Thermographic and Histological Evaluation Laser Resurfacing

Research on Science of Cosmetic Lasers

Thermographic and Histological Evaluation Laser Resurfacing

PostPosted by DCNGA » Sat Sep 11, 2010 9:53 am

From 1999. Of course there have been advances with laser resurfacing and skin cooling in the last 10 years, but this remains good information.

The study was not performed on a human subject, but rather a rat.

http://citeseerx.ist.psu.edu/viewdoc/do ... 1&type=pdf

Abstract—In general, ablative laser skin resurfacing procedures have shown good short-term efficacy. However, the mechanisms underlying laser skin resurfacing remain poorly understood. We performed a quantitative study to investigate the thermal response of skin to CO2 laser irradiation. Raster scans were performed on an in vivo rat model and radiometric surface temperatures measured using a thermal camera. Temperatures approaching 400 C were measured during the scans and remained above the initial skin temperature for durations longer than ten seconds. Analysis of histology sections showed that the epidermis remained partially intact after three passes. To explain the observed trends in the temperature response and histology, the dynamics of optical and thermal parameters were investigated. Water vaporization played a key role in governing the response of the skin to subsequent laser passes. Char formation and pulse stacking altered the thermal effects.

A more crucial problem is the highly subjective nature of laser resurfacing. Factors that may lead to disappointing
results or to serious complications include patient-to-patient variability and the dependence on the surgeon’s experience
and technique. An operating protocol used successfully by one physician may prove to be inadequate or deleterious with
another physician; quantitative explanation of any observed discrepancies is difficult.These discrepancies are in part because laser-assisted skin resurfacing is a dynamic thermal event governed by the penetration of laser radiation into the tissue and the rate of heat generated by the absorption of the incident laser light. We believe that a better understanding of the optical and thermal response of skin to CO laser radiation will improve our understanding of clinical results. Any framework for analyzing the thermal response of skin to laser irradiation must include the effects of potential dynamic changes in tissue properties during treatment. Absorption of 10.6- m-wavelength radiation produces a rapid increase in temperature that is a function of the radiant exposure [J/cm of the laser spot and the local optical absorption coefficient [cm ].

Manuscript received December 14, 1998; revised May 21, 1999. This work was supported by the Office of Naval Research Medical Free Electron Laser Biomedical Science Program under Contract N0014-91-J1564, by the Albert W. and Clemmie A. Caster Foundation, by the Air Force Office of Scientific Research through MURI from DDR&E under Contract F49620-98-1-0480,
and by Bio-Medical Consultants, Inc. B. Choi and A. J. Welch are with the Biomedical Engineering Laser Laboratory, The University of Texas at Austin, Austin, TX 78712 USA. E. K. Chan is with Indigo Medical, Inc. Cincinnati, OH 45242 USA. J. K. Barton is with the Biomedical Engineering Program, University of Arizona, Tucson, AZ 85721 USA. S. L. Thomsen is with the Department of Anatomic Pathology, The University of Texas at Austin MD Anderson Cancer Center, Houston, TX 77030 USA
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