Apparatus for therapeutic electromagnetic treatment

ES 2 224 151 T3

DESCRIPTION

Apparatus for electromagnetic therapeutic treatment.

The present invention relates globally to the electromagnetic therapeutic treatment technique and more specifically to a method and apparatus for using a spatially extended powered light source such as a flashlamp (electronic flashlamp or tube) for a treatment of this type or effectively focus the light from the flashlamp onto optical fibers for therapeutic treatment or other applications.

This application is a continuation part of an earlier pending United States application serial number 07 / 964,210, filed on October 20, 1992, entitled "Procedure and apparatus for electromagnetic therapeutic treatment" and corresponding to document EP-A -0 565 331. This document describes an apparatus according to the preamble of claim 1.

It is known in the prior art to use electromagnetic radiation in medical applications for therapeutic uses such as treating skin disorders. For example, US Patent No. 4,298,005 to Mutzhas describes a continuous ultraviolet lamp with cosmetic, photobiological and photochemical applications. A treatment based on the use of the ultraviolet part of the spectrum and its photochemical interaction with the skin is described. The power delivered to the skin using the Mutzhas lamp is described as 150 W / m², which does not have a significant effect on skin temperature.

In addition to prior art treatment involving ultraviolet light, lasers have been used for dermatological processes including argon lasers, CO lasers.₂, Nd (Yag) lasers, copper vapor lasers, ruby ​​lasers and lasers with dyes. For example, US Patent No. 4,829,262 to Furumoto describes a process for constructing a dye laser for use in dermatological applications. Skin conditions that can be treated by laser radiation are exterior skin irregularities, such as local differences in pigmentation or skin structure and vascular disorders that are deeper under the skin which cause a variety of skin abnormalities, including port wine stains , telangiectasias, varicose veins on the legs, and stellar and cherry-shaped angiomas. Laser treatments for these skin disorders generally include localized heating of the treatment area by absorption of laser radiation. Warming of the skin changes or corrects the skin disorder and causes the skin abnormalities to disappear in whole or in part.

Certain external disorders, such as pigmented lesions, can also be treated by very rapidly heating the skin to a temperature high enough to evaporate part of the skin. Vascular disorders that are more profound are more typically treated by heating the blood to a temperature high enough to cause it to clot. The disorder will then finally disappear. To control the depth of treatment, a pulsed radiation source is often used. The depth to which heat penetrates the blood vessel is controlled by controlling the pulse width of the radiation source. The absorption and diffusion coefficients of the skin also affect the penetration of heat. These coefficients are a function of the constituents of the skin and the wavelength of the radiation. In particular, the absorption coefficient of light in the epidermis and dermis tends to be a monotonically decreasing and slowly varying function of wavelength. Therefore, the wavelength of the light must be chosen such that the absorption coefficient is optimal for the particular condition of the skin and the size of the vessel being treated.

The effectiveness of lasers for applications such as tattoo removal and age and birthmark removal decreases because lasers are monochromatic. A laser of a given wavelength can be effectively used to treat a first type of skin pigmentation disorder, but, if the specific wavelength of the laser is not effectively absorbed by the skin having a second type of disorder, it will be ineffective for the second type of skin disorder. Furthermore, lasers are generally complicated and expensive to manufacture, large for the amount of power supplied, they are unreliable and difficult to maintain.

The wavelength of light also affects the treatment of the vascular disorder because the blood contained in the surroundings of the vascular disorders varies, and the blood content affects the absorption coefficient of the treatment area. Oxyhemoglobin is the main chromophore that controls the optical properties of blood and has strong absorption bands in the visible area. More particularly, the strongest absorption peak of oxyhemoglobin occurs at 418 nm and has a bandwidth of 60 nm. Two additional absorption peaks with lower absorption coefficients occur at 542 and 577 nm. The total bandwidth of these two peaks is of the order of 100 nm. Additionally, light in the wavelength range of 500 to 600 nm is desirable for the treatment of blood vessel disorders of the skin since it is absorbed by the blood and penetrates through the skin. Wavelengths greater than 1000 nm are also effective as they can penetrate deeper into the skin, heat the surrounding tissue, and, if the pulse width is long enough, help heat the blood vessel by thermal conductivity. Also, longer wavelengths are effective for treating larger diameter vessels because the lower absorption coefficient is offset by the longer path of light in the vessel.

ES 2 224 151 T3

Accordingly, a broadband electromagnetic radiation source covering near ultraviolet rays and the visible part of the spectrum will be desirable for the treatment of vascular and external skin disorders. The general range of wavelengths of the light source will be sufficient to make the treatment optimal for any of a number of applications. Such an electromagnetic radiation therapeutic device must also be capable of providing an optimal wavelength range within the general range for the specific disorder to be treated. The intensity of the light must be sufficient to cause the required thermal effect by raising the temperature of the treatment area to the required temperature. Also, the pulse width must be variable over a range of width sufficient to achieve the optimum penetration depth for each application. Therefore, it will be desirable to provide a light source having a wide range of wavelengths, which can be selected according to the required skin treatment, with a controlled pulse width and a sufficiently high energy density to application to the affected area.

Non-laser pulse light sources such as linear flash lamps provide these benefits. The intensity of the emitted light can be made high enough to achieve the required thermal effects. The pulse width can vary over a wide range so that control of the thermal penetration depth can be achieved. The typical spectrum covers the visible and ultraviolet range and the most effective optical bands for specific applications can be selected, or enhanced, using fluorescent materials. Additionally, non-laser-type light sources such as flash lamps are much simpler and easier to manufacture than lasers, are significantly cheaper for the same power output, and have the potential to be more effective and more reliable. They have a wide spectral range that can be made optimal for a number of specific skin treatment applications. These sources also have a pulse length that can be varied over a wide range that is critical for different types of skin treatments.

