Cell Biochem Biophys DOI 10.1007/s12013-013-9596-6
ORIGINAL PAPER
Comparative Study of 1,064-nm Laser-Induced Skin Burn and Thermal Skin Burn Yi-Ming Zhang • Jing Ruan • Rong Xiao Qiong Zhang • Yue-Sheng Huang
•
Ó Springer Science+Business Media New York 2013
Abstract Infrared lasers are widely used in medicine, industry, and other fields. While science, medicine, and the society in general have benefited from the many practical uses of lasers, they also have inherent safety issues. Although several procedures have been put forward to protect the skin from non-specific laser-induced damage, individuals receiving laser therapy or researchers who use laser are still at risk for skin damage. This study aims to understand the interaction between laser and the skin, and to investigate the differences between the skin damage caused by 1,064-nm laser and common thermal burns. Skin lesions on Wistar rats were induced by a 1,064-nm CW laser at a maximum output of 40 W and by a copper brass bar attached to an HQ soldering iron. Histological sections of the lesions and the process of wound healing were evaluated. The widths of the epidermal necrosis and dermal denaturalization of each lesion were measured. To observe wound healing, the epithelial gap and wound gap were measured. Masson’s trichrome and picrosirius red staining were also used to assess lesions and wound healing. The thermal damage induced by laser intensified
Electronic supplementary material The online version of this article (doi:10.1007/s12013-013-9596-6) contains supplementary material, which is available to authorized users. Y.-M. Zhang J. Ruan R. Xiao Q. Zhang Y.-S. Huang (&) Institute of Burn Research, Southwest Hospital, State Key Laboratory of Trauma, Burns and Combined Injury, Third Military Medical University, Chongqing 400038, People’s Republic of China e-mail:
[email protected] Present Address: Y.-M. Zhang Department of Plastic and Cosmetic Surgery, Xinqiao Hospital, Third Military Medical University, Xinqiao Road, Sha Ping Ba District, Chongqing 400037, People’s Republic of China
significantly in both horizontal dimension and in vertical depth with increased duration of irradiation. Ten days after wounding, the dermal injuries induced by laser were more severe. Compared with the laser-induced skin damage, the skin burn induced by an HQ soldering iron did not show a similar development or increased in severity with the passage of time. The results of this study showed the pattern of skin damage induced by laser irradiation and a heated brass bar. This study also highlighted the difference between laser irradiation and thermal burn in terms of skin damage and wound healing, and offers insight for further treatment. Keywords
Laser Burn Skin Damage
Introduction Infrared lasers are widely used in medicine, industry, and other fields [1, 2]. Infrared wavelengths are readily absorbed by animal tissues because of their high water content [3]. Although science, medicine, and the society as a whole have benefited from the many practical uses of lasers, they also present inherent risks [4, 5]. For instance, the skin, being the human body’s largest organ, can be damaged when receiving laser therapy. In addition, researchers conducting scientific studies on laser are also at risk of its damaging effects. Therefore, it is important for us to understand laser–skin interaction and the mechanism by which laser damages the skin, which may be very helpful in finding an effective treatment for laser-induced skin damage. The responses of biological tissues to laser irradiation are typically classified as photochemical interaction, photothermal interaction, photo-ablation, plasma-induced ablation, and photo-disruption effects [6–8]. The laser–tissue interaction depends on the wavelength, pulse duration, spot size, and
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power, among others. For example, it has been reported that photothermal effect is mainly produced by infrared lasers, while ultraviolet radiation causes photochemical effect [6–8]. Among all known laser–tissue interactions, photothermal damage is the most important, since high temperature caused by photothermal effects is the main factor that produces skin damage. In addition, the photothermal interaction between lasers and biological tissues has various thermal effects, such as coagulation, vaporization, and carbonization. The energy released by laser also accumulates and diffuses in tissues, further extending its thermal effects and thermal damage. As mentioned above, among laser–tissue interactions, photothermal effect is the most important. As the body’s largest organ, the skin has a high risk of getting damaged after laser irradiation. Although there are several studies on the photothermal