DEVICE FOR SUPERFICIAL WARMING UP OF FABRIC

MC 33/6110'. FCT/2r25/03720 Method and device for the superficial heating o£ tissi-ie i The iirvention relates to a method and device for bhe superficial heating of tiseue of the type stated in the preamble of patent claims 1 and 11, respectively. For the removal of lines and smoothing of prematurely aged skin {for example due to excessive exposure to sun} , for some time laser systems such as the Er:YAG and CO3 lasers have been successfully .used in dermatology as an alternative to chemical peeling. With these lasers, the skin is superficially removed. In a way similar to in the case of peeling, both the smoothing effect and the probability of undesired side-effects (scars, hyper- or hypopigmentation) increase with the depth of removal from approximately SO (am (suparficial removal) to 0.8 mm (deep peeling). The removal can have the efface of partly leveling the surface of the skin, and a tightening is observad. According to current literature, the a kin- tightening effect is explained:-by the fact that harmful, elastotic layers of skin are removed and, in the course of the subséquent healing of the wounds are replaced by a repair layer with new collagen of the type I. This effect is in principle independent of the way ih which the skin was removed or irreversibly changed; it explains why mechanical dermabrasion, chemical agents or laser-induced ablations are equally effective. WC 99/61105 - 2 - PCT/EP99/0372CI l The hear-induced shrinkage of collagen is discussed as; a further mode of acnion, existing only in the case of lasers. Type I collagen fihrils shrink when heated to a temperature range between 550C to 60oC and 70oC (beginning of coagulation) to a third of their length, without becoming biologically inactive. This is a process commencing immediately with the heating. Fitspatrick et al. presume cilia effect to be a cause of zhe immediate tightening of loose and lined skin unexpectedly observed during "resurfacing" (R.E. Fitzpatrick et al. Pulsed carbon Dioxide Laser Resurfacing of Photoaged Facial Skin, Arch Dermatol 132, 395-402, 1396). Although "resurfacing" based on skin removal is effective in many cases, it also has adverse side-effects. The most important are : - postoperative risk, of infection (in some cases coverage of the entire face winhJ £ilm is required for several days) - erythema lasting for several weeks - restricted social life for at least o week - possible hyperpigmentation, less commonly hypepigmen- tacion. 06-17-2000 FCT/EF99/03720 DESCPAjyiD Furtnermore, nhe newly formed skin shdws deviabions with respect to its structure in comparison wltli rhâ rsmaining akin. ' WiLh the existing smoothing of lines using C02 and Er:YAG lasers, the removal and new formation of skin are presumably the main factors determining the result. This hypothesis is made plausible by the extent of the depth of the layers of skin treated: the regions of removed skin (approximately 100 m) and irreversibly damaged, coagulated skin (C0a laser approximately 3 0 ta 100 jum, Er:YAG laser approximately 4 0. um) undergo the mechanism of new skin formation. For the collagen shrinkage, on the other hand, only the region adjacent to the coagulation zone is available, lying in the temperature interval between the coagulation temperature of approximately ?0oC and the lower limit of the collagen shrinkage temperature of approximately SSC to fSO'C. For both lasers, this region is relatively thin in the extent of its depth during the skin removal, so that an appreciable contribution to the smoothing cannot be expected, though it is estimated Co be greater in the case. oj: C03 lasers than, for example, in the àase OJ; Er:YAG lasers. WO-A-97 3 7723 discloses a method and device of the type stated at the beginning in which the laser wavelength is chosen with respect to the thickness of the target tissue and the spectral absorption coefficients o£ this wavelength such that the laser radiation reaches the collagen layer in the depth of the skin without experiencing any significant absorption in the layers of skin lying above. The surface of the skin may in this case be cooled before the laser Printed:08-04-200 0 AMENDED SHEET 06-17-2000 ! FCT/EP99/rT7-jn , rt-i/ û.i?3S/ Cj;720 DESCPAMD ! - 4 - radiation is applied, in ordar to avoid impairmenc of Che surface of the skin by the possible slight absorption in the upper skin. In this cQ3e, the selection of laser is restricted to certain laser wavelengths becauae of the recruired great depth of penetration into the tissue. EP-A2-0 763 371 discloses a method and apparatus for skin rejuvenation and wrinkle smoothing in which ablation takes place by means of an EnYAG laaer, a flashlamp additionally being used to produce light pulees in the range of 500-1000 nm for heating up the collagen. The Er:YAG laser merely brings about ablation of the surface on account Of