In addition to being used for the treatment of skin disorders, lasers have been used for invasive medical procedures such as lithotripsy and the removal of blockages from blood vessels. In invasive procedures of this type the laser light is coupled to optical fibers and delivered through the fiber to the treatment area. In lithotripsy the fiber supplies light from a laser driven to the kidney or gallbladder and the interaction of the light with the stone creates a shock wave that pulverizes the stone. To remove blockages from blood vessels, light is coupled to the blockage by the fiber and disintegrates the blockage. In any event, the limitations of lasers described above with respect to laser skin treatment are present. Accordingly, a device for lithotripsy and filling removal using a flashlamp would be desirable.

To effectively treat an area, the light from the source must be focused on the treatment area. Coupling of pulsed laser light into optical fibers in medicine is very common. The prior art describes the coupling of incoherent isotropic point sources such as CW lamps on small optical fibers. For example, US Patent No. 4,757,431, assigned July 12, 1988 to Cross et al., Describes a procedure for focusing incoherent point sources with small filaments or an arc lamp with an electrode spacing of 2 mm in an area. little. Point (or small) sources are relatively easy to focus without large energy losses due to the small size of the source. Also, US Patent No. 4,022,534, assigned on May 10, 1977 to Kishner describes the light produced by an electronic flash tube and the collection of only a small part of the light emitted by the tube into the optical fiber.

However, the large dimension of an extended source, such as for example a flashlamp, makes it difficult to focus large fractions of its energy on small areas. The coupling in optical fibers is even more difficult since not only a high density of the energy must be achieved, but also the angular distribution of the light must be achieved in such a way that it is trapped in the optical fiber. Therefore, it is desirable to have a system for coupling the output of a high-density, extended, pulsed light source into an optical fiber and to provide a distribution of the light rays with shallow penetration into the tissue.

This object is achieved by an apparatus as defined in claim 1 with preferred embodiments as in the dependent claims.

The therapeutic treatment device comprises a housing and an incoherent light source, suitably a flashlamp, operable to provide a pulsed light output for treatment, disposed in the housing. The housing has a hole and is suitable to be arranged adjacent to the treatment area on the skin. A reflector is mounted within the housing close to the light source and at least one optical filter is mounted close to the hole in the housing. An iris is co-extensively mounted with the hole. Power to the lamp is provided by a circuit that forms a variable pulse width pulse. Therefore, the treatment device provides a pulsed, filtered, density controlled light output through a hole in the housing to the area of ​​the skin for treatment.

Also described is a light energy treatment method comprising the steps of providing a high power pulsed light output from an incoherent light source, which is not the laser type, and directing the pulsed light output to the area. treatment. The pulse width of the light output is controlled and focused so that the energy density of the light is controlled. Also, the light is filtered to control the spectrum of the light.

ES 2 224 151 T3

The coupler comprises an incoherent light source such as a toroidal flashlamp. A reflector is arranged around the incoherent light source and at least one optical fiber or light guide. The fiber has one end arranged inside the reflector. This end collects the light from the circular lamp. In a similar coupling configuration, fibers may be provided, along with a linear to circular fiber transfer unit arranged to receive light from the light source and provide light to the optical fibers. The reflector has an elliptical cross section in a plane parallel to the axis of the linear electronic flash tube and the linear electronic flash tube is positioned at one focus of the ellipse while the linear-to-circular transfer unit is positioned at the other focus. of the ellipse.

For a better understanding of the invention, reference is made to the accompanying drawings, in which like numbers designate elements or corresponding sections therethrough and in which:

Figure 1 is a cross-sectional view of an incoherent pulsed light source skin treatment device;

Figure 2 is a side view of the light source of Figure 1;

Figure 3 is a schematic diagram of a pulse forming a network with a variable pulse width for use in the skin treatment device of Figures 1 and 2;

Figure 4 is a cross-sectional view of a coupler for coupling light from a toroidal electron flash tube into an optical fiber with a tapered edge;

Figure 5 is a side view of a toroidal electronic flash tube;

Figure 6 is a top view of a toroidal electronic flash tube;

Figure 7 shows the geometry for engagement within a conical section;

Figure 8 is a cross-sectional view of a coupler for coupling light from a toroidal electron flash tube into an optical fiber with a flat edge;

Figure 9 is a front sectional view of a coupler for coupling light from a linear flash tube into a circular fiber bundle;

Figure 10 is a side sectional view of the coupler in Figure 9;

Figure 11 is a front view of a coupler for coupling light from a linear electron flash tube into an optical fiber;

Figure 12 is a front view of a coupler for coupling light from a linear electron flash tube into an optical fiber with additives;

Figure 13 is a schematic configuration of the gel skin interface with a transparent plate;

Figure 14 shows an angular distribution of photons penetrating without using a gel;

Figure 15 shows a light guide providing a large angular divergence;

Figure 16 shows a light guide providing a narrow angular divergence;

Figure 17 shows a spectrum produced with a typical 200 A flashlamp;

Figure 18 shows a spectrum produced with a typical 380 A flashlamp; and Figure 19 shows a GTO (Gate Turn-Off thyristor) drive circuit for a flashlamp.

In the various figures, like reference numerals are used to describe like components.

Before explaining in detail at least one embodiment of the invention, it should be understood that the invention is not limited in its application to the details of the construction and arrangement of the components set forth in the following description or illustrated in the drawings. The invention may have other embodiments or be practiced or carried out in various ways. Also, it should be understood that the phraseology and terminology employed herein are for descriptive purposes and should not be construed as limiting.

Referring now to Figures 1 and 2, side and cross-sectional views of a device are depicted.

ES 2 224 151 T3 treating the skin 10 with an incoherent pulsed light source constructed and operable in accordance with the principles of the present invention.

It can be seen that the device 10 includes a housing 12, provided with a hole, a handle 13 (only in figure 2), a light source 14 provided with an outer glass tube 15, an elliptical reflector 16, a set of optical filters 18, an iris 20 and a detector 22 (only in figure 1).

