Biomedical Engineering Reference
In-Depth Information
(
A
)
(
B
)
Figure 2.24
Venous lake (
A
) before and (
B
) after treatments with alexandrite laser (70 J/cm
2
, 8 mm, 3 ms, 90 ms spray and 80 ms delay with cryogen spray).
Fibrous papules in adults can be treated with vascular-specifi c
lasers or erbium:YAG/CO
2
lasers. More erythematous lesions
respond well to KTP and PDL, whereas more fl esh-colored
lesions respond best to small spot applications of the erbium:YAG
and CO
2
lasers.
circumscriptum, have all been treated with the PDL
(
178
)
.
We have found that purpuric settings work best for these condi-
tions. Newer-generation IPLs with shorter pulse durations that
allow for purpuric settings most likely could be used for all of
these applications. Psoriasis has been treated in a number
of studies. Typical settings are 5-9 J/cm
2
with the PDL at
0.45-1.5 ms. Hern et al. (179) studied the vascular response in
plaques and found a reduction in vessel density and width. Most
of these studies were conducted in the absence of surface cool-
ing and pain was a limitation in some patients. On a practical
level, PDL is best reserved for those patients with a few refrac-
tory red lesions.
Striae Rubra
These lesions respond well to purpuric settings with the PDL,
particularly in lighter patients. We typically use 5-6 J/cm
2
with
1.5 ms, 595 nm, and a 10 mm spot. For narrower lesions, 5 and
7 mm spots can be applied.
Sebaceous Hyperplasia
These lesions may be treated with vascular lasers. In this case,
one is exploiting the small telangiectasia that tends to course
through the lesions, the blood vessel readily apparent upon
dermoscopy. KTP and PDL have been used. We usually use the
3 mm spot PDL with purpuric settings (15 J/cm
2
, 1.5 ms with
DCD). Alternatively, we have used nonpurpuric settings with
the PDL or the KTP laser with a 2 mm spot (15 J/cm
2
, 15 ms; no
cooling) with repeated stacked pulses at 1.5 Hz until the lesion
undergoes a transition from yellow to a gray white color. The
endpoint here is the production of a limited degree of nonspe-
cifi c thermal damage to destroy the sebaceous gland. Photody-
namic therapy is also useful in conjunction with the PDL. With
PDT, the porphyrin (usually ALA or MALA) is absorbed by the
sebaceous gland and is activated by the PDL and/or the blue,
red, and/or IPL light sources (see chap. 3 on PDT).
Molluscum Contagiosum
In a study 19 patients were treated with PDL at setting ranging
from 6 to 7 J/cm
2
, 0.45 ms, 7 mm spot. Almost all patients
responded to one treatment session (180).
Verrucous Hemangioma
Verrucous hemangioma normally occurs on the lower extrem-
ities. The lesions comprise a deeper hemangioma component
and a more superfi cial angiokeratoma component. A recent
report showed successful reduction (181) in the thickness
and redness of the lesions after sequential CW CO
2
laser and
595-1064 nm laser.
Verruca Vulgaris
Verrucae represent benign tumors of epidermal cells induced by
the human papillomavirus. They occur in about 10% of adults
and children. To maintain a proliferative growth, neovascular-
ization is stimulated. This is refl ected histologically in promi-
nent, dilated blood vessels in dermal papillae. Theoretically,
vaporization and coagulation of the new capillaries should halt
viral replication and promote verrucae resolution. The PDL has
been used for about 18 years for warts. Multiple studies support
its use (182-187). Biopsies suggest that both melanin at the
dermal-epidermal junction and capillaries are the targets for
595 nm light. In our experience aggressive settings achieve the
best results (12-15 J/cm
2
with 5 and 7 mm spots) without DCD
(Fig. 2.25). Two to four pulses are given until the lesion turns
gray. Flatter lesions in cosmetically conspicuous areas (face and
backs of hands) should be treated at lower fl uences and a smaller
number of pulses, as scarring and long-term pigment changes
are possible with PDL. We treat aggressively about the nails and
on the palmar and planate surfaces as these areas tend to heal
quickly and any long-term pigment changes are usually incon-
spicuous. Pain can be severe and can be mitigated by topical
Ecchymosis
Ecchymosis (177) has been treated with the PDL with non-
purpuric settings. Normally, a fl uence of 5-6 J/cm
2
is applied at
595 nm with one to two passes (not stacked), 10 ms, and cool-
ing. Care should be taken to not apply too high a fl uence. The
blood fraction in the dermis is quite high and these lesions are
susceptible to blistering and even scarring. The most common
application for this scenario is postfi ller bruising. Early inter-
vention (within 2 days of the bruise onset) will typically clear
the purpura within 1 to 3 days. The IPL can also be used with
similar minimally purpuric settings and has been shown to be
as effective as the PDL.
Inflammatory Skin Diseases
A number of infl ammatory skin diseases where the vasculature
is the primary target have been treated with PDL. For exam-
ple, lupus erythematosis, psoriasis, granuloma annulare, necro-
biosis lipodica diabeticorum, granuloma faciale, lymphangioma
