Derrnatologic Laser Surgery

Derrnatologic Laser Surgery Wendy W. Lou, MD, and Roy G. Geronemus, MD

A DVANCES IN TECHNOLOGY have made lasers an important presence in the practice of

medicine. Lasers have become a critical part of dermatology providing the treatment of choice for many dermatologic conditions. As a consequence of the therapeutic advances provided by lasers, clinicians today should have an overall understanding of laser applications and should keep abreast with the advances in this field.

After a brief introduction on laser history and physics, clinical applications of lasers will be presented in detail. Four main topics will be the fo- cus: vascular lesions, pigmented lesions, resurfacing, and hair removal.

LASER H I S T O R Y

The concept of light amplification by stimulated emission of radiation (LASER) light produc- tion was first proposed by Albert Einstein in 1917 in The Quantum Theory of Radiation. About 40 years later, Townes and Gordon actually built a system producing monochromatic radiation by stimulated emission with microwaves--MASER (microwave amplification by stimulated emission of Radiation). The first LASER was developed by Maiman in 1960 by using ruby crystals and flashlamps. It is no surprise that the field of dermatology leads the advancement of laser technology because skin is one of the most accessible organs for laser effects.

A dermatologist, Goldman, was the first to pub- lish his finding of ruby laser treatment of the human skin in 1963. Subsequently, a number of continuous-wave lasers were developed: argon (488 nm, 514 nm), carbon dioxide (10,600 nm), and neodynium:yttrium-aluminum-garnet (Nd:YAG) (1064 nm). There was initial enthusiasm in the 70s until it became clear that treatments were frequently associated with high risk-to-benefit ratio. Because of the nonspecific tissue injury from these continuous-wave lasers, the incidence of scarring was particularly high. Thus, the popularity of this group of lasers declined for those conditions with alternative treatment options or for those that would improve during natural course of disease, such as hemangiomas.

In 1983, Anderson and Parrish presented the

theory of selective photothermolysis~ which launched a new era in laser technology. With a better understanding of laser-tissue interaction, lasers are developed with specific tissue effects in mind. The first laser developed in accordance with this theory was the flashlamp pumped pulsed dye laser, which has revolutionized the treatment of vascular lesions. Since then, other lasers have been designed and applied in the similar manner. Because of the selective nature of tissue injury, this new generation of lasers has very low incidence of long-term side effects if used appropri- ately. Today, lasers often provide a favorable alternative to traditional nonlaser treatment options for a rapidly expanding list of dermatologic conditions.

LASER P H Y S I C S

Laser light is a type of electromagnetic radiation, which is a form of energy that has properties of both waves and discrete particles of energy called photons. Electromagnetic radiation is often categorized according to wavelengths: gamma rays, x-rays, ultraviolet rays, visible light, infrared radiation, microwaves, and radio waves. The spectrum of light used in dermatologic lasers is in the visible and infrared wavelength range (400 nm to 10,600 nm).

The term LASER is an acronym for light amplification by stimulated emission of radiation, the mechanism by which such light is produced. Elec- trons of an atom or molecules normally orbit in the resting state or the lowest energy state. These electrons may absorb certain set amounts of energy in the form of photons and may be risen to an excited state at a higher energy orbit. Such electrons at the excited state are relatively unstable and may spontaneously return to their resting state by discharging photons of light containing the same amount of energy as initially absorbed. Such occurrence is termed spontaneous emission of

Reprinted from Current Problems in Dermatology 13(1):5-24, 2001 with permission.

Copyright 2001, Elsevier Science (USA). All rights reserved. 1085-5629/02/2102-0002535.00/0 doi: l O. 1053/sder.2002.33286

Seminars in Cutaneous Medicine and Surgery, Vol 21, No 2 (June), 2002: pp 107-128 107

108 LOU AND GERONEMUS

radiation. If an already excited electron absorbs a photon of light, it will emit two photons of light when it falls back to its resting state. These two photons will have the same energy and wavelength and will be spatially and temporally in phase with each other. This is called stimulated emission of radiation. Because most of the electrons are normally in the resting state, stimulated emission occurs rarely. However, if external energy is supplied so that most of the electrons in the lasing cavity are in excited states, the chance of stimulated emission is much higher. The state in which most electrons are in the excited state is called population inversion.

The laser apparatus has 3 essential components. The pumping system is the external energy source. The lasing medium (gain medium) sup- plies the electrons necessary for emitting laser radiation and determines the wavelength of such radiation. The medium may be a gas, such as argon, carbon dioxide, and copper vapor; a liquid, such as tunable dye; or a solid, such as ruby, alexandrite, diode, Nd:YAG, and erbium:yttrium-aluminum-garnet (Er:YAG). The optical resonator (optical cavity, lasing cavity) contains the lasing medium and has two parallel, opposing mirrors, one of which is partially reflective. Photons of light travel back and forth between the mirrors while stimulating emission of more photons of light that are in phase. Finally, some photons of light exit the cavity through the partially reflective mirror and make up the laser beam.

Laser light is generated in a manner that gives it characteristic properties common to all laser beams. Light from a laser is monochromatic, that is, of one wavelength or a very narrow band of wavelengths. The wavelength is characteristic of the particular lasing medium used. This mono- chromacity allows selective absorption by specific chromophores, thus affecting only selective tis- sues. Laser light is also temporally and spatially coherent, meaning that the emitted waves are in phase both in time and space. Such coherence results in a collimated, unidirectional beam of light which is critical to the proper delivery of the laser beam from the optical cavity to the target tissue without much divergence. A collimated beam has the same spot size regardless of how far the tissue is from the handpiece. However, some laser systems are purposely designed with an additional focusing lens allowing convergence or di-

vergence of the light beam by moving the handpiece closer to or further from the tissue. Finally, laser light beam is extremely bright containing a large amount of energy in a small area, thus creat- ing a dramatic tissue effect.

In addition to the wavelengths, lasers vary in their pulse durations. Continuous-wave lasers, such as carbon dioxide, argon, and krypton, emit a continuous beam of light at the same energy. Me- chanical shutters may be used with these lasers to allow laser emission for a set time (usually 0.02- 1.00 seconds or more) and similar amount of off or close time. The power is in the 1- to 100-W range. The quasicontinuous-wave lasers, such as the superpulsed carbon dioxide, copper vapor, copper bromide, and potassium-titanyl-phosphate (KTP) lasers, emit a rapid train of short pulses. These lasers affect the skin in the same manner as the continuous-wave lasers. Pulsed lasers, such as the flashlamp-pumped pulsed dye laser, emit pulses with peak energy in the kilowatt range and with pulse duration in the 0.5-1.5 ms range. The pause between pulses is long enough for the handpiece to be moved to a new untreated area so that multiple pulsing to the same site does not occur. Q-switched lasers, such as the Q-switched alexandrite, Q-switched Nd:YAG and Q-switched ruby, emit even shorter pulses, in the 5- to 100-ns range. This is achieved with an elec- tro-optic switch turning polarizers 90 degrees to each other blocking light emission from the optic cavity, then turning them parallel to each other allowing the emission of all the stored light. Thus, the emitted beam has very high peak power, in the megawatt to gigawatt range. The combination of high peak power and short pulse duration allows these lasers to effectively target very small particles like tattoo ink and melanosomes.

