OA10619A - Biological tissue stimulation by optical energy - Google Patents

Description

Οΐ 06 19 -ι-

Description

Biological Tissue Stimulation by Optical Energy - Background of the Invention 1. Field of the Invention

The présent invention relates çjenerally to thetreatment of living biological tissue by optical IC irradiation, and in particular to a method for stimulatingsoft, living tissue by laser irradiation. 2. Description of Related Art

Various non-surgical means hâve been employed in the 25 therapeutic treatment of living tissue. Such techniquesu.wiütcu ti-r: app_j.oao*üû o^ u^tiu^ouxt eueig\ , electrical stimulation, high frequency stimulation bvdiathermy, X-rays and microwave irradiation. Techniquessuch as electrical stimulation, diathermy, X-ray and 20 microwave radiation hâve shown some therapeutic benefit forsoft tissues. Kowever, their use has been somewhat limitéebecause of tissue damage caused by excessive thermaleffects. Consequently, the energy levais associated withtherapeutic treatments involving diathermy, X-ray, 25 microwave and electrical stimulation hâve· been limited tosuch low levels Chat iittle or no benefit has beei^iobtained. Moreover, the dosage or exposure to microwavesand X-ray radiation must be carefullv controlled te· avoidradiation related health prcblems. Ultrasonic energy is 010619 ncn-preferentially absorbed and affects ail of the surrounding tissue.

Optical energy generated by lasers has been appliedfer various medical and surgical purposes because of themcnochromatic and cohérent nature of laser light which canbe selectively absorbed by living tissue depending uponcertain characteristics of the wavelength of the light andpreperties of the irradiated tissue, inciuding refIectivity, absorption coefficient, scattering coefficient, thermal conductivity and thermal diffusionconstant. The refIectivity, absorption coefficient andscattering coefficient are dépendent upon the wavelength ofthe optical radiation. The absorption coefficient is knownto dépend upon such factors as interband transition, freeélectron absorption, grid absorption (phonon absorption),and impuritv absorption, which are dépendent upon thewavelength of the optical radiation.

In living tissue, water is a prédominant componentwhich has an absorption band according to the vibration ofwater molécules in the infrared range. In the visiblerange, t'nere existe absorption due to the presence ofhemcglobin. Furt'ner, the scattering coefficient in livingtissue is a dominant factor.

Thus, for a given tissue type, the laser light mayprepagate through the tissue, substantially unattenuated,cr rray be almost entirely absorbed. The extent to whichthe tissue is heated and ultimately destroyed dépends onthe extent to which it absorbe the optica! energy. It is.générai!;.· preferred that the laser light. be essentiel!;·transmissive m tissues which are desired not to be ü 1 Ü 6 1 9 affected, and absorbed by the tissues which are to beaffected. For example, when applying laser radiation in atissue field which is wet with blood or water, it isdesired that the optical energy not be absorbed by the 5 water or blood, thereby permitting the laser energy to be drrected specifically to the tissue to be treated. Anotheradvantage of laser treatment is that the optical energy canbe delivered to the treatment tissues in a précisé, welldefined location and at prédéterminée, limitée energy 2 ievels.

Ruby and argon lasers are known to émit optical energyin the visible portion of the electromagnetic spectrum, andhâve been used successfully in the field of ophthaïmologyte reattach retinas to the underlying choroidea and to .5 créât glaucoma by perforating anterior portions of the eyeet reiievë interocoular presser^. Trm· ruby iase: enerovnas a wavelength of 694 nanometers and is in the redportion of the visible spectrum. The argon laser emitsenergy at 4 88 and 515 nanometers and thus appears in the ÎC hiue-green portion of the visible spectrum. The ruby andargon laser beams are minimallv absorbed by water, but aremtensely absorbed by blood chromogen hemoglobin. Thus,the ruby and arçon laser energy is poorly absorbed by non-pigmented tissue such as the cornea, lens and vitreous 25 humer of the eye, but is preferably absorbed by the pigmented retins where it can then exert a thermal effect.

