微脉冲半导体激光的临床应用现状

微脉冲半导体激光是一种阈下光凝技术 ,它能选择性地作用于视网膜色素上皮细胞 ,避免损伤视网膜神经层 ,在产生治疗作用的同时最大限度地保持视功能 ,对治疗黄斑水肿、中心性浆液性脉络膜视网膜病变 (中浆 )和玻璃膜疣具有较好的疗效。本研究阐述了微脉冲半导体激光的原理、临床应用及激光光凝斑检测等方面的进展。     

Modeling optical and thermal distributions in tissue during laser irradiation

The propagation of light energy in tissues is an important problem in phototherapy, especially with the increased use of lasers as light sources. Often a slight difference in delivered energy separates a useless, efficacious, or disastrous treatment. Methods are presented for experimental characterization of the optical properties of a tissue and computational prediction of the distribution of light energy within a tissue. A standard integrating sphere spectrophotometer measured the total transmission, Tt, total reflectance, Rt, and the on-axis transmission, Ta, for incident collimated light that propagated through the dermis of albino mouse skin, over the visible spectrum. The diffusion approximation solution to the one-dimensional (1-D) optical transport equation computed the expected Tt and Rt for different combinations of absorbance, k, scattering, s, and anisotropy, g, and by iterative comparison of the measured and computed Tt and Rt values converged to the intrinsic tissue parameters. For example, mouse dermis presented optical parameters of 2.8 cm-1, 239 cm-1, and 0.74 for k, s, and g, respectively, at 488 nm wavelength. These values were used in the model to simulate the optical propagation of the 488-nm line of an argon laser through mouse skin in vivo. A 1-D Green's function thermal diffusion model computed the temperature distribution within the tissue at different times during laser irradiation. In vitro experiments showed that the threshold temperature range for coagulation was 60 degrees-70 degrees C, and the kinetics were first order, with a temperature-dependent rate constant that obeyed an Arrhenius relation (molar entropy 276 cal/mol-degrees K, molar enthalpy 102 kcal/mol). The model simulation agreed with the corresponding in vivo experiment that a 2-s pulse at 55 W/cm2 irradiance will achieve coagulation of the skin.     

Protective effect of human adipose-derived stem cells transplanted to fat grafts against high-power laser therapy mediated fat tissue damage

Introduction

High Power Laser therapy (HPLT) can damage tissues due to its high skin absorption and side effects. The objective of this study was to determine the protective effect of human adipose-derived stem cells (hADSCs) against HPLT-mediated fat tissue damage after fat grafts in an in vivo study.

Effects on Bone Repair of Osteotomy With Drills or With Erbium,Chromium: Yttrium‐Scandium‐Gallium‐Garnet Laser: Histomorphometric and Immunohistochemical Study

Background: The erbium, chromium:yttrium‐scandium‐gallium‐garnet (Er,Cr:YSGG) laser has been widely used in the dental clinic; however, few studies have demonstrated the advantages of the use of this laser for bone osteotomies. The purpose of this study is to evaluate and compare the bone repair process of defects generated by the Er,Cr:YSGG laser or conventional drills. Methods: Ninety‐six rats were divided into two groups of 48 animals (drill group and laser group). After surgical exposure of the right tibia, the animals were subjected to a 2‐mm‐diameter osteotomy created by conventional drills (drill group) or by the Er,Cr:YSGG laser (laser group). The animals were sacrificed 0, 3, 7, 14, 30, and 60 days after the creation of the defect, and histologic sections were obtained and used for histomorphometric and immunohistochemical analyses for the detection of osteocalcin, osteoprotegerin, receptor activator of nuclear factor κ‐B ligand, vascular endothelial growth factor, and caspase‐3. Results: The osteotomy with the drill produced well‐delimited and smooth walls, whereas the osteotomies in the laser group were irregular and presented an amorphous basophilic line and bone necrosis that was slowly resorbed during the repair process. Despite these characteristics, bone repair was similar between groups at various time points, and, at 60 days, the defects in both groups were completely repaired by newly formed bone. Conclusion: The repair process of osteotomies created by the Er,Cr:YSGG laser, despite producing thermal damage to bone tissue, is comparable to that with conventional drills.     

Laser treatment for superficial vascular lesions in a public hospital programme

Summary

Use of a pulsed dye laser in the dermatology department of a public hospital proved to be effective treatment for the large majority of patients with superficial cutaneous vascular lesions. Excellent or good results were obtained on completion of treatment for 87% of adult patients with port wine stain (n = 23), 96% with telangiectasia (n = 48) and 85% with other dermatological conditions (n = 52). Interim results from test patches on children with port wine stain (n = 37) gave 74% excellent or good responses, consistent with results obtained for adults. The great majority of patients were satisfied with the results of their treatment. Shortcomings of the service were slowness of the laser method and the limited resources in the public hospital system. Newer types of laser can be expected to reduce the time and costs of treatment, but should be critically assessed in terms of patient outcomes.