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Victor E Ross - One of the best experts on this subject based on the ideXlab platform.
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depth of tissue ablation and residual Thermal Damage caused by a pixilated 2 940 nm laser in a swine skin model
Lasers in Surgery and Medicine, 2010Co-Authors: Thomas D Regan, Nathan S Uebelhoer, Elizabeth K Satter, Victor E RossAbstract:Background/Objective The purpose of this study was to assess the effects of fluence, pulse stacking, and multiple passes on the depth of injury caused by a fractionated Er:YAG laser in an in vivo farm pig model. Design/Material/Methods A fractionated 2,940 nm Er:YAG laser (Pixel, Alma Lasers, Caesarea, Israel) was applied to the flank skin of a Yorkshire cross pig. The 11 mm×11 mm handpiece was comprised of either 49 or 81 microbeams (200 µm diameter), depending on the tip configuration. There were six different parameter sets divided according to total energy per pulse (150, 285, and 500 mJ) and tip type (81 or 49 microbeams per 11 mm×11 mm macrospot). Each of these six groups was subdivided according to number of stacked pulses (1, 3, and 6) and number of passes (1, 3, and 6). This resulted in a total of 36 treatment parameters. Results With the 49 microbeam configuration, a single pulse resulted in partial epidermal ablation at 150 mJ, complete epidermal ablation at 285 mJ and partial dermal ablation at 500 mJ to a depth of 90 µm. Stacking the pulses resulted in a significant increase in ablation with each fluence with the maximal depth of ablation measured at 140 µm after six stacked pulses at 500 mJ. Increasing the number of passes did not result in a significant increase in ablative depth, but did create a larger surface area of ablation. Residual Thermal Damage (RTD) was minimal and remained between 10 and 20 µm. Conclusions The fractionated Er:YAG laser exhibited some of the same tissue interactions as its fully ablative counterparts. An increase in fluence resulted in an increase in ablative depth with minimal RTD. Additionally, RTD was unaffected by pulse stacking or by additional passes. Differences were that pulse stacking appeared to yield a more rapid decrease in ablation efficiency and additional passes did not seem to increase the depth of ablation. Lasers Surg. Med. 42:808–811, 2010. © 2010 Wiley–Liss, Inc.
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comparison of carbon dioxide laser erbium yag laser dermabrasion and dermatome a study of Thermal Damage wound contraction and wound healing in a live pig model implications for skin resurfacing
Journal of The American Academy of Dermatology, 2000Co-Authors: Victor E Ross, Joop M. Grevelink, David J Barnette, Miroslav Skrobal, George S Naseef, Joeseph R Mckinlay, Rox R AndersonAbstract:Abstract Background: Advances in laser technology allow for precise tissue removal and minimal Thermal Damage. However, mechanisms for cosmetic improvement have not been determined. Investigators have suggested that ablation, collagen shrinkage, and new collagen deposition all contribute to the clinical outcome. Objective: In a live farm pig, we examined gross and microscopic effects of Thermal and mechanical ablation devices to characterize immediate and long-term mechanisms in skin rejuvenation. Methods: Two CO 2 lasers, an erbium:YAG laser, a dermabrader, and a dermatome were used to treat flank skin in a farm pig. There were 14 different treatment groups based on device type and working parameters. One to five sites were treated for each group. Wound surface areas were measured before treatment, immediately after treatment, and 7, 17, 23, 30, and 60 days thereafter. Biopsies were performed immediately after irradiation and 2, 7, 17, and 60 days after treatment. Results: For the CO 2 laser–induced wounds, surface area measurements showed that immediate and final wound contraction tended to increase with initial residual Thermal Damage (RTD) for a range of values, above which immediate contraction remained relatively constant. Although there was no immediate wound contraction with mechanical ablation devices, long-term wound contraction in the dermatome and dermabrasion sites increased with depth of ablation. The erbium:YAG laser sites healed in a manner similar to that of mechanically induced wounds. Wound contraction profiles over time were dependent on depth of RTD and depth of ablation. Sixty days postoperatively, histologic examination showed varying degrees of fibroplasia. Overall, there was greater compaction and horizontal orientation of collagen fibers in those wounds with more than 70 μm of dermal RTD. Grossly, all wounds were similar after 60 days, with the exception of the deep dermabrasion sites, at which clinical scarring was observed. Conclusion: Our results show that CO 2 laser resurfacing produces short- and long-term wound contraction that is greater than that induced by purely ablative methods for the same total depth of injury. The erbium laser produced wound contraction profiles similar to those produced by mechanical wounding. The data suggest that initial collagen contraction and Thermal Damage modulate wound healing. (J Am Acad Dermatol 2000;42:92-105.)
