Light and Heat Energy (LHE ) Technology Review of a Novel Approach to Hair Removal

Transcription

1 Light and Heat Energy (LHE ) Technology Review of a Novel Approach to Hair Removal Yosef P. Krespi, M.D., St. Lukes Roosevelt Hospital, 425 West 59 th Street, 10 th Floor New York, NY Alex Levenberg, M.D., Beit Ha rofeem Plastic Surgery Clinic June 2003 Abstract: Light-based hair removal is a multi-factorial process that involves complex photothermal reactions through the epidermal-dermal layers, aimed to cause follicle damage. To achieve this, current laser and IPL technologies utilize intense light energy levels which require application of skin cooling techniques in order to avoid thermal damage to the epidermis and ensure patient comfort. Radiancy s pulsed light and heat energy (LHE ) patented technology enables the use of low light energy levels to achieve the desired follicle damage without the risk of potential adverse side effects. Heat originating from the light unit assembly mounted on the handpiece is conducted down the hair shaft INTRODUCTION Light-based hair removal is a multi-factorial process that involves complex photothermal reactions through the epidermal-dermal layers, aimed to cause follicle damage[1-4]. Light parameters are carefully considered and critically selected to achieve effective, long lasting damage to the follicle while avoiding adverse side effects to the surrounding skin. Based on the theory of selective photothermolysis[5] wavelengths are chosen for maximum absorption in the melanin which is the targeted chromophore, while pulse durations are set to minimize epidermal heating as well as thermal diffusion from the heated follicle. Ideal candidates for laser and IPL hair removal are those with fair skin and dark, coarse hair. In practice, however, most candidates possess a significant amount of melanin in their skin and desire removal also of lighter, thinner hair. Under these conditions the effectiveness of the basic selective photothermolysis theory diminishes to the point where auxiliary skin cooling techniques become mandatory to avoid undesirable thermal damage to the epidermis[6-7].most current laser and IPL hair removal systems employ intense light fluence combined with various skin cooling technique such as a contact, cooled sapphire window[8] or a burst of evaporative coolant[9] delivered just prior to the laser/light pulse, to avoid adverse side effects. While adding to the cost and complexity of such systems, these cooling techniques are also operator dependent and may compromise safety. Since selective conversion of light energy to follicular heat is an inefficient process, Radiancy has developed a novel approach of simultaneously utilizing two different energy pathways, light and heat[10], in order to prevent potential adverse side effects without using any cooling mechanism. during and following the delivery of the light pulse. The combined light and heat effect raises the follicle s temperature to the required coagulation level of ~ 85 0 C while maintaining the surrounding epidermal temperature below the necrosis threshold of ~ 60 0 C, without the use of any auxiliary skin cooling technique. The use of LHE technology facilitates an effective, safe, compact, and cost-effective system. This paper describes the technology utilized by Radiancy s LHE-based hair removal system, and reviews studies results which demonstrate clinical equivalency to existing laser and IPL hair removal devices. By applying its patented LHE technology, rather than intense light energy, and simultaneously optimizing wavelength, pulse duration, and spot size, Radiancy s hair removal system achieves safe and effective hair removal without utilizing any skin cooling mechanism. THE LHE CONCEPT: The traditional photoepilation process, applied by lasers and IPL systems, is based on the principle of selective photothermolysis. According to this well known principle, pulsed light treatment parameters are chosen to selectively injure the hair follicles without damaging the surrounding tissue. Special consideration applies for the destruction of hair follicles since the target chromophore is melanin and the pulse light has to penetrate through the overlying skin, which also contains melanin. In contrast to lasers and IPL systems which apply intense light energy, block the heat generated by the light source, and include various cooling methods in order to prevent adverse side effects, LHE uses dual light and heat energy pathways, allowing safe temperature margin on the skin without the need for cooling means. Since lasers and IPL systems block the heat normally generated in the process of emitting light pulses, such systems are required to deliver to the targeted area intense light energy of more than 25 J/cm 2 to effectively damage the hair follicle and raise the follicle s temperature to the required coagulation level. Such intense light energy without appropriate cooling raises the temperature of the surrounding epidermis well above the necrosis threshold to a temperature of more than C [11]. In order to avoid adverse side effects and maintain patients comfort a cooling mechanism has to be incorporated in such lasers and IPL systems.

