Premium
Bioheat transfer analysis of cryogen spray cooling during laser treatment of port wine stains
Author(s) -
Pfefer T. Joshua,
Smithies Derek J.,
Milner Thomas E.,
van Gemert Martin J.C.,
Nelson J. Stuart,
Welch Ashley J.
Publication year - 2000
Publication title -
lasers in surgery and medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 112
eISSN - 1096-9101
pISSN - 0196-8092
DOI - 10.1002/(sici)1096-9101(2000)26:2<145::aid-lsm5>3.0.co;2-0
Subject(s) - materials science , laser , irradiation , port wine stain , fluence , pulse duration , optics , analytical chemistry (journal) , biomedical engineering , chemistry , chromatography , medicine , physics , nuclear physics
Background and Objective The thermal response of port wine stain (PWS) skin to a combined treatment of pulsed laser irradiation and cryogen spray cooling (CSC) was analyzed through a series of simulations performed with a novel optical‐thermal model that incorporates realistic tissue morphology. Study Design/Materials and Methods The model consisted of (1) a three‐dimensional reconstruction of a PWS biopsy, (2) a Monte Carlo optical model, (3) a finite difference heat transfer model, and (4) an Arrhenius thermal damage calculation. Simulations were performed for laser pulses of 0.5, 2, and 10 ms and a wavelength of 585 nm. Simulated cryogen precooling spurts had durations of 0, 20, or 60 ms and terminated at laser onset. Continuous spray cooling, which commenced 60 ms before laser onset and continued through the heating and relaxation phases, was also investigated. Results The predicted response to CSC included maximal pre‐irradiation temperature reductions of 27°C at the superficial surface and 12°C at the dermoepidermal junction. For shorter laser pulses (0.5, 2 ms), precooling significantly reduced temperatures in superficial regions, yet did not effect superficial vessel coagulation. Continuous cooling was required to reduce significantly thermal effects for the 10‐ms laser pulse. Conclusions For the PWS morphology and treatment parameters studied, optimal damage distributions were obtained for a 2‐ms laser pulse with a 60‐ms precooling spurt. Epidermal and vascular morphology as well as laser pulse duration should be taken into account when planning CSC/laser treatment of PWS. Our novel, realistic‐morphology modeling technique has significant potential as a tool for optimizing PWS treatment parameters. Lasers Surg. Med. 26:145–157, 2000. © 2000 Wiley‐Liss, Inc.