Biomedical Engineering Reference
In-Depth Information
(
A
)
(
B
)
Figure 2.13
Small angioma (
A
) before and (
B
) just after treatment with 4 mm adaptor that fi ts over 10
×
15 mm crystal. The adaptor allows for placement in hair-
line without damaging hair.
vary among manufacturers. Accordingly, comparison of set-
tings between various manufacturers is diffi cult, as actual sur-
face fl uences will not always be equivalent among manufacturers
even when the user interface indicates like-settings. In the case
of IPL, changes in lamp pumping can affect the pulse profi le
and spectral emission, so that simple changes in the fl uence
typically will involve a change in another parameter (21-23).
Also, various manufacturers' IPLs emit different output spectra
and the “fl uence” listed on the user interface is normally that of
the whole output. Without knowledge of the exact spectrum
and subsequent calculation of the laser equivalent tissue effect,
predicting IPL responses in the skin is more diffi cult. Some
physicians lament the IPL as a poor replacement for laser, even
in the treatment of pigmented lesions and vascular lesions.
However, modern IPLs can achieve very selective vascular and
pigment heating; moreover, most IPLs incorporate cooling
technologies (sapphire contact plate or cryogen spray), making
them much safer than in previous years. For discrete lesions,
IPLs can be optimized by using small spots. Cutera (Brisbane,
California, USA) and Lumenis (Santa Clara, California,
USA) manufactures a small spot IPL (Fig. 2.5), and Palomar
manufactures a clip on adaptor that converts a 10 × 15 mm
spot to a 4 mm round spot (Fig. 2.13). Another way to increase
effi cacy of millisecond technologies is to use a “mask” with an
aperture that is roughly the size of the pigmented lesions or
vessels. Accordingly, skin outside the hole in the plastic mask
is preserved.
Figure 2.14
Small 980 nm laser for vessels. The whole unit weighs less than
5 pounds.
Varia laser (New Star Lasers, Rosemont, California, USA)
found greater than 75% improvement in 97% of treated sites
with a 125-150 J/cm
2
fl uence through a 6-mm-diameter spot
and 25-ms pulse duration for small diameter vessels and 75- to
100-ms pulse durations for facial reticular veins. All treated
reticular veins including periorbital and temporal veins
resolved 100%. One or two passes were required to achieve
vessel spasm or coagulation (24).
Another long-pulse 1064 nm laser uses precooling through a
copper contact probe and demonstrated moderate to signifi cant
vessel improvement in 80% of patients (25). This laser (Cool-
Glide Excel/Xeo, Cutera, Burlingame, California, USA) is used
at 120-170 J/cm
2
with a 3-mm-diameter spot size and 5- to
40-ms pulses until vessel blanching or coagulation occurs.
These patients received two treatments 4 weeks apart to achieve
therapeutic effi cacy. Cutaneous blistering and scarring with
2- to 3-mm depressions and/or hypopigmentation were
reported in this study. Bulk heating is (see fi gure 20
in chap. 1) likely in 1064 nm treatment of telangiectasia
940 nm Diode-Pumped Laser
This laser (Medilas D SkinPulse; Dornier MedizinLaserGmbH,
Germering, Germany) and Vari-lite (Cutera, California, USA)
has been reported to be effective at clearing 1- to 3-mm-
diameter periocular vessels in 86% of patients when used
at 141 J/cm
2
, 20-ms pulse through a 3-mm-diameter spot
size (24). Also, a 980 nm miniaturized diode laser is available
that weighs under four pounds (Fig. 2.14).
1064 nm Long Pulse Nd:YAG Laser
Using this wavelength requires fl uences over 10 times that used
with 532 and 595 nm lasers since the absorption of Hb and
HbO
2
at 1064 nm is 10 times less. These higher fl uences neces-
sitate epidermal cooling. One laser uses cryogen spray cooling
to achieve epidermal protection. A study using the CoolTouch