2 2 LIGHT AND HEAT ENERGY (LHE ) TECHNOLOGY REVIEW OF A NOVEL APPROACH TO HAIR REMOVAL Hair follicle damage can be more safely and efficiently achieved by combining the effects of selective light absorption in the follicular melanin with direct conduction of heat through the skin and the hair shaft down to the follicle. A typical system powered by LHE uses optical fluence of 2 10 J/cm 2 which is only 15% of the total electrical energy used by the LHE system. The total fluence delivered to the skin is composed of the optical fluence and the heat energy resulting in effective J/cm 2 energy fluence for hair removal. As opposed to light energy that heats the epidermis along with the hair shaft and hair follicles, and is absorbed in both the epidermal and follicular melanin, heat energy provides a better direct conduction of heat through the hair shaft down to the follicle without raising the skin temperature to extreme and unsafe levels[12]. The temperature rise of the epidermis is different than the temperature rise of the hair shaft and follicle since they possess different heat capacity and conductivity. The hair shaft differently than the epidermis, possess a low water content and therefore provides for high heat conductivity and low heat capacity, allowing efficient transfer of heat energy down to the follicle at a rate of approximately 3.5 m/sec.. The combined light and heat effect raises the follicle s temperature to the required coagulation level of ~ 85 0 C while maintaining the surrounding epidermal temperature below the necrosis threshold of ~ 60 0 C without the use of any auxiliary skin cooling technique. Figure 1: The role of light and heat in photoepilation WAVELENGTH BAND Hair derives its natural color from melanin. Melanin is present in the hair shaft, the hair matrix, the infundibulum and sparsely in the outer root sheath layer. Fair hair (blonde, gray, white) has a decreased number of melanocytes in the hair bulb compared to dark hair. Nicholls[13] found that the absorption coefficient of black hair at 440 nm is approximately two times greater than the absorption coefficient of black hair at 650nm, and approximately four times greater than the absorption coefficient of blond hair at 440nm and 650nm. The LHE system uses a unique wavelength band of 400 to 1200nm to allow a better absorption of the light in the hair shaft and follicle and provide effective hair removal. Figure 2: Light Absorption as a Function of Wavelength PULSE WIDTH Light energy is absorbed in the epidermal melanin as well as in the hair melanin. However, the temporal characteristics of these mechanisms are quite different[14]. The epidermis being a thin layer with a greater surface to mass ratio than the hair follicle, has a low thermal relaxation time of 3-7 msec. The hair follicle, in contrast, has a longer thermal relaxation time in the order of 100 msec. The LHE hair removal system utilizes a light pulse of 35 msec which is sufficiently long for the epidermis to dissipate the absorbed energy yet short enough for the follicle to fully retain the absorbed light energy and transform it into heat (see figure 1: The role of light and heat in photoepilation). In addition, during and following the delivery of the 35 msec light pulse, the system delivers heat energy to both the epidermis and the hair shaft. As explained above, the temperature rise of the epidermis and the hair shaft and follicle is different since they possess different heat capacity and conductivity. The use of heat energy in addition to the use of specific pulse width further allows an effective follicular necrosis while sparing surrounding skin from any adverse effects. SPOT SIZE The geometry of optical energy delivered to the skin is important in the process of hair removal. When light interacts with the skin a scattering process occurs. If a small spot size is used the scattering process diffuses the beam rapidly and the penetration depth is minimal (see figure 3). On the other hand, if the light is delivered via a large aperture the beam is kept in a well defined

3 3 LIGHT AND HEAT ENERGY (LHE ) TECHNOLOGY REVIEW OF A NOVEL APPROACH TO HAIR REMOVAL pathway that penetrates deep into the skin (see figure 4). The LHE system uses a very large spot size of 22 x 55 mm, thus ensuring deep penetration of the energy into the hair follicle. Figure 3: Energy delivery via a small spot size hair and lack of effect on the surrounding tissue. Typical desired endpoints are bleaching or singing/burning of the hair, perifollicular erythema, and lack of any adverse side effects such as erythema in the shape of the aperture, or blistering. Treatments are preferably performed with the hair shaved, leaving an area with trimmed hair in order to better evaluate the immediate response to the system s parameters setting. Figure 5 is a picture taken by a microscope with an enlargement of X200 immediately after treatment. The picture depicts the results of transferring the heat generated in the hair shaft down to the follicle. The light and heat bleached the hair completely. The hair shaft becomes thicker due to the evaporation of free water molecules inside the shaft, resulting in a high temperature stream heating the hair bulb. Figure 4: Energy delivery via a large spot size SYSTEM DESCRIPTION AND OPERATION The LHE system is a compact table-top device, containing two low fluence flash lamps which emit light at a wavelength band of nm. This broad spectral range accommodates removal of hair of different colors and follicles of different depths[15-18].the lamps are housed in a light unit assembly that directs both light and heat generated by the flash lamps via the aperture. This aperture defines a very large effective spot size of 22x55 mm allowing deep penetration by reducing light energy loss due to photon scattering in the skin[19]. Using a single, simple, analog control knob, the optical fluence can be adjusted within the range of 2-10 J/cm 2 corresponding to J/cm 2 effective fluence level. Fluence is displayed in percentage of maximum output. As with any laser or IPL hair removal treatment[20-22], initial system settings are based on manufacturer s recommendations or user s experience, in accordance with the patient s skin type, hair color, coarseness and density. The light unit assembly is fitted with hygiene ring for hygiene purposes. A pulse is triggered by pressing the footswitch and simultaneously activating one of two available pulse switches located on the handpiece. Upon emission of the light pulse the handpiece should be left in contact with the treated area approximately 1 to 2 seconds to assure the full effect of the heat energy process. Optimal settings are judged by the thermal effect on the Figure 5: Immediate results bleached hair Figure 6 depicts the resulting coagulation of the hair follicle. Since the temperature of the shaft and follicle is higher than the coagulation temperature, the follicle coagulates ad covers the hair shaft and bulb with thin coagulated layer. Figure 6: Immediate results coagulation of the hair follicle For effective non-invasive hair removal, it is necessary to damage the hair follicle during its active cycle of hair growth. Thus, the time between treatments should be as similar as possible to the length of the telogen phase. The duration of the resting period for hair follicles depends on the anatomical location (see Table 1). Therefore, the time between consecutive treatments should be determined according to the treated area. It should be noted that the time parameters in table 1 are statistical and may vary between individuals due to