effect of lasers on the skin, the dynamics of laser–skin interaction, including ablation and heat diffusion processes, are poorly understood. Furthermore, the biological wound healing response to laser irradiation remains largely unexplored. Several reports have also demonstrated that wound healing of laser-induced damage is significantly slower compared to scalpel incisions [9– 11]; however, the difference between laser-induced skin damage and skin thermal burn remains unclear. Among lasers with different wavelengths, the 1,064-nm laser is known to mainly produce photothermal effect on the irradiated skin. Because of its penetrativity and it is easily absorbed by melanocytes, the 1,064-nm laser is used to treat melanocytic nevi [12], hyperpigmentation [13], and other skin disorders. It is also used to treat skin aging by stimulating dermal regeneration [2]. Photothermal effect is also reported to be related to the model of action of laser; hence, 1,064-nm lasers with different action models have been applied in different fields. For example, long-pulsed 1,064-nm laser is used to treat wrinkles. Q-switched laser is used in removing unwanted hair, tattoos, and pigmented and vascular lesions [14]. Along with their widespread use comes the increased risk of injury from their use and the need for methods to ameliorate these injuries. In an effort to understand laser– tissue interactions, the 1,064-nm laser has been used as a source to create a wound tissue environment. Therefore, in this study, we adopt 1,064-nm laser to induce skin damage, and to investigate photothermal effect on the irradiated skin. Several studies on skin burn have been performed [15–17]. In these studies, pressing a heated electric iron directly to the skin to create burn wounds of varying sizes has been proven the most effective way to study cutaneous wound healing and the therapeutic effect of drugs on wound healing [17]. In this study, a heated copper brass bar attached to an HQ soldering iron is used to induce thermal burns on skin, as a control to laser. This study aims to understand the interaction between laser and the skin, and to investigate the differences between 1,064-nm laser-induced burns and thermal burns.
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Materials and Methods Animal Model This study was approved by the Animal Care and Ethics Committee of the Third Military Medical University (Chongqing, China). Two hundred and forty Wistar rats weighing 200–250 g were provided by the Experimental Animal Production and Supply Center of the Daping Hospital, Third Military Medical University (Chongqing, China). They were fed standard rat chow and kept in an environment with constant temperature and humidity and a 12-h light/dark cycle. After 48 h, the rats were anesthetized intraperitoneally using pentobarbital sodium (50 mg/kg) and their backs shaved with an electric clipper. One day after shaving, the rats were re-anesthetized intraperitoneally using pentobarbital sodium (50 mg/kg). Then the shaved area was divided into four 2 9 2 cm grids by a marker pen. The left two grids were subjected to an electrical iron heated to 390 °C. The right two were treated with continuous laser beam with 40 W output at a wavelength 1,064-nm. This study used Gaussian-shaped spot sizes of approximately 10 mm and exposure durations of 2, 4, 6, and 8 s. Standardized digital photographs of the wounds were taken at 2 h, 1, 4, 7, 10, and 14 days postwounding and the open wound areas were determined with an image analyzer (ImageProPlus version 6.0, Meyer Instruments, Inc.). The ANOVA and Student’s t test were used for the statistical analysis. H&E Staining and Analyses The wounds, together with unwounded skin margins, were excised within 2 h postwounding. Other wounds from laserirradiated and thermal-burned rats were obtained at 1, 4, 7, 10, and 14 days after wounding. All the skin samples were embedded in 10 % neutral-buffered formalin and paraffin. A series of sections covering the whole wound area were stained with H&E and were used to calculate the average epithelial gap and wound gap. The epithelial gap is defined as the distance between the advancing edges of the epidermal keratinocytes, and wound gap was determined by the distance between the hair follicles, as described previously [18]. To show the entire wound, multiple overlapping pictures had to be taken under a microscope (Leica, DM 6000B, Germany) and used to reconstitute them. Masson’s Trichrome Staining Masson’s trichrome staining was performed using a staining skit. Sections were conventionally dewaxed and rehydrated, incubated with Masson solution at 37 °C for 5 min, and rinsed with deionized water for 1 min. The sections were then incubated with phosphomolybdic acid for 5 min.