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effects of overlap and pass number in co2 laser skin resurfacing a study of residual Thermal Damage cell death and wound healing
Lasers in Surgery and Medicine, 1999Co-Authors: David J Barnette, Robert D Glatter, Victor E Ross, Joop M. GrevelinkAbstract:Background Newer CO2 laser systems incorporating short pulse and scanning technology have been used effectively to resurface the skin. As the number of resurfacing cases has increased, hypertrophic scarring has been reported more commonly. Previous dermabrasion and continuous wave CO2 studies have suggested that depth of injury and Thermal Damage are important predictors of scarring for a given anatomic region. To determine whether rapid overlapping of laser pulses/scans significantly altered wound healing, we examined residual Thermal Damage, cell death, and histologic and clinical wound healing in a farm pig. Methods and Materials Two popular CO2 systems were used, with a range of radiant exposures, degrees of overlap, and numbers of passes. Thermal Damage was assessed by histology, and dermal cell viability was measured with nitrotetrazolium blue staining. Presence or absence of clinical scarring was determined by textural change and loss of skin markings. Results We observed that dermal Thermal Damage did not increase significantly with pass number when performed as in the normal clinical setting (for 2–4 passes); however, by delivering rapidly overlapping pulses and scans, residual Thermal Damage and cell death depth were increased as much as 100% over areas without immediate overlap of laser impacts. Conclusions Immediate overlapping of CO2 laser pulses and scans is a significant risk factor in increasing Thermal Damage, cell death, and possibly scarring. Lasers Surg. Med. 24:103–112, 1999. © 1999 Wiley-Liss, Inc.
Joop M. Grevelink - One of the best experts on this subject based on the ideXlab platform.
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comparison of carbon dioxide laser erbium yag laser dermabrasion and dermatome a study of Thermal Damage wound contraction and wound healing in a live pig model implications for skin resurfacing
Journal of The American Academy of Dermatology, 2000Co-Authors: Victor E Ross, Joop M. Grevelink, David J Barnette, Miroslav Skrobal, George S Naseef, Joeseph R Mckinlay, Rox R AndersonAbstract:Abstract Background: Advances in laser technology allow for precise tissue removal and minimal Thermal Damage. However, mechanisms for cosmetic improvement have not been determined. Investigators have suggested that ablation, collagen shrinkage, and new collagen deposition all contribute to the clinical outcome. Objective: In a live farm pig, we examined gross and microscopic effects of Thermal and mechanical ablation devices to characterize immediate and long-term mechanisms in skin rejuvenation. Methods: Two CO 2 lasers, an erbium:YAG laser, a dermabrader, and a dermatome were used to treat flank skin in a farm pig. There were 14 different treatment groups based on device type and working parameters. One to five sites were treated for each group. Wound surface areas were measured before treatment, immediately after treatment, and 7, 17, 23, 30, and 60 days thereafter. Biopsies were performed immediately after irradiation and 2, 7, 17, and 60 days after treatment. Results: For the CO 2 laser–induced wounds, surface area measurements showed that immediate and final wound contraction tended to increase with initial residual Thermal Damage (RTD) for a range of values, above which immediate contraction remained relatively constant. Although there was no immediate wound contraction with mechanical ablation devices, long-term wound contraction in the dermatome and dermabrasion sites increased with depth of ablation. The erbium:YAG laser sites healed in a manner similar to that of mechanically induced wounds. Wound contraction profiles over time were dependent on depth of RTD and depth of ablation. Sixty days postoperatively, histologic examination showed varying degrees of fibroplasia. Overall, there was greater compaction and horizontal orientation of collagen fibers in those wounds with more than 70 μm of dermal RTD. Grossly, all wounds were similar after 60 days, with the exception of the deep dermabrasion sites, at which clinical scarring was observed. Conclusion: Our results show that CO 2 laser resurfacing produces short- and long-term wound contraction that is greater than that induced by purely ablative methods for the same total depth of injury. The erbium laser produced wound contraction profiles similar to those produced by mechanical wounding. The data suggest that initial collagen contraction and Thermal Damage modulate wound healing. (J Am Acad Dermatol 2000;42:92-105.)
