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 Evaluation of cryogen spray cooling exposure on in vitro model human skin

2004 ◽  
Vol 34 (2) ◽  
pp. 146-154 ◽  
Author(s):  
Bunsho Kao ◽  
Kristen M. Kelly ◽  
Guillermo Aguilar ◽  
Yoshiaki Hosaka ◽  
Ronald J. Barr ◽  
...  
Keyword(s):  
Human Skin ◽  
In Vitro Model ◽  
Spray Cooling ◽  
Cryogen Spray Cooling ◽  
Vitro Model

Effects of hypobaric pressure on human skin: Implications for cryogen spray cooling (Part II)

2005 ◽  
Vol 36 (2) ◽  
pp. 130-135 ◽  
Author(s):  
Guillermo Aguilar ◽  
Walfre Franco ◽  
Jie Liu ◽  
Lars O. Svaasand ◽  
J. Stuart Nelson
Keyword(s):  
Human Skin ◽  
Spray Cooling ◽  
Cryogen Spray Cooling ◽  
Cooling Part

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.

Methodology for Characterizing Heat Removal Mechanism in Human Skin During Cryogen Spray Cooling

2003 ◽  
Vol 31 (5) ◽  
pp. 493-504 ◽  
Author(s):  
Brian M. Pikkula ◽  
James W. Tunnell ◽  
Bahman Anvari
Keyword(s):  
Human Skin ◽  
Heat Removal ◽  
Spray Cooling ◽  
Removal Mechanism ◽  
Cryogen Spray Cooling

Comparative study of cryogen spray cooling with R-134a and R-404a: implications for laser treatment of dark human skin

2006 ◽  
Vol 11 (4) ◽  
pp. 041116 ◽  
Author(s):  
Tianhong Dai ◽  
Mohammad A. Yaseen ◽  
Parmeswaran Diagaradjane ◽  
David W. Chang ◽  
Bahman Anvari
Keyword(s):  
Comparative Study ◽  
Laser Treatment ◽  
Human Skin ◽  
Spray Cooling ◽  
Cryogen Spray Cooling ◽  
R 134A

scholarly journals Cutaneous Effects of Cryogen Spray Cooling on In Vivo Human Skin

2006 ◽  
Vol 32 (8) ◽  
pp. 1007-1012 ◽  
Author(s):  
NICOLE DATRICE ◽  
JULIO RAMIREZ-SAN-JUAN ◽  
RONG ZHANG ◽  
AZIN MESHKINPOUR ◽  
GUILLERMO AGUILAR ◽  
...  
Keyword(s):  
Human Skin ◽  
Spray Cooling ◽  
Cryogen Spray Cooling

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.

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