Cell Biochem Biophys
Subsequently, sections were immersed in 2 % aniline blue for 5 min. After that, sections were rinsed under deionized water for 1 min and incubated with differentiated solution for 1 min. Finally, all sections were rinsed in 95 % ethanol, and absolute ethanol in turn, immersed in xylene for 10 min, and mounted with resin. Collagen fibers were stained blue, but denaturalized collagen were stained red [19], cytoplasm and erythrocyte were stained red, and nuclei were stained bluish brown. Picrosirius Red Staining Paraffin-embedded wound sections were immersed in 0.1 % Sirius red (in picric acid) for 1 h and then washed in acidified water. When examined under plane-polarized light, larger collagen fibers appear red, orange, or yellow
and the thinner ones green. This birefringence is highly specific to collagen [20].
Results Distinct Damage Models of Thermal Skin Burn and Radiation Heating-Induced Skin Burn This study used Gaussian-shaped, 10-mm spots and exposure durations of 2, 4, 6, and 8 s. With increasing irradiation time, the skin injuries became larger and more severe (Fig. 1). An 8-s irradiation led to coagulation burns with clear edges in the internal organs directly under the irradiated spot (Figs. 1, 4). From 2 h to 1 day after irradiation, an obvious increase in burn-wound size was observed in
Fig. 1 Distinct lesions of 1,064-nm laser-induced skin burn and thermal skin burn. *P \ 0.05 when compared with 6 or 8 s group, respectively. ## P \ 0.05 when compared with 2 or 4 s group, respectively. **The difference between 4, 6, and 8 s groups was significant (P \ 0.05). #P \ 0.05 when compared with 2 h postwounding
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Fig. 2 Histological observation of wound 2 h postwounding
the groups subjected to longer irradiation duration (Figs. 1, 2, 3). In contrast, no apparent differences were observed in the wound surface among the thermal-burned groups (Fig. 1). However, an incrustation was observed in the stasis zone around the wounded area (Fig. 1), but without any distinct change in the wound size. As burn wound becomes more severe within 24–48 h [21], we took the wound tissue and made histological observation at 2 h and 1 day postwounding. In the 2-s lasertreated group, no evident injury was observed (Figs. 2, 3). In the 4-s laser-treated group, epidermal and superficial dermal injury and muscle fiber edema in the subcutaneous smooth muscle layer (tunica muscularis) were observed within 2 h (Fig. 2). The epidermal injury became smaller 1 day postwounding, while the injury in the shallow dermis
Fig. 3 Histological observation of wound 1 day postwounding
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became more distinct, compared with that 2 h postwounding (Fig. 3). The 6-s laser-treated group presents similar injuries with the 4-s group, although bigger and deeper. The subcutaneous smooth muscle layer showed hydropic degeneration after being heated. Hydropic degeneration was observed in the underlying superficial skeletal muscle layer because heat breaks and separates muscle fibers (Fig. 2). After 1 day, the dermal burn deteriorated (Fig. 3). The 8-s laser-treated group presented a bigger and deeper injury. Meanwhile, a coagulation necrosis was observed in the subcutaneous muscles and in the internal organs directly below the irradiated areas (Figs. 2, 3, 4). In contrast, injuries in the thermal-burned group did not worsen with the passage of time. The burn wounds were deeper 1 day postwounding compared with those after 2 h (Figs. 2, 3).
