U.S. patent application number 13/314548 was filed with the patent office on 2012-04-05 for system and method for microablation of tissue.
This patent application is currently assigned to LUMENIS LTD.. Invention is credited to VITALI EPSHTEIN, YONI IGER, VLADIMIR LEMBERG, JOHN LEE PANNELL.
Application Number | 20120083777 13/314548 |
Document ID | / |
Family ID | 38656076 |
Filed Date | 2012-04-05 |
United States Patent
Application |
20120083777 |
Kind Code |
A1 |
LEMBERG; VLADIMIR ; et
al. |
April 5, 2012 |
SYSTEM AND METHOD FOR MICROABLATION OF TISSUE
Abstract
The present invention generally relates to the field of laser
treatment of tissue, and particularly, to a system and method for
creating microablated channels in skin. The present invention is
more particularly directed to treating subsurface tissue through
the created channels.
Inventors: |
LEMBERG; VLADIMIR; (Santa
Clara, CA) ; EPSHTEIN; VITALI; (Binyamina, IL)
; IGER; YONI; (Haifa, IL) ; PANNELL; JOHN LEE;
(Knoxville, TN) |
Assignee: |
LUMENIS LTD.
Yokneam
IL
|
Family ID: |
38656076 |
Appl. No.: |
13/314548 |
Filed: |
December 8, 2011 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11730017 |
Mar 29, 2007 |
|
|
|
13314548 |
|
|
|
|
60791194 |
Apr 12, 2006 |
|
|
|
60850628 |
Oct 11, 2006 |
|
|
|
60832964 |
Jul 25, 2006 |
|
|
|
Current U.S.
Class: |
606/9 |
Current CPC
Class: |
A61B 2017/00765
20130101; A61B 18/203 20130101; A61B 2018/00452 20130101; A61B
2018/00458 20130101; A61B 2017/00761 20130101 |
Class at
Publication: |
606/9 |
International
Class: |
A61B 18/20 20060101
A61B018/20 |
Claims
1. A laser system comprising: a laser source; a laser emitting
device coupled to the laser source and configured to apply laser
pulses to tissue, the tissue comprising an epidermis region, a
dermis region below the epidermis region, and a hypodermis region
below the dermis region; and a controller configured to control
application of the laser pulses; wherein the controller is
configured to direct the laser emitting device to apply at least
one ablative laser pulse at each of a plurality of sites within a
treatment area of the tissue to ablate a channel at each of the
plurality of sites, each of the ablated channels having a depth
that extends at least into the dermis region of the tissue and a
diameter that is smaller than the depth of the ablated channel;
wherein the controller is configured to determine the number of
sites within the treatment area and a spatial location of each site
within the treatment area such that at least a portion of tissue
between the plurality of sites is not ablated; wherein the
controller is further configured to control characteristics of each
laser pulse such that a duration of each pulse is shorter than a
tissue thermal relaxation time.
2. The laser system of claim 1, wherein the diameter of each of the
ablated channels is less than about 250 .mu.m.
3. The laser system of claim 1, wherein the laser source is a
carbon dioxide (CO2) laser.
4. The laser system of claim 1, wherein each of the ablated
channels has a depth that extends into the hypodermis region.
5. The laser system of claim 1, wherein the controller is further
configured to control characteristics of each laser pulse such that
a profile of thermal damage adjacent to each ablated channel has a
uniform width along the depth of the channel.
6. The laser system of claim 5, wherein the width of the profile of
thermal damage is less than approximately 300 .mu.m.
7. The laser system of claim 1, wherein each ablative laser pulse
has a spot size between about 80 .mu.m to about 150 .mu.m.
8. The laser system of claim 1, wherein the plurality of sites are
a first plurality of sites and the controller is further configured
to direct the laser emitting device to apply at least one ablative
laser pulse at each of a second plurality of sites within the
treatment area of the tissue to ablate a channel at each of the
second plurality of sites such that the ablated channel at each of
the second plurality of sites has a depth and width that is
different from the depth and width of the ablated channel at each
of the first plurality of sites.
9. The laser system of claim 8, wherein the ablated channel at each
of the second plurality of sites has a depth that is smaller than
the depth of the ablated channel at each of the first plurality of
sites; and wherein the ablated channel at each of the second
plurality of sites has a diameter that is larger than the diameter
of the ablated channel at each of the first plurality of sites.
10. The laser system of claim 1, wherein the controller is
configured to direct the laser emitting device to apply a plurality
of ablative laser pulses at each of the plurality of sites such
that the plurality of channels are ablated in sequence.
11. The laser system of claim 1, wherein the controller is
configured to direct the laser emitting device to apply a plurality
of ablative laser pulses at each of the plurality of sites such
that the plurality of channels are ablated approximately
concurrently.
12. The laser system of claim 1, wherein the controller is
configured to direct the laser emitting device to apply at least
one non-ablative laser pulse through the channels formed at the
plurality of sites.
13. The laser system of claim 1, wherein the controller is
configured to control characteristics of each laser pulse such that
each laser pulse has a uniform power distribution across its
respective spot.
14. A method of operating a laser device, the method comprising:
determining how many channels are to be ablated in an area of
tissue; determining a depth and width of each channel such that the
depth is sufficient to extend at least into a dermis region of the
tissue and the width is smaller than the depth; determining a
location for each channel in the area of tissue such that each
channel is separated from the other channels by portions of the
tissue; determining characteristics of ablative laser pulses such
that a duration of each ablative pulse is shorter than a tissue
thermal relaxation time; and directing a laser emitting device to
apply at least one ablative laser pulse to each of the determined
locations based on the determined characteristics to ablate a
channel having the determined depth and width at each of the
determined locations.
15. The method of claim 14, wherein determining characteristics of
the ablative laser pulses comprises determining characteristics of
the ablative laser pulses such that each ablative laser pulse has a
uniform power distribution across its respective spot.
16. The method of claim 14, wherein determining the width of each
channel comprises determining a width that is less than about 250
.mu.m.
17. The method of claim 14, wherein determining the depth of each
channel comprises determining a depth that is sufficient to extend
into a hypodermis region of the tissue.