Laser light incident onto the skin has 4 possible consequences: absorption, reflection, scattering, and transmission. Absorption and scattering ac- counts for most of the incident light, whereas only 4% to 7% of the light is reflected by the stratum corneum. According to the Grotthus-Draper law of photobiology, absorption of light by tissue is necessary for an effect. Chromophores in the tissue are particles or molecules that selectively absorb certain wavelengths of light. Thus a given chromophore has a characteristic absorption spectrum. Chromophores present in the skin in-

DERMATOLOGIC LASER SURGERY

Table 1. Specifications for 532-nm ms-pulsed Green Lasers

109

Laser Loser Type Maximum Fluence J/cm 2 Spot sizes (mm) Repetition Rate Other Features

Versapulse (Coherent) True pulsed in 1-10 msec domain. 0.26-0.38; upper fluence is 2 10 1-6 Hz Chilled tip Domains above 15 to 50 msec capped by software for consist of 3-msec subpulses safety

Aura KTP (Laserscope) Q-switched domain, pulsed, 1-999; maximum fluence 1, 2, and 4 1-10 Hz Smartscan grouped into millisecond pulses at 4 mm = 14 J/cm 2

CB Diode (Continuum Q-switched domain, pulsed, 0.3-240 0.4, 0.8, and 1.2 1, 5, and 10 Scanner available Biomedical) grouped into millisecond pulses Hz (optional)

Diolite (Iriderm) Q-switched domain, pulsed, 0.1-950 0.2, 0.5, 0.7, 1, Single 0.5, 1, Scanner available grouped into millisecond pulses and 1.4 2, 3, and up (optional)

to 15Hz

NOTE. Reproduced with permission from McGraw-Hill Companies. Copyright @ 2000. Dover J, Arndt K, Geronemus R, et al. Illustrated cutaneous laser surgery. 2nd ed. Norwalk (CT): Appleton & Lange; 2000.

clude water, melanin, nucleic acid, protein, oxyhemoglobin, and deoxyhemoglobin.

Several measurements of the laser light are commonly encountered in clinical practice. En- ergy (joules) is the amount of work. Power (watts = joules/seconds) is the rate at which the work is done. Fluence (joules/cm 2) is the amount of work applied to a unit area. Fluence is also called energy density. Irradiance (watts/cm 2) is the rate of energy applied to a unit area. Irradiance is also known as power density.

In 1983, Anderson and Parrish presented the theory of selective photothermolysis, which marked a new era in laser applications. The theory predicts selective tissue injury if the following 3 conditions are fulfilled. (1) The wavelength of light is preferentially absorbed by the chromophore in the target tissue and not the surrounding structures. (2) The pulse duration is less than or equal to the thermal relaxation time (Tr) of the target structure. (3) The fluence is greater than or equal to the threshold fluence for tissue destruction. The thermal relaxation time is defined as the time required for an object to cool to 50% of the initial temperature reached. Larger structures usually take longer to cool than smaller ones. The concepts of selective photothermolysis have been applied in the making of numerous new lasers with specific tissue effects in mind.

V A S C U L A R LESIONS

Lasers

Treatment of vascular lesions is one of the first applications of medical laser technology that provides the physician with many unique therapeutic options. Before pulsed lasers, continuous and

quasi-continuous wave lasers, such as the argon, argon pumped tunable dye, copper vapor, and krypton, were used. Because of the nonselective nature of the tissue injury by these lasers, it soon became clear that they were associated with relatively high incidences of side effects, in particular, scarring and permanent hypopigmentation. Thus, after initial enthusiasm in treating a variety of vascular lesions, their use in the more innocent lesions such as hemangiomas declined rapidly.

The flashlamp pumped pulsed dye laser for vascular lesions was the first laser designed in accordance with the principles of selective photothermolysis for the purpose of treating vascular lesions. Its initial wavelength of 577 nm was cho- sen to match an oxyhemoglobin absorption peak, then it was increased to 585 nm for deeper skin penetration. Its 0.45-ms pulse duration is shorter than the thermal relaxation time of the cutaneous vessels. After laser treatment, selective damage of blood vessels with coagulated red blood cells, platelets, and fibrin were noted histologically in the papillary and upper reticular dermis, whereas surrounding structures remain uninjured. Be- cause of the specific nature of vessel destruction, lesions that were not eagerly tackled by laser sur- geons before because of unjustifiably high risk-to- benefit ratios are now amendable to safe and effective treatments. More recently, a wavelength of 595 nm along with a 1.5-ms pulse duration is available for even better tissue penetration and uniform heating of the larger, deeper vessels. The VLS (3, 5, 7, 10 mm, 20 J/cm 2) (Cynosure, Chelmsford, Mass) and Candela ScleroPLUS (Candela Corp, Wayland, Mass) 5, 7, 2 • 7 mm, 30 J/cm 2, Wayland, Mass) both have selectable


Table 2. Pulsed 1064 nm Nd:YAG Lasers

Maximum Fluenee Laser Laser Type J/cm 2 Pulse Width Spat Sizes (ram)

Orion (Laserscope) KTP at 532 nm: quasi-CW with 1-300 J/cm 2 1 1o 500 msec 1, 2, and 4 mm

StarPulse Nd:YAG at 1064 nm:

CW with StarPulse Intense pulsed light at 515-1200

nm Nd:YAG at 1064 nm

Nd:YAG at 532 nm, 1064 nm: quasi-CW, Captured Pulse

VascuLight (ESC) 3-90 J/cm 2 0.5 to 25 msec 8 • 35 ram, 8 • 15 mm

40-150 J/cm 2 1 to 14 msec 6 mm

VeinLase (HGM) 100 J/cm 2 0.5 1o 50 msec captured pulse 0.6, 2, and 4 mm

NOTE. Reproduced with permission from McGraw-Hill Companies. Copyright @ 2000. Dover J, Arndt K, Geronemus R, et al. Illustrated cutaneous laser surgery. 2nd ed. Norwalk (CT): Appleton & Lange; 2000.

wavelengths, 585,590, 595,600 nm, and 1.5 ms- pulse duration. In conjunction with cryogen (tetrafluoroethane) spray from Dynamic Cooling De- vice (DCD) (Candela Carp), higher fluences may be safely applied with these new modifications for more efficacious treatments. The benefits of these alterations to the laser are already seen in the treatment of a variety of vascular lesions, including capillary vascular malformations, hemangiomas, leg telangiectases, and hypertrophic scars. The availability of this modified laser is expected to increase significantly.

Recently, a number of other lasers have been developed to target cutaneous vessels. The Nd: YAG lasers emit at 1064 nm, which should reach 5 to 8 mm into the skin and thus have been used primarily for larger and deeper leg telangiectases, including reticular veins (Table 1). Some have even used these lasers for large deep veins of the lower eyelids with variable success usually without purpura. The continuous wave Nd:YAG is rarely used today because of its high risk of scarring.

Pulsed alexandrite lasers emit at 755 nm, a wavelength well absorbed by hemoglobin and a wavelength long enough to reach substantial depth into the skin. Thus, there have been studies for low extremity telangiectases, which tend to be larger and deeper compared with other body sites. GentleLASE (755 nm, 8-60J/cm 2, 8-15 mm, 3 ms) (Dynamic Cooling Device, Candela) has been shown to be effective in treatment of leg telangiectases. Cynosure TKS (755 nm, 50 J/cm 2, 5, 10, 20 ms, 7, 10 mm) (Cynosure, Inc) is another pulsed alexandrite laser in this class.

Frequency-doubled Q-switched Nd:YAG lasers emit green light at 532 •m by passing a Nd:YAG (1064 nm) laser beam through an optical KTP (potassium-titanyl-phosphate) crystal, which

doubles the frequency and halves the wavelength. The resultant wavelength is 532 nm and is near an oxyhemoglobin absorption peak. A number of such long-pulsed 532-nm lasers are available (Ta- ble 2). VersaPulse (Coherent Laser Carp, Palo Alto, Calif) is a dye-pumped KTP laser that has a water-chilled quartz tip. With the high energy long pulsed green (HELP G) function, the laser is capable of pulse durations of 2 to 50 ins. The Aura (Laserscope-Orion, San Jose, Calif), CB Diode/ 532 (Continuum Biomedical, Dublin, Calif), and Diolite 532 (Iriderm, Mountain View, Calif) are different from the VersaPulse in that they emit a pulsed train of grouped Q-switched pulses, yield- ing a net effect likened to 1 to 100 ms pulse durations. These 3 lasers also have optional scanners. The long pulse widths of these lasers allow slower heating of the vessels without resultant vascular rupture and purpura, unlike the pulsed dye laser treatments. There is notable epidermal melanin absorption at this wavelength, epidermaI injury and the risk of pigmentary alternations is expected to be higher than longer wavelength lasers, especially in skin types III and higher. Also, because skin penetration by light of 532 nm wavelength is limited, only superficial lesions are targeted. Currently, facial telangiectases and some fine superficial leg telangiectases are effectively treated.

