ABSTRACT
BACKGROUND: This paper demonstrates the use of optical diagnostic methods to assess the dynamic skin changes observed in acute and chronic exposure to ultraviolet (UV) radiation in vivo. METHODS: Firstly, in order to initiate photoaging (chronic UV exposure), animals (n = 40) were divided into two groups: chronic UV exposure (n = 30), and control (n = 10; without irradiation). Photoaging in animals was induced by chronic repeated exposure to UVA radiation three times per week, for 12 weeks continuously, while the UV dose increased stepwise over the course of the experiment (55 minimal erythema doses (MED) in total). Laser fluorescence spectroscopy (LFS), optical tissue oximetry (OTO), laser Doppler flowmetry (LDF), and optical coherence tomography (OCT) of the shaved dorsum skin were performed regularly, once per week until the conclusion of the study. At 0, 5, and 12 weeks of the experiment, histological examination of animal tissues using hematoxylin/eosin and Masson's trichrome staining was performed. At the second stage, erythema was induced in mice (n = 15) by acute UV exposure at high doses. The colorimetric assay of the image from a digital RGB camera was used to evaluate the erythema index. RESULTS: The tissue content index ηcollagen of collagen was appropriate for the characterization of skin photoaging. Significant differences (p < 0.05) in ηcollagen were found between the control and photoaging groups from the 5th to the 9th week of the experiment. In addition, the rate of collagen degradation in the control group was about half that of the photoaging group. This marker allows the differentiation of photo- and chronoaging. OCT revealed the main optical layers of the skin in compliance with the histological pattern. The analysis of the RGB camera images provided visualization of the acute skin reaction to UV radiation. CONCLUSIONS: This study demonstrates the applicability of optical methods for the quantitative assessment of acute and chronic skin effects of UV exposure in vivo.
ABSTRACT
BACKGROUND AND OBJECTIVES: To evaluate the feasibility of using a novel blue diode laser (blue laser), a thulium fiber laser (Tm laser), and their combination as a directed-energy surgical tool in laparoscopic partial nephrectomy (LPN). STUDY DESIGN/MATERIALS AND METHODS: The blue laser emitting at 442 nm, the Tm laser emitting at 1,940 nm wavelengths, and the combination of them were tested. First, cutting and coagulative abilities of the lasers were characterized ex vivo on porcine kidney in air and CO2 . Histological staining was performed to assess the efficiency of ablation and coagulation. Next, experimental LPN was performed on a porcine model at zero ischemia. Upper and lower segments of both kidneys were resected. Total operation time and resection time were measured; bleeding and carbonization were evaluated. RESULTS: Ex vivo data show that laser-induced ablation and coagulation processes do not differ substantially between CO2 and air environments. Histological analysis of ex vivo incisions demonstrates that the blue laser produced deep ablation with relatively narrow coagulation zone, whereas Tm laser was less efficient in terms of ablation but possessed excellent coagulative properties. Experimental LPN revealed that the blue laser provided fast cutting with minimal carbonization, whereas Tm laser induced slow cutting with strong carbonization. The combination of the blue and Tm lasers provided the most promising results demonstrating the highest resection rate, almost carbonization free resection surface and clinically acceptable hemostasis enabling LPN without the need for vessel clamping. CONCLUSIONS: The blue laser can be efficiently utilized in LPN. Furthermore, the combination of the blue and Tm lasers into a single modality may be beneficial for further development of successful laser-assisted LPN. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.