18. The method of claim 14, wherein determining characteristics of
the ablative laser pulses comprises determining characteristics of
each ablative laser pulse such that a profile of thermal damage
adjacent to each ablated channel has a uniform width along the
depth of the channel.
19. The method of claim 14, wherein determining characteristics of
the ablative laser pulses comprises determining characteristics
such that each ablative laser pulse has a spot size between about
80 .mu.m to about 150 .mu.m.
20. The method of claim 14, wherein the ablated channels comprise a
first plurality of channels, the method further comprising:
determining a depth and width of each of a second plurality of
additional channels such that the depth of each additional channel
is shorter than the depth of each channel in the first plurality of
channels and such that the width of each additional channel is
larger than the width of each channel in the first plurality of
channels; determining a location in the area of tissue for each of
the second plurality of additional channels; and directing the
laser emitting device to ablate an additional channel at each of
the determined locations for the second plurality of additional
channels.
21. The method of claim 14, wherein directing the laser emitting
device to apply at least one ablative laser pulse to each of the
determined locations comprises directing the laser emitting device
to sequentially apply a plurality of ablative laser pulses at each
of the determined locations, one location after another.
22. A laser system comprising: a carbon dioxide laser source; a
laser emitting device coupled to the laser source and configured to
apply laser pulses to tissue, the tissue comprising an epidermis
region, a dermis region below the epidermis region, and a
hypodermis region below the dermis region; and a controller
configured to control application of the laser pulses; wherein the
controller is configured to direct the laser emitting device to
apply at least one ablative laser pulse having a spot size between
about 80 .mu.m to about 150 .mu.m at each of a plurality of sites
within a treatment area of the tissue to ablate a channel that
extends at least into the dermis region at each of the plurality of
sites; wherein the controller is configured to direct the laser
emitting device to apply the at least one ablative laser pulse at
each site in a pattern such that the channel ablated at each site
is separated from the other channels by non-ablated tissue; wherein
the controller is further configured to control characteristics of
each laser pulse such that each laser pulse has a uniform power
distribution across its respective spot and such that a duration of
each pulse is shorter than a tissue thermal relaxation time.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is related to the following co-pending
United States patent applications, all of which are hereby
incorporated herein by reference:
[0002] This application is a continuation of and claims the benefit
of the filing date of U.S. Ser. No. 11/730,017, filed on Mar. 29,
2007, entitled "SYSTEM AND METHOD FOR MICROABLATION OF TISSUE",
which, in turn, claims the benefit of U.S. Ser. No. 60/791,194,
filed on Apr. 12, 2006, entitled "SYSTEM, METHOD AND APPARATUS FOR
LASER TREATMENT OF TISSUE", U.S. Ser. No. 60/850,628, filed on Oct.
11, 2006, entitled "A NOVEL MICROABLATIVE DEVICE", and U.S. Ser.
No. 60/832,964, filed on Jul. 25, 2006, entitled "SYSTEM, METHOD
AND APPARATUS FOR LASER TREATMENT OF TISSUE."
BACKGROUND
[0003] 1. Field of the Invention
[0004] The present invention generally relates to the field of
laser treatment of tissue, and particularly, to a system and method
for creating microablated channels in skin. The present invention
is more particularly directed to treating subsurface tissue through
the created channels. By doing treating subsurface tissue through
uniquely created channels, skin may be treated with heretofore
unrealized results.
[0005] 2. Description of the Related Art
[0006] Skin is primarily made of an outer layer, or epidermis, that
has a depth of approximately 100/an from the outer surface of the
skin and an inner layer, or dermis, that has depth of approximately
3000 fm from the outer surface of the skin. As used herein, "dermal
tissue" or "skin" refers to both the dermis and epidermis
layers.
[0007] There is ongoing demand for procedures to improve skin
defects. Such improvements include reducing wrinkles, reducing
dyschromia (a variety of abnormalities or irregularities of skin
color resulting from, inter alia, irregular pigment distribution,
dilated blood vessels, etc.) and etc. A wide variety of skin
treating techniques have been introduced in recent years for
attempting to achieve this objective. The skin treating techniques
that have been employed may be generally categorized into two
general types of treatment: ablative laser skin resurfacing ("LSR")
and non-ablative collagen remodeling ("NCR"). LSR generally may
result in fairly extensive thermal damage to either the epidermis
and/or the dermis. NCR, on the other hand, is designed to avoid
thermal damage of the epidermis.
[0008] Nevertheless, LSR is an effective laser treatment for
treating skin. A typical LSR procedure comprises thermally damaging
a region of the epidermis 100 and a corresponding lower region of
the dermis 110 for promoting wound healing. Electromagnetic energy
120 is directed towards a region of skin, thereby ablating the skin
and removing both epidermal tissue and dermal tissue. Combining LSR
with a pulsed laser, for example a CO.sub.2 or an Er:YAG laser, is
typically referred to as laser resurfacing or ablative resurfacing.
This is considered to be an effective treatment protocol photo aged
or chronically aged skin, scars, superficial pigmented lesions,
stretch marks, and/or superficial skin lesions. Major drawbacks
include, however, edema, oozing, and burning discomfort up to the
first fourteen (14) days after treatment. Such drawbacks are
unacceptable for many patients. A further problem with LSR
procedures is that they are relatively painful. Therefore, they
generally require an application of a significant amount of
analgesia. While LSR of relatively small areas can be performed
under local anesthesia, LSR procedures that include relatively
large areas frequently require general anesthesia or nerve blockage
by multiple anesthetic injections.
[0009] Another limitation of LSR is that ablative laser resurfacing
generally can not be performed on the patients having dark
complexions. Ablation of pigmented epidermis tissue can cause
severe cosmetic disfigurement to patients having a dark complexion.
Such disfigurement can last from several weeks up to years. This is
generally considered to be unacceptable by most patients and
physicians. Yet another limitation of LSR is that ablative
resurfacing generally has a greater risk of scarring in areas other
than the face and result in an increased incidence of an
unacceptable scar formation because the recovery from skin injury
within these areas is not very effective.