In addition, intense pulsed light source (Photo- Derm, ESC Medical Systems, Ltd, Haifa, Israel) uses a flashlamp to produce a spectrum of light from 515 nm to 1200 nm and fluences up to 90 J/cm 2. Cutoff filters are place to block light below 515 nm to below 695 nm. The noncoherent light may be delivered in single, double, or triple pulses of 2 to 10 ms each with variable delay between pulses. The 8 • 35 mm spot handpiece allows treatment of large areas with relative ease. An-

DERMATOLOGIC LASER SURGERY 111

other advantage of these systems is the lack of purpura when treating vascular lesions. Although the variability in the treatment parameters of this system theoretically allows them to be adjusted ideally for the characteristics of the target lesion, vast experience is necessary to make such adjust- ments in order to maximize efficacy and minimize side effects. This pulsed light source has been shown to treat portwine stains, hemangiomas, and facial and lower extremity telangiectases. How- ever, the comparison to the pulsed dye laser, more treatments may be necessary for the same degree of lesional clearance.

A number of diode lasers, emitting at 800 nm, 900 nm, or 930 nm, are being studied. The longer wavelengths of light allow deeper skin penetration. They are poorly absorbed by hemoglobin and are minimally absorbed by epidermal melanin. This situation actually enables delivery of higher fluences to compensate for the poor absorption by hemoglobin with potentially less epidermal side effect. The LightSheer 800 nm diode laser (Coherent Star, Pleasanton, Calif) has a variable pulse duration of 5 to 30 ms suitable for those large-caliber vessels situated deeper in the skin.

Cl in ica l A p p l i c a t i o n s

Portwine stains are capillary vascular malformations that appear as dilated vessels in the papillary dermis. They are present in 0.3% to 0.5% of neonates as pink patches and gradually darken in color. By the fifth decade of life, approximately two-thirds of the affected individuals will have hypertrophy of the lesion and vascular nodules that might bleed. Much has been studied and written on the medical necessity and psychological benefit of treating these lesions. However, before the new laser era, management of capillary vascular malformations included excision, dermabrasion, radiation therapy, and cryotherapy, which often left scarring. Continuous and quasi-continuous wave lasers were then used frequently, resulting in scarring and pigmentary changes. Compared with today's laser technology, the risk- benefit ratios of those methods are unacceptable. The laser of choice today for capillary vascular malformations is the pulsed dye laser and its newer modified versions. The cryogen spray used in conjunction with the 595 nm, 1.5 ms laser decreased the healing period and side effects when patients with portwine stains were treated at 10

Fig 1. Capillary vascular malformation in a 1-month-old boy treated with a modified pulsed dye laster (ScleroPlus laser, Candela, Wayland, Mass) at 595 nm, 11 Jlcm% 7 mm spot, with 30 msec of Dynamic Cooling Device cryogen spray and 30 msec delay. (A) Before. (B) Three weeks after 6 treatments at 3-week intervals.

J/cm 2. Overall, this laser appears to be able to effect better clearance and fewer side effects after comparable number treatments with the original pulsed dye laser. Though multiple treatments are necessary to achieve complete clearance or reach an endpoint of improvement, some trends lie in the characteristics of the lesions. For example, head and neck lesions respond more readily than


Fig 2. Nasal te langiectas ia on a white man treated with pulsed dye laser at 6 .25 J / c m =, 7 mm spot. (A) Before. (B) Two months after 2 treatments.

truncal ones, followed by distal extremity lesions. On the face, centrofacial portions of portwine stains in the trigeminal nerve (V2) distribution are more resistant to treatment than those laterally. Finally, lighter lesions in individuals less than 10 years of age with skin types I-III also tend to require fewer treatments. In fact, there are data in support of treatment during infancy because of the better response and the extremely low risk of side effects with today's technology. Other lasers including VersaPulse (Coherent Laser Corp) and VascuLight (ESC Medical Tech) are being studied for capillary vascular malformations. Despite all that has been written on the medical, social, and psychological detriment on leaving these lesions untreated and despite the relative ease of effective treatment, a surprisingly large portion of today's managed care organizations deny, unethically in our opinion, insurance coverage for treatment.

Hemangiomas are a common vascular lesion in infancy present in 10% of newborns with frequency 3 times higher in girls than in boys. After a rapid proliferation period during the first year of life, hemangiomas undergo involution over the next 5 to 10 years. Because an estimated 60% of the lesions occur on the head and neck regions,

there is obvious social and psychological advantage in early resolution of these lesions, especially before formal schooling. Although laser therapy is most effective in thin superficial lesions, early treatment of thicker lesions can limit the size of the hemangioma to some extent as well as control ulceration and bleeding. Although monthly to bi- monthly treatment intervals are recommended for regressing hemangiomas, actively proliferating lesions should be treated every 2 to 3 weeks. The same lasers, the pulsed dye laser and its newer versions, are effective in treating hemangiomas with extremely low risk-to-benefit ratio.

Before the advent of the vascular-specific pulsed dye laser, treatment of facial telangiectases with continuous wave and quasi-continuous wave lasers, even with robotized scanners, had unac- ceptably high risks and thus was rarely used for this purpose. The pulsed dye laser effectively pho- tocoagulated facial telangiectases with the primary side effect of resultant purpura lasting 7 to 10 days after treatment. In one study, good to excellent responses were noted in 97.5% of patients after 1 to 3 treatments with the 585 nm, 450 ms pulsed dye laser at 6-7.75 J/cm 2 and 5 mm spot. Smaller red vessels seemed to have re-


Fig 3. Nevus of Ota on a 6-year-old Asian girl t reated with the Q-switched ruby laser at 4-5 J / c m 2, 6.5 mm spot. (A) Before. (B) Six months after 5 treatments at 8-week intervals.

sponded better than the larger blue ones. The 595 nm, 1.5 ms laser with DCD appears to be more effective on those larger deeper facial vessels. A 2 • 7 m m elliptical spot more closely approxi- mates the configuration of the vessels, and DCD providing cryogen spray offers epidermal protection and decreased patient discomfort. Another group of systems all with millisecond pulse duration can treat facial telangiectases with minimal side effects and without residual purpura: KTP (532 nm) green light lasers, Nd:YAG (1064 nm) laser, and intense pulsed light source as described above. As may be expected from the wavelength, the superficial fine vessels respond well to the 532 nm lasers, whereas the deeper, large-calibered, blue infraorbital vessels are better targeted by the 1064 nm laser.

Regarding the treatment of leg veins, although sclerotherapy has long been the gold standard, its disadvantages include high-technique dependence, matting, ulceration, and possible patient allergy to sclerosant. An increasing number of lasers are being explored and used for the treatment of leg veins. Treatment of leg veins presents a challenge because there is an even wider range of

size and depth of the vessels than on the face. In addition, elevated hydrostatic pressures of the lower extremity and thicker vessel wall often ad- versely affect treatment results. Because of these characteristics, longer wavelength, longer pulse duration, and higher fluence, as well as means of epidermal cooling, are important. Thus, the modifications of longer wavelength (585-600 nm), longer pulse width (i.5 ms), and DCD cryogen spray have advantages over the 585 nm, 450 ms pulsed dye laser. Studies have shown clearance rates as high as 75% at sites treated thrice at 15 to 20 J/cm 2 with a 2 • 7 mm elliptical beam. Post- treatment purpura resolved in 7 to I0 days, and the 20% to 30% incidence of hyperpigmentation all resolved within 3 months. Clearances of 100% after 1 to 2 treatments of vessels <0.5 mm and 80% after up to 4 treatments of vessels 0.5 to 1.0 m m were seen in another study. The 532 nm KTP green light lasers target small superficial vessels. In general, greater than 50% clearance has been reported in 80% to 90% of the sites treated 2 to 4 times at 9.5-16 J/cm 2 and 10 to 20 ms. Transient pigmentary alterations are seen in up to 36% of the sites. Long pulsed alexandrite lasers are being ex-


Table 3. Q-switched Pigment Lasers

Wavelength Pulse Pulse rate Maximum Fluenees Laser Type Manufacturer (rim) Duration (Hz) Spot Sizes (mm) (J/cm 2)

Spectrum RD-1200 QS ruby Spectrum (Palomar) 694.3 28 nsec 0.8 5, 6.5 3-10

Alexlazr QS alexandrite Oandela 758 50 nsec 5 2, 3, 4 3-12 PhotoGeniea-T QS arexandrile Cynosure 752 1 O0 nsec Single-10 2.4 10

Vesapulse VPC FD Nd:YAG Coherent 532 2-50 msec Single-6 2-10 0.26-38 QS FD Nd:YAG 532 4 nsec Single-lO 2-6 0.36-6

QS Nd:YAG 1064 5 nsec Single-lO 2-6 0.75-12

QS alexandrite 755 45 nsec Singled 0 2-6 0.85-12

Medlite IV QS FD, QS Nd:YAG Continuum Biomedical 532, 1064 5-7 nsec 1, 2, 5, 10 532 nm: 2, 3, 4, 6 532 nm: 5 at 3 mm 1064 nm: 3, 4, 6, 8 1064 rim: 6 at 4 mm

NOTE. FD, Frequency-doubled; QS, Q-switched. Reproduced with permission from McGraw-Hill Companies. Copyright @ 2000. Dover J, Arndt K, Geronemus R, el al. Illustrated Cutaneous Laser Surgery.

