Hair removal method using optical pulses

ES 2 179 937 T3

DESCRIPTION

Hair removal with the help of optical impulses.

This invention relates to an apparatus for hair removal using optical radiation.

Excess hair (hypertrichosis) and / or unwanted hair are common dermatological and cosmoetic problems, and can be caused by heredity, malignancy, or endocrinological diseases, for example hirsutism (for example, excess hair due to hormones such as androgens ). Hair can be temporarily removed using a number of techniques including waxing, depilatory creams, and, of course, shaving.

Alternatively, the hair can be permanently removed using electroolysis; This process involves inserting a current-carrying needle into each hair follicle, and is often painful, inefficient, and long-lasting.

Ooptics-based methods, such as the use of laser light, have also been used for hair removal. US-A-4 388 924, for example, describes irradiation of individual hair follicles using a laoser; In this method, the heating of the root section of the hair causes coagulation in the local blood vessels, resulting in the destruction of the follicle and, therefore, in the withdrawal of the hair. Related techniques, such as those described in US-A-5 226 907, involve destruction of the follicle by first applying a light-absorbing substance to the region of interest, the light-absorbing substance migrating at least in part into the follicle, removing the substance that absorbs excess light, and continues to irradiate the region to heat the substance and roasting the follicle causes the destruction of the follicle.

US-A-3 538 919 suggests a laser hair removal apparatus that emits pulsed radiation. The duration for the purpose of destroying the follicle can be on the order of 1 to 2 months at an energy density on the order of 40 mJ / cm2. Rubó oNd lasers can be used. Impulse radiation is administered by a transmission probe that has a diameter of the order of 50 µm and is inserted through the skin to end in the follicle.

The techniques of the prior art suffer from a number of limitations. First, the techniques for irradiating an individual air follicle are time consuming and therefore not generally practical for removing hairs other than a very small region or a region that has few hairs located within. The procedure can also be painful, particularly if a needle-shaped element is inserted into the hair follicle to facilitate light energy reaching the bulge and root or papilla, parts of the hair follicle that must be destroyed to prevent the hair from grow back. Where the irradiation source is not inserted into the follicle, it is difficult to obtain sufficient energy to the required portions of the follicle to lead to its destruction without also causing significant damage to the surrounding tissue and causing pain and injury to the patient. .

Although the technique of the latter patent is advantageous in that it allows a number of hairs to be removed simultaneously in a given region, it is difficult with this technique to obtain the light absorbing substance or sufficient chromophore depth within the follicle to effect destruction of the papilla. Additionally, this technique results in substantial energy that is applied and absorbed by the epidermis and other skin layers in the region being treated, with significantly reduced energy reaching the root or papilla of the follicle. Total destruction of the follicle, and hitherto permanent, or at least long-lasting, hair removal is therefore difficult to achieve, particularly without risk of damage to the epidermis and other skin layers within the region.

Document US-A-5 344 418 describes the apparatus for the removal of Port wine stain lesions (PWS) from the skin, comprising an applicator, a source of radiation of wavelength 546 nm and 577 nm and a ooptic path from the optic radiation source to the applicator. The wavelength described in this document is suitable for the removal of PWS lesions.

Summary of the Invention

There is, therefore, a need for an improved technique for performing hair removal that facilitates ooptic energy reaching the bulge and base, or root, of hair follicles in one region while minimizing damage to the hair. epidermis in the region, thereby reducing patient discomfort and the potential adverse side effects of treatment.

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The present invention provides an apparatus for the simultaneous removal of a plurality of hairs from a region of the skin, each hair being in a follicle extending into the skin from one surface, the apparatus comprising: an applicator comprising a tailored surface to be in contact with the surface of the skin in a region of the skin from which the hair is to be removed; a source of optical radiation; and an optical path from the source of optical radiation to said surface of said applicator, the path of which is substantially transparent to ooptic radiation at a selected wavelength, the optic radiation being passed through said surface of said applicator to said region of the skin, characterized in that said radiation has a wavelength between 680 nm and 1200 nm, preferably between 680 nm and 900 nm, and a fluence of between 10 J / cm² and 200 J / cm², and because the duration of radiation in said skin region is 2 ms to 200 ms.

The use of the apparatus involves placing the applicator in contact with the surface of the skin in the region of the skin and applying the ooptic radiation through the applicator to the region of the skin for a predetermined time interval. The applicator is preferably pressed against the surface of the skin, reducing the distance from the applicator to the papilla of the hair follicles and facilitating hair destruction.

For preferred embodiments, the applicator is used to cool the skin surface in the skin region to the selected depth and the selected depth is preferably at least equal to the depth of the epidermis layer of the skin (ie say the skin layer closest to the skin surface). Cooling by the applicator can for example be achieved by cooling at least the surface of the applicator in contact with the skin surface, said cooling preferably being achieved both before and during irradiation of the skin.

For preferred embodiments, cooling of the applicator is achieved by passing a cooling fluid through the applicator. Furthermore, it is also preferred that irradiation of the skin surface is not performed until the skin region has substantially cooled to the selected depth. For the most preferred embodiment, cooling is performed both before and during irradiation, and the selected flow and predetermined exposure time (i.e., the time interval for irradiation) are selected such that there is at most one mononymous heating of the skin in the skin region to the selected depth, while there is sufficient heating of the hairs and follicles below the selected depth to at least damage the hairs and follicles without causing significant damage to the tissue surrounding the follicles.