Anocher type of laser which has been adaptée forsurgirai use is the carbon dioxide (CCy) gas laser .whichemits an optical beam which is intenselv absorbée by water. 2 2 Tes wavelencth cf the CO, laser is 1P.6 micrometers and 01 06 19 -4- therefore lies in the invisible, far infrared région of theelectromagnetic spectrum, and is absorbed independently oftissue color by ail soft tissues having a high watercontent. Thus, the CO2 laser makes an excellent surgical 5 scalpel and vaporiser. Since it is completely absorbed,its depth of pénétration is shallow and can be preciseiyccntrolled with respect to the surface of the tissue beingtreated. The CO2 laser is thus well adapted for use mvarious surgical procedures in which it is necessarj’ te 10 vaporise or coagulate neutral tissue· with minimal thermaldamage to nearby tissues.

Another laser in widespread use is the neodymium dopedyttrium-aluminum-gamet (Nd:YAG) laser. The NdiYAG laserhas a prédominant mode of operation at its secondary 15 wavelencth of 1,320 nanometers in the near infrared régionof the electromagnetic spectrum. The Nd:YAG opticalémission is absorbed to a greater extent by blood than bywater making it useful for coagulating large, bleedingvessels. The Nd:YAG laser at 1,320 nanometers has been 20 transmitted through endoscopes for treatment of a varietyof gastrcintestinal bleeding lésions, such as esophagealvarices, peptic ulcers and arteriovenous anomalies. Suchapçlications of laser energy are thus, well adaptec wherehier, energy thermal effects are desired, such as tissue 23 vaporization, tissue cauterization, coagulation and as asurgical scalpel.

The followinc U.£. patents disclose apparatus andmsthod fer therapeutic treatment of living tissue by alaser irradiation: î f 3,456,651 3,720,213 4,141,362 10 15 20 25

3C -5- 4,144,888 4,367,729 4,561,440 4,573,465 4,589,404 4,601,288 4,604,992 4,672,969 4,692,924 4,705,036 4,931,053 4,966,144 prior artin certain, spe

Three patents; Dew, 4,672,969.00; 1,'Espérance, Jr.4,531,053.00 dated June 5, 1990; and Rochkind, et al4,966,144.00 dated October 30, 1990, beat describe the

This prior art teaches the use of laser energy:ic applications. Dew discusses the use of a laser, specifically, a Nd:YAG type laser operated asecondary wave length of 1,320 nanometers, Dew disclosesthat Nd:YAG lasers ordinarily operate at 1,060 nanometers.The purpose of the Dew patent is to use a laser to effectwound closure and reconstruction of biological tissue. Thelaser enerçry is cor.verted te beat which vicimateiy breakrdowr. the tissue intc collagenous éléments, which act as"biological glue". L'Espérance teaches use of two laser beams used in thevisible red or low infrared and extremely low power laserste irradiate tissue. L'Espérance teaches the use either ahelium-neon or krypton lasers. The wave length used by1'Espérance is 61G-660 nanometers delivering an output of.15 milliwatts.

Rochkind dated October 30, 1990, uses either cohérentor noncoherent life, but describes a helium-neon laseroperating at 632 nanometers with an intensitv of 16milliwatts per sçuare centimeter or an argon type lasergeneratmg light at 465 or 520 nanometers with a iightintensitv of about 40 milliwatts per square centimeter. In -6- 01(1619 addition, Rochkind describes a two-step process inachieving the methods sought by the invention; a iirsttreatment while the tissue is open and exposed duringsurgery and a second treatment after ciosure. z>

Qb~iect of the Invention

The application of conventional lasers for the purposeof stimulating soft tissue to cause u réduction in pain andinflammation, in stimulation of microcirculation to reduce IC healing time has been attempted at verv low power levels,typically well under 100 miliiwatts. Although sometherapeutic benefits hâve been achieved, the treatment timehas been unacceptably long.

Accordingly, the object of the présent invention is to 15 provide a method for safely and effectively applying réactivé laser energy to living tissue for therapeuticcomposes, for example, to reduce pain, reduce inflammationat higher levels of power, and enhance the healing oftissue by stimulation of microcirculation, without exposing 20 the tissue to damaging thermal effects. This method shortens treatment time beyond what if known by the art.