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Fig. 4 Laser can induce skeletal muscle and visceral lesions. Laser irradiation can induce skeletal muscle slight lesion at a duration of 6 s (Aa, Ba). It can induce skeletal muscle (Ab, Bb), pulmonary (Ac left
arrow, Bc), gastric (Ac right arrow, Bd), small intestinal (Ad and Bf), colonic (Ae, Be), nephric (Af, Bg), splenic (Ag, Bi) and hepatic lesions (Bi) at a duration of 8 s
Difference in Wound Healing Between ThermalBurned Skin and 1,064-nm Laser-Induced Skin Burn
(Supplementary Fig. 1). On the 14th day, the residual wounds are small in the 4- and 6-s laser-treated groups, while big in the 8-s laser-treated group after the decrustation. The 8-s laser-treated group, with relatively large residual wounds, presented statistically significant differences (P \ 0.05) from the 2-, 4-, and 6-s laser-treated groups, which showed small residual wounds. There were
We observed the general characteristics and pathology of both wounds. On the 4th, 7th, 10th, and 14th days we found that the wounds were covered with eschar in all the 1,064-nm laser-treated and thermal-burned groups
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no significant differences between the 2-, 4-, and 6-s lasertreated groups (P [ 0.05) (Fig. 7). Histological observation revealed that epidermal gap and wound diameter are slightly increased in the lasertreated groups from 1 day postwounding to 4 days (Figs. 3, 5, 8 and Supplementary Figs. 2). While in the thermalburned groups, the wounds were covered by eschar with smaller wound diameters. Such differences indicate the progressive deepening of the burn wound in the lasertreated groups. On the 7th day, the epithelium began to creep and grow to the center of the wound in both the laserand thermal-burned groups (Supplementary Fig. 3). On the 10th day, the neonatal epithelium had crept to cover the
Fig. 5 Histological measurements for skin lesion. a Epidermal lesion induced by laser irradiation 2 h postwounding. b Dermal lesion induced by laser irradiation or thermal burn. *P \ 0.05 when compared with 2 s group 1 day postwounding
Fig. 6 Wound collagen accumulation was different between laser groups and thermal burn groups wound tissue on the 14th day from laser-irradiated rats and thermal-burned rats was analyzed for collagen content by Picro-Sirius staining. Red type I collagen was observed in laser groups, but green type III collagen in thermal burn groups (Color figure online)
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wound surface in the 4-s laser-treated group. In the 6- and 8-s laser-treated groups and in all the thermal-burned groups, the neonatal epithelium began to creep to the center of the wound (Supplementary Fig. 4). On 14th day, the neonatal epithelium covered the wound surface in the 6-s laser-treated group. This group also showed larger granulation tissues than the 4-s laser-treated group. The 8-s lasertreated group only revealed a few neonatal granulation tissues after decrustation, with a large area of unhealed wound surface. A large number of neonatal granulation tissues appeared on the wound surface in the thermalburned groups. Taking the appearance of the hair follicles as the demarcation between granulation tissues and the normal dermis, the 8-s laser-treated group showed the largest extent of granulation tissues. The epithelium did not cover the wound surface in the thermal-burned group. With Masson’s staining, the dermis in the wound area of lasertreated group appeared deep red, which intensified with the passage of time. This demonstrates the progressive degeneration and necrosis in the wound dermis (Supplementary Fig. 5). We assessed the epidermal gap and found that since 4 days postwounding, the laser- and thermal-burned groups presented common patterns in the epidermal gap; that is, longer irradiation time causes more severe injury and wider epidermal gap. However, the epidermal gap diminished with time after injury (Fig. 8). We evaluated the wound gap and found that 4 days postwounding, the laser- and thermal-burned groups presented a common trend in the wound gap; that is, longer irradiation time causes more severe and wider wound gap. However, the wound gap diminished with time after injury (Fig. 8). On the 14th day, Picricsirius red staining and polarized light were applied to the wounds in both groups to assess collagen production. In the laser-treated groups, both types I and III collagen formed in the center of the wounds, whereas small and green type III collagen formed in the thermal-burned group (Fig. 6).