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the effect of wiping on skin resurfacing in a pig model using a high energy pulsed co2 laser system
Dermatologic Surgery, 1999Co-Authors: E V Ross, Robert D Glatter, A Mowlavi, David J Barnette, Joop M. GrevelinkAbstract:Background. The impact of wiping in laser skin resurfacing has not been systematically studied. Methods. We examined the effects of wiping during single- and multiple-pass high energy pulsed CO2 laser skin resurfacing in a farm pig. Consequences of wiping were evaluated with regard to depth of residual Thermal Damage, tissue necrosis, and fibroplasia. Also, the impact of wiping on gross wound healing was observed. Wounds were followed for 21 days and biopsies were obtained on postoperative days 0, 1, and 21. Results. Immediate postoperative biopsies of single-pass wounds showed equivalent residual Thermal Damage regardless of wiping; in contrast, biopsies from multiple-pass sites without wiping showed more extensive and variable residual Thermal Damage than wiped sites. On postoperative day one, single pass sites without wiping were grossly less erythematous than wiped sites, and biopsies showed less extensive necrosis and inflammation. In contrast, multiple pass sites without wiping were grossly more erythematous than corresponding wiped sites, and biopsies revealed significantly increased and variable necrosis. After 21 days, multiple pass sites without wiping were grossly more erythematous and showed a thicker band of fibroplasia microscopy. Conclusions. For single pass wounds, not wiping decreased the level of wounding. In contrast, not wiping in multiple pass wounds significantly increased the depth and variability of residual Thermal Damage and necrosis, resulting in prolonged healing.
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effects of overlap and pass number in co2 laser skin resurfacing a study of residual Thermal Damage cell death and wound healing
Lasers in Surgery and Medicine, 1999Co-Authors: David J Barnette, Robert D Glatter, Victor E Ross, Joop M. GrevelinkAbstract:Background Newer CO2 laser systems incorporating short pulse and scanning technology have been used effectively to resurface the skin. As the number of resurfacing cases has increased, hypertrophic scarring has been reported more commonly. Previous dermabrasion and continuous wave CO2 studies have suggested that depth of injury and Thermal Damage are important predictors of scarring for a given anatomic region. To determine whether rapid overlapping of laser pulses/scans significantly altered wound healing, we examined residual Thermal Damage, cell death, and histologic and clinical wound healing in a farm pig. Methods and Materials Two popular CO2 systems were used, with a range of radiant exposures, degrees of overlap, and numbers of passes. Thermal Damage was assessed by histology, and dermal cell viability was measured with nitrotetrazolium blue staining. Presence or absence of clinical scarring was determined by textural change and loss of skin markings. Results We observed that dermal Thermal Damage did not increase significantly with pass number when performed as in the normal clinical setting (for 2–4 passes); however, by delivering rapidly overlapping pulses and scans, residual Thermal Damage and cell death depth were increased as much as 100% over areas without immediate overlap of laser impacts. Conclusions Immediate overlapping of CO2 laser pulses and scans is a significant risk factor in increasing Thermal Damage, cell death, and possibly scarring. Lasers Surg. Med. 24:103–112, 1999. © 1999 Wiley-Liss, Inc.
