U.S. patent application number 11/225821 was filed with the patent office on 2006-03-30 for laser treatment of cutaneous vascular lesions.
Invention is credited to Jennifer K. Barton, Eric K. Chan, Thomas E. Milner, Gracie Vargas, Ashley J. Welch.
Application Number | 20060069166 11/225821 |
Document ID | / |
Family ID | 30772747 |
Filed Date | 2006-03-30 |
United States Patent
Application |
20060069166 |
Kind Code |
A1 |
Vargas; Gracie ; et
al. |
March 30, 2006 |
Laser treatment of cutaneous vascular lesions
Abstract
Methods for treating maladies such as cutaneous vascular
lesions. A patient in need of vascular lesion treatment is
identified. A hyperosmotic agent is administered to a region
adjacent the lesion. Blood flow velocity is slowed within the
region using the hyperosmotic agent, and the lesion is exposed to
laser radiation.
Inventors: |
Vargas; Gracie; (Galveston,
TX) ; Barton; Jennifer K.; (Tucson, AZ) ;
Chan; Eric K.; (Lexington, MA) ; Milner; Thomas
E.; (Austin, TX) ; Welch; Ashley J.; (Austin,
TX) |
Correspondence
Address: |
FULBRIGHT & JAWORSKI L.L.P.
600 CONGRESS AVE.
SUITE 2400
AUSTIN
TX
78701
US
|
Family ID: |
30772747 |
Appl. No.: |
11/225821 |
Filed: |
September 13, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10385195 |
Mar 10, 2003 |
6942663 |
|
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11225821 |
Sep 13, 2005 |
|
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60363726 |
Mar 12, 2002 |
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Current U.S.
Class: |
514/738 ;
606/49 |
Current CPC
Class: |
A61B 2018/00452
20130101; A61B 18/203 20130101; A61K 31/045 20130101 |
Class at
Publication: |
514/738 ;
606/049 |
International
Class: |
A61K 31/045 20060101
A61K031/045; A61B 18/18 20060101 A61B018/18 |
Goverment Interests
[0002] Aspects of this invention were made with government support
of the National Science Foundation, grant number BES9986296.
Further support has been provided by Texas Higher Education
Coordinating Board, grant number BER-ATP-253. Accordingly, the
government may have certain rights in this invention.
Claims
1. A method for reducing the amount of radiation required to
destroy a blood vessel of a cutaneous vascular lesion comprising
administering a hyperosmotic agent to the blood vessel to slow
blood flow velocity prior to exposure to laser radiation.
2. The method of claim 1, wherein the amount of radiation is
reduced by at least 15%.
3. The method of claim 1, wherein blood flow velocity is slowed by
at least 15%.
4. The method of claim 1, wherein blood flow velocity is slowed to
zero.
5. The method of claim 1, wherein administering comprises
injection.
6.-31. (canceled)
Description
[0001] This application claims priority to, and incorporates by
reference, U.S. Provisional Patent Application Ser. No. 60/363,726
filed Mar. 12, 2002 entitled "Laser Treatment of Cutaneous Vascular
Lesions."
BACKGROUND OF THE INVENTION
[0003] 1. Field of the Invention
[0004] The present invention relates generally to biomedical
engineering, imaging, medicine, and medical treatment. More
particularly, it concerns clinical laser treatment of cutaneous
vascular lesions using chemical agents that not only increase light
penetration but also decrease blood flow velocity.
[0005] 2. Description of Related Art
[0006] Cutaneous vascular lesions can be classified into two main
categories. The first includes benign disorders, such as the
hemangioma (a benign tumor consisting of a dense mass of blood
vessels) and the cutaneous nevus (a congenital discoloration of a
skin area, also called a strawberry or stork mark) [van Gemert et
al., 1995; Mulliken, 1992]. The second category is made up of
vascular malformations, where the lesion is caused by abnormal
blood vessel pathology [Mulliken, 1992]. Included in this class of
cutaneous vascular lesions is the port wine stain (PWS), a
congenital lesion in which ectatic capillaries make an area appear
a dark red color and produce raised nodules protruding above the
normal skin surface. Another vascular malformation is leg
telangiectasia, small, localized clusters of blood vessels
sometimes found deep (millimeters) below the surface.
Telangiectasis can also occur as an extensive network that is much
more widespread [Goldman, 1992].
[0007] Some of these lesions, such as the port wine stain (PWS),
can be quite traumatic for a patient, resulting in serious
psychological and social problems [Lanigan et al., 1989; Tan, 1992;
Morelli et al., 1992; Masciarelli, 1992; van Gemert, 1992]. When
lesions are located near joints, lips, or the eyes they can also
interfere with normal functions and lead to serious problems such
as hypertrophy of skeletal tissue or more severe conditions
[Mulliken, 1992]. Because the lesions become increasingly
hypertrophic, early treatment is preferred.