2rid ed. Norwalk (CT): Appleton & Lange; 2000.

plored for deep large-caliber leg veins. In one study, 20 adult subjects with 54 patches of leg veins up to 2 m m in diameter were treated once at 60 or 80 J/cm 2 with 70-100 ms DCD cryogen (tetrafluoroethane) spray and 3 ms delay (Gentle- LASE). At 3-month follow-up evaluation, 65% of the sites had greater than 75% clearance and 87% had greater than 50%. Thirty-six percent of the sites had mild or moderate hyperpigmentation at 3 months. Diode lasers emitting at 800 to 810 nm offer good skin penetration and are close to the hemoglobin absorption peak of 915 nm. When an 800 nm pulsed diode laser (LightSheer) was used for leg veins up to 1 mm, 25% cleared after 1 treatment, 50% after 2 treatments, and 75% after 3 treatments. Better clearance was noted with larger vessels. The long pulsed Nd:YAG laser emitting at 1064 nm offers even deeper penetration. With fluences 80-130J/cm 2 at single, double, and triple i0 to 16 ms synchronized pulses, 75% improvement was reported 3 months after a single treatment of vessels 0.5-3 mm. Lastly, PhotoDerm, an intensed pulsed light source, offers another treatment option for leg veins. Wavelength spectrum and pulsed duration may be selected to match the characteristics of the target vessel. In a multi- center trial, 369 sites with up to 3 mm diametered vessels in 159 subjects were treated up to 5 times. Greater than 75% clearance was seen in 79% of the sites, and greater than 50% clearance in 90% of the sites. Unlike treatments with the pulsed dye laser where purpura is a predictable consequence, rupture of vessel and purpura is only occasional with these latter systems.

Other common vascular lesions amendable to laser treatment include spider angiomas, rosacea-

associated telangiectases and erythema, and venous lakes. For poikiloderma of Civatte in particular, multiple treatments with the pulsed dye laser at low fluences and large spot size have proved to be optimal. Even hypertrophic scars and psoriatic plaques appear to improve with pulsed dye laser treatments.

The new trends in the treatment of vascular lesions include longer pulse durations, coupled cooling devices, and in some cases, longer wavelengths. The longer pulse widths in the millisecond domain allow more uniform heating of the blood vessels, and thus are less likely to result in vascular rupture and in purpura. Because epidermal protection has been associated with decreased side effects, a variety of cooling devices are now recommended with the use of the various lasers by either precooling the skin before laser irradiation or simultaneous cooling during the laser procedure itself. The Dynamic Cooling Device uses a cryogen (tetrafluoroethane) spray immediately before each laser pulse, as with the GentleLASE long pulsed alexandrite laser and ScleroPLUS laser. The laser beam from the VersaPulse (Coher- ent Laser Corp) traverses through a water-cooled quartz plate on the handpiece that comes in contact with the epidermis. Cooling gel provides epidermal protection and decrease light reflectance from the stratum corneum in the systems such as the Vasculight and Aura. For those deeper, bigger vessels, lasers with longer wavelengths are also being developed for better skin penetration. This category includes the long pulsed alexandrite lasers, long pulsed Nd:YAG, and modified pulsed dye laser with selectable wavelengths of 585 nm, 590 nm, 595 nm, and 560 nm.


Fig 4. Green and black professional tattoo on a white man treated with Q-switched ruby laser at 8.5 J /cm 2, 5 mm spot. (A) Before. (B) After 3 treatments. (C) After 8 treatments.

REMOVAL OF BENIGN PIGMENTED LESIONS AND TATTOOS

Treatment of benign pigmented lesions and tattoos depends on melanin and exogenously origi- nated tattoo inks, respectively, as the target chromophores. The target structures are melanosome and tattoo pigment containing membrane-bound intracellular granules. Benign pigmented lesions may be a result of increased melanocytes or increased melanogenesis in the epidermis, dermis, or both. Examples of increased melanogenesis include ephelides, Becket's nevi, and melasma. Nevi of junctional, intradermal, or compound type, either congenital or acquired, are lesions with increased melanocytes. Tattoos, on the other hand, result from exogenously induced ink, organometallic dyes, dirt, or asphalt that are bound in intracellular granules of dermal macrophages or fibroblasts.

Benign P i g m e n t e d Lesions

Traditionally, epidermal pigmented lesions, such as cafe-au-lait macules, ephelides, and len-

tigines, have been tackled by cryotherapy and acid peels such as with trichloracetic acid, alpha-hydroxy acids, and beta-hydroxy acids with variable success (Table 3). Dermabrasion has been commonly used for epidermal pigment, and surgical excision commonly for dermal pigment. Resurfac- ing lasers, such as carbon dioxide and erbium: YAG lasers, which are nonselective for melanin have also been used. Dermal pigmented lesions such as nevus of Ota are less responsive to the above treatments and frequently resort to camouflaging cosmetic tattooing. Lasers that are selective for melanin are the most popular for pigmented lesions of epidermal, dermal, or combined nature.

In 1963, Goldman et al were the first to exper- iment with 694 nm ruby lasers, both 500/xs normal mode and Q-switched, demonstrated more intense effect on darker-colored skin. Those studies showed melanin as the target chromophore and melanosomes as the target structure. How- ever, it was not until the 1980s that electron mi- croscopy studies confirmed that melanosomes are


actually disrupted after Q-switched laser irradiation. These further investigations showed 40 to 750 ns as the necessary pulsed duration for melanosome disruption.

The Q-switched ruby laser has as the active medium the ruby crystal made from aluminum oxide and chromium. At the wavelength of 694 nm and pulse duration of 20 to 40 ns, it is capable of high peak powers (10J/cm2). A beam of 694 nm is well absorbed by melanin and by blue-black tattoo ink, and it penetrates approximately 1 mm into the skin permitting effect on both epidermal and dermal pigments. Lentigines, including labial lentigos, usually clear completely after a single treatment. Caf~ au lait macules, Becker's nevi, and nevus spilus usually lighten after a series of treatment, but frequently recur in the ensuing months to years. Dermal pigmented lesions such as nevus of Ito and Ota respond well to Q-switched ruby laser treatment, but numerous treatments are necessary. Interestingly, minocycline-induced cutaneous hyperpigmentation, as a result of granules with staining properties similar to melanin and/or hemosiderin, has been successfully treated with Q-switched ruby laser.

The Q-switched alexandrite laser emits 100 ns pulses of 755 nm light, which is close to that of the ruby laser. It has been shown to effectively lighten epidermal and dermal lesions.

The Q-switched Nd:YAG laser emits 10 to 20 ns pulsed either at 1064 nm or at 532 nm when the frequency-doubling KTP crystals are applied. De- spite the relatively poor absorption of 1064 nm light by melanin, its ability to penetrate deeply into the skin offers enough of an advantage for it to be useful. Dermal pigmented lesions, such as nevus of Ito and Ota respond well to this treatment. The competitive absorption of the 532 nm light by both melanin and hemoglobin places lim- itations on its use in pigmented lesions and tends to increase its potential risk of side effects. In one study using fluences of 2 to 5 J/cm 2, 84% of lentigines showed at least 50% lightening after several treatments. Care au lait macules, Becket's nevi, and nevus spilus tend to recur months after treatment as they do after treatments with other lasers.