The applicator is preferably also designed to converge the applied optical radiation to the skin region, thus further facilitating irradiation of the follicle papillae. For preferred embodiments, the applicator also has a convex surface in contact with the skin surface, applying substantially uniform pressure thereto to deform the underlying skin surface. For alternative embodiments, the applicator is designed to form a skin fold in the skin region and to apply optic radiation to two substantially opposite sides of the fold. For example, the applicator may have a groove formed on the surface thereof in contact with the surface of the skin, with at least a portion of the skin region being introduced into the groove and ooptic radiation being applied to it. the skin region from at least two opposite sides of the groove.

It is also desirable that a substantial refractive ondx fit be maintained between the applicator and the skin surface in said skin region. Such a refractive ondyx adaptation may be provided by a layer of refractive ondx adaptation substance between the applicator and the skin surface in a region of the skin and / or by the applicator forming a material that at least stops the surface of contact with the skin. The region of the skin has a refractive onyx that substantially adapts that of the skin surface.

To facilitate hair removal, hairs in the skin region can be shaved prior to irradiation. However, it may be preferable to pluck the hairs in the skin region prior to irradiation. When the hairs are depilated, the destruction of the follicles can be facilitated by filling the follicles since the hairs have been depilated with a substance that preferentially absorbs optic radiation at the selected wavelength that is used for irradiation (i.e. a chromophore). In addition, where only temporary hair removal is desired, this can be achieved over a period of up to several weeks, relatively painlessly, by applying the chromophore to the aereal, which has preferably been previously shaved, whose chromophore migrates within the hair follicles to a depth of a few millimeters, approximately to the depth of the sebaceous glandula. Low level irradiation applied through the applicator to the skin region then resulted in the destruction of the hair without destroying the follicle.

ES 2 179 937 T3

An applicator suitable for use in the practice of hair removal in accordance with the foregoing may include the inlet through which optical radiation is applied to the applicator, a surface configured to contact the surface of the skin in the region of the skin, an aoptic path from the entrance to the surface, the path of which is substantially transparent to oaptic radiation at the selected wavelength, an element in the aoptic pathway to converge the oaptic radiation as it leaves the applicator across the surface and some means to cool the surface to a temperature below that of the skin region. As previously noted, the surface it is preferably formed of a material having a refractive index that substantially matches, but is not less than, the refractive index of the skin surface in the region of the skin. For preferred embodiments, the element for converging the oaptic radiation is a lens and the means for cooling is a channel near the surface through which the cooling water is passed. For one embodiment, the surface of the applicator in contact with the skin has a convex configuration while for an alternative embodiment the surface has a groove formed within, with the oaptic path leading to at least two opposite sides of the groove, and the applicator includes means for introducing at least a portion of the skin region into the slot, this introducing means preferably includes a vacuum applicator element.

Brief Description of Drawings

The invention will be further described, by way of example, with reference to the drawings, in which:

Figure 1 is a perspective view of a laser-based hair removal device according to the invention.

Figures 2A and 2B are cross-sectional views of a unit of an applicator or irradiation unit suitable for use with a hair removal device of this invention, the applicator receiving, respectively, light from an oaptic fiber or optic fiber bundle. , and from a mirror set.

Figures 3A, 3B, and 3C are, respectively, an extended cross-sectional view of the contact device of the irradiation unit in direct contact with a region of the skin in contact with the hair, a cross-sectional view showing shows the backward scattered oaptic fields in the interface device / epidermis region, and a cross-sectional view showing tathermic transport in the interfacial region.

Figure 4 is a graph showing the oacetic absorption spectrum of melanin, hemoglobin, oxygenated hemoglobin, and water.

Figures 5A and 5B show, respectively, the time and space profiles and the preferred oaptic field used during the hair removal process.

Figure 6 is a graph of computer generated oaptic intensity as a function of skin depth for different oaptic fields.

Figure 7 is a photograph showing skin regions of a patient three months after he had been treated according to the hair removal method of the invention.

Figures 8A, 8B and 8C are oscilloscope traces showing, following irradiation, the temperature responses as a function of time of, respectively, dry black hair, wet black hair, and the live skin surrounding the black hair sample.

Figure 9 is a graph showing temperature rise as a function of laser pulse energy for dry hair (DH), wet hair (WH), and skin (S) samples from eight different patients.

Figure 10A is a partial cross-sectional view of the applicator of the invention that is used to implement an alternative embodiment of the invention where depilation and filling of the empty follicles with a chromophore are performed prior to irradiation; Y

Figure 10B is a cross-sectional view of an applicator for an alternative embodiment used for hair removal.

ES 2 179 937 T3

Detailed description

Referring to FIG. 1, an exemplary laser hair removal system 10 includes a light source 12, which may, for example, include one or more lasers to generate the irradiation field. The light source 12 can be ooptically coupled to a series of beam manipulating optics 14 which, in turn, can be coupled via a fiber optic cable 16 (or any other fiber optic device) to the irradiation unit or applicator 18. During hair removal therapy, the light source is actuated by a voltage and current supply 19, and delivers a beam or light through optics 14 and optic fibers 16 to irradiation unit or applicator 18. The field is then administered to a region 20 of a patient 22 (placed, for example, on a table 25, a chair, or any other suitable positioning element depending on the location of region 20 on the patient's body) resulting in hair removal from region 20. Once the desired region is treated, the irradiation unit can be easily moved along the patient 22, as indicated by arrows 27, and is used to treat posterior regions. The spatial and temporal properties of the ooptic field determine the effectiveness of the air removal process, and some of these properties can, if desired, be adjusted using a series of controls 24, 26, 28 located on various components of the air removal system. 10. For example, using controls 24 located on the power supply, the optical intensity and the pulse repetition rate of the irradiation field can be controlled by adjusting parameters such as voltage, current, and switching speed for the laser power supply. Other field properties, such as wavelength and pulse duration, can be varied by controls 26 that adjust components (e.g. louvers, mirror or filter positions, shutters, or pulse-forming means) of the light source. 12; however, for preferred embodiments the wavelength should not be adjusted. In a similar manner, controls 28 can be used to adjust the modulation optic 14, resulting in control of properties such as mode quality, beam diameter, and irradiation field coupling within the optic fibers 16. All controls can be adjusted by hand; and the system can also be operated (i.e. the connected laser) by hand or, alternatively, using a foot pedal 30 connected to the system 10.

