Objective Melanin Measurements: Review of Novel Dosimetry Guidance Device for Intense Pulsed Light in Aesthetic Treatments

April 2016 | Volume 15 | Issue 4 | Original Article | 421 | Copyright © 2016

E. Victor Ross MD,a Travis W. Blalock MD,a Douglas Winstanley DO,a Joel L. Cohen MD,b and James J. Childs PhDc

aScripps Clinic, San Diego, CA
bAbout Skin Dermatology and DermSurgery, Denver, CO; University of Colorado, Aurora, CO; University of California Irvine, Irvine, CA
cCynosure, Chelmsford, MA

Abstract

A melanin meter has been created to assess real time skin pigmentation to optimize settings for visible light aesthetic applications.
METHODS: A handheld meter was applied to non sun-damaged skin on the back of volunteers to measure skin pigmentation prior to treatment with IPL light sources over a range of pulse widths and ascending fluences. Curves for maximum epidermal tolerances as a function of pigmentation were determined. These curves were then tabulated for each pulse width in device software to provide guidance in the selection of fluences. Based on these findings, the device was applied in over 300 patients at a comprehensive laser and cosmetic dermatology center.
RESULTS: A pigment meter evaluation led to treatment parameter guidance in intense pulsed light applications. These suggested ranges for settings based on the melanin index score proved useful, accurate, and safe in applications over a broad range of skin colors and across various anatomic units of the skin.
CONCLUSION: A pigment meter can be used to identify appropriate settings with IPL treatments in order to enhance safety and efficacy when treating epidermal pigmented lesions, vessels, general photodamage and excessive hair (where the principles of selective photothermolysis are applied).

J Drugs Dermatol. 2016;15(4):421-432.

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INTRODUCTION

Treatment of excessive hair or cutaneous lesions with laser and light technologies requires wavelength-specific targeting of the primary chromophore(s): water, melanin, or hemoglobin. In clinical practice, the objective is to deliver sufficient energy to maximize destruction/alteration of the target while minimizing injury to adjacent skin.

The array of hair qualities (color and thickness, etc), pigmented lesions, vascular lesions, and native skin colors makes finding a ‘sweet spot’ of optimized treatment parameters somewhat complicated, often becoming easier only through extensive clinical experience with a particular device.   The physician must assess skin melanin content since all visible and near infrared light interacts with melanin in the epidermis. The risk to benefit ratio naturally increases with darker skin types or with low- contrast pigmented lesions (those lesions where the pigment concentrations of the lesion is similar to that of background skin, ie, a lighter colored lentigo). Skin melanin density can vary seasonally and over specific anatomic sites, and cannot be reliably determined by visual assessment because perceived skin color is affected by lighting, skin hydration and underlying hemoglobin.

Physicians have used various methods for assessing melanin density, including Fitzpatrick skin typing (FST). This popular method of characterizing the skin was developed for selection of ultraviolet (UV) doses in psoriasis treatments. The FST protocol characterizes the skin’s response to UV exposure, its relative ability to tan, and risk for sunburn. FST depends on melanin (or, more accurately, the capacity to produce it), but does not quantify the skin’s current melanin density. The FST scale lacks specific identification of actual melanin densities, whose values are important for the selection of safe and optimal treatment parameters. Across patients with the same Fitzpatrick skin type, a large range of melanin densities is observed. Even within the same patient, melanin densities vary with season and anatomic location. None of these factors are included in the FST algorithm. Consequently, clinicians may evaluate immediate skin reactions following test spot treatments to determine best parameters. Even test spots can prove inadequate, as the skin’s response typically evolves over the first 20-30 minutes after a test spot treatment (Figure 1). In the absence of test spots, one may choose conservative settings, which run the risk of inadequate treatment, or in a less desirable scenario, choose too aggressive settings

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