Light source 14, which is mounted in housing 12, may be a typical incoherent light source such as a Model No. L5568 gas-filled linear flashlamp available from ILC. The spectrum of the light emitted by the gas-filled linear flashlamp 14 depends on the current density, the type of glass wrapping material, and the gas mixture used in the tube. For high current densities (e.g. 3000 A / cm², or greater) the spectrum is similar to the radiation spectrum of a black body. Typically, most of the energy is emitted in the wavelength range of 300 to 1000 nm.

To treat a skin (or visible) disorder, the required density of light must be supplied to the skin. This density of light can be achieved with the focusing arrangement shown in Figures 1 and 2. Figure 1 shows a cross-sectional view of reflector 16, also mounted in housing 12. As shown in Figure 1, the cross section of reflector 16 in a plane that is perpendicular to the axis of flashlamp 14 is an ellipse. Linear flashlamp 14 is positioned at one focus of the ellipse and reflector 16 is positioned such that skin treatment area 21 is positioned at the other focus. The arrangement shown is similar to the focusing arrangements used with lasers and effectively couples the light from flashlamp 14 to the skin. This provision, however, should not be considered limiting. Elliptical reflector 16 can be a metallic reflector, typically polished aluminum which is a reflector that can be easily machined and has a very high reflectivity in the visible range and the ultraviolet range of the spectrum can be used. Other bare or coated metals can also be used for this purpose.

Neutral density and optical filters 18 are mounted in housing 12 near the treatment area and can be moved within the beam and outside the beam to control the spectrum and intensity of the light. Typically, 50 to 100 nm bandwidth filters are used, as well as low cut filters in the visible and ultraviolet parts of the spectrum. In some procedures it is desirable to use most of the spectrum, with only the ultraviolet portion being cut off. In other applications, mainly for deeper penetration, it is preferable to use narrower bandwidths. Bandwidth filters and notch filters are readily available commercially.

The glass tube 15 is positioned coaxially with the flashlamp 14 and has fluorescent material arranged therein. The glass tube 15 will typically be used for the treatment of blood vessel coagulation to optimize the energy output of the device 10. The fluorescent material can be chosen to absorb the ultraviolet part of the flashlamp 14 spectrum and generate light in the range of 500 to 650 nm that is optimal for absorption into the blood. Similar materials line the interior walls of commercial fluorescent lamps. A typical material used to generate "warm" white light in fluorescent lamps has a conversion efficiency of 80%, has a peak emission wavelength of 570 nm, and has a bandwidth of 70 nm and is useful for absorption. in the blood. The extinction time of a few milliseconds of these phosphors is consistent with the long pulses required to treat blood vessels.

Other shapes and configurations of flashlamp 14 may be used such as circular, helical, short arc, or multiple linear flash tubes. The reflector 16 may have other designs such as parabolic or circular reflectors. The light source can also be used without a reflector and the required energy and power density can be achieved by positioning the light source 14 close to the treatment area.

The iris 20 is mounted in the housing 12 between the optical filters 18 and the treatment area and controls the length and width of the exposed area, that is, by collimating the output of the flashlamp 14. The length of the flashlamp flashes 14 controls the maximum length that can be displayed. Typically an 8 cm long tube (arc length) will be used and only the center 5 cm of the tube is exposed. The use of the central 5 cm ensures a high degree of uniformity of energy density in the exposed skin area. Therefore, in this embodiment the iris 20 (also called a collimator) will enable the exposure of areas of the skin of a maximum length of 5 cm. The iris 20 may be closed to provide a minimum exposure length of one millimeter. Similarly, the width of the exposed skin area can be controlled in the range of 1 to 5 mm for a 5 mm wide flashlamp. Larger exposed areas can be easily achieved using longer electron flash tubes or multiple tubes, and smaller exposed areas can be obtained with an iris that performs more complete beam collimation. The present invention provides a larger exposure area compared to prior art lasers or point sources and is very effective in clotting blood vessels since interrupting blood flow in a longer section of the vessel is more effective. in coagulation. The greater area exposed simultaneously also reduces the time required for the process.

Detector 22 (Figure 1) is mounted outside of housing 12 and monitors light reflected from the skin. The detector 22 combined with the optical filters 18 and the neutral density filters can be used to achieve a quick estimate of the spectral reflection and absorption coefficients of the skin. This can be done at a low energy density level prior to application of the main treatment pulse. Measurement of the optical properties of the skin prior to the application of the main pulse is helpful in determining the optimal conditions of

ES 2 224 151 T3 treatment. As stated before, the wide spectrum of light emitted by the non-laser type source enables the investigation of the skin over a wide spectral range and the choice of optimal wavelengths for treatment.

In an alternative embodiment, the detector 22, or a second detector system, may be used for a real-time measurement of the temperature of the skin during its exposure to the pulsed light source. This is useful for long pulse skin thermolysis applications where light is absorbed into the epidermis and dermis. When the outer part of the epidermis gets too hot, it can result in permanent skin burns. Therefore, the temperature of the skin should be measured. This can be done by using infrared emission from heated skin, to avoid overexposure.

A typical real-time detector system will measure infrared emission from the skin at two specific wavelengths using two detectors and filters. The relationship between the signals from the two detectors can be used to estimate the instantaneous temperature of the skin. The operation of the pulsed light source can be stopped if a previously selected skin temperature is reached. This measurement is relatively easy as the temperature threshold for driven heating that can cause skin burns is on the order of 50 ° C or more, which can easily be measured using an infrared emission.

The depth of heat penetration depends on the absorption of light and burning of the different layers of the skin and the thermal properties of the skin. Another important parameter is the width of the pulse. For a pulsed light source, the energy of which is absorbed in an infinitesimal thin layer, the depth of heat penetration (d) by thermal conductivity during the pulse can be written as represented in equation 1:

d = 4 [kAt / Cp]^1/2 (Equation 1) where:

k = heat conductivity of the material being illuminated;

At = pulse width of the light pulse;

C = specific heat of the material;

ρ = density of the material.

It is clear from equation 1 that the penetration depth can be controlled by the pulse width of the light source. Hence, a pulse width variation in the range of 10^-5 seconds to 10 'seconds will result in a variation of thermal penetration by a factor of 100.