In alternative embodiments, the light source, coupling optics, and irradiation unit can be included in a single, hand-held device. In this case, the light source is preferably a series of diode lasers directly coupled to the irradiation unit, and is driven by a small external power supply. The compact nature of this type of optical system allows for a more controllable, more maneuverable device, and further obviates the need for fiber optic supply systems.

To effectively destroy the irradiated hair follicles without causing damage to the surrounding skin, the light field supplied by the system 10 and the irradiation unit 18 is designed to maximize the amount of light-induced heating deposited in the hair follicles. , reducing roasted the degree of damage to the surrounding skin. It is preferred, for example, to supply sufficient optic energy to various "target" regions on the hair follicle; radiation administered to these regions results in complete and localized destruction of the follicles.

Before treatment, the region to be treated can be shaved to facilitate irradiation of the follicles. Alternatively, as described later, hairs in the region can be depilated and a chromophore can be applied to region 20, the chromophore of which migrates into the empty follicles. Excess chromophore can then be removed from the skin surface prior to irradiation. Before treatment, an anesthetic can also be injected locally or applied to the surface of the skin and following the treatment, patients can be treated with topical antibiotic ointments.

Mechanical structure

Referring now to Figures 2A and 2B, the applicator or irradiation unit 18 of the hair removal system allows the administration of the irradiation field 38 to the hair follicles 40 located in the region 20. As shown in the figure 2AA, field 38 can be delivered to irradiation unit 18 using a fiber optic cable 16 (or any other fiber optic device) containing one or more fibers or fiber optic bundles. In this case, after the waveguide exits, the field 38 is topically spatially scattered, and is preferably accumulated and roughly collimated using a plano-convex lens 42. Alternatively, as shown in Figure 2B, the field it can be delivered to the irradiation unit using, for example, one or more reflection mirrors 44. This allows field 38 to be approximately collimated before striking lens 42.

ES 2 179 937 T3

Depending on the focal length of the lens 42 and the mode quality of the irradiation field, the field is preferably condensed using, for example, a plano-convex lens as shown in the figure. After passing through this optic, the beam then strikes a contact lens or device 46 that is placed in contact with the skin region 20. The optical and mechanical properties of the contact device 46 are chosen to allow efficient coupling of optical radiation within the skin region (resulting in an administered field 38) and the theoretical properties of the contact device are chosen to allow coupling. efficient heat from the skin region. Once administered, the field is used to irradiate, heat, and then destroy the hair follicles 40. The contact device 46, furthermore, is used to couple light and heat outside the surface skin layer (ie, epidermis) of the irradiated region. This allows the light-absorbing pigment (i.e., melanin) contained within the deep part of the hair follicles to be irradiated and selectively heated, allowing permanent destruction of the follicle, while potentially damaging optical and thoracic energy is simultaneously conducted out. of the underlying skin layers. Therefore, multiple hair follicles can be destroyed, permanently removing hair from the skin region without causing pain or substantial harm to the patient. The destroyed follicles are finally removed by the body.

Both the lenses 42 and the contact device 46 are preferably arranged in a housing 48 containing both the inlet 50 and outlet 52 ports for fluids such as cooling water and pure gas (i.e., nitrogen to prevent condensation on the surface). lens) to flow in and out; Fluids can be used, for example, to cool the contact device 46, which, in turn, cools the surface of the skin. Alternatively, the housing 48 may include an electrically controlled cooler to provide precise control over the temperature of the contact device 46. Preferably, when cooling means are used, the temperature of the surface layer or epidermis of the skin is lowered to or within 4 -15 ° C. Furthermore, in this case, it is preferred that a short period of time (eg, about 1 second) is allowed to elapse before irradiation to ensure that the epidermis is adequately cooled. An outer casing 39, as indicated in FIG. 2B by the striped lone, or a fiber coupling housing, as shown in FIG. 2A, can be used to connect the light supply means to the housing 48.

Referring now to Figure 3A, the contact device 46 is preferably formed within a lens configured to converge the irradiation field, preferably near the base of the hair follicles 40. To converge the light, the contact device must be ooptically transparent in the wavelength of irradiation, and preferably has a biconvex or plane-convex lens configuration, preferably with an f number less than or equal to f / 1.0, and a focal length of between approximately 0.5 and 2 cm. Control over the surface configuration of the contact device allows the converged light field 38 'to simultaneously irradiate several object portions of the hair follicle, resulting in efficient destruction. Topically, each irradiated hair shaft has a diameter of approximately 75 microns, with the entire follicle having a diameter of approximately 200 microns. After passing through the contact device 46, the light field 38 'preferably converges through the epidermis 56 of the skin layer (which has a thickness, for example, of about 0.1 mm) and condenses in the dermis 58 near the papillae 54 of the follicles 40. Because the dermal thickness varies greatly over the body, the papillae may be superficial (as in, for example, the eyelids and scrotum), but for areas of greater interest (for example, the face, armpits, and legs). papillae are located at depths of approximately 4 to 7 mm below the epidermal surface. Located a few tenths of a millimeter below the papillae are the neurovascular bundles 60 that serve the metabolic and other needs of a hair matrix, the region of rapidly growing keratinizing cells, located in the papilla, which produce the stem. 55. The matrix, papilla, and the corresponding vascular bundle, as well as the protrusion near the center of the follicle, represent the follicular objects to be irradiated / destroyed. Preferably, during irradiation of these regions, the field is boosted, keeping the duration of the irradiation pulse short enough that damage is localized to a small region of the dermis (topically within about 0.2 mm) surrounding each follicle according to the principles of selective photothermoolysis. The extent of damage is preferably much less than half the distance between neighboring follicles (topically between 1 and 4 mm); if significantly greater than this, the induced light injury can result in a third degree burn.

