Biomedical Engineering Reference
In-Depth Information
Table 3.1
Laser Selection for Different Types of Pigmented Lesions
Pathology Lesion Type Preferred Laser Choices
Epidermal Lentigo FD QS Nd:YAG (532 nm)
Café-au-lait macule QS ruby (694 nm)
Ephelide QS alexandrite (755 nm)
Junctional nevus LP alexandrite (755 nm)
Nevus spilus KTP (532 nm)
Seborrheic keratosis QS ruby (694 nm)
Epidermal-dermal Melasma QS ruby (694 nm)
QS alexandrite (755 nm)
FD QS Nd:YAG (532/1064 nm)
Erbium (2940 nm)
CO
2
(10,600 nm)
IPL
Becker's nevus Combination of two lasers
Hair removal laser appropriate for skin and hair type
Pigment-specifi c laser such as QS ruby, alexandrite, or Nd:YAG
Dermal Congenital nevus Laser treatment should be undertaken with caution
Acquired nevus Laser treatment should be undertaken with caution
QS ruby (694 nm)
QS alexandrite (755 nm)
FD QS Nd:YAG (532/1064 nm)
LP alexandrite (755 nm)
Diode (810 nm)
Nevus of Ito/nevus of Ota QS ruby (694 nm)
QS alexandrite (755 nm)
QS Nd:YAG (532/1064 nm)
Blue nevus Laser treatment should be undertaken with caution
QS ruby (694 nm)
QS alexandrite (755 nm)
QS Nd:YAG (1064 nm)
Abbreviations
: FD, frequency doubled; KTP, potassium titanyl phosphate; LP, long pulse; QS, Q-switched.
Lentigines
Lentigines are small, irregular but sharply marginated brown
macules. Solar lentigo (lentigo senilis) is an acquired lentigo
resulting from sun exposure. These lesions increase in number
with advancing age and are usually related to the extent of past
sun exposure, but are not premalignant. Histologically, these
lesions have elongated rete ridges that extend into the underlying
papillary dermis. The basal cell layer of the epidermis often shows
hypermelanosis with an increased number of basal melanocytes.
Lentigines can also be a component of different cutaneous
syndromes, including lentiginosis profusa, Peutz-Jeghers syn-
drome, Moynahan syndrome, and LEOPARD (multiple lentigi-
nes) syndrome. In these syndromes, the histology of the lentigo is
identical to that of a normal lentigo simplex, or slightly different,
with the fi nding that basal melanocytes are not always increased
in number as with other lentigines. In addition, in Peutz-Jeghers
syndrome, the melanosomes are deeply melanized. Giant macro-
melanosomes are found in the cells of the LEOPARD syndrome.
The three QS lasers and 532-nm potassium titanyl phosphate
(KTP) laser have demonstrated effi cacy in the clearance of len-
tigines (15,18-24), as well as the noncoherent, broadband, IPL
source (25). For the QS lasers, one should utilize a 2- to 4-mm
spot with a fl uence that produces brisk whitening without epi-
dermolysis. Owing to concomitant hemoglobin absorption
when using the 532-nm wavelength, purpura may ensue.
Although the purpura generally resolves, residual erythema may
be noted for the fi rst month postoperatively. The 532-nm KTP
laser will immediately darken the lesion, which will then peel off
approximately 7 days later if on the face and 10-14 days later if
on the body. Purpura is not a factor as the longer pulse width
does not cause bruising. The IPL should be set so that normal
skin pigment is protected, but the treated lesions darken with
treatment. A study on Asian patients with lentigines showed
that both QS and microsecond, long
-
pulsed 755-nm alexandrite
lasers were equally effective, although the longer pulse width was
associated with less postinfl ammatory hyperpigmentation (26).
Case 1
Lentigo
A 28-year-old woman presented with a lentigo over her left cheek, which had failed to improve with topical hydroqui-
none and liquid nitrogen treatment (Fig. 3.1A). The treatment plan included IPL, daily application of sunblock, and
nightly application of hydroquinone. The lesion was treated at the time of the initial visit with two passes of IPL; the fi rst
pass at 32 J/cm
2
and the second one at 36 J/cm
2
. At the 5-week follow-up appointment, complete clearing of the lentigo
was noted (Fig. 3.1B).