[0010] Several NCR techniques have attempted to overcome the
aforesaid problems associated with LSR procedures. These techniques
may be variously referred to as non-ablative resurfacing,
non-ablative subsurfacing, or non-ablative skin remodeling. Such
NCR techniques generally use non-ablative lasers, flash lamps, or
radio frequency current for damaging the dermal tissue and avoiding
damage to the epidermal tissue. NCR techniques apply the concept
that it is the thermal damage of the dermal tissues that is thought
to induce wound healing. This results in biological repair and the
formation of new dermal collagen which in turn can result in
decreased photoaging related structural damage. Avoiding the
epidermal damage by using NCR techniques may also decrease both the
severity and the duration of treatment related side effects, for
example, post procedural oozing, crusting, pigment changes, and the
incidence of infections.
[0011] Treating skin using the NCR method involves heating
selective portions of dermal tissue within the dermal layer for
inducing wound healing without damaging the epidermis above. By
cooling the surface of the skin and focusing electromagnetic
energy, for example a laser beam, a selected dermal damaged region
can be achieved while leaving the epidermis undamaged. Using
non-ablative lasers for damaging the dermis while leaving the
epidermis undamaged is common to NCR treatment methods. Generally,
using non-ablative lasers result in deeper dermal penetration
depths as compared to the ablative lasers than the
superficially-absorbed ablative Er:YAG and C0.sub.2 lasers used in
typical LSR procedures. Further, when NCR techniques are used, they
generally do not have the undesirable side effects characteristic
of the LSR treatment, such as the risk of scarring or infection.
Examples of NCR techniques and apparatus are disclosed by Anderson
et al. in U.S. Patent Publication No. 2002/0161357.
[0012] Although these NCR techniques may avoid epidermal damage, a
major drawback of this method is its limited effectiveness. For
example, this is significantly less improvement of photoaged skin
or scars after the NCR treatment than when LSR ablative techniques
is used. In fact, even when multiple NCR treatments are employed,
improvement in the patient's skin is often far below expectations.
In addition, improvement is often delayed for several months when a
series of treatment procedures are used. Although NCR techniques
have been found to be moderately effective for wrinkle removal,
they have generally not been found to be effective for
dyschromia
[0013] Another problem with using a NCR technique is the limited
the breadth of acceptable treatment parameters for safe and
effective treatment of dermatological disorders. This is because
NCR procedures generally rely on an optimum coordination of laser
energy and cooling parameters. This results in an unfavorable
temperature profile in the skin. An unfavorable temperature profile
consequently results in either no therapeutic effect on one hand,
or scar formation due to the overheating of a relatively large
volume of the tissue, on the other.
[0014] A problem that is common to both ablative and non-ablative
resurfacing procedures is that they do not significantly use
keratinocytes, which play an active role in the wound healing
response. Keratinocytes release cytokines when the keratinocyte is
damaged. Cytokines encourage wound healing. For example, during
ablative resurfacing procedures, keratinocytes are removed from the
skin along with the epidermis. This removes keratinocytes entirely
from the healing process altogether. During non-ablative
procedures, keratinocytes, located in the epidermis, are not
damaged at all and thus do not release cytokines for aiding the
healing process.
[0015] Accordingly, there is now provided with this invention an
improved system and method for treating skin that effectively
overcomes the aforementioned difficulties and longstanding problems
inherent in using either a LSR or a NCR procedure. These problems
have been solved in a simple, convenient, and highly effective way
by which to treat skin.
SUMMARY OF THE INVENTION
[0016] According to one aspect of the invention, a method for
treating tissue is disclosed. The method comprises applying
electromagnetic radiation to the tissue for ablating a channel
therein having a predetermined width and predetermined depth. The
method includes non-ablatively heating tissue on the bottom of the
channel with electromagnetic radiation and creating a thermal
affected zone of predetermined volume proximate said channel.
[0017] According to another aspect of the invention, a system for
treating tissue, is disclosed which comprises an electromagnetic
radiation source and an electromagnetic radiation emitting device
for applying the electromagnetic radiation to the tissue for
forming a channel therein having a predetermined width,
predetermined depth, and a thermal affected zone of predetermined
volume proximate said channel.
[0018] As will be appreciated by those persons skilled in the art,
a major advantage provided by the present invention is full control
of: depth of treatment, the amount and placement of heat, and the
amount and placement of channels. It is therefore an object of the
present invention to rejuvenate skin and reduce wrinkles, scars,
dyschromia and other conditions such as melasma and
hyperpigmentation. It is another object to provide a channel with
or without heat for delivery other therapy (vitamins, drugs, etc).
Additional objects of the present invention will become apparent
from the following description.
[0019] The method and apparatus of the present invention will be
better understood by reference to the following detailed discussion
of specific embodiments and the attached figures which illustrate
and exemplify such embodiments.
DESCRIPTION OF THE DRAWINGS
[0020] A specific embodiment of the present invention will be
described with reference to the following drawings, wherein:
[0021] FIG. 1 is a schematic illustration of a microablation method
and system in accordance with an embodiment of the invention;
[0022] FIGS. 2A, 2B, 2C, and 2D are schematic illustrations of
sequential stages of microablation and treatment in accordance with
an embodiment of the invention;
[0023] FIGS. 3A, 3B, 3C, and 3D are schematic illustrations of
sequential stages of microablation in accordance with an embodiment
of the invention;
[0024] FIGS. 4A, 4B, 4C, and 4D are schematic illustrations of
tissue manipulation in accordance with an embodiment of the
invention;
[0025] FIG. 5 is a schematic illustration of tissue treatment
according to an embodiment of the invention; and
[0026] FIG. 6 is a schematic flow chart of a method of producing
microablation on a tissue in accordance with an embodiment of the
invention; and
[0027] FIG. 7 is a schematic flow chart of a method of producing
microablation on a tissue in accordance with an embodiment of the
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0028] The following preferred embodiment as exemplified by the
drawings is illustrative of the invention and is not intended to
limit the invention as encompassed by the claims of this
application. A system and method for treating skin is disclosed
herein. In skin tissue, for example, proteins such as collagen
reside in the dermal layer of the skin. The microchannel disclosed
in an embodiment of the present invention may itself target and
alter the collagen fibers within the dermis as an effective
treatment for wrinkles of the skin. Alternatively, an embodiment of
the microchannel disclosed herein may create a passage through
which targeted tissue is treated.