[0008] Currently, the only accepted treatment for these vascular
lesions is pulsed laser radiation at selected wavelengths that
target the absorption characteristics of hemoglobin. By selecting
the proper laser pulse duration, the process is referred to as
selective photothermolysis. Blood vessels are damaged by the
increase in temperature resulting from absorption of pulsed laser
light. The objective is to permanently destroy the blood vessels
comprising a cutaneous lesion, while sparing surrounding skin
structures.
[0009] A number of shortcomings exist in current clinical
treatments due to the lack of parameter optimization and sufficient
delivery of light to deep lying blood vessels. Unfortunately,
because the treatment parameters governing the effectiveness of
laser therapies vary greatly from patient to patient, many
instances of incomplete destruction of abnormal vessels and
clearing of the lesion occur.
[0010] In general, low treatment success rates remain a problem
with existing laser treatments of vascular lesions. This low
success rate is due to at least two main limitations: (a)
restrictions in the achievable penetration depth of light in
biological tissue and (b) insufficient increase in blood vessel
temperatures associated with high flow velocities.
[0011] The first limitation (limitation (a)) in the laser treatment
of cutaneous vascular lesions involves rapid attenuation of
incident light with depth. Attenuation of laser light in biological
media occurs by absorption and scattering. In many cases, deep
blood vessels in a lesion are not sufficiently heated by incident
light due to competition from absorption and scattering by other
tissue constituents. This competition for laser light decreases the
fluence rate [W/cm.sup.2] available for photocoagulation of a blood
vessel. In view of this limitation, methodologies that decrease
light attenuation and increase the penetration depth of incident
light are desirable.
[0012] The second limitation (limitation (b)) in the laser
treatment of vascular lesions involves the lack of control of blood
flow velocity. Blood flow velocity has been shown to be an
important factor that affects the success of vessel
photocoagulation. Specifically Boergen, et al. have shown that
complete flow cessation of blood in vessels before laser
irradiation significantly decreases the fluences required to
permanently destroy a blood vessel [Boergen et al., 1977]. Despite
this realization, current laser treatment techniques have not been
able to fully capitalize upon the benefits afforded by controlling
blood flow velocity during treatment. In view of this limitation,
methodologies that not only decrease light attenuation, but also
decrease blood flow velocity would be desirable.
[0013] The referenced shortcomings of conventional methodologies
mentioned above are not intended to be exhaustive, but rather are
among many that tend to impair the effectiveness of previously
known techniques concerning the laser treatment of cutaneous
vascular lesions. Other noteworthy problems may also exist;
however, those mentioned here are sufficient to demonstrate that
methodology appearing in the art have not been altogether
satisfactory and that a significant need exists for the techniques
described and claimed herein.
SUMMARY OF THE INVENTION
[0014] Shortcomings of the prior art are reduced or eliminated by
the techniques disclosed herein. These techniques are applicable to
a vast number of applications, including but not limited to
applications involving the laser removal of cutaneous vascular
lesions.
[0015] Procedures described herein are able to reduce the laser
dose required for irreversible photocoagulation of blood vessels in
tissue. Each of the two main limitations of conventional
techniques, discussed above, are addressed by using a specific
class of chemical agents together with application of laser
radiation to blood vessels. Required fluences for the permanent
destruction of blood vessels in the skin are significantly lower
with the techniques of this disclosure as compared to cases where
no chemical agents are used. Experimental results substantiating
the assertions of this disclosure are presented in the Examples
section.
[0016] In a recent study, the inventors discovered that the
addition of glycerol, and other chemical agents, to skin leads to
changes in blood vessel morphology. In particular, glycerol alters
the flow characteristics of blood in the skin. In the study,
glycerol was added to the subdermal side of skin in which blood
vessels were located 80-100 .mu.m from the subdermal surface.
Within twenty minutes, the flow in venules (approximately 100-400
.mu.m in diameter) ceased. Over prolonged periods of exposure to
glycerol, flow in arterioles ceased as well. When the skin was
hydrated in a physiologic saline solution, flow in arterioles and
venules returned to physiologic values. In the experience of the
inventors, the addition of glycerol, and the other hyperosmotic
agents described herein, to blood vessels did not result in any
permanent vessel damage.
[0017] These recently-discovered morphological effects of glycerol
(and other agents) on blood flow velocity, coupled with glycerol's
ability to increase light transmission within turbid media (i.e.,
glycerol's "optical clearing" properties), serve as one basis for
an effective, new methodology for vastly improved laser treatment
of cutaneous vascular lesions. First, increased light penetration
due to glycerol and other hyperosmotic agents allows for better
localization of light on deep blood vessels that previously would
not have been targeted. Second, decrease in blood flow velocity due
to glycerol allows for significantly lower radiant light exposures
to be used for blood vessel photocoagulation.
[0018] In one embodiment, the invention is a method for reducing
the amount of radiation required to destroy a blood vessel of a
cutaneous vascular lesion. The method involves administering a
hyperosmotic agent to the blood vessel to slow blood flow velocity
prior to exposure to laser radiation.