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Discussion The 1,064-nm Nd:YAG laser is widely used in the treatment of skin aging and skin pigmentosus diseases. However, a high-powered laser beam can lead to skin burns [22]. To study the differences between skin burns caused by the 1,064-nm laser and normal thermal burns, and to establish an effective treatment, we developed models of laser-induced burn injury and thermal-burned injury and compared them. We observed and compared the differences between laser-induced and thermal-burned injuries in the skin and other tissues through histopathological and mathematical methods. The healing patterns of the two types of wounds were also compared. Because of its low water absorption and small scattering coefficients, the 1,064-nm laser can cause a deep dermal injury [23]. This study observed that, unlike thermal burn, laser-induced tissue injury became bigger and deeper when irradiation time is increased. This discrepancy may be attributed to the different action modes of the two types of burns [22, 24–28]. In the injury caused by heated copper brass, the heat is conducted slowly from the skin surface to the deeper and surrounding areas [24–26]. However, in irradiation with 1,064-nm laser, the laser beam penetrates the skin’s deeper parts after it hits the surface. Meanwhile, tissues scatter laser and, thus, disperse the injury to the surrounding tissues, which occurred almost promptly [29– 31]. That explains why with prolonged exposure the skin injury rapidly become bigger. An interesting phenomenon was that the wound area was smaller than that of the laser light spot (a diameter of 10 mm and an area of 78.5 mm2) in the 4-, 6-, and 8-s laser-treated groups. This mainly resulted from the uneven distribution of energy of the laser beam. The Gaussian distribution [32] of the energy of laser beam (i.e., with high energy in the center while low energy on the periphery) accounts for the fact that the skin in the central areas are most likely to be injured. As tissues scatter the laser after it reaches the skin, and also because of the continued effect of peripheral laser beam of comparatively lower power, the wound area expanded rapidly. In the end, coagulation and necrosis occurred in the center and red inflammatory edema area with slight injury on the periphery, the latter arises from the inflammatory infiltration around the thrombi and blood vessels [28]. In addition, our observation notes that the skin surface showed a larger wound area than the dermis, which shows that the skin surface and the dermis scatter laser in a different manner [33, 34]. It might be also due to the fact that the skin surface has a lower damage threshold than collagen [33]. When comparing the results between laser-treated groups of different durations, we observed that the laserinduced injury becomes more severe as the exposure time is increased (Fig. 1). An interesting phenomenon was that
the dermal layer did not present apparent injury at 4 s, but an edema in the smooth muscle under the dermis (the tunica muscularis) and swelling and degeneration of the muscle cells were observed (Fig. 2). This is mainly due to the 1,064-nm laser’s good penetration capability and the difference between the smooth muscle’s and collagen’s sensitivity to laser-produced heat [1]. It also might arise from the selective photodecomposition effect of the 1,064nm laser [15, 35], which needs further verification. Laser irradiation not only leads to a full-thickness skin wound, but might also damage the internal organs directly under the irradiated area, especially when exposure reaches 8 s (manifested as a coagulative burn in a limited size; Fig. 4). Such damage should draw our special attention, as the tissues, especially the underlying internal organs, would be immediately injured, induced by an accidental overly intense laser beam, and thus posing a threat to life. Due to the further heat conduction and the involvement of the inflammatory cytokine, the burn wound would be more severe within 24–48 h [36–39]. Therefore, the assessment of the depth of the burn injury used to be made at around 24 h after injury. Comparing the progression of the burn wounds of laser-induced burns and thermal burns, we found the dermal damage intensified at 24 h than before injury in both groups. For example, in the 4- and 6-s laser-treated groups, a distinct coagulative necrosis area appeared after injury (Figs. 1, 2, 3). The thermalburned groups, however, did not present such a trend (Figs. 1, 2, 3). Further observation found that the gap between normal dermis was evidently reduced on 4th day than 1st day in the thermal-burned groups. However, the epidermal gap and the dermal wound diameter were still expanding 4 days after injury in the laser-treated groups. Such progressive expansion might be related to the following. First, a multitude of inflammatory factors contained in the transudate from the loose connective tissues and the dartos layer under the dermis would irritate the adjacent dermal tissues and cause further injury. Second, because of selective photothermolysis [35] of laser, no apparent hyalinization occurred in the dermis after laserinduced injury, but the endothelium of heat-injured-blood vessels and blood erythrocytes [28, 30, 34] form microthrombi, which lead to ischemia and, in turn, develop progressive necrosis in the uninjured dermis. It is also interesting to note that on 10th day after laser irradiation, the red-stained dermis continued to deepen in color (Supplementary Fig. 4) but did not extend in size in the horizontal plane (Fig. 8). This might result from the injury of the deep-seated vessels directly below the irradiated areas [30, 33]. On the horizontal level, although the laser would scatter sideways after it gets to the skin tissues [29, 31], it is not powerful enough to injure the vessels in the surrounding side-scattered areas.
