U.S. patent application number 11/623383 was filed with the patent office on 2008-07-17 for method and apparatus for selective photothermolysis of veins.
This patent application is currently assigned to The General Hospital Corporation. Invention is credited to Richard Rox Anderson, William A. Farinelli, Iris Rubin.
Application Number | 20080172111 11/623383 |
Document ID | / |
Family ID | 39618377 |
Filed Date | 2008-07-17 |
United States Patent
Application |
20080172111 |
Kind Code |
A1 |
Anderson; Richard Rox ; et
al. |
July 17, 2008 |
METHOD AND APPARATUS FOR SELECTIVE PHOTOTHERMOLYSIS OF VEINS
Abstract
A system and method are provided that are capable of selectively
treating a vein using photothermolysis techniques, where an
electromagnetic radiation is applied to tissue containing the vein.
The radiation can be selected so that it may be more effectively
absorbed by veins as compared to arteries. Thus, unwanted thermal
damage to arteries in the vicinity of the vein being treated can be
reduced or avoided. The radiation can have a frequency of
approximately 654 nm, which can provide a ratio of absorption by
veins to absorption by arteries of about 3.7. Other wavelengths
near 654 nm may be provided, for example, which can have an
absorption ratio greater than, e.g., about 3.3 to 3.6.
Inventors: |
Anderson; Richard Rox;
(Boston, MA) ; Rubin; Iris; (Brookline, MA)
; Farinelli; William A.; (Danvers, MA) |
Correspondence
Address: |
DORSEY & WHITNEY LLP;INTELLECTUAL PROPERTY DEPARTMENT
250 PARK AVENUE
NEW YORK
NY
10177
US
|
Assignee: |
The General Hospital
Corporation
Boston
MA
|
Family ID: |
39618377 |
Appl. No.: |
11/623383 |
Filed: |
January 16, 2007 |
Current U.S.
Class: |
607/89 ;
606/9 |
Current CPC
Class: |
A61N 2005/0659 20130101;
A61B 18/20 20130101; A61B 18/203 20130101; A61B 2018/00452
20130101; A61B 2018/00458 20130101 |
Class at
Publication: |
607/89 ;
606/9 |
International
Class: |
A61N 5/067 20060101
A61N005/067 |
Claims
1. A method for treating at least one vein, comprising: directing
an electromagnetic radiation to a tissue containing the at least
one vein, wherein the radiation has at least one characteristic
which effectuates an absorption by the at least one vein more
effectively than by an artery.
2. The method of claim 1, wherein the radiation has a wavelength
between about 632 nm and 680 nm.
3. The method of claim 1, wherein the radiation has a wavelength
between about 638 nm and 668 nm.
4. The method of claim 1, wherein the radiation has a wavelength
between about 644 nm and 662 nm.
5. The method of claim 1, wherein the radiation has a wavelength of
about 654 mm.
6. The method of claim 1, further comprising providing the
radiation by at least one of a pulsed dye laser, a
wavelength-shifted Nd:YAG laser, a frequency-doubled infrared
laser, a high power diode laser array or a fiber laser.
7. The method of claim 1, further comprising providing the
radiation using an intense pulsed light source.
8. The method of claim 1, wherein the at least one vein is a
varicose vein.
9. The method of claim 1, wherein the at least one vein is
associated with a port wine stain.
10. A system for treating at least one vein, comprising: an
arrangement configured to provide an electromagnetic radiation to a
tissue containing the at least one vein; wherein the radiation has
at least one characteristic which effectuates an absorption by the
at least one vein more effectively than by an artery.
11. The system of claim 10, wherein the radiation has a wavelength
between about 632 nm and 680 nm.
12. The system of claim 10, wherein the radiation has a wavelength
between about 638 nm and 668 nm.
13. The system of claim 10, wherein the radiation has a wavelength
between about 644 nm and 662 nm.
14. The system of claim 10, wherein the radiation has a wavelength
of about 654 nm.
15. The system of claim 10, wherein the arrangement is at least one
of a pulsed dye laser, a wavelength shifted Nd:YAG laser, a
frequency-doubled infrared laser, a high power diode laser array or
a fiber laser.