Accordingly, flashlamp 14 provides a pulse width of from 10 ⁵ seconds to 10 'seconds. For the treatment of vascular disorders in which the objective is coagulation of blood vessels in the skin, the pulse length is chosen to uniformly heat as much of the entire thickness of the vessel as possible to achieve effective coagulation. Typical blood vessels that need to be treated on the skin have thicknesses in the range of 0.5mm. Therefore, the optimal pulse width, taking into account the thermal properties of the blood, is of the order of 100 milliseconds. If shorter pulses are used, heat will still be conducted through the skin to cause clotting, however, the instantaneous temperature of some of the blood in the vessel and surrounding the tissue will be higher than the temperature required for clotting. and it can cause unintentional damage.

For the treatment of external skin disorders in which the objective is to evaporate the skin, a very short pulse width is used to provide very shallow thermal penetration into the skin. For example, a boost of 10^-5 seconds will penetrate (by thermal conductivity) a depth of the order of only 5 microns into the skin. Therefore, only a thin layer of the skin is heated and a very high instantaneous temperature is obtained so that the outer marking of the skin evaporates.

Figure 3 shows a circuit that forms a pulse of variable pulse width comprising a plurality of individual pulses that form networks (PFN - Pulse Forming Networks) that create the variation in the pulse widths of the flashlamp 14. The width full light pulse at half maximum (FWHM - Full Width at Half Maximum) of a flashlamp driven by a single PFN element, with a capacitance C and an inductance L, is approximately equal to:

At ~ 2 [LC]^1/2 (Equation 2)

Lamp 14 can be driven by three different PFNs as depicted in Figure 3. Relay contacts R1 ', R2' and R3 'are used to select between three capacitors C1, C2, and C3 that are charged by supplying power. high voltage. Relays R1, R2 and R3 are used to select the PFN to be connected

ES 2 224 151 T3 to the flashlamp 14. The high voltage switches S1, S2 and S3 are used to discharge the energy stored in the PFN capacitor into the flashlamp 14. In one embodiment, L1, L2 and L3 have values ​​of 100 mH, 1 mH, and 5 mH, respectively, and C1, C2, and C3 have values ​​of 100 mF, 1 mF, and 10 mF, respectively.

In addition to the ability to fire each PFN separately, which generates the basic variability in pulse width, additional variation can be achieved by firing the PFNs sequentially. If, for example, two PFNs having a pulse width of At1 and At2 are fired, so that the second PFN is fired after the first pulse has decayed to half its amplitude, then the pulse width of the effective light of this system operation will be given by the relationship:

At ~ At1 + At2

The load power supply typically has a voltage range of 500 V to 5 kV. The relays therefore must be high voltage relays that can reliably isolate these voltages. The switches S are capable of carrying the current from the flashlamp 14 and isolating the high reverse voltage generated if the PFNs are fired sequentially. Solid state switches, vacuum switches or gas switches can be used for this purpose.

A central power supply (not shown in Figure 3) can be used to keep the flashlamp in a low current driving mode. Other configurations can be used to achieve pulse width variation, such as using a single PFN and a toggle switch, or using a switch with open and close capability.

Typically, for flashlamp 14 operation with a pulse width of 1 to 10 milliseconds, a linear electrical energy density input of 100 to 300 J / cm can be used. An energy density of 30 to 100 J / cm² can be achieved on the skin with a typical flashlamp bore diameter of 5mm. The use of a bandwidth of 500 to 650 nm transmits 20% of the incident energy. Therefore, skin energy densities of 6 to 20 J / cm are achieved.². The incorporation of the fluorescent material will further spread the output radiation in the desired range, enabling the same skin exposure with a lower energy input to the flashlamp 14.

Pulsed laser skin treatment shows that energy densities in the range of 0.5 to 10 J / cm²with pulse widths in the range of 0.5 milliseconds they are generally effective in treating vein-related skin disorders. This range of parameters falls into the operating range of light sources other than the driven laser type, such as linear flash lamps. A few passes of 18 neutral density glass filters can also be used to control the energy density in the skin.

For external disturbances a typical pulse width of 5 milliseconds is used. An electrical energy density input of 20 J / cm into a 5 mm drill flashlamp results in an energy density in the skin of 10 J / cm². Cutting the hard ultraviolet part of the spectrum results in 90% energy transmission, or exposing the skin to an energy density of about 10 J / cm². This energy density is high enough to evaporate outer markings on the skin.

Device 10 may be provided as two units: a physician-held, lightweight unit using handle 13, with the hand-held unit containing flashlamp 14, filters 18, and iris 20 that together control the spectrum and size of the exposed area and detectors that measure reflectivity and instantaneous skin temperature. The power supply, PFN, and electrical controls are contained in a separate box (not shown) that is connected to the hand-held unit via a flexible cable. This allows for simple operation and easy access to areas of the skin that need to be treated.

The invention has therefore been widely described in connection with the treatment of the skin. However, the use of a flashlamp instead of a laser in invasive treatments also provides advantages. Procedures such as lithotripsy and removal of blockages from blood vessels can be carried out with a flashlamp. Such a device can be similar to that shown in Figures 1 and 2 and can use the electronics of Figure 3 to produce the flash. However, to properly couple light to an optical fiber, a series of couplers 40, 80, and 90 are depicted in Figures 4 and 8-10, respectively.

The coupler 40 includes an isotropic high density incoherent pulsed light optical source such as a linear electron beam tube 42, a light reflector 44 which supplies the light energy to an optical fiber 46. The latter has a generally tapered edge in the embodiment of Figure 4. Optical fiber 46 transfers light from collection system 44 to the treatment area. In general, coupler 40 couples pulsed light from an electron flash tube into an optical fiber and has applications in medical, industrial, and domestic areas.