The 510 nm flashlamp pumped pulsed-dye laser emitting 300 ns pulses was designed for epidermal pigments for which considerable success has been shown.

Conditions such as postinflammatory hyperpigmentation and melasma should be approached with extreme caution as they may worsen. Melasma especially have a high recurrence rate. Minimal intervals between multiple treatments of pigmented lesions are usually 6 to 8 weeks.

Congenital nevi may be lightened with red or infrared light lasers such as the long-pulsed ruby laser used alone or in conjunction with Q-switched lasers. In general, lightening of the lesions is achievable, but recurrences may occur since not all of the melanocytic cells are destroyed. With the long-pulsed red light lasers, fibrosis in the papillary dermis may sometimes obscure the persistent dermal nevus cells providing the clinical picture of clearing.

Tattoo Remova l

Before laser, methods of tattoo removal were limited to dermabrasion, salabrasion, and surgical excision, which usually resulted in scarring. Suc- cessful laser tattoo removal was reported as early as 1964 by Goldman et al. However, the technique did not assume popular application until work done by Scottish scientists in the 1980s showing removal of blue-black tattoos without permanent epidermal damage.

Tattoo removal by lasers is probable via a number of mechanisms (Table 3). The high temperature achieved from the laser pulse causes chemical alteration and fragmentation of the tattoo pigments. The shattered particles then undergo re- packaging by local macrophages, transportation to regional lymph nodes, and elimination trans- epidermally.

Response of tattoos to laser treatments in general depends on the particular type and color of the ink and how and when it was placed into the skin. Amateur tattoos, usually containing smaller carbon-based particles, require fewer laser treatments for clearance than multicolored professional ones with densely arranged organometallic dyes. Studies with a 25 ns Q-switched ruby laser showed that 85% of amateur tattoos were completely removed in an average of 3 treatments and that 10%, 70%, and 20% of professional tattoos were completely, partially, and minimally cleared, respectively, after an average of 6 treatments.

The Q-switched lasers, ruby (694 nm), alexandrite (755 nm), and Nd:YAG (1064 nm), are nearly comparable in their abilities to remove

DERMATOLOGIC LASER SURGERY

Table 4. Lasers and Lightsource for Hair Removal

117

Maximum Device Name/manufacturer Wavelength Pulse Width Spol Size Fluence Pulse Rate Olher

Long pulsed Photogeniea LPIR 775 (nm) 5, 10, 20 ms 7 (ram) 40 J/crn 2 1 Hz or single Cooling tip alexanddte (Cynosure) 10 (ram) 25 J/cm 2 (Optional)

6 x lO(mm) 30J/cm 2

GentleLASE (Condela) 755 (nm) 3 ms 8 (mm) 100 J/cm 2 1 Hz Cryogen spray 3 X 10 (ram) 100 J/cm 2 cooling

12(ram) 40J/cm 2 15(mm) 30J/cm 2

18 (ram) 20 J/crn 2

EpiTouch (Sharplan) 755 (nm) 2 ms 5 (ram) 50 J/cm 2 5 Hz or single 7 (ram) 25 J/cm 2

Diode FeatherLite (LaserLite) 805 + 25 (nm) 100 ms 2 (ram) 60 W 5 Hz Chill tip 2 x 4 (mm)

LightSheer (Coherent) 600 (nm) 5-30 ms 9 x 9 (mm) 40 J/cm 2 0.5 Hz

Normal mode, EpiLaser (Palomar) 694 (rim) 3 ms 7, 10 (ram) 40 J/cm 2 0.5 Hz EpiWand cooling long pulsed ruby handpiece

QS Nd:YAG with SoflLight (Thermolase) 1064 (nm) 17 ns 7 (mm) 2.5 J/cm 2 1, 2, 5, 10 Hz

carbon-based (2-3 J/cm 2)

suspension Intense pulsed light EpiLight (Energy Systems 590-1200 (rim)

source Carp) 2.7-7 ms 8 • 35 (ram) 30-65 J/cm 2 2-5 pulse sequelae

10 x 45 (ram)

blue-black tattoos. The Q-switched ruby laser is more effective in removing blue-black pigments than brightly colored pigments. Green tattoos respond variably to the ruby laser but are better targeted with the Q-switched alexandrite systems. The absorption of the ruby red light is poor by red pigments and nearly nil by yellow pigments.

Compared with the Q-switched ruby laser, Q- switched alexandrite laser at 755 nm penetrates deeper into the skin and is not as well absorbed by melanin. It is effective in removing blue-black as well as green tattoo pigments, but is less able to target the red pigments. The Q-switched Nd:YAG at 1064 nm does not work well in brightly colored tattoos. However, its frequency-doubled light at 532 nm is optimal for red tattoos. Because the 532 nm light is well absorbed by melanin and hemoglobin, it tends to result in more whitening and purpura than does the 1064 nm beam in the Nd: YAG system. The 1064 nm Nd:YAG is more frequently associated with textural changes and transient hyperpigmentation and less frequently associated with hypopigmentation in comparison with the Q-switched ruby laser. Because of the limited depth of penetration, the 300 ns, 510 nm flashlamp pumped pulsed-dye laser is not efficient in tattoo removal except for those with bright colored pigments, such as orange and purple.

Depending on the size and location of the tattoo, topical or intralesional anesthesia is often

used. Immediately after laser treatment for tattoo removal, epidermal whitening may be expected frequently with crust formation. Wound care with hydrogen peroxide and antibiotic ointment is ad- vised until complete healing of the treated area. In general, side effects of laser tattoo removal are limited to transient pigmentary changes in 10% to 50% of the patients. Textual alterations and persistent hypopigmentation/depigmentation occur in much fewer cases.

Removal of camouflaging and cosmetic tattoos warrants extra caution. With Q-switched laser irradiation, the ferric oxide often present in red cosmetic tattoos undergoes reduction to ferrous oxide, which appears black. Titanium oxide, common in skin-colored or tan-colored tattoos, also undergoes a similar color transformation to blue or black with Q-switched laser treatment. One may resort to resurfacing lasers, such as the Er: YAG in order to remove such tattoo pigments.

As our experience in the field of laser skin surgery increases, there are some systemic medica- tions that are absolutely contraindicated with specific laser systems. For example, those patients who have ever taken systemic gold therapy should n o t be treated with Q-switched laser systems. The resultant gray-blue discoloration of the skin is dif- ficult to manage. However, some success of removing such discoloration has been achieved with the use of a second Q-switched laser system. A1-


Fig 5. Unwanted hair in abdominal area treated with a long-pulsed ruby laser (EpiLaser, Palomar, Lexington, Mass) at 694 nm, 3 msec, 7 mm, 35 J l c m =. (A) Before. (B) Three months after 3 treatments at 6-week intervals. Courtesy of Arielle N. B. Kauvar, MD.

though the half-life of isotretinoin and its metab- olites is relatively short, its cutaneous effect, in particular its hinderance to normal wound healing, may last months. Thus it is recommended that laser treatments, especially those that disrupt the epidermal integrity, be postponed for at least 1 year after the last isotretinoin dose.

Tattoo removal continues to be an area yearn- ing for advancement. Tackling some of the more resistant colors, such as yellow, in tattoos and clearing the residual faint pigmentation have always been challenging. Decreasing the number of treatments necessary is also highly desired. These difficulties have in part been overcome by recent work done with carbon-based lotion used in conjunction with Q-switched Nd:YAG at 1064 nm. Normally, the epidermal whitening and crust formation prevent tissue effect from a second laser pass immediately after the first. However, if after the traditional first pass of a Q-switched laser, a carbon-based lotion is applied on the treated skin surface followed by Q-switched Nd:YAG (1064 nm) irradiation, an additive photoacoustic effect is believed to take place. Clinically, this protocol

appears to achieve faster clearing than without a traditional second pass or without the carbon- based lotion. Better clearing is also seen with those more resistant bright-colored pigments.

