MXPA96000522A - Lapiel surface removal process using the - Google Patents

Abstract

The present invention relates to a process for the removal of superficial epidermal skin cells in human skin. A contaminant that has a high absorption at least a wavelength of light is applied topically to the surface of the skin. Some of the contaminant is forced to infiltrate into spaces between the superficial epidermal cells. The skin section is illuminated with short pulses of laser at the previous wavelength, at least one of the pulses having enough energy to cause some of the particles to explode, releasing the cells of the superficial epidermal skin. In a preferred embodiment, 1 micron graphite particles and a Nd: Y laser are used

Description

SURFACE PROCESSING OF THE SKIN USING LASER This invention is a continuation in part of the application Serial No. 08 / 005,810, filed on January 19, 1993, which was a continuation in part of Serial No. 07 / 783,789, filed on October 29, 1991. , now patent No. 5,226,907, issued July 13, 1993. This invention relates to processes for the removal of the surface layer of human skin, and in particular to such processes using lasers. BACKGROUND OF THE INVENTION The epidermis of human skin comprises several distinctive layers of skin tissue. These tissue layers are shown in block diagram form in Figure 1. The deeper layer is the layer of basal layer, which consists of column cells. The next layer up is the spiny layer, composed of polyhedral cells. Cells pushed up from the spiny layer are flattened and synthesize keratoyalin granules to form the granule stratum layer. As these cells move out, they loosen their nuclei and the keratoyalin granules melt and mix with tonofibrils. This forms a clear layer called the lucid stratum. The cells of the lucid stratum are closely packed. As the cells move up the lucid stratum, they become compressed in many layers of opaque scales. These cells are all flattened remnants of cells that have been completely filled with keratin and have lost all their other internal structure, including nuclei. These scales constitute the outer layer of the epidermis, the stratum corneum. In the lower part of the stratum corneum the cells are completely compacted and adhere to each other strongly, but higher up in the stratum they are loosely packed and eventually form flakes on the surface. For example, in the skin of the cheeks of a face of 50 years, the outer layer of the stratum corneum typically consists of about 15 layers and the layers form flakes at the rate of about one or two layers per month. So naturally a completely new stratum corneum is obtained about twice a year. It is well known that the removal of a few superficial layers of a person's skin will generally result in a skin that looks younger. Many techniques have tried to produce this effect. A faint solar burn will cause slight blistering on the skin after which an outer layer of skin is released. This usually leaves a surface of the skin that looks younger. Similar results can be obtained by abrasion processes such as actually scraping the surface layer with an abrasive material such as a fine sandpaper. Recent attempts have been made to use laser beams to "cook" the surface layer of the skin. This cooking causes the skin to blister, after which the surface layers can be scraped off. Likewise, people have been experimenting with lasers that vaporize the outer surface. These processes of the prior art have some beneficial results, but also provide potential risk to the patient. The slight sunburn presents the risk of long-term underlying damage to the skin. Abrasion processes often result in bleeding and pain and sometimes infection, scabs and slight scars. Laser treatments can result in unwanted pain and burning, and if not properly applied, can result in bleeding and scarring. Summary of the Invention The present invention provides a process for the removal of superficial epidermal skin cells in human skin. A contaminant that has a high absorption of at least one wavelength of light is topically applied to the surface of the skin. Some of the contaminant is forced to infiltrate spaces between the superficial epidermal cells. The skin section is illuminated with short laser pulses at the previous wavelength, with at least one of the pulses having enough energy to cause some of the particles to explode, tearing the superficial epidermal cells. In a preferred embodiment, one Miera graphite particles and one Nd: YAG laser are used. BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the present invention can be described by reference to the drawings. First Embodiment - NdtYAG External Layers of the Epidermis A first preferred embodiment of the present invention can be described by reference to Figs. 2 to 10. Fig. 2 shows a typical cross section of the outer portion (the upper three layers) ) of the human epidermis, such as those in the skin of a cheek of a 50-year-old woman. A representation of a stratum corneum of 15 cells in thickness, and a lucid stratum of 3 cells in thickness, and a granular stratum of 3 cells in thickness are shown.

