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International Heat Transfer Conference 15

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

A New Theoretical Model of Selectively Photothermolysis to Aid Laser Treatment of Poor Responding Port Wine Stain Blood Vessels

Dong Li
State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, Xi'an, 710049, China

Bin Chen
State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiao Tong University, No.28 Xianning West Road, Xi'an, Shaanxi, 710049, China

Guo-Xiang Wang
Department of Mechanical Engineering, College of Engineering, The University of Akron, Akron, OH 44325-3903, USA; and State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University

Wenjuan Wu
State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University

Ya-Ling He
Key Laboratory of Thermo-fluid Science and Engineering, Ministry of Education, School of Energy and Power Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China

DOI: 10.1615/IHTC15.ppe.009038
pages 6993-7006


キーワード: Computational methods, phonon and electron transport, Bio and medical applications, Cryogen spray cooling, Laser treatment of PWS, Theoretical model

要約

In laser dermatology, laser treatment of poor responding Port Wine Stain (PWS) lesion is always challenging. Cryogen spray cooling (CSC) was justified to be an effective way to avoid unwanted hyperthermal injury from skin burning and improve the threshold radiant exposure. R134a is now the commercial clinical cooling agent. However, there is still risk of nonspecific thermal injury with R134a spray for darkly pigmented human skin. To quantitatively simulate the cooling of the skin and the heating of the targeted blood vessels in PWSs during laser treatment, a new integrated model is proposed based on the classical homogeneous multi-layer skin model that treats PWS-containing dermis as a mixture of dermal tissue and homogeneously distributed blood. Light propagation in skin and PWSs is simulated by a Monte-Carlo method, which provides accurate description of the light scattering and absorption in the skin. The thermal response of a targeted vessel is obtained from the thermal analysis of a Krogh-unit that consists of the PWS vessel and the surrounding dermal tissues. The results from the multi-layer skin model provide appropriate laser influence input as well as the initial thermal condition for the micro-model of the Krogh-unit. A general dynamic relation is also introduced on the surface of skin to quantify the convective cooling of CSC. With this new model, the thermal responses of the PWS layer and the discrete target blood vessel can be simulated simultaneously. The model is applied to dye-laser treatment (wavelength of 585 nm) of PWSs with CSC. The numerical results showed that deeply located small and large sized blood vessels respond poorly to the laser irradiation due to inefficient and insufficient heating. For treating poor responding blood vessels, variable pulse duration was necessary to increase the thermal response in small blood vessels. On the other hand, prolonging spurt duration was an effective and efficient way to increase heat deposition and improve clearance of large and deep ectatic vessels. Furthermore, using cryogen with lower boiling point (e.g. R407c and R404a) will be a promising way to improve the therapeutic outcome in PWS lesions containing extremely large and deep blood vessels.

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