Sunm.amv of che Invention

The method of using a low level reactive laser system 25 froc. 100 miliiwatts - 800 miliiwatts in either a pulsed orcontinuons mode with optical energy produced by a Nd;YAGlaser at a fundamental wavelength of l,0t>4 nanometers has.been round to reduce pain m soft tissues, reduceinflammation and enhance the healing oi tissue by 3 Z stimulation of microcirculation without subjecting the 0)0619 -7- living tissue to damaging thermal effects. In analternative method, optical energy is produced by anecdymium doped yttrium-lithium-fluoridc (Nd:YLF) laser ata wavelength of 1,055 nanometers or by ruine other laser in 5 a preferred wavelength range of front about 1,000 to 1,150nanometers. The living tissue is irradiated with opticalenergy at a wavelength and at a power dissipation level inthe tissue to cause the amount of optical energy abaorbedand converted te heat to be withiri a range bounded by a IC minimum absorption rate sufficient te elevate the averagetempérature of the irradiated tissue to a level above thebasal body température, but which is less than theabsorption rate at which tissue is converted into acollagenous substance. The wavelength, spot or beam size, 15 power, time exposure are carefullv controlled to produce anotaoeable warming effect in the irradiai ed tissue, butwhich is limited to avoid tissue damage by thermal effects.

None of the prior art cited teaches the présentinvention. As set forth in the spécification, a Nd:YAG 20 laser opérâtes at its primarv wavelength of 1,064 nanometers with a power of 80-100 milliwntts or a Nd:YLFlaser opérâtes at a wavelength of 1,055 nanometers with thesame power range. Neither L'Espérance nor Rochkind teachesthe use of the Nd:YAG laser in this particular mode. Both 15 1'Espérance and Rochkind detail the preferred method of operation as being a wavelength approximately half of theprésent invention. In tact, L'Espérance uses two beamsrather than one. Nor.e of the prior art discloses the useof a Nô:YAG laser at its pnmary wave lenuth of 1,064 3 Z nanometers. -8- 010619

The following chart compares the Dew, L-Esperance andRochkind art with the présent invention:

Patent Laser Type Wave- length (NM) Power (MW) Use Dew Nd:YAG 1,320 1000-5000 Scapel L'Esper- He-Ne 633 .15 Treatment i ance Rochkind i He-Ne Ar 632 520 16 80 Treatment i Bellinger Nd:YAG 1,064 100-800 Treatment 10 While L'Espérance might teach Rochkind, none of the prior art even hints that the Nd:YAG laser could be used inthis fashion with this much power and the desired résulta.

Description of the Preferred Bmbodimcnt 15 According to the preferred method, the laser energy is produced by a Nd:YAG laser at a fundamental wavelength of1,064 nanometers at an output power level of from 100 - 800milliwatts. The laser optical energy is applied to régionsof the body which recuire a decrease in muscle spasm, 2'. rnoreased circulation, decrease in pain o: enhanced tissuehealing. The surface area is demarcated and the surface ofthe tissue is irradiated with the laser beam for the amountof time and intensity necessary to produce the desiredrherapeutic effect, with the energy·· density of the 25 irradiated tissue being iimited to the rance of from about1 jouies/cirô to about 15 youles/cm. The intensity andduration cf treatment is determined by the character of the RECBFIED SHEET(RULE 91) οιoeio 10 tissue te be treated, the depth oi pénétration desired, theîcuteness of the injury and the condition of the patient.

Therapeutic treatment by a low level reactive laserSystem. has been demonstrated for the purposes of reducingpain, reducing .inflammation, and enhancing healing ofdamaged tissue by stimulation of microcirculation, ailbeinç successfully accomplished without producing damagingthermal effects in the tissue. A Nd:YAG laser resonatorwas usée as the laser source. Its principal wavelength was1,064 nanemeters, and nad an adjustable beam energy outputcf 102 m.iiiiwatts - 800 milliwatts. The laser was capablecf opération in a pulsed or continuous mode, and its outputwas ccntrclled by an exposure timer in the range of 0.1 -5.5 mtnutes. The puise on-time was adjustable front 0.1 -.5 seconds in 0.1 second intervals. The puise off-time was aise adjustable front 0.1 - 9.9 second:· in 0.1 secondtntervais. The Ne:YAG laser beam opérâtes in the nearinfrarec portion of the electromagnetic spectrum at 1,064nanemeters, and t'nus is invisible.