[0019] In another embodiment, the invention is a method of treating
a cutaneous vascular lesion. A patient in need of vascular lesion
treatment is identified. A hyperosmotic agent is administered to a
region adjacent the lesion. Blood flow velocity is slowed within
the region using the hyperosmotic agent, and the lesion is exposed
to laser radiation.
[0020] In another embodiment, the invention is a method of
destroying a blood vessel. A hyperosmotic agent is administered to
the blood vessel to reduce blood flow velocity by at least 15%, and
the blood vessel is exposed to an amount of laser radiation at
least 15% less than an amount of radiation required to destroy a
blood vessel in the absence of the administration of the
hyperosmotic agent.
[0021] As used herein, "amount of radiation" simply means any
measure of radiation being used to treat a lesion or other malady.
In one embodiment, the "amount of radiation" may be measured with
reference to energy per unit area, such as J/cm.sup.2. As used
herein, "adjacent" shall be interpreted broadly to mean not only
"close to," but also overlapping with (completely or partially).
Thus, an agent administered "adjacent" a region may be administered
near or at that region.
[0022] Other features and associated advantages will become
apparent with reference to the following detailed description of
specific embodiments in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The following drawings form part of the present
specification and are included to further demonstrate certain
aspects of the present invention. The invention may be better
understood by reference to one or more of these drawings in
combination with the detailed description of specific embodiments
presented herein.
[0024] FIG. 1 is a flowchart illustrating exemplary embodiments of
the present disclosure.
[0025] FIGS. 2A and 2B are photographs in accordance with
embodiments of the present disclosure. Preparation of a subdermal
side of a hamster dorsal skin flap window is shown. Blood vessels
are located approximately 80-100 .mu.m from the near-surface. FIG.
2A shows native skin. FIG. 2B shows the same window preparation,
twenty minutes following treatment with glycerol.
[0026] FIG. 3 is a photograph in accordance with embodiments of the
present disclosure. The locations of subdermal blood vessel
irradiations in one dorsal skin flap window-preparation are
shown.
[0027] FIG. 4 is a graph showing results in accordance with
embodiments of the present disclosure. This figure shows RE50
(radiant exposures which have been found through statistical
analysis of the experimental data to result in a 50% probability of
permanent vessel coagulation) values for permanent blood vessel
coagulation using a 532 nm laser (10 ms pulse duration, 3 mm spot
size) applied to the subdermal side of skin. Two experimental
conditions are represented in this plot. Subdermal irradiations on
native skin are summarized in the "native venules" and "native
arterioles" data points. Subdermal irradiations conducted on skin
in which anhydrous was applied to the subdermal side are shown by
the "glycerol venules" and "glycerol arterioles" points.
[0028] FIG. 5 is a schematic diagram of equipment suitable for
carrying out embodiments of the present disclosure.
[0029] FIGS. 6A and 6B are photographs in accordance with
embodiments of the present disclosure. Shown are amplitude (FIG.
6A) and Doppler (FIG. 6B) images of skin in the hamster dorsal skin
flap window-preparation. The skin shown is a control sample prior
to irradiation. The surface at the top is the subdermal connective
tissue.
[0030] FIGS. 7A and 7B are photographs in accordance with
embodiments of the present disclosure. Shown is the subdermal side
of the control sample twenty-four hours after irradiations (applied
to the epidermal surface) up to 16 J/cm.sup.2. FIG. 7A is an
amplitude image, and FIG. 7B is a Doppler image. Flow in both the
arteriole and venule remains.
[0031] FIGS. 8A and 8B are photographs in accordance with
embodiments of the present disclosure. Shown are amplitude (FIG.
8A) and Doppler (FIG. 8B) images of a native skin sample imaged
from the subdermal side. An arteriole and venule are identified in
the Doppler image.
[0032] FIGS. 9A and 9B are photographs in accordance with
embodiments of the present disclosure. Shown are amplitude (FIG.
9A) and Doppler (FIG. 9B) images of a skin sample treated with
glycerol for twenty minutes and imaged from the subdermal side. The
arteriole and venule are identified in the amplitude image;
however, no flow remains as can be seen from the lack of Doppler
shifts in the Doppler image.
[0033] FIGS. 10A and 10B are photographs in accordance with
embodiments of the present disclosure. Shown are amplitude (FIG.
10A) and Doppler (FIG. 10B) images showing hamster skin twenty-four
hours after irradiation with 1.6 J/cm.sup.2 following treatment
with glycerol. Permanent coagulation has been achieved in both
blood vessels.
DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0034] U.S. Pat. No. 6,275,726 ("the '726 patent") entitled,
"Methods of enhanced light transmission through turbid biological
media" by Chan et al. is hereby incorporated by reference in its
entirety.
[0035] The '726 patent involves a process to increase light
transmission in biological tissue. The technique involves
temporarily replacing tissue water with a fluid that has a
refractive index closer to that of inter/intra cellular components.
