WO2008002198A1

WO2008002198A1 - Laser device for ablating tissues and for lithotripsy

Info

Publication number: WO2008002198A1
Application number: PCT/RU2007/000339
Authority: WO
Inventors: David Georgievich Kochiev; Anatoly Leonidovich Bondarenko
Original assignee: David Georgievich Kochiev; Anatoly Leonidovich Bondarenko
Priority date: 2006-06-23
Filing date: 2007-06-21
Publication date: 2008-01-03
Also published as: RU2318466C1

Abstract

The invention relates to medical engineering and can be used in surgical urology, in particular for treating benign prostatic hyperplasia, and in lithotripsy for treating vesical calcification. The inventive laser device for ablating tissues and for lithotripsy comprises a laser emitter which is embodied in such a way that it generates pulses and comprises an optical generator and an extracavity converter for second harmonic conversion of radiation, wherein said laser emitter generates pulses in a time range of 0.1-10.0 microseconds, the optical generator is based on a Nd:YALO3 crystal with a q modulation by a gate at a frustrated total internal reflection and with a fibre time-delay line, an optical insulator is arranged between the optical generator and a two-pass optical Nd:YALO3 crystal-based amplifier, the extracavity converter is embodied such that the conversion efficiency thereof is equal to or greater than 30% and an attenuator is placed at the radiation input of a fibre tool. The invention makes it possible to efficiently used the device for treating two the most commonly encountered urological diseases - benign prostatic hyperplasia and vesical calcification.

Description

LASER INSTALLATION FOR ABLATION OF TISSUES AND LITHOTRIPSY

Technical field

The invention relates to medical equipment.

State of the art

Currently, one of the most common diseases in urology is benign prostatic hyperplasia (BPH) and urolithiasis (ICD). With the introduction of endoscopic methods of surgical treatment into surgical practice, treatment methods using laser systems are becoming more widespread, in which the delivery of laser radiation to the affected area is carried out using thin optical fibers. However, laser devices known from the prior art are intended, as a rule, for the treatment of either only BPH or only ICD. Currently known methods of treating BPH using laser systems are based on the action of high-intensity laser radiation (with radiation powers predominantly more than 60 W) on hyperplastic prostate lobes in order to remove tissue. Photothermal and photomechanical processes in the interaction of high-power laser radiation with tissue lead to vaporization, ablation and coagulation of the tissue remaining in the area of influence.

In particular, US Pat. No. 5,593,404 (Costello, et al) describes a device for ablating tissue of a hyperplastic prostate gland based on an Nd: YAG laser, with a radiation wavelength of 1.064 μm, operating in a continuous generation mode, with an output radiation power in the range of 40 Watts up to 90 watts. The exposure is carried out using a fiber catheter with a lateral output of radiation. The radiation power density on the surface of the fabric, with a spot diameter of 1 mm, is 5, IxIO ³

9 A O

W / cm to 1.1x10 W / cm. In addition to the narrow scope, The device is also that due to the large effective depth of penetration of radiation with a wavelength of 1.064 μm, a large proportion of tissue (up to several millimeters thick) after exposure is coagulated. Coagulated tissues leave for a long period (up to 3 weeks), which leads to urinary retention and long periods of catheterization. The recovery process is accompanied by sensations of postoperative pain and discomfort, the risk of infectious inflammation.

To date, devices based on pulsed Ho: YAG lasers, with a radiation wavelength of 2.1 μm, operating in the free generation mode, with a radiation pulse duration from 100 μs to 500 μs and an output power of up to 80 W, are widely used.