In addition to providing a light convergence function, a contact device 46 having a convex shaped surface 62 allows efficient compression of the skin during contact. Compression of the dermis 58 located near the surface 62 of the contact device decreases the distance between this region and the papillae; Depending on the applied force, the distance can be decreased above up to several millimeters. Because the radiation field 38 'is scattered attenuated from

In a corresponding manner during propagation through the dermis, compression of the skin results in bringing more light to the deep portions of the hair follicles for more efficient light-induced heating of the papilla. Furthermore, compression of the dermis by the contact device using a pressure greater than that of the patient's blood pressure forces the light-absorbing blood out of the irradiated region (indicated during treatment by a whitening of the skin in the pressurized region). This reduces the absorption of the optic field, leading to a more efficient light delivery to the follicular target regions. The applied pressure using a contact device having a convex surface results in a relatively uniform displacement of blood from the skin region. A contact device having this configuration is therefore preferred over a flat device, which tends to produce regions that have central portions that are not completely free of blood.

In alternative embodiments, the contact device can be mounted to the housing in a spring loaded mode so that it can be forced against the surface of the skin with an adjustable pressure. Furthermore, in this embodiment, the spring mechanism can be attached to a sensing and reading device so that the exact pressure applied to the skin surface can be accurately monitored and / or controlled.

When forced against the skin, the contact device 46 allows the ooptic radiation to couple in and out of the epidermis. Referring now to Figure 3B, the refractive ondx (nCD) of the contact device 46 should roughly match the (nEP) of the epidermis 56, which is approximately 1.55. Due to the light that travels from one refractive medium (i.e. the contact device) to another (the epidermis) it is reflected at the interface 57 which separates the two regions by an amount related to the square of the difference of the onyx Refractive, the proximal ondyx adaptation allows efficient coupling of the irradiation field within the skin. Therefore, a contact device composed of a material having a refractive ondx close to 1.5 or slightly greater allows the incident irradiation field to subject minimal reflections (indicated in the figure by arrow 64) at the interface of the contact device / epidermis 57. In a similar manner, as indicated in the figure by arrows 66, optic fields within the dermis are scattered back toward the epidermis due to diffuse reflectance. These backscattered fields contribute to unwanted epidermal heating, and are easily coupled out of the skin using the adapted index contact device 46. This allows for a minimization of the induced light damage to the epidermis 56, allowing even irradiation. effective of the target sites of the follicle within the epidermis. In preferred embodiments, to suit substantially ondx, the contact device is preferably formed of a high-density material such as sapphire (nCD = 1.7), solid fused (nCD = 1.5), or crystals or similar optically transparent plastics. To provide a convergent field entering the skin and having the convex configuration of the contact device as shown, it is advantageous to use sapphire, whose slightly higher onyx facilitates the desired field convergence.

Referring now to FIG. 3C, to conduct heat out of the epidermis, it is further preferred that the contact device 46 is composed of a material having a high thermal conductivity (kCD) that is similar to that of skin. This allows efficient heat transfer (indicated in the figure by arrows 68) from the epidermis 56, through the epidermis / contact device interface 57, and into the contact device 46. A high thermal conductivity, furthermore, is necessary to minimize the local heating effects that can occur at interface 57, thus reducing the event of thermally induced damage or injury to the irradiated epidermis. As described later, this is particularly important when the contact device is cooled. Ideally, the thermic properties of the contact device and the time in which the contact device is applied to the skin prior to irradiation begins to allow a reduction to the heating rate near the epidermis, but has little effect on the deposited heating. near the papillae of the hair follicle (shown in the figure as region 70). Materials that have high thermal conductivities include sapphire (KCD = 0.083 cal. Sec.^-1 cm^-2 ° C cm^-1 along the C axis at 30 ^ C), solid molten (KCD = 0.026 cal. sec.^-1 cm^-2 ° C cm^-1 along the C axis at 30 ^ C), as well as other high-density glass or plastics.

Additionally, to improve both the ooptic (i.e., backward-scattered light transmission) and the thermal (i.e., heat conduction) properties at the contact device / epidermis interface 57, it is desirable to apply a topical liquid to the skin. or an emollient, such as a lotion, water, alcohol, or oil, having a refractive onyx that is similar to that of the contact device 46 and the epidermis. For example, the application of an oil that has a refractive onyx between that of the epidermis (n = 1.55) and sapphire (n = 1.7) reduces the optical reflection effects at the interface to the same name,

ES 2 179 937 T3 thus allowing a more efficient transfer of light into the skin region from the contact device and scattered radiation back from the skin region. In addition, a liquid allows more efficient heat transfer by conduction from the skin into the sapphire, thus reducing the degree of damage or injury to the epidermis.