4 4 LIGHT AND HEAT ENERGY (LHE ) TECHNOLOGY REVIEW OF A NOVEL APPROACH TO HAIR REMOVAL differences in age, hormonal activity and ethnicity. Body Site Telogen (Months) Anagen (Months) Back Bikini Arm Calf Axilla Upper lip Table 1: Hair follicles growth cycle To achieve successful hair reduction results using LHE technology, multiple treatments are performed at intervals of 1 month up to 3 months, depending on hair re-growth. Usually 4 to 10 treatments may be required for satisfactory hair reduction, depending on the particular patient and anatomical location. When setting patients expectations it is important to explain that LHE technology usually produces a complete temporary hair removal followed by permanent hair reduction, which means reduction in the amount of re-growing hair. Once a patient completes the treatment regimen the regrowing hairs are lighter and thinner than before providing a significant cosmetic improvement. CLINICAL RESULTS In the past few years a few clinical studies were performed in order to evaluate the performance of Radiancy s LHE technology. Yosef Krespi, MD of St. Lukes Roosevelt Hospital in New York conducted a single treatment study designed to evaluate clinical safety and efficacy of the LHE system. Thirty nine (39) adults with Fitzpatrick skin types I-IV and various hair colors were enrolled in the study. Each participant was treated on one or two different areas (leg, arm, face or bikini line). Photographs were taken before treatment, 30 minutes after treatment and in each follow-up visit. Follow up visits were conducted every two weeks, up to twelve weeks post treatment. Hair counts were taken directly from the photographs by two independent evaluators. Additionally, during follow-up visits the investigator evaluated the degree of hair reduction and assessed the treatment effects as well as any side effects. The investigator evaluated cosmetic improvement on a scale of 0-5 (no improvement to excellent improvement) and participants ranked their level of satisfaction. The average hair clearance stabilized at approximately 50% at week 2 up to week 10 and decreased to 35% at week 12. In addition to this statistically significant hair clearance, treatment showed qualitative reduction in hair diameter and lightening of hair re-growth. According to the investigator s evaluation approximately 85% of all treated sites exhibited good to excellent cosmetic improvement. Erythema was the most common side effect which occurred in 72% of the treated sites and resolved from within a few hours up to 5 days post treatment. Crusting which resolved within 2 weeks post treatment was reported in 8% of the treated sites. Maurice Adatto, MD of the Skinpulse dermatology center in Geneva, Switzerland conducted a multiple treatments study with a long term follow-up. Dr. Adatto[23], treated 21 patients of skin types II and III with dark, coarse hair mainly on the back or chest for males and the bikini/axilla area for females. Each patient over went 4 to 9 treatments. The average percentage of hair reduction 3 to 6 months after the last treatment was 58% for males and 73% for females. As expected, the anatomical sites treated on females responded better than those treated on males, and required, on average, fewer sessions (5.53 vs. 7.5 treatments). Side effects were minor and transient and included erythema for up to two days after treatment and a few crusted areas where hair was very dark and coarse. These crusts fell off within a few days with no pigmentary changes. In a study conducted by Thomas E. Rohrer, MD [24] 27 patients with skin types I-IV, were treated in the axillary or bikini area. In this study the superior aspect of each site was treated while the inferior aspect was left untreated as a control. Patients over went three treatments with one month interval between each treatment. Follow ups were performed up to nine months following the third treatment. An average hair count reduction of 54.9% was achieved nine months following the last treatment. There were minimal side effects and virtually no complications following the treatments. No pigmentary changes, scarring or prolonged erythema were apparent. Crusting occurred in 0.8% of the cases but quickly resolved with no medical intervention. The clinical results demonstrate delay in hair growth and permanent hair reduction. The single treatment study showed delay in hair growth which sustained up to 12 weeks following a single treatment. The multiple treatments studies conducted by Dr. Addato and Dr. Rohrer showed hair clearance of more than 50% 6 to 9 months following the final treatment. Thus, the two long term studies demonstrate statistically significant permanent hair reduction which is stable for a longer period of time than the complete growth cycle of follicles at the treated areas. CONCLUSION The clinical studies reviewed in this paper