Having a high absorption coefficient (μ _a = 26.93 cm ^"1 - GM HaIe and MR Querrou," Orthisal components of water and 200nm to 200μm wavelength, Arr. Ort, 12, 555-563, 1973), radiation Ho : The YAG of the laser is well absorbed both in the water contained in the tissue of the prostate gland and in the aqueous solution used to irrigate the area of exposure.To prevent the loss of energy and side effects associated with heating the water, in the known devices the contact effect of the distal end of the fiber on tissue. Contact excision of the tissue, in turn, requires the use of the use of special devices, marcellators - see US Pat. No. 6,156,049 (Lovato, et al.) - for grinding and removing parts of excised tissue from the prostatic urethra. With endoscopic access, the ability to manipulate the instrument is limited and contact exposure to the desired tissue sites may not be possible. also a device based on an Nd: YAG laser operating in the quasi-continuous mode of generation, with the generation of the second harmonic of radiation, with a radiation power of up to 80 W (see US 6,986,764, Davert et al.). The device has a radiation wavelength of 0.532 μm, the radiation pulse is a train of short (<1 μs) pulses following each other with a high repetition rate (25 kHz), the total duration of the train can be from 1 ms to 50 ms. 0.532 μm radiation has a larger the coefficient of effective absorption by the tissue of the prostate gland than the radiation of 1.064 μm, its absorption by water is insignificant (μ _a = 4.34xl0 ^" cm ^{" 1} - RM Rohre and ES Frу, "Absorptioprestraum (380-700nm) оf рuеr water. II. Ipteggati pvitu teasurepetts "Arr. Ort, 36, 8710-8723, 1997). As a result of the exposure, the proportion of tissue is greater than when exposed to 1.064 μm radiation, and the depth of the residual coagulated tissue does not exceed 1-2 mm. The disadvantage of this device is that with these radiation parameters, the mechanism of interaction with the tissue is thermal in nature and is based on the removal of excess tissue by heating it to high temperatures. The inefficiency of the energy input with this type of interaction is expressed in the fact that both a high density of pulse energy on the surface of the tissue and a high average radiation power are required. The need to maintain high power densities requires reducing the size of the spot on the surface of the fabric and, therefore, reducing to less than 2 mm the distance between the distal end of the fiber with the lateral output of the radiation and the exposure zone. At such distances, the interaction products settle on the transparent surface of the quartz cap and can lead to tool failure. Carrying out one procedure related to ablation of the prostate gland of medium size and more requires the use of two copies of a fiber instrument with lateral output of radiation and leads to an increase in the cost of the procedure. Achievements of high average radiation powers of solid-state lasers are associated with an increase in energy consumption, dimensions, as well as with well-known problems of compensating for thermal effects in the cavity of the emitter. Ultimately, this leads to the high cost of the proposed equipment. In addition, high temperatures in the exposure zone lead to damage to the underlying tissue layers, which remain in the form of a coagulated layer, which reduces the accuracy of the exposure and leads to an increase in the total radiation dose. In the considered analogues intended for the treatment of BPH, a mechanism of tissue ablation is implemented, in which the energy of laser radiation, delivered inside the tissue, sufficient to vaporize it. In this case, a relatively slow heating of the fabric, having in its composition a large amount of water, occurs to temperatures above 100 ° C, at a constant ambient pressure. Such processes are characteristic of the interaction of laser pulses of long duration with tissue.

In the case of short laser pulse durations, for visible and infrared radiation, a series of experimental and theoretical data (see SL Jakques, “How to get the best results, the best way to go, the best way to go, the better, the better, the better, the better, the better, the good for you, , 316-322 1992; Stevep L. Jacques "RoIe оf tissuе ortісs аnd рulsе durаtiop op tissеу effects duriпg high-rover lasеr irradiatiop", Arr. Ort. V. 32, No. 13, pp. 2447-2457, 1993; Albalgli, M. Dark, LT Relelmap, S. vop Roceperg, I. Itzkap, MS FeId “Rhotomysapis basis of laser ablathiop of biologic lasing”, No. 16, 1984, v. A. Oraevsku, R. O. Esepaliev, S L Jasques, F. K. Titel, "Meshapism of the issue of paying benefits with the best of the effects (UPDER of the stresses of the irradiadiop)" SPIE Proseedipgs, 2323, 250-A, Fr. 261, 1995; Titel "Mesapism of laser ablátiop for aqueuus medía irradiátad updep sopfid-stress" J. Arrl. Phs. V.78 (2), pp. 1281-1290, 1995; I. Itzkap, D. Albagli, ML Dark, L.T. Rellmap, Ch. vop Rosepberg, MS FeId "Theothermastiс basis оf short pulsed laser ablаtiop оf biologisal tissuе", Pr. Natl. Acad. Sсi. USA, v. 92, pp. 1960-1964, 1995; V. Vepugoralap, NS Nishioka, V.V. Miki &, "Thermodupamis Resource Ос Sof Biologisal Тісуесо т Pulsed Ipfаrеd-Lаser Irradiatiop", Віорхусiсal jоurаl. 70, pp. 2981-2993, 1996; A. A. Oraevsku, SL Jasques, apd F. K. Titel, "Меаsuremet оf tissuе ortіsal рrеrеtеs bу timеrеsolvеd deterіtsop оf lаsеr-iпduсеd trаpsiеpt strеss" Arr. Ort. 36, 402-416, 1997; D. Kim, M. Ye, CP. Grigororulos, "Pulse laser-ipodus ablаtiop оf aborbiпg liquids apd acustiс-trаpsiept heperetiopi", Arl. Phs. A, v. 67, pp. 169-181, 1998), indicates a significant (up to 10-fold) decrease in the energy density required to start the ablation process, even at temperatures below 100 ° C (SL Jakques, “But tissuе ortіs aff dst dоsimеtеrо fоrhothеhеmіl, rhotоthothermal , aphotomycephalic mesophilism of laser-tissuеpterastiop, "SPIE Prosediipgs, 1599, 316-322, 1992; A. Ogavevsku, SL Jacques, F. K. Titel "Meshapism оf lаsеr аlbаtiop fоr аquеusus mеdia irradiadеd updep sopfіed-strеss" J. Arrl. Phs. V.78 (2), pp. 1281-1290, 1995). The main reason for more efficient tissue removal is the development of acoustic and shock waves, accompanied by cavitation in the surface layer of the tissue, at a depth equal to half the effective penetration depth. At low absorbed energy densities, the main mechanism of sound excitation is the optoacoustic mechanism, in which the generation of acoustic waves occurs due to thermoelastic stresses during inhomogeneous heating of the tissue. When the energy value exceeds the vaporization energy, the excitation of the acoustic wave in the tissues is due to the recoil momentum arising from the evaporation of the tissue. With a further increase in energy, breakdown on the surface of the tissue is possible, accompanied by the generation of shock waves.

