US20070073308A1 - Method and apparatus for EMR treatment - Google Patents

Abstract

A method and apparatus are provided for performing a therapeutic treatment on a patient's skin by concentrating applied radiation of at least one selected wavelength at a plurality of selected, three-dimensionally located, treatment portions, which treatment portions are within non-treatment portions. The ratio of treatment portions to the total volume may vary from 0.1% to 90%, but is preferably less than 50%. Various techniques, including wavelength, may be utilized to control the depth to which radiation is concentrated and suitable optical systems may be provided to concentrate applied radiation in parallel or in series for selected combinations of one or more treatment portions.

Description

RELATED APPLICATIONS
• The present application is a continuation of U.S. patent application Ser. No. 11/235,697, filed Sep. 21, 2005, which is a continuation of U.S. patent application Ser. No. 10/033,302 (U.S. Pat. No. 6,997,923) entitled “Method and Apparatus for EMR Treatment,” which was filed on Dec. 27, 2001, and herein incorporated by reference, which, in turn, claims priority from provisional application Ser. No. 60/258,855 filed Dec. 28, 2000. All content disclosed in these applications is hereby incorporated by reference in its entirety.
FIELD OF THE INVENTION
• This invention relates to methods and apparatus for using electromagnetic radiation (EMR) for various therapeutic treatments and more particularly to methods and apparatus for dermatological treatment by use of spatially confined and concentrated EMR to create areas of treatment or damage substantially surrounded by areas of sparing.
BACKGROUND OF THE INVENTION
• Various forms of electromagnetic radiation, particularly optical radiation, both coherent and non-coherent, have been utilized for many years for a variety of medical treatments, and in particular for dermatology treatments. Such treatments include, but are by no means limited to, removal of unwanted hair, skin rejuvenation, removal of vascular lesions, acne treatment, treatment of cellulite, pigmented lesions and psoriasis, tattoo removal, treatment of skin and other cancers, etc. Most of these treatments have involved in one way or another the use of a process known as selective photothermolysis (See for example Anderson R R, Parrish J., Selective photothermolysis: Precise microsurgery by selective absorption of the pulsed radiation. Science 1983; 220: 524-526), this process involving irradiating a target area to be treated with radiation at a wavelength preferentially absorbed by a chromophore, either a natural chromophore or artificially introduced chromophore, in the target area, the heating of the chromophore either directly or indirectly effecting the desired treatment.
• While these techniques are useful for many of the indicated applications, these techniques have a number of significant limitations. First, treatments which are performed over a relatively large area, such as skin rejuvenation and hair removal, particularly skin rejuvenation, can cause varying degrees of skin damage over a substantial treatment area. In particular, such treatments can sometimes result in a detachment of skin layers. These relatively large areas of skin damage can frequently take several weeks or more to heal, and follow-up treatments can normally not be performed during this period. It would be preferable if these procedures could be performed in a manner which would result in smaller, spaced areas of damage which heal more quickly, this enhancing both patient comfort and the ability to more quickly perform follow-up treatments. Further, many treatments, such as for example hair removal and wrinkle removal, only require that the treatment be performed in small portions or regions of a much larger treatment area; however, current techniques of treatment generally require that the treatment be performed over the entire treatment area rather than in only the selected regions of the treatment area requiring treatment.
• Another potential problem is the need for a chromophore in the target area which selectively absorbs the applied radiation to generate the heat required for treatment. First, to the extent the regions above the treatment area contain a chromophore which preferentially absorbs or otherwise absorbs the applied radiation, such chromophores are also heated, and care must be exercised in any treatment to assure that such heating does not result in epidermal or dermal damage. Various forms of cooling of such overlying regions, sometimes aggressive cooling, are frequently required to permit such treatments to be performed without damage to the overlying skin. For example, for hair removal or other treatments where melanin is targeted, heating of melanin in the epidermis, particularly at the dermis-epidermis (DE) junction, is a problem. Where the chromophore being targeted is water, substantially all tissue in the treatment area and thereabove will be absorbing the radiation and will be heated, making controlled treatment of a selected body component difficult, and increasing the likelihood of unwanted peripheral damaged.
• Another problem with selective photothermolysis is that the wavelength selected for the radiation is generally dictated by the absorption characteristics of the chromophore utilized. However, such wavelengths may not be optimal for other purposes. For example, skin is a scattering medium, but such scattering is far more pronounced at some wavelengths than at others. Unfortunately, wavelengths preferentially absorbed by for example melanin, a frequently used chromophore, are also wavelengths at which substantial scattering occurs. This is also true for the wavelengths typically utilized for treating vascular lesions. Photon absorption in skin also varies over the optical wavelength band, wavelengths dictated by selective photothermolysis frequently being wavelengths at which skin is highly absorbent. The fact that wavelengths typically utilized for selective photothernolysis are highly scattered and/or highly absorbed limits the ability to selectively target body components, and in particular, limits the depths at which treatments can be effectively and efficiently performed. Further, the fact that much of the energy applied to a target region is either scattered and does not reach the body component undergoing treatment, or is absorbed in overlying or surrounding tissue to cause undesired and potentially dangerous heating of such tissue, results in optical dermatology treatments being relatively inefficient. This low efficiency for such treatments means that larger and more powerful EMR sources are required in order to achieve a desired therapeutic result and that additional cost and energy must be utilized to mitigate the effects of this undesired heating by surface cooling or other suitable techniques. Heat management for the more powerful EMR source is also a problem, generally requiring expensive and bulky water circulation or other heat management mechanisms. Further, since chromophore concentration in a target (for example melanin in the hair) varies significantly from target to target and from patient to patient, it is difficult to determine optimum, or even proper parameters for effective treatment of a given target using selective photothermolysis. High absorption by certain types of skin, for example dark skinned individuals or people with very tanned skin, often makes certain treatments difficult, or even impossible, to safely perform. A technique which permitted all types and pigmentations of skin to be safely treated, preferably with little or no pain, and preferably using substantially the same parameters, is therefore desirable.
• Still another problem with existing treatment is that the amount of energy which can be applied to the treatment area, even where damage to the epidermis, skin scarring or other damage is not an issue, is frequently limited by pain experienced by the patient. Ideally, EMR dermatology procedures, which are typically for cosmetic purposes, should be painless or substantially painless. While if the procedure is being performed by a physician, pain may be controlled by the use of a local anesthetic, or even by putting the patient to sleep, there are risks in the use of any anesthetic, and the use of needles to administer a local anesthetic is undesirable for cosmetic procedures. It would therefore be preferable if patient pain could be substantially reduced or eliminated without the need for such procedures, while still permitting sufficient radiation to be applied to achieve a desired therapeutic result.
• There are also occasions where microsurgery is required or desired on a patient's skin, particularly near the skin surface, where the area to be treated is of a size in the micron range, for example 10 microns, a size which cannot be treated with a scalpel. Existing EMR devices for performing microsurgery are also not adapted for performing surgery on such small targets. A need therefore exists for improved techniques for performing such fine microsurgery.
• Further, while EMR techniques are available for treating some of the conditions indicated above, such techniques do not currently exist for treating scars, including acne scars, chicken pox scars and the like, for bumps in the skin resulting from scar tissue, for stretch marks, for treating certain parasites, etc.. An effective technique for treating such conditions is therefore needed.
• Still another problem is in the removal of tattoos or pigmented lesions, particularly close to the skin surface, where existing techniques frequently result in blistering and other skin problems. An improved technique which would permit the fading of such tattoos or pigmented lesions and/or the ultimate removal thereof in a gentle enough manner so as to not cause damage to the patient's skin or significant patient discomfort is also desirable. Similar techniques for treating various skin blemishes are also desirable.
• Finally, while techniques currently exist which are relatively effective in treating large vascular lesions, such techniques are not as efficient in treating spider veins and other small veins. Similar inefficiencies exist where radiation is applied over a relatively large area of a patient's skin where treatment is required in only relatively small portions of such area.
• A need therefore exists for an improved method and apparatus for EMR therapeutic treatments, and in particular for optical dermatology treatments, which permit more selective treatment in target areas, and which do not rely on selective photothermolysis so that the wavelengths utilized may be selected so as to be more efficient for delivery of radiation to a desired target volume at a selected depth, and in particular to selected portions of such a target volume, which portions are preferably surrounded by portions which are not treated, and so that proper parameters for treating a given target may be more easily determined.
SUMMARY OF THE INVENTION
• In accordance with the above, this invention provides a method and apparatus for performing a treatment on a volume located at area and depth coordinants of a patient's skin, the method involving providing a radiation source and applying radiation from the source to an optical system which concentrates the radiation to at least one depth within the depth coordinants of the volume and to selected areas within the area coordinants of the volume, the at least one depth and the selected areas defining three-dimensional treatment portions in the volume within untreated portions of the volume. The apparatus has the radiation source and an optical system to which radiation from the source is applied, the optical system concentrating the radiation to at least one depth in the volume and to selected areas of the volume, the at least one depth and the areas defining the three-dimensional treatment portions in the volume within untreated portions of the volume. For both the method and apparatus, the ratio of the treatment portions to the volume may be between 0.1% and 90%, but is preferably between 10% and 50%, and more preferably between 10% and 30%. In each instance, the treatment portions may be cylinders, spheres, ellipsoids, solid rectangles or planes of at least one selected size and thickness. The treatment portions may also be spaced lines of a selected length and thickness. The optical system may either apply radiation to all the treatment portions substantially simultaneously or the optical system may apply radiation to at least selected treatment portions sequentially.
• The patient's skin over at least one treatment portion may also be pre-cooled to a selected temperature for a selected duration, the selected temperature and duration for pre-cooling preferably being sufficient to cool the skin to at least a selected temperature below normal body temperature to at least the at least one depth for the treatment portions. For selected embodiments, the skin is cooled to at least the selected temperature to a depth below the at least one depth for the treatment portions so that the at least one treatment portion is substantially surrounded by cooled skin. The cooling may continue during the applying of radiation, and for this embodiment, the duration of the applying of radiation may be greater than the thermal relaxation time of the treatment portions. The wavelength for the radiation source is preferably selected so as not to be either highly absorbed or scattered in the patient's skin above the volume on which treatment is to be performed. For deeper depth coordinants, the optical system focuses to a selected depth below the at least one depth of the treatment portions in order to achieve concentration at the desired depth coordinant in the patient's skin. A selected condition in the volume on which treatment is being performed and/or the patient's skin above this volume may be detected, the results of the detecting being utilized during the applying of radiation to control the treatment portions to which radiation is concentrated.