Subsequently, the amount of index mis-match between those
components and the fluid environment is temporarily decreased.
This, in turn, lowers the amount of random reflection and
refraction which also reduces light scattering.
[0036] Although useful for the methodology it describes and claims,
the '726 patent does not address problems associated with
conventional laser techniques' inability to adequately control
blood flow velocity. This inability, in turn, hinders the effective
clinical laser treatment of cutaneous vascular lesions. Further,
the '726 patent does not recognize that certain chemical agents may
significantly affect blood flow velocity in a manner that can be
exploited to greatly improve the treatment of cutaneous vascular
lesions. In sum, the '726 patent does not recognize or describe the
particular applications described and claimed herein that create a
new clinical laser treatment protocol for cutaneous vascular
lesions. This protocol not only reduces light attenuation but also
controls blood flow velocity to effectively remove lesions using
lasers exhibiting lower radiant light exposures.
[0037] The present disclosure describes methods for the laser
treatment of cutaneous vascular lesions and other maladies. The
techniques described herein are advantageous at least because they
address shortcomings exhibited in the prior art--(a) light
attenuation and (b) lack of control of blood flow velocity.
Applications for these techniques are vast and include any
situation in which a decreased blood flow velocity and/or reduced
light attenuation is desired. In particular, the laser treatment of
blood vessel lesions, including hyper-vascular lesions, benefits
greatly. Examples of this type of treatment are port wine stains
and leg telangiectasia.
[0038] One aspect of embodiments of this disclosure involves the
use of chemical agents to alter the optical properties of tissue in
order to enhance the delivery of light to physiological targets in
the skin (i.e., "optical clearing"). This aspect is based, at least
in part, upon the findings of U.S. Pat. No. 6,275,726, which has
been incorporated by reference and discusses how appropriate
chemical agents may be used to optically alter biological tissue in
a direction that increases the penetration-depth of light.
[0039] Another aspect of embodiments of this disclosure involves
the use of chemical agents to alter the blood flow velocity of
tissue. The chemical agents allow one to control the blood flow
velocity; in particular, it has recently been discovered by the
inventors that the application of appropriate agents may
significantly reduce, or even halt, blood flow velocity in a
reversible manner.
[0040] In combination, these two aspects, which would have seemed
to be disparate and unrelated phenomena prior to this disclosure,
provide the basis for drastically improved laser treatment
techniques. Specifically, these two aspects in combination provide
for an effective clinical laser treatment protocol for the removal
of cutaneous vascular lesions.
[0041] In one embodiment, hyperosmotic chemical agents are used to
significantly reduce the laser doses required to irreversibly
destroy blood vessels of a vascular lesion. The method uses
chemical agents that temporarily reduce scattering in biological
tissue and reduce the velocity of blood in vessels. Based on the
experimental results listed in the "Examples" section of this
disclosure, a significant improvement in clinical treatment of
hyper-vascular lesions is provided. In particular, the results
reveal a significant reduction in the laser radiant exposures
required to permanently destroy a blood vessel, both under direct
irradiation conditions and when the laser beam is delivered to the
skin epidermal surface and must travel through the dermis to reach
blood vessels.
[0042] Different embodiments involve the application of different
hyperosmotic chemical agents prior to laser irradiation of a
vascular lesion. In one embodiment, a suitable hyperosmotic
chemical agent is glycerol. In other embodiments, suitable
hyperosmotic chemical agents may include, but are not limited to:
dimethyl sulfoxide, sucrose, glucose (dextrose), propylene glycol,
polyethylene glycol, hypaque sodium (diatrizoate sodium), or
mannitol. Any of these agents may be used alone, or in combination
with another one or more of the agents.
[0043] Suitable doses and concentrations of hyperosmotic chemical
agents may be found by reference to U.S. Pat. No. 6,275,726. In
different embodiments, agents may be diluted and still achieve the
same or similar results discussed herein; in particular, in
different embodiments, one may dilute glycerol (down to 25%) or
glucose (down to 10%).
[0044] Suitable techniques to deliver the hyperosmotic chemical
agents may be found by reference to U.S. Pat. No. 6,275,726,
although it will be understood that any other suitable delivery
technique may be exploited including, but not limited to, a variety
of transdermal techniques. One suitable technique for delivery is
injection. In different embodiments, the injection may be
accomplished by a fine hypodermic needle or a high velocity jet.
Another suitable technique involves use of a transdermal drug
delivery device. Such suitable techniques include, but are not
limited to: (1) tape stripping the surface of skin to remove a
small area of epidermis (a technique in common use), (2) use of
ablative methods--such as laser ablation techniques--to create
micro-holes in the skin down to the dermis or subdermis, (3)
chemical peels, (4) mechanical debridement, (5) ultrasound-enhanced
techniques, (6) electroporation, or (7) iontophoresis to aid
transdermal diffusion of chemical agents.
