Thermally induced optical property changes in myocardium at 1.06 μm

✍ Scribed by Garrett J. Derbyshire; Daniel K. Bogen; Michael Unger

• Publisher: John Wiley and Sons
• Year: 1990
• Tongue: English
• Weight: 590 KB
• Volume: 10
• Category: Article
• ISSN: 0196-8092
• DOI: 10.1002/lsm.1900100108

✦ Synopsis

Light in the visible and near-infrared region is diffusely scattered in tissues by macromolecules. It was therefore hypothesized that tissue coagulation caused by high-power continuous wave laser irradiation might significantly alter tissue optical properties, resulting in a redistribution of laser energy during the laser ablation process. Infrared transmittance studies confirmed the hypothesis by demonstrating an irreversible decrease in light transmittance (45%) during heating of a 0.75 mm thick slice of tissue. Absorption and scattering coefficients were then determined from transmittance and reflectance measurements on thin slices of raw and coagulated myocardium irradiated with a Nd: YAG laser (1.06 pm). The scattering coefficient was found to increase fourfold (0.427 mm-' + 1.74 mm-') during tissue coagulation, while the absorption coefficient remained relatively unchanged (0.044 mm-' .+ 0.051 mm-'1. Calculations indicate that the coagulation-induced changes in tissue optical properties substantially increase surface back-scattering and reduce tissue penetration.