HAIR REMOVAL

Hair reduction is one of the newest areas of laser application. Although it is a valuable tool in the management of various medically related conditions of excess hair or hirsutism, the current interest in laser hair reduction is also fueled by pub- lic interest. Because of our culture and life style, excess hair, except on the scalp, often seems to be an undesirable trait, as evidenced by the numerous methods of hair removal including shaving, waxing, tweezing, and electrolysis. Finally, laser holds the promise of long-term hair reduction with minimal side effects.

Laser hair removal is based on the theory of selective photothermolysis, with follicular melanin as the natural target chromophore. Within the hair follicles, melanin is present in the hair shaft, bulb, and follicular epithelium. For individuals with light hairs containing little melanin, exog-


Fig 6. Facial rhytides in a 70-year-old woman treated with a carbon dioxide laser (Ultrapulse, Coherent, Santa Clara, Cali f ) at 300 m J, 60 watts, and density of 6. (A) Before. (B) Six months after treatment.

enously applied carbon is used as the chromophore with a certain laser system. Red and infrared lights (600-1100 nm) are the best wavelengths to provide the desired combination of selective absorption by melanin and deep penetration into the dermis. Another parameter of critical concern in selective follicular injury is the pulse duration. For hair follicles with average diameters of 200 to 300/xm, the thermal relaxation time is estimated to be 40 to 100 ms. Thus, to minimize epidermal injury, the optimal pulse duration of a hair removal laser should be less than 40 to 100 ms and greater than the thermal relaxation time of the epidermis, which is about 3 ms.

Several systems are available today for hair removal (Table 4). The long-pulsed ruby, long- pulsed alexandrite, and the diode lasers all use melanin within the hair follicle as the chromophore for selective thermal injury. Different Q-switched Nd:YAG lasers have been used for hair reduction with or without an application of exogenous carbon. Non-laser intense pulsed light sources can also target melanin and are used for the same purpose. Many of these systems incorpo- rate a cooling handpiece, cooling gel, or cryogen spray in an attempt to protect the epidermis from

thermal injury, thus allowing higher fluences to be applied safely.

The long-pulse ruby lasers emit at a wavelength of 694 nm and include EpiLaser (Palomar, Lex- ington, Mass) and EpiTouch Ruby (ESC/Sharplan Medical Systems, Needham, Mass). After a single treatment of 13 fair-skinned, dark-haired subjects in one study using a long-pulsed ruby laser (694 nm, 3 ms, 7, 10 mm, 10-40 J/cm 2, EpiLaser), all had hair-growth delays lasting 3 to 6 months compared with wax epilated or shaved control sites. The amount of hair reduction appeared to be energy-dependent. In only 4 of these 13 subjects, less than 50% regrowth of terminal hairs were observed at 2-year follow-up. Hair counts in these 4 are similar at 6-month, 1-year, and 2-year follow-ups, implying the persistence of these changes in some individuals. Histologic examina- tion revealed a decrease in large terminal hairs and a reciprocal increase in miniaturized, vellus-like hair follicles in these subjects. One study that used a different ruby laser (694 nm, 800/xs, 4-5 mm, 10-40 J/cm 2, EpiTouch) reported 40% to 80% regrowth of arm hair 12 weeks after a single treatment. Further studies have shown improved efficacy with larger spot size, 10 mm, compared with


7 mm. In addition, cooling of the epidermis de- creases incidence of side effects.

The long-pulse alexandrite lasers emitting at 755 nm have similar mechanisms of action as the long-pulsed ruby laser. EpiTouch Alex (ESC/ Sharplan Medical Systems), GentleLASE (Candela Laser Corp), and Photogenica LPIR (Cynosure, Inc) are currently available. In 1 study of 126 patients treated up to 5 times with a long-pulsed alexandrite laser (755 nm, 2 ms, 5-7 mm, up to 50 J/cm 2, EpiTouch), 90% hair reduction was found at 3 months after the last treatment. A comparison study of the long-pulse alexandrite and long-pulse ruby laser showed similar efficacy and side effect profiles. Similar to the ruby laser, larger spot size, 10 mm, appears to be more effective than 7 mm spot size, and higher fluences resulted in greater hair reduction. An analysis of 392 patients treated with a long-pulsed alexandrite laser (755 nm, 5, 10, 20 ms, 7, 10, 6 • 10 mm, up to 40 J/cm 2, Photogenica LPIR) showed a higher incidence of erosions in the 62 patients with darker or black skin. A study of 14 subjects of skin type IV and V was conducted by using a long-pulsed alexandrite laser (GentleLASE) at 8-20 J/cm 2, 3 ms, 15 mm, 100 ms DCD with 3 ms delay. After a short period of hair growth delay after a single treatment session, regrowths at the treatment sites were comparable with the control sites by 3-month follow-up evaluation.

Diode lasers emitting at 800 nm include Feath- erLite (LaserLite, Boston, Mass) and LightSheer (Coherent-Star, Pleasanton, Calif). When 58 subjects of skin types II and lli were treated with a diode laser (800 nm, 5-30 ms, 9 • 9 mm, up to 40 J/cm 2, LightSheer) once or twice at l -month intervals, approximately 90% of the dark-haired subjects and 30% of the blonde-haired subjects showed hair growth delays. Higher fluences and multiple treatments were associated with greater amount of hair loss. Both the reduction in hair diameters and lightening of hair color reached statistical significance. Long-term hair regrowth data at an average follow-up of 20 months after treatment are available from a prospective follow-up of 20 out of 50 original subjects treated with a diode laser (LightSheer). Regrowth was 22% to 31% at 1 month after a single treatment and stabilized between 65% to 75% at 3 months to 20 months. Longer growth delays were seen after 2 treatments at a 1-month interval, with regrowth

plateau starting at 6 months and ranging 47% to 66%. Transient pigmentary changes were limited in those with skin types II and III.

Q-switched Nd:YAG lasers emitting at 1064 nm have been used with (SoftLight, Thermolase Corp, Carrollton, Tex) and without (MedLite IV, Con- tinuum Biomedical) exogenous carbon. In the SoftLight system, carbon is physically introduced into the hair follicles by rubbing a carbon-based lotion onto the skin and wiping it off the skin surface immediately before laser irradiation. The microparticulate carbon is propelled down the hair shaft and generates photoacoustic waves when low-energy laser light is absorbed. This re- suits in a photomechanical disruption of the hair follicle. Because follicular melanin is not the target chromophore, blonde and red-haired patients may be effectively treated by this method. In addition, because the absorption of 1064 nm light by epidermal melanin is minimal, this system may be used more safely in darker skin-typed patients. Growth delays have been reported for up to 3 months after a single treatment. However, although better than wax-epilation, which yield hair regrowth at 1-month follow-up, hair regrowth is seen at 6 month after a single SoftLight treatment. Permanent hair loss has not been ob- tained even with multiple treatments. The Q-switched Nd:YAG laser in the nanosecond pulse range appears to cause reversible photomechanical disruption of the follicle, but not photothermal injup/seen with millisecond-range lasers.

Intense pulsed light source, such as the Epi- Light (ESC Medical Systems) is a non-laser system also used for hair removal. Rather than emitting a specific wavelength of light as by a laser, it emits light with wavelengths ranging from 540 to 1200 nm. The characteristics of the emitted energy can be tailored to patients with different hair and skin color combinations by means of different cut-off filters adjusting the quality of light and variable pulse widths. In one study, 60% hair reduction was reported 12 weeks after a single treatment with various cut-off filters (34-44 J/cm 2, 2-5 pulses, 1.5-3.5 ms, 20-50 ms delays). Adverse effects included posttreatment erythema in 7%, hyperpigmentation in 3%, and blistering in 11%. Other investigators have reported similar data.