[0045] After the desired optical and morphological changes are
induced on the tissue through the delivery and application (e.g.,
transdermal delivery or injection) of one or more hyperosmotic
chemical agents, laser radiation may be applied to the lesion. The
chemical agents both reduce scattering in the biological tissue,
and also lead to the reduction and/or cessation of flow in
arterioles and venules. The changes allow laser energy to be more
directly applied to the vessels and, concurrently, reduce the
required energy to destroy a given vessel.
[0046] Accordingly, the techniques of this disclosure solve the
once-difficult balancing problem of being able to deliver
sufficient laser energy to a targeted blood vessel to destroy the
vessel without damage to the epidermis and dermis by making it
possible to use lower power lasers (and/or lower laser doses) to
cause irreversible photocoagulation. The techniques reduce or even
eliminate the necessity of multiple treatments to coagulate
vessels. Advantageously, the observed optical, morphological, and
physiological effects due to application of the chemical agents to
skin are reversible with simple hydration of the tissue.
[0047] Turning to FIG. 1, there is shown a flowchart illustrating
general, exemplary embodiments of the present disclosure. In step
20, a patient is identified. In one embodiment, the patient may be
in need of vascular lesion treatment. In other embodiments, the
patient may be in need of other treatments that would benefit from
a reduction in light reflection/refraction and/or decreased blood
flow velocity. In one embodiment, the patient may be human, while
in other embodiments, the patient may be any other type of living
organism.
[0048] In step 30, one or more hyperosmotic agents are administered
to the patient. In the case of vascular lesions, an agent is
administered to a region adjacent the lesion--at the lesion itself
or near the region. In one embodiment, the agent may be
administered at the site of one or more blood vessels to be
permanently photocoagulated, or destroyed, by laser treatment. The
administration of the agent may be done as is known in the art. In
one embodiment, injection by a hypodermic needle or a high velocity
jet may be used. In other embodiments, tape stripping, ablation,
chemical peel, electroporation, iontophoresis, mechanical
debridement, or other transdermal delivery method may be used. The
hyperosmotic agent may include any of the agents discussed herein,
including those discussed in U.S. Pat. No. 6,275,726.
[0049] In step 40, blood flow velocity is reduced by way of the
administration of the hyperosmotic agent. In one embodiment, this
reduction in blood flow velocity may be at least 15%. In
particular, the reduction in blood flow velocity may be about 15%,
16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%,
29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%,
42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%,
55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%,
68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%,
81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%,
94%, 95%, 96%, 97%, 98%, 99%, or 100%. To measure the reduction in
blood flow velocity, one may measure the blood flow velocity before
and after application of a hyperosmotic agent.
[0050] In step 50, light reflection and refraction are reduced
among cellular components at or about a region to be treated to
enhance light transmission. This "optical clearing" comes about by
way of the administration of the hyperosmotic agent, as discussed
in U.S. Pat. No. 6,275,726.
[0051] In step 60, the area to be treated is exposed to radiation,
such as laser radiation. The amount of radiation applied to the
area may vary greatly depending upon the application. In
embodiments involving the treatment of cutaneous vascular lesions,
the administration of one or more hyperosmotic agents in step 30
advantageously lowers the amount of radiation required to treat the
lesions (i.e., to permanent photocoagulate, or destroy, blood
vessels associated with the lesions). In fact, the reduction in
laser radiation may be at least 15%. In particular, the reduction
in radiation amount may be about 15%, 16%, 17%, 18%, 19%, 20%, 21%,
22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%,
35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%,
48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%,
61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%,
74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%,
87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, or 95%. To measure the
reduction in blood flow velocity, one may measure the energy per
area required to treat a lesion with and without the administration
of a hyperosmotic agent. In one embodiment involving the treatment
of lesions, a suitable range of radiation may be between about 0.1
and about 20 J/cm.sup.2. In one embodiment, the source of laser
radiation may be light sources, including lasers, in the wavelength
range of about 450-1100 nm. Typical sources include, but are not
limited to cw (continuous wave) and pulsed diode lasers, dye
lasers, solid state lasers, and gas lasers. In one embodiment
delivery may be through optical fibers. In other embodiments, any
other suitable source of radiation may be used.
[0052] In step 70, a hydrating agent is administered to the area
being treated. The purpose of the hydrating agent is to flush the
hyperosmotic agent from the area and to return the area being
treated as close as possible back to its normal, pre-treatment
state, excluding the status of blood vessels. The administration of
the hydrating agent may be accomplished by any of the means used to
administer the hyperosmotic agent(s), including injection. In one
embodiment, the hydrating agent may include saline. Other hydrating
agents and techniques are discussed in U.S. Pat. No. 6,275,726.