For example, the coupler 40 can be used in the processing of a material for rapid heating or for ablation of a portion of a material that is being processed. Alternatively, the coupler 40 can be used in

ES 2 224 151 T3 a photographic application to provide a flash at the time of taking a picture. The use of such a coupler will allow the flash bulb to be positioned inside the chamber, the light being transmitted to the outside of the chamber using an optical fiber. As one skilled in the art will recognize the coupler 40 allows the use of incoherent light in many applications where coherent or incoherent light has been used in the past.

To provide coupling of light to an optical fiber, the electronic flash tube 42 has a toroidal shape, shown in Figures 5 and 6, and is disposed within the reflector 44. In addition to the toroidal shape, other shapes may be used. , such as a continuous helix, for the electronic flash tube 42. However, a helical tube is more difficult to manufacture than a toroidal tube. Referring now to Figure 6, the electronic flash tube 42 is generally in the shape of a ring, but it is not a perfect ring since the electrodes positioned at the end of the ring have to be connected to the power source. This does not create significant distortion in the circular shape of the electronic flash tube 42, because the connection to the electrodes can be made quite small.

Reflector 44 collects and concentrates light and has a substantially ellipse-shaped cross section, in a plane perpendicular to the minor axis of toroidal electron flash tube 42. The major axis of this ellipse preferably forms a small angle with the major axis of the toroidal lamp 42. The exact value of the angle between the axes of the ellipse and the main axis of the lamp 42 depends on the numerical aperture (NA - Numerical Aperture) of the optical fiber. The toroidal electronic flash tube is positioned such that its minor axis coincides with the focus of the ellipse. The other focus of the ellipse is on the edge of the optical fiber 46. The reflector 44 can be machined from metal with the interior surfaces polished for good reflectivity. Aluminum is a very good reflector with high reflectivity in the visible and ultraviolet wavelengths and can be used for this purpose. The reflector can be machined in one piece and then cut along a surface perpendicular to the main axis of the device. This will facilitate the integration of the toroidal electronic flash tube within the device.

As shown in FIG. 4, the edge of the optical fiber 46 is a cone with a small opening angle, so that the total area of ​​the fiber that is exposed to the light from the electron flash tube is increased. Referring now to Figure 7 the geometry for coupling light within a conical tip is shown. It is assumed here that the light comes from an area of ​​space with an index of refraction of n2 and that the conical section of the fiber (as well as the rest of the core of the fiber) has an index of refraction of n ,.

Not all light rays striking the cone are trapped in it. For light rays propagating in a plane containing the main axis of the system, a condition can be derived for the angle of a ray that will be trapped and absorbed in the fiber. This condition is represented in equation 3.

sen (^_cIiti) = cos (β) - [n,² / n₂² - 1]^{1 /2} sin (β) (equation 3)

The light will be trapped in the conical part of the optical fiber if the angle of incidence μ is greater than ^_cIiti calculated from equation 3. It is only possible to catch it if n,> n₂. If the medium outside the fiber is air, n₂ = 1. Not all light trapped in the conical section of the fiber will also be trapped in the straight part of the fiber if a fiber with a core and a sheath is used. If a fiber with a core and without a sheath is used (the sheath is air), then all the rays captured in the tapered section of the fiber will be trapped in the straight section of the fiber as well.

The configuration shown in figure 4 can also be used with a fluid that fills the volume between the reflector and the optical fiber. A very convenient fluid for this purpose can be water. Water is also very effective in cooling the flashlamp if pulses with high repetition rates are used. The presence of a fluid reduces the losses that are associated with transitions from glass to air, such as the transition between the material that surrounds the flashlamp and air. If a fluid is used in the volume of the reflector, then its refractive index can be chosen such that all rays trapped in the conical section are also trapped in the fiber, even if core / sheath fibers are used.

Another way to configure the fiber in the reflector is to use a fiber with a flat edge. This configuration is depicted in Figure 8 and has a trapping performance very close to the trapping performance of the tapered edge. Many other fiber edge shapes can also be used, such as spherical shapes. The fiber edge configuration also has an effect on the light distribution on the fiber exit side and can be chosen according to the specific application of the device.

The device can be used with a wide variety of optical fibers. Single fibers, or a small number of millimeter or submillimeter diameter fibers, will typically be used in invasive medical applications. In other applications, particularly industrial and domestic applications, it will be preferable to use a fiber having a larger diameter, or a larger bundle of fibers, or a light guide.

According to one embodiment, flexible or rigid light guides are used to couple the light to the treatment area. Flexible light guides made from a bundle of quartz or other glass fibers are heat fused together at the edge of the bundles. The bundles can be circular, rectangular or of any other useful shape. The guides

Rigid light fixtures can be made from quartz, acrylic, glass, or other materials that have a high degree of transparency. The material is generally highly polished on all sides.

A typical cross section of a circular light guide useful for therapeutic treatment is one 1mm to 10mm in diameter. Alternatively, a rectangular light guide provided with typical dimensions from 3mm by 10mm to 30mm by 100mm can be used. In any case the length can be from 20 to 300 mm, or as needed for the specific application.

According to another alternative embodiment, a rectangular light guide is used to more effectively couple the light. The rectangular light guide is chosen to have a shape that matches a rectangular linear flashlamp and that matches the shape of the vessel to be treated.

The light guides described above can be used in another alternative embodiment to control the spectrum of light delivered to the treatment area. Spectral control can be achieved by making the light guide from material that has an absorbent dye dissolved in it. Therefore, the light transmitted by the light guide will have a spectrum determined by the absorbing dye. Alternatively, a discrete filter can be added at one end (preferably at the input end) of the light guide. These filters are absorbent filters. The inventors have found that the absorbent filters produced by Schott, having model numbers OG515, OG550, OG570 and OG590 have suitable characteristics.

Additionally, interference filters or reflective coatings can be used in the light guide by applying an appropriate optical coating to the light guide. Again, a single discrete interference filter can also be used. Additionally, combinations of the various filters described herein, or other filters, can be used. The use of the filters described here can make the use of the filters described above with reference to Figure 1 redundant.

