Biomedical Engineering Reference
In-Depth Information
12
Body contouring: Noninvasive fat reduction
Lilit Garibyan, H. Ray Jalian, Mathew M. Avram, and Robert A. Weiss
introduction
The rise in the rate of obesity and the increase in public,
medical, and scientifi c awareness of the disadvantages of excess
adipose tissue have made body-sculpting procedures more
and more popular. Although diet, exercise, and bariatric sur-
geries may effectively control obesity and lead to dramatic
weight loss, oftentimes cosmetic procedures are still necessary
to remove excess fat deposition in selected, more focal areas.
The improvement in shape and smoothness of the human
physique is referred to as “body contouring.” The traditional
method of improving body contour is removal of fat via lipo-
suction and it remains the gold standard in this fi eld. Liposuc-
tion is the most commonly performed procedure worldwide
for excess fat removal and currently is among the top fi ve cos-
metic surgical procedures performed in the USA (1). However,
as liposuction is an invasive procedure there are inherent risks
including postprocedural pain, infection, prolonged recovery,
impaired social downtime, and anesthesia-related complica-
tions (2). All these factors have contributed to patients seeking
less invasive methods for body contouring. Less invasive surgi-
cal techniques such as tumescent liposuction and laser-assisted
lipoplasty are still invasive surgical procedures and therefore
have higher risk compared with noninvasive fat removal. Of
late, multiple different modalities using different methods to
induce adipocyte apoptosis resulting in noninvasive fat reduc-
tion have become available. These modalities primarily aim at
targeting the physical properties of fat that differentiate it from
the overlying epidermis and dermis, thus resulting in selective
removal of fat or lipolysis. Currently available noninvasive fat
removal methods include heating, cryolipolysis, laser, radio-
frequency, and ultrasound sources to more selectively target
adipocytes. This chapter reviews currently available and novel
approaches for noninvasive and intended selective destruction
of fat. Devices utilizing cryolipolysis, lipid-selective wave-
lengths of laser light, thermal focused ultrasound (TFU) and
nonthermal focused ultrasound (NTFU), and radiofrequency
will be reviewed.
popsicle. Histologic analysis of these sites demonstrated pan-
niculitis, which subsequently resolved with a temporary focal
lipoatrophy (3). This report, along with other reports of cold-
induced fat injury, suggests that fat cells are more susceptible to
cold at certain temperatures compared with the surrounding
tissue, particularly dermis (4). This concept of selective suscep-
tibility to cold led to the development of cryolipolysis for the
noninvasive removal of fat and body sculpting.
The initial preclinical animal studies aimed at determining
the feasibility of selective destruction of fat in pigs with local,
noninvasive controlled cooling. In these studies, a Yucatan pig
was exposed to a prototype device with a copper plate cooled
with antifreeze solution at a target temperature of −7°C,
pressed fi rmly against the skin surface. After single treatment
at ten different sites, lasting between 5 and 21 minutes, the ani-
mal was followed for 3.5 months for appearance and persis-
tence of local fat loss. The amount of fat loss was estimated
relative to the adjacent unexposed fat layer thickness. The
results demonstrated that in all 10 sites tested, there was visible
indentation noted, with a maximal relative loss of the superfi -
cial fat layer of nearly 80% (5). In addition, there was lack of
apparent skin injury in the test sites and only one case of tran-
sient hyperpigmentation following the procedure. This selec-
tive loss of fat was not associated with elevated cholesterol or
triglyceride levels when monitored up to 3 months posttreat-
ment (5). This study demonstrated a signifi cant reduction in
fat layer thickness with no damage to skin or associated struc-
tures and no systemic elevation of cholesterol or triglyceride
levels. A subsequent porcine study confi rmed that cryolipoly-
sis led to decreased thickness of the fat layer as measured by
ultrasound and by histology. Histologic analysis showed
approximately 50% reduction in the thickness of superfi cial
fat layer (6). A lobular panniculitis and infl ammatory infi ltrate
was present within the subcutaneous adipose tissue. The
infl ammatory infi ltrate was seen approximately 2 days follow-
ing treatment and was thought to be related to cold-induced
adipocyte apoptosis. This response peaked approximately
1 month after treatment and then declined. The infl ammatory
infi ltrate is predominantly composed of macrophages that
are hypothesized to ingest and clear the apoptotic fat cells.
This process occurs slowly over a period of 90 days posttreat-
ment, with an end result of gradual reduction of fat that is
observed clinically (6). Other hypothesized mechanisms of
action include reperfusion injury following cooling of temper-
ature-sensitive adipocytes, resulting in free radical damage,
oxidative stress, and subsequent cell death (7).
Human clinical studies were conducted utilizing a cup-
shaped treatment applicator with cooling panels on both sides.
cryolipolysis
The selective destruction and noninvasive removal of fat with
cooling is termed “cryolipolysis” (CoolSculpting®, Zeltiq,
Pleasanton, CA). This novel approach for fat removal was
introduced in 2007 and was cleared in 2010 by the U.S. Food
and Drug Administration (FDA) for the treatment of localized
fat of the fl anks and later in 2012 for the abdomen. The con-
cept behind the development of selective cold injury stems
from the clinical observation of “popsicle panniculitis”
reported in infants at the site of prolonged contact with an ice
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