• The applied radiation preferably has an output wavelength which is at least in part a function of the at least one depth of the treatment portions. More specifically, the wavelength of the applied radiation may be selected as a function of the applied radiation as follows: depth=0.05 to 0.2 mm, wavelength=400-1880 nm & 2050-2350 nm, with 800-1850 nm & 2100-2300 nm preferred; depth=0.2 to 0.3mm, wavelength=500-1880 nm & 2050-2350 nm, with 800-1850 nm & 2150-2300 nm preferred; depth=0.3 to 0.5 mm, wavelength=600-1380 nm & 1520-1850 nm & 2150-2260 nm, with 900-1300 nm & 1550-1820 nm & 2150-2250 nm preferred; depth=0.5 to 1.0 mm, wavelength=600-1370 nm & 1600-1820 nm, with 900-1250 nm & 1650-1750 nm preferred; depth=1.0 to 2.0 mm, wavelength=670-1350 nm & 1650-1780 nm, with 900-1230 nm preferred; depth=2.0 to 5.0 mm, wavelength=800-1300 nm, with 1050-1220 nm preferred.
• The method and apparatus may also be utilized to treat a variety of medical conditions. Where a vascular lesion at a selected depth is being treated, treatment parameters, including the optical system and the wavelength of the applied radiation are selected so that the at least one depth of the treatment portions are at the depth of the vessel being treated. Similarly, where the treatment is skin remodulation by treatment of collagen or hair removal, treatment parameters, including the optical system and the radiation wavelength are selected so that the at least one depth is the depth of interdermal collagen and the depth of at least one of the bulge and matrix of the hair follicle, respectively. The teachings of this invention may also be used to treat acne, to target and destroy pockets of fat, to treat cellulite, for tattoo removal, for treating pigmented lesions, for treating hypotropic and other scars and other skin blemishes, and for treating various other conditions in the skin.
• The optical system utilized in practicing this invention may include an array of optical elements to at least a plurality of which radiation from the source is simultaneously applied, each of the optical elements concentrating the radiation to a selected portion of the volume. Each of the optical elements may for example focus or concentrate to a line of selected length and thickness, the lines for some of the elements being at a selected angle to the lines of other of the elements. The optical system may alternatively include apparatus for scanning radiation applied to optical concentrating components so as to successively focus radiation to N of the treatment portions at a time, where N≧1. The optical system may instead include adjustable depth optical focusing components, and a positioning mechanism for such optical focusing components which moves the components to focus at successive treatment portions. The apparatus may also include a mechanism which cools the part of the patient's skin at least over the selected area coordinants to a selected temperature, and controls which selectively operate the cooling mechanism to pre-cool this part of the patient's skin for a selected duration before application of radiation and/or during application of radiation. The cooling mechanism and the controls may pre-cool the skin to a temperature and for a duration sufficient to cool the part of the skin to at least a selected temperature below normal body temperature to the at least one depth of the treatment portions or may cool to a depth below the at least one depth of the treatment portions, the treatment portions in the latter case being substantially surrounded by cooled skin. The apparatus may also include a detector for at least one selected condition in the volume and/or in a part of the patient's skin above the volume and the optical system may operate in response to the detector to control the treatment portion of the volume to which radiation is concentrated.
• The invention also includes a method and apparatus for performing a treatment on a volume located at an area and depth coordinant of a patient's skin which includes providing a radiation source and pre-cooling the patient's skin over at least part of the area coordinant of the volume to a selected temperature for a selected duration, the selected temperature and duration being sufficient to cool the skin to a depth below the depth coordinant of the volume; and applying radiation to an optical system which concentrates the radiation to at least one depth coordinant and to selected areas within the area coordinants to define treatment portions in the volume, the treatment portions being less than the total volume and each treatment portion being within untreated portions and being substantially surrounded by cooled skin. More specifically, a mechanism may be provided which cools the patient's skin over the area coordinant to the selected temperature and controls may be provided for selectively operating the cooling mechanism to pre-cool the skin for a selected duration before application of radiation and/or during application of radiation, the mechanism and controls cooling to a temperature and for a duration sufficient to cool the skin to at least a selected temperature below normal body temperature to at least a depth below the depth coordinant of the volume. The cooling of the patient's skin by the cooling mechanism may continue during the step of applying radiation and the duration of radiation application may be greater than the thermal relaxation time of each treatment portion.
• Finally, the invention includes a method and apparatus for performing a therapeutic treatment on a patient's skin by concentrating applied radiation of at least one selected wavelength at a plurality of selected three-dimensionally located treatment portions, which treatment portions are within non-treatment portions.
• The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of various embodiments of the invention as illustrated in the accompanying drawings, the same or related reference numerals being used for common elements in the various figures.
IN THE DRAWINGS
• FIGS. 1-1B are top views of three optical systems involving arrays of optical elements suitable for use in delivering radiation in parallel to a plurality of target portions.
• FIGS. 2-3C are side views of various lens arrays suitable for delivering radiation in parallel to a plurality of target portions.
• FIGS. 4-4C are side views of Fresnel lens arrays suitable for delivering radiation in parallel to a plurality of target portions.
• FIGS. 5-5B are side views of holographic lens arrays suitable for use in delivering radiation in parallel to a plurality of target portions.
• FIGS. 6-6A are side views of gradient lens arrays suitable for use in delivering radiation in parallel to a plurality of target portions.
• FIGS. 7-7B are top views of various matrix arrays of cylindrical lenses, some of which are suitable for providing a line focus for a plurality of target portions.
• FIGS. 8-8C are cross-sectional or side views of one layer of a matrix cylindrical lens system suitable for delivering radiation in parallel to a plurality of target portions.
• FIGS. 9-9B are a perspective view and cross-sectional side views, respectively, of a two layer cylindrical lens array suitable for delivering radiation in parallel to a plurality of target portions.
• FIGS. 10-13 are side views of various optical objective arrays suitable for use in concentrating radiation to one or more target portions.
• FIGS. 14-19 are side views of various deflector systems suitable for use with the arrays ofFIGS. 10-13 to move to successive target portions.
• FIGS. 20 and 21 are side views of two different variable focus optical system suitable for use in practicing the teachings of this invention.
• FIGS. 22A and 22B are semi-schematic perspective and side views respectively of a section of a patient's skin and of equipment positioned thereon for practicing the teachings of this invention.
DETAILED DESCRIPTION
• Referring first toFIGS. 22A and 22B, a portion of a patient'sskin200 is shown, which portion includes anepidermis202 overlying adermis204, the junction of the epidermis and dermis being referred to as the dermis-epidermis (DE)junction206. Also shown is a treatment volume V located at a depth d in the patient's skin and having an area A. Treatment volume V may contain one or more vascular lesions which are to be destroyed or removed, may contain a plurality of hair follicles which are to be either permanently destroyed, or at least be damaged so as to result in temporary hair loss, or which are to be stimulated to cause hair growth, may contain in the area below the DE junction collagen which is to be restructured by various means, for example by being temporarily destroyed to stimulate regrowth, particularly for skin rejuvenation and wrinkle removal, may contain a melanoma to be removed, a vascular lesion, pigmented lesion, port wine stain, psoriasis, scar, or other skin blemish or a tattoo to be removed, or some other bodily component on which optical dermatology procedures are performed.
• Also shown is asystem208 for delivering optical radiation tovolume V. System208 includes anEMR source210, which source may be a coherent light source, such as a solid-state laser, dye laser, diode laser, fiber laser or other coherent light source, or may be an incoherent light source, for example a flash lamp, halogen lamp, light bulb or other incoherent light source used to deliver optical radiation in dermatology procedures. Acoustic, RF or other EMF sources may also be employed in suitable applications. The output fromsource210 is applied to anoptical system212, which is preferably in the form of a deliver head in contact with the surface of the patient's skin as shown inFIG. 22B. Where an acoustic, RF or other non-optical EMR source is used assource210,system212 would be a suitable system for concentrating or focusing such EMR, for example a phased array, and the term “optical system” should be interpreted, where appropriate, to include such system.
• Various embodiments of anoptical system212 are discussed hereinafter and shown in the various figures. Generally,system212 functions to receive radiation fromsource210 and to focus/concentrate such radiation to a focused one ormore beams222 directed to a selected one or more treatment ortarget portions214 of volume V, the focus being both to the depth d and spatially in the area A. The energy of the applied EMR is thus concentrated to deliver more energy to targetportions214. Depending on system parameters,portions214 may be cylinders of selected diameter and thickness, spheres or ellipsoids, and for one embodiment may have a square or rectangular cross-section. The portions of each shape may extend through volume V or may be formed in a single layer or staggered layers thereof.Target portions214 may also be (a) relatively narrow strips which may either extend through volume V, be formed in a single thin layer in volume V or be in staggered layers of the volume; or (b) may be one or more thin layers formed in volume V. As will be discussed in greater detail hereinafter,optical system212 may focus to all or a selected subset ofportions214 simultaneously, may contain some type of optical or mechanical-optical scanner for moving radiation focused to depth d tosuccessive portions214, or may generate an output focused to depth d and be physically moved on the skin surface over volume V, either manually or by a suitable two-dimensional or three-dimensional (including depth) positioning mechanism, to direct radiation to desiredsuccessive portions214. For the two later embodiments, the movement may be directly from portion to portion to be focused on or the movement may be in a standard pattern, for example a grid pattern, with the EMR source being fired only when over a desiredportion214.
• Acooling element215 is also included to cool the surface ofskin200 over treatment volume V. As shown inFIG. 22A and 22B, coolingelement215 acts onoptical system212 to cool the portion of this system in contact with the patient's skin, and thus the portion of the patient's skin in contact with such element. Coolingelement215 may for example be a thermoelectric element, or may be a system for passing water, preferably chilled water, a gas, preferably a chilled gas, and possibly even a cryogenic gas, over such portion of the optical system. Other techniques for cooling the surface of the patient's skin known in the art could also be used. Further, whereoptical system212 is not in contact with the patient's skin, cryogenic spray cooling, gas flow or other non-contact cooling techniques may be utilized. A cooling gel on the skin surface might also be utilized, either in addition to or instead of, one of the cooling techniques indicated above.
• System208 also includes anoptional detector216, which may for example be a CCD camera or other suitable detector for a selected characteristic of the patient's skin. The output fromdetector216 is applied to acontrol218, which is typically a suitably programmed microprocessor, but may be special purpose hardware or a hybrid of hardware and software.Control218 controls both the turning on and turning off ofsource210 and may also control the power profile of the radiation.Control218 is also applied tooptical system212 to for example control focus depth for the optical system and to control the portion orportions214 to which radiation is being focused/concentrated at any given time, for example by controlling scanning by the optical system and/or the beam radiating therefrom. Finally, controls218 are applied to coolingelement215 to control both the skin temperature above the volume V and the cooling duration, both for precooling and during an irradiation.

