Thermal analysis of blood undergoing laser photocoagulation

• Published in: IEEE journal of selected topics in quantum electronics Vol. 7; no. 6; pp. 936 - 943
• Main Authors: Barton, J.K., Popok, D.P., Black, J.F.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-11-2001; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Absorption; Biomedical engineering; Blood; Coagulation; Computer simulation; Erythrocytes; Finite element method; Finite element methods; Irradiation; Laser pulses; Liquids; Mathematical models; Phase measurement; Polymers; Predictive models; Proteins; Reflectance; Reflection; Reflectivity; Refractive index; Refractivity; Temperature; Temperature measurement; Thermal measurements; Thermoanalysis
• ISSN: 1077-260X; 1558-4542
• DOI: 10.1109/2944.983297

The temperature of blood undergoing laser-induced photocoagulation during long-pulse (10 ms) 532 nm irradiation was measured in a time- and spatially-resolved manner using a novel technique. This method is based on the change in reflectivity of a solid-liquid interface given a dynamically changing refractive index in the liquid phase. In our case, the temperature-dependent change in the refractive index of blood was utilized, and the reflectivity at a glass-blood interface was measured. Measurements were compared to predictions from a finite-element model incorporating the effects of time-dependent changes in the absorption coefficients of the blood, and phase changes representing coagulation and the liquid/vapor transition. Previous studies have linked the onset of blood coagulation to a sharp rise in the 532-nm reflectance of the blood. Based on the thermal measurements and the results of an Arrhenius analysis, we postulate that the reflectance rise is a combination of protein denaturation and red blood cell conformal changes.