Effect of Dual-Wavelengh Laser on Soft Tissue

Objectives: Various laser systems with excellent hemostatic effect and coagulation ability have been used in laser surgery. Dual-wavelength lasers can be emitted simultaneously by prototyped laser device (Dual-Wavelength Laser Equipment with an Optical Parametric Oscillator). The purpose of the present study is to evaluate the incision performance and coagulation effect observed at the time of simultaneous dual-wavelength irradiation at 2.94 and 1.67 micrometer. Methods: The non-vital chicken pectoralis muscle flaps were used. Each sample was placed on a table and irradiated. The table was moved at 25 mm/min. The wavelength 2.94 micrometer at energy of 0, 20, 30, and 40 mJ was combined with the wavelength 1.67 micrometer at energy of 0, 10, 20, 30, and 40 mJ, to irradiate the samples with simultaneous dual-wavelength laser at 40 pps in the contact mode. During irradiation, surface temperature was measured in each sample. Following irradiation, the samples were histologically examined by staining with HE stain, Mallory stain, or phosphotungustic acid hematoxylin stain. The samples were also observed under polarizing microscopy. Results: In the group having a combination of the wavelengths 2.94 and 1.67 micrometer, a semicircular denatured zone was observed around the sharp incision margin. The denatured zone became thicker in proportion to the output energy of the wavelength 1.67 micrometer. Under the irradiation conditions used in the present study, the maximum thickness of denatured zone was 1.6 mm from the margin of incision, revealing that dual-wavelength laser has no influence on any deep area beyond the target coagulation site. Conclusion: Therefore, our results were suggested that simultaneous irradiation at wavelengths of 2.94 and 1.67 micrometer provides both soft tissue incision ability through irradiation at 2.94 micrometer and protein coagulation effect through the thermal effect of irradiation at 1.67 micrometer.