Biomedical Engineering Reference
In-Depth Information
are probably not able to damage clusters or nests of nevomela-
nocytic components. The development of dermal pigment-
targeting lasers (139-141) and IPL systems (142) with long
pulse widths shows encouraging results on the treatment of
these pigmented lesions.
As described previously, multiple, sequential treatments
are typically required for desired cosmetic results of the der-
mal pigmented lesions. Attempts to accelerate treatment
response of dermal pigmentation have been employed
including the use of multiple lasers on the same treatment
session (126,131,143,144) and the application of bleaching
agents prior to laser treatment (145).
Epidermal ablation with a resurfacing laser may enhance the
effectiveness of laser for removing dermal pigmentation by
eliminating competing epidermal melanin and melanocytes,
and removing the epidermis itself, thereby reducing a scatter-
ing of the beam and physically placing it closer to the dermal
target. Thus, a higher delivered energy fl uence will have an
impact on the target-dermal melanin.
To improve the response rate of treating dermal pigmented
lesions, we developed a technique using a combination of
scanned CO
2
and QSRL to treat ABNOMs in a series of 13 Thai
women. A signifi cantly higher percentage of clearing was noted
on the sides treated with a combination of CO
2
and QSRL,
compared with those with QSRL alone (Fig. 13.15) (126). By
combining laser resurfacing and QSRL, a retrospective study in
and suggested that resident macrophages continued scaveng-
ing of laser-damaged pigment cells.
PIH is more common than that of nevus of Ota, occurring
in 50-73% of Asian patients (Fig. 13.5) (129). The benefi t of
using topical bleaching agents to prevent or to treat PIH in
ABNOMs is also controversial. A previous study noted PIH in
73% of the 66 patients who underwent the treatment with a
QS Nd:YAG laser despite the use of topical hydroquinone
(129), whereas another series of 70 patients who developed
PIH following the laser treatment responded readily to topical
hydroquinone within a few days to weeks of application (128).
In our experience, there is little benefi cial effect in using topi-
cal bleaching agents preoperatively to decrease the rate of PIH.
PIH usually persists for 2-3 months even with prompt postop-
erative treatment with hypopigmenting topical medications,
sun-avoidance, and a broad-spectrum sunscreen with an SPF
of at least 30.
As red (QS ruby) and near-infrared (QS alexandrite and QS
Nd:YAG) wavelengths can be selectively absorbed by dermal
pigment, the use of these lasers in the treatment of other mela-
nocytic processes with dermal involvement, including nevus
of Ito (67), Becker's nevus (132), nevus spilus (133), blue
nevus (134), and congenital melanocytic nevus (135-138),
may be effective. The café-au-lait background of nevus spilus
and Becker's nevus frequently recurs after treatment (67). The
short pulse width and low-energy fl uence of these QS lasers
(
A
)
(
B
)
(
C
)
(
D
)
Figure 13.15
(
A
) Acquired bilateral nevus of Ota-like macules in a 40-year-old Thai woman, before treatment. (
B
) Just after epidermal ablation with carbon dioxide
laser. (
C
) Immediately after Q-switched ruby laser irradiation on dermal pigmented lesions. (
D
) Four months after a combined laser treatment.
Source
: From Ref. 126.