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effects of overlap and pass number in co2 laser skin resurfacing preliminary results of residual Thermal Damage cell death and wound healing
Lasers in Surgery: Advanced Characterization Therapeutics and Systems VII, 1997Co-Authors: E V Ross, Robert D Glatter, Daniella Duke, Joop M. GrevelinkAbstract:ABSTRACT Newer CO2 laser systems incorporating short pulse and scanning technology have been used effectively toresurface the skin. Although scarring is rare, as the number ofresurfacing cases has increased, somehypertrophic scarring has been observed. Previous dermabrasion and continuous wave (CW) CO2 studiessuggest that depth of injury and/or Thermal Damage are important predictors of scarring for a given anatomicregion. To determine ifoverlapping laser pulses/scans significantly altered wound healing, we examinedresidual Thermal Damage, cell death, and histologic and clinical wound healing in a farm pig. TheUltrapulse and SilkTouch systems were used with various radiant exposures, degrees of overlap, andnumbers ofpasses. Thermal Damage was assessed by histology, and dermal cell viability was measuredwith nitrotetrazolium blue staining. Presence or absence ofclinical scarring was determined by notingtextural change and loss of skin markings. We observed that Thermal Damage and cell death depth did notincrease significantly with pass number; however, by double-pulsing or double-scanning sites, residualThermal Damage and cell death depth were increased as much as 100 % over areas without immediateoverlap of laser impacts. Also, scarring was increased focally in areas with overlap. We conclude thatimmediate overlapping of CO2 laser pulses/scans is a significant risk factor in increasing Thermal Damage,cell death, and scarring.Keywords: Thermal Damage, CO2 laser, skin resurfacing, scar
E V Ross - One of the best experts on this subject based on the ideXlab platform.
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analysis of depth of ablation Thermal Damage wound healing and wound contraction with erbium yag laser in a yorkshire pig model
Journal of Drugs in Dermatology, 2015Co-Authors: S M Alsaad, E V Ross, W J Smith, D P DerienzoAbstract:Background and objectives The erbium YAG laser is commonly used for skin resurfacing. It is known that varying the pulse duration can influence residual Thermal Damage and wound healing. Our study used a porcine model to evaluate a broad range of settings in a comparison of depth of ablation, depth of residual Thermal Damage (RTD), and wound contraction employing both a full coverage and fractional hand piece with an erbium YAG laser. Materials and methods The laser delivered an ablative pulse followed by a heating pulse of variable duration using either the full coverage or fractional hand piece. Pulse durations for specific coagulation depths were selected based on existing heat transfer models. The bilateral flanks of a single Yorkshire pig were irradiated. There were 14 treatment groups. 3 sites were treated per group for a total of 42 sites. Two of the 3 sites were for observational assessments and the 3rd site served as a reservoir for biopsies. Biopsy specimens were collected on days 0, 1, 3, 7, 14, and 28. Bleeding, erythema, wound healing, and wound contraction (in the fractional hand piece groups) were assessed. Conclusion Wound healing is faster for fractional laser skin resurfacing compared with traditional contiguous resurfacing as demonstrated by textural changes and degree of erythema. The laser operator can be confident that the depth of ablation displayed on this system accurately reflects what is occurring in vivo for both confluent and fractional modes. Likewise, the measured degree of coagulation was consistent with panel display settings for the confluent mode. However, the degree of coagulation, as measured by the thickness of residual Thermal Damage, did not vary significantly between the fractional groups. In other words, the pulse duration of the second (heating) pulse did not impact the degree of coagulation in the fractional mode. There was a 2.3% wound contraction between some groups and a 6.5% wound contraction between other groups. A two way analysis of variance found a statistically significant difference in wound contraction based on ablation depth ( P = 0.012) but the degree of coagulation did not prove to be statistically significant for wound contraction (P = 0.66).
