Lukac_revised2.qxp 19/5/09 2:15 pm Page 58
Aesthetic Dermatology Laser
Novel Fractional Treatments with Variable Square Pulse
Erbium:Yttrium–Aluminum–Garnet Aesthetic Lasers
Matjaz Lukac,
1
Zdenko Vizintin
2
and Tom Sult
3
1. Research Associate, Josef Stefan Institute; 2. Aesthetic Laser Programme Director, Fotona; 3. Medical Director, Laser Aesthetics, Inc.
Abstract
Indications for use of the erbium:yttrium–aluminium–garnet (Er:YAG) laser are continuously expanding. This article discusses the latest
pixel screen technology (PST) fractional technique for minimally invasive Er:YAG skin rejuvenation. PST provides another dimension in the
treatment of various skin conditions, avoiding some of the adverse effects of ablative laser procedures while improving the limited
efficacy of non-ablative treatments. Fractional techniques are based on producing an array of microscopic wounds on the skin surface
that are rapidly re-epithelialised by the surrounding undamaged tissue, thus sparing the epidermis. The advantage of PST over other
fractional technologies is that it allows the laser beam quality and parameters within the individual pixels to remain identical to the basic
beam properties. This enables the practitioner to perform nine basic ablative and one non-ablative treatment at fully clinically tested and
proven laser parameters. Combined with other Er:YAG supporting technologies presented in this paper (smooth and turbo mode), this
provides 11 basic and 11 fractional treatment modalities with the same single-laser source.
Keywords
Fractional, laser resurfacing, variable square pulse (VSP) technology, erbium:yttrium–aluminium–garnet (Er:YAG) laser, erbium, chrome-doped:
yttrium–scandium–gallium–garnet (Er,Cr:YSGG) laser, CO
2
laser, turbo mode, smooth mode, ablative treatment regimes
Disclosure: The authors have no conflicts of interest to declare.
Received: 27 February 2009 Accepted: 26 March 2009
matjaz.lukac@ijs.si
Fractional laser photothermolysis is the latest in a broad range of erbium, chrome-doped:yttrium–scandium–gallium–garnet (Er,Cr:YSGG)
laser techniques to treat ageing and sun-damaged skin. It promises a and CO
2
laser wavelengths operate in the regions of the major
novel means of providing treatments that claim to be as effective as absorption peaks for water. Since the skin consists of 70% water,
traditional erbium:yttrium–aluminium–garnet (Er:YAG) resurfacing these three laser sources can be effectively used for skin tissue
approaches, while further reducing downtime and risk.
1–3
The ablation treatments.
fractional technique is based on the concept of producing an array
of microscopic wounds on the skin surface that are rapidly Closer study of the absorption peaks associated with Er:YAG,
re-epithelialised by the surrounding undamaged tissue, sparing the Er,Cr:YSGG and CO
2
lasers shows differences between their
epidermis in the unaffected areas. This article describes and absorption coefficients in human skin. The optical penetration depth
discusses the latest pixel screen technology (PST) fractional modality of the Er:YAG laser wavelength is approximately 3µm in the skin, while
and technique for minimally invasive Er:YAG skin rejuvenation. those for the Er,Cr:YSGG laser and CO
2
laser wavelengths are 10 and
30µm, respectively. The optical penetration depth defines the smallest
Basics of Ablative Laser Skin Treatments possible skin coagulation depth. While the coagulation depth can be
There are three phases in tissue heating upon irradiation with a laser. increased through indirect heating, it cannot be reduced below the
First, tissue is directly heated within the laser’s specific optical optical penetration depth.
absorption depth. The minimum laser coagulation depth is dependent
on the laser’s specific optical absorption depth. Direct heating is Laser pulsewidth determines the indirect heating depth, and thus
followed by indirect heating, where thermal diffusion indirectly heats the the laser treatment regime. If the energy is delivered to the target
deeper tissues. For shorter laser pulses, the time span for thermal in a very short time-span, ablation occurs before significant heat
diffusion is short and indirect heating does not reach very deeply into diffusion can take place. In this case, less heat is distributed to the
the tissue. For longer pulses, the heat has sufficient time to spread more surrounding tissue. A long pulsewidth will allow more heat transfer
deeply into the tissue. In the third phase, the hottest part of the before ablation takes place, resulting in a greater thermal effect on
irradiated tissue closest to the skin surface is evaporated. In effect, this the surrounding tissue.
reduces the thickness of the thermally affected skin layer.
The ability to control coagulation depth by varying the laser
Wavelength is a key factor in determining the suitability of any laser to pulsewidth is subject to limitations of each particular laser
provide ablative skin procedures in aesthetic treatments. Er:YAG, technology and wavelength. Er,Cr:YSGG lasers are limited due to
58 © TOUCH BRIEFINGS 2009
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