Numerical Analysis of Cold Injury of Skin in Cryogen Spray Cooling for Dermatologic Laser Surgery

2007 ◽  
Author(s):  
Dong Li ◽  
Ya-Ling He ◽  
Guo-Xiang Wang ◽  
Jie Xiao ◽  
Ying-Wen Liu
Keyword(s):  
Numerical Analysis ◽  
Laser Surgery ◽  
Spray Cooling ◽  
Cold Injury ◽  
Dermatologic Surgery ◽  
Spray Process ◽  
Skin Cells ◽  
Model Predictions ◽  
Cryogen Spray Cooling ◽  
Clinical Conditions

In laser dermatologic surgery, cryogen spray cooling (CSC) is used to avoid laith damage such as scars from skin burning due to the melanin absorption of the laser beam. As the cryogen is fully atomized from the nozzle, evaporation of the droplets may quickly drop the cryogen temperature below −60 °C, depending on the spray distance from the nozzle. Such a low temperature is potential to cold injury for skin. Therefore, spray process should be accurately controlled during clinical practice to achieve sufficient protection and to avoid cold injury. This study presents a numerical analysis of cold injury of skin in cryogen spray cooling for dermatologic laser surgery. The model for cryogen spray cooling of skin, developed early, is extended to include the freezing of skin cells. The model predictions include the movement of the lethal isothermals. The severity of cold injury is then quantified under various clinical conditions. The effect of initial temperature and the spurt duration on possible cold injury of skin are also investigated.

scholarly journals Influence of spraying distance and postcooling on cryogen spray cooling for dermatologic laser surgery

2001 ◽  
Author(s):  
Guillermo Aguilar ◽  
Boris Majaron ◽  
John A. Viator ◽  
Brooke Basinger ◽  
Emil Karapetian ◽  
...  
Keyword(s):  
Laser Surgery ◽  
Spray Cooling ◽  
Cryogen Spray Cooling

Effect of Nozzle Size on the Surface Heat Transfer Dynamics during Cryogen Spray Cooling in Dermatologic Laser Surgery

2012 ◽  
Vol 39 (3) ◽  
pp. 0303005
Author(s):  
周致富 Zhou Zhifu ◽  
王锐 Wang Rui ◽  
王国祥 Wang Guoxiang ◽  
郭烈锦 Guo Liejin ◽  
陈斌 Chen Bin ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Laser Surgery ◽  
Spray Cooling ◽  
Surface Heat ◽  
Surface Heat Transfer ◽  
Nozzle Size ◽  
Cryogen Spray Cooling

scholarly journals Characterization of Cryogen Spray Cooling With Thin-Film Thermocouple

2007 ◽  
Author(s):  
Wangcun Jia ◽  
Thang Nguyen ◽  
Jaskaran Gill ◽  
J. Stuart Nelson
Keyword(s):  
Thin Film ◽  
Skin Temperature ◽  
Human Skin ◽  
Bulk Material ◽  
Thermal Contact ◽  
Spray Cooling ◽  
Dermatologic Surgery ◽  
Medical Laser ◽  
Cooling Period ◽  
Cryogen Spray Cooling

Cryogen spray cooling (CSC) has been used effectively to protect the epidermis during laser dermatologic surgery. However, the temperature reduction in human skin induced by CSC has not been reliably determined due to the short cooling period and significant temperature gradient in the skin. Therefore, CSC has not been optimized for different laser dermatologic surgery procedures. Although it would be desirable to measure in situ human skin temperature, embedding a sensor within 100 μm beneath the skin surface is not feasible. In addition, infrared skin temperature measurement is also not workable because the skin is covered with a cryogen layer of unknown thickness. In this study, we selected an epoxy which has similar thermal properties to that of human skin as our cooling target. Thin-film thermocouples (TFTC) were deposited directly onto the epoxy substrate using micro-fabrication techniques to minimize the thermal contact resistance between TFTC and the substrate. The negligible mass of TFTC also creates a minimal disturbance to heat flow across the surface. Due to the difference in thermoelectric property between thin film and leading wire, special sensor design and calibration procedures were developed. TFTC were calibrated from −46 to 50°C. The thermoelectric sensitivity is around 50–60% of that of bulk material. Skin phantom temperature reductions produced by a commercial medical laser nozzle at different spray durations were measured using the TFTC. The results not only help to elucidate the mechanisms involved in interaction between cryogen spray and human skin but also provide a thermal boundary condition for numerical modeling of laser dermatologic surgery.

scholarly journals Theoretical Study on Cryogen Spray Cooling in Laser Treatment of Ota’s Nevus: Comparison and Optimization of R134a, R404A and R32