[0029] As shown generally in FIG. 1, an embodiment of the present
invention provides a system and method for performing microscopic
ablation or partial microablation of e.g. tissue, and forming a
microchannel through a surface of tissue to treat subsurface
tissue. The microchannel may provide access to subsurface tissue
targeted for a prescribed treatment, or the microchannel itself may
provide a prescribed treatment. In some embodiments of the present
invention, the microchannel may produce partial lateral
denaturation of proteins (e.g. collagen) within the walls and/or at
the bottom of the channel.
[0030] According to some embodiments of the invention, a tissue
ablation system 1 may include a laser unit 2 and a laser emitting
device 3 for ablating a microchannel 6 into a tissue 5, for
example, for applying a treatment thereto as will be described
below in detail. The microchannel 6 may be, e.g. a column, a well,
a hole, or the like, created in the tissue 5 by ablating the tissue
5 by the laser emitting device 3 and the laser beam 4, for example,
an ablating laser beam. Microablation of the tissue 5 may result in
ablation of the microchannel. Microablation of the tissue may also
result in dissipation of heat from the heated and evaporated tissue
by the tissue surrounding the resultant microchannel 6. Thus,
ablation of the tissue 5, producing the microchannel 6, may result
in a thermal affected zone 7 surrounding the walls and/or bottom of
the microchannel 6. The thermal affected zone 7 is generally
indicative of damaged tissue and of tissue necrosis (the death of
cells) in particular. As used herein, "damaged" is defined as
inducing cell death in one or more regions of the dermal tissue of
interest ("lethal damage"), or stimulating the release of
cytokines, heat shock proteins, and other wound healing factors
without stimulating necrotic cell death ("sublethal damage").
[0031] Selection of the laser beam 4 may also be based on the
absorptive qualities of the tissue 5 to be treated. The absorptive
properties of the tissue 5 to be treated may dictate or influence
specific the type of laser or the characteristics of that laser
suitable for a particular treatment for and/or microchannel. For
example, certain lasers may reach depths unable to be reached by
other types of lasers. As an example, an ablative laser may reach
up to any depth required while non-ablative lasers may be unable to
penetrate skin below, for example, about 50 .mu.m. Similarly, it
may be difficult to reach energy doses with one type of laser that
are easily reached with others. Of course, as is well known in the
art, if the wavelength is altered, the corresponding absorption
level of the skin treatment area will be altered. Therefore, as
long as the fluence described herein is maintained for achieving
the microablation disclosed herein, different lasers having
different characteristics may be used for achieving the same or
similar results disclosed.
[0032] The microchannel 6 may be characterized by certain
parameters, for example, diameter D and depth h. The diameter D of
the microchannel and the depth h of the microchannel generally may
be controlled by the energy characteristics of the laser. Such
energy characteristics include, for example, wavelength, power, and
the beam profile of the laser. Characteristics of the beam profile
of the laser include, for example, pulse width, pulse duration, and
pulse frequency). Furthermore, the profile and volume of the
thermal affected zone may be formed by using different laser beam
characteristics, such as chosen wavelength, energy of individual
pulse or defined sequence of pulses, duration of each pulse, power
distribution, shape of the laser spot, and the like, as will be
outlined in detail below.
[0033] In some embodiments of the invention, the diameter of the
ablated microchannel 6 may range from about 10 .mu.m to about 500
.mu.m, preferably in the range from about 50 .mu.m to about 250
.mu.m. Microchannel diameter D may depend on the type of laser used
and other parameters, for example, the elasticity of the skin. It
has been found that the bottom of the formed microchannel is often
conical due to the elastic forces of the skin as well as the power
energy distribution of the spot formed by the laser.
[0034] The depth of the microchannel may be determined by the
attending physician based upon the treatment required or selected
by the physician. For example, treatment of collagen (collagen
remodeling) typically located at a depth in the range from about
200 .mu.m to about 2 mm from the surface of skin tissue may be
desired. Treatment of blood vessels may necessitate a microchannel
extending up to approximately 0.5 mm, which is where blood vessels
are typically located. The microchannel 6 may therefore be created
in accordance with an embodiment of this invention to a
predetermined depth h to effect treatment to collagen or blood
vessels or any other portion of the dermis selected by the
attending physician. According to some embodiments of the present
invention, the laser device 4 may produce the microchannel 6
reaching, for example, in the range from about 100 .mu.m to about 3
mm in depth below the surface of the tissue 5.
[0035] Any suitable type of laser may be used, for ablating the
microchannel, for example, CO.sub.2 laser, Er:YAG, Tm:YAG, Tm fiber
laser, Er fiber laser, Ho fiber laser, etc. or any other laser type
as is well known in the art which may match a predetermined
operational parameter such as, for example, optical absorption by
tissue and intensity of laser that are strong enough to ablate
small volumes with minimal lateral damage. The laser emitting
device 3 may therefore be adapted for emitting an ablative laser
beam 4 having any suitable power level and/or spot size and/or
other associated characteristics. The laser power level may range,
for example, in the range from about 0.5 mJ to about 250 mJ. The
spot size of the laser beam 4 on the tissue surface may range, for
example, in the range from about 10 .mu.m to about 50 .mu.m. For
example, a CO.sub.2 laser may use a spot size ranging from about 80
.mu.m to about 150 .mu.m for ablative treatment and preferably
about 80 .mu.m.