  TABLE 1
  Depth of damage,	Wavelength range, μm	NA range	Pulse

  μm	broad	preferred	broad	preferred	width range, s

  50-200	400-1880 &	800-1850 &	<3	0.2-1	<2
  	2050-2350	2100-2300
  200-300	500-1880 &	800-1850 &	<3	0.2-1	<10
  	2050-2350	2150-2300
  300-500	600-1380 &	900-1300 &	<2	0.2-1	<60
  	1520-1850 &	1550-1820 &
  	2150-2260	2150-2250
  500-1000	600-1370 &	900-1250 &	<2	0.2-0.6	<120
  	1600-1820	1650-1750
  1000-2000	670-1350 &	900-1230	<1.5	0.2-0.6	<120
  	1650-1780
  2000-5000	800-1300	1050-1220	<1	0.2-0.4	<300

• TABLE 2
  Depth of	Diameter of
  damage,	damage,	Wavelength		Pulse		Focusing
  μm	μm	μm	NA	width, ms	Energy, J	depth, μm

  300	50-100	2.2	0.3-0.5	<10	>0.00015	400-600
  300	50-100	1.7	0.3-0.5	<10	>0.0007	400-600
  300	50-100	1.3	0.3-0.5	<10	>0.003	400-600
  300	50-100	1.54	0.3-0.5	<10	>0.0003	400-600
  300	50-100	1.208	0.4-1	<10	>0.016	400-600
  300	50-200	0.92	0.4-1	<10	>0.15	400-600
  1000	50-200	1.7	0.3-0.4	<100	>0.01	1100-2000
  1000	50-200	1.54	0.4	<100	>0.008	1100-2000
  1000	50-200	1.3	0.4	<100	>0.1	1100-2000
  1000	50-200	1.208	0.4	<100	>0.4	1100-2000

• TABLE 3
  	Diameter
  Depth of	of			Pulse
  damage,	damage,	Wavelength,		width,		Focusing
  μm	μm	μm	NA	ms	Power, W	depth, μm

  500-1000	200-1000	2.2	0.3-0.5	>100	>0.5	600-1500
  500-1000	200-1000	1.7	0.3-0.5	>100	>1.5	600-2000
  500-1000	200-1000	1.208	0.3-0.6	>3000	>1.0	600-2000
  500-1000	400-1200	0.92	0.3-0.6	>3000	>25.0	600-2000
  2000-3500	1000-2000	1.208	0.3-0.4	>10000	>1.5	4000-6000