Most of the laser and light source systems today use some form of epidermal cooling technique for epidermal protection and patient comfort. The

D E R M A T O L O G I C LASER SURGERY

Table 5. High Peak Power C02 Lasers, Flashsconners, and Er:YAG Lasers

121

Er:YAG Laser Coherent UltroPulse Tissue Technology TruPulse Sharplan SilkLaser (various manufacturers)

Laser lype 100 watt C02 6 W C02 20-150 W C02 Wavelength 10.6 tLm 10.6 t~m 10.6 >m Delivery Method Individual Gaussian Individual square pulses Spiral (SilkTouch, FeatherTouch) or

pulses rasterized (SureTouch) scan with focused beam

Power 500 W peak power, 10,0O0 W peak power, 7-]00 W average power, CW beam pulsed pulsed

Pulse duration 650-950 tLS 60-100 tLS 0.03-0.52 S scan duration; 300- 1000 ,u,s tissue dwell time

Energy N/A CW laser

Er:YAG 2.94 t~m Individual pulses

Effect of increasing Increases rate of pulsing Increases rate of pulsing power

10-20 W average power

250-350/~s

O. 1-3 J/pulse Adjustable 50-500 m J/pulse 10-500 m J/pulse Adjustable by adjustable by changing pulse width changing peak power

Energy fluence 5-7 J/cm 2 5-7 J/cm 2 5-15 Jlam 2 or more 1-60 J/era 2 Spot size 3 mm collimated; 2.25- 1 and 3 mm 6.9 mm 0.6-15-mm scan size with 0.1-0.25- 2-8 mm collimated or focused;

mm spot CPG spatula mm focused beam paltern generator Spot Shape Round spot; various Square spot Round, square, elliptical, or doughnut Round; various with CPG

with CPG scan (SilkTouch, FeatherTouch); various (SureTouch)

Increases thickness of tissue removed with each scan

Increases rate of pulsing (1-20 Hz)

NOTE. CPG, Computer paltern generator. Reproduced with permission from: Dover J, Arndt K, Geronemus R, et al. Illustrated Cutaneous Laser Surgery, 2nd ed. Norwalk (CT): Appleton & Lange; 2000.

various methods of epidermal cooling include application of ice or cooling gel, glass chamber, dynamic cooling device with cryogen spray (tetrafluoroethane [HFC 134-], boiling point = -26.2~ and contact cooling via a chilled sapphire and quartz tip. Because the epidermis contains melanin, the target chromophore, epidermal injury may occur with treatments. Cooling of the epidermis will minimize this risk and also allow the use of fluences higher than would be safe without epidermal cooling. This concept is especially important in the treatment of individuals with darker skin types or with a tan because the competing epidermal melanin is the main reason for the higher incidence of side effects in this population.

Most of the hair reduction treatments have been in individuals of skin types I-Ill. Thus, the side effects are minimal and largely transient. Mild erythema and perifollicular edema are expected and desired immediately after laser treatment for hair removal, although erythema and crusting may be present for a few days. Pigmentary changes may be seen and usually resolve in several months. Blis- tering is uncommon and normally heals without any lasting sequelae. In the hands of the experi- enced physicians or with conservative treatment

parameters, scarring is an extremely rare occurrence.

Treatment of individuals with tanned skin or with skin types IV-VI is complicated by the abun- dance of competing epidermal melanin leading to a much higher risk of pigmentary alterations and epidermal damage. Although the incidences of pigmentary changes may be decreased by the pre- treatment and posttreatment use of bleaching agents and strict sun avoidance, it is still a significant problem. Because of the side effect profile, these individuals are often treated at low fluences, thus resulting in less hair reduction for a shorter period of time compared with the non-tanned, skin types I-III counterparts. Nevertheless, laser treatments at the restricted parameters have been shown to dramatically improve conditions such as pseudo folliculitis, highly prevalent in this population. Thus, despite the challenges, researchers are actively attempting to develop systems and define parameters for safer and more effective long-term hair reduction for darker skin typed individuals.

Traditionally, it was believed that the matrix area of the hair bulb is solely responsible for follicular regeneration. It followed that there must be irreversible destruction of those stem cells for per-

122

manent hair reduction. Along this logic, laser scientists believe that follicles are most vulnerable to injury by various lasers or light sources during the anagen phase when melanin chromophore is more abundant near those stem cells in the deep dermis. Because the duration of the hair cycle dif- fers for different body sites, repeat treatments are usually done when there is a wave of rapid hair regrowth or between 4 and 8 weeks. However, according to the recent bulge-activation hypothesis, the bulge area of the outer root sheath near the arrector pili muscle insertion contains pluripoten- tial cells, which contributes to the new hair matrix when induced by the dermal papillae during late telogen. Thus, injury to stem cells in the bulge area would lead to follicular destruction. Because the location of the bulge does not change during the follicular cycle, perhaps the anagen phase would not be a prerequisite for laser effect on hair growth. Although some recent clinical data show additive hair reduction from repeat treatments within several days to a couple of weeks of the previous treatment session, the mechanism remains to be elucidated. Perhaps nonanagen hairs were affected. Or alternatively, telogen hairs were induced to start anagen by the first treatment, and the subsequent treatment session affected these hairs that newly began anagen.

As we better understand laser and follicular interaction, a true optimal treatment interval, if there is such, will be derived. In addition, faster treatments with larger spot sizes and/or rapid repetition rate may be anticipated in the coming years. With the refinement of epidermal cooling systems, perhaps treatment of darker and tanned skin will become safer with improved efficacy. Our data on laser hair reduction are limited by the short duration for which this technology has been available. Currently, permanent hair reduction is defined as a significant reduction in the number of terminal hairs that remain stable for a period longer than the complete growth cycle of follicles at a given anatomic site. More long-term results after multiple treatments will truly define the phrase permanent hair reduction.

RESURFACING

The main goal of facial rejuvenation is to even the skin texture and pigmentation. Since the dawn of time, mud packs, fruit extracts, and mechanical exfoliants have been used for these purposes.

LOU A N D GERONEMUS

Table 6. Indications tar Carbon Dioxide Lasers

Aclnic cheilitis Actinic keratoses Adenoma sebaceum DermatosJs papulosa nigra Epidermal nevi Er,/throplasia at Quyerat Facial rhytides Facial scars, including acne, traumatic, varicella Rhinophyma Sebaceous hyperplasia

More recent procedures and better-refined products include creams and peels with hydroxy acids and vitamin A derivatives. These remain relatively limited in their ability to provide dramatic im- provements. Even though phenol peels and dermabrasions are more effective in improving rhytides, they have largely been replaced by resurfacing lasers.

Laser application in dermatology has been based on the theory of selective photothermolysis. For the 10,600 nm light emitted by a carbon dioxide laser, water is the chromophore in skin. Un- fortunately, the continuous-wave carbon dioxide lasers used for skin resurfacing in the 1980s and early 1990s carried a relatively high risk of scarring because of significant thermal diffusion. Al- though laser light penetrates only about 30/xm, its thermal effect reaches about 1 mm because of heat diffusion. The thermal relaxation time of the 30 /xm layer is less than 1 ms. The new short-pulsed, high peak power, rapidly scanned, focused-beam CO 2 lasers with less than 1 ms pulse width are able to provide precise control over the amount of tissue ablation and thermal damage. The high-energy pulsed carbon dioxide and scanned carbon dioxide lasers along with the new Er:YAG lasers will be discussed (Table 5).

A high-energy pulsed carbon dioxide laser is Ultra-Pulse laser (Coherent Laser Carp). It has been shown that about 5 J/cm 2 is needed of the pulsed fluence to ablate skin tissue. With a beam diameter of 2.5 mm, 5 Hz of 30 to 50 millijoules is considered optimal when using the UltraPulse laser. This set of parameters gives 20 to 30 /,m of tissue vaporization and 40 to 120/xm of residual thermal damage. A single pass is expected to result in partial or complete epidermal loss with minimal dermal effect. Dermal vaporization will ensue with additional passes and will be proportional to the pulse energy and total number of passes. In the


human skin, UltraPulse laser will result in 20/xm, 40/xm, and 70/xm of thermal damage after 1, 2, and 3 passes, respectively.