Energies ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 5647
Author(s):  
Jiameng Tian ◽  
Bin Chen ◽  
Zhifu Zhou ◽  
Dong Li
Keyword(s):  
Laser Therapy ◽  
Asian Population ◽  
Spray Cooling ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Cold Injury ◽  
Skin Tissue ◽  
Morbidity Rate ◽  
Maximum Surface ◽  
Cryogen Spray Cooling

Cryogen spray cooling (CSC) could be applied clinically for the laser therapy of Ota’s nevus, a dermal hyperplastic pigmented disease with a morbidity rate of 0.1–0.6% in the Asian population. An accurate, efficient, complete simulation system that considers the entire spray cooling process, including cryogen flow in the tube nozzle, spray dynamics and internal phase change heat transfer (cold injury) in skin tissue, was established to determine suitable cryogen and cooling parameters. The optimum spray distances for R134a, R404A and R32 were determined to be 66.0, 43.1 and 22.5 mm, respectively. The corresponding maximum surface heat fluxes were 363.5, 459.9, and 603.6 kW∙m−2, respectively. The maximum surface heat flux of R32 with small spray distance was 1.66 times as large as that of R134a, indicating the potentially good cooling performance and precise targeted cooling of R32 during the laser therapy of Ota’s nevus. The cooling durations that caused cold injury of skin tissue were 2.3, 1.4, and 1.1 s for R134a, R404A, and R32, respectively. The interval between CSC and laser irradiation was optimized to 90–162 ms for R134a, R404A and R32, in consideration of the cooling effect, depth, uniformity, and risk of cold injury.

Dynamic Behavior of Cryogen Spray Cooling: Effect of Spray Distance

2003 ◽  
Author(s):  
G.-X. Wang ◽  
G. Aguilar ◽  
J. S. Nelson
Keyword(s):  
Heat Transfer ◽  
Skin Surface ◽  
Spray Cooling ◽  
Heat Fluxes ◽  
Cooling Effect ◽  
Dermatologic Surgery ◽  
Measured Temperature ◽  
Surface Cooling ◽  
Spray Distance ◽  
Cryogen Spray Cooling

Cryogen spray cooling (CSC) is used to minimize the risk of epidermal damage during laser dermatologic surgery. During CSC, skin surface is cooled by a short spurt of refrigerant R134a with boiling point of −26.2°C. Since R134a is volatile in open atmospheric conditions, the atomized liquid droplets undergo continuous evaporation as they fly in air, leading to a lost momentum and mass. Therefore, the cooling effect of CSC depends strongly on the spray distance between the nozzle and the skin surface (L). The objective of this study was, therefore, to investigate the effect of L on the dynamic heat transfer of CSC. A skin model system made of poly methyl-methacrylate resin (Plexiglass®) is used to simulate CSC during laser dermatologic surgery. A fast-response temperature measurement sensor is built using thin (20 μm) aluminum foil and placed on top of the plexiglass with a 50 μm bead diameter thermocouple positioned in between. Variation of the surface temperature is then measured under various spray distances. The surface heat flux (q) as well as the heat transfer coefficient (h) between the surface and the cryogen is estimated by solving an inverse heat conduction problem with the measured temperature data as input. The effect of L on surface cooling in CSC is then investigated systematically. Both the estimated q and h show strong dynamic characteristics and are strong functions of the L. Two distinct spray-surface interaction mechanisms are identified within the spray distances studied. For short L (< 30 mm), the spurt droplets impinge on the substrate violently, resulting in a fairly thin cryogen film deposited on the surface. Strong dynamics and high q result in this case, corresponding to a high h as well. Interestingly, h becomes strongly fluctuating and even larger after spurt termination for these cases. For long L (> 30 mm), q is lower and it steadily decreases after spurt termination. The dynamic variation of h in this case is similar to that of q. These results should help in the selection of optimal CSC parameters, which are needed to produce high heat fluxes at the skin surface and thus obtain maximal epidermal protection during various dermatologic laser therapies.

Influence of nozzle-to-skin distance in cryogen spray cooling for dermatologic laser surgery

2001 ◽  
Vol 28 (2) ◽  
pp. 113-120 ◽  
Author(s):  
Guillermo Aguilar ◽  
Boris Majaron ◽  
Karl Pope ◽  
Lars O. Svaasand ◽  
Enrique J. Lavernia ◽  
...  
Keyword(s):  
Laser Surgery ◽  
Spray Cooling ◽  
Cryogen Spray Cooling

scholarly journals Radial and temporal variations in surface heat transfer during cryogen spray cooling

2005 ◽  
Vol 50 (2) ◽  
pp. 387-397 ◽  
Author(s):  
Walfre Franco ◽  
Jie Liu ◽  
Guo-Xiang Wang ◽  
J Stuart Nelson ◽  
Guillermo Aguilar
Keyword(s):  
Heat Transfer ◽  
Spray Cooling ◽  
Temporal Variations ◽  
Surface Heat ◽  
Surface Heat Transfer ◽  
Cryogen Spray Cooling
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