WO2001013810A1 - Procede et systeme permettant de souder des tissus au moyen d'un faisceau laser - Google Patents

Procede et systeme permettant de souder des tissus au moyen d'un faisceau laser Download PDF

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Publication number
WO2001013810A1
WO2001013810A1 PCT/US2000/022726 US0022726W WO0113810A1 WO 2001013810 A1 WO2001013810 A1 WO 2001013810A1 US 0022726 W US0022726 W US 0022726W WO 0113810 A1 WO0113810 A1 WO 0113810A1
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tissue
laser
welding
radiation
elements
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PCT/US2000/022726
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English (en)
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Alexandr V. Kuklin
Alexandr V. Rezsov
Evgeny A. Karpov
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Miracle Medical/Surgical Technologies Inc.
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Priority to AU67862/00A priority Critical patent/AU6786200A/en
Publication of WO2001013810A1 publication Critical patent/WO2001013810A1/fr

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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B18/18—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by applying electromagnetic radiation, e.g. microwaves
    • A61B18/20—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by applying electromagnetic radiation, e.g. microwaves using laser
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
    • A61B17/00491—Surgical glue applicators
    • A61B2017/00504—Tissue welding
    • A61B2017/00508—Tissue welding using laser

Definitions

  • the present invention relates to methods and systems for joining tissue portions.
  • the invention relates to methods and systems for joining tissues by the use of lasers, as in laser tissue welding.
  • the surgical suture is presently the most common means used for connecting adjacent or overlapping portions of biological tissue.
  • Suturing provides a reasonably flexible technology, that can be adapted almost for any conditions arising in tissue. This technology is relatively inexpensive, reliable and accessible. Nevertheless, the use of sutures can result in tissue damage, particularly when the needle is passed through tissue and the knots are initialized. Moreover, since the suturing material is foreign to the organism, the use of sutures can lead to inflammation, as well as granuloma, scars and stenoses. Moreover, it is recognized that sutures do not give tight connection of tissue, and the overall success of the procedure can be dependent on the surgeon's individual practices and skills.
  • brackets and clips Connecting tissue with brackets and clips can provide more stable and secure results, since the force of tissue compression is determined by the seaming device.
  • the use of brackets and clips has some restrictions as well, particularly in terms of the thickness and integrity of tissue.
  • a further advantage of brackets and clip is their usefulness with endoscopes and laparoscopes.
  • Several of the defects associated with sutures apply to brackets and clips as well, however, including the relatively large force needed to tighten the brackets, and the corresponding technical limitations that exist on the minimum size of such suturing devices.
  • the use of laser beam tissue "welding" has been applied as well, involving the application of laser energy for tissue connection.
  • a laser having a wavelength of l ⁇ m to 1.4 ⁇ m, average radiation power 5 W to 30 W, beam diameter 0.1 mm to 0.3 mm and exposure time 0.05 s to 0.2 s (20).
  • US Patent No. 5,281,211 (Parel, et al., "Noncontact Laser Microsurgical Apparatus”) describes a noncontact laser microsurgical apparatus and method for marking a cornea of a patient's or donor's eye in transplanting surgery or keratoplasty, and in incising or excising the comeal tissue in keratotomy, and for tissue welding and for thermokeratoplasty.
  • an adjustable mask pattern is inserted in the optical path of the laser source to selectively block certain portions of the laser beams to thereby impinge only selected areas of the cornea.
  • the comeal tissue may be heated only sufficiently to cause shrinkage of the tissue in selected areas to alleviate astigmatism and/or corneal refractive error.
  • the apparatus includes a pulse-controlled dye delivery system which may be coordinated with the delivery of laser energy to predetermined tissue.
  • the pulse-controlled dye delivery system includes an ejection head capable of ejecting drops of liquid dye with the diameter of each drop being less than two hundred microns.
  • the dye is responsive to the wavelength of energy delivered by the laser performing the surgery to convert the laser energy from the surgical laser to tissue thermal energy.
  • the effects of laser beams on a living body will depend on numerous factors, for example, wavelength, energy or power intensity, and difference of waveform such as continuous wave or pulsative wave.
  • the effects of a laser beam can be classified into four regions, namely, the photochemical, thermal, photoablative and electromechanical regions.
  • the thermal region is used as a laser scalpel. See, for instance, US Patent No. 5,407,443 (Kobayashi, et al.) which describes a laser operation device for insertion into a region to be irradiated and which is optimally used as an intraocular device to treat cataracts, glaucoma or the like.