• In accordance with the teachings of this invention,system208 controls a variety of parameters of the applied radiation. Data in Tables 1-3 were found based on Monte-Carlo modeling of photon propagation in the skin using standard parameters of skin scattering and absorption for different wavelength. These parameters include, but are by no means limited to:
• 1. The shape oftreatment portions214. Each of these portions may be a thin disk as shown, may be an elongated cylinder which may for example extend from a first depth closer toDE junction206 to a second deeper depth or, as will be discussed later in conjunction with various optical systems to be described, may be a line focus, each of the lines having a selected length, width and orientation and adjacent lines being spaced by a selected amount. The orientation of the lines for theportions214 in a given application need not all be the same, and some of the lines may, for example, be at right angles to other lines (see for exampleFIGS. 7A and 7B). Lines can by oriented around a treatment target for greater efficacy. For example the lines can be perpendicular to a vessel or parallel to a wrinkle.Portions214 may also be spherical, ellipsoidal and at least for one embodiment, may be a solid square or rectangle of selected thickness. The shape ofportion214 is dictated by the combined parameters of the focused optical signal applied thereto, with the duration of application and to a lesser extent the wavelength of the signal being significant factors in determining the shape of the targeted portions. For example, it has been found that with a 1720 nm laser operating at roughly 0.5 J to 2 J and having a pulse duration of 0.5 to 2 ms, a generally cylindrically shapedportion214 is obtained. Conversely, with a 1250 nm laser operating in the same energy range and having a pulse duration of 0.5 to 3 seconds, with an average of 1 second, generally spherically-shaped target portions are obtained. The parameters for obtaining a particular portion shape may be determined in a variety of ways, including empirically. By suitable control of wavelength, focusing, spot size at the surface and other parameters, theportions214, regardless of shape, may extend through volume V, may be formed in a single thin layer of volume V or may be staggered so that, for example,adjacent portions214 are in different thin layers of volume V. The pattern of the target portions in volume V may also vary with application. Further,target portions214 may also be (a) relatively narrow stripes which may either extend through volume V, be formed in a single thin layer or be staggered in different thin layers, with for example adjacent stripes being in different layers; or (b) may be one or more thin layers formed in volume V. While all of the prior configurations fortarget portion214 could be formed either serially or in parallel, the last configuration with multiple thin layers in the volume V would probably need to be formed serially. The geometry ofportions214 controls the thermal damage in the treatment portion. Since a sphere provides the greatest gradient, and is thus the most spatially confined, it provides the most localized biological damage, and may therefore be the preferred target shape for applications where this is desirable.
• 2. The size of thetreatment portions214. For a depth of approximately 1 mm into the patient's skin, the minimum diameter of aportion214, or the minimum width of aline214, is estimated to be approximately 100 microns; however, much larger portions, several mm's or more, are possible. For greater depths, the minimum sizes will be greater.
• 3. Center to center spacing betweenportions214. The center to center spacing is determined by a number of factors, including the size ofportions214 and the treatment being performed. Generally, it is desired that the spacing betweenadjacent portions214 be sufficient to protect the patient's skin and facilitate healing of damage thereto, while still permitting the desired therapeutic effect to be achieved. In one application, as little as 4% of the volume V was damaged (i.e. a 4% fill factor); however, the damagedportions214 would typically cover substantially more of treatment volume V. While theoretically, the ratio of the combined volume oftreatment portions214 to the volume V ( also sometimes referred to as the fill factor) could be 0.1% to 90%, a preferred range for fill factor is 10% to 50% for some applications and 10% to 30% for most applications. It is important that there be at least some area of sparing around each of the islands or areas of treatment/damage214 and that this area of sparing be sufficient to permit the skin to recover, such recovery being facilitated by melanosome migration..
• 4. The depth d for the volume V. While it may be difficult to achieve a smallfocal spot214 at a depth much below1 mm in a scattering medium such as skin, focussing at depths of up to 4 mm, and perhaps even more, may be possible so long as a tight focus is not required and alarger portion size214, perhaps several millimeters, is acceptable.
• 5. Focus Depth. While as may be seen from Table 1, depth d for volume V and the focal depth ofoptical system212 are substantially the same when focussing to shallow depths, it is generally necessary in a scattering medium such as skin to focus to a greater depth, sometimes a substantially greater depth, in order to achieve a focus at a deeper depth d. The reason for this is that scattering prevents a tight focus from being achieved and results in the minimum spot size, and thus maximum energy concentration, for the focused beam being at a depth substantially above that at which the beam is focussed. The focus depth can be selected to achieve a minimum spot size at the desired depth d based on the known characteristics of the skin.
• 6. Wavelength. Both scattering and absorption are wavelength dependent. Therefore, while for shallow depths a fairly wide band of wavelengths can be utilized while still achieving a focused beam, the deeper the focus depth, the more scattering and absorption become factors, and the narrower the band of wavelengths available at which a reasonable focus can be achieved. Table 1 indicates preferred wavelength bands for various depths, although acceptable, but less than optimal, results may be possible outside these bands.
• 7. Pulse Width. Normally the pulse width of the applied radiation should be less than the thermal relaxation time (TRT) of each of the targetedportions214, since a longer duration will result in heat migrating beyond the boundaries of these portions. Since theportions214 will generally be relatively small, pulse durations will also be relatively short as indicated in Table 1. However, as depth increases, and the spot sizes thus also increase, maximum pulse width or duration also increase. Again, the values given in Table 1 are maximum values for a given spot size and shorter pulses may be used. Generally, thermal diffusion theory indicates that pulse width T for a spherical island should be τ<500 D²/24 and the pulse width for a cylindrical island with a diameter D is τ<50 D²/16. Further, the pulsewidths can sometimes be longer than the thermal relaxation time of thetarget portion214 if density of the targets is not too high, so that the combined heat from the target areas at any point outside these area is well below the damage threshold for tissue at such point. Also, as will be discussed later, with a suitable cooling regimen, the above limitation may not apply, and pulse durations in excess of the thermal relaxation time for adamage portion214, sometimes substantially in excess of TRT, may be utilized.
• 8. Power. The required power from the radiation source depends on the desired therapeutic effect, increasing with increasing depth and cooling and with decreasing absorption due to wavelength. The power also decreases with increasing pulse width.
• 9. Cooling. Typically cooler215 is activated beforesource210 to precool the patient's skin to a selected temperature below normal skin temperature, for example 0 to 10° C., to a depth of at leastDE junction206, and preferably to depth d to protect theentire skin region220 above volume V. However, in accordance with the teachings of this invention, if precooling extends for a period sufficient for the patient's skin to be cooled to a depth below the volume V, and in particular if cooling continues after the application of radiation begins, then heating will occur only in the radiatedportions214, each of which portions will be surrounded by cooled skin. Therefore, even if the duration of the applied radiation exceeds TRT forportions214, heat from these portions will be contained and thermal damage will not occur beyond these portions. Further, while nerves may be stimulated inportions214, the cooling of these nerves outside ofportions214 will, in addition to permitting tight control of damage volume, also block pain signals from being transmitted to the brain, thus permitting treatments to be effected with greater patient comfort, and in particular permitting radiation doses to be applied to effect a desired treatment which might not otherwise be possible because of the resulting pain experienced by the patient. This cooling regimen is an important feature of the applicants invention.
