Biomedical Engineering Reference
In-Depth Information
tissues revealed clearly demarcated zones of necrosis visible on
gross inspection of the treatment areas. The overlying dermis
and epidermis were intact with no evidence of injury. Immedi-
ately after treatment, adipocyte necrosis was present in histo-
logic specimens. Two weeks following treatment, a localized
infl ammatory infi ltrate consisting primarily of scavenger mac-
rophages is observed. It is presumed that these macrophages
engulf cellular debris and extracellular lipids released from
necrotic adipocytes, as lipid-laden macrophages were present
within the treatment zone. The infl ammatory and healing
process is completed in about 14 weeks after treatment, which
is the time that clinical reduction in fat is also observed (18).
From the limited clinical data available thus far, TFU has
demonstrated a favorable safety profi le when used for body
contouring. Prolonged tenderness, edema, ecchymosis, and
hard lumps were seen in less than 12% of patients. Impor-
tantly, all adverse events resolved within 1-3 months after
treatment. Some treatments were terminated due to excessive
pain during the treatment, but this pain resolved completely
upon the termination of treatment (18,19). This illustrates the
difference between thermal and NTFU, with nonthermal
being much less painful during treatment application. Impor-
tantly, like all the devices used to affect adipocytes, TFU did
not lead to elevation in serum lipid levels or liver function tests
in multiple clinical studies. The fi rst- and second-generation
HIFU devices received FDA clearance in 2011 for body
contouring.
Figure 12.6 An FDA cleared multiple head, low-level laser therapy device for
fat reduction. Source : Courtesy of Zerona.
on objective ultrasound or 3D imaging modalities. Critics
have also noted the short follow-up time of these studies.
A nonrandomized, uncontrolled retrospective study analyzed
data from 689 patients who had the LLLT procedure to evalu-
ate the circumferential reduction across the treatment site of
the waist, hips, and thighs as well as untreated systemic regions
(24). They reported a mean circumferential reduction in all
treated sites 1 week after the treatment regimen of 3.27 inches.
Most importantly, reduction was not attributed to fl uid or fat
relocation as all measurement points, including the untreated
areas, demonstrated circumferential reduction. Study subjects
were not asked to abstain from receiving any other treatment
to promote body contouring and/or weight loss while receiv-
ing LLLT. Subsequent investigator-initiated trials using the
same device with less number of patients failed to show statis-
tically signifi cant reduction in fat using waist circumference
and more objective ultrasound measurements of fat layer
thickness (22).
low-level laser therapy
The use of low-level light to affect cell biology and metabolic
activity is termed photomodulation. The modulation of cell
activity is believed to be the effect on mitochondria cell organ-
elles. It is believed by some that low-level light may infl uence
adipocytes making their membranes less stable. Low-level
laser therapy (LLLT; Zerona™, Erchonia) claim for fat reduc-
tion was based on in vivo observation that a 635-nm laser
caused a transitory pore within adipocytes, leading to defl a-
tion of the adipocyte through the release of lipids into the
interstitial space. The theory was that this pore does not dam-
age the cells but allows for the effl ux of lipid contents from the
cell into the interstitial space (21). The mechanism of action was
thought to result from photoexcitation of cytochrome- c oxi-
dase, an enzyme component of respiratory chain within the
mitochondria as in other LLLT devices (22). LLLT received FDA
clearance in 2010 for fat reduction (Fig. 12.6).
Several commercial devices are available and are various
iterations of multiple low power laser diode modules operat-
ing at a wavelength of 635 nm. Current treatment recommen-
dations are to undergo six to eight sessions, each lasting up to
30 minutes. In addition, some device manufacturers recom-
mend concomitant proprietary nutritional supplements
aimed at enhancing the lymphatic and circulatory systems.
Although numerous studies exist on the role of laser-induced
adipocyte modifi cation as an adjunct to liposuction, there are
limited data regarding the use of LLLT alone for fat reduction.
The results from the limited number of studies are mixed. An
initial, double-blind, placebo-controlled trial demonstrated
an overall combined reduction of 3.51 inches when the results
of all treatment sites (waist, hip, and thighs) were combined
together, compared with 0.6 inches in the control group (23).
This is based on subjective circumference measurements, not
infrared lasers
Infrared lasers use the concept of selective photothermolysis to
specifi cally target fat. This involves the selection of a wave-
length of light and pulse duration that can selectively heat up
adipose tissue without damage to the surrounding tissue. Indi-
vidual chromophores within the target tissue allow confi ne-
ment of heat, specifi cally within target tissue. Infrared bands
have been found to be useful for the selective targeting of
lipid-rich tissues such as fat. The absorption spectrum of fat
has two unique peaks at 1210 and 1720 nm, which were greater
than that of water. It has been demonstrated that exposure of
intact, full-thickness porcine tissue samples to infrared lasers
with a wavelength of 1210 nm causes reproducible thermal
damage to subcutaneous fat without injuring the overlying
skin or surrounding tissues (25).
 
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