[0036] In some embodiments of the present invention, the ablation
may be produced by a continuous wave laser, by a single pulse of a
laser, or by a series of pulses. The selection of these forms may
depend, for example, upon the depth of the microchannel required,
the diameter of the microchannel, as well as the size of the
thermal affected zone, that is, the width of the lateral damage. In
an embodiment using a continuous wave laser, for example, an
ablating laser operating in a wavelength of 10.6 nm, the laser
emitting device 3 may be operated at a power level of, e.g., in the
range from about 1.0 W to about 250 W for a duration of, e.g., in
the range from about 0.02 msec to about 500 msec. In an embodiment
using a pulsed CO.sub.2 laser, for example, a series of, for
example, 10 pulses, each having a duration of, for example in the
range from about 0.05 msec to about 100 msec may be fired at an
energy level of, e.g. in the range from about 0.2 mJ to about 20
mJ. In an embodiment using a pulsed laser, a series of pulses, each
having a duration of from about 0.05 msec to about 100 msec may be
fired may be fired at an energy level of in the range from about
0.2 mJ to about 20 mJ. In skin, for example, applying a pulsed
laser as indicated above may result in a microchannel 6 of a
diameter in the range of from about 80 .mu.m to about 100 .mu.m, a
depth in the range of from about 300 .mu.m to about 500 .mu.m, and
a thermal affected zone of lateral width in the range of from about
20 .mu.m to about 300 .mu.m. Additionally, as described below in an
embodiment of the invention, a series of pulses, of pulsed laser
may be fired at the tissue 5 to further deepen the microchannel 6,
created as identified above. The microchannel 6 may be deepened to
a desired depth, preferably to the level of the tissue to be
non-ablatively treated. It should be noted that the diameter of the
deepened microchannel 6 may be in the same range or different range
as the previously created microchannel in the same location.
[0037] In some embodiments of the invention, the microablation
channel 6 may be sculpted by employing different pulse
characteristics of the laser beam. Pulse characteristics of a laser
beam, e.g. laser beam 4, may further include different energy
profiles. As mentioned above, the depth h of the microchannel and
the resulting width of lateral damage and the profile of the
thermal affected zone 7 may be controlled by different laser beam
characteristics. For example, the laser beam 4 may have
characteristics resulting in the thermal affected zone 7 having a
substantially constant width (linear profile) 7. It will be
recognized that some embodiments of the invention may have a
thermal affected zone 7 profile different from the one depicted in
FIG. 1. Furthermore, it is now possible to produce a microchannel 6
according to embodiments of the present invention with a minimal
thermal affected zone 7, e.g. a width in the range from about 1
.mu.m to about 5 .mu.m with the use of the Er:YAG laser.
[0038] In some embodiments of the present invention, the laser unit
2 may include a controller 12 able to control the laser emitting
device 3, and an input interface 13 capable of receiving input
parameters from user of system 1. Such input parameters may be for
defining microablation treatment parameters, for example. User
input parameters to the interface 13 may further include the
microchannel depth, the spatial location of the microchannel 6 on
the tissue surface 1, etc. Parameters may be provided at the input
interface 13 by an operator of the system, for example, a
physician, or alternatively, through an imager program detailed
below. The controller 12 may be able to perform at least one of the
following functions, as will be described in more detail below: (a)
identifying at least one location for treatment; (b) selecting
treatment(s) for each of at least one location; (c) operating a
laser and directing mechanism to produce the at least one
microablation; and (d) delivering the selected treatment(s) at the
at least one site.
[0039] Reference is now made to FIGS. 2A, 2B, 2C, and 2D which
schematically illustrate sequential stages of microablation and
treatment in accordance with an embodiment of the invention.
According to an embodiment of the invention, it may be desirable to
apply treatment to tissue which may be, for example, in the
hypodermis 10 in a way that substantially maintains the profile of
the thermal affected zone throughout the treatment protocol. As it
is desirable to minimize the necrosis of tissue at the surface 11,
it may be beneficial to apply a plurality of laser pulses onto the
tissue 5 in order to reach a depth of treatment area in the
hypodermis 10. As illustrated in FIG. 2A, the microchannel 6
created by a first ablative laser pulse, may have the desired
thermal affected zone 7, e.g. linear profile of constant width, for
example, a minimal width, and may have a depth of h1 that is not
sufficiently deep to provide treatment to the hypodermis 10. A
second ablative laser pulse may be applied through microchannel 6
of FIG. 2A to deepen the microchannel 6 having a minimal thermal
affected zone to a depth h2 into, for example, the dermis 9 of the
tissue 5, while maintaining the predetermined minimal thermal
affected zone profile, as illustrated in FIG. 2B. Finally, as
indicated in FIG. 2C, a third ablative laser pulse may be applied
through the microchannel 6 of FIG. 2B to deepen the microchannel 6
having a minimal thermal affected zone 7 further to a depth h3 into
the targeted hypodermis layer 10, while maintaining the
predetermined thermal affected zone profile 7. Alternatively, if a
non-ablative pulse is applied after the profile depicted in FIG.
2B, the profile may appear as depicted in FIG. 2D.
[0040] According to some embodiments of the invention, a delay
representing a minimum time, e.g. 1 to 100 msec, may pass between
each laser pulse, thereby allowing relevant portions of tissue 5 to
cool down between each pulse. This delay may be between any
succession of laser pulses whether they are ablative or
non-ablative. It is preferable to have a delay after an ablative
laser pulse. To allow for cooling of tissue 5, the minimum time
between pulses may be determined according to, for example, a
predetermined tissue relaxation time which may define, e.g. the
time required to dissipate a certain amount of heat absorbed by,
e.g. the tissue 5, during a laser pulse applied by the laser device
3. The delay may also allow venting of ablative tissue and or gases
that may have developed during an ablative pulse of light.
Accordingly, if a time of an applied pulse is shorter than the
tissue relaxation time and the beam has a top hat profile a very
low amount of heat may dissipate through walls of the microchannel
6.
[0041] A beam profile that would conform to an inverted top bat may
be preferable in some embodiments of the present invention for
forming a channel with well defined side walls, minimal
microchannel diameter, and a minimal thermal affected zone.
Typically, a beam has a Gaussian power distribution across the
diameter of its spot. Since the power on the edges of such a spot
is less than the power in the center of the spot, it is often
difficult to form a straight walled channel or hole. By having a
beam profile that has a uniform power distribution across its spot
(a top hat profile) it will be easier to form a straight walled
channel.
[0042] In some embodiments of the invention, upon producing the
microchannel and clearing a path to the treatment site, a wide
variety of types of treatment may be delivered to the site, as
detailed below. In some embodiments, the treatment may be
non-ablative laser treatment. Such non-ablative laser treatment may
be used, for example, for remodeling collagen. As is more
particularly illustrated in FIG. 2D, a non-ablative laser treatment
may be delivered to the tissue 5 in the dermis 9 after the
microchannel 6 has been created. The path created for the
non-ablative heating of the target tissue may follow embodiments of
the invention detailed above regarding FIGS. 2A, or 2B and/or 2C.
