Biomedical Engineering Reference
In-Depth Information
(
A
)
(
B
)
(
C
)
(
D
)
(
E
)
Figure 4.9
Skin type V. (
A
) Black ink in a patient with skin type V; (
B
) after one treatment with neodymium-doped:yttrium-aluminum-garnet at 1064 nm;
(
C
) after two treatments; (
D
) after three treatments; and (
E
) after four treatments, there is complete ink resolution and no adverse side effects.
broad-spectrum sunscreens (Fig. 4.10). Hypopigmentation is
a function of the wavelength used but is more apparent in
darker skin types. Repigmentation of post-laser hypopigmen-
tation can be promoted with phototherapy or ultraviolet-
range lasers but often responds slowly with no treatment at all.
Increased melanin absorption seen with shorter wavelengths
increases the risk for hypopigmentation. Permanent depig-
mentation is also a rare possibility.
Permanent tissue textural changes, scarring, hypertrophic
scarring, and keloid scars are rare. Scarring has been reported,
however, following Q-switched laser treatment of combustible
materials in the case of traumatic gunpowder tattooing and
with dense pigment deposition in the case of “double tattoos,”
where a preexisting tattoo is overlaid with a second tattoo
(240,241). Transient textural changes are often noted but
resolve within 1-2 months. If a patient is more prone to this,
longer treatment intervals are recommended. That noted,
patients should be aware that preexisting tissue changes and
scarring from the original tattoo placement is unlikely to
improve with the corresponding ink reduction from laser tat-
too removal. Bulla (Fig. 4.11), while disconcerting to patients,
typically heals with no long-term sequel (242).
As noted earlier, allergic reactions to tattoo pigment before
(39,243) as well as after Q-switched laser treatments are pos-
sible (244). Unlike the destructive modalities previously
described, Q-switched lasers mobilize the ink and may gener-
ate a systemic allergic response. If an allergic reaction to the
ink has been noted, Q-switched laser treatment is not advised.
There is no evidence, to date, of systemic toxicity reactions in
vivo following laser treatment of tattoos; however, studies on
chemical and photophysical analysis do find some evidence
that potentially hazardous compounds can be liberated from
laser treatment of tattoo pigment in vitro (245,246).
Paradoxical tattoo ink darkening has been noted following
Q-switched laser treatment. While this phenomenon can occur
with any colored ink, it is more common with red, white, and
flesh-toned inks, although darkening of pink ink (247) and yel-
low ink has also been reported (248). In vitro tests with various