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use of a novel erbium laser in a yucatan minipig a study of residual Thermal Damage ablation and wound healing as a function of pulse duration
Lasers in Surgery and Medicine, 2002Co-Authors: E V Ross, David J Barnette, Joseph R Mckinlay, Francis P Sajben, Charles H Miller, Kenneth J Meehan, Norak P Chhieng, Mickey J Deavers, Brian D ZelicksonAbstract:Background and Objective Theoretical models show that varying pulse duration influences residual Thermal Damage in erbium YAG skin resurfacing. Accordingly, our objective was to compare residual Thermal Damage, ablation, tissue shrinkage, and wound healing between a variable pulsewidth erbium YAG laser and a popular CO2 resurfacing laser. Study Design/Materials and Methods The erbium laser delivered a typical ablative pulse (250 microseconds), followed by a heating pulse of variable duration. Pulse durations for specific coagulation depths were selected based on existing heat transfer models. The bilateral flanks of one Yucatan pig were irradiated. Eight sites were treated per group. Biopsies were performed just after treatment and 1, 3, 7, 21, and 60 days postoperatively. Results Just after irradiation, gross examination of “cold” (without a coagulation pulse) erbium sites showed a reddish papillary dermis consistent with conventional erbium laser ablation. Two and three pass CO2 sites showed uniform surface yellowing. The longer pulsewidth (“hot”) erbium groups showed only slight surface yellowing. Biopsies showed immediate Thermal Damage that increased with erbium pulse duration; however, actual residual Thermal Damage (RTD) was sometimes less than that predicted by the laser control panel. All wounds healed uneventfully by 14 days. Conclusions An erbium laser with a variable macropulse pulsewidth was capable of achieving RTD of up to 80 μm. Even greater RTD depths may be obtainable with future manipulations of fluence and pulse duration. Lasers Surg. Med. 30:93–100, 2002. © 2002 Wiley-Liss, Inc.
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the effect of wiping on skin resurfacing in a pig model using a high energy pulsed co2 laser system
Dermatologic Surgery, 1999Co-Authors: E V Ross, Robert D Glatter, A Mowlavi, David J Barnette, Joop M. GrevelinkAbstract:Background. The impact of wiping in laser skin resurfacing has not been systematically studied. Methods. We examined the effects of wiping during single- and multiple-pass high energy pulsed CO2 laser skin resurfacing in a farm pig. Consequences of wiping were evaluated with regard to depth of residual Thermal Damage, tissue necrosis, and fibroplasia. Also, the impact of wiping on gross wound healing was observed. Wounds were followed for 21 days and biopsies were obtained on postoperative days 0, 1, and 21. Results. Immediate postoperative biopsies of single-pass wounds showed equivalent residual Thermal Damage regardless of wiping; in contrast, biopsies from multiple-pass sites without wiping showed more extensive and variable residual Thermal Damage than wiped sites. On postoperative day one, single pass sites without wiping were grossly less erythematous than wiped sites, and biopsies showed less extensive necrosis and inflammation. In contrast, multiple pass sites without wiping were grossly more erythematous than corresponding wiped sites, and biopsies revealed significantly increased and variable necrosis. After 21 days, multiple pass sites without wiping were grossly more erythematous and showed a thicker band of fibroplasia microscopy. Conclusions. For single pass wounds, not wiping decreased the level of wounding. In contrast, not wiping in multiple pass wounds significantly increased the depth and variability of residual Thermal Damage and necrosis, resulting in prolonged healing.
