Investigational – Better Vessel Treatment with Two Pulse, Two color
Laser System

Laser companies are trying to continually improve the specificity
and effectiveness of their laser systems.  There is a very
interesting dual laser system that contains two color (wavelengths)
that has the best photocoagulation rates of any laser to date.  The
first laser pulse changes the hemoglobin into met-hemoglobin (a much
better target for laser) and the second pulse destroys the blood
vessel through targeting of met-hemoglobin.  Human clinical trials
have already started in Arizona.  What took 5 treatments in the past
may only take one treatment.  Very interesting.  A little bit
technical – drop down to summary if you want to bypass the tech talk.




Cooperative Phenomena in Two-Pulse, Two-Color Laser Photocoagulation
of Cutaneous Blood Vessels

John F. Blacka, Jennifer Kehlet Bartonb#, George Frangineasa, and
Herbert Pummera


ABSTRACT

A novel laser system has been developed to study the effects of
multiple laser pulses of differing wavelengths on cutaneous blood
vessels in vivo, using the hamster dorsal skin flap preparation. The
system permits sequenced irradiation with well-defined intrapulse
spacing at 532 nm, using a long pulse frequency doubled Nd:YAG
laser, and at 1064 nm, using a long pulse Nd:YAG laser. Using this
system, we have identified a parameter space where two pulses of
different wavelengths act in a synergistic manner to effect
permanent vessel damage. Using a two-color pump-probe technique in
vitro, we have identified a phenomenon we call green-light-induced
infrared absorption (GLIIRA), where a pulse of green light causes
photochemical and photothermal modifications to the chemical
constituents of blood and results in enhanced infrared absorption.
We identify a new chemical species, met-hemoglobin, not normally
present in healthy human blood but formed during laser
photocoagulation which we believe is implicated in the enhanced
vessel photocoagulation.

Keywords: Selective photothermolysis, telangiectases, oxy-
hemoglobin, met-hemoglobin, Nd:YAG laser.


Summary:

We have shown that two sequential laser pulses, one of 532 nm
(green) light and one of 1064 nm (near infrared) light, when applied
to cutaneous vessels with an appropriate time delay, can produce a
photocoagulation effect greater than that which would be expected
from the individual isolated pulses. In vitro experiments have shown
that photochemically-induced changes in the blood cause an
enhancement of the absorption of red and near-infra-red wavelengths.
We have implicated the production of met-hemoglobin as contributing
to the enhancement of IR absorption. These observations offer
intriguing possibilities for treatment of vascular disorders in
humans, specifically a reduction in the total radiant exposure
required for treatment, and a concomitant reduction in potential
adverse side effects and pain associated with the procedure. Future
work will include using a high-speed thermal imaging camera to
determine the temperature at which the met-Hb reaction starts, which
may in turn allow extraction of the activation energy for the
reaction. Clinical trials in humans are underway.

Regards,

Geoffrey
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Dr. Geoffrey Nase
Ph.D. Neurovascular Physiologist
http://www.drnase.com
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