Optical Properties

The temporal and spatial distribution of the intensity for the oáptic field of radiation within the skin ultimately determines the amount of heat deposited within the target regions of the hair follicle; these properties can therefore be selected and / or adjusted to optimize the hair removal process. In particular, properties that affect the hair removal process include pulse energy, pulse duration, repetition rate (i.e. the length of time between subsequent pulses), wavelength, energy, point size of exposure, beam convergence as it enters the skin, and mode geometry (ie, spatial extent and uniformity) of the opal impulse. These characteristics can be selected according to the pigment present in the hair and skin to be irradiated; preferably, each parameter is adjusted so that the temperature at each target site, which is immediately followed by irradiation, rises to between about 80-120 C. Heating of the follicle to this temperature leads to permanent damage and subsequent removal.

Referring now to Figure 4, the wavelength of the irradiation field is chosen to be resonant with the natural pigment (i.e., melanin) present at the target sites (i.e., hair shaft, bulge, matrix, and papilla). The absorption spectra of melanin, water, hemoglobin, and oxyhemoglobin shown in the figure indicate the ability of these compounds to absorb aoptic radiation at different wavelengths; Low absorption indicates that light at the particular wavelength will penetrate deeper into the absorbing media. In general, to selectively heat the target regions, the wavelength of the irradiation field is chosen to match the absorption spectrum of melanin, which basically absorbs light from about 200 to 1200 nm; conversely, the wavelength is out of adjustment to the absorption spectrum of compounds contained in the skin, such as water and hemoglobin. Light having wavelengths between 680 and 1200 nm, a range indicated by arrow 70 in the figure, is effectively absorbed by melanin while relatively transmitted by both hemoglobin and water, and can hitherto be used for heating. selective pigmented hair surrounded by white or slightly tanned skin. In particular, light in the range of 680 to 900 nm or 1000 to 1200 nm is preferred, as this radiation is strongly absorbed by melanin, and will not be absorbed by ribbons present in water and in oxyhemoglobin near 950 nm. . For patients with less melanin present in the hair follicles (for example with reddish brown, or slightly brown hair), shorter wavelengths in this region are preferable due to the higher absorption coefficient of melanin. In addition, other effects of light attenuation in addition to absorption, eg radiation scattering, are also wavelength dependent, and should be considered during selection of the wavelength of the oáptic field. For example, in human skin, light penetration is partially determined by the transport scattering coefficient (μ_s), which decreases at longer wavelengths due to scattering in the dermis. For radiation at 1000 nm, μ., It is approximately 10 cm^-1; the propagation of light within the skin from an index medium generally adapted at this wavelength will therefore reach a maximum intensity at about 1 mm below the surface of the skin.

Sources that generate visible light or near infrared light in the 680-1200 nm range include diode (λ = 800-100 nm), Nd: YAG and Nd: YLF (λ = 1064 and 1053 nm), Ti: Sapphire and infrared dye (λ «700-1000 nm) rubá (λ = 694 nm) and alexandrite lasers (λ = 700 - 850 nm). Rubá, Nd: YAG and diode lasers (particularly series of diode lasers) are preferred as these sources are commercially available, well classified, and can be manufactured on a small scale. Light sources of this type can be incorporated into compact hair removal devices, which, in turn, can be easily manipulated by the operator during hair removal processes.

The duration of the optic impulse can also be controlled to vary the heating of the hair follicle. Referring now to FIG. 5A, the oaptic pulses, indicated by waveforms 74, 74 ', preferably have durations 76, 76' that allow the follicle to heat up for short periods of time. The pulse width is controlled to vary the heat conduction during the optic pulse, and thus the damage to the follicle and its immediate surrounding dermis; Too little damage results in capillary recurrence, while extensive damage can cause scabbing in the irradiated region.

The exact pulse duration is dictated by the diffusion of heating into the skin, a process that

ES 2 179 937 T3 roughly follows the heat diffusion equation in relation to diffusion time t, diffusion distance d, and thermal diffusivity k, as described in Welch, AJ "The thermal response of laserirradiated tissue", IEEE J Quant. Electron. QE-21 (12), 1471-1481 (1984): t = d2 / 4k (k for the human dermis is approximately 1.3 x 10^-3 cm²/ sec). The time required for heat extraction from the epidermis during a laser pulse is approximately 2 ms, and the thoracic time during a typical 200 micrometer hair follicle is approximately 40 ms. For light exposures lasting more than a few hundred milliseconds, too much heat diffusion may occur during the exposure period, resulting in either inefficient destruction of the target regions of the hair follicle, excessive dermal damage, or both. Furthermore, since much melanin (approximately two-thirds) in the epidermis was in the lower portion of the epidermis, heating of the epidermis occurs first in the deeper portions of the epidermis, and it takes some time for this to occur. heating reaches the surface in order to be removed by the contact device 46. Therefore, since this time is at least 2 ms, this is the minimum pulse duration, with a longer time, preferably at least 5 ms, that is suggested to minimize damage to the epidermis. Furthermore, depending on the loaser used, each pulse could be in the form of a single continuous pulse as shown in Figure 5A or in the form of a train of closely spaced pulses of shorter duration, the space between such closely spaced pulses being short moes of 5

For a given fluence, the intensity of the optic field is inversely related to the pulse duration; therefore, when the pulse duration is below Ιϋμβ, large optical intensities can lead to undesirable modes of damage to surrounding skin regions. In addition, short pulses can result in heat-induced "bursts" localized to the follicle causing mechanical damage to the skin. In preferred embodiments, the pulse has a duration or pulse width of about 2-100 ms. During this period of time, the thoracic diffusion takes place over a distance of approximately 0.05 to 0.3 mm; damage limited to approximately this distance results primarily in the destruction of the irradiated hair follicles, with little or no damage to the surrounding skin.