• 10. Numerical Aperture. Numerical aperture is a function of the angle θ for the focusedradiation beam222 fromoptical device212. It is preferable that this number, and thus the angle θ, be as large as possible so that the energy atportions214 in volume V where radiation is concentrated is substantially greater than that at other points in volume V (and in region220), thereby minimizing damage to tissue inregion220, and in portions of volume V other thanportions214, while still achieving the desired therapeutic effect in theportions214 of volume V. Higher numerical aperture of the beam increases safety of epidermis, but it is limited by scattering and absorption of higher angel optical rays. As can be seen from Table 1, the possible numerical aperture decreases as the focus depth increases.
• Thus, by judicious selection of the various parameters indicated above and others, one or more focused radiation beams222 may be achieved to create islands of treatment/damage214 in a treatment volume V at a selected depth d in the patient's skin. Preferred ranges of parameters for achieving these objectives at various depths are provided in Table 1. Table 2 and Table 3 illustrate ranges of parameters at various depths for short pulses (i.e., pulses of less than 10 ms for superficial small targets and less than 100 ms for deeper depths) and for long pulses respectively. The values in Table 2 assume that deep cooling through volume V as described above is not being provided so that the pulse duration is limited by the thermal relaxation time ofdamage portions214. Thus, at shorter depths, where smaller spot or focus areas can be achieved, for example a spot having a diameter of 50 μm, as assumed in Table 2, pulse widths of less than 10 ms are required and other parameters are selected accordingly. Conversely, for deeper depths, tight focus cannot be achieved because of scattering, resulting in a significantly larger diameter fordamage portions214, and thus a larger thermal relaxation time for these portions. Therefore, substantially longer pulse widths can be provided, permitting required energy to achieve the therapeutic effect to be provided over a longer time interval. This facilitates removal of heat fromregion220, and in particular from theepidermal portion202 thereof and fromDE junction206. It also permits a lowerpeak power source210 to be utilized. From Table 2, 3 it is also noted that the focus depth is indicated as greater than the depth d of thedamage portions214. The reasons for this have been discussed above.
• Whilecontrols218 can be preprogrammed to focus on selectedportions214 in target volume V, another option is to use feedback, either mechanically obtained by use ofdetector216, or obtained by an operator, generally optically, but possibly using other of the operator senses such as touch or hearing, to control theportions214 in volume V which are focused on. Assuming, for example, thatdetector216 is a CCD imaging device, the location of hair follicles, vascular lesions, or other targeted components in volume V can be located andfocused beams222 specifically directed to the locations of such components. Thus, assuming a hair removal treatment,detector216 could locate each hair follicle at the surface above volume V, and then focus abeam222 to each such follicle at a selected depth, for example, a depth of 1 mm where stem cells are located. The beam could also be focused to an extended depth along the follicle, for example, 0.7-3 mm to assure destruction of all elements within the follicle required for permanent or substantially permanent hair removal, for example, destruction of follicle stem cells, without substantially damaging dermal tissue surrounding the follicle or damage to the follicle matrix. This result is most easily achieved if the cooling technique discussed above is utilized, with cooling extending below the treatment volume V so that each follicle being treated is surrounded by cooled dermal tissue.
• Feedback could also be used to track a blood vessel or other vascular structure being treated or to track a wrinkle or wrinkles to be treated by collagen restructuring. Further, whilefocused beams222 can be automatically positioned in response to outputs fromdetector216 bycontrol218, such feedback can also be achieved by the operator manually adjusting the position ofoptical system212 to track and treat hair follicles, vascular structures, wrinkles or the like.
• More specifically, the scanner used could include three low power laser diodes, preferably of different colors, used for detection and one high power laser diode used for treatment. The scanner can, for example, be utilized both to detect the location of the blood vessel and the depth of the blood vessel. One of the three diodes used for detection may be a high power diode which can be operated in either a detection or treatment mode and detection, in some instances, may be performed by only one or two diodes, which diode or diodes may be also used for treatment in some cases. A suitable scanner can be used to move the detectors and/or treatment diode over a selected pattern. However, while galvanic scanners have been used in the past, a contact scanner is required for this application, since the desired focusing of the beam requires contact, something which is not possible with a galvanic scanner. Again, the scanner can be programmed to trace a particular pattern to locate targets, and may be programmed to follow a target once located, for example a vein, or the scan may be manually controlled. Where the scan is following a selected target, for example a blood vessel, irradiation may occur at selected points along the blood vessel. It is generally necessary to coagulate a blood vessel at a selected one or more points along the vessel in order to stop blood flow therein and kill the vessel. It should not be necessary to irradiate the entire vessel in order to effect destruction thereof.
• Where a scanner is being used, the area scanned can be projected on a screen, providing effective magnification, which facilitates either the selection of desired target points in a programmed scan or the performance of a scan along a desired target such as a blood vessel. Multiple detectors, which may be filtered to provide different colors, can be utilized for detecting the depth of a target, for example the blood vessel, so that light can be focused to the appropriate depth for treatment. Thus, scanning can be in three dimensions. Since depth is to some extent controlled by wavelength, a fiber laser, the output wavelength of which is programmable over a limited range, may be utilized to control skin depth both for detection and treatment. In each instance, the treatment may be effected solely by focusing radiation to a selected point, water at the point normally being what is heated, or by the effect of such focusing coupled with selective absorption by the desired target at the wavelength utilized. The chromophor, while typically water, could also be blood or melanin. Further, when treating blood vessels, since there is no need for hemoglobin as a chromophore, the vessel can be compressed during treatment, for example by applying pressure to the vessel. This can permit denaturation and shrinkage of the vessel wall, which can result in a more permanent closure of the vessel and in the potential to permanently close larger vessels. The location and size of the islands of treatment/damage can be adjusted for different size, type and location of vessel. Similarly, for hair removal, since melanin need not be targeted, there is no requirement for high melanin content in the hair shaft or follicle, facilitating the easier treatment of gray and blond hair.
• For port wine stains, wavelength can be in a range of 0.9 to 1.85 μm for water absorption or 0.38 to 1.1 μm for hemoglobin absorption with a fill factor of 10% to 80%, and preferably, 30% to 50%. The light source can be an arc lamp with filtering and masking.
• The teachings of this invention are also particularly adapted for skin rejuvenation treatments by collagen regeneration. In such treatments, since collagen is not itself a chromophor, a chromophor such as water in the tissues or blood in the papillary dermis or below typically absorbs radiation and is heated to heat the adjacent collagen, causing selective damage or destruction thereof which results in collagen regeneration. Perturbing blood vessels in the region can also result in the release of fibroblasts which trigger the generation of new collagen. While such treatments may be made only along the line of a wrinkle or other blemish to be treated, such treatment is typically performed over a relatively large area undergoing treatment. In accordance with the teachings of this invention, such treatments can be more effectively performed by heatingselective portions214, with perhaps a 30% to 50% fill factor, resulting in significant collagen regeneration with less trauma and pain to the patient. Such procedure may be performed over a relatively large area A or, utilizing techniques similar to those discussed above for blood vessels, may be performed by periodically firing a beam when over a wrinkle, the beam being traced in a predetermined pattern and fired only when over selected points on the wrinkle, or being moved to track a wrinkle and periodically fired while thereover. Also, as for other treatments where the teachings of this invention are employed, healing occurs relatively quickly so that a subsequent treatment, to the extent required, might generally be performed within a few weeks of an initial treatment, and certainly in less than a month.