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Cell Biochem Biophys Fig. 7 Wound healing on the 14th day. a Gross observation of wound closure in laser group and thermal burn group. b Distinct wound healing in laser group but similar wound healing in thermal burn group. *P \ 0.05 when compared with the 2-, 4-, or 6-s group
On 14th day postwounding, after the decrustation, the size of the burn wound varied significantly among the laser-treated groups (Fig. 7), which largely correlated with the considerable differences in the initial burn-wound size induced by the laser. However, in the thermal-burned groups, there was no distinct difference in the residual
wound between the 2-, 4-, and 6-s laser-treated groups, with the exception of the 8-s laser-treated group (Fig. 7). Histological assessment found the epidermal gap and burnwound width reduced from 4th to 14th day after injury in both laser-treated and thermal-burned groups (Fig. 8) and shared a similar development trend, only that there was a
Fig. 8 Histological measurements for wound healing. a A representative image for histological measurement on 10th day in 8 s thermal burn group. b Representative images of H&E staining (left) and Masson’s Trichrome staining (right) for wound healing on 14th day in
both groups. c Epidermal gap for laser group from 4th to 14th day. d Wound gap for laser group from 4th to 14th day. e Epidermal gap for thermal burn group from 4th to 14th day. f Wound gap for thermal burn group from 4th to 14th day
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more evident development trend among the laser-treated groups (Fig. 8). Such a fact might be associated with the significant differences in the initial burn-wound dimension in these groups. This study investigates the differences between the 1,064-nm laser-induced and thermal-burned skin burns, and in their healing patterns. Our results reveal that the laser-induced burn injury intensified significantly in both horizontal dimension and in vertical depth with the prolongation of the time. In addition, the laser is likely to injure the deep-seated tissues. Until 10th day, the laserinduced dermal injuries were progressively more severe. Compared with the laser-induced skin burns, the thermalburned skin injuries did not show a clear development trend, or turned progressively severe with the passage of time after injury. The above results provide us with data about the injuring pattern and turnover in the skin and other tissues by the laser. It also highlighted the differences between the laser-induced skin burns and the normal thermal skin burns, establishing a sound foundation for treatment of laser burn. Acknowledgments This work was supported by the National Program on Key Basic Research Project of China (973 Program; 2012CB518101), a Grant from National Natural Science Foundation of China (81071574) and a Grant from 1130 Project of Xinqiao Hospital.
