Simultaneous irradiation and imaging of blood vessels during pulsed laser delivery

Background and Objective: Simultaneous irradiation and viewing of 10-120 mu m cutaneous blood vessels were performed to investigate the effects of 2-m u s 577-nm dye laser pulses. Study Design/Materials and Methods: A modified scanning laser confocal micr oscope recorded vessel response to different radiant exposures (J/cm(2)). P robit analysis determined the 50% probability ("threshold") radiant exposur e necessary to cause embolized or partly occluding coagula, coagula causing complete blood flow stoppage, and hemorrhage. Results: A statistically significant difference in the threshold radiant ex posure existed for each damage category for blood vessels 10-30 mu m in dia meter, but not for larger vessels. For vessels over 60 mu m, complete flow stoppage was unattainable; increasing laser pulse energy produced hemorrhag e. In larger vessels, coagula often were attached to the superficial vessel wall while blood flowed underneath. Monte Carlo optical and finite differe nce thermal modeling confirmed experimental results. Conclusion: These results provide insight into the role of pulse duration a nd vessel diameter in the outcome of pulsed dye laser irradiation. (C) 1999 Wiley-Liss, Inc.