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International Journal of Thermophysics

, Volume 34, Issue 8–9, pp 1549–1558 | Cite as

Influence of the Sampling Rate and Noise Characteristics on Prediction of the Maximal Safe Laser Exposure in Human Skin Using Pulsed Photothermal Radiometry

  • L. Vidovič
  • M. Milanič
  • B. Majaron
Article

Abstract

Pulsed photothermal radiometry (PPTR) allows for noninvasive determination of the laser-induced temperature depth profile in strongly scattering samples, including human skin. In a recent experimental study, we have demonstrated that such information can be used to derive rather accurate predictions of the maximal safe radiant exposure on an individual patient basis. This has important implications for efficacy and safety of several laser applications in dermatology and aesthetic surgery, which are often compromised by risk of adverse side effects (e.g., scarring, and dyspigmentation) resulting from nonselective absorption of strong laser light in epidermal melanin. In this study, the differences between the individual maximal safe radiant exposure \((H_{\mathrm{max}})\) values as predicted from PPTR temperature depth profiling performed using a commercial mid-IR thermal camera (as used to acquire the original patient data) and our customized PPTR setup are analyzed. To this end, the latter has been used to acquire 17 PPTR records from three healthy volunteers, using 1 ms laser irradiation at 532 nm and a signal sampling rate of 20 000  \(\mathrm{s}^{-1}\). The laser-induced temperature profiles are reconstructed first from the intact PPTR signals, and then by binning the data to imitate the lower sampling rate of the IR camera (1000 fps). Using either the initial temperature profile in a dedicated numerical model of heat transfer or protein denaturation dynamics, the predicted levels of epidermal thermal damage \((\varOmega )\) and the corresponding \(H_{\mathrm{max}}\) are compared. A similar analysis is performed also with regard to the differences between noise characteristics of the two PPTR setups.

Keywords

Infrared detection Noise characteristics Pulsed photothermal radiometry Sampling rate Temperature depth profiling 

Notes

Acknowledgments

The authors thank Fotona d.d. (Ljubljana, Slovenia) for lending the laser system for use in this study.

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Copyright information

© Springer Science+Business Media New York 2013

Authors and Affiliations

  1. 1.Jožef Stefan InstituteLjubljanaSlovenia
  2. 2.Faculty for Mathematics and PhysicsUniversity of LjubljanaLjubljanaSlovenia

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