Selective Ablation of Atheromas Using a Flashlamp-Excited Dye Laser at 465 nm

Ablation of human atheromas with laser pulses that had only a small effect on normal artery tissue was shown in vitro in air and under saline using 1-μ sec pulses at 465 nm from a flashlamp-excited dye laser. At this wavelength, there is preferential absorption in atheromas due to carotenoids. The threshold fluence for ablation was 6.8 ± 2.0 J/cm2 for atheromas and 15.9 ± 2.2 J/cm2 for normal aorta tissue. At a fluence of 18 J/cm2 per pulse, the ablated mass per unit of energy ranged from 161 to 370 μ g/J for atheromas and from 50 to 74 μ g/J for normal aorta tissue. Ablation products consisted of cholesterol crystals, shredded collagen fibers, and small bits of calcific material. Most debris was less than 100 μ m in diameter, but a few pieces were as large as 300 μ m. High-speed photography of ablation in air suggested explosive ejection of debris, caused by vapor formation, at speeds on the scale of 300 m/sec. Histological analysis showed minimal thermal damage to residual tissue. These data indicate that selective laser ablation of atheromas is possible in vitro.