New referrinç to FIGURE 1, the laser 100 produces alaser beat, 102 that exits the output coupler of the laserbeat and is steerec by a pair of alignment wedges ±04 20

JU refera passing threugh a circularly variable, neutralcansity attanuator 106. Light passincj through theatténuâtes 106 is focusad through a 90 mm focal length lens11Ξ ente the proximal end of an optica.1 fiber cable 110. T.ta m.atnoc for deliverinç the beam to the farget sight is aflauirle quartz fibar and focusmg handpiece 114.

The main beam attanuator 112 is a shutter piacedcutaide the laser beat bstween the output coupler of tnelaser and a beam stéarine mirror (net rhown). It inciudes 0)0619 10 15 - 10 - four compcnents: a 90 degree reflecting prism 120, ashutter arm 120, a shutter mounting bracket <Jnot sksoun) andan actuating solenoid 124. The prism 120 is mounted to theshutter arm so that, in the normally closed position, theprism 120 intercepts the laser beam 102 and reflectn itcownwardly into a beam dump in the laser deck (not shown) .The solenoid 124 is energized when an output chenue! hasbeen selected and foot pedal (not shown) is depressod,which causes the shutter arm 120 to raise and allow:. thebeam to pass. When the solenoid arm is de-energized, thesnutter drops into the closed position.

The optical energy is produced by a cohérent llghtsource, preferably a laser having a wavelength of 1,064nanometers in the near infrared région oi the electromaçnetic spectrum. The laser is provided with anoptical fiber guide and coupler for directing the beam ofcptrcal e.nergy to the tissue surface. The energy of thecpnical radiation is controlled and applied to produce aminimum absorption rate in the irradiated tissue which willelevate the average température of the irradiated tissue toa lever above the basal body température, but which doesnon exceed the maximum absorption rate which is greatenough te convert the irradiated tissue into a collagenoussurstance.

It has been cetermined through extensive testing thatthe foreçoing condition is satisfied by a Nd:YAG lasercperatec at its primary wavelength of I,0o4 nanometers at apcwer cutput level of from 100 - 800 milliwatts, with thelaser team being fccused to produce an energy density ofthe prcjected Laser beam. in the range of i nom about 1.0icu.e/cc- te about 15 ioules/cm2 at the treatment site. u 1061 y -11-

Certain physiological mechanisms in the tissue and atthe cellular level hâve been observed when the aboveprocess is used. In the évaluation of the microcirculatorySystem, for example, it has been demonstrated the.· blood 5 vessel walls possess photosensitivity. When the blood vessel walls are exposed to laser irradiation as set forthabove, the tonus is inhibited in smooth myocytes, thusinoreasing the blood flow in the capilluries. Other-effeccs w'nich hâve been observed are: parapherai capillarid IC recvascularization, réduction of blood platelet aggregation, réduction of 02 from the triplet to thesinglet form which allows for greater oxygénation of thetissue, réduction of buffer substance concentration in theblood, stabilization of the indices of érythrocyte 15 deformation, réduction of products of perioxidized lipidoxygénation of the blood. Other effects which hâve beenobserved are increased index of antithrombin activity,simulation of the enzymes of the antioxidant System suchas superoxide dismutase and catalase. An increase in the 20 venous and lymph and outflow from irradiated région hasbeen observed. The tissue permeability in the area issubstantially enhanced. This assiste in the immédiateréduction of edema and hematoma concentrations in thetissue. At the cellular level, the mitochondrie hâve also 25 been r.oted to produce increased amounts of ADP with subséquent increase in ATP. There also appears to be anincreased stimulation of the calcium and sodium pumps atthe tissue membrane at the cellular level.

Ai the neuronal level, the following effects nave been 31 observed as a resuit of the foreaoing therapeutic 0 î OGÎ 9 -12- treatment. First, there is an increased action potentialof crushec and intact nerves. The blood supply and thenumber of axons is increased in the irrudiated area.Inhibition of scar tissue is noticed whon tissue istreated. There is an immédiate increase in the membranepermeability of the nerve. Long term changes in thepermeability of calcium and potassium ions through thenerve for at least 120 days hâve been observed. The RNAand subséquent DîîA production is enhanced. Singlet Ce ipproduced v.’hich is an important factor in cell régénération.Pathological degeneration with nerve injury is changed torégénération. Eoth astrocytes and oligodedrocytes arestimulated which causes an increased production ofperipheral nerve axons and myelin.

