Biomedical Engineering Reference
In-Depth Information
(
B
)
(
A
)
Figure 6.19
Improvement in loose, folded tissue of photodamaged lower-eyelid skin usually occurs primarily from collagen tightening. (
A
) Before therapy;
(
B
) 4 months after CO
2
laser resurfacing.
(
A
)
(
B
)
Figure 6.20
Atrophic acne scars may respond dramatically to a single treatment with CO
2
laser by using collagen tightening selectively and artfully to elevate scars.
(
A
) Before treatment; (
B
) 4 months after CO
2
laser resurfacing.
Multipulse Coagulation
The most effi cient fl uences for vaporizing the epidermis have
been shown to be in the range of 5-19 J/cm
2
. Single-pulse
vaporization generally uses fl uences of about 7 J/cm
2
. How-
ever, when one pulse is stacked on top of another without suf-
fi cient tissue cooling time, additive thermal effects occur.
When using the CPG with the UltraPulse laser, a density of 9
results in as high an energy density as 60 J/cm
2
to be delivered
to the tissue. It has been clinically observed that after making
three or four passes with the UltraPulse laser using CPG densi-
ties of 4-6, nothing visible appears to occur to the tissue. Nei-
ther the depth of vaporization nor the thermal injury appears
to be increasing. Biopsy studies confi rm this impression as
long as single-pulse vaporization is being used (100).
