Mathematical modeling of the optimum pulse structure for safe and effective photo epilation using broadband pulsed light

Abstract

The objective of this work is the investigation of intense pulsed light (IPL) photoepilation using Monte Carlo simulation to model the effect of the output dosimetry with millisecond exposure used by typical commercial IPL systems. The temporal pulse shape is an important parameter, which may affect the biological tissue response in terms of efficacy and adverse reactions. This study investigates the effect that IPL pulse structures, namely free discharge, square pulse, close, and spaced pulse stacking, has on hair removal. The relationship between radiant exposure distribution during the IPL pulse and chromophore heating is explored and modeled for hair follicles and the epidermis using a custom Monte Carlo computer simulation. Consistent square pulse and close pulse stacking delivery of radiant exposure across the IPL pulse is shown to generate the most efficient specific heating of the target chromophore, whilst sparing the epidermis, compared to free discharge and pulse stacking pulse delivery. Free discharge systems produced the highest epidermal temperature in the model. This study presents modeled thermal data of a hair follicle in situ, indicating that square pulse IPL technology may be the most efficient and the safest method for photoepilation. The investigation also suggests that the square pulse system design is the most efficient, as energy is not wasted during pulse exposure or lost through interpulse delay times of stacked pulses.PACS number: 87.10.Rt

Review of human hair optical properties in possible relation to melanoma development

“…For this reason, implementing the MC photon simulation to tissues subjected to light with varied wavelengths is challenging. 68,69 To overcome this challenge, Ash et al 69 ran the MC photon simulation simultaneously for each wavelength comprising the spectrum of the broadband light source. In contrast, Sun et al 68 applied a spectrum-intensity-weighted method to estimate the effective absorption and scattering coefficients of the tissues.…”

“…The refractive-indexmismatch of hair and skin was taken into consideration in Ash et al's simulation. 69,70 Theoretically, the MC photon simulation in hair requires the knowledge of its absorption coefficient, scattering coefficient, refractive index, and anisotropy factor. However, it is difficult to experimentally determine all the properties, due to the small size of hair.…”

“…Therefore, the refractive index and anisotropy factor of hair are usually assumed and the hair is often simply modeled as a cylinder in the MC simulation. [67][68][69][70] Hair, like skin, can also be damaged by the UV rays. For example, prolonged sun exposure can cause hair to develop split ends, brittleness, dryness, and color fading through photoaging and photodegradation processes.…”

New lasers and light sources – old and new risks?

“…On the one hand, various device generations are currently being used, with first‐generation devices employing different technologies than subsequent systems (square pulse/free discharge). This affects the stability of the emitted pulse during the application cycle and thus has direct effects on the expected side effect profile . First‐generation IPL devices emit light in the infrared spectrum, often resulting in collateral damage to the epidermis and a high incidence of adverse effects.…”

Neue Laser und Strahlquellen – alte und neue Risiken?

“…Generation andere Technologien als die nachfolgenden Systeme verwenden (square pulse/free discharge). Dies hat Auswirkungen auf die Stabilität des emittierten Pulses während eines Nutzungszyklus des Gerätes und damit unmittelbar auf das zu erwartende Nebenwirkungsprofil . IPL‐Geräte der 1.…”