Phagocytosis of the blood celle is increased, therebysubstantially reducing infection. There also appears to bea significant anti-infiammatory phénomène which provides adecrease in the inflammation of tendons, nerves, bursae inthe joints, while at the same time yielding a strengtheningof collagen. There is also an effect on the significantincrease of granulation tissue in the closure of openwounds under limitée circulation conditions.

Analgesia of the tissue has been observed inconnection with a complex sériés of actions at the tissuelevel. At the local level, there is a réduction ofinflammation, causinc a reabsorption of exudates.Enxephalins and endorphins are recruited to modulate thé-pain production toth at the spinal cord level and m thebrain. The serornogenic pathway is also recruited. V.'hiitit is not ccmpletely understood, it is believec that the- 01061!) -13- irradiation of the tissue causes the return of an energybalance at the cellular level whicb is the reason for theréduction of pain.

In an alternative method, laser energy is produced by5 a Nd:YLF laser at a wavelength of 1,055 nanometers. Other lasers could be usée or developed to operate in a preferredrange of from about 1,000 to about 1,150 nanometers at thesans power level.

Although the invention has been described with 10 reference to preferred method, and with reference tospécifie therapeutic applications, the foregoingdescription is not intended to be construed in a limitingsense. Modifications of the disclosed embodiment as wellas alternative applications of the invention will be 15 suggested to persons skilled in the art by the foregoingspécification. lt is therefore contemplated that theapoended ciaims will cover any such modifications orembodiments that fall within the true scope of theinvention. 20

Claims (13)

14. 01061!) The daims

1. The use of a low level reactive laser in a method for treaLing a small treatmsnt area of a biological tissue of a living subject withoutexposinc the tissue to damaging thermal effects, the method comprising: usingthe low level reactive laser to generate cohérent optical energy radiationhaving a wavelength in the range of the near infrared région of theelectromag-etic spectrum at a power output in the range of from about 100milliwatts to a_bout 800 milliwatts, and fccusing said cohérent optical energy radiation on said smalltreatr.snt area to achieve a rate of absorption and conversion to beat in theirradiated rissue in the range bstween a minimum rate, aufficient to clevatethe average température of the irradiated tissue to a level above the basalbody température of the living subject, and a maximum rate which is less thanthe rate an vnich the irradiated tissue is converted into a collagenoussubstance, wnerein the density of the optical energy radiation is in the rangeof frer. about l.C joule/cm2· to about 15 joules /cm1 at the irradiated tissuesite.

2. The use according to Claim 1 wherein said wavelength is about1,064 nanemeners.

3. The use according to claim 2 wherein said low level reactivelaser comprises a Nd:YAG laser.

4. Tne use according to claim 3 wherein said tissue is irradiatedwith sait cob-rent optical energy radiation at a plurality of small treatmentareas in a gr_ô for the amount of time and intensity necessary to provide atherapeutic effect.

5. TiiG use according to Claim 3 wherein each owalj treiitment aieni i i bas an area in taa range of about. 0.5 mm to about 2mm .

6. The use according to Claim 3 wherein said low lovol réactivé.'laser is pui_sed with each puise on tune being in the· range o£ O.ï to 9.9seconds and each puise ofi time being in the range of ü.J to 9.9 seconds. the use according to Cia..ni 3 wherein said low luvel reactivelaser is operated in a continuouu n.ode. B. the use according to Claim 1 wherein sa.i.d wavelength is about1,055 nanometers.

9. The use according to claim ·'> wherein π a.ici low levai réactivé Ι,ι.ίργ comprisen a ; -i:Yl.r laser. JC. t.ic use according to Claim 9 wherein said tisauc is irradratei * with sai-i coiicrcnt optical energy radiation at a plural it.y of omall treatmcul.areas in a or_d fer tiie aniount df time and intennity ncccssary to provid·. a r< therapeutic effect. 11. T/.e use according to Claim 9 wherein each muai 1 Lreatmont are?Ibis au area ir the range of about 0.3 mm L to about 2 mm z. !?. ΊΊι·~ ur.-~ aecorling to Claim 9 wherein raid low level. réactivé laser 1 s puis·-·.! wi-.h each puise on time being in the range of 0.1 to ? .'> JP seconds and each puise off Lime being in the range of 0.1 to 9.5 secon...