A criterion for the development of various processes during the interaction of radiation with tissue is the limitation of the processes occurring in the interaction zone for a time equal to the laser pulse duration t _L so that energy transfer from the interaction zone does not occur either due to heat transfer or due to the propagation of sound waves. We take for the optical interaction zone, the distance d, at which the value of the radiation energy density in the tissue falls to the level 1 / e of the value on the surface. Then the heat transfer process conditions of their restrictions in the optical zone of interaction is a condition (AA Oraevsku, SL Jasques, and F. K. Tittel, "Measuremept ° F tissue ortisal rrorerties bu time-resolved laser-detestiop ° F ipdused trapsiept stress" App. Ort. 36, 402-416, 1997): t _L «t _th = d ² / Mχ, where t _th is the time during which the heat transfer processes reach the boundary of the optical interaction zone, χ is the thermal diffusivity (for water χf = O, 15 mm / s), M is a numerical parameter related to the geometric shape of the irradiated volume (M = 4 for a disk, M = 8 for a cylinder, M = 27 for a sphere, A.L. MsKepziе, "Рсhusiсs f rrosesses Ip thermal laser-tissue ipterastiops "Rhus. Med. Viol. 35, pp. 1175-1209, 1990). Accordingly, for acoustic waves, the condition for their limitation in the interaction zone will be: t _L «t _s = d / c _s , where t _s is the propagation time of sound waves, for which they reach the boundary of the interaction zone, c _s is the speed of sound in water.

The tissue of the prostate gland during the propagation of radiation of the visible and near infrared range is a medium with a dominance of scattering processes. Determining the value of the optical zone for each wavelength requires knowledge of the tissue parameters, both during absorption and scattering of radiation, taking into account anisotropy (Stevep L. Jaques "RoIe оf tissuе effіts іnd pulsuratіop on tissu effіts duriпg high-rover lаsеr irrаdiаti ", Arr. Ort. V. 32, No. 13, pp. 2447-2457, 1993): d = (l / μ _eff ) -ln (l + k), where μ _eff is the effective absorption coefficient, k is the parameter associated with an increase in the energy density at the surface during backscattering of radiation in the medium. From the source of Stevep L. Jacques "RoIe оf tissuе ortiсs аnd рulsе durаtiop op tissuе effices duriпg high-rover laser irradiadiop", Arr. Ort. v. 32, No. 13, pp. 2447-2457, 1993 к = 3 + 5, l R _d -exp (-9,7 R _d ), where R _d is the coefficient of the total diffuse reflection of the medium. The measured values of μ _eff and R _d for prostate tissue and radiation with wavelengths of 0.532 μm and 1.064 μm are presented in A. A. Oraevsku, SL Jacques, update F. K. Tittel, Меаsuremept оf tissu рrеrеrtеtе bе timе-resеlvеd deteсt Of laser-ipdused trpsiept stress "Arr. Ort. 36, 402-416 (1997). Taking into account the shape of the irradiated zone and the characteristic value of the spot diameter on the tissue surface - 1 mm, we obtain the size of the optical interaction zone at a wavelength of 0.532 equal to d _Oj532 = l, 8 mm, and for radiation of 1.064 μm, di _{; 064} = 5, l mm.

For the radiation of Ho: YAG laser, the tissue of the prostate gland is a medium with a dominance of absorption, and the radiation is absorbed by water, which is part of the tissue, therefore d ₂ d = l / μ _a = 0.34 mm. The time, for each of the wavelengths, during which the heat propagation reaches the boundary of the optical interaction zone is: t _th o _{, 532} ⁼ 2.6 s, t _tl , _{1; 064} = 21.8 s, t _{th 2} d - 0D9 s, and for an acoustic wave, respectively: t ^ szr ^ lD μs; t _s i _{, 0b4} ⁼ 3.4 μs; t _s2 d = 0.2 μs. Thus, in the interaction of the radiation of the considered devices with the tissue, the conditions for limiting the spread of heat transfer are observed. The condition for limiting the acoustic energy in the interaction zone is met only for the emission of a Ho: YAG laser. However, a large absorption in water makes it impossible to use for ablation of the prostate gland.

In a first approximation, the degree of violation of the limitation of acoustic stresses in the interaction zone obeys the exponential law, where the boundedness factor is ~ A:

A = (l-exp (-t _L c _s / d)) / (t _L c _s / d).

Factor A, with a pulse duration equal to t _L = d / c _s , it makes sense that the peak pressures in the interaction zone reach values equal to 0.63 of the pressure values that can be achieved with deliberately short pulses. For radiation of 0.532 μm with a duration of tc «l, 0 μs, the factor A = I, which reflects the absence of energy dissipation from the interaction zone, and for pulse durations of the order of 1 ms, it has a value of about 0.001. With a further increase in the pulse duration tb, the value of factor A tends to zero. If we set the boundary value of factor A equal to OD as the boundary condition, then the duration at which the radiation pulse with a wavelength of 0.532 μm can be considered as partially satisfying the condition for limiting acoustic energy in the interaction zone should be less than 12 μs.

