Effect of absorption of laser radiation by blood hemoglobin on threshold of destruction of pathological tissue during laser angioplasty

Conclusions1. Absorption by hemoglobin increases the threshold power density of laser radiation at the outlet of the light guide and, together with scattering of the radiation, determines the range of distances between the irradiated surface and the end of the light guide within which destruction of atherosclerotic formations (the range of working distances) can be obtained.2. For the purpose of laser angioplasty, it is advisable to use light-conducting systems with a numerical aperture of not more than 0.2 at the outlet.3. For an ionic argon laser (λ=0.488−0.514 μ) the range of working distances is limited to something of the order of 1 mm and is mainly determined by absorption of the radiation by hemoglobin. An increase of power causes virtually no change in this value.4. For a solid laser on Nd:YAG (λ=1.064 μ) the range of working distances is limited to something of the order of 1.5–2 mm, and is determined mainly by scattering of the radiation at the outlet of the light-conducting system.