[0053] FIG. 5 shows one suitable apparatus for visualizing the
effects of the techniques described herein, such as those
illustrated in FIG. 1. FIG. 5 shows an optical setup of a color
Doppler optical coherence tomography system (CDOCT). CDOCT is a
light imaging device that acquires cross-sectional, in-depth images
of biological tissue [Izatt et al.,]. Besides providing images of
tissue structure, CDOCT reveals blood vessels by detecting Doppler
shifts due to moving blood. After imaging, samples may be
irradiated in place using equipment such as a frequency-doubled
Nd:YAG laser (Versapulse V, Coherent). Technical specifications of
the device are described: A superluminescent diode (SLD) centered
at 1290 nm is used as the light source. The light from the SLD is
split into a reference arm (incident on a reference mirror) and a
sample arm (incident on the sample). The probing beam is incident
on the dorsal window, which may be tilted at 20.mu. with respect to
the vertical to obtain Doppler information. The light from the
sample and the reference mirror recombine and form an interference
signal. The envelope of the interference signal may be filtered
with a bandpass filter (BPF). The signal is coherently demodulated
in a lock-in amplifier. The backscattered magnitude (I) and the
phase information (O) undergo digital signal processing in a
computer. Labview software [Izatt, Case Western University] may be
used to process and display amplitude (magnitude) and Doppler
(velocity) images.
[0054] With the benefit of the present disclosure, those having
skill in the art will comprehend that techniques claimed herein and
described above may be modified and applied to a number of
additional, different applications, achieving the same or a similar
result. The claims attached hereto cover all such modifications
that fall within the scope and spirit of this disclosure.
[0055] The following examples are included to demonstrate specific
embodiments of this disclosure. It should be appreciated by those
of skill in the art that the techniques disclosed in the examples
that follow represent techniques discovered by the inventors to
function well in the practice of the invention, and thus can be
considered to constitute specific modes for its practice. However,
those of skill in the art should, in light of the present
disclosure, appreciate that many changes can be made in the
specific embodiments which are disclosed and still obtain a like or
similar result without departing from the spirit and scope of the
invention.
EXAMPLES
[0056] In these examples, the inventors use chemical agents for
reducing the applied laser radiant exposure required to permanently
destroy blood vessels. The technique has been demonstrated both in
direct blood vessel irradiations, and also on blood vessels located
hundreds of microns beneath the epidermal surface of in vivo skin.
Evidence is presented that demonstrates the treatment of skin with
agents such as glycerol prior to laser radiation leads to a
significant decrease in the delivered radiant exposures required to
permanently destroy a blood vessel, compared to control cases where
treatment with agents such as glycerol did not occur.
Materials and Methods
[0057] Animal Model
[0058] Hamsters were anesthetized with a 4:3 mixture of Ketamine
(20 mg/ml): Rompun (100 mg/ml) and 0.15 ml/100 g body weight of the
solution was delivered IP. The rodent dorsal skin flap window
preparation first developed by Papenfuss et al. was used as an in
vivo animal model to demonstrate the effect of glycerol on
photocoagulation of blood vessels. This in vivo model allows the
simultaneous observation of the epidermal and subdermal sides of
the skin while maintaining hydration and function [Papenfuss et
al., 1979]. The preparation has been used as an in vivo model for
optical imaging blood vessels on the subdermal side of skin while
maintaining access to the epidermis [Barton et al., 1998, Vargas et
al., 2001].
[0059] The preparation includes shaving and epilating the entire
dorsal area of a hamster. The skin is pulled away from the body
along the dorsal midline and sutured to a vertical c-clamp. A
circular region 1 cm in diameter is cut from one single thickness
of skin, exposing the subdermal side of the opposing thickness of
skin. An aluminum chamber is sutured to both sides of the skin, and
glass is placed over the cutout section to prevent the tissue from
dehydrating on the subdermal side. During the experiments, this
glass is removed for improved imaging, and hydration is maintained
with application of physiological saline.
[0060] Blood vessels in the skin of the dorsal window preparation
are located in the subdermal fat and connective tissue layers
approximately 400-700 .mu.m beneath the epidermal surface and about
80-100 .mu.m from the exposed subdermal surface of a 100 g hamster.
Arterioles and venules in the dorsal window preparation range in
diameter between about 50-500 .mu.m in inner diameter, with the
main arteriole and venule about 350-500 .mu.m in diameter.
[0061] In Vivo Application of Glycerol
[0062] Anhydrous glycerol was applied to the subdermal side of the
dorsal skin flap window preparation. The subdermal side of the
window preparation contains a well approximately 2 mm deep and 1 cm
in diameter placed directly over the exposed subdermal skin. A
small opening at the bottom allows the flow of glycerol out of the
well. This well was filled with glycerol and continually refilled
for a total time of twenty minutes. Any remaining glycerol was
removed from the well at the end of twenty minutes. An example
window preparation shown from the subdermal side before and after
the application of glycerol is shown in FIG. 2.
[0063] Subdermal Irradiations
[0064] Subdermal irradiations allowed for the direct irradiation of
blood vessels in the rodent dorsal skin flap window preparation.