16. The system of claim 10, wherein the arrangement is an intense
pulsed light source.
17. The system of claim 10, further comprising a power source and
control electronics, both coupled to the arrangement.
18. The system of claim 10, further comprising an optical apparatus
configured to receive the radiation and direct the radiation toward
the tissue.
19. The system of claim 10, further comprising an apparatus
configured to cool a surface of the tissue.
Description
FIELD OF INVENTION
[0001] The present invention relates to methods and apparatus for a
selective photocoagulation of veins, for example, a treatment of
port wine stains or varicose veins, while avoiding significant
thermal damage to arteries.
BACKGROUND
[0002] A blood vessel can be any vascular structure, e.g., an
artery, a vein, or a capillary. A dilated or malformed vein can be
associated with one or more of a variety of disease conditions such
as, e.g., port wine stains and varicose veins.
[0003] Port wine stains can include post-capillary venules. Port
wine stains can begin in infancy, and may both thicken and darken
in color with time. In addition to being disfiguring, port wine
stains can have adverse psychosocial effects.
[0004] A conventional treatment for port wine stains may use a
pulsed dye laser at a wavelength of 595 nm. A success rate for
complete clearance of port wine stains may be low when using
conventional treatment modalities such as the 595 nm pulsed dye
laser, which can result from inadequate depth of penetration. Deep
vessels can be targeted using, e.g., a 1064 nm Nd:YAG laser
treatment for port wine stains. However, a wavelength of 1064 nm
can be more strongly absorbed by arterial blood (which may contain
primarily oxygenated hemoglobin ("HbO2")), than by venous blood
(which may contain a mix of deoxygenated hemoglobin ("Hb") and
HbO2)). Thus use of the Nd:YAG laser to treat port wine stains may
create undesirable arterial damage, causing tissue necrosis and
scarring, and can be dangerous to a patient. Although radiation
from a 595 nm pulsed dye laser may be somewhat more absorbed by
deoxygenated hemoglobin (Hb) than by oxygenated hemoglobin (HbO2),
treatment fluence with the pulsed dye laser can still be limited by
potential thermal damage to arteries. It may be desirable to have a
laser that is designed specifically to target deoxygenated
hemoglobin (Hb), and can be significantly more selective for
veins.
[0005] Varicose veins can be dilated, tortuous veins which may
result from defective structure or function of the valves of the
veins, from intrinsic weakness of a vein wall, or from
arteriovenous fistulas. Varicose veins can be categorized as
superficial or deep. Superficial varicose veins may be primary,
originating in the superficial system, or secondary, resulting from
deep venous insufficiency and incompetent perforating veins, or
from deep venous occlusions causing enlargement of superficial
veins that can serve as collateral veins.
[0006] Superficial varicose veins may provide an undesirable
cosmetic appearance. Conventional treatments for superficial
varicose veins can include sclerotherapy or surgical therapy. For
example, sclerotherapy can include injection of a sclerosing
solution such as hypertonic saline or surfactants into blood
vessels of interest, which may result in deformation of the
vascular structure. Surgical therapy can involve extensive ligation
and stripping of greater and lesser saphenous veins. However, an
administration of such therapies can use a high degree of technical
skill. Also, a fear of needles and/or surgical procedures may
prevent many patients from seeking these treatments.
[0007] Lasers and other light sources can be used in
photothermolysis therapy to treat dilated blood vessels, such as
superficial varicose veins. Photothermolysis treatment techniques
are described, e.g., in U.S. Pat. No. 5,558,667. Absorbed light,
which can be provided in a form of pulses, may be used to damage
the vessels while sparing surrounding tissues. For example, an
irradiation of a blood vessel with an electromagnetic radiation can
lead to an absorption of energy by blood components contained
therein and subsequent heating of the vessel. The heated vessel may
thrombose and collapse, which can produce desired therapeutic
effects for treatment of venous malformations. However, nearby
arteries may also be damaged by such photothermolysis techniques,
which can lead to partial or complete closure of the arteries,
necrosis of adjacent tissue, and unwanted scarring.