Optical pulses having well defined and adjustable durations can be generated using known techniques. For example, intra-cavity modulation of the light field using electro or acousto-optic Q-switching devices allows the generation of pulses that have time profiles that are topically Gaussian in configuration. The pulses made using these methods are topically too short, however, they have durations in the sub-microsecond interval. The normal mode pulses produced by excitation of the instantaneous bulb of ruby, alexandrite, Ti: sapphire, or Nf: YAG lasers are preferred because these are high energy pulses in the 0.1 -10 ms pulse duration region. . Alternatively, a continuous ooptic field (ie as a function of time) emitted by a laoser can be externally modulated using, for example, a mechanical shutter or electro-optic gate. Modulation using external methods allows the pulse width to be easily varied from a few hundred microseconds to several hundred milliseconds. Pulses generated using external modulation can also have "rectangular wave" time profiles (as shown in Figure 5A) that allow a more uniform optic field to be applied to the region of interest. However, external modulation is not used for currently preferred embodiments.

When using a contact device to deliver the ooptic pulse, a time delay preferably exists between the time the contact device contacts the skin surface and the arrival of the pulse. This allows the entire epidermis layer 56 to cool significantly prior to irradiation, thereby increasing its damage threshold. Pain and damage to the epidermis are thus reduced and further minimized by continuing to cool the contact device 46 during irradiation so that heat continues to be withdrawn from the epidermis. However, heating at lower levels where the destruction of the follicles, and in particular the bulge and papillae thereof, is desired not to be affected by the cooling carried out both before and / or during irradiation.

In addition, the length of time between optical pulses (indicated in FIG. 5A by arrow 78) can be adjusted to control the total amount and average rate of heat deposited within the irradiated region. If respective illumination is required for the destruction of the follicle, this time period is preferably constant and lies between several seconds and a few hundredths of milliseconds. Alternatively, for "single hit" lighting, this time period is selectively controlled by the operator. In this case, an individual laser impact is administered to the region of interest, and then the region is inspected by the operator for damage. Whether

ES 2 179 937 T3 requires more radiation, additional laser impacts can then be delivered to the region. Otherwise, the irradiation unit is moved and used to treat a separate region.

The spatial extent of the ooptic field is chosen to allow multiple hair follicles to be irradiated with a single laser impact. Furthermore, larger spot sizes are preferred since attenuation along the beam axis within the skin due to scattering decreases as the beam radius R increases. Therefore, wide area beams allow more efficient delivery of optic radiation to deep target sites. Referring now to Figure 5B, the width 80 of the spatial profile 82 of the irradiation beam at the skin surface was preferably on the order of, and preferably much greater than, the depth of the object to be irradiated. Most preferably, the beam diameter is at least 8mm. The area of ​​the irradiation field is preferably between about 0.5 and 2 cm², preferably between 0.75 and 1 cm². Since the beam is preferably converged, the spatial profile was condensed as a function of depth before reaching a boundary at a depth defined by ooptic scattering in the dermis. Preferably, as shown in Figure 5B, the intensity through the beam diameter is approximately constant to provide a substantially uniform field of radiation.

Referring now to Figure 6, following illumination, the intensity distribution of the ooptic radiation (i.e., the y-axis in the figure) as a function of skin depth (i.e., the x-axis) is calculated using Monte Carlo-based computer simulations. The distribution is a function of the spatial profile of the beam, the ooptic properties of the medium in contact with the skin. Although the plotted data is based on a computer simulation, and is therefore only an approximation, the x-axis units are estimated to be approximately 500 microns per clock pulse. The first curve 90 shows the properties as a function of skin depth of an ooptic field originating from a small, collimated point of light of 800 nm in air. In this case, the majority of the ooptic intensity is distributed near the surface of the skin (indicated by the “0” point along the x-axis), with the intensity falling rapidly at greater depths. A collimated point originating from the air (curve 92) has an intensity as a function of the depth of the skin distributed more uniformly, although most of the light was still concentrated near the surface of the skin, administering a radiation point collimated, large from a material having a refractive index of 1.5 (curve 94) results in a relatively uniform optic intensity in the first millimeter or so of the skin; at greater depths, this intensity begins to decrease with a relatively slow time constant. Finally, in the preferred embodiment, a large, spatially converging optical field from the refractive material n = 1.5 has an intensity at the skin surface that increases to a maximum after propagating approximately one millimeter within the skin. The intensity was then attenuated as a function of skin depth with a time constant slower than that shown by curve 94. Therefore, such a field can be used to effectively heat the target sites of the follicle, with Reduced heating of the skin on the surface, thus reducing heating damage to the skin.

In the case where the illumination laser generates a beam having a smaller diameter than the preferred values, it may be necessary to extend the beam before administering to the irradiation unit. This can be done with conventional telescopic optics, for example, two-lens systems configured first to extend and then to collimate the emitted beam. Alternatively, as shown in Figure 2A, the irradiation field can be coupled within an optic fiber and then delivered to the irradiation unit. In this case, the emerging field is naturally dispersed due to the waveguiding nature of the fiber, and is then accumulated by a collimating lens. The shift of the lens from the fiber tip allows the irradiation beam profile to be increased to the desired amount.