  • Kobayashi et al. describe the manner in which the temperature of tissue irradiated by a laser is elevated because of a rapid increase of molecular temperature. Since the depth reached by the energy of the laser beam or the temperature of the tissue attained is determined by the combination of wavelength, irradiation time and irradiation area of the laser beam, control is possible including the suppression of cell activity, as well as melting, coagulation, carbonization, and evaporation of proteins. Further, the Kobayashi et al.
  • this patent describes the manner in which argon and other visible light lasers tend to produce less than satisfactory effects.
  • the output of argon lasers and the like was found to be heavily absorbed by blood and subject to substantial scattering within the tissue These effects combined to create a narrow therapeutic "window" between a proper amount of energy necessary for laser fusion and that which induces tissue carbonization, particularly in pigmented tissues and tissues that have a high degree of vascularization.
  • the patent remarks that the development of new solid state laser sources have made prospects brighter for efficient, compact laser fusion systems suitable for clinical use.
  • Such systems typically employ rare, earth-doped yttrium aluminum gamet (YAG) or yttrium lithium fluoride (YLF) or yttrium-scadium-golilinium-garnet (YSGG) lasers.
  • YAG yttrium aluminum gamet
  • YLF yttrium lithium fluoride
  • YSGG yttrium-scadium-golilinium-garnet
  • the Sinofsky patent is said to address a need for better laser fusion systems that can accurately control the formation of an anastomotic bond to avoid thermal damage and achieve optimal results.
  • high-energy radiation e.g., having a power density of greater than about 1 W/cm 2
  • a thermal effect occurs.
  • radiation power density increases the tissue becomes hotter.
  • the configuration of many types of macromolecules is changed (6), which, together with dehydration, results in varying effects on the viscosity, density, thermal and optical properties of tissue.
  • tissue begins to dehydrate and becomes coagulated, after which it is thermolized and carbonized (2, 3).
  • the average power radiation density values for achieving these processes are, approximately 10 W/cm 2 to 50 W/cm 2 for dehydration and coagulation, 50 W/cm 2 to 1000 W/cm 2 for thermolysis and carbonization start-up (4).
  • Complete carbonization is reached at temperatures about 200 °C to 220°C, and that the carbonized framework burns up at 400°C to 450°C.
  • Certain objective criteria of the effectiveness of thermal tissue welding include: the firmness of the tissue connection, the duration of the welded suture (e.g., as compared to tissue healing kinetics), and the area of tissue affected (e.g., the size of a zone where tissue dies away under thermal influence).
  • the quality of welding depends on radiation features (e.g., wavelength, power, distance, spectral characteristic of radiation source), the exposure time, and properties of the tissue itself.
  • Tissue can be considered as a flat layer with constant thermophysical properties (32).
  • the structure of volumetric absorption of radiation can be determined on the intensity of dropping radiation and the reduction factors in a tissue accounting absorption and unitary dispersion.
  • the heat conductivity for a received three- dimensional axis-symmetrical problem was solved analytically by decomposition on Besets functions.
  • Various types of lasers were analyzed, including a C0 -laser (wavelengths 10.6 ⁇ m), an argon laser (0.5-0.6 ⁇ m), its depth of penetration of a beam being essentially larger, than for a C0 -laser, but its radiation being strongly absorbed by hemoglobin), and a Nd-YAG laser (wavelength 1.06 ⁇ m, it's absorption being 4-5 time less than that for a argon laser, thus providing the ability to achieve tissue warming up with a narrow beam penetrating up to several mm in the depth).
  • the authors evaluate experimental data up to the temperature 75°C. At temperatures above 58°C coagulation begins, while the processes of evaporation (at temperatures above 100°C), carbonization and burning out of carbonized sites at further increase of temperature were not considered (32).
  • the tissue is also considered as an axis-symmetrical flat layer.
  • the values of thermophysic parameters of a tissue were varied according to the non-uniformity of its structure and with regard to coagulation, evaporation and carbonization.
  • a three dimensional, axis-symmetrical calculation of thermal fields in tissue is considered in Zweig et al. (34), using a C0 2 laser.
  • the evaporation of water contained in tissue and heat and mass exchange were considered in a biphase environment.
  • lasers are also commonly used for ablating, rather than joining, tissues. See for instance, Wojcik, et al., US Patent No. 5,860,968 ("Laser scanning method and apparatus"), which describes the manner in which carbon dioxide laser beam has been used for many years in the ablation of living tissue.
  • the laser causes a temperature rise in the tissue primarily due to the absorption of laser radiation by water in the tissue. When this water is heated to its boiling point, it causes an explosive ablation of the surrounding tissue.