[0008] A reperfusion of treated blood vessels may reduce the
effectiveness of photothermolysis treatment. Multiple treatments
can be preferred because of the reperfusion of a treated vessel,
which can become more likely if the amount of applied energy is
limited to avoid unwanted damage to nearby arteries. High costs,
number of treatments, and risk of post-treatment pigmentation are
other negative factors which may be associated with
photothermolysis therapy.
[0009] Superficial varicose veins may be treated using
sclerotherapy, which can be effective but is often painful, and can
have side effects including, e.g., hyperpigmentation, matting,
and/or ulceration. Various lasers may be used for treating ectatic
leg veins such as, e.g., a pulsed dye laser operating at a
wavelength of 595 nm, an alexandrite laser at 755 nm, a diode laser
at 800/810 nm, or a NdYag laser at 1064 nm, although the use of
such lasers may not be very effective and/or may produce
undesirable side effects. A phototreatment of veins using lasers or
other sources of electromagnetic radiation such as, e.g., Intense
Pulsed Light ("IPL") sources, may also induce unwanted thermal
damage to nearby arteries.
[0010] Therefore, it may be desirable to provide a laser or IPL
source that can selectively photocoagulate veins for treatment of
various venous malformations, with relative sparing of
arteries.
OBJECTS AND SUMMARY OF THE INVENTION
[0011] Exemplary method and apparatus of the present invention can
provide, e.g., selective photothermolysis of venous lesions using a
laser, IPL source or other source of electromagnetic radiation
which can facilitate a relative sparing of arteries.
[0012] According to exemplary embodiments of the present invention,
a method can be provided for treating a vein, which includes
directing an electromagnetic radiation to biological tissue, such
as skin, containing the vein. Characteristics of the radiation can
be chosen so the radiation may be selectively absorbed by veins as
compared with arteries. For example, the radiation has a wavelength
between about 632 nm and 680 nm, between about 638 nm and 668 nm,
between about 644 nm and 662 nm, or about 654 nm.
[0013] In certain exemplary embodiments of the present invention,
the radiation can be provided by a pulsed dye laser, another type
of laser, or an intense pulsed light source.
[0014] Veins and vascular lesions which can be treated using
exemplary embodiments of the present invention can include but are
not limited to varicose veins and port wine stains. Venous
malformations in organs other than the skin may also be treated
using exemplary embodiments of the present invention.
[0015] According to further exemplary embodiments of the present
invention, a system can be provided which is configured to treat a
vein using photothermolysis techniques. For example,
characteristics of the radiation can be chosen so the radiation is
selectively absorbed by veins as compared with arteries to avoid
unwanted arterial damage. The exemplary system can include, e.g., a
radiation source, a power source, control electronics, and an
optional optical arrangement which can be used to further direct
the radiation toward the tissue being treated. The exemplary system
can also include an arrangement configured to cool the surface of
the tissue being treated.
[0016] These and other objects, features and advantages of the
present invention will become apparent upon reading the following
detailed description of embodiments of the invention, when taken in
conjunction with the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Further objects, features and advantages of the invention
will become apparent from the following detailed description taken
in conjunction with the accompanying figures showing illustrative
embodiments of the invention, in which:
[0018] FIG. 1 is an exemplary graph of an absorption of
electromagnetic energy by Hb and HbO2 as a function of wavelength
of the energy, together with an absorption ratio of Hb and
HbO2;
[0019] FIG. 2 is an exemplary graph of an absorption ratio of Hb
and HbO2, and an absorption ratio of venous and arterial blood, as
a function of wavelength of electromagnetic radiation; and
[0020] FIG. 3 is a schematic diagram of an exemplary system which
may be used in accordance with exemplary embodiments of the present
invention.
[0021] While the present invention will now be described in detail
with reference to the figures, it is done so in connection with the
illustrative embodiments.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF INVENTION
[0022] Perfusion (blood flow) can maintain a blood vessel such as,
e.g., a vein or an artery, in a healthy condition. Perfusion of
blood can be an important function of blood vessels. Conversely,
when a vessel is closed off and perfusion stops, the vessel may
eventually thrombose, die, and degrade. It may be desirable to
reduce or eliminate perfusion in certain blood vessels, e.g., in
venous malformations, for therapeutic and/or cosmetic purposes.
Non-invasive methods using photothermolysis can be provided to make
selective use of this natural process.