The fluence of the optic field was varied according to the degree of pigmentation in the patient; Patients with darker hair require lower creep than patients with lighter hair. Preferably, the pulse fluence of the irradiation field for pulses of approximately 1 ms duration is between 30 and 50 J / cm². As described here, in all cases, the creep is adjusted to heat the target regions to the desired temperature of about 80 to 120 C. In addition, the creep level can be increased as the pulse duration is increased to compensate for a less efficient heating of the follicles due to thoracic conduction during long pulses. It may be necessary to increase or decrease the optic fluence to heat the hair follicle to the desired temperature if the wavelength of the irradiating light field is not in the preferred spectral regions (i.e. 680-900 nm or 1000-1200 nm). Additionally, in cases where the laser output is below the desired ooptic fluence, it may be necessary to amplify the individual pulses prior to irradiation to the skin. Optical amplifiers, such as optical cavities

ES 2 179 937 T3 external can be used for this purpose.

Table 1, samples below, lists the preferred parameters of the oaptic fields used for hair removal. The value of each parameter depends on the amount of hair in the region of interest, the degree of pigmentation of the hairs, and the pigmentation of the patient's surrounding skin.

TABLE 1

Optical Field Preferred Parameters

<td>Parameter</td><td>Interval</td><td>Preferred Values</td>

<td>Wavelength</td><td>680-1200 nm</td><td>680-900, 1000-1200 nm</td>

<td>Impulse Duration</td><td>2 ms - 200 ms</td><td>2 - 100 ms</td>

<td>Beam Area</td><td>&gt; 0.5 cm²</td><td>0.75 - 1.0 cm²</td>

<td>Boost Energy</td><td>10 - 200J / cm²</td><td>30 - 50 J / cm²</td>

<td>Coupling (Optical</td><td>External n&gt; 1.4</td><td>N = 1.5 to 1.7</td>

<td>Beam convergence, on skin surface</td><td>Collimated or convergent</td><td>F # 0.5 - 2</td>

The invention will now be further described with reference to the examples that follow.

Examples

In a set of experiments, to show that the temperature rise within irradiated hair is dependent on the degree of pigmentation, fresh human hair and skin samples having different colors were exposed using the hair removal method described here. The light source for all experiments was the rubá laser above. The emitted light was first coupled within an enclosed beam steering device containing several mirrors coated to have high reflectivities at 694 nm, and then supplied to an irradiation unit similar to that shown in Figure 2B. The unit will include a 5 cm flat-convex glass lens attached to the near end of a water-cooled Plexiglas housing. A sapphire contact device configured as a 1 cm focal length lens was disposed at the distal end of the contact device, with the convex side touching the skin to allow compression during exposure as described above. Human skin will be irradiated with an 8mm diameter beam by pressing the cooled contact device (4^or) against the skin region of the patients, and then delivering an individual laser impact. Each impact will typically result in the simultaneous exposure of approximately 10 hairs.

The skin and hair of six adult patients who have hair color ranging from red to black will be irradiated and then observed. In each patient, eight treatment sites were irradiated, each having an area of ​​10 cm.². In order to monitor the destruction of the papilla, sites 1-4 were waxed before exposure to laser light, while sites 5-8 were shaved before exposure. Each site then received an oaptic fluence of both 28 J / cm², 42J / cm², or 57 J / cm². Patients were seen on subsequent examinations one month and three months (and for some patients also one year) after exposure. As seen from the photographs of the exposed regions shown in figure 7 (i.e. regions AC) the regrowth of hair after three months was minimal or non-existent in all cases compared to the region shaved but not treated. (Regioán D), which clearly indicates permanent damage to the hair follicle. In the figure, the AC sites were treated with energy decreasing from the laser. It is clearly evident that air withdrawal is relatively less pronounced in region C, treated with a fluence of 27 J / cm². Region D, the control region, were shaved, on the same day the AC regions were treated. Additionally, the histological specimens obtained from the treated sites revealed that the damage occurred exclusively to the follicle.

ES 2 179 937 T3 of the hair, while the surrounding dermis was essentially replenished. Hair loss was statistically significant for all subjects at the laoser-treated sites compared to the unexposed, shaved control sites. A year later, there was also significant permanent hair loss without any scab formation.

A separate set of experiments allowing the measurement of the temperature characteristics as a function of time of hair and skin samples were conducted using a pulse phototothermal radiometry (PPTR) apparatus. In these experiments, the rubo laser described above was used at lower fluences to provide optic pulses that have an energy that allows the heating, but not destruction, of the follicles. The output from the laser in focus on the human hair and skin samples, to provide a uniform field of excitation. A New England Research, Inc. black body radiation detector containing an amplified liquid nitrogen cooled HgCdTe detector was used for monitoring. The time-dependent characteristics of the sample temperature, and an energy meter by Laoser Gentec, Inc. was used to monitor the radiated pulse. The output of both detectors was amplified with a 0-10 MHz compensated DC-coupled preamplifier, and then relayed to a digital oscilloscope to record and store the data.

Eight patients who had various skin types and hair color ranged from red / blonde to black were studied. In general, the PPTR results indicated that following irradiation at 694 nm, black hair experienced a greater temperature rise than lighter brown hair, and that both of these specimens experienced higher temperature elevations compared to red hair. /blond. Furthermore, following irradiation, type II skin had a lower temperature elevation than type III or type IV skin.

Referring now to Figures 8A-8C, in a particular example using a patient with black hair and white skin, the time traces measured using the PPTR apparatus indicated that 400 ms after irradiation, both the hair experience huomer black and dry, respectively, the temperature rises of about 7 ^ C and 72 C (Figures 8A and 8B) from a base line temperature of 23 ° C, while the surrounding skin (Figure 8C) is subjected to a temperature rise of less than 1 ° C. The difference in the temperature rise and fall characteristics as a function of time of huomeric hair is likewise due to thermic effects (for example, the higher heating capacity of huomeric hair).

