@article{viator99c, author = {J. A. Viator and S. A. Prahl}, title = {Laser Thrombolysis Using Long Pulse Frequency-Doubled {Nd:YAG} Lasers}, journal = {Lasers in Surgery and Medicine}, volume = {25}, pages = {379--388}, year = {1999}, abstract = {\textit{Background and Objective}: Laser thrombolysis is a means for clearing blood clots in occluded arteries. Many researchers have studied the mechanisms of clot ablation and research clinicians have used the technique to treat myocardial infarction using a number of different laser systems. Specifically, a 1\,$\mu$s pulsed dye laser has been used clinically to remove blood clots in coronary arteries. As a comparative study, the ablation characteristics of lasers with pulse durations in the ranges 50--150\,$\mu$s and 2--10\,ms are investigated. Two frequency-doubled Nd:YAG lasers at 532\,nm were used in this study. Ablation threshold and ablation efficiency of gel phantoms and thrombus using these two lasers were measured and compared to the results of the pulsed dye laser. The pulsed dye laser in this study operated at 522\,nm. \vskip2mm \textit{Study Design/Materials and Methods}: Gelatin samples with 150 cm$^{-1}$ absorption coefficient at 532\,nm and animal clot were confined to 3\,mm silicone tubes to measure ablation parameters. Additional samples with 150 cm$^{-1}$ absorption coefficient at 522\,nm were prepared for use with the pulsed dye laser. A fluorescence technique and photographic bubble detection were used to determine ablation threshold. A spectrophotometric technique was used to determine ablation efficiency. \vskip2mm \textit{Results}: The ablation threshold of the gel phantoms for all three lasers was determined to be 17$\pm$2\,mJ/mm$^2$. Ablation efficiency for the gel phantoms was 1.7$\pm$0.1\,$\mu$g/mJ. Clot had an ablation efficiency of 2.9$\pm$1.0\,$\mu$g/mJ. \vskip2mm \textit{Conclusions}: Ablation threshold and efficiency are independent of laser pulse duration for 1\,$\mu$s, 50--150\,$\mu$s, and 2--10\,ms pulses (p$<$0.05).}, }