[0023] For example, a vascular structure may be irradiated with
electromagnetic radiation using a photothermolysis procedure. Blood
vessels contain red blood cells which are rich in hemoglobin.
Hemoglobin can provide a chromophore that may be absent in the
surrounding tissues, e.g., the dermis, and which may preferentially
absorb radiation. Therefore, hemoglobin can be a suitable target
for selective absorption of heat energy within blood vessels. For
example, deoxygenated hemoglobin (deoxyhemoglobin, or Hb) and/or
oxygenated hemoglobin (oxyhemoglobin, or HbO2) can preferentially
absorb radiation, which can lead to local heating of the structure.
Such a heating may thermally damage the blood vessel, and lead to a
reduction or elimination of perfusion therein.
[0024] It may be preferable to use photothermolysis techniques to
damage veins such as, e.g., varicose veins, or post-capillary
venules which may be present in port wine stains. However,
conventional photothermolysis techniques may also produce unwanted
thermal damage to nearby arteries, which can lead to undesirable
effects such as, e.g., local necrosis and scarring.
[0025] According to exemplary embodiments of the present invention,
a system and method can be provided for photothermolysis of venous
structures which can avoid inducing a significant thermal damage in
arteries. Arterial blood can contain predominantly oxygenated
hemoglobin, whereas venous blood can include a mix of oxygenated
and deoxygenated hemoglobin. Photothermolysis using an
electromagnetic radiation that is more strongly absorbed by Hb than
by HbO2 can be used to induce significant thermal damage in
particular veins while avoiding or inducing lesser thermal damage
in nearby arteries.
[0026] FIG. 1 is an exemplary graph 100 of absorption of
deoxyhemoglobin 110 and of oxyhemoglobin 120 as a function of
electromagnetic energy wavelength. Also shown in FIG. 1 is a graph
of a ratio 130 of the absorption of the electromagnetic energy by
deoxyhemoglobin 110 to the absorption by oxyhemoglobin 120. This
graph indicates that the Hb/HbO2 absorption ratio is larger for
electromagnetic radiation having wavelengths between about 600 nm
and 700 nm.
[0027] Table 1 provides numerical values of absorption by Hb
("UHb") and by HbO2 (UhbO2") of electromagnetic radiation having
wavelengths between 620 nm and 680 mm. Table 1 shows a maximum
UHb/UHbO2 absorption ratio of about 10.23 at a wavelength of 654
nm. This absorption ratio can be greater than 10 for wavelengths
between about 644 nm and 662 nm. Further, the UHb/UHbO2 absorption
ratio may be greater than about 9 for wavelengths between about 634
nm and 676 nm.
[0028] Veins can typically contain approximately 30%
deoxyhemoglobin (Hb) and 70% oxyhemoglobin (HbO2); precise
composition values may depend on a particular organ associated with
the vein and metabolic need for oxygen extraction. Arteries can
contain primarily oxyhemoglobin (HbO2). A relative absorption of
the electromagnetic radiation by a vein ("Uvein") to an absorption
by an artery ("Uartery") can be estimated mathematically based on
these compositions of venous and arterial blood. This ratio can be
used as a measure of venous selectivity of energy absorption for a
particular wavelength of radiation.
[0029] The absorption ratio of Uvein/Uartery (absorption by
veins/absorption by arteries) can be expressed using the absorption
by Hb and HbO2 (UHb and UHbO2, respectively). The absorption of the
radiation by a vein, Uvein, can be approximated by the following
exemplary equation:
Uvein=UHbO2*Sa(v)+UHb*(1-Sa(v)), (1)
TABLE-US-00001 TABLE 1 Absorption of electromagnetic radiation by
deoxygenated hemoglobin, Hb, and oxygenated hemoglobin, HbO2.