Also known are dye laser systems with lamp-pumped radiation, the radiation pulse duration of which lies in the microsecond range (see MR Ripse, TF Deutsch, AH Shariro, R J. Margolis, AR Oseroff, J.T. Fallop, J. A. Parish, RR Upersop, “Selective Albatiop of Atheromas Usipg and Flash-Exit Duel Lacert 465 bp”, Ros. Nat. Acad. Ssi. USA ₅ v. 83, pp. , and S. A. Prhl, "The Effects Of Shot, Pulse Eperg, Ref Rétitiop Ráté on Microsesopd Albátiop оf Gelátip Upré Water", Pr. SPIE 2391, 336-344, 1995; . Prahl, "Acustic cavitati evopts duriпg miсrosesopd irradiatiof о аqueusus solutiops ", Rros. SPIE 2970, 4-9, 1997). Due to the low output power of 1-5 W, such lasers can be used either in lithotripsy or when exposed to tissues when microscopic exposure is required, for example In angioplasty, due to the toxicity of the active media used, the high cost and complexity of operation, these devices are not widely used.

Further, solid-state lasers with a microsecond pulse duration are known that are used for crushing stones in the ICD based on different active media: on ruby in the application RU 95105018 (Berenberg V.A. et al.), Published on June 10, 1997, on Nd crystals : YAG in the application RU 93003708 (Dyakonov G.I. et al.), Published on 05/20/1995, and in patent US 5963575 (Muller G. et al.), Published on 10/05/1999, The listed devices cannot be used for ablation soft tissues, including the prostate gland, since low energy values of 0.1-0.2 J and a low pulse repetition rate Owls up to 10 Hz, do not give the output radiation power required to implement effective ablation. The average output power of these lasers does not exceed 2 W, which is clearly not enough.

Solid-state lasers with a short pulse duration are known for which the condition for limiting acoustic energy in the interaction zone is obviously fulfilled (t _L <10 ^"9 s). The closest analogue of the claimed invention is a laser installation known from US Pat. No. 5,144,630 (Lip), publ. 01.09 .1992, which, as indicated, can be used both for tissue ablation and lithotripsy, and which includes a laser emitter configured to generate pulses and containing an optical generator and non-resonant a radiation converter into the second harmonic.In this case, an installation based on an Nd: YAG or Nd: YLF laser with the conversion of the frequency of the main radiation to the second, fourth, and fifth harmonics is described in a source that reveals the closest analogue. Nonlinear crystals LBO, KTP are used to convert the radiation frequency BBO, with different ways to implement frequency conversion. The duration of the output radiation pulse lies in the range of 10 ^" -10 ^{" 6} s, and the pulse repetition rate is in the range of 1-10 Hz. It is possible to select a radiation wavelength or to use mixed radiation of several wavelengths depending on the application for medical or industrial applications.

Possible medical applications: ophthalmology, microsurgery, neurosurgery and lithotripsy. For small pulse durations, in the range from subpicosecond to picosecond durations, and high repetition frequencies of 10 ³ -10 Hz, the possibility of microsurgical intervention is proposed for ablation of tissue on the surface of the cornea, when focusing radiation with wavelengths of 0.213 μm or 0.266 μm on the surface of the cornea. At an energy density of 1.3 J / cm ² , the damage zone created by a radiation pulse with a wavelength of 0.213 μm was <1 μm in depth, and for radiation with a wavelength of 0.266 μm it was <25 μm (see Ren, Q; Gailitis, RP; Thomopsop, KP; Lip, J.T. Аblathiop оf thе corepe apd superthis rosmers uspg and UV (213 nm) solid-state laser, IEEE J. Qaptit Elop., 26: 2284-2288, 1990; R.P. Gilit Q. Rep, K. P. Thomrsop, JT Lip, G. O. Varipag. Solidid ultraviolet laser (213 pt) ablatiop оf tеorpea apd suptеtis sulagеpеpеpеpuеpеpuеpеpuеpеpuеpеdiеpеpuperi - 562, 1991). In the case of a nanosecond range of durations and a frequency range of 5-50 Hz, the possibility of ablation of corneal tissue in a tissue area with a larger area up to several millimeters is stipulated.

Short durations and low values of the energy of the radiation pulse lead to microscopic damage on the surface and small volumes of removed tissue. Such an effect may be in demand in eye microsurgery or neurosurgery, but the practical use of radiation with such characteristics is not suitable for ablation of large, up to 50 cm, tissue volumes due to the length of the removal process. An increase in the average radiation power due to a significant increase in the pulse repetition rate is reduced to a quasi-continuous mode generation leading, as in the previous case, to the increasing role of undesirable thermal effects.

Fragmentation of stones by laser radiation with a short pulse duration of 10 ^'13 -10 ^"6 s is ineffective, despite the wavelength range of the generated radiation with high absorption in the stone material, and the radiation intensity sufficient to form a laser spark on the stone surface. Shock waves, in this In this case, they are generated due to the expansion of the plasma in the laser spark, and the energy input into the resulting cavitation bubble is small, which leads to microscopic damage to the material of the stone and a decrease in the rate of fragmentation of the stones. The changes in the pulse energy under these modes of radiation generation do not provide for the generation of a shock wave with high values of pressure in the front.

