Biomedical Engineering Reference
In-Depth Information
11
Treatment of leg telangiectasias with laser
and high-intensity pulsed light
Mitchel P. Goldman
Lasers have been used to treat leg telangiectasias for various
reasons (1). First, lasers have a futuristic appeal. By virtue of
their advanced technology, lasers are perceived as “state of the
art”. The general public often equates “high tech” with treat-
ment safety and superiority. Unfortunately, as described later,
this perception by both the general public and the physician
has often resulted in unanticipated adverse sequelae (scarring
and pain) and higher costs; lasers cost considerably more in
terms of purchase and maintenance than a needle, syringe,
or sclerosing solution. In addition, lasers have theoretical
advantages compared with sclerotherapy for treating leg telan-
giectasias. Sclerotherapy-induced pigmentation is caused by
hemosiderin deposition through extravasated red blood cells
(RBCs). Laser coagulation of vessels should not have this
effect. In the rabbit ear model, approximately 50% of vessels
treated with an effective concentration of sclerosing solution
demonstrated extravasated erythrocytes, compared with a
30% incidence when treated with the fl ashlamp-pumped
pulsed dye laser (PDL) (Goldman, unpublished observations).
Furthermore, telangiectatic matting (TM), which occurs in a
signifi cant percentage of sclerotherapy-treated patients, has
also not been seen after laser treatment of vascular lesions.
Finally, specifi c allergenic effects of sclerosing solutions are not
a concern when treating telangiectasias with a laser.
Both lasers and intense pulsed light (IPL) have been used to
treat leg telangiectasias. Each acts in a different manner to
induce vessel destruction. Effective lasers and IPL are pulsed so
that their effects act within the thermal relaxation times of
blood vessels to produce specifi c destruction of vessels of vari-
ous diameters based on the pulse duration. Lasers of various
wavelengths and the broad-spectrum IPL are used to selec-
tively treat blood vessels by taking advantage of the difference
between the absorption of the components in a blood vessel
(oxygenated and deoxygenated hemoglobin) and the overlying
epidermis and surrounding dermis (as described below) to
selectively thermocoagulate blood vessels (Fig. 11.1). Each
wavelength requires a specifi c fl uence to cause vessel destruc-
tion. In addition, leg veins are not composed mostly of oxy-
genated hemoglobin, as are port-wine stains (PWSs) and
hemangiomas. They are fi lled with predominantly deoxygen-
ated hemoglobin, hence their blue color. Selective wavelengths
for deoxyhemoglobin as opposed to oxyhemoglobin include
approximately 545 and 580 nm and a broad peak between
650 and 800 nm.
Optical properties of blood are mainly determined by
the absorption and scattering coeffi cients of its various
oxyhemoglobin components. Oxyhemoglobin has three major
absorption peaks at 418, 542, and 577 nm. A less selective
and broader absorption peak spans from approximately 750 to
1100 nm. There is a strong absorption at wavelengths below
600 nm with less absorption at longer wavelengths. However, a
vessel of 1 mm in diameter absorbs more than 67% of light
even at wavelengths longer than 600 nm. This absorption is
even more signifi cant for blood vessels of 2 mm in diameter.
Therefore, use of a light source above 600 nm would result in
deeper penetration of thermal energy without negating absorp-
tion by oxyhemoglobin in vessels greater than 1 mm in diame-
ter. This is because the absorption coeffi cient in blood is higher
than that of surrounding tissue for wavelengths between
600 and 1000 nm. Shorter wavelengths heat only the portion of
the vessel wall closest to the skin surface, which can result in
incomplete thrombosis (2). The only caveat is that wavelengths
greater than 900 nm are less specifi c and also target water, mak-
ing higher fl uences required to produce the desired effects on
oxyhemoglobin, the desired chromophore (3). However, these
higher fl uences can cause unnecessary damage to surrounding
tissue unless adequate cooling measures are employed.
Patients seek treatment for a leg vein largely for cosmetic
reasons (4). Bernstein (5) has evaluated the clinical character-
istics of 500 consecutive patients presenting for laser removal
of lower extremity spider veins. Patients ranged in age from
20 to 70 years and had had noticeable spider veins for an aver-
age of 14 years. Twenty-eight percent of patients had leg veins
less than 0.5 mm in diameter; 39% of patients had veins less
than 1.5 mm in diameter. Fifty-six percent of patients who had
had sclerotherapy (not stated how this was performed) devel-
oped TM. Therefore, any treatment that is effective should be
relatively free of adverse sequelae. With recent advances, lasers
or IPL systems have become methods for treating telangiec-
tatic vessels with a minimum of adverse effects. However, for
these advanced treatments to be effective and safe, they must
be used appropriately.
Sclerotherapy has a number of potential adverse effects.
Up to 30% of patients treated with sclerotherapy develop post-
sclerosis pigmentation (6) and/or TM (7). As discussed earlier,
at least one study determined that TM developed in 56% of
patients who presented for laser treatment of leg veins (5).
These adverse effects can occur even with optimal treatment
but are more common when an excessive infl ammatory reac-
tion occurs. To minimize risks of an infl ammatory response,
lasers and IPL act by producing thermal damage with the ulti-
mate goal being vaporization of the targeted vessel. When used
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