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Proceedings Paper

Influence of spraying distance and postcooling on cryogen spray cooling for dermatologic laser surgery
Author(s): Guillermo Aguilar; Boris Majaron; John A. Viator; Brooke Basinger; Emil Karapetian; Lars Othar Svaasand; Enrique J. Lavernia; J. Stuart Nelson
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Paper Abstract

Cryogen spray cooling (CSC) is used to minimize the risk of epidermal damage in various laser dermatological procedures such as treatment of port wine stain birthmarks and hair removal. However, the spray characteristics and combination of CSC and heating (laser) to obtain optimal treatments have not yet been determined. The distance between the nozzle tip and the skin surface for commercial devices was apparently chosen based on the position at which the cryogen spray reached a minimum temperature, presumably with the expectation that such a minimum would correspond to maximal heat flux. We have systematically measured spray characteristics of various nozzles, such as mean droplet diameter, velocity, temperature, and heat transfer coefficient, as a function of distance from the nozzle tip. Among other interesting correlations between these spray characteristics, it is shown that, for nozzle-to-skin distances between 20 to 80 mm, variations in the heat transfer coefficient are larger than those in the spray temperature and, therefore, maximization of the heat flux should be better dictated by the distance at which the heat transfer coefficient is maximized rather than that at which the spray temperature is minimized. Also, the influence of droplet diameter appears to be more influential on the heat transfer coefficient value than that of droplet velocity. Based on spray characteristic correlations, different ranges for positioning the nozzles are recommended, depending on the clinical application. Also, a 2D finite-difference method has been developed to study the spatial and temporal thermal variations within the skin. Our results show that it is possible to decrease significantly the epidermal damage after laser irradiation provided the heat transfer coefficient is significantly increased. The influence of post-cooling has minimal effects for the cases studied.

Paper Details

Date Published: 21 May 2001
PDF: 11 pages
Proc. SPIE 4244, Lasers in Surgery: Advanced Characterization, Therapeutics, and Systems XI, (21 May 2001); doi: 10.1117/12.427778
Show Author Affiliations
Guillermo Aguilar, Whitaker Ctr. for Biomedical Engineering and Beckman Laser Institute and Medical Clinic (United States)
Boris Majaron, Beckman Laser Institute and Medical Clinic and Jozef Stefan Institute (Slovenia)
John A. Viator, Beckman Laser Institute and Medical Clinic (United States)
Brooke Basinger, Beckman Laser Institute and Medical Clinic (United States)
Emil Karapetian, Univ. of California/Irvine (United States)
Lars Othar Svaasand, Beckman Laser Institute and Medical Clinic and Norwegian Univ. of Science and Technology (Norway)
Enrique J. Lavernia, Univ. of California/Irvine (United States)
J. Stuart Nelson, Whitaker Center for Biomedical Engineering and Beckman Laser Institute and Medical Clinic (United States)


Published in SPIE Proceedings Vol. 4244:
Lasers in Surgery: Advanced Characterization, Therapeutics, and Systems XI
Lawrence S. Bass; David S. Robinson; Eugene A. Trowers; Kenton W. Gregory; Lou Reinisch; Kenneth Eugene Bartels; R. Rox Anderson; Reza S. Malek; Kenneth Eugene Bartels; Lloyd P. Tate; Abraham Katzir; C. Gaelyn Garrett; Timothy A. Woodward; Hans-Dieter Reidenbach; George M. Peavy; Lawrence S. Bass; C. Gaelyn Garrett; Michael D. Lucroy; Kenton W. Gregory; Abraham Katzir; Nikiforos Kollias; Michael D. Lucroy; Reza S. Malek; J. Stuart Nelson; George M. Peavy; Hans-Dieter Reidenbach; Lou Reinisch; David S. Robinson; Lloyd P. Tate; Eugene A. Trowers; Timothy A. Woodward, Editor(s)

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