An alternative embodiment involves the use of application specific light guides. In this way, the spectrum of light for various treatments can be easily controlled. According to this alternative, each type of treatment will be carried out with a specific light guide.

The optical properties of the light guide will be chosen to render the particular treatment optical. The wavelengths that follow are particularly useful for the respective treatments:

arteries less than 0.1 mm in diameter - 520-650 nm veins less than 0.1 mm in diameter - 520-700 nm vessels between 0.1 and 1.0 mm in diameter - 550-1000 nm major vessels - 600-1000 nm.

In each case, if the skin is darker (higher pigmentation), longer wavelengths should be used in the lower part of the spectrum.

Multiple spectra can be used for optimal penetration. This can be achieved by lighting with a few pulses, each provided with a different spectrum. For example, the first pulse may have a spectrum that is highly absorbed in the blood. This impulse will coagulate the blood, thereby changing the optical properties of the blood, making it more absorbent in another range of wavelengths (preferably longer). A second pulse will be more efficiently absorbed since the blood absorbs energy from a longer wavelength range. This principle can also be used with lasers or other light sources.

In addition to the characteristics of the light guides described above, in another alternative embodiment a light guide is used to control the angular distribution of the light rays striking the skin. Light striking the skin at large angles (relative to perpendicular) will not penetrate very deeply into the tissue. On the contrary, light that strikes perpendicular to the skin will have a deeper penetration. Therefore, it is desirable to provide a light ray distribution having a relatively wide angular divergence when the treatment requires shallow penetration. Alternatively, a narrower divergence is preferable for the treatment that requires and where deep penetration is desired. Some treatment may require both shallow and deep penetrations.

Figure 15 shows a light guide 115 provided with an exit beam with an angular divergence greater than that of the entry beam. As shown in FIG. 15, a beam 116 enters the light guide 115 at a small angle, relative to the axis of the light guide 115. When the beam 501 exits the light guide 115, the angle relative to axis is much larger. The conical shape of the light guide 115 enhances this divergence.

Figure 16 shows a straight light guide 118 that maintains the angular distribution of the light rays entering it. A beam 119 is shown entering and exiting light guide 118 at the same angle, relative to the axis of coupler 601. Alternate use of both light guides 115 and 118 can achieve penetration.

ES 2 224 151 T3 narrow and deep described above. Alternatively, the user can select the type of coupler according to the depth of penetration required for the treatment being carried out.

Figures 9 and 10 show a coupler 90 for coupling the linear electron flash tube 92 through a linear to circular fiber transfer unit 94 to a fiber bundle 96. A reflector 98 has an elliptical cross section, shown in FIG. Figure 10, in a plane parallel to the axis of the linear electronic flash tube 92 in this embodiment. Tube 92 is positioned at one focus of the ellipse while the linear side of linear beam converter 94 is positioned at the other focus of the ellipse. This configuration is relatively simple to manufacture and commercially available linear to circular converters such as 25-004-4 available from General Fiber Optics can be used. This configuration is particularly useful for larger fiber exposure areas, or for flash lighting purposes.

The energy and power densities achievable with this invention are high enough to achieve the desired effects in surface treatment or medical applications. For the embodiment depicted in Figure 4 the total energy and power densities can be estimated as follows. For a typical toroidal lamp with a hole diameter of 4 mm and a diameter greater than 3.3 cm, a linear electric energy density input of 10 J / cm can be used inside the lamp with a pulse width of 5 seconds. The light output of the lamp will be 5 to 6 J / cm for optimal electrical operating conditions. For the reflector represented in figure 4, 50% of the light generated in the lamp will reach the lower focus. Therefore, a total energy flux at the focus of 25 to 30 J can be obtained. For the embodiments shown in Figure 4 or Figure 8 the total cross-sectional area of ​​the reflector in the focal plane has a section 0.8 cm cross². Energy densities of the order of 30 to 40 J / cm can be achieved² at the fiber entrance with this cross section. This corresponds to power densities of 5 to 10 MW / cm², which are typical power densities used in medical applications or in materials processing.

For longer pulses, higher linear electrical energy densities can be used within the lamp. For a 1 millisecond pulse to the electron flash tube, a linear electrical energy density of 100 J / cm can be used. The corresponding energy density in the focal area will be up to 300 J / cm². Energy densities of this type are very effective in industrial and process cleaning applications as well as in medical applications.

Alternative embodiments for coupling the optical fiber to an extended light source such as a linear flashlamp are depicted in Figures 11 and 12. In the embodiment of Figure 11 an optical fiber 101 is wound around a lamp 102 and a lamp envelope 103. Some of the light that is produced by the light source is coupled within the fiber. If the light rays propagate in the direction in which it is trapped by the fiber then this light will propagate in the fiber and can be used at an exit from fiber 104. A limitation of this configuration is the fact that the greater part of the light emitted by the lamp 103 travels in a direction perpendicular to the surface of the lamp 103 and cannot be trapped in the fiber 101.

The embodiment depicted in Figure 12 overcomes this problem. An optical fiber with additives 105 is wound around the lamp 102 and the sheath 103, instead of a fiber without additives like the fiber 101 of Figure 11. The additive is a fluorescent material which is excited by radiation emanating from lamp 102 and radiates light into the fiber. The light is radiated in all directions and the part of it that is within the critical angle of the fiber 105 is trapped and propagated through the fiber and can be used at the exit of the fiber 104. The angle of the light that is trapped in the fiber is the critical angle of the material from which the optical fiber or optical waveguide is made. For a fiber (or optical waveguide) in air this angle is given by sin α = l / n.