The total thickness shown is around 100 microns (0.10 mm). The individual cells of the stratum corneum have dimensions of about 10 to 15 microns long, about 5 microns wide and up to 2 microns thick. The cells of the upper layers are stuck together loosely. The spaces between the cells vary from a distance of zero to about 1 or 2 micras. Application of Carbon Solution The first step of this preferred embodiment is to apply topically a layer of carbon solution to the surface of the skin, as shown in Figure 3. The solution comprises graphite powder of 1 miera in oil. baby. The graphite-oil ratio is 20% graphite suspended in 80% oil, by weight. The next step, figure 4, is to force some of the carbon particles down, below the surface of the stratum corneum. It is preferred to do this with an ultrasound unit operating at 0.2 watts per cm2 and 10 MHz. A Hewlett Packard model 3325A pulse generator and a Parametrics transducer model A5525 are used. It has been found that about 5 minutes of ultrasound treatments at this frequency will force a considerable number of carbon particles down through several layers of the stratum corneum. The result of the ultrasound treatment is shown in Figure 5. This distribution of carbon particles has been demonstrated in pig skin. Microscopic examination of pigment epidermal biopsy samples shows the distribution sketched in Figure 5. As shown in Figure 5, two layers of graphite particles are left on the surface and a portion of the particles 6 are distributed by beneath the surface. Pulsed Irradiation The next step is to irradiate the surface of the skin with Nd: YAG laser pulses of about 3 J / cra2 at a wavelength of 1.06 μm. The frequency of the pulses is around 5 Hz but the beam can be scanned so that each place is pulsed at a frequency of about 1 Hz. Graphite is very absorbent of laser energy at the wavelength of 1.06 μm. The latent heat of vaporization is around 104 J / cm3 for solid, cold graphite. In this way, to vaporize a cube of 1 miera (10"12 cm3) approximately 10" 8 J. would be required. The energy that falls on the surface of the particle of 1 miera (1 x 10"8 J / cm2) in a pulse of 3 J / cm2 is 3 x 10"8 J, about three times the energy needed to vaporize the particle. The energy is deposited in a few nanoseconds so there is no time for it to diffuse the heat, therefore exploding violently to be illuminated by the pulse. The effect of a pulse is to vaporize some of the graphite (especially the smallest particles) and break the larger particles of graphite into smaller particles that will fly partly with the high energy. (Subsequent pulses will vaporize the smaller particles created by the previous pulses.) In this way, as a result of the first pulse 7, the first layer of graphite particles is exploited, as shown in 8 in Figure 6. The second layer and the surface of the skin are effectively shielded from the first pulse 7 by the first layer. Some of the carbon particles on the skin have been pushed towards the skin as a result of the shock waves that result from the explosion of the particle in the first layer. The second pulse 9 that comes a second later vaporizes the second layer, as shown at 10 in Figure 7. As before, the additional particles are pushed towards the skin. The skin is quite effectively shielded from pulse 9 by the second layer. But the third pulse 11 interacts with the skin and the carbon particle under the skin. The laser energy at a wavelength of 1.06 μm has an extinction length in human skin of the order of several centimeters, so that very little energy is absorbed from the pulse in the skin tissue but it is absorbed to a large extent in the graphite particles below the surface and at the energy absorption of the third pulse 11 occurs, as shown in FIG. Figure 8, the particles explode violently, tearing dead stratum corneum cells that lie on the exploding cells, all as shown in Figure 8. A few particles can be shielded from pulse 11, but three or four additional pulses 13 will ensure that essentially all the graphite particles are exploited, as shown in Figure 9. Figure 10 shows a cross-sectional view of the surface of the skin after laser irradiation. This drawing is based on biopsy results of treated pig skin, as described above. The skin is lightly washed with a cloth soaked in alcohol and left to dry, resulting in a surface, as shown in Figure 11. The sketch, as shown in Figure 11, can be compared with that in Figure 2. It is seen that around three layers of dead cells in the stratum corneum have been removed. There is no pain, there is no sensation of heat and there is no significant injury to the skin tissue. The Nd: YAG laser energy that was not absorbed in the carbon is dissipated safely in the skin and tissue under the skin. It is preferable to provide a beam of slight divergence to ensure that it spreads after hitting the skin. In the preferred embodiment, the spot size on the surface is 0.5 cm (diameter) and its scattering or diffusion is 10 degrees. Second Form of Preferred Embodiment (With Confinement) A second embodiment is the same as the first embodiment, except that after the carbon-oil suspension is placed on the surface of the skin, a thin, flat piece of glass (such as a microscope glass) is placed firmly on the suspension in order to confine the small explosion and several pulses (preferably around 1 or 2) of the laser beam are applied through the glass onto each section of the suspension. Neither is the ultrasound unit used. The effect is to greatly improve the sub-surface contamination of the upper layers of the epidermis with small particles of graphite. The effect is shown in Figures 12 and 13. One or two pulses are sufficient to produce substantial sub-surface contamination with small carbon particles. After this application, the glass is removed and the process, as explained before for the first embodiment, is continued until it has essentially vaporized all the graphite. In one embodiment, a disposable plastic plate, transparent to the laser beam, can be used instead of the glass plate. The disposable plastic plate can be made part of an articulated arm of the laser or a part of a manual part attached to the articulated arm. This method of forcing matter into the skin tissue can be used to tattoo the skin or to administer drugs through the skin. At least one of the inventors of the present plans to submit a continuation request in part that specifically claims such processes. Third Embodiment - CO, A third embodiment uses a pulse laser of C02. The preferred operating parameters are: wavelength of 10.6 microns, energy density per pulse of 2.5 J / cm2, pulse diameter of 1 cm, pulse duration of 50 ns. Laser beams at 10.6 microns have an extinction length in the skin of about 40 microns because the pulse energy is highly absorbed in water. It is much more highly absorbed in carbon. An extinction length of 1 to 2 microns is estimated. The process is very similar to the one described above. Graphite is applied as before using ultrasound to force some of the carbon that is below the surface. The laser pulses are applied as before and the first two pulses produce similar results, cleaning the two layers of carbon. The third pulse, however, in addition to vaporizing the carbon below the surface of the skin will vaporize a thin surface of tissue. Therefore, the combined effect of (1) mechanical tissue removal due to the explosion of particles below the surface and (2) vaporization of a superficial layer of epidermal tissue of about 2 to 3 microns thick is obtained. Fourth Form of Preferred Embodiment - Liquid Contaminant A hot water solution colored with black food coloring is prepared to one part of dye per fifty parts of water. Apply to the surface of the skin with gauze for 10 minutes. The hot, black water will infiltrate the space in the upper layers of the stratum corneum. (These spaces are normally filled with air.) The gauze is removed and illuminated with about 1 or 2 pulses per site using a C02 laser operating at 10.6 microns and pulses of 50 nanoseconds in duration, with an energy density of 2. J / cm2. These short pulses will deposit enough energy selectively to the colored water solution to instantly vaporize the water, tearing the cells of the upper stratum corneum in the skin section.