Direct irradiations of blood vessels following treatment with
glycerol were performed to demonstrate the benefits of a decrease
in blood flow velocity due to chemical agents. A total of 46
venules and 38 arterioles were irradiated directly in six window
preparations following application of glycerol with radiant
exposures ranging from 0.3 J/cm.sup.2 to 7.5 J/cm.sup.2. Three to
six irradiations were performed on each window preparation
depending on the anatomical structure of the microvasculature. For
instance, in the window preparation of FIG. 3, six areas were
irradiated (shown by the circles) to target individual
arteriole-venule pairs.
[0065] Venules ranged in diameter from 50 to 200 micrometers.
Arteriole diameters ranged from 20 to 140 micrometers. Each
arteriole-venule pair was irradiated a single time with a single
pulse from a Versapulse V Vascular (Coherent, Santa Clara, Calif.)
laser at 532 nm with a pulse duration of 10 ms and spot size of 3
mm. The window preparation was viewed and recorded through a
surgical microscope (Wild Leitz M650, Germany) prior to, during,
and following irradiation. The window preparation was observed
twenty-four hours after laser irradiation to assess whether
permanent coagulation occurred for each vessel irradiated.
[0066] Since previous studies have revealed that the fluences
required to permanently destroy a blood vessel depends on size and
type (arteriole vs. venule) [Kimel et al., 1994; Barton, 1998],
data analysis for venules and arterioles was done separately, and
for each type, vessels were categorized according to inner
diameter. Venules were categorized in four groups (50-80 .mu.m,
80-110 .mu.m, 110-140 .mu.m, and 140-200 .mu.m diameter) and
arterioles into three groups (20-50 .mu.m, 50-80 .mu.m, and 80-110
.mu.m).
[0067] Yes/no (0/1) grading of vessel destruction by
photocoagulation after twenty-four hours was used to perform probit
analysis on the data assuming a sigmoid probability distribution,
resulting in 50% probability for threshold radiant exposures (RE50)
for vessels of a given size category and type [Cain et al.,
1996].
[0068] Epidermal Irradiations
[0069] While the subdermal irradiations were done to show that the
resulting decrease in blood flow velocity by glycerol allows for a
substantial decrease in laser doses to destroy vessels, epidermal
irradiations were performed to demonstrate how the technique could
be carried out clinically. In this set of experiments, three dorsal
skin flap window preparations were treated with glycerol on the
subdermal side of the skin. Then, the main arteriole-venule pair
(such as the one labeled A and V in FIG. 3) was irradiated from the
epidermal side to determine the approximate range of radiant
exposures required to permanently destroy blood vessels in skin
treated with glycerol. Since no published data exists for direct
comparison with controls, two native hamster dorsal skin flap
window preparations were irradiated from the epidermal side as
well.
[0070] The skin surrounding the main arteriole-venule pair in each
window preparation was first imaged using Color Doppler optical
coherence tomography (CDOCT) (see FIG. 5). The skin was imaged from
the subdermal side since these blood vessels are located
approximately 100 .mu.m from the subdermal surface, allowing for
accurate determination of vessel flow and size characteristics. In
the case of control samples (2), the vessels were irradiated from
the epidermal side immediately after imaging the native skin. This
was achieved by applying a single pulse from a 532 nm, 3 mm spot
size, 10 ms pulse duration laser (Versapulse V, Coherent) to the
skin without altering its position relative to the CDOCT sample
probe. The experimental setup is illustrated in FIG. 5.
[0071] The skin was imaged again to assess changes to blood flow.
In the first control sample, if no changes were observed to occur,
the skin was radiated with a higher radiant exposure one hour
later. If any changes in flow or vessel size were observed, the
skin was not irradiated again and was imaged after 24 hours. In
all, 5 pulses were delivered ranging in radiant exposure from 4.13
J/cm.sup.2 to 16 J/cm.sup.2, the maximum allowable for the laser
parameters used. In the second control sample, only a single pulse
was delivered with a radiant exposure of 12 J/cm.sup.2.
[0072] In the other three samples, glycerol was applied to the
subdermal side of the window preparation for twenty minutes after
imaging the native skin with CDOCT. The optically cleared skin was
then imaged again using CDOCT. Laser pulses were applied in the
same manner described above and the skin was re-imaged after
twenty-four hours to assess if permanent vessel closure
occurred.
Results
[0073] Subdermal Irradiations
[0074] The resulting RE50 values for permanent vessel destruction
are summarized in FIG. 4 for arterioles and venules in skin treated
with glycerol prior to irradiations. Results are compared to values
from previously published results on subdermal irradiations
performed on dorsal windows not treated with glycerol [Barton et
al., 1998] in FIG. 4. Due to the small number of irradiations
compared to the number of parameters (vessel size and type), there
was insufficient data to estimate the ED50 values for arterioles
and venules 80-110 .mu.m in diameter.