• Typically, a bump in the skin occurs when collagen is heated, the bump resulting from contraction of the collagen. Thus, this technique can be used not only to remove wrinkles but also to remove other skin blemishes such as acne or chicken pox scars or other scars in the skin and may also be utilized for treating cellulite. While the bump may recede after approximately a month, the heating also increases the thickness-to-length ratio of the collagen in the area, thus increasing the collagen thickness, resulting in much of the improvement from skin rejuvenation/blemish removal being reasonably permanent.
• Other skin blemishes treatable by the teachings of this invention include stretch marks, which differ from wrinkles in that these marks are substantially flush with the surface, the collagen shrinkage and regeneration as a result of heating reducing these marks. Hypotropic scarring, the raised scars which occur after surgery or certain wounds, can also be treated by reducing blood flow to the vessels of the scar in much the same way that port wine stains are treated above.
• In addition to hair removal, treatment of vascular lesions, and skin resurfacing, the teachings of this invention can also be used to target and destroy a sebaceous gland or glands, for example to treat acne, to target and destroy pockets of subcutaneous fat, to treat cellulite and to do skin resurfacing on areas where such treatments cannot currently be performed, for example neck and hands, where the damage caused using standard skin resurfacing techniques does not normally heal. The treating of only small islands in such areas should leave sufficient undamaged skin structure for healing to occur. The teachings of this invention may, as indicated above, also be utilized for tattoo removal, for treating pigmented lesions, for treating hypotropic and other scars, stretch marks, acne and chicken pox scars and other skin blemishes and for treating various other conditions which may exist in the patient's body at depths of less than approximate 4 mm, for example, various skin cancers and possibly PFB. For skin tumors, a combination may be used of a feedback system that localizes the position of the tumor and a robotic system that insures complete thermal destruction of the tumor. Psoriasis may be treated in substantially the same way with substantially the same parameters as for port wine stain. The teachings may also be used to treat intredermal parasites such as larva migrans, which can be detected and selectively killed using the teachings of the invention.
• There are three general ways in which the invention may be utilized for tattoo removal. The first is by using a wavelength or wavelengths absorbed by the tattoo ink, preferably with short, high fluence pulses, to break up or destroy the ink in and between cells. The second technique involves destroying the cells containing the ink, targeting either the ink or water in the cells, causing the ink to be released and removed by the body's lymphatic system. Here long pulses in the millisecond to second range, having low power and high energy, would typically be utilized. In a third technique, an ablation laser would be used to drill 1 to 2 mm spots into the tattoo, ablating or vaporizing both cells and tattoo ink in these areas. With a small fill factor, in for example the 10% to 80% range, and preferable the 10% to 30% range, such small damage spots heal well, permitting the tattoo to be progressively lightened and ultimately removed for each of the three treatments. A randomized pattern on each treatment is also preferable to interference of the removal pattern.
• A particular problem for which the teachings of this invention are particularly adapted is the treating of birthmarks or other pigmented lesions in the epidermis. Such lesions are generally difficult to treat without blistering using conventional treatment. By using islands of damage with a fill factor of 1% to 50%, and preferably 10% to 30%, and with a spot size of 100 microns to ½ mm, it is possible to treat such lesions without scarring. Since the treatment in this case is so close to the surface, focusing is not necessary. A similar treatment, with similar fill factor could be used for treating port wine stains or tattoos, but in either of these cases, focusing would be required since the treatment is at a greater depth. In all cases, a first treatment might result in only the lightening of the treated area. Once the treated portion has healed, which generally would occur in a few weeks to a month with an islands of damage treatment, one or more additional treatments can be performed to further lighten the treated area until the lesion, port wine stain, tattoo or the like is removed. In each instance, dead cells resulting from the treatment containing melanosites, ink or the like, would be removed by the body, normally passing through the lymphatic system.
• Thus, a technique has been provided (a) which permits various therapeutic treatments on a patient's body at depths up to approximately 4 mm, (b) which permits only islands of damage in three dimensions to occur, thereby facilitating healing (by permitting continued blood flow and cell proliferation between skin layers and islands of damage214) and reducing patient discomfort, (c) which permits targeting of specific components for treatment without damage to surrounding parts of the patient's body, thereby more efficiently using the applied radiation while also reducing peripheral damage to the patient's body as the result of such treatment (d) which permits treatment of all skin types using substantially the same parameters for a given treatment, thereby simplifying treatment set-up and treatment safety, and (e) which permits the wavelength utilized for treatment to be optimally selected for the depth of treatment, rather than being restricted to a wavelength optimally absorbed by a targeted chromophore. In fact, while the wavelengths selected for the teachings of this invention normally have significant water absorption, one of the criteria in selecting wavelengths is that they are not, particularly for deeper depths, highly absorbed, even by water, so that the radiation can reach desired depths without losing substantial energy/photons to absorption. The concentration of photons/energy attarget portions214 increases energy at these portions more than enough to compensate for reduced absorption at the wavelength utilized. This invention thus provides an entirely new and novel technique for performing such treatments.
• FIGS. 1-21 illustrates various optical components suitable for use inoptical system212. In these figuresFIGS. 1-9B illustrate various systems for delivering radiation in parallel to a plurality oftarget portions214. The arrays of these figures are typically fixed focus arrays for a particular depth d. This depth may be changed either by using a different array having a different focus depth, by selectively changing the position of the array relative to the surface of the patient's skin or to target volume V or by controlling the wavelength(s) of the radiation.FIGS. 10-13 show various optical objective arrays which may be used in conjunction with the scanning or deflector systems ofFIGS. 14-19 to move to successive one or morefocused portions214 within target volume V. Finally,FIGS. 20 and 21 show two different variable focus optical systems which may, for example, be moved mechanically or manually over the patient's skin to illuminatesuccessive portions214 thereon.
• Referring to these figures in greater detail,FIGS. 1, 1A and1B show a focusingelement1 on asubstrate3, the focusing element having a border which is in a hexagonal pattern (FIG. 1), a square pattern (FIG. 1A), and a circular or elliptical pattern (FIG. 1B). Standard optical materials can be used for these elements. While the hexagonal and square patterns ofFIG. 1 andFIG. 1A can completely fill the working area of the focusingelement plate4, this is not true for the element pattern ofFIG. 1B. Radiation fromsource210 would typically be applied simultaneously to all of the focusingelements1; however, the radiation could also be applied sequentially to these elements by use of a suitable scanning mechanism, or could be scanned in one direction, illuminating/irradiating for example four of the elements at a time.
• FIGS. 2 and 2A are cross-sectional views of a microlens system fused in a refractingmaterial8, for example, porous glass. The refractive index for the material oflenses5 must be greater than the refractive index of refractingmaterial8. InFIG. 2,beam11 initially passes throughplanar surface10 of refractingmaterial8 and is then refracted both byprimary surface6 and bysecondary surface7 of eachmicrolens5, resulting in the beam being focused to afocal point12. The process is reversed inFIG. 2A, but the result is the same.
• InFIGS. 2B and 2C, theincident beam11 is refracted by aprimary lens surface6 formed of the refractingmaterial8.Surfaces6 and7 for the various arrays can be either spherical or aspherical.