That is, heating of subsurface tissue by a non-ablative laser
through the created microchannel may be through a microchannel that
was created by one or by more that one ablative pulses. Laser
treatment by the laser beam 4 may be applied to the tissue 5 in the
dermis 9, whereby the tissue 5 is heated to a temperature below
that at which the tissue is ablated though heated to a temperature
sufficient to denature collagen, for example, in the range of from
about 50.degree. C. to about 67.degree. C. The non-ablative laser
beam 4 may further create a thermal affected zone of denatured
collagen 17, without tissue ablation, whereby collagen is heated.
The collagen thereupon contracts, thus removing wrinkles. The
non-ablative laser beam 4 may further be applied to targeted tissue
for removing pigmentation, treating blood vessels, and other
treatments, as is well known to those skilled in the art.
[0043] Accordingly, it will be appreciated that the use of the
microchannel 6 of the present invention as a conduit for applying
non-ablative heat to targeted subsurface tissue, enables the
heating of the subsurface tissue to be treated without excessively
damaging non-targeted tissue, for example, the surface tissue.
Further, the thermal affected zone may be additionally controlled
by having non-ablative heating applications interposed between
ablative treatments for creating a larger thermal affected zone 17
deep in the tissue, for example in the dermis 9.
[0044] Reference is now additionally made to FIGS. 3A, 3B, 3C, and
3D which schematically illustrate sequential stages of treatment in
microablation channels in accordance with embodiments of the
invention. In accordance with to some embodiments of the invention,
it may be desirable to create a predetermined non-uniform thermal
affected zone profile and/or lateral width damaged area along the
depth of the channel. In other embodiments of the invention, an
area of tissue in the dermis 9 may be, treated for forming a
predetermined thermal affected zone having a profile different from
the profile of the thermal affected zone in the epidermis 8 near
the surface. As is more particularly illustrated in FIG. 3A, the
microchannel 6 having a predetermined thermal affected zone and/or
profile 7a and a depth h1 may be created by a first ablative laser
pulse. As illustrated in FIG. 2D, a second laser non-ablative laser
pulse may heat the bottom of the microchannel 6 thereby damaging a
spherical area surrounding the bottom of the channel to a depth h3,
reaching for example, beyond the dermis 9. This second pulse may
have different characteristics than the first pulse, producing a
thermal affected zone having a different area and/or profile than
the first pulse and resulting in the profile illustrated in FIG.
2D. When a second ablative laser pulse (that is, the third pulse to
this treatment area) is applied through the damaged tissue on the
bottom of the microchannel, a profile 7b as depicted in FIG. 3B is
formed. Thus, FIG. 3B depicts an ablative laser pulse applied
subsequent to the non-ablative laser pulse which formed the profile
depicted in FIG. 2D. Alternating ablative laser treatment with
non-ablative laser treatment may result, for example, in a
microchannel having a thermal affected profile as illustrated in
FIG. 3C. It will be understood that a microchannel may be produced
to any depth and by any number of pulses for creating a series of
predetermined thermal affected zones that may vary along the depth
of the microchannel. In this way, a predetermined thermal affected
zone profile along the microchannel 6 is formed. It is thus
possible to build a variety of predetermined thermal affected zone
areas and/or profiles along the wall and/or the bottom of the
microablated channel, using a sequence of pulses with different
parameters (e.g. energy and duration or wavelength) and employing
the natural thermal conductivity of tissue. For example, in another
embodiment of the invention, an ablative laser pulse applied to the
tissue 5 may have characteristics producing a thermal affected zone
having an area and/or profile 7d as illustrated in FIG. 3D. The
thermal affected zone 7d in FIG. 3D illustrates that the thermal
affected zone area may decrease along the depth of the channel,
according to predetermined laser beam parameters. Of course, once
the depth of the tissue targeted for treatment is reached, the
non-ablative heating of the tissue should preferably commence.
[0045] In some embodiments of the present invention, the creation
of the microchannel 6 with the desired thermal affected zone
profile 7 along the walls and/or bottom of the microchannel 6 may
itself be the desired treatment method. Additionally or
alternatively, creating the microchannel 6 itself may facilitate
the desired treatment method, by providing access directly to a
subcutaneous site for treatment. For example, upon completion of
the microchannel, a substance may be delivered to the treatment
site by any means, including for example, ultrasonic delivery.
Additionally or alternatively, the microchannel may serve as a
conduit for transdermal substance delivery, for example, for
diffusion, electrophoresis, ointments, acids, healing substances,
chemical peeling agents, collagen modification agents, fillers,
stem cells, or any variety of administering medicines and the like.
It will be noted that the depth of the microchannel need not be the
only or even the primary treatment site; rather the treatment site
may be any and all sites along the walls and/or bottom of the
microchannel adjacent to or proximate the microchannel.
[0046] In some embodiments of the invention, the controller 12 may
provide 3 a command via a signal 14 to the laser device for
applying a pulse or series of pulses to the tissue 5. The
controller may provide a variety of commands to the laser device 3,
for example, the sequence and duration of pulses to apply to the
tissue 5. The controller may also select form a variety of laser
sources for applying a desired sequence of ablative and
non-ablative laser applications to a particular site. The
controller may also prescribe the desired delay between the laser
applications. Furthermore, the controller 12 enables the laser
emitting device 3 to deliver precise multi-spot ablation to
selective portions of tissue in accordance with preselected
treatment protocols as is well known by the physician.