Compared with the UltraPulse laser, the Tru- Pulse (Tissue Technologies, Albuquerque, NM) carbon dioxide laser has higher peak power pulses, but lower average power and shorter pulse durations (30/xs-1000/xs). It is capable of reach- ing fluences over 5 J/cm 2, which is necessary to ablate human skin. Within the 60-100 /xs pulse duration, which is shorter than that which would be capable from the UltraPulse, TruPulse's resultant zone of vaporization with each pass and zone of residual thermal damage are also smaller, about 30/xm and 15 to 30/xm, respectively. Thus, more passes are required for a given depth of ablation, but a thinner layer of residual thermal damage is left behind. Early observations are that there are less oozing, crusting, and erythema with TruPulse laser compared with other carbon dioxide lasers.

A flashscanner using rapidly oscillating mirrors in the handpiece scans a focused continuous-wave laser beam in a spiral pattern across the tissue, thus keeping the laser beam at a given spot for less than 1 ms. With this feature, vaporization is achieved whereas thermal damage is limited to a 40 to 50 /xm radius. SilkTouch (ESC/Sharplan Medical Systems) is equipped with such a scanner that may be programmed to scan 1 to 16 mm diameter and various shapes (circles, ellipses, squares). Depending on the scan size, a cycle of skin resurfacing scan takes 0.2 to 0.45 seconds.

The Er:YAG laser is a relatively new player in skin resurfacing. Its water absorption coefficient is 10 times that of the carbon dioxide laser. It is able to ablate thin layer of tissue with minimal thermal injury as compared with the carbon dioxide laser. Because there is less residual thermal injury compared with carbon dioxide, healing after Er:YAG resurfacing is much faster. Also, there does not appear to be the hypopigmentation seen years after carbon dioxide laser resurfacing. Be- cause of this, resurfacing of isolated cosmetic units should be done with Er:YAG lasers only to avoid a pigment discrepancy and line of demarcation.

Facial rejuvenation of photodamaged skin manifesting in rhytides and actinic keratoses is one of the original and still the primary applications of laser resurfacing technology. However, a long list of other indications exists including a

multitude of benign lesions (Table 6). It is important to note that carbon dioxide resurfacing of anatomic sites other than the face for the purposes of rejuvenation is contraindicated due to the high risk of scarring. Er:YAG laser, however, appears to be safer in non-facial sites when used cautiously.

The two main contraindications of facial resurfacing in a patient who is otherwise medically healthy enough to undergo the procedure are recent systemic isotretinoin use or recent facial surgery or tissue augmentation. Because of the potential adverse effects of isotretinoin on wound healing, it is traditionally recommended to post- pone resurfacing for at least 1 year after dis- continuing the medication. Concomitant facial surgery, such as facelift, or facial tissue augmentation, such as lipotransfer, is not recommended because the incidence of scarring is much higher. A waiting period of at least 6 months is recommended between facial resurfacing and these other procedures.

Patient selection, patient compliance, pretreat- ment and posttreatment skin care, treatment techniques, and close clinical follow-up are all especially critical in optimizing results and minimizing side effects of facial resurfacing. Psycho- logical preparation of the period immediately after treatment and patient expectation of long-term outcome cannot be overemphasized. Fitzpatrick skin types I and II are ideal, with skin types III and IV carrying higher risk of pigmentary alterations. Those undergoing carbon dioxide laser resurfacing should also be warned of the frequent occurrence of mild hypopigmentation of the treated skin years after the procedure. The line a color demarcation is usually more apparent in darker- skinned (skin type III and IV) patients. Prelaser topical tretinoin cream nightly is usually recommended, as such application seems to help minimize milia formation after the procedure. Bleach- ing agents are often recommended for 4 to 6 weeks before surgery for those in the higher risk category for hyperpigmentation. Anti-viral and anti-bacte- rial prophylaxis should always be used starting the day before the procedure and during the entire healing phase until complete re-epithelialization. An intravenous dose of antibiotics is also frequently given intraoperatively. Some laser sur- geons routinely use anti-fungal prophylaxis, but most only administer anti-fungal agents in high-


risk patients or the patients demonstrate fungal overgrowth or infection during the healing phase.

Treatments of cosmetic units are generally per- formed with local anesthesia or nerve blocks. Al- though nerve blocks may be used for full-face procedures, twilight sedation by means of intravenous propafol with the concomitant used of fent- anyl and ketorolac tromethamine (Toradol, Roche Laboratories, Nutley, NJ) administered by an an- esthesiologist offers much greater patient comfort. Supplemental oxygen is not recommended for safety concerns.

Postoperative care ranges from open to closed technique and a combination of both. In the open technique, gauze soaked with water, acetic acid, or hydrogen peroxide are used to soak the treated area followed by an application of a thick layer of ointment such as Aquaphor healing ointment (Beiersdorf-Jobst, Inc, Norwalk, Conn). This pro- cess is repeated several times a day initially but the frequency is decreased rapidly and is stopped after re-epithelialization. This open technique, although labor intensive, has the advantage of allowing potentially earlier detection of infection or other problems than the close technique. The open technique leaves the skin more susceptible to injury such as from scratching. If insufficient ointment is applied, re-epithelialization may be delayed. In the closed technique, a semi-occlusive dressing is secured to the face for up to a week. Advocate of this method claim greater patient comfort and faster healing. However, problems such as potential delayed detection of infection and feeling of claustrophobia by some patients. Some use the occlusive dressing for 1 to a few days followed by the open technique. A new class of dressing in the category of skin substitutes, cul- tured skin fibroblasts, biologic response modifiers such as growth factors and the likes have been used on burn wound and are currently being mar- keted for post-resurfacing use. Because of the high cost of these products, no adequately controlled studies have been done to support any claims of advantage over current methods.

Antiviral, antibacterial, and if desired antifun- gal agents should be continued during the postoperative period until re-epithelialization is complete. Oral analgesics such as Tylenol with codeine (McNeil Pharmaceutical, Rariton, NJ), Vicodin (Knoll Laboratories, Mount Olive, NJ), or Percocet (DuPont Pharma, Wilmington, Del) are

taken on an as needed basis as the pain tolerance ranges widely among patients. Oral steroids, either prednisone 60-100 mg for 3-4 days or a Medrol Dosepak (UpJohn, Kalamazoo, Mich) may be used, but the threshold of administering it should be much higher for patients with a history of oral herpes simplex infections.

The potential complications of facial resurfacing include acute viral/herpetic infection, bacte- rial infection, and yeast overgrowth. Possible long-term side effects include scarring, prolonged erythema, and burning sensation. These may all be minimized by antimicrobial prophylaxis, close clinical observation, and avoiding the above-men- tioned contraindications of resurfacing.

Recently, carbon dioxide followed by 1 to 2 passes of Er:YAG to remove the ablated debris has been studied. This combination results in a thick zone of residual thermal injury which seems to correlate with collagen shrinkage and less healing time than without the Er:YAG passes. Faster re- epithelialization and less thermal injury are seen when the Er:YAG is used to resurface carbon dioxide vaporized skin. In light of the potential benefits of combining the techniques, efforts have been made to design one system that offers both. Derma K (ESC Medical Systems, Needham, Mass) possesses the 250 to 350 microsec Er:YAG and a continuous-wave carbon dioxide lasers. Contour (Sciton, Palo Alto, Calif) is a 2940 nm Er:YAG laser with variable repetition rate and pulse energy combinations to effect thermal damage. How these systems actually fair with the traditional carbon dioxide and Er:YAG lasers in terms of clinical results remains to be seen.

Other new trends in skin rejuvenation include non-laser techniques and non-ablative methods. A radio frequency device (Visage, Palo Alto, Calif) can remove the epidermis leaving a thin zone of dermal thermal damage by a method termed cold ablation. Ultrasound has also been used in skin resurfacing. Nonablative laser treatments of rhytides, also termed subsurfacing, are a promising concept emerging in application. Attempts are being made to heat the dermis to cause fibroplasia and collagen remodeling without epidermal injury. Studies are being done with numerous lasers emitting in the red to infrared ranging up to 1320 nm usually with epidermal cooling systems. Most of these systems target specific dermal chromophores, which in turn act as heat sources stim-


ulating fibroplasia and collagen remodeling. One minor disadvantage exists for those patients with significant sun damage manifesting in lentigines

and solar keratoses as well as rhytides. These nonablative techniques would not be able to treat those epidermal lesions adequately.

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Derrnatologic Laser Surgery

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