• InFIGS. 3 and 3A, thelens pieces15 are mounted to a substrate and are in animmersion material16. The refraction index oflens pieces15 are greater than the refraction index ofimmersion material16.Immersion material16 can be in a gas (air), liquid (water, cryogen spray) or a suitable solid Gas and liquid can be used for cooling of the skin. The immersion material is generally at the primary and secondary plane surfaces,13 and14, respectively. InFIG. 3A, theprimary surface6 andsecondary surface7 of eachlens piece15 allows higher quality focusing to be achieved. ForFIGS. 3B and 3C, thelens pieces15 are fixed on a surface of a refractingmaterial8, the embodiment ofFIG. 3C providing a deeper focus than that ofFIG. 3B, or that of any of other arrays shown inFIGS. 3A-3C for a givenlens15. The lens arrays shown inFIGS. 3A-3C are a preferred lens arrays for practicing the teachings of this invention.
• FIGS. 4-4C show Fresnel lens surfaces17 and18 formed on a refractingmaterial8. Changing the profile ofFresnel lens surface17 and18, the relationship between the radius ofcenter17 andring18 of the Fresnel surface, makes it possible to achieve a desired quality of focusing. The arrays ofFIGS. 4B and 4C permit a higher quality focusing to be achieved and are other preferred arrays.Surfaces17 and18 can be either spherical or aspherical.
• InFIGS. 5 and 5A, the focusing of anincident beam11 is achieved by forming a holographic lens19 (i.e., a photographic hologram) on a surface of refractingmaterial8.Holographic lenses19 may be formed on either of the surfaces of refractingmaterial8 as shown inFIGS. 5 and 5A or on both surfaces.FIG. 5B shows that theholographic material20 substituted for the refractingmaterial8 ofFIGS. 5 and 5A. The holographic lens is formed in the volume ofmaterial20.
• InFIGS. 6 and 6A, the focusing elements are formed bygradient lenses22 having primary plane surfaces23 and secondary plane surfaces24. As shown inFIG. 6A, such gradient lenses may be sandwiched between a pair of refractingmaterial plates8 which provide support, protection and possibly cooling for the lenses.
• FIGS. 7, 7A and7B illustrate various matrix arrays ofcylindrical lenses25. The relation of thelengths26 anddiameters27 of thecylindrical lenses25 can vary as shown in the figures. Thecylindrical lens25 ofFIGS. 7A and 7B provide a line focus rather than a spot or circle focus as for the arrays previously shown.
• FIGS. 8-8C are cross-sectional views of one layer of a matrix cylindrical lens system. Theincident beam11 is refracted by cylindrical lenses25 (FIGS. 8 and 8A) or half cylinder lenses29 (FIGS. 8B and 8C) and focus to aline focus28. InFIGS. 8B and 8C, thecylindrical lenses29 are in theimmersion material16. Primary workingoptical surface30 and secondary optical workingsurface31, which may be spherical or aspherical, allowing high quality focusing to be achieved. As shown inFIGS. 7-8C the line focuses for adjacent lenses may be oriented in different directions, the orientations being at right angles to each other for certain of the lenses in these figures.
• InFIGS. 9, 9A and9B, a matrix of focal spots is achieved by passingincident beam11 through two layers ofcylindrical lenses32 and35.FIGS. 9A and 9B are cross-sections looking in two orthogonal directions at the array shown inFIG. 9. By changing the focal distance ofprimary layer lens32, having asurface33, andsecondary lens35, having asurface36, it is possible to achieve a rectangular focal spot of a desired size.Primary layer lens32 andsecondary layer lens35 are mounted inimmersion material16.Lenses32 and35 may be standard optical fibers or may be replaced by cylindrical lenses which may be spherical or aspherical.Surfaces34 and37 can be of optical quality to minimize edge losses.
• FIG. 10 shows a onelens objective43 with abeam splitter38. Thebeam11 incident onangle beam splitter38 divides and then passes through the refractingsurfaces41 and42 oflens43 to focus atcentral point39 and off-center point40.Surfaces41 and42 can be spherical and/or aspherical.Plate54 having opticalplanar surfaces53 and55 permits a fixed distance to be achieved betweenoptical surface55 and focusingpoints39,40.Angle beam splitter38 can act as an optical grating that can splitbeam11 into several beams and provide several focuses.
• InFIG. 11, a twolens43,46 objective provides higher quality focusing and numerical aperture as a result of optimal positioning ofoptical surfaces41,42 and44. All of these surfaces can be spherical or aspherical.Optical surface45 oflens46 can be planar to increase numerical aperture and can be in contact withplate54.Plate54 can also be a cooling element as previously discussed.
• FIG. 12 differs from the previous figures in providing a three lens objective,lenses43,46 and49.FIG. 13 shows a four lens objective system, theoptical surfaces50 and51 oflens52 allowing an increased radius of treatment area (i.e., the distance betweenpoints39 and40).
• FIGS. 14, 14A and14B illustrate three optical systems which may be utilized as scanning front ends to the various objectives shown inFIGS. 10-13. In these figures, the collimatedinitial beam11 impinges on ascanning mirror62 and is reflected by this mirror to surface41 of thefirst lens43 of the objective optics.Scanning mirror62 is designed to moveoptical axis63 over an angle f. Rotational displacement of a normal64 ofmirror62 by an angle f causes the angle ofbeam11 to be varied by an angle2f. The optical position ofscanning mirror62 is in the entrance pupil of the focusing objective. To better correlate between the diameter ofscanning mirror62 and the radius of the working surface (i.e., the distance betweenpoints39 and40) and to increase the focusing quality, alens58 may be inserted before scanningmirror62 as shown inFIG. 14A.Optical surfaces56 and57 oflens58 can be spherical or aspherical. For additional aberration control, alens61 may be inserted betweenlens58 andmirror62, thelens61 havingoptical surfaces59 and60.
• FIGS. 15, 15A and15B are similar toFIGS. 14, 14A and14B except that the light source is a point source oroptical fiber65 rather than collimatedbeam11.Beam66 frompoint source65, for example the end of a fiber, is incident on scanning mirror62 (FIG. 15) or onsurface57 of lens58 (FIGS. 15A, 15B).
• FIGS. 16 and 16A show a two mirror scanning system. In the simpler case shown inFIG. 16, scanningmirror67 rotates over an angle f2 andscanning mirror62 rotates over an angle f1.Beam63 is initially incident onmirror67 and is reflected bymirror67 to mirror62, from which it is reflected to surface41 ofoptical lens43. InFIG. 16A, to increase the numerical aperture of the focusing beam, increase work area on the skin and decrease aberration between scanning mirrors62 and67, anobjective lens106 is inserted between the mirrors. While a simple onelens objective106 is shown in this figure, more complex objectives may be employed.Objective lens106 refracts the beam from the center ofscanning mirror67 to the center ofscanning mirror62.
• InFIG. 17, scanning is performed by scanninglens70 which is movable in direction s. When scanninglens70 is moved to anoff center position73,optical surface68 refracts a ray of light alongoptical axis71 todirection72.
• InFIG. 18, scanning is performed by rotatinglens76 to, for example,position77.Surface74 is planar andsurface75 is selected so that it does not influence the direction of refractedoptical axis72. InFIG. 19, scanning is performed by the moving of point source oroptical fiber65 in direction s.
• FIGS. 20 and 21 show zoom lens objectives to move the island of damage to different depths. InFIG. 20, a first component is made up of asingle lens81 movable along the optical axis relative to a second component which is unmovable and consists of twolenses84 and87.Lens84 is used to increase numerical aperture. To increase numerical aperture, range of back-focal distance and decrease focal spot size,optical surfaces79,80,82,83 and85 can be aspherical. The relative position of the first and second components determines the depth offocal spot12.
• FIG. 21 shows zoom lens objectives with spherical optical surfaces. The first component is made up of asingle lens90 movable with respect to the second component along the optical axis. The second component, which is unmovable, consists of fivelenses93,96,99,102, and105. The radius of curvature ofsurfaces88 and89 are selected so as to compensate for aberrations of the unmovable second component. Again, the depth of focus may be controlled by controlling the distance between the first and second components. Either of the lens systems shown inFIGS. 20 and 21 may be mounted so as to be movable either manually or under control ofcontrol218 to selectively focus on desiredportions214 of target volume V or to non-selectively focus on portions of the target volume.
• While the invention has been shown and described above with reference to a number of embodiments, and variations on these embodiments have been discussed, these embodiments are being presented primarily for purposes of illustration and the foregoing and other changes in form and detail may be made in these embodiments by one skilled in the art without departing from the spirit and scope of the invention which is be defined only by the appended claims.