  • heat transfer to adjacent tissue may cause thermal damage, resulting in tissue necrosis, desiccation, or carbonization (“char”) that hinders further ablation until the "charred” tissue is removed.
  • the beam is moved by manipulating conduit through which the beam travels, with the proximal end of the conduit being held in fixed alignment with the laser energy source and the distal end of the conduit being moved in a predetermined pattern.
  • the laser energy source is pulsed at a predetermined power level and for a predetermined frequency and duration, and the conduit is moved at a predetermined speed in coordination with the pulses of laser energy to uniformly scan the laser beam over the target area and achieve uniform tissue ablation in the target area.
  • the laser delivery system is said to include a generator of laser energy, a guide for conducting the laser energy to a target site; and a device for scanning the laser energy at the target site, the scanning device comprising a conduit for conducting laser energy; and a device for moving the conduit in a predetermined pattern to uniformly scan the target site with laser energy and achieve a uniform and thorough ablation of the target tissue at the target site.
  • the laser generator is configured to generate pulses of laser energy of a predetermined power, frequency and period or duration
  • the moving device is configured to move the distal end of the conduit at a predetermined continuous speed in coordination with the frequency and duration of the laser energy pulses so that the laser energy is delivered uniformly to the target site.
  • Figures la and lb show alternative cross-sectional schematic views of laser formed elements for use in the present invention.
  • Figure 2a shows a variety of different laser point elements in side elevation and cross section according to the present invention
  • Figure 2b shows a variety of geometrical combinations (i.e., patterns) of laser point elements according to the present invention.
  • Figure 3 shows a chart of the spectral dependencies of transmission coefficients.
  • Figure 4 shows a schematic view of a system of a multispectral laser welding system.
  • Figure 5 shows schematic views 5a, 5b and 5c of a laser welding system for se in the present invention.
  • Figure 6 shows a chart of the spectral characteristics of quartz plates.
  • Figure 7 shows an optical scheme of an MPS-2000 spectrophotometer.
  • Figure 8 shows an optical scheme of a U-3400 spectrophotometer.
  • Figure 9 shows an optical scheme of a multitarget unity RTA-2000.
  • Figure 10 shows an optical scheme of an IR-435 spectrophotometer.
  • Figure 11 shows a chart of the reflection, transmission and absorption indicies of two-layer tissue samples.
  • Figure 12 shows a chart of the absorption index of compressed tissue.
  • Figure 13 shows a chart of the spectral characteristics of tissues in the IR- range radiation.
  • Figure 14 shows a chart of the results of calculations for unfocused laser beams.
  • Figure 15 shows a chart of the results of calculations for focused laser beams.
  • Figure 16 shows a chart of the characteristic laser beam power distribution curve.
  • Figures 17 through 21 show various microphotographs of the effects of laser radiation on tissue.
  • Figure 22 shows a schematic view of a system of this invention.
  • the present invention provides a method and system for joining adjacent tissue portions using lasers, the method comprising the steps of forming a plurality of non-contiguous laser formed elements along a weld line, the elements being positioned in a predetermined pattern with respect to each other and each having a predetermined cross-sectional configuration.
  • the elements are independently created in order to achieve a desired absolute and relative extent of denaturation, coagulation, and/or carbonization within the tissue, and particularly within the individual elements themselves.
  • the effect of laser energy on tissue e.g., under conditions of increasing laser energy and/or exposure time, will be considered to involve the following steps, in approximate order of occurrence (and corresponding with increasing tissue temperatures): protein denaturation, dehydration, coagulation, thermolysis, and carbonization.
  • the net effect on tissue can be assessed by determining the absolute and/or relative extent of denaturation, coagulation, and carbonization, since dehydration and thermolysis are more akin to the processes involved, as compared to the detectable result achieved.
  • the method comprises the steps of
  • tissue portions 1) contacting two or more tissue portions, in a manner that provides respective surfaces of the tissues in direct or indirect contact with each other, such that the contacted tissue portions provide at least one surface accessible to a source of laser energy;
  • the tissue portions can be directly or indirectly "contacted” in any suitable manner, e.g., they can be provided in a directly overlapping or abutting relationship with respect to each other and/or they can be indirectly contacted by the use of a secondary material, e.g., an intermediate or surrounding layer of an exogenous treated natural tissue, for instance, that is itself susceptible to laser radiation in order to form an integral bond with tissue portions to be welded.
