Computational investigation on thermal responses of blood vessels during laser treatment of port wine stain

Abstract

Purpose – The purpose of this paper is to present a numerical analysis of the laser surgery of port wine stain (PWS) with cryogen spray cooling to compare the treatment effect between pulse dye laser and Nd:YAG laser, explain the incomplete clear of the lesion and optimize the laser parameter. Design/methodology/approach – The complex structure of skin and PWS is simplified to a multi-layer skin model that consists of top epidermal layer and underneath dermis layer embedded with discrete blood vessels. The cooling effect of cryogen spray before laser firing is quantified by a general correlation obtained recently from the experimental data. The light distribution is modeled by the Monte Carlo method. The heat transfer in skin tissue is calculated by Pennes bioheat transfer model. The thermal damage of blood vessel is quantified by the Arrhenius damage integral. Findings – For the vessel size studied (10-120 µm), pulse duration is recommended shorter than 6 ms. Large and deeply buried vessels, which may survive from 595 nm laser irradiation, can be coagulated by 1,064 nm laser due to its deep light penetration depth in skin. Furthermore, a desired uniform heating within the large vessel lumen can be achieved by 1,064 nm laser whereas 595 nm laser produce non-uniform heating. Originality/value – The possible reason for the poor responding and incomplete clearance lesions is clarified. Laser wavelength and pulse duration are suggested to improve the clinical results.

Successful Treatment of Reticular Blue Veins of the Lower Eyelid by Long-Pulse Nd: YAG – Case Report with 8-Year Follow-Up

“…In vitro experiment found that vessel constriction was due to the constriction of thrombus induced by laser irradiation. The theoretical investigation revealed that the mechanism for the effective reduction of energy density by multi-pulse Nd: YAG laser was due to enhanced light absorption of the blood with thrombus formation [ 9 ][ 10 ].…”

Numerical simulation of ophthalmic laser surgeries by a local thermal non-equilibrium two-temperature model

“…To solve these problems, a local thermal non-equilibrium theory of porous media, which had been successfully established in our previous study on the laser therapy of port wine stain (Li et al, 2016), was applied for the investigation of ophthalmic laser surgery. The fundus tissues were considered as a porous solid skeleton, and the chromophores (melanin and hemoglobin) were considered as the media filled in the pore space.…”

Enhancement of light absorption by blood to Nd:YAG laser using PEG‐modified gold nanorods

“…Thus, a millisecond‐pulsed 1064 nm Neodymium:Yttrium Aluminum Garnet (Nd:YAG) laser has great potential in the treatment of deeper PWSs. The advantage of the Nd:YAG laser over PDL is weak absorption of epidermal melanin and water , as well as deeper penetration due to the longer wavelength that permits increased light penetration into the dermis . Nevertheless, the thermal response of deep and large blood vessels to the 1064 nm Nd:YAG laser is weaker than PDL because of the lower absorption of hemoglobin, which should be enhanced to improve its clinical effectiveness.…”