Claims (18)

1. A method of treating a subject's skin comprising

applying energy to the skin so as to generate a plurality of treatment portions within a volume of the skin such that each treatment portion is separated from another treatment portion by an untreated portion of the volume.

2. The method ofclaim 1, wherein said step of applying energy comprises applying acoustic energy.

3. The method ofclaim 2, wherein said step of applying acoustic energy comprises focusing the acoustic energy onto said treatment portions.

4. The method ofclaim 1, wherein said treatment portions comprise a fraction of the volume in the range of about 1% to about 90%.

5. The method ofclaim 1, wherein said treatment portions comprise a fraction of the volume in the range of about 1% to about 50%.

6. The method ofclaim 1, wherein said treatment portions comprise a fraction of the volume in the range of about 10% to about 30%.

7. The method ofclaim 1, wherein said treatment portions extend from skin surface to a depth below the surface of the patient's skin.

8. The method ofclaim 1, wherein said treatment portions are one of cylinders, spheres, ellipsoids, solid rectangles or planes.

9. The method ofclaim 1, wherein said treatment portions are spaced lines of selected length and thickness.

10. The method ofclaim 1, wherein said volume of the skin is pre-cooled to a selected temperature for a selected duration.

11. The method ofclaim 1, further comprising pre-cooling said skin volume to at least one depth below the skin surface.

12. A method for treating a patient's skin comprising

applying energy to the skin so as to generate a plurality of periodically located three dimensional treatment portions within a volume of the skin such that each treatment portion is separated from another treatment portion by an untreated portion of the skin.

13. The method ofclaim 12, wherein said step of applying energy comprises applying acoustic energy.

14. The method ofclaim 13, wherein said step of applying acoustic energy comprises applying the energy to create sub-dermal islands of damage.

15. The method ofclaim 13, further comprising applying the acoustic energy to said treatment portions in a temporal sequence.

16. Apparatus for treating the skin, comprising

a source capable of generating energy, and

a system capable of focusing the energy generated by the source to a plurality of three dimensional treatment portions within a volume of skin such that each treatment portion is separated from another treatment portion by an untreated portion of the volume.

17. The apparatus ofclaim 16, wherein the energy is acoustic energy.

18. The apparatus ofclaim 16, wherein the system for concentrating the acoustic energy comprises of at least one phase array.

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