An alternative to this embodiment is to add indocyanine green to the hot water instead of the black food coloring. Indocyanine green absorbs infrared light such as that produced by lasers of Nd.-YAG, C02, Alexandrite, Ti: sapphire and Ga: As diode. Since water is an excellent absorber of C02 laser energy, many lotions for water-based skin can be used with the C02 laser. Other Forms of Embodiment Technicians in the field of laser-based medical technology will recognize that many other laser-contaminant combinations can be used to practice this invention. The important attributes of the combinations are: 1. The contaminant must be very highly energy absorbing at the wavelength of the laser beam. 2. The laser beam must be a pulsed beam with very short pulses (pulse duration of less than 1 microsecond). 3. The contaminant must be able to infiltrate the upper layers of the epidermis. 4. The contaminant must explode with enough energy to tear the epidermal cells upon absorption of the laser energy. Applicants have tested acrylic tattoo inks that have been approved by the FDA (Administration of Food and Drugs of the United States) for use in tattoos. The black and blue tattoo inks sold by Spaulding and Rogers seem to work well with a Nd: YAG laser that operates at 1 Hz, 1.06 microns, with an energy density of around 3 J / cm2. It was less successful with other colors. Although the above description contains many specifications, the reader should not interpret these as limitations of the scope of the invention, but as mere exemplifications of their preferred embodiments. Technicians in the field will design many other possible variations that are within their scope. Accordingly, the reader is requested to determine the scope of the invention through the appended claims and their legal equivalents, and not by the examples that have been given.

Claims (14)

1. CLAIMS 1. A process for the removal of superficial epidermal skin cells in human skin, comprising the steps of: a) applying topically to a section of said skin a contaminant having a high absorption at least at a frequency of band of light that penetrates the outer layers of the human epidermis; b) force some of said contaminant to infiltrate spaces between said superficial epidermal skin cells; and c) illuminating said skin section with pulses of said at least one frequency of the light band, at least one of said pulses having sufficient energy to cause at least a portion of said contaminant to explode so as to detach some of said cells from the superficial epidermal skin.
2. 2. A process as in claim 1, wherein said contaminant comprises a large number of carbon particles.
3. 3. A process as in claim 2, wherein an ultrasound device is used to force some of the carbon particles to infiltrate said spaces.
4. 4. A process as in claim 1, wherein at least one forced explosion of a portion of said contaminant is used to force said contaminant to infiltrate said spaces.
5. A process as in claim 1, wherein confinement means, transparent to said at least one frequency of the light band, are placed firmly on said pollutant applied topically for the duration of said forced explosion for the purpose of confining said explosion forced
6. 6. A process as in claim 5, wherein said confining means is a glass plate.
7. 7. A process as in claim 5, wherein the confining means is a plastic plate.
8. 8. A process as in claim 7, wherein said plastic plate is part of an articulated arm.
9. 9. A process as in claim 2, wherein said carbon particles are graphite particles.
10. 10. A process as in claim 9, wherein said graphite particles are mixed with an oil.
11. 11. A process as in claim 10, wherein said oil is baby oil.
12. 12. A process as in claim 2, wherein said carbon particles have a main dimension of about 1 miera.
13. 13. A process as in claim 2, wherein said pulses are pulses of a Nd: YAG laser.
14. 14. A process as in claim 2, wherein said pulses are pulses of a C02 laser.