Biomedical Engineering Reference
In-Depth Information
( A )
( B )
( C )
Figure 7.10 Hand ( A ) before, ( B ) immediately after one treatment (fractional carbon dioxide, 20% coverage, 150-μm depth), and ( C ) 1 month later.
Melasma/Hyperpigmentation/Hori's Nevus
Although disorders of pigmentation have traditionally been
treated by either selective or nonselective destructive methods,
fractional lasers can be applied as an adjunct therapy or used in a
series of treatments to achieve at least partial pigment improve-
ment. When used alone, ablative fractional lasers only produce
temporary resolution of pigmented lesions since the majority of
the pigmented cells are not vaporized; pigmentary dyschromia is
often reestablished after a few months. Ideally one can combine a
deep small spot, low-density technique with a larger spot more
confl uent technique (i.e., total FX). Alternatively, one can pre-
treat the skin with an IPL or Q-switched alexandrite laser for pig-
ment followed by ablative fractional treatment on the same day.
coverage per pass for two passes with 120-
m spot Deep FX
system. Healing requires about 10 days (Fig. 7.12).
The variable density of scarring, issues with dyspigmentation,
and ongoing acne eruptions conspire to produce outcomes that
may prove to be less than optimal. Also, many acne scarring
patients are young adults who are unable to tolerate the pro-
longed downtime after an ablative procedure. Unlike photoag-
ing, especially wrinkles, where ablative fractional lasers show a
clear advantage over nonablative lasers, acne scarring (boxcar
type) appears to respond almost as well to a series of four to fi ve
nonablative sessions as one to two ablative fractional treat-
ments. One study compared CO 2 and 1550 nm in acne scars in
type IV skin and found similar effi cacy in the two systems (27).
μ
 
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