiation of blood are necessary to achieve a better understanding of laser treatment of cutaneous vascular lesions and improve numerical models. In this study, multiple experimental techniques were employed to quantify the effects os single- pulse KTP laser (λ = 532 nm, τ_p= 10 ms) irradiation of whole blood in vitro: high-speed temperature measurement with a thermal camera in line-scan mode (8 kHz); optical coherence tomography; and transmission measurement with a co-aligned laser beam (λ=635 nm). Threshold radiant exposures for coagulation (4.4-5.0 J/cm²) and ablation (~ 12 J/cm²) were identified. Thermal camera measurements indicated threshold coagulation temperatures of 90-100°C, and peak temperatures of up to 145°C for sub-ablation radiant exposures. Significant changes in coagulum thickness and consistency, and a corresponding decrease in transmission, were observed with increasing radiant exposure. The Arrhenius equation was shown to produce accurate predictions of coagulation onset. The significant of dynamic effects such as evaporative loss and dynamic changes in optical properties was indicated. Implications for numerical modeling are discussed. Most importantly, the threshold temperatures typically quoted in the literature for pulsed laser coagulation (60-70 °C) and ablation (100 °C) of blood do not match the result of this study.

Citation Download Citation

T. Joshua Pfefer, Bernard Choi, Gracie Vargas, Karen M. McNally-Heintzelman, and Ashley J. Welch "Mechanisms of laser-induced thermal coagulation of whole blood in vitro", Proc. SPIE 3590, Lasers in Surgery: Advanced Characterization, Therapeutics, and Systems IX, (22 June 1999); https://doi.org/10.1117/12.350970

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