the small depth of penetration of the light pulaae, while the flashlamp has a greater depth of penetration and reaches the collagen. The heating of the collagen by the Er:YAG laasr is obviously not regarded as adequate. For this reason, the Br:YAG laser is used in the customary ;way merely for removing the upper layers of skin. The invention is based on the object of providing a method and device of the type stated at the beginning which permit improved elimination of skin damage or skin impairments, such as for example scars, lines and the like. Printed:08-04-2 0 00 AMENEED SHEET 06-17-2000 PCT/EP99/03720 OESCPAMD - 4a - This object is achieved by the features specified in patent claims 1 and 11, respectively. Advantageous irefinements and developments o£ the invention emerge from the subclaims. in the caae of the method and device according to the invention, the heating extends from the surface of the skin, in which the absorption substantially takes place, over a relatively great layer thickness beneath the surface of the Skin, it being possible in a preferred refinement oJ! thm invention to dispense completely with removal in many cases. In other cases, it may be advisable to use a combination of local removal (for example line ridges) and heating over a large region. Printed:08-04-2000 AMENDED SHEET WO 39/61105 - 5 - PCT/EP99/03720 The range of problems so far discussed with respect to lines also apply in a similar way to the treatment o£ scars. In principle, renewed damage to the surface of the skin should be minimized here. A targeted hea.t-induced shrinkage of (scar) collagen is also possible in this case. According to a preferred refinement of the method and device, various types of laser light sources may be used as the light source, such as for example a Ho:YAG laser, an Er:YAG laser, an Er:YSGG laser, a Tm:YAG laser, a C02 laser or an Nd:YAG laser, these only being some examples. In the case of all types of light sources, a considerable amount of energy can be introduced into the tissue beneath the surface of the skin by the pulse concrol according to the invention. in this case, the energy level is chosen such that there is no removal, but adequate heating of the deeper-lying collagen layer is obtained by heat conduction. The invention is explained in more detail below on the basis of an exemplary embodiment represented in the drawing. Represented in the upper half of the drawing is a series of light, pulses, with energy densities of the individual pulses preselected such that the temperature profiles at the surface of the skin and in the layers of tissue lying beneath the surface of the skin, at depths of |jjn, 100 /im, 150 um and 200 (j.m, repreaantad in the lower WO 99/61105 - S - PCT/SP9S/03720 j i part of the illustration are obtained over timel The vertical scale indicates the temperature difference AT in "K with respect to the temperature of the skin. As the drawing reveals, in the case of the example represented, a series of laser pulses l uo 10 are applied to the surface of the skin, the first pulses of the series, for example pulses 1 and 2, preferably having a higher energy level, energy density or power, which however must lie below the removal threshold, in order to achieve rapid heating initially of the surface of the skin and then, after a time delay, heating of the desired layer of tissue lying beneath it by heat conduction to the target temperature. As the curve for a depth of 50 .um reveals, this» ca-usea the temperature at this depth to increase relatively rapidly and then be maintained as uniformly as possible at a desired difference from the target temperature of, for example, 4 0 0K. As can be seen, the temperature for the cur"v<s for a depth of 5 0 um drops slightly again after application of the three first light pulses and is then for example raised again to the desired limit temperature by the pulse represented at 4. The same also applies to the subsequent pulses 5 to 10, which in each case bring about reheating to the target temperature. The pulses of the pulse sérias following the first pulses may in this case have a lower energy level, brought about by a lower power a.nd/cr duration, since the energy required for maintaining the desired target WC 99/S1105 - 7 - PCT/E299/03720 temperature is lower- The temperature at the depth of 10 0 Jim and in the deeper-lying layers of 150 im and 200 (am in this i case increases continuously and approaches a desired limit value at a cemperature difference of, for example, 3 0oK for the depth of 10 0 p.tn. According to an advantageous refinement of the invention, the temperature ac the surface of the akin, and if appropriate in layers lying beneath it, can be monitored, for example by a surface temperature sensor, so that a corresponding pulse control of the individual pulses can take place, it being ensured, for example, that the prescribed target