Optimal cryogen spray cooling parameters for pulsed laser treatment of port wine stains

Verkruysse, Wim; Majaron, Boris; Tanenbaum, B. Samuel; Nelson, J. Stuart

doi:10.1002/1096-9101(2000)27:2<165::aid-lsm8>3.0.co;2-n

Cited by 74 publications

(66 citation statements)

References 15 publications

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“…Several recent theoretical and experimental studies have suggested that longer cryogen spurt durations ͑200 -300 ms͒ than those used in current clinical practice ͑ϳ60 ms͒ may provide more epidermal protection 5,10 without compromising cooling selectivity. 11 Although CSC has been shown to raise the epidermal damage thresholds in lightly to moderately pigmented skin, 5,7,10 it has not been shown to be effective in protecting the epidermis in dark-skinned individuals. 5 Many mathematical models [12][13][14][15][16][17][18][19][20][21] have been developed for the study of laser therapy in human skin; however, with the exception of a few, 12,21 all models represent the epidermis as a homogeneously absorbing medium, which is not consistent with epidermal anatomy.…”

Section: Introductionmentioning

confidence: 99%

Optimum pulse duration and radiant exposure for vascular laser therapy of dark port-wine skin: a theoretical study

Tunnell¹,

Wang²,

Anvari³

2003

Appl. Opt.

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Laser therapy for cutaneous hypervascular malformations such as port-wine stain birthmarks is currently not feasible for dark-skinned individuals. We study the effects of pulse duration, radiant exposure, and cryogen spray cooling ͑CSC͒ on the thermal response of skin, using a Monte Carlo based optical-thermal model. Thermal injury to the epidermis decreases with increasing pulse duration during irradiation at a constant radiant exposure; however, maintaining vascular injury requires that the radiant exposure also increase. At short pulse durations, only a minimal increase in radiant exposure is necessary for a therapeutic effect to be achieved because thermal diffusion from the vessels is minimal. However, at longer pulse durations the radiant exposure must be greatly increased. There exists an optimum pulse duration at which minimal damage to the epidermis and significant injury within the targeted vasculature occur. For example, the model predicts optimum pulse durations of approximately 1.5, 6, and 20 ms for vessel diameters of 40, 80, and 120 m, respectively. Optimization of laser pulse duration and radiant exposure in combination with CSC may offer a means to treat cutaneous lesions in dark-skinned individuals.

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Section: Introductionmentioning

confidence: 99%

Optimum pulse duration and radiant exposure for vascular laser therapy of dark port-wine skin: a theoretical study

Tunnell¹,

Wang²,

Anvari³

2003

Appl. Opt.

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“…Moreover, extensive clinical use of CSC with exposure of human skin to cryogen spurt durations of 100 ms or more has not resulted in cryo-injury. [4][5][6] Drs. Weisberg and Greenbaum speculate that ''super cooling'' of the distance gauge may be the cause of skin dyspigmentation.…”

mentioning

confidence: 99%

Further Investigation of Pigmentary Changes After Alexandrite Laser Hair Removal in Conjunction With Cryogen Spray Cooling

Kelly

Svaasand

Nelson

2004

Dermatologic Surgery

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“…V was computed using the following analytic equation: ( 4 ) where k = 2×10 -4 kg/m is the air resistivity, y-y 0 = 65 mm was the distance between the nozzle tip and the impact surface, m the droplet mass and g = 9.81 m/s 2 the gravity acceleration constant.…”

Section: Droplet Spread Modelmentioning

confidence: 99%

“…Epidermal melanin absorption of laser light causes localized heating which, if not controlled, may lead to permanent complications such as scarring and dyspigmentation. The risk of non-specific epidermal thermal injury has been effectively minimized by the introduction of skin cooling procedures, such as cryogen spray cooling (CSC) 1, , 2 3 , in which the epidermis is cooled selectively by applying a short cryogen spurt (10-100 ms) onto the skin surface while minimally cooling the deeper targeted chromophores 4 . Shortly after spurt termination a short laser pulse (0.5-40 ms) is aimed at the same area of skin.…”

Section: Introductionmentioning

confidence: 99%

Design and construction of experimental device to study cryogen droplet deposition and heat transfer

2003

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Cryogen spray cooling (CSC) is used to pre-cool the epidermis during laser dermatological procedures such as treatment of port wine stain (PWS) birthmarks. It is known that PWS patients with medium to high epidermal melanin concentrations are at a high risk of epidermal thermal damage after laser irradiation. To avoid this complication, it is necessary to maximize CSC efficiency and, thus, essential to understand the mechanical and thermal interactions of cryogen droplets with the sprayed surface.It has been observed that cryogen sprays exhibit droplet rebound as droplets impinge on the skin surface. Studies of water droplet impact on hard surfaces have shown that droplet rebound may be suppressed by dissolving small amounts (a few percent) of diverse polymer or surfactant solutions prior to atomization. To investigate the possibility of suppressing the rebound of cryogen droplets in a similar way, we have constructed a device that allows observation of the impact, spreading, and rebound of individual water and cryogen droplets with and without these solutions, and their influence on cryogen/surface dynamics and heat transfer. Our preliminary studies show that dissolving a 4% nonionic surfactant in water reduces droplet rebound and thickness of the residual liquid layer. The maximum spread of water droplets after impact can be described within 20% accuracy by a previously developed theoretical model. The same model provides an even more accurate prediction of the maximum spread of cryogen droplets. This study will aid the analysis of future results and design conditions of new studies, which will recreate conditions to determine if added surfactant solutions suppress droplet rebound and lead to improved CSC efficiency.

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Optimal cryogen spray cooling parameters for pulsed laser treatment of port wine stains

Abstract: In the absence of knowledge about the lesion anatomy, using a tau(s) of 100-200 msec and no delay is a good compromise. A delay is justified only when basal layer and target chromophore are relatively deep and the optimal spurt duration cannot be applied, e.g., to avoid frostbite.

Cited by 74 publications

References 15 publications

Optimum pulse duration and radiant exposure for vascular laser therapy of dark port-wine skin: a theoretical study

Optimum pulse duration and radiant exposure for vascular laser therapy of dark port-wine skin: a theoretical study

Further Investigation of Pigmentary Changes After Alexandrite Laser Hair Removal in Conjunction With Cryogen Spray Cooling

Design and construction of experimental device to study cryogen droplet deposition and heat transfer

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