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effects of overlap and pass number in co2 laser skin resurfacing preliminary results of residual Thermal Damage cell death and wound healing
Lasers in Surgery: Advanced Characterization Therapeutics and Systems VII, 1997Co-Authors: E V Ross, Robert D Glatter, Daniella Duke, Joop M. GrevelinkAbstract:ABSTRACT Newer CO2 laser systems incorporating short pulse and scanning technology have been used effectively toresurface the skin. Although scarring is rare, as the number ofresurfacing cases has increased, somehypertrophic scarring has been observed. Previous dermabrasion and continuous wave (CW) CO2 studiessuggest that depth of injury and/or Thermal Damage are important predictors of scarring for a given anatomicregion. To determine ifoverlapping laser pulses/scans significantly altered wound healing, we examinedresidual Thermal Damage, cell death, and histologic and clinical wound healing in a farm pig. TheUltrapulse and SilkTouch systems were used with various radiant exposures, degrees of overlap, andnumbers ofpasses. Thermal Damage was assessed by histology, and dermal cell viability was measuredwith nitrotetrazolium blue staining. Presence or absence ofclinical scarring was determined by notingtextural change and loss of skin markings. We observed that Thermal Damage and cell death depth did notincrease significantly with pass number; however, by double-pulsing or double-scanning sites, residualThermal Damage and cell death depth were increased as much as 100 % over areas without immediateoverlap of laser impacts. Also, scarring was increased focally in areas with overlap. We conclude thatimmediate overlapping of CO2 laser pulses/scans is a significant risk factor in increasing Thermal Damage,cell death, and scarring.Keywords: Thermal Damage, CO2 laser, skin resurfacing, scar
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effects of co2 laser pulse duration in ablation and residual Thermal Damage implications for skin resurfacing
Lasers in Surgery and Medicine, 1996Co-Authors: E V Ross, Yacov Domankevitz, Miroslav Skrobal, Rox R AndersonAbstract:Background and Objectives Resurfacing with the CO2 laser is rapidly gaining acceptance for skin rejuvenation. Advances in CO2 laser and scanning technology allow for precise tissue removal with minimal Thermal Damage. High energy CO2 laser pulses have been widely used effectively to smooth the surface of facial skin; however, pulse duration effects on ablation and Thermal Damage have not been systematically studied over the millisecond region (0.25–10 ms). Study Design/Materials and Methods This study characterizes the ablation threshold, heat of ablation, and residual Thermal Damage in skin resulting from CO2 laser pulses with a Gaussian beam profile. Mass loss from fresh pig skin was measured with an analytical balance, and residual Thermal Damage was determined through histology. Results Pulse durations >1 ms were associated with higher ablation thresholds and localized increased Thermal Damage. Conclusions Our results show that although pulse duration is an important determinant in ablation and Thermal Damage, irradiance is more critical as an independent parameter in predicting the effects of CO2 laser pulses. © 1996 Wiley-Liss, Inc.
Rox R Anderson - One of the best experts on this subject based on the ideXlab platform.
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lidocaine induced potentiation of Thermal Damage in skin and carcinoma cells
Lasers in Surgery and Medicine, 2019Co-Authors: Adam B Raff, Carina N Thomas, Gary S Chuang, Mathew M Avram, Rox R Anderson, M L PurschkeAbstract:OBJECTIVE Lidocaine acts as a local anesthetic by blocking transmembrane sodium channel permeability, but also induces the synthesis of heat shock proteins and sensitizes cells to hyperthermia. A previous study reported two cases of deep focal skin ulceration at points corresponding to depot local lidocaine injection sites after treatment with non-ablative fractional resurfacing and it was hypothesized that lidocaine had focally sensitized keratinocytes to the Thermal Damage of laser treatment. The objective of this study was to investigate whether lidocaine potentiates hyperthermia Damage to both normal and cancerous skin cells using an in vitro model. METHODS Normal skin cell lines (fibroblasts, keratinocytes), skin cancer cell lines (melanoma, basal cell carcinoma), and a mucosal cancer cell line (cervical carcinoma) were exposed to various concentrations of lidocaine (0-0.3%) with or without hyperthermia (37°C, 42°C). RESULTS Compared to normal skin cells, we demonstrate that cancer cell lines show significantly increased cell toxicity when a moderate temperature (42°C) and low lidocaine concentrations (0.1-0.2%) are combined. The toxicity directly correlates with a higher percentage of cells in S-phase (28-57%) in the cancer cell lines compared to normal skin cell lines (13-19%; R-square 0.6752). CONCLUSION These results suggest that lidocaine potentiates Thermal sensitivity of cell cycle active skin cells. The direct correlation between cell toxicity and S-phase cells could be harnessed to selectively treat skin and mucosal cancer cells while sparing the surrounding normal tissue. Additional research pre-clinically and clinically using several different heat sources (e.g., lasers, ultrasound, etc.) and lidocaine concentrations is needed to confirm and optimize these results. Lidocaine-enhanced hyperthermia may provide a non-invasive, alterative treatment option for highly proliferating, superficial skin, and mucosal lesions such as cancer or warts. Lasers Surg. Med. 51:88-94, 2019. © 2018 Wiley Periodicals, Inc.