5 5 LIGHT AND HEAT ENERGY (LHE ) TECHNOLOGY REVIEW OF A NOVEL APPROACH TO HAIR REMOVAL demonstrate that Radiancy s LHE hair removal system provides the same long term hair removal results as existing laser and IPL hair removal systems, while maintaining a safety margin which is superior to the safety margins provided by traditional technologies. The studies show hair clearance of more than 50% six to nine months following the final treatment, with only minor side effects such as erythema that resolved within a few hours up to a few days post treatment. It is well established that LHE technology eliminates the need for any cooling methods and enables safe and effective hair removal treatments using a compact and affordable device. References: 1. Grossman MC, et al. Damage to hair follicles by normal-mode Ruby laser pulses. J. Am. Acad Dermatol 1996;35: Lask G., et al. The role of laser and intense light sources in photo-epilation:a comparitive evaluation. J. Cutan Laser Ther 1999;1: Liew SH. Unwanted body hair and its removal: A review. Dermatolol Surg 25:6:June 1999, pp Olsen EA. Methods of hair removal. J. Am. Acad Dermatol 1999 Feb;40 (2 Pt 1): Anderson RR, Parish JA. Selective photothermolysis: Precise microsurgery by selective absorption of pulse radiation. Science 1983;220: Anderson RR. Lasers in dermatology-a critical update. J. Dermatol 2000 Nov, 27(11): Alora MB, Anderson RR. Recent developments in cutaneous lasers. Lasers Surg Med 26: (2000). 8. Klavuhn KG, Green D. Importance of cutaneous cooling during photothermal epilation: theoretical and practical considerations. Lasers Surg Med 2002;31(2): Nelson JS, et al. Dynamic epidermal cooling during pulsed laser treatment of port wine stain-a new methodology with preliminary clinical evaluation. Arch Dermatol 1995;131: Goldberg DJ, Silapunt S. Hair removal with a combined light/heat based photoepilation system. J. Cutan Laser Ther 2001;3: Lask G, Elman M, Slatkine M, Waldman A, Rozenberg Z. Laser-assisted hair removal by selective photothermolysis. Dermatol Surg. 1997; 23: Lawrence Iwaki, et. al. Growth Inhibition and Transient Temperature Measurement of Laser- Irradiated Hair Fibers and Follicles, Optical Technology Division, NIST, Private communication 13. Nicholls EM. The genetics of red hair. Hum Hered 1969; 19: Van Gemert MGC, Welch AJ. Time constant in thermal laser medicine. Laser Surg. Med. 1989;940: Gold MH, et al. Long-term epilation using the Epilight broad band intense pulsed light hair removal system. Dermatol Surg. 1997;23: Sadick NS, et al. Long-term photoepilation using a broad-spectrum intense pulsed light source. Arch Dermatol 2000 Nov; 136(11): Weiss RA, Weiss MA. Hair removal with the Epilight system, in Keller GS ed. Lasers in Aesthetic Surgery. Thieme 2001, chap. 25, pp Troilius A, Troilius C. Hair removal with a second generation broad spectrum intense pulsed light source-a long-term follow-up. J. Cutan Laser Ther 1999;1: Reimisch L. Scatter-limited phototherapy: a model for laser treatment of skin. Lasers Surg. Med. 2002;30(5): Liew SH. Laser hair removal: guidelines for management. Am. J. Clin Dermatol 2002;3(2): Dierickx CC. Hair removal by lasers and intense pulsed light sources. Dermatol Clin 2002 Jan; 20(1): Goldberg DJ. Laser hair removal. Dermatol Clin 2002 Jul; 20(3): Adatto MA. Hair removal with a combined light/heat based photoepilation system: an 18 month experience. To be published. 24. Rohrer TE, Touma DJ, Evaluating the safety and efficacy of a novel light based hair removal system. Laser Surg. Med.; (suppl. 13): 24

6 6 LIGHT AND HEAT ENERGY (LHE ) TECHNOLOGY REVIEW OF A NOVEL APPROACH TO HAIR REMOVAL Radiancy, its logo and LHE are all trademarks of Radiancy Inc. 40 Ramland Road South, Suite10 Orangeburg, New York 10962, USA Tel: , Fax: , Toll Free: Visit the Radiancy website at: Radiancy Inc. / / June 2003