Another significant factor limiting the use of the closest analogue for the stated purposes is the inability to use a fiber tool to deliver radiation to the affected area. High values of radiation intensity in a short pulse lead to fiber damage and, consequently, to the inability to carry out tissue ablation or laser lithotripsy by endoscopic methods.

SUMMARY OF THE INVENTION

The present invention is based on the task of creating a multifunctional laser unit, which could be used both for ablation of prostate tissue in the treatment of BPH, and for crushing stones in the treatment of ICD.

This problem is solved in that in a laser apparatus for tissue ablation and lithotripsy, including a laser emitter, configured to generate pulses and containing an optical generator and an extra-resonant radiation transducer to the second harmonic, according to the invention, the laser emitter generates radiation pulses in the duration range 0, l ÷ 10.0 μs, the optical generator is made on the basis of a Nd: YAY ₃ crystal with Q switching with a broken gate total internal reflection and a fiber delay line between the optical generator and a two-pass optical amplifier based on a Nd: YAY ₃ crystal, an optical insulator is installed, the non-resonant radiation converter is made with a conversion efficiency of at least 30%, and an attenuator is installed on the radiation input into the fiber instrument.

Preferably, the non-resonant radiation converter to the second harmonic is equipped with a thermal stabilization system including a thermostat with a non-linear crystal installed in it. It is also preferable that the non-resonant transducer of radiation into the second harmonic be made with the possibility of realizing the 90 ° phase-non-critical angle synchronism with focusing the radiation into a nonlinear crystal.

In this case, as a nonlinear crystal in the converter, in a particular case, an LBO crystal (LiB ₃ Os) or a KTP crystal (KTiOPO ₄ ) can be used.

Unlike well-known analogues, each of which can only be successfully used to affect tissues of one structure, the claimed device allows you to effectively act on tissues of various structures: soft tissues and hard calculi, by providing an average output radiation power in the range from 1 W to 100 W at a microsecond pulse duration and can be used to treat the two most common diseases in urology (BPH and ICD).

The effectiveness of the effect of laser radiation on tissue depends not only on the choice of wavelength with the corresponding absorption coefficient, as in the closest analogue, but also on a combination of other radiation parameters (including wavelength, duration, energy and pulse repetition rate). The design of the claimed device provides for the implementation of the microsecond range of pulse durations and the conversion of radiation into a second harmonic (duration and wavelength of radiation). In combination with pulse energy values in the range 0.1-1.0 J and pulse repetition rates up to 100 Hz, the radiation parameters allow ablation of the maximum volume of soft tissues (in particular, up to 100 cm ³ of prostate tissue) while preventing the dissipation of laser radiation energy from the interaction zone during the pulse. At the same time, the obtained radiation parameters are sufficient to obtain the pulse energy, which, when exposed to solid calculi, provides the development of cavitation effects and the generation of pressure> 100 KBr at the front of the shock wave that develops during the collapse of a cavitation bubble. The exposure times for ablation of the prostate gland are less than 15 minutes, and for fragmentation of the stones less than 2 minutes, leading to a decrease in the duration of surgery in comparison with other methods.

In addition, the microsecond duration of a radiation pulse with an energy of up to 1 J allows avoiding the destruction of the fiber used to deliver radiation to the operation area, which, in contrast to the radiation of the nanosecond and picosecond range of durations in the prototype, allows using endoscopic access and applying minimally invasive treatment technologies. Tissue ablation using the claimed device is carried out when exposed to radiation with an output power of 30 W or more, at a second harmonic wavelength. The destruction of solid stones is carried out by the contact method under the influence of mixed radiation of two wavelengths: the main radiation and the second harmonic with a pulse energy of up to 0.2 J and a pulse repetition rate of 10 Hz. The average output radiation power in this mode of exposure is up to 2 W, and the fragmentation of the stones is due to the shock waves generated by the collapse of cavitation bubbles on the surface of the stone. It is also possible to use the claimed device for contact dissection of tissue when, in order to increase the hemostatic effect, two mixed wavelengths of the main radiation and the second harmonics, and the average output power of the radiation during contact dissection of the tissue can be up to 100 watts.

Brief Description of the Drawings

The invention is further explained in more detail with a specific example of its implementation with reference to the accompanying drawings, in which:

- in FIG. 1 is a block diagram of an installation;

- in FIG. 2 is an optical diagram of a radiator.

BEST MODE FOR CARRYING OUT THE INVENTION

In the preferred embodiment shown in the drawings, the laser apparatus includes a laser emitter comprising two quantrons 1 and 3 with active elements of Nd: YAY crystals ₃ 26 and 34 installed respectively in an optical oscillator and a two-pass optical amplifier, which are described in more detail are described below. The active elements are pumped using power supplies 9 and 10. Q-switching in the optical emitter of the emitter is carried out by a modulator 2, which is a gate on the impaired total internal reflection (gate ATR 29). The radiation is converted to the second harmonic by a nonlinear crystal installed in the thermostat 4. The ratio of the energies of the main radiation and the energy of the second harmonic of the laser pulse is changed by means of replaceable attenuator filters using the attenuator control unit 5. Measurement and control of the radiation output parameters is performed using component group 6, on based photodiodes. The cooling system 7, with a closed-loop air-water heat exchanger, cools the quantrons 1 and 3. The power supply units 9 and 10 of the pump lamps, the Q-switch 2, thermostat 4, attenuator 5, the control and measuring group of components 6 and the control unit 8 of the cooling system work 7 is controlled by a controller 12, which is electrically connected to the control units of these devices. For ease of use, the device can also be equipped with a touch monitor 11 both to control the operation of the installation and to display the signal of the surgical endovideo camera, the processing of which is carried out by unit 13. The video signal processing unit 13 serves not only to display the course of the intervention in real time on the monitor screen 11, but can also record video on an external mobile storage medium for archiving and subsequent analysis.