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comparison of carbon dioxide laser erbium yag laser dermabrasion and dermatome a study of Thermal Damage wound contraction and wound healing in a live pig model implications for skin resurfacing
Journal of The American Academy of Dermatology, 2000Co-Authors: Victor E Ross, Joop M. Grevelink, David J Barnette, Miroslav Skrobal, George S Naseef, Joeseph R Mckinlay, Rox R AndersonAbstract:Abstract Background: Advances in laser technology allow for precise tissue removal and minimal Thermal Damage. However, mechanisms for cosmetic improvement have not been determined. Investigators have suggested that ablation, collagen shrinkage, and new collagen deposition all contribute to the clinical outcome. Objective: In a live farm pig, we examined gross and microscopic effects of Thermal and mechanical ablation devices to characterize immediate and long-term mechanisms in skin rejuvenation. Methods: Two CO 2 lasers, an erbium:YAG laser, a dermabrader, and a dermatome were used to treat flank skin in a farm pig. There were 14 different treatment groups based on device type and working parameters. One to five sites were treated for each group. Wound surface areas were measured before treatment, immediately after treatment, and 7, 17, 23, 30, and 60 days thereafter. Biopsies were performed immediately after irradiation and 2, 7, 17, and 60 days after treatment. Results: For the CO 2 laser–induced wounds, surface area measurements showed that immediate and final wound contraction tended to increase with initial residual Thermal Damage (RTD) for a range of values, above which immediate contraction remained relatively constant. Although there was no immediate wound contraction with mechanical ablation devices, long-term wound contraction in the dermatome and dermabrasion sites increased with depth of ablation. The erbium:YAG laser sites healed in a manner similar to that of mechanically induced wounds. Wound contraction profiles over time were dependent on depth of RTD and depth of ablation. Sixty days postoperatively, histologic examination showed varying degrees of fibroplasia. Overall, there was greater compaction and horizontal orientation of collagen fibers in those wounds with more than 70 μm of dermal RTD. Grossly, all wounds were similar after 60 days, with the exception of the deep dermabrasion sites, at which clinical scarring was observed. Conclusion: Our results show that CO 2 laser resurfacing produces short- and long-term wound contraction that is greater than that induced by purely ablative methods for the same total depth of injury. The erbium laser produced wound contraction profiles similar to those produced by mechanical wounding. The data suggest that initial collagen contraction and Thermal Damage modulate wound healing. (J Am Acad Dermatol 2000;42:92-105.)
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effects of co2 laser pulse duration in ablation and residual Thermal Damage implications for skin resurfacing
Lasers in Surgery and Medicine, 1996Co-Authors: E V Ross, Yacov Domankevitz, Miroslav Skrobal, Rox R AndersonAbstract:Background and Objectives Resurfacing with the CO2 laser is rapidly gaining acceptance for skin rejuvenation. Advances in CO2 laser and scanning technology allow for precise tissue removal with minimal Thermal Damage. High energy CO2 laser pulses have been widely used effectively to smooth the surface of facial skin; however, pulse duration effects on ablation and Thermal Damage have not been systematically studied over the millisecond region (0.25–10 ms). Study Design/Materials and Methods This study characterizes the ablation threshold, heat of ablation, and residual Thermal Damage in skin resulting from CO2 laser pulses with a Gaussian beam profile. Mass loss from fresh pig skin was measured with an analytical balance, and residual Thermal Damage was determined through histology. Results Pulse durations >1 ms were associated with higher ablation thresholds and localized increased Thermal Damage. Conclusions Our results show that although pulse duration is an important determinant in ablation and Thermal Damage, irradiance is more critical as an independent parameter in predicting the effects of CO2 laser pulses. © 1996 Wiley-Liss, Inc.
