Christine Dierickx

Damage to hair follicles by normal-mode ruby laser pulses

BACKGROUND Although many temporary treatments exist for hirsutism and hypertrichosis, a practical and permanent hair removal treatment is needed. OBJECTIVE Our purpose was to study the use of normal-mode ruby laser pulses (694 nm, 270 microseconds, 6 mm beam diameter) for hair follicle destruction by selective photothermolysis. METHODS Histologically assessed damage in ex vivo black-haired dog skin after the use of different laser fluences was used to design a human study; 13 volunteers with brown or black hair were exposed to normal-mode ruby laser pulses at fluences of 30 to 60 J/cm2, delivered to both shaved and wax-epilated skin sites. An optical delivery device designed to maximize light delivery to the reticular dermis was used. Hair regrowth was assessed at 1, 3, and 6 months after exposure by counting terminal hairs. RESULTS Fluence-dependent selective thermal injury to follicles was observed histologically. There was a significant delay in hair growth in all subjects at all laser-treated sites compared with the unexposed shaven and epilated control sites. At 6 months, there was significant hair loss only in the areas shaved before treatment at the highest fluence. At 6 months, four subjects had less than 50% regrowth, two of whom showed no change between 3 and 6 months. Transient pigmentary changes were observed; there was no scarring. CONCLUSION Selective photothermolysis of hair follicles with the normal-mode ruby laser produces a growth delay consistent with induction of prolonged telogen with apparently permanent hair removal in some cases.

Theoretical considerations in laser hair removal

A systematic and logical approach for laser hair removal demands an understanding of its biologic and physical bases. This article presents an overview of hair anatomy and physiology followed by a mathematically nonrigorous review of tissue optics and thermal responses to laser irradiation. The reader is provided with a step by step approach to laser hair removal.

Micro-fractional ablative skin resurfacing with two novel erbium laser systems

Fractional ablation offers the potential benefits of full‐surface ablative skin resurfacing while minimizing adverse effects. The purpose of this study was to evaluate the safety, damage profile, and efficacy of erbium fractional lasers.

Contact cooling of the skin.

Skin precooling can be used to reduce epidermal thermal damage in laser procedures (such as hair removal) where the target structures are located up to several millimetres below the skin surface. We have developed and experimentally verified a computational model that describes contact precooling of a multilayered skin structure prior to laser irradiation. The skin surface is assumed to be brought into thermal contact with a cold plate made of material with a high thermal conductivity. The approximate analytical solution for the skin temperature is obtained by considering the plate as a local heat sink. The time evolution of temperature (in both the skin and the plate) is simulated numerically to yield the optimal cooling parameters. To experimentally verify the numerical results of the model, we performed direct measurements of skin temperature for contact cooling with a sapphire plate held at several different temperatures in the range +10 to -30 degrees C.

A clinical overview of hair removal using lasers and light sources

The tremendous demand for removal of unwanted hair has led to the development of a wide range of noninvasive, user-friendly laser and light source systems; however, despite considerable advances in this field, these devices still have the potential to cause injury when used improperly. It is important to follow precise treatment guidelines in order to attain optimal results. This article gives an overview of the currently available lasers and light sources. It focuses on the practical aspect of laser hair removal by discussing patient selection, safety precautions, techniques using the different systems, pre- and post-laser treatment care, proper treatment endpoints, expected outcome, and possible side-effects and complications.

Ruby laser hair removal : Evaluation of long-term efficacy and side effects

Although several studies on laser‐assisted hair removal have been published, data on long‐term follow‐up are few. The present study investigated the long‐term efficacy and safety of normal‐mode ruby laser pulses on hair removal.

Visible light treatment of photoaging

ABSTRACT:  Recently, a number of new devices have been developed specifically to improve the visible signs of aging in a noninvasive way. These include visible or near‐infrared lasers, intense pulsed light sources (IPL), light‐emitting diode (LED), and radiofrequency devices. This paper reviews the use of visible light sources and examines the attributes of specific systems for noninvasive skin rejuvenation.

Laser‐assisted hair removal: state of the art

Excessive hair can be a major cosmetic and medical problem. Many temporary hair removal methods exist, including shaving, tweezing, cold and hot wax epilation, and chemical depilatories (1,2). Electrolysis was until recently the only long-lasting method of hair removal. Aside from being tedious, this method is invasive because an electrode is inserted into each follicle. It requires multiple treatments, is usually only partially effective, and regrowth of 15–50% has been reported (3). The need for a rapid, noninvasive method of hair removal has led to the development of various light sources for hair removal. These devices target either an endogenous (melanin) or exogenous (e.g., carbon suspension or photosensitizer) chromophore. A confusing array of devices now exist, along with speculations about their actual performance. These include ruby, alexandrite, diode, and Nd:YAG lasers and intense pulsed light sources. This article focuses on patient selection and treatment protocols for the various systems in order to provide safe and effective treatment.

Reduction of regrowing hair shaft size and pigmentation after ruby and diode laser treatment

Abstract Laser pulses which selectively damage pigmented hair follicles are a useful treatment for hypertrichosis. Clinically, regrowing hairs are often thinner and lighter after treatment. In this study, hair shaft diameter and optical transmission (700 nm) were measured before and after ruby (694 nm) and diode (800 nm) laser irradiation. Hair was collected from ¶47 and 41 subjects treated with ruby (0.3 ms and 3 ms) and diode (10–20 ms) lasers, respectively. “Responders” were defined as subjects with significant long-term hair loss as determined by hair counts at 9 and/or 12 months after treatment. In ruby laser responders (34/47), regrowing hairs were significantly both thinner (decreased diameter) and lighter (increased transmission). In “nonresponders” (13/47), regrowing hairs were lighter, but not thinner. The regrowing hair shaft absorption coefficient (as calculated assuming Beer’s law) was significantly decreased by 0.3 ms ruby laser treatment, but was not changed by 3 ms ruby laser or diode laser treatment. After diode laser treatment, 38 of the 41 subjects were responders and regrowing hairs were both thinner and lighter. These results show that laser treatments can affect structural recovery (size of hair), follicular pigmentation (hair absorption coefficient), or both. Regrowth of thinner hair (decreased shaft diameter) occurs in conjunction with actual loss of hair. After long pulses (3 ms ruby; diode), regrowing hair was thinner and also lighter to an extent related to the decrease in hair diameter. In contrast, short ruby laser pulses (0.3 ms) appeared to be capable of inhibiting follicular pigmentation per se, in addition to affecting the hair diameter. This may account for the complete regrowth of lighter hair in “nonresponders” treated with 0.3 ms pulses. Laser-induced reduction in hair diameter and/or pigmentation are both long-term responses which confer cosmetic benefits in addition to actual hair loss.

Non-ablative fractional laser provides long-term improvement of mature burn scars--a randomized controlled trial with histological assessment.

Non‐ablative fractional laser‐treatment is evolving for burn scars. The objective of this study was to evaluate clinical and histological long‐term outcome of 1,540 nm fractional Erbium: Glass laser, targeting superficial, and deep components of mature burn scars.