Typically for glass and other transparent materials n = 1.5 and α = 41.8 °. This corresponds to an efficiency of trapping greater than 10% of the light emitted by the fluorescent inside the fiber. If a 50% efficiency of the fluorescent process is assumed, it will be found that more than 5% of the light produced by the lamp is trapped and propagated in the fiber. For example, a 4 ”lamp, with a linear electrical energy input of 300 J / inch and a 50% electricity-to-light conversion efficiency, will couple 2.5% of its electrical energy within the fiber. This corresponds, in the case of the 4 ”lamp, to a total light energy of 30 J of light. This embodiment has the additional advantage of transferring the wavelength emitted by the lamp to a wavelength that may be more useful in some of the therapeutic applications or processes mentioned above. Therefore, the fluorescent material with additives in the fiber can be chosen according to an emission wavelength determined by the specific application of the device.

An alternative embodiment includes the use of a gel to couple the light to the skin. This alternative reduces the heating of the outer layer of the skin (the epidermis and the upper layers of the dermis). The gel is preferably a high viscosity water-based gel and is applied to the skin prior to treatment, although other gels that are not necessarily water-based can also be used. A gel having a relatively high heat capacity and thermal conductivity, such as gel from water, is preferable to allow cooling of the outer skin (in particular the epidermis). Transparency is also desirable because during treatment light passes through the clear gel and reaches the skin.

Referring now to Figure 13, a gel 110 is applied to skin 21 prior to treatment. A flat layer of gel is used on top of the skin because irregularities in the top layer of the gel through which light passes can cause

ES 2 224 151 T3 scattering light and reducing its penetration into the skin. In order to achieve this flatness, a flat, transparent, solid piece 111 can be applied on top of the skin. The configuration is represented schematically in Figure 13. The transparent plate can be made of glass or other transparent materials. Both the flashlamp housing and the light guide described above can be placed in direct contact with the transparent plate.

The configuration of Figure 13 has the advantage of reducing scattering of light (represented by arrows 113) entering the skin due to irregularities in the skin surface. Skin has a refractive index that is greater than that of air. As a result, any photon striking the skin air interface is deflected if it does not strike the skin with an angle of incidence of 0 °. Since the surface of the skin is uneven, the angular distribution of the skin increases. This is schematically represented in Figure 14.

The use of gel addresses this problem since the gel can fill in irregular holes that have been created in the skin structure. The transparent plate covering the gel and the gel itself will preferably have a refractive index that is close to that of the skin. This is relatively easy since the refractive index of the skin is of the order of 1.4 in the visible zone and near infrared. Most transparent glasses and plastics have refractive indices that are on the order of 1.5, which is close enough. The refractive index of water is of the order of 1.34 in this range. Gels made from water will have similar refractive indices. The index can be increased by appropriate additives. The plate and gel therefore act as a flat surface for light to fall on. Since the gel and the plate have a refractive index close to that of the skin, there is very little dispersion at the gel-plate and gel-skin interfaces.

The use of a gel has been experimentally successful in treating leg veins and other benign vascular skin lesions. The treatments were carried out with the flashlamp described above. However, in alternative embodiments, an inconsistent font or a different consistent font can be used.

During operation the light is typically applied to the skin in a sequence of three pulses with short delays between pulses. This mode of operation is used to take advantage of the rapid cooling of the superficial thin epidermis (less than 0.1 mm thick) compared to the larger and deeper vessels typical of leg veins. The gel in contact with the skin cools the epidermis during the waiting period between impulses. This cooling significantly reduces damage to the epidermis.

Light is applied to the treated area both in one long pulse and in a sequence of pulses separated by a delay. The length of the delay and the pulse are preferably controlled by the operator to provide sufficient heat to achieve the desired treatment but not sufficient heat to damage the skin.

This concept was verified with large and deep vessels (on the order of 2mm in diameter and 2mm in depth). A thin layer of commercial water-based ultrasound gel (1 to 2 mm thick "Aqua clear" gel manufactured by Parker USA) was applied to the skin. A 1mm thin glass window was used to generate a flat plate of gel. Light from the device passed through the thin glass and gel onto the skin. Care was taken to ensure that there were no air bubbles in the gel. This configuration was tested with photon fluences of 30 to 50 J / cm². Coagulation and cleaning of the vessels was obtained without causing damage to the skin. This is the opposite of what has happened with similar tests in which no gel was used and in which photon fluences of 20 J / cm² with the same impulse structure they burned the skin.

The epidermis is approximately 0.1 mm thick and has a cooling time of approximately 5 milliseconds. Therefore, delays greater than 5 milliseconds are used to avoid burns.

In another alternative embodiment, the spectrum of the light used for treatment is controlled by controlling the voltage and current applied to the flashlamp. As is well known in the art, the spectrum of light produced by a flashlamp is dependent on the voltage and current supplied to the flashlamp. According to this embodiment, the input voltage and current are selected to provide a desired treatment spectrum. The appropriate voltage and current can be determined experimentally for each flashlamp used. For example, a 200 amp flashlamp current produces the spectrum depicted in Figure 17. Similarly, the spectrum of Figure 18 is produced using a 380 amp flashlamp current. The spectrum in Figure 17 shows a significant improvement in the wavelength range of 800-1000 nm. Such a spectrum is particularly useful for the treatment of large vessels.

The different currents and voltages used to control the output spectrum can be obtained using a group or bank of capacitors that can be connected both in series and in parallel as part of the power source for the flashlamp. A series connection will provide a relatively high voltage and current, thereby producing a spectrum that has an energy at a shorter wavelength, such as 500-650 nm. Such a series connection will be more appropriate to generate shorter pulses (1 to 10 milliseconds, for example) useful for treating smaller vessels.

A parallel connection provides a lower voltage and current and thereby produces a spectrum of

ES 2 224 151 T3 output of a longer wavelength, such as 700-1000 nm. Such a spectrum is more appropriate for treating larger vessels and is suitable for producing longer pulses (in the range of 10-50 milliseconds, for example). Selection of series or parallel connections can be made using a relay or sets of relays.

In an alternative embodiment, the pulse that forms the network of Figure 3 is replaced by a GTO 121 drive circuit, such as that shown in Figure 19. The drive circuit of Figure 19 uses a switch that can be connected or disconnect to control the application of power to the flashlamp. While this alternative embodiment will be described with respect to a GTO that is used as the switch, other switches that can be connected and disconnected, such as IGBTs (IGBT - Insulated Gate Bipolar Transistor - Insulated Gate Bipolar Transistor), can also be used. use.