[0075] Epidermal Irradiations
[0076] The CDOCT amplitude and Doppler images from the first
control sample prior to irradiations are shown in FIG. 6. The
amplitude image represents backscattered light from the tissue--a
cross-section of the skin is shown. The Doppler image represents
frequency-shifted light from scatterers in the skin. While one
cannot identify blood vessels in the amplitude image, an arteriole
and venule are identified in the Doppler image. The arteriole (A)
diameter is 225 .mu.m, and the venule (V) diameter is 470 .mu.m.
They are located approximately 80 .mu.m from the subdermal surface
(the first interface in the top of the amplitude scan) and 750
.mu.m from the epidermal surface (not shown here). Although this
sample was repeatedly irradiated with radiant exposures starting at
4.13 J/cm.sup.2 and ending with 16 J/cm.sup.2, twenty-four hours
later flow remains in both vessels (FIG. 7).
[0077] In the second control sample a single pulse (12 J/cm.sup.2)
was unsuccessful in leading to permanent flow cessation of either
an arteriole (290 .mu.m) or venule (460 .mu.m), which were located
500 .mu.m below the epidermal surface of the skin (100 .mu.m from
the subdermal surface).
[0078] In the three window preparations where glycerol was applied
prior to irradiation from the epidermal side, blood vessels on the
subdermal side of the skin were successfully destroyed with radiant
exposures as low as 1.6 J/cm.sup.2. One such example follows. The
native skin of one rodent window preparation is shown in FIG. 8.
The arteriole diameter is 250 .mu.m, while the venule has a
diameter of 300 .mu.m. They are located 450 .mu.m from the
epidermal surface.
[0079] The same skin is again shown after treatment with glycerol
for twenty minutes (FIG. 9). The Doppler image of FIG. 9 shows that
flow does not remain in either the arteriole or venule. This result
is typical as has been observed in a previous study [Vargas, 2001].
That study showed that flow cessation after the treatment with
glycerol alone is not permanent (upon hydration the skin and blood
vessels return to their native state). A single pulse (1.6
J/cm.sup.2) was applied from the subdermal side of the skin in FIG.
9. Twenty-four hours later, flow has not returned to either vessel
(FIG. 10), despite hydration of the skin.
[0080] In another preparation, successful permanent coagulation
using glycerol was achieved using a radiant exposure of 4.13
J/cm.sup.2. In this case the vessels (200 .mu.m arteriole and 410
.mu.m venule) were located 680 .mu.m below the epidermal surface in
the native skin and almost 400 .mu.m in the skin treated with
glycerol. Finally, in the third case 4.95 J/cm.sup.2 applied to
skin with a 300 .mu.m arteriole and 390 .mu.m venule, only the
venule was successfully coagulated. In this case, the vessels were
located 615 .mu.m from the epidermal surface of the native skin and
300 .mu.m in the glycerol-treated case.
Discussion
[0081] Subdermal Irradiations
[0082] Because in subdermal irradiations, blood vessels of the skin
were irradiated directly with no overlying tissue layers present,
the data of FIG. 4 indicates that the morphological effects of
glycerol on cutaneous blood vessels (specifically, the decrease in
blood flow velocity) considerably aids in their permanent
destruction by laser radiation. Comparison with previously
published results [Barton et al., 1998] indicate that glycerol
reduces radiant exposures required for permanent vessel destruction
by a factor of 10 for arterioles and a factor of 5-8 for venules.
The results of this experiment lead us to conclude that radiant
exposures required to directly destroy vessels of a given type and
size were drastically reduced by using glycerol to reduce or cause
the cessation of blood flow in subdermal blood vessels.
[0083] Epidermal Irradiations
[0084] These results appear to indicate that the techniques
discussed herein allow use of lower laser fluences when treating
cutaneous blood vessel lesions. The studies of the inventors
indicate that the decrease in laser fluences and increase in depth
penetration of light afforded by these techniques may have a
significant, lasting impact on the clinical laser treatment of
cutaneous vascular lesions.
CONCLUSION
[0085] The presented data offers experimental support of using
glycerol and other "optical clearing" agents that control flow
velocity to enhance the laser treatment of cutaneous vascular
lesions. This method may significantly impact clinical laser
procedures not only for the treatment of cutaneous vascular
lesions, but also for any malady whose treatment would benefit from
increased light penetration and the reduction in blood flow
velocity.
[0086] With the benefit of the present disclosure, those having
skill in the art will comprehend that techniques claimed herein may
be modified and applied to a number of additional, different
applications, achieving the same or a similar result. For example,
techniques of this disclosure may be applied to, for example, the
treatment of blood vessels endoscopically--as in a stomach ulcer,
etc. In such an application, topical application may be achieved
without modifying the tissue. The claims attached hereto cover all
such modifications that fall within the scope and spirit of this
disclosure.
REFERENCES
[0087] Each of the following references is hereby incorporated by
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Cutaneous Blood Vessels, Doctoral Dissertation, The University of
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of small vessels by laser irradiation," Lasers in Surgery,
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[0102] Vargas G., Reduction of Light Scattering in Biological
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