In FIG. Figure 2 shows the optical scheme of the laser emitter of the installation, providing the required parameters of the output radiation. Achieving an effective result of using the device for the treatment of the diseases mentioned above requires the joint solution of several technical problems.

The main radiation parameters that need to be provided are: a) obtaining the required laser pulse duration lying in the microsecond duration range (from 0.1 μs to 12 μs); b) achieving, in the specified range of durations, the values of the energy of the laser pulse, preferably from 0.8 J or more; c) implementation of conversion to the second harmonic of the main radiation with an efficiency of 30% or more.

The laser pulse is generated in an optical generator, which, in the example shown in FIG. 2, includes a blind mirror 21, a fiber delay line 22, a polarization isolation based on a Fresnel rhombus 25, an Nd: YAY ₃ crystal 26, a lens 28, an ATR shutter 29, intended for active modulation of the Q-factor of the resonator (A. A. Oraevsku, SL Jacques, F. K. Titel “Meshapism of laser ablattiop for acuéus medía irradiadép updepcopfid-stréss” J. Arl. Rhs. 81, 8. 1995; I. Itzkap, D. Albagli, ML Dark, L.T. Relelmap, Ch. Vop Rosepberg, M.S. FeId "Theothermastiс basis оf shortt pulsed laser ablаtiop оf biologisalis sue ", Rros. Natl. Assad. Ssi. USA, v. 92, pp. 1960-1964, 1995), and an output mirror 30. Mirrors 27 and 33 are 45 degrees with an optical axis, have a reflection coefficient of 99.9% and serve to rotate the optical axis in order to reduce the overall dimensions of the installation. In the particular case of the invention, an Nd: YAlO ₃ 26 crystal of dimensions 06.3x100 mm can be used as an active element, a spherical mirror 21 can be used as a deaf mirror, with a reflection coefficient at a wavelength of 1.0796 μm equal to 99.9%, and the output mirror 30 can be a plane-parallel plate 1 mm thick.

An increase in the pulse duration is achieved by changing the effective cavity length due to the use of a fiber delay line 22. The fiber delay line for changing the temporal characteristics of laser radiation was first used by E. M. Dianov et al. (E. M. Dianov, C. K. Isaev, L. S. Kornienko , N.V. Kravtsov, V.V. Firsov. “Laser with a light guide”, “Quantum Electronics”, 3, Ni-I l, pp. 2503-2505, 1976; EM Dianov, CK. Isaev, L . S. Kornienko, N.V. Kravtsov, V.V. Firsov. "Combination laser with a fiber-optic resonator", "Quantum Electronics", 5, X ° 6, p. 1305-1309, 1978), and further studies were performed in S.K. Isaev, LS Corporation, NV Krávtsov, N.M. Naumkıp, W. G. Skuibip, VV Firsóv YU. P Yatsepko. "Model self-loskipg solid-state lasers with lopg resopators." J. Ort. Soc. Am., V. 68, No. 11, pp. 1621-1622, 1978; A.M. Zabelin, CK. Isaev, L.S. Kornienko. "Mode selection and frequency tuning in a laser with a fiber-optic resonator", "Quantum Electronics", 8, X ° 12, pp. 2695-2697, 1981; Masataka Nakazawa, Masamitsu Tokuda, Nawa Ushida. "Lasipg shasteristics оf а Nd ³⁺ : YAG laser with а lopg ortisal-fiber resopator." J. Ort. Soc. Am., V. 73, JVabb, pp. 838-842, 1983; EAT. Dianov, A.M. Zabelin, CK. Isaev, L.S. Kornienko. "Ring garnet laser with a light guide", "Quantum Electronics", 11, X ° 8, pp. 1509-1510, 1984; EAT. Dianov, CK. Isaev, L.S. Kornienko, V.V. Firsov, Yu.P. Yatsenko. "Synchronization of SBS components in a laser with a fiber-optic resonator", "Quantum Electronics", 16, XaI, pp. 5-6, 1989.