Referring now to Figure 9, in all cases, the normalized temperature rises (that is, the ratio of temperature rise to laser impulse energy) in wet and dry hair follicles were higher than significantly than those measured on the skin, indicating selective heating of the follicles using the method of the invention. Table 2 below shows the lists of hair and skin types for each patient in the study. The patient numbers in the table correspond to the patient numbers in Figure 9.

TABLE 2

Patient's Hair and Skin Types

<td>Patient</td><td>Hair</td><td>Type of skin</td>

<td> 1</td><td>Red</td><td>II</td>

<td> 2</td><td>Brown</td><td>III</td>

<td> 3</td><td>Brown</td><td>II</td>

<td> 4</td><td>Gray / black</td><td>III</td>

<td> 5</td><td>Gray / black</td><td>III</td>

<td> 6</td><td>Dark brown</td><td>III</td>

<td> 7</td><td>Gray / black</td><td>II</td>

<td> 8</td><td>Black</td><td>III</td>

ES 2 179 937 T3

Other Forms of Realization

Figure 10A illustrates an alternative embodiment of the invention where region 20 is depilated in addition to being simply shaved prior to treatment in accordance with the teachings of this invention. A solution or suspension of fluid 100 containing a chromophore can then be applied to the skin region 20, with the fluid containing chromophore migrating into the empty follicles and filling the follicles. The "capillary action" of the fluid / chromophore within the follicles is desirable and can be enhanced by providing a low surface tension between the fluid and the skin, for example by using surfactants or solvents. Excess fluid / chromophore can then be removed from the skin surface by washing, cleaning or stripping. During irradiation, the chromophore 100 in the follicle absorbs light and heats up and, along with the heating of the melanin of the follicle itself, results in a significant heating of the follicle that destroys the portions of it, including the bulge and the papilla , required to prevent hair from regrowing. The chromophore therefore must absorb light at the wavelength or wavelengths used for irradiation. Suitable chromophores can include a suspension of carbon particles or a dye such as methylene blue or indocyanine green. Melanin itself in liposomal form can also be used. Since the chromophore is only in the follicles, this technique maximizes the damage to the follicles while minimizing the damage to the surrounding tissue, and for this reason it is a preferred way of practicing the invention, especially for those with colored hair. blonde, red, light brown or other light colored hair. Except for the differences noted above, this embodiment of the invention functions in the same manner as described above for prior embodiments, including cooling of the contact device 46, deformation of the skin in region 20, and irradiation. optics preferred, with the exception that lower frequency may be allowed when chromophores are used.

Figure 10B illustrates another alternative embodiment of the invention where the contact device or appliance 46 'is modified to simultaneously expose both sides of a skin fold. This further increases the relative supply of light to the deep portion of the follicles. In Figure 10B, the contact device has for example an opening or slot 110 in the face of the applicator into which the skin area 20 can be introduced by for example vacuum or aspiration that is applied to the line 112 leading into the top of slot 110, the skin being formed in slot 110 within a fold 113. Radiation can be applied through a fiber optic bundle 114 that is split to apply radiation to lenses 116 on either side of slot 110. Cooling water can flow onto lens surfaces 116 through line 118 . Alternatively, two applicators similar to those shown for example in Figure 2A or 2B may be positioned on opposite sides of a skin fold formed by holding the skin region between them or by other suitable means.

The advantage of folding the skin, as described for the above embodiments, is that the radiation is applied to a relatively thin section of the skin from both sides. Thus, the papilla of a given follicle may be receiving radiation not only from lens 116 on the side of slot 110 where the follicle is located, but also some radiation from lens 116 on opposite sides of the slot. Therefore, the energy applied to the papilla of each follicle is increased without increasing the energy on the surface, facilitating hair removal without pain or injury. By making the slot 110 relatively narrow, pressure is applied to the skin on both sides of the slot, the skin being compressed between the walls of the slot. The advantages of compressing the skin, including removing blood from it and reducing the distance from the skin surface to the papilla, are therefore also achieved by this embodiment of the invention. They held it to form the crease applied to the skin as well.

It may also be possible to use the teachings of this invention during short-term hair removal, the device serving as for example a razor that can provide a shave that lasts perhaps one or two weeks. This is achieved by applying the fluid / chromophore to the region to be "shaved" whose region has preferably been shaved using conventional techniques, but not depilated. In this case, the chromophore can migrate only a few millimeters into the follicle, up to, for example, the level of the sebaceous gland. The excess chromophore can then be removed, and the contact device of this invention used with radiation at a relatively low level to heat the chromophore, and destroy the hair surrounded by it, without substantial damage to both the skin and the follicle.

Furthermore, while cooling water has been shown to be the preferred embodiment for cooling the contact device 46, this is not a limitation on the invention and others may be used.

ES 2 179 937 T3 refrigeration techniques. For example, a low temperature gas or liquid gas can be passed over the contact device for cooling purposes or the contact device can be sufficiently cooled before use so that it can continue to perform the cooling function during irradiation without having a medium. of refrigeration passed on oil. Other refrigeration techniques known in the art can also be used.

Other embodiments are within the scope of the following claims. For example, the contact device cannot be cooled or cooling of the epidermis can be done without an applicator (eg cryogenically).

Therefore, although the invention has been shown and described particularly above with reference to preferred embodiments, the foregoing and other changes in shape and detail may be made herein by a person skilled in the art without departing from the scope of the invention. .