Gottfried O H Naumann - One of the best experts on this subject based on the ideXlab platform.
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q switched erbium yag laser corneal trephination Thermal Damage in corneal stroma and cut regularity of nonmechanical q switched erbium yag laser corneal trephination for penetrating keratoplasty
Cornea, 2004Co-Authors: Milenko Stojkovic, B Seitz, Achim Langenbucher, A Viestenz, Carmen Hofmannrummelt, Ursula Schlotzerschrehardt, Michael Kuchle, Gottfried O H NaumannAbstract:PURPOSE To assess stromal Thermal Damage and cut regularity induced by nonmechanical Q-switched Er:YAG laser corneal trephination for penetrating keratoplasty. METHODS Corneal trephination was performed in 80 enucleated porcine eyes by Q-switched (2.94-microm) Er:YAG laser, along with donor and recipient masks made of metal or ceramic. All combinations of 0.65- or 0.96-mm spot diameter and 45- or 50-mJ/pulse energy setting were used with each of the masks at a 5-Hz repetition rate. Corneas were processed for histologic examinations. Stromal Thermal Damage was quantified on PAS-stained slides, and cut regularity was assessed semiquantitatively on a scale from 0 (regular) to 3 (highly irregular). Transmission electron microscopy and scanning electron microscopy were performed on selected specimens. RESULTS The least Thermal Damage (mean +/- SD = 6.2 +/- 0.7 microm) was found in the donor ceramic group with 50-mJ/pulse energy and 0.65-mm spot diameter, while the best regularity of the cut (1.2 +/- 0.4) was found in the donor ceramic group with 45-mJ pulse energy and 0.65-mm spot diameter. Thermal Damage was less pronounced in donor than in recipient corneas (P < 0.01). Smaller spot diameter (0.65 mm) led to less Thermal Damage (P < 0.01) than the use of a 0.96-mm spot diameter. The differences in Thermal Damage between ceramic and metal masks were minimal. CONCLUSIONS After Q-switched Er:YAG laser corneal trephination for nonmechanical penetrating keratoplasty, reproducible high cut regularity and low concomitant Thermal Damage were observed. This is an encouraging finding in the search for a nonmechanical trephine for penetrating keratoplasty combining high precision and low cost.
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nonmechanical q switched erbium yag laser trephination for penetrating keratoplasty experimental study on human donor corneas
Archives of Ophthalmology, 2003Co-Authors: Milenko Stojkovic, B Seitz, Achim Langenbucher, A Viestenz, Carmen Hofmannrummelt, Ursula Schlotzerschrehardt, Michael Kuchle, Gottfried O H NaumannAbstract:Objective To assess the alterations in human donor corneal tissue induced by Q-switched erbium (Er):YAG laser corneal trephination. Methods Thirty human corneoscleral donor buttons unsuitable for transplantation were placed in an artificial chamber on an automated rotation device. Corneas were trephined with a Q-switched Er:YAG laser (wavelength, 2.94 µm; pulse duration, 400 nanoseconds) along (donor and recipient) aluminum silicate(ceramic) open masks. A spot diameter of 0.65 mm, energy setting of 50 m J/pulse, and repetition rate of 5 Hz were used. Corneal Thermal Damage and cut regularity were quantitatively assessed in 24 corneas processed for light microscopy and by transmission and scanning electron microscopy. Results The stromal Thermal Damage was the highest (mean [SD], 8.0 [2.7] µm) at a 150-µm cut depth and decreased downward. Cut regularity was very good and did not significantly differ between donors and recipients. Scanning electron microscopy confirmed that the cuts were highly regular; transmission electron microscopy revealed 2 distinctive subzones within the stromal Thermal Damage zone. Conclusions Thermal Damage induced by Q-switched Er:YAG nonmechanical corneal trephination was low, and the regularity of the cuts was very good. Clinical Relevance The Q-switched Er:YAG laser may have the potential to become an alternative to the excimer laser for nonmechanical penetrating keratoplasty.