  • a secondary material e.g., an intermediate or surrounding layer of an exogenous treated natural tissue, for instance, that is itself susceptible to laser radiation in order to form an integral bond with tissue portions to be welded.
  • the predetermined weld line pattern is a primary pattern selected from the group consisting of straight lines, zigzag, wave forms, and the like, examples of which are shown in Figure 2b.
  • the pattern can include one or more secondary patterns (also shown in Figure 2b, e.g., with adjacent, grouped elements in the form of small geometric patterns), the groupings themselves preferably being formed in predetermined positions along a weld line.
  • the term "primary pattern” will refer to the position of a element within a weld line, e.g., along a point forming the overall weld between two tissue portions, while the term “secondary pattern” will refer to the position of a element within a subgroup of adjacent elements, e.g., to form a secondary structure or geometric pattern that covers a larger area than any single element, but a smaller area than the weld line itself.
  • the primary and secondary patterns can be provided in any suitable manner, e.g., by the use of pattern-imposing masks, pattern positioned solder, and/or in a controlled manner by controlling the location and other relevant parameters of the laser head itself.
  • an apparatus for use in the present system preferably includes a hand-held or automated instrument, e.g., a pen-like device adapted to be held by the surgeon in the course of applying the laser energy.
  • the tip of the "pen” delivers the laser energy (impulse) to the tissue, and can be used to create either a single point (element) or patterns of such points in the sutured tissue.
  • the tip of such a device can be permanent or changeable, e.g., by physically changing the tip itself or by altering computerized instructions thereto, in order to create different point patterns.
  • Laser tips of this invention can also have a pre-defined point pattem such as an arc, triangle, a plurality of points in a row, or a single point.
  • the surgeon can use the impulse delivery device in a variable and controllable mode and/or can lock the device in one or more fixed positions in order to move it around the tissue.
  • the cross-sectional configuration of the elements is independently selected from the group consisting of elements of a generally cylindrical, multilateral, pyramidal, conical or egg shaped configuration.
  • the elements can be either solid through their entireties, or the form of cavities within (partially or wholly through) the tissue.
  • the elements can independently extend partially or fully through one or both portions of adjacent tissue (and/or into or through intermediate layers as described herein).
  • the elements are formed substantially at or near the interface between two tissue portions, so as to minimize the impact and possible trauma to surrounding tissue.
  • Tissue impact can be controlled and coordinated between individual elements, so as to provide an optimal extent and balance of denaturation, coagulation and/or carbonization.
  • denaturation the links between complex spiral molecules of protein are altered, transforming the spirals into a fibrous structure having strong links between the newly formed fibers.
  • the method and apparatus of the present invention can be applied to a variety of laser welding approaches. Such parameters as power level and exposure time can be selected to obtain suitable element structures, e.g., resembling a "hollow clinch", in the form of a substantially hollow element.
  • the method of forming a weld of this invention can involve the use of laser energy to form one or more hollow elements each surrounded by a zone of denaturated protein. Given their numbers and relative positions along the weld line, the elements can collectively provide a suture weld line having the desired toughness and stability, and without the need to provide carbonized tissue.
  • An alternative embodiment, shown in Figure lb, involves the laser formation of one or more carbonic elements between the tissue portions.
  • a substantially cylindrical coagulated zone can be provided that surrounds the carbonized framework, providing suture firmness that can be even higher that of the first embodiment above.
  • the element can be formed at substantially the interface between the tissue portions, rather than through the whole depth of the portions, thereby further reducing trauma .
  • tissue samples can be quite different, even within different portions of the same organ, e.g., in terms of temperature at the zone of protein denaturation, the degree of compression of welded tissue samples, and the like.
  • the denaturation reaction proceeds slowly at tissue temperatures below about 60°C and increases significantly as temperatures exceed about 70°C. For instance, using calculations based on the Arrenius equation, it can be determined that at 60°C the speed of reaction equals 5 s ' at 70°C - 5.5xl0 3 s "1 and at 80°C - 4xl ⁇ V.
  • the combination of short exposure times with high power density will typically be less preferred, since to obtain firm connection of tissue portions the denaturation process should generally be completely terminated in a rather large zone.
  • the temperature of the reaction is therefore preferably uniform in the whole volume under the zone surface and enough high to intensify the denaturation process.
  • the present invention also provides the ability to control the extent and type of tissue impact within and/or surrounding individual elements, and in a preferred embodiment to diagnose such impact in the course of the procedure itself, so as to permit further control options.
  • the method can be used to provide elements having an optimal combination of zones of tissue (or components of the tissue) that has been denatured, coagulated, and or carbonized.