References 1. Prieto, V. G., Diwan, A. H., Shea, C. R., et al. (2005). Effects of intense pulsed light and the 1,064-nm Nd:Yag laser on sundamaged human skin: histologic and immunohistochemical analysis. Dermatologic Surgery, 31, 522–525. 2. Trelles, M. A., Alvarez, X., Martin-Vazquez, M. J., et al. (2005). Assessment of the efficacy of nonablative long-pulsed 1064-Nm Nd:Yag laser treatment of wrinkles compared at 2, 4, and 6 months. Facial Plastic Surgery, 21, 145–153. 3. Querry, M. R., & Hale, G. M. (1972). Optical-constants of water in 200-Nm to 0.2-Mm wavelength region. Journal of the Optical Society of America, 62, 1381–1386. 4. Zivin, J. A., Albers, G. W., Bornstein, N., et al. (2009). Effectiveness and safety of transcranial laser therapy for acute ischemic stroke. Stroke, 40, 1359–1364. 5. Erceg, A., Bovenschen, H. J., van de Kerkhof, P. C. M., et al. (2009). Efficacy and safety of pulsed dye laser treatment for cutaneous discoid lupus erythematosus. Journal of the American Academy of Dermatology, 60, 626–632. 6. Peng, Q., Juzeniene, A., Chen, J., et al. (2008). Lasers in medicine. Reports on Progress in Physics, 71, 28. 7. Knappe, V., Frank, F., & Rohde, E. (2004). Principles of lasers and biophotonic effects. Photomed Laser Surgery, 22, 411–417. 8. van Leeuwen, T. G., & Borst, C. (1996). Fundamental laser-tissue interactions. Seminars in Interventional Cardiology, 1, 121–128. 9. Hall, R. R. (1971). Healing of tissues incised by a carbon-dioxide laser. British Journal of Surgery, 58, 222–225.
10. Kamat, B. R., Carney, J. M., Arndt, K. A., et al. (1986). Cutaneous tissue-repair following Co2-laser irradiation. The Journal of Investigative Dermatology, 87, 268–271. 11. Ross, E. V., Grossman, M. C., Duke, D., et al. (1997). Long-term results after Co2 laser skin resurfacing: a comparison of scanned and pulsed systems. Journal of the American Academy of Dermatology, 37, 709–718. 12. Rosenbach, A., Williams, C. M., & Alster, T. S. (1997). Comparison of the Q-switched alexandrite (755 Nm) and Q-switched Nd:Yag (1064 Nm) lasers in the treatment of benign melanocytic nevi. Dermatologic Surgery, 23, 239–244. 13. Parker, J., & Hamzavi, I. (2009). Q-switched Nd:YAG 1064-nm laser for the treatment of acne-Induced postinflammatory hyperpigmentation. J Am Acad Dermatol, 60, AB198. 14. Dang, Y. Y., Ren, Q. S., Liu, H. X., et al. (2005). Comparison of histologic, biochemical, and mechanical properties of murine skin treated with the 1064-Nm and 1320-Nm Nd:Yag lasers. Experimental Dermatology, 14, 876–882. 15. Babilas, P., Shafirstein, G., Baumler, W., et al. (2005). Selective photothermolysis of blood vessels following flashlamp-pumped pulsed dye laser irradiation: in vivo results and mathematical modelling are in agreement. The Journal of Investigative Dermatology, 125, 343–352. 16. Chen, B., O’Dell, D. C., Thomsen, S. L., et al. (2005). Porcine skin Ed50 damage thresholds for 2,000 Nm laser irradiation. Lasers in Surgery and Medicine, 37, 373–381. 17. Coolen, N. A., Vlig, M., van den Bogaerdt, A. J., et al. (2008). Development of an in vitro burn wound model. Wound Repair and Regeneration, 16, 559–567. 18. Eming, S. A., Werner, S., Bugnon, P., et al. (2007). Accelerated wound closure in mice deficient for interleukin-10. American Journal of Pathology, 170, 188–202. 19. Chvapil, M., Speer, D. P., Owen, J. A., et al. (1984). Identification of the depth of burn injury by collagen stainability. Plastic and Reconstructive Surgery, 73, 438–441. 