In particular, in this example, a quartz fiber with a quartz core diameter of 300 μm and a numerical aperture of NA = 0.22 can be used. The end face of the fiber facing the deaf mirror 21 is located from it, preferably at a distance equal to the diameter of the quartz fiber core. The coordination of the numerical aperture of the radiation emerging from the other end of the fiber delay line 22 with the aperture of the active element 26 is carried out by the lens 23 with a focal length equal to 18 mm To prevent the generation of radiation in the resonator, which is formed between the fiber end of the delay line 22 and the output mirror 30, and therefore to obtain coupled resonators, a polarization isolation 25 is used, consisting of a Fresnel rhombus 24.1, rotated by an angle of 45 ° relative to the optical axis, and a polarizer 24.2. The radiation at the output of the active element 26 is focused on the surface of the output mirror 30 with a lens 28, with a focal length of 98 mm

The increase in pulse energy in the inventive installation is provided by a double pass through an optical amplifier 34, assembled on the basis of a Nd: YAY ₃ crystal. To prevent the influence of the amplifier 34 on the optical generator, an optical insulator 32 is installed between them, which may include a Faraday rotator, a quartz rotator, and two polarizers from Glan prisms. Coordination of the apertures of the insulator 32 of the amplifier 34 with the aperture of the optical generator is carried out by the lens 31. The double passage of radiation through the optical amplifier 34 is provided using a spherical mirror 35.

In the particular case, the optical amplifier 34 can be assembled on the basis of an Nd: YAlO ₃ crystal with dimensions of 08x100 mm, lens 31 can have a focal length of 120 mm.

Lens 36 is used to focus the laser radiation reflected by the optical insulator 32 into a non-linear crystal 37 mounted in the thermostat 4. The lens system 38 and 41 is designed to introduce radiation into the fiber tool 42 attached to the installation. Attenuator 39 with interchangeable filters mounted between the lenses 38 and 41, is intended to change the ratio of the energies of the main radiation and the second harmonic. A beam splitter plate 40, mounted behind the attenuator 39, is designed to reflect part of the radiation on the measuring group of components 6, consisting of energy meters 44 and 45 and a dichroic mirror 43, which provide control and management of the output radiation parameters. Installation works as follows.

The laser cavity between the mirrors 21 and 30, operates in the regime of active Q-switching and generates radiation pulses of the microsecond range of durations. The pulse width at the output is determined primarily by the effective cavity length and radiation loss during propagation in the fiber delay line. The value of the duration of the laser pulse at the output of the mirror 30 can be controlled by the length of the fiber delay line 22. The change in the gain of the active medium or the loss in matching the apertures in the cavity, when the pump level of the active element 26 changes, cause relatively small changes in the pulse duration depending on the pump level. For example, for a fiber delay line of fiber with a diameter of a quartz core of 300 μm with a length of 50 m, the half-width of the pulse at the output of the optical generator is 0.98 μs for a pump energy of 35 J and 0.8 μs for a pump energy of 44 J. the length of the fiber delay line in the generator, one should take into account the possibility of changing the duration of the radiation pulse (for example, an increase of 2–3 times) upon amplification in the optical amplifier 34 due to the displacement of the leading edge of the pulse propagating through the medium with gain saturation I am.

The polarization isolation 25 based on the Fresnel rhombus serves to suppress spurious generation of radiation in the resonator formed between the output mirror 30 and the polished fiber end of the fiber delay line 22 and prevent the formation of coupled resonators. The resonator Q-factor is modulated by an ATR shutter 29, which has an open transmission of 95% at a wavelength of 1.0796 μm of generated radiation. The pulse energy behind the output mirror 30 is 130 mJ when pumped at 35 J and 180 mJ when pumped at 44 J. An optical amplifier 34 is used to increase the laser pulse energy, and the radiation passes through it twice due to reflection from a spherical mirror 35. Spherical mirror 35 with a radius of curvature equal to 100 mm, it is preferable to set in such a way as to compensate for the return passage of the changes in the radius of the front of the laser beam caused by a thermal lens in the amplifier 34.

The radiation propagating in the opposite direction is polarized at an angle of 90 ° to the original horizontal plane, and its plane of polarization is perpendicular to the transmission axis of the polarizer — the Glan prism of the isolator 32. The transmittance of the isolator for radiation of the desired polarization is 92%, and the degree of isolation of the reflected radiation is 38 dB.

The energy of the radiation reflected by the Glan prism can reach values of the order of 0.6 ÷ l, 2 J and have a duration of the order of 2.0-3.0 μs, with a beam aperture of about 8 mm. The radiation power density in such a beam has a value of the order of 1.0 MW / cm ² . Achieving effective radiation frequency conversion requires large power densities. To this end, the radiation is focused into a nonlinear crystal 37, in which the 90 ° phase-free synchronism is realized. On the length of the radiation wave of an Nd: YAlO ₃ laser, synchronism that is not critical in angles is possible, for example, for KTP or LBO crystals, when they are heated. The experimentally measured temperature value for the KTP crystal is 54 ⁰ C (Abrosimov CA., Grechin C.G., Kochiev DG, Maklakova H.Yu., Semenenko V. “GBG in a KTP crystal of single-pulse microsecond pulses)), Quantum electronics , 31, N ° 7, pp. 643-646, 2001), for the LBO crystal according to published data in the range 145 ⁰ C - 155 ⁰ C. The radiation is focused by a lens 36 having a focal length of 120 mm into a non-linear crystal 37, which is thermally stabilized with accuracy ± 0.1 ° C. The radiation conversion efficiency under these conditions was about 40%, and the radiation energy at a wavelength of 0.54 μm at the output of the transducer ~ 0.4 J. The system for introducing radiation into the fiber, consisting of lenses 38 and 41, transfers the image of the laser radiation spot from the waist in a nonlinear crystal to the plane of the input end of the fiber tool with a decrease

42. The system is optimized both with respect to spherical and with respect to chromatic aberrations for radiation of two wavelengths.