Wavelength UHb UHbO2 (nm) (cm-1/M) (cm-1/M) UHb/UHbO2 620 942
6509.6 6.910403397 622 858 6193.2 7.218181818 624 774 5906.8
7.631524548 626 707.6 5620 7.942340305 628 658.8 5366.8 8.146326655
630 610 5148.8 8.440655738 632 561.2 4930.8 8.786172488 634 512.4
4730.8 9.232630757 636 478.8 4602.4 9.612364244 638 460.4 4473.6
9.716768028 640 442 4345.2 9.830769231 642 423.6 4216.8 9.954674221
644 405.2 4088.4 10.08983218 646 390.4 3965.08 10.15645492 648
379.2 3857.6 10.17299578 650 368 3750.12 10.19054348 652 356.8
3642.64 10.20919283 654 345.6 3535.16 10.22905093 656 335.2 3427.68
10.22577566 658 325.6 3320.2 10.19717445 660 319.6 3226.56
10.09561952 662 314 3140.28 10.00089172 664 308.4 3053.96
9.902594034 666 302.8 2967.68 9.800792602 668 298 2881.4
9.669127517 670 294 2795.12 9.507210884 672 290 2708.84 9.340827586
674 285.6 2627.64 9.200420168 676 282 2554.4 9.058156028 678 279.2
2481.16 8.886676218 680 277.6 2407.92 8.674063401
where Sa(v) can represent the fractional saturation of oxygen in
venous blood. In a similar manner, absorption of radiation by n
artery, Uartery, can be approximated by the equation:
Uartery=UHbO2*Sa(a)+UHb*(1-Sa(a)), (2)
where Sa(a) can represent the fractional saturation of oxygen in
arterial blood.
[0030] As described above, Sa(v) can be approximately 0.7 (e.g., a
vein may contain approximately 70% oxygenated blood), and Sa(a) can
be approximately 1.0 (e.g., blood in an artery can be fully
oxygenated). Using these values, the expressions for Uvein and
Uartery in Eqs. (1) and (2) can be provided as:
Uvein=0.7UHbO2+0.3UHb, (3)
and
Uartery=UHbO2. (4)
The ratio of absorption of radiation by a vein to absorption by an
artery, Uvein/Uartery, can then be expressed as:
Uvein/Uartery=(0.7UHbO2+0.3UHb)/UHbO2. (5)
The absorption ratio Uvein/Uartery can account for the relative
composition of deoxyhemoglobin (Hb) and oxyhemoglobin (HbO2) in
veins and arteries, and may represent a measure of venous
selectivity.
[0031] FIG. 2 is an exemplary graph 200 showing a ratio 210 of
deoxyhemoglobin absorption, UHb, to oxyhemoglobin absorption UHbO2,
over a range of wavelengths of electromagnetic radiation. Also
shown in FIG. 2 is a selectivity ratio 220, Uvein/Uartery, as a
function of radiation wavelength. The absorption selectivity of
veins as compared to arteries can reach a maximum value at a
wavelength near 650 nm, and may decrease with an increasing or
decreasing of the wavelength.
[0032] Values of Uvein and Uartery, together with a selectivity
ratio Uvein/Uartery, are provided in Table 2 for the radiation
wavelengths between 620 nm and 680 nM. This data can indicate that
the selectivity ratio Uvein/Uartery may have a maximum value of
about 3.77 at a wavelength of about 654 nm. This ratio may remain
above 3.7 for wavelengths between about 644 nm and 662 nm, and may
be greater than 3.6 for wavelengths between about 638 nm and 668
nm. The selectivity ratio can be greater than 3.3 for wavelengths
between about 632 nm and 680 nm.
[0033] Based on the absorption data provided herein, the exemplary
method and system can be provided in accordance with exemplary
embodiments of the present invention for non-invasively inducing
selective necrosis of unwanted veins, while inducing relatively
little or no damage to nearby arteries.