20. Junqueira, L. C. U., Bignolas, G., & Brentani, R. R. (1979). Picrosirius staining plus polarization microscopy, a specific method for collagen detection in tissue-sections. Histochemical Journal, 11, 447–455. 21. Papp, A., Kiraly, K., Harma, M., et al. (2004). The progression of burn depth in experimental burns: a histological and methodological study. Burns, 30, 684–690. 22. Khoury, J. G., Saluja, R., Keel, D., et al. (2008). Histologic evaluation of interstitial lipolysis comparing 1064 Nm, 1320 Nm and 2100 Nm lasers. Lasers in Surgery and Medicine, 40, 402–406. 23. Goldberg, D. J., & Silapunt, S. (2001). Histologic evaluation of a Q-switched Nd:Yag laser in the nonablative treatment of wrinkles. Dermatologic Surgery, 27, 744–746. 24. Liu, H. X., Dang, Y. Y., Wang, Z., et al. (2008). Laser induced collagen remodeling: a comparative study in vivo on mouse model. Lasers in Surgery and Medicine, 40, 13–19. 25. Jiang, S. C., Ma, N., Li, H. J., et al. (2002). Effects of thermal properties and geometrical dimensions on skin burn injuries. Burns, 28, 713–717. 26. Mercer, G. N., & Sidhu, H. S. (2005). Modeling thermal burns due to airbag deployment. Burns, 31, 977–980. 27. Ng, E. Y. K., & Chua, L. T. (2002). Comparison of one- and twodimensional programmes for predicting the state of skin burns. Burns, 28, 27–34. 28. Chen, B., Thomsen, S. L., Thomas, R. J., et al. (2008). Histological and modeling study of skin thermal injury to 2.0 Mu M laser irradiation. Lasers in Surgery and Medicine, 40, 358–370. 29. Wilmink, G. J., Opalenik, S. R., Beckham, J. T., et al. (2008). InVivo optical imaging of Hsp70 expression to assess collateral
123
Cell Biochem Biophys
30.
31.
32.
33.
tissue damage associated with infrared laser ablation of skin. Journal of Biomedial Optics, 13, 12. Tanghetti, E., Sherr, E. A., Sierra, R., et al. (2006). The effects of pulse dye laser double-pass treatment intervals on depth of vessel coagulation. Lasers in Surgery and Medicine, 38, 16–21. Sadick, N., & Schecter, A. K. (2004). Utilization of the 1320-Nm Nd:Yag laser for the reduction of photoaging of the hands. Dermatologic Surgery, 30, 1140–1144. Siegman, A. E., Sasnett, M. W., & Johnston, T. F. (1991). Choice of clip levels for beam width measurements using knife-edge techniques. IEEE Journal of Quantum Electronics, 27, 1098–1104. Dai, T. H., Diagaradjane, P., Yaseen, M. A., et al. (2005). Laserinduced thermal injury to dermal blood vessels: analysis of wavelength (585 Nm Vs. 595 Nm), cryogen spray cooling, and wound healing effects. Lasers in Surgery and Medicine, 37, 210–218.
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34. Pikkula, B. M., Chang, D. W., Dai, T. H., et al. (2005). Epidermal and vascular damage analysis of in vivo human skin in response to 595 Nm pulsed laser irradiation. Lasers in Surgery and Medicine, 37, 19–28. 35. Anderson, R. R., & Parrish, J. A. (1983). Selective photothermolysis—precise microsurgery by selective absorption of pulsed radiation. Science, 220, 524–527. 36. Achauer, B. M., & Martinez, S. E. (1985). Burn wound pathophysiology and care. Critical Care Clinics, 1, 47–58. 37. Arturson, G. (1996). Pathophysiology of the burn wound and pharmacological treatment. The Rudi hermans lecture. Burns, 22, 255–274. 38. Gibran, N. S., & Heimbach, D. M. (2000). Current status of burn wound pathophysiology. Clinics in Plastic Surgery, 27, 11–22. 39. Nanney, L. B., Wenczak, B. A., & Lynch, J. B. (1996). Progressive burn injury documented with vimentin immunostaining. Journal of Burn Care and Rehabilitation, 17, 191–198.