Referring now to Figure 19, the drive circuit 121 includes a high voltage source 122, a capacitor bank C5, an inductor L5, a diode D5, a switch GTO1, a diode D6, a diode DT, a resistor R5 , a capacitor C6, a trigger generator GTO TR1, a resistor R7, a capacitor C7 and a trigger generator for the electronic flash tube TR2. These components are connected to flashlamp 14 and serve to provide pulses of power to flashlamp 14. The duration and timing of the pulses are provided in accordance with the description made herein. Drive 121 operates in the manner described below.

High voltage source 122 is connected across capacitor bank C5 and charges capacitor bank C5 to a voltage suitable for application to flashlamp 14. Capacitor bank C5 may comprise one or more capacitors and may be configured in the manner described above.

Prior to illumination of the flashlamp 14, the electronic flash tube trigger generator TR2 primes the flashlamp 14 and creates a channel of relatively low impedance within it. After the lamp has been primed, capacitor C7 draws current into flashlamp 14, further creating a low impedance channel in flashlamp 14. This provides a pre-discharge that prepares flashlamp 14 for the power pulse. Capacitor C7 provides a small amount of current, relative to capacitor bank C5. Alternatively, the drive circuit 121 may operate in slow mode, in which pre-discharge is not necessary.

After that, the switch GTO1 is connected via a pulse from the trigger generator GTO TR1, completing the circuit between the lamp 14 and the capacitor bank C5. Therefore, the bank of capacitors C5 discharges through the flashlamp 14. An inductor L5 may be provided to control the rise time of the current through the flashlamp 14. The inductor L5 may include a component inherent resistive, not shown.

After a period of time determined by the desired pulse width has passed, the GTO TR1 trigger generator provides a pulse to the GTO1 switch, disconnecting it. A control circuit determines the timing of the firing pulses and provides them according to the desired pulse width and delays.

A snubber circuit is provided, comprising a diode D6, a resistor R5 and a capacitor C6 for the switch GTO1. Diodes D5 and D7 are also provided to protect switch GTO1 from reverse voltages. Resistor R7 is provided in parallel with flashlamp 14 to measure the leakage current of switch GTO1, which in turn can be used to ensure that switch GTO1 is working properly.

One possible addition to drive circuit 121 is to provide an SCR or other switch in parallel with capacitor bank C5. This allows discharge or reset of capacitor bank C5 without connecting switch GTO1. Other modifications can be made, such as providing the circuit with a series trigger, rather than the parallel trigger shown. Another modification is to use the drive circuit with a laser instead of a flashlamp 14.

Proper utilization of pulse widths and lags can help prevent burning of the epidermis. The epidermis has a cooling time of approximately 5 milliseconds, while large vessels have longer cooling times (a 1mm vessel has a cooling time of approximately 300 milliseconds). Therefore, during an impulse of a duration longer than 5 milliseconds the epidermis can cool down but the glass will not. For example, for treating a large vessel (such as one with a diameter of approximately 1mm) a 100 millisecond pulse will allow the skin to cool but will not cool the vessel.

The same effect can be achieved by using pulse trains. This is useful when it is not practical to provide a single long pulse to the flashlamp. The delays between pulses are selected to allow the skin to cool, but are short enough that the glass does not cool. Therefore, larger vessels can be treated with longer delays because they have longer cooling times. Small glasses get cold

ES 2 224 151 T3 quickly and long delays are not effective. However, they also require less energy and can be treated effectively with a single push.

Typical delay times are in the range of 20 milliseconds to 500 milliseconds. More specifically, delays between 100-500 milliseconds are effective for vessels greater than one millimeter in diameter. Delays of between 20-100 milliseconds are effective for vessels between 0.5 and 1 mm in diameter. Delays of between 10-50 milliseconds are effective for vessels between 0.1 and 0.5 mm in diameter. A single pulse having a width in the range of 1 milliseconds to 20 milliseconds is effective for vessels smaller than 0.1 mm in diameter.

Additionally, the delays should be selected according to the pigmentation of the skin. Darker skin absorbs more energy and takes longer to cool down: therefore longer delays are needed. Lighter skins absorb less energy and shorter delays can be accommodated.

Multiple impulses have been found to prevent "purpura" or the bursting of small vessels in or near the skin. The use of pulses to prevent burning and provide cooling will be effective for light provided by lasers or other sources as well.

Another alternative embodiment includes the use of a microprocessor or personal computer to control the flashlamp. The microprocessor can be used to provide the trigger signal timing and prompting functions described above. Additionally, in one embodiment the microprocessor includes a user interface, such as a screen and a keyboard, buttons, mouse, or other input devices. The microprocessors have information stored inside them and help in the selection of treatment parameters.

For example, if the condition to be treated is a type III port wine stain on the skin, the doctor enters that condition into the microprocessor. The microprocessor responds with suggested treatment parameters, such as using a 570nm cutoff filter, a double pulse with a delay of 50 milliseconds, and a fluence of 55 J / cm.². The clinician can alter these suggested parameters, but does not need to refer back to the operating guidelines for the suggested parameters.

The microprocessor or personal computer can also be used to create and store information about the patient in a database. Therefore, information about previous treatments, such as the condition being treated, the treatment parameters, the number of treatments, etc., is stored and can be recalled when the patient is treated again. This helps to provide the appropriate treatment to the patient. Additionally, the database can include photographs of the patient's condition before and after each treatment. Again, this can be memorized and helps in determining which treatments are most successful for a given condition.

In addition to the treatments described above the devices and procedures described herein can be used to treat other conditions. For example, psoriasis and warts have been treated successfully. Similarly, it can be effective for rejuvenation (wrinkle treatment). The inventor further contemplates the use of this invention to treat hemorrhoids, throat injuries, and gynecological problems associated with vascular malformations.