13. The use according to Claim 9 wherein said low lowl roacti·.·lancr j. n cpcraLcü ir a continuons mode . V i. t { j ,· t!i.? π ü d according to Ci/À-ti! J. vihc. rein lov level ruac-iVi j.aser comrrises a Nd:ïAG laser.

15. The une according to Clair. r uvrein siuid J αν lcvc^ reac,.i\u laser corrrises a Nd-.YLF laser. 10 20

16. The use according to Claii i- 1 wherc:n uuid tiuuuc is irra.cn. a/-‘rwitk raid coliorcut optieal onorgy radie tio» at a plurulity of troatincnt pointain a grid for tho amouiit of time end inl onnity nocoouary to previde athcrapeutic effect.

17 . The use according to Claire 1 wherein each troatincnt point haa anarea in tes rance of about 0.5 jnm2to < bout 2mm7-. 1 * Ine use ûccordxnç to ci ?mt 1 whsrcin uuid low level rcactivelaser is puiaori with each puise or time baing in the range of 0.1 to fseconds a:.ri onch puino off Lime br,"7 !.. the range of 0.3 to 9.5 second;. laser 15

12. The use accortliny to daim 1 wheroin tiaid low level reactiviis crcrated in n continuoua mole. 2C. The use according to cia j» 1 wheroin oaid wavclorigti. is in t;range of fro;:. about 1 , 000 iiaiioiucteru to abc-ut 1,150 nanonictors. app malus for heating hioiü^ ;cal tissuc, comprising:iassr omputting a laser beam v th a wavclerigih in the range of the near :f the eîectrornagneric speciruif, the iriser producing cohérent opticc:a: a rower ouiput in the rang., of from about 100 milliwatis tto abc CC fr.cans recciving the user ! hert.”,· eenei’.v ’.scr ! iuni and conirolling the cohérent opt;c.<rudir. n·?:; r :::·.· ie ~cr beain for delivery to - u- biol<. çicei tïne nt anthe range c n.-'oid ! joule/cnri to accct 15 joules/crr/. 25

22. The apparatus in accordance with Claiin 21 wherein the control mcans Controls·and femmes the cohérent optical energy radiation on an area of the biological tissue to açhievea rate cf aeserptton and conversion to heat ,n the irradiated tissue in the range between aminimum rate, sufncient to elevate the average température of the irradiated tissue to - ievelabuve toc rasai cody température of the living subjert, and a maximum mte winch in !-: ; litc mte a: --.2.:2 the irradiated tissue is convcrted into a collacenous substance. 2? Tr.e apparatus in accordance with Claim 21 wherein the wavclenyth is in the m?·- of hem r2- _·. ,COO nanometers to about 1,15(. nanometers. 10 2- he apparatus in accordance with Claim 21 wherein the low ievei reacti·.·„· lasercomprise? a Xa:Y.-\C- laser. The apparatus in accordance with Claim 21 wherein the low ievel reacti’.c laser mwa c. : ; a: L. laser. me an: moun Pr.e anparatus in accordance with Claim 22 wherein the t'.ssuc is irrac. ·.:;: 2 wmatucal energy radiation at a pi irality rf sma’i treatmer.t areas in a gr'.c nu meand mtensity neccssary to previdc a therapcutic effee: ""i:·: apearatus in accordance whh Claim 26 wherein eacn smail treatmer.t area h asr.r.ce cf about 0.5 mm2 te abos t 2 mm.3. 15 1/. 010619 2S. The apparatus in accordance with Claîm 21 wherein the low levei reactive laser . ; » iis cci v.7 : : i eue;-, puise on tinte being in the range of 0.1 to 9.9 seconds and each puise off c * * u c c c i n £ *·. the ronge of 0.1 to 9.9 seconds. 29. The npparatus in accordance widr Claim 21 whcrein tue low ievel réactive laser s orerated in a continuons mode.

30. The npparatus in accordance with Claim 29 whcrein the tissue is irradiated with tir: cohérent epdcci energy radiation at a plurality of sm3ll treatment areas in a grid for the artteunt of tir r.e ?jia imensity neccssary to provtde a thcrapeutic cffcct. 31. Tire npparatus in accordance with Claim 21 wherein the contre’, means compris denstiy at;er.uaic :. 10 32. 7;;: t’pnarntus in accordante with Clairt’. 21 whcrein the contrai mean^ comp