Comparison of Various Methods to Enhance Laser Photon Density in Soft Tissue: Tissue Temperature, Laser Pulse Modulation, Glycerol, and Their Combination

摘要

Recently, tissue optical clearing (TOC) has been considered as a useful tool in low level laser therapy due to the enhancement of photon density in deep tissue layer. In this study, glycerol injection, tissue temperature, laser pulse modulation, and their combination methods were investigated and compared by analyzing 2D and 3D laser beam profile.rnA thermal plate was built to control tissue temperature from 40°C through 10°C at 10°C decrement. A continuous laserrnof 660 nm was modulated at the frequencies of 1, 10, 25, and 50 Hz. 95% glycerol was injected into a region of interest of sample where laser is irradiated and its effect was analyzed after 5 min. Finally, their combination method was evaluated. Analysis was performed with the diffusion images acquired by CCD and the optical properties measured by double integrating sphere. Results demonstrated that average peak intensity of laser beam profile was 1) 1.57-fold higherrnat 10°C than 40°C, 2) 1.79-fold higher at 10 Hz than continuous wave, 3) 1.65-fold higher with 95% glycerol injectionrnthan no glycerol application, and 4) 2.52-fold higher at the combination method than independent methods. Average total intensity at FWHM was 1) 1.44-fold higher with tissue cooling, 2) 1.71-fold higher at 10 Hz, 3) 1.61-fold higher with glycerol injection, and 4) 2.19-fold higher with the combination method. In conclusion, this study implies that tissue-cooling, pulse modulation, glycerol injection, and their combination method can effectively deliver laser photon in LLLT by enhancing the photon density in soft tissue.