Part of the laser radiation is assigned to the plate 40 for measuring the output energy of the radiation pulse at each wavelength with energy meters 44 and 45, which are connected by feedback with the controller, for monitoring and controlling the output parameters of the radiation. It is possible to change the ratio of the shares of radiation energy at each wavelength in the output radiation energy, depending on the current task of practical use. An increase in the average power and hemostatic properties of radiation during contact dissection of tissues can be obtained by leaving the unconverted main radiation in the laser beam. For use in lithotripsy, the optimal combination of parameters of a radiation pulse with different wavelengths can be the following: maximum total pulse energy of 200 mJ, with radiation of 0.54 μm not more than 60 mJ, radiation 1.0796 μm not more than 140 mJ. The attenuator 39, consisting of replaceable filters, serves to select the desired ratio of radiation energies at each of the wavelengths. Three combinations of transmission of the system from the filters with respect to the radiation of 1.0796 microns are possible: 1 - 100% transmission, for contact dissection of tissues with an increased level of tissue coagulation and hemostasis; 2 - transmission within 70-80%, in the mode of operation of the lithotripter; 3- lack of transmission, in ablation mode with minimal tissue coagulation.

Preliminary experiments on the effect of radiation of microsecond duration on soft tissues of the ureter wall showed the possibility of ablation in a selected range of durations. When exposed to ureteral tissue, with a spot diameter on the tissue surface of 0.3 mm, with values of energy density of 15 J / cm ² was observed start of tissue removal with the formation of a crater. With an increase in energy density to 35 J / cm ² and exposure to 500 pulses, the depth of the crater was 0.5 mm, and the layer of coagulated tissue did not exceed 0.4 mm in thickness. Obviously, the low radiation energy in the pulse does not provide the required tissue removal rate. An increase in tissue removal efficiency requires an increase in both the pulse energy and the average radiation power at the second harmonic wavelength.

As already noted, tissue ablation using the claimed device is carried out when exposed to radiation with an output power of more than 30 W, at a second harmonic wavelength. The impact on the tissue is carried out remotely, the diameter of the spot on the surface of the fabric is 1 mm, and the energy density on the surface of the fabric is more than 35 J / cm. Contact tissue dissection is possible, where, in order to increase the hemostatic effect, the tissue is exposed to the mixed radiation of the first and second harmonics. The average radiation power during contact dissection of the tissue at the output of the distal end of the fiber tool can be more than 60 watts. The destruction of solid stones is also carried out by the contact method, when the distal end of the fiber tool comes into contact with a quartz core diameter of 300 μm, with the surface of the stone. The impact in this case is carried out by mixed radiation of two wavelengths with a pulse energy of up to 0.2 J, and a pulse repetition rate of 10 Hz. The average radiation power at the output of a fiber tool in this exposure mode is 2 watts. Fragmentation of stones in this case is carried out due to shock waves generated during the collapse of cavitation bubbles on the surface of the stone.

It should be noted that the above example is provided solely for a better understanding of the essence of the claimed invention and cannot be construed as limiting the scope of claims. The specialist will be clear and other special cases of the invention (in particular, changing the pulse duration in the claimed range from 0.1 μs to 10 μs - can be achieved by changing the length of the fiber delay line 22, in addition, it is possible to carry out polarization isolation on the basis of a phase plate with a thickness of λ / 4, the use of other nonlinear crystals, etc.) that do not go beyond the scope of the claimed legal protection, determined solely by the attached formula inventions.

Industrial applicability

The device according to the invention can be successfully used in surgical urology for the surgical treatment of benign prostatic hyperplasia (in tissue ablation mode) and urolithiasis (in lithotripter mode). For the manufacture of the installation, individually known structural elements can be used, which, when assembled, are combined in accordance with the claimed arrangement described above with specific examples.

Claims

CLAIM

1. A laser apparatus for tissue ablation and lithotripsy, comprising a laser emitter configured to generate pulses and comprising an optical generator and an extra-resonant radiation transducer to the second harmonic, characterized in that the laser emitter generates radiation pulses in the duration range 0.1 ÷ 10.0 μs, the optical generator is based on an Nd: YA10z crystal with Q-switching by a gate on the disturbed total internal reflection and a fiber delay line between the optical generator and a two-pass optical amplifier based on an Nd: YAlO ₃ crystal, an optical insulator is installed, an non-resonant radiation converter is made with a conversion efficiency of at least 30%, and an attenuator is installed at the input of the radiation into the fiber instrument.

2. The laser installation according to claim 1, characterized in that the non-resonant radiation converter to the second harmonic is equipped with a thermal stabilization system including a thermostat with a non-linear crystal installed in it.

3. Laser installation according to claims 1 or 2, characterized in that the non-resonant radiation converter to the second harmonic is made with the possibility of realizing a 90 ° synchronism that is not critical in angle with focusing the radiation into a nonlinear crystal.

4. Laser installation according to paragraphs. 1 or 2, characterized in that the LiB ₃ Os crystal or KTiOPO ₄ crystal is used as a nonlinear crystal in the non-resonant radiation converter to the second harmonic.