temperature, for example of irreversible thermal damage, is never exceeded. with lower requirements for a rapid heating-up time, a pulsed laser can of course equally be clock-controlled with a constant pulse series frequency and pulse energy level or pulse energy density or pulse power below the ablation threshold, backed up if appropriate by measurement of the surface temperature of the skin, eo that comparable temperature increases can be achieved; The device according to the invention permits targeted treatment of the skin by appropriate control of the pulse series and energy levels of individual pulses, it being possible for these energy levels and pulse durations or pulse intervals to be chosen according to the desired application. I WO 39/61105 - a - PCT/EP99/03720 The device: according to the invention can not only bo used for the thermal changing of collagen fibrils, but can serve generally for the purpose of inducing physiologically- specific temperacure increases. For example, to increase zhe enzyme acrivicy in the skin, it is meraly naceesary to induce a temperaturs incraass of a few "K. To deactivate enzymes, layers of tissue lying beneath the surface of the skin should be heated to a temperature of approximately 430C to 550C. For shrinkage of collagen without coagulation, temperatures in the range from approximately 550C to 60oC and 70UC should be used, for coagulation the temperature range is 70oC to 100oC. If the method and device according to the invention i are to h& used for superficially changing hard tissues (bone, tooth enamel), the temperature increase should be several 100 K- If desired, the pulse series represented in the drawing,may be fallowed by a subsequent removal pulse of higher jpower. ; If the method and device according to the invention are to be used for che removal of malignant or bacterially or virally contaminated tissue, th« machod according to the invention reduces the risk of entraining living tumor cells, bacteria or viruses by the possibility of performing a coacrulation before the removal. WO SS/SI105 PCT/EP99/03720 In the case of a specific example, corresponding to the drawing, a number o£ pulses o£ an Eir:YAG laser- with a notai energy level of approximately 100 mj was used (cf. caJble) . With 56 mJ altogether, the first three pulses in this case contain over half the total energy, these pulses following relatively quickly one after the other. This leads to rapid heating of the surface zo the permitted target temperature increase of AT = 4U0K at a depth of 50 (am. The subsequent pulses 4 to 10 serve simply for stabilizing this temperature. For this stabilization, increasingly lower individual pulse energy levels arc subsequently required, it being possible for there to be relatively long pauses between the individual pulses. In this way, virtually stable gradients are then achieved in'deeper layers of tissue, as can be seen from the curves for a depth of 1Q0 (im or ISO fim and 200 fim at the end of the ten pulses. TABLE Pulsenumber l 2 3 4 5 S 7 9 9 Energy/mJ 33.3 23.3 3.4 7.2 5.9 s.o S.3 4.7 4.4 d .4 Irradia-tion./J<3m"z 0.74 0.74 0.30 0.2a 0.22 0.19 0.17 0.15 0.14 0.13 Timeintervalfrom thepreviouapulse/ms - 4 4 18 18 19 19 13 ia 18 This laser and the pulse series merely represent a preferred exemplary embodiment, without any restriction. WC 99/51105 PCT/EP99/03720 There is, for example, also the possibility of using a laser with a high pulse frequency, for example 5 0 Hz, which is additionally controlled/ if appropriate, by a sensor measuring Che temperature of the surface of the akin. II Patent claims i A menhod for the superficial fceacing of tissue with the aid of a pulged light source, in which method a series of light pulses are applied to the surface of the tissue, wherein a light: source with a wavelength of which che light is absorbed mainly in the region at the surface of th» skin which lies above a tissue depth of SO m is used, wherein a first part of the series of light pulses is configurad such that rapid heating of the surface of the skin and chen, after a time delay, heating of regions of rissue lying beneath this region of the surface of the skin to a prescribed target temperature is achieved by heac conduction without tissue removal, and wherein a subséquent part of the 3eries brings about an oscillation of the temperature of the regions of tissue about a value lying slightly below che target temperature. 2- The method as claimed in claim l, wherein the puïse energy levels or pulse energy densities of the pulses following the first pare of the series and/or the interval between the subsequent pulses is dimensioned such that only slight deviations from the target, temperature occur. 3. The method as claimed in claim 1 or 2, wherein the energy level, energy density or power of the individual pulses lies close to the removal threshold for tissue, but below in. AMENDED SHEET