Frequency-doubled alexandrite laser for tissue differentiation in angioplasty

摘要

The Q-switched Alexandrite laser (750 nm/375 nm; 150 ns-2$mu@s) may be a solid-state alternative to excimer and pulsed dye lasers in laser angioplasty. The aim of this study was to determine whether laser induced fluorescence spectroscopy performed at 375 nm excitation could guide an Alexandrite laser angioplasty system. Thirty three segments of femoral arteries - classified as normal aorta, yellow fatty atheroma, and calcified plaque - were irradiated at a fluence of 0.2 J/cm$+2$/ and investigated spectroscopically in vitro. Calcified plaque and normal aortic LIF spectra showed a fluorescence peak at 450 nm, yellow fatty plaque spectra revealed an additional peak of equal or lower intensity at 520 nm. The ratio of the laser-induced fluorescence intensity at 465 nm and 530 nm was used to discriminate yellow fatty atheroma from normal artery wall. This fluorescence intensity ratio was 2.55$POM@0.25 for normal aorta, 2.35$POM@0.33 for calcified plaque, and 1.42$POM@0.27 for yellow fatty plaque, respectively. Using a discrimination threshold of 2.0, 95% of the yellow fatty plaque could be classified correctly. Thrombs showed no fluorescence signal. An Alexandrite laser system might allow the simultaneous ablation and identification of vascular tissue in laser angioplasty.