TABLE-US-00002 TABLE 2 Absorption of electromagnetic radiation by a
vein, Uvein, and an artery, Uartery, together with the selectivity
ratio Uvein/Uartery. Wavelength Uvein Uartery Uvein/ (nm) (cm-1/M)
(cm-1/M) Uartery 620 2612 942 2.77 622 2459 858 2.87 624 2314 774
2.99 626 2181 708 3.08 628 2071 659 3.14 630 1972 610 3.23 632 1872
561 3.34 634 1778 512 3.47 636 1716 479 3.58 638 1664 460 3.62 640
1613 442 3.65 642 1562 424 3.69 644 1510 405 3.73 646 1463 390 3.75
648 1423 379 3.75 650 1383 368 3.76 652 1343 357 3.76 654 1302 346
3.77 656 1263 335 3.77 658 1224 326 3.76 660 1192 320 3.73 662 1162
314 3.70 664 1132 308 3.67 666 1102 303 3.64 668 1073 298 3.60 670
1044 294 3.55 672 1016 290 3.50 674 988 286 3.46 676 964 282 3.42
678 940 279 3.37 680 917 278 3.30
[0034] For example, a conventional photothermolysis treatment for
port wine stains or other vascular lesions can use a pulsed dye
laser having a wavelength of about 595 nm. Use of a longer
wavelength of about 654 nm, as described herein, can provide
increased selectivity of absorption by veins as compared with
arteries, and may also allow for a deeper penetration into the
treated tissue, which can improve treatment efficacy.
[0035] An exemplary system 300 which may be used in accordance with
exemplary embodiments of the present invention is shown in FIG. 3.
This exemplary system 300 can include a source of electromagnetic
radiation 310, a power source 320, a control electronics
arrangement 330 and, optionally, a delivery optics arrangement 340.
One or more of these components 310-340 may be provided in a single
enclosure or a handpiece. Alternatively, one or more of these
components 310-340 may be provided in a separate housing from other
components.
[0036] The power source 320 may be used to provide power to the
radiation source 310. The control electronics arrangement 330 can
be in electrical or wireless communication with both the power
source 320 and the radiation source 310, and can be used to control
or affect certain properties of the electromagnetic radiation
generated by the radiation source 310. The radiation source 310 can
be configured, optionally together with the delivery optics
arrangement 340, to direct radiation towards a region of a
biological tissue 350 to be treated. The tissue 350 can contain
both arteries and veins.
[0037] The radiation source 310 can be configured to provide the
radiation having a wavelength that is preferentially absorbed by
the veins as compared to the arteries. For example, the radiation
can have a wavelength between about 632 nm and 680 nm, or
preferably between about 638 nm and 668 nm, or more preferably
between about 644 nm and 662 nm, or even more preferably about 654
nm.
[0038] The radiation source 310 can include a pulsed dye laser
configured to provide the radiation having an exemplary wavelength
or plurality of wavelengths as described herein. Other types of
laser capable of emitting the radiation at one or more preferred
wavelengths may also be used. Alternatively, an intense pulsed
light (IPL) source can be used. The IPL source may be filtered to
provide radiation having wavelengths close to 654 nm, as described
herein.
[0039] Other radiation source parameters can include pulse
duration, fluence, and spot size. These parameters may be selected
to be similar to parameters used in conventional photothermolysis
techniques, and may be controlled using the control electronics
arrangement 330. Fluence of the applied electromagnetic radiation
(which can have units of J/cm.sup.2) may be selected based on,
e.g., the depth and size of a target vein. For example, pulses of
the radiation may be used in accordance with exemplary embodiments
of the present invention, and can have a duration of, e.g., about 1
to 300 milliseconds, about 10 to 300, or about 20 to 100
milliseconds. Fluence values can be, e.g., between about 20 and 80
J/cm.sup.2. These parameters are exemplary, and other values may be
used depending on the characteristics of the tissue being treated
and the desired degree of thermal damage desired. For example,
further exemplary radiation parameters which may be used for
photothermolysis of blood vessels are described, e.g., in U.S. Pat.
No. 6,306,130.
[0040] The delivery optics arrangement 340 can be used to focus the
radiation to particular regions within the tissue 350 containing
the target vein, in accordance with conventional techniques. Other
options may also be used together with the exemplary system 300
including, e.g., an arrangement capable of providing superficial
cooling to a surface of the tissue being treated.
[0041] The foregoing merely illustrates the principles of the
invention. Various modifications and alterations to the described
embodiments will be apparent to those skilled in the art in view of
the teachings herein. It will thus be appreciated that those
skilled in the art will be able to devise numerous systems,
arrangements and methods which, although not explicitly shown or
described herein, embody the principles of the invention and are
thus within the spirit and scope of the present invention. In
addition, all publications, patents and patent applications
referenced herein are incorporated herein by reference in their
entireties.
* * * * *