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This paper aims to understand the laser–tissue interaction mechanism during ophthalmic laser surgeries through numerical analysis. The influence of laser parameters and the multipulse technique were investigated.

The ocular fundus was simplified as a multilayered homogenous medium model. Afterward, the multilayer Monte Carlo method was used to simulate the propagation and energy deposition of laser light, and a local thermal non-equilibrium two-temperature model was established to simulate the temperature variation of chromophores and surrounding tissue with different laser wavelength.

Through the model, the selective heating of chromophore (melanin and blood vessels) was clearly illustrated: 1) neglecting the laser energy absorbance by blood in the traditional model will cause significant errors in temperature calculation; 2) the non-thermal equilibrium heat transfer model was needed to obtain an accurate description of the thermal process when the dimensionless pulse width (tp*) is <10⁵. For 532 nm Argon laser, the optimize tp* is around 10⁵ and the appropriate energy density is 5 J/cm²; 3) multipulse technique makes the energy more concentrated within the melanin, thereby reducing the thermal damage in surrounding tissue, with most appropriate pulse number and duty cycle is 10 and 1/10.

Taking the blood absorption into account, the different temperature variations of melanin/vessels and surrounding tissue caused by the selective photo-thermolysis were simulated successfully. By understanding the mechanism of laser therapy, laser parameters and multipulse technique are suggested to improve the clinical results.

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.

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.

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.

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.

The purpose of this paper is to describe a sustainable free laser tattoo removal clinic for economically disadvantaged adult probationers.

This paper describes the partnerships, methods and challenges/lessons learned from the implementation of a free monthly laser tattoo removal program for adult probationers within a medical school setting in California.

Possible patients are identified via a collaboration with the county’s Probation Department. Founded in 2016, this monthly program has provided tattoo removal services to >37 adult patient probationers, many of whom receive follow-up treatments. Clients seek to remove about four blue/black ink tattoos. Since its inception, 23 dermatology residents have volunteered in the program. Challenges to patients’ ongoing participation primarily pertain to scheduling issues; strategies for overcoming barriers to participation are provided. No safety concerns have emerged.

Programs such as this public-private partnership may benefit probationers by eliminating financial barriers associated with tattoo removal. This model supports the training of cohorts of dermatologists seeking community service opportunities related to laser medicine. Others seeking to implement a similar program may also consider expanding treatment days/times to facilitate access for working probationers, providing enrollment options for other health and social services (e.g. public insurance, food stamp programs) and hosting a mobile onsite clinic to address clients’ physical and mental health needs.

This paper describes a unique collaboration between law enforcement and a medical school and it may assist other jurisdictions in establishing free tattoo removal programs for the benefit of probationers. The methods described overcome challenges regarding the implementation of this specialized clinical service.