Ablation In Air Research Articles

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-mu 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 micrograms/J for atheromas and from 50 to 74 micrograms/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 micron in diameter, but a few pieces were as large as 300 micron. 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.

Investigation of photoablation of atherosclerotic plaques by laser radiation

A study was made of the mechanism and products of ablation of atherosclerotic plaques and arterial walls by laser radiation of wavelengths 308, 539, and 1078 nm at energy densities 0.5–8 J/cm2. Visible and infrared radiation were found to have a tissue damage threshold of 3–4 J/cm2 and the process was explosive involving ejection of large fragments. Ultraviolet radiation resulted in soft ablation of tissues throughout the investigated range of energy densities with the minimal effects on the underlying layers. The specific energy of ablation in air was 1.1 ± 0.3 kJ/g and the effective quantum yield of volatile products in vacuum was 0.8 ± 0.3. The quantum yield of lipids and their photoproducts was approximately the same at all the wavelengths and did not exceed 10−3. The results obtained confirmed the photochemical mechanism of ablation of tissues by XeCl laser radiation.