Biomedical Engineering Reference
In-Depth Information
1064- and 1319-nm wavelengths. The ProLipo 1064-nm plat-
form has been approved since July 2007. The 1319-nm compo-
nent was initially FDA approved on December 1, 2008, with a
higher energy system gaining FDA approval on March 6, 2009.
The newest platform is capable of delivering a maximum
energy of 40 W for both the 1064- and the 1319-nm wave-
lengths. The 1064-nm wavelength was selected in this multiplex
system for its affi nity for oxyhemoglobin, while the 1319 nm
for its high absorption of water. In addition, the company
reports that the energy produced from the 1319-nm wavelength
concentrates around the fi ber tip and targets fi brous septae by
damaging associated collagen. The multiplex system may use
differential blending of wavelengths to exert more vascular
effects with the 1064-nm predominance or more skin tighten-
ing effects by favoring the 1319-nm wavelength.
Alexiades-Armenakas conducted a study of the 1064/1319-nm
multiplex LAL device for 12 patients with lipodystrophy and
skin laxity of the submentum and neck (44). Three treatment
arms (1064 nm only, 1319 nm only, and 1064/1319-nm multi-
plex) of the study showed similar degrees of skin tightening.
This study is notable for its use of in situ tissue monitoring to
a target tissue temperature of 45-48°C. No thermal injuries
were reported.
A multiplex LAL device (Cynosure's Triplex Workstation,
Cynosure, Inc.) utilizes three wavelengths: 1064, 1320, and
1440 nm. These wavelengths can be used independently or can
be blended (1064 and 1320 nm or 1064 and 1440 nm) with the
objective of enhancing the effi cacy of lipolysis and improving
skin tightening. This device also includes a subcutaneous tem-
perature monitoring system and motion sensing devices to
minimize overtreatment and thermal injuries.
created less thermal diffusion compared with the other two
wavelengths. The 1064-nm wavelength had intermediate tem-
perature elevation and rate of temperature increase, while the
1320-nm wavelength created the highest temperature diffu-
sivity. These fi ndings would suggest that the 1444-nm wave-
length compared with 1064 nm and 1320 nm has the highest
degree of thermal confi nement to the area treated. These stud-
ies indicate that 1444 nm may be a more effi cient wavelength
for fat destruction. This may decrease work required for fat
lipolysis; however, there is likely less collateral tissue damage.
This effect is desirable when considering a need to protect
nearby vital structures such as nerves and vasculature. How-
ever, if thermal diffusivity creates collateral thermal destruc-
tion and subsequent collagen production and tissue tightening,
this may be a potential limitation of the 1444-nm wavelength.
Further studies are still required to establish safety and effi -
cacy guidelines comparing all of the FDA-approved wave-
lengths utilized for LAL.
technique
Patient workup and preparation are similar to that of the
tumescent liposuction technique. Patients are marked in a
standing position. Patients are prepped in a sterile fashion and
typically given a light sedative medication by the oral, intra-
muscular, or intravenous route. Less commonly, some physi-
cians will perform LAL under spinal or general anesthesia (14).
LAL may be performed independently or in combination
with traditional liposuction. In the majority of cases, tumes-
cent anesthetic fl uid similar to the Klein formulation is infi l-
trated in the area to be treated. Once the infi ltration is
complete, a baseline temperature is taken with an infrared
temperature sensor and small adit sites are created by a direct
puncture technique using a #11 surgical steel blade. The
microcannula housing the laser fi ber is inserted under the skin
into the fat compartment. With currently used devices, the
laser fi ber tip must be advanced outside the cannula tip, usu-
ally by 2-3 mm (12).
Some practitioners begin LAL in the deep fat compartment
fi rst and then move more superfi cially within the adipose layer
in a fan-like motion. A red aiming beam (HeNe) is visible
under the surface of skin, with the intensity increasing as the
laser light becomes more superfi cial. Protective eyewear should
be used by all individuals in the operating room through the
entirety of the procedure. The cannula is moved in a to-and-
fro manner in a fanning pattern at a velocity of approximately
100 mm/s. Some authors stress the need for slow movement of
the cannula through the tissue, to maximize laser-tissue inter-
action (12). The operator's dominant hand is used to propel
the cannula back and forth within the treatment area, while
the nondominant hand is placed on the skin surface for tactile
feedback on the skin surface temperature.
Typical starting temperatures at the skin surface are 26-28°C.
Serial temperature readings are taken during the procedure,
and treatment discontinued in a given area when the skin sur-
face temperature registers 38-40°C or there is a complete loss
of resistance, signaling emulsifi cation of the fat, whichever end
point is reached fi rst. At this clinical end point, the skin feels
moderately warm to touch (21). Areas with a thinner dermal
and adipose layer (e.g., submental area) will reach the target
temperature more quickly, and special care must be taken in
The 1444-nm Device
In 2009 the FDA gave clearance for the surgical incision,
excision, vaporization, ablation, and coagulation of soft tissue
by the 1444-nm device called AccuSculpt™ (Lutronic Inc.,
San Jose, California, USA). The laser system is a neodymium-
doped laser operating on a micropulsed mode (100 µs)
through a 600-µm silica fi ber.
The selection of this wavelength is based on the fact that
both the fat and the water absorption spectra have pronounced
peaks near 1444 nm. Theoretically, this may allow for more
selective, focused destruction of adipocytes in the treatment
area with less thermal diffusion to adjacent tissues (45). A
Korean study conducted by Tark and Song found greater lipo-
lytic effect with the 1444-nm Nd:YAG laser compared with the
1064-nm Nd:YAG laser in an in vivo mini pig and in vitro
human fat experiments (46). However, considering the asso-
ciation between powerful lipolytic effect and thermal damage,
there were theoretical concerns of complications of thermal
burns and oil collection from the 1444-nm laser. A 2012 fol-
low-up porcine study by Youn and Holcomb compared fat
ablation crater depth, tissue mass loss, and thermal tempera-
ture monitoring on ex vivo samples (45). While measuring fat
ablation depth and tissue mass loss, the 1444-nm laser treat-
ment demonstrated the greatest effect, followed by the 1320-
nm laser and then the 1064-nm fi ber. In terms of temperature
changes, laser irradiation by the 1444 nm demonstrated the
least amount absolute temperature elevation and slowest
rate (slope) of temperature elevation, indicating the 1444 nm