  • an element is provided in a manner that has a cavity in the form of a substantially hollow core, surrounded by a substantially concentric zone of carbonized tissue, which itself is surrounded by a ring of coagulated tissue and then a ring of denatured tissue, or more preferably which is surrounded by substantially denatured tissue.
  • the word “denatured” and inflections thereof will refer to tissue in which the tertiary structural characteristics of its proteins are detectably altered, while the word “coagulated” and inflections thereof will refer to the conversion of the tissue or its components (e.g., cells or cellular structures) into a solid, semi-solid or gel-like mass.
  • the area of coagulated tissue is preferably minimized, since it tends to provide the least preferred combination of low strength and scarring.
  • laser energy can be applied to tissue in order to various combinations (including absolute and relative extents) of denatured, coagulated, and carbonized tissue.
  • the word "interface” as used herein will refer to the physical contact point or points between tissue portions (including natural tissues and/or intermediate layers as described herein), and in turn, to the zone of laser energy deposited at or near the interface in order to effect a bond between the two portions.
  • the present invention provides a method and related apparatus for laser tissue welding. The method and apparatus of the invention can be used to optimize welding modes and to provide advanced equipment design.
  • a preferred system of this invention comprises one or more components selected from the group consisting of a laser radiation source; a radiation transport component; one or more welding clamps; a cooling component with optics and sensor protection; a diagnostic component system; and an automatic welding control.
  • a system can include, for instance: (1) Source of Radiation:
  • the radiation source includes one or more lasers or set of lasers
  • the apparatus preferably further includes a radiation transport component, e.g., in the form of a set of fiberoptics cables, electrical and micro optical components adapted to transport radiation from laser to tissue;
  • a radiation transport component e.g., in the form of a set of fiberoptics cables, electrical and micro optical components adapted to transport radiation from laser to tissue;
  • the system can further include one or more welding clamps, e.g., with sensors, which function to hold welding tissue together and transmit information about the welding process;
  • the system of this invention also includes a cooling device adapted to cool optical components, sensors and tissue surfaces; absorb extra radiation from tissue; remove tissue particles, vapors or eliminate mists formed during welding process; and protect sensors from tissue particles.
  • the apparatus preferably also includes a set of sensors, cameras and electrical components adapted to diagnose various parameters within the tissue before, during and after laser welding process; (6) Automatic Welding Control:
  • the present system further includes a computer and monitor adapted to receive and compile information; provide substantially real time information for surgeon about tissue welding process, and permit control thereof.
  • a computer and monitor adapted to receive and compile information; provide substantially real time information for surgeon about tissue welding process, and permit control thereof.
  • the present invention addresses a variety of present concerns, including: (1) the ability to irradiate tissue with laser energy in order to obtain a surgical suture with specified features; (2) the development of related equipment and circuitry for laser welding in order to achieve such specified features in various types of tissue; and (3) the development of computer software for controlling the apparatus in order to achieve the desired features, and for use in modeling of the physical-chemical processes occurring in tissues influenced by powerful laser radiation.
  • Applicants have, in turn created a system that permits the user to: (1) create a laboratory testing ground for the development and substantiation of a method of laser tissue suturing; (2) review the optical properties of tissue, including particular features of laser radiation of various spectral ranges and it's interaction with various kinds of tissue and resultant tissue properties; (3) improve control methods for maintaining laser beam parameters while investigating the influence of radiation on tissue; (4) analyze and compare various experimental tissue laser suturing processes; (6) optimize parameters of laser radiation (e.g., including spectral range, duration, pulse ratio, power capacity of laser pulse); (7) investigate and determine the firmness of a laser welded suture and it's optical properties; (8) develop a three-dimensional axis- symmetrical non-stationary model of the processes of tissue interaction with laser radiation; (9) accomplish optional accounts for specified tissue types and definition of optimum radiation source parameters; and (10) compare the calculated results with experimental data and updating the model.
  • parameters of laser radiation e.g., including spectral range, duration, pulse ratio, power capacity of laser
  • Applicants Using thin intestine tissue as a model, Applicants have shown that it is possible to develop at least two basic approaches for tissue connection. One is based on dot influence of powerful radiation on tissue pieces being sutured. Power level and exposure time are selected to obtain a structure resembling a partially or entirely hollow cavity (Fig. la) surrounded by a zone or layer of coagulation.
  • a second, and more preferred, approach for forming welds of this invention involves the formation under the influence of radiation a carbonic joint-element between the tissue pieces (Fig. lb). If there