[0047] In some embodiments, more than one microchannel may be
produced substantially concurrently or in rapid sequence on the
tissue 5, for example, by directing the laser emitting device 3
from one predetermined site to another of the tissue 5, applying a
pulse at each site and returning precisely to the previously
treated site so as to apply the next pulse in the sequence. Thus,
while the tissue 5 at one microchannel is cooling, the controller
12 may send a command to the laser device 3 to move among one or
more sites on the tissue 5 for creating a plurality of
microchannels at a plurality of sites. Such a device may use, for
example, a laser scanner. Such scanners may operate in accordance
with the teachings in U.S. Pat. Nos. 5,713,902; 5,957,915; and
6,328,733, all of which are incorporated herein by reference. For
example, at a first scanning sequence, the laser device 3 may
provide the laser beam 4 on the first site resulting in a
microchannel of depth h1. The controller 12 may then move the laser
device 3 to a second site to produce thereon a microchannel having
a depth h1. This process may continue until the laser device 3
performed on each location has a microchannel resulting in depth
h1. The controller 12 may then proceed to provide the laser beam 4
on a microchannel site further ablating a microchannel resulting in
another microchannel of depth h2 directly below the first
microchannel site. Alternatively, the second laser application may
be a non-ablative laser beam. The controller 12 may then move the
laser device 3 to a second site to produce a microchannel of depth
h2. This process may continue until the laser device 3 performed on
each microchannel location of depth h1 a second laser beam pulse
resulting in a microchannel of depth h2. Of course, the order of
the second beam across the selected treatment sites may be in a
different order or sequence than the first pass. Alternative
scanning sequences may apply laser beam pulses repeatedly at a
location, then moving to another location to apply laser pulses. It
may not be necessary that the same series of pulses
(characteristics including duration and power) be applied at each
location in the sequence and any number of series of pulses may be
applied to tissue at various locations.
[0048] In some embodiments of the invention, the tissue 5 may be
manipulated and the laser emitting device 3 positioned for applying
the laser beam 4 to the tissue 5. For example, the skin tissue to
be treated may be lifted and the laser beam 4 may be applied from
the side. Furthermore, the controller 12 may direct the laser
emitting device 3 to apply the laser beam 3 to the tissue 5 from a
variety of angles from the perpendicular.
[0049] In another embodiment of the invention, it may be desirable
to increase the amount of radiation per unit of surface area of the
tissue 5. For example, the tissue 5 may be stretched prior to
applying laser beam 4 to the tissue. Referring to FIG. 4A, laser
beam 4 may be applied to unstretched tissue 5 over a surface area
19 of tissue. The tissue 5 may be stretched in a variety of
directions as selected by the physician, for example, the lateral
direction, manually or by some device applying a stretch 20, prior
to producing the microchannel 6 as detailed above in an embodiment
of the invention. Referring to FIG. 4B, applying stretch 20 to the
tissue 5, effectively increases the amount of radiation per unit
surface area 19 of the tissue 5. The microchannel 6 (FIG. 4C)
created in the stretched tissue 5 will possess dimensions and
characteristics as detailed above. Release of the tissue stretch
13, may result in a relaxed tissue 5 wherein the microchannel 6 now
possesses a smaller diameter D' (i.e. D'<D; Ref. FIG. 4D). The
reduction in microchannel diameter may also be a function of tissue
properties, for example, tissue elasticity, tissue hydrated
conditions, and the thickness of the stratum corneum. Thus, by
stretching the skin prior to a laser beam is applied, the area of
damaged skin may be further reduced. Stretching the skin has many
advantages beyond just minimizing the amount of damaged skin. For
example, by stretching the skin during the application of an
ablative laser for creating a microchannel, the diameter of the
microchannel will be further reduced. In this way, infection has a
smaller entrance point and the chance for infection may be further
minimized. Stretching the skin during the application of the laser
beam (both an ablative laser beam and a non-ablative laser beam)
provides additional advantages, for example, better penetration,
better evacuation of vapors, and being less sensitive to the
position of the target relative to the applied beam.
[0050] The system may also include an imager to enable a user to
view the tissue area and to choose a treatment site. For example,
the imager and an image processor may be used to determine the
wrinkle topology of a tissue. For example, by using the imager
combined with the application of polarized light, the outline,
depth, and profile of the skin's topology may be more precisely
determined. The wrinkle topology may be provided to the input
interface 13 to communicate with the controller 12 and send a
signal 14 to the laser device 3 to maximize the aim of the laser
device 3 to the target tissue 5. The wrinkle topology may be used
to measure the effectiveness of the treatment as well as used for
identifying targeted sites that may require additional
treatment.
[0051] An imager may also be used to generate optical feedback,
either manually to the eye of the user, or automatically to an
image processor, in order to return the laser to a previously
treated site. The processor may process the image obtained from the
imager for providing information to the controller for varying the
treatment locations, the particular laser to be used, the laser
spot size, the spot location, etc. In this manner, if the patient
moved between pulses, an imager and processor may enable returning
the laser to the precise site of the previous pulse. Use of an
imager to optically track or determine tissue position may be used
in concert with the process described above of the sequential
creation of microchannels, as is well known to those skilled in the
art.
[0052] As shown in FIG. 5, in another embodiment of the invention,
the microchannel may be used to facilitate treatment to
subcutaneous tissue by a means other than through the microchannel
itself. The void of the microchannel may act as a barrier, or
insulating separation of air, between layers of tissue on either
side of the microchannel. Therefore, a microchannel may be used in
conjunction with radio frequency (RF) energy treatment to allow
driving a current below the microchannel. As illustrated, the
microchannel 6 is created according to an embodiment of the present
invention detailed above, having a width W, a length L, and a depth
h. In this embodiment, the microchannel depth h reaches into the
dermis of the tissue and the targeted tissue is beneath the
microchannel 6 in the dermis 9. Radio frequency electrodes 15 and
16 may be applied to the tissue at opposite sides of the
microchannel 6. When RF current 18 is applied, the insulating
(non-conducting) property of the microchannel 6 requires the
current to flow between electrodes 15 and 16, below the
microchannel depth h, directing the current to deeper tissue than
would have occurred in the absence of the microchannel 6. The
length L of the microchannel should preferably be at least twice
its depth (2D) so that the applied current may go through the
targeted tissue and not find an alternate path of less resistance.
The length of the microchannel in this embodiment of the invention
may be in the range of from about 100 .mu.m to about 500 .mu.m, and
preferably about 300 .mu.m. Accordingly, it will be appreciated
that by using the microchannels of the present invention, the
heating of deeper layers of tissue may be achieved without damaging
the surface tissue. It will further be appreciated that controlling
the dimensions of the microchannel, e.g., the depth, width, and/or
length of the microchannels may define the treatment provided by
the treatment device, e.g., the RF electrodes, to the treatment
layer of the tissue. It will be noted that by concentrating the
current, the microchannel may provide for increased current density
at the desired treatment site. A similar approach may be used for
heating and followed shrinkage of collagen fibers at a
predetermined depth.
[0053] Creating a microchannel into the tissue for reaching an area
of targeted treatment may also be achieved without an ablative
laser. For example, a microchannel may be created mechanically with
a heated microneedle. After the microchannel is thus formed,
non-ablative treatment may be applied
[0054] Reference is now made to FIG. 6, which schematically
illustrates a flow-chart of a method for performing micro-ablation
on a tissue in accordance with an embodiment of the invention. As
indicated at block 601, the method may include, for example,
positioning the laser device for performing microchannel ablation.
For example, the user of the system 1 may initially position the
laser device 3 relative to the skin 5 to enable creating the
microchannel at a desired location. As indicated at block 602, the
method may also include, for example, determining the depth of the
microchannel. For example, the user may determine that the desired
depth of the microchannel 6 (FIGS. 2A, 2B and 2C) is h3. As
indicated at block 603, the method may also include, for example,
determining the width of the microchannel and/or the thermal
affected zone. For example, the user may determine that the desired
width of the microchannel 6 is D (FIG. 1) and the desired thermal
affected zone profile may vary as in 7a, 7b, 7c, and 7d (FIGS. 3A,
3B, 3C and 3D). The density of microchannels (e.g., number of
channels per area) can also be determined. The wavelength for the
different stages of the ablation may also be determined. As
indicated at block 604, the method may also include, for example,
producing a microchannel. For example, the laser device 3 may emit
a laser beam and may thereby produce the microchannel 6 in the
tissue 5. As indicated at block 605, the method may also include,
for example, applying treatment onto a microchannel location. For
example, applying heat treatment to affect collagen at bottom of
microchannel 6 (FIG. 2D). It will be recognized that the step of
applying treatment is optional and need not be practiced in every
embodiment of the invention.
[0055] FIG. 7 depicts a flow chart method in accordance with
embodiments of the present invention. At block 700, the orientation
of the tissue 5 is selected for treatment, the tissue, e.g. skin is
stretched, lifted, or left natural. At block 701, image analysis of
the tissue surface is performed, for example, to create wrinkle
topology, to provide information to the controller 12 (FIG. 1) in
order to maximize laser orientation. It will be recognized that the
step of image analysis is optional and need not be practiced in
every embodiment of the invention. At blocks 702 and 703, the depth
and width of the microchannels may be determined respectively, for
example, based on the treatment program selected or selected by the
operator. At block 704, the thermal affected zone (e.g. area and/or
diameter of necrosis) may be determined, for example, by setting
the pulse duration, pulse energy, the number of pulses, or the
density of the pulses based on the treatment program, or based on
selection by the operator. At block 705, the area of collagen
shrinkage (i.e. thermal affected zone 17) may be determined (FIG.
2D). At block 706, a treatment pattern or program may be
determined, for example, by the operator of the device selecting an
appropriate program. At block 707, the size of the microchannel
pattern may be determined, for example, automatically by scanning,
or based on the treatment program, or by an operator selecting the
appropriate pattern size. At block 708, the fill factor, for
example, the density of the microchannels on the tissue, may be
determined, for example, automatically by the device, e.g., based
on the treatment program, or by selection by the operator of the
device. At block 709, the device may be positioned on the tissue,
and at block 710, the treatment may be performed by forming the
microchannels, and/or applying any other desired treatment.
[0056] It will be appreciated by persons of ordinary skill in the
art that according to some embodiments of the present invention
other applications according to the principles of the present
invention are possible and are in the scope of this application.
While certain features of the invention have been illustrated and
described herein, many modifications, substitutions, changes, and
equivalents will now occur to those of ordinary skill in the art.
It is, therefore, to be understood that the appended claims are
intended to cover all such modifications and changes as fall within
the true spirit of the invention.
Example
[0057] It is to be understood that the following example of the
present invention is not intended to restrict the present invention
since many more modifications may be made within the scope of the
claims without departing from the spirit thereof.
[0058] A study was conducted that consisted of two research
criteria. The first criterion evaluated different laser energy
doses on 47 consecutive samples of skin. The doses ranged from 5 mT
to 200 mJ. The width and depth of the ablated "column" was measured
as well as the surrounding width and depth of necrosis. The second
criterion compared the effects of doses ranging from 5 mJ to 20 mJ
on the arms of selected volunteers. These evaluations were recorded
immediately after the firing of the laser; at one hour; one day and
four days.
Summary of Results or Findings
[0059] The depth and diameter of the ablated columns correlated in
a linear fashion with the dose. The column depth could be directly
controlled and ranged from 180 to 1378 microns, depending on the
dose level. Despite the wide range of dosing parameters, the column
diameter was tightly confined and only ranged from 34-106 microns
with most of column diameters being in the 50-70 micron range.
Necrosis depth ranged from 27-213 microns. Necrosis width was
extremely confined and ranged only from 19-55 microns.
Histologically, the ablated columns produced by 5 mJ and 10 mJ
pulses reached the mid-to deep-dermis; columns only penetrated to
the fat at the highest dose (200 mJ). On doses of 5, 10, and 20 mJ,
the resultant skin erythema and edema was evident at 1-2 days, but
the mild to moderate erythema faded by the fourth day. There were
no cases of necrosis.
CONCLUSIONS REACHED
[0060] Utilizing histologic evaluation, it is a novel carbon
dioxide based microablation device can produce selective digital
injury to dermal collagen using very low energy levels. The
collateral necrosis is very limited. Preliminary clinical
evaluation using low energy doses demonstrates mild to moderate
erythema that fades at four days. These findings will be used to
determine the dosing for future clinical studies.
[0061] Although the particular embodiments shown and described
above will prove to be useful in many applications in the skin
treatment art to which the present invention pertains, further
modifications of the present invention will occur to persons
skilled in the art. All such modifications are deemed to be within
the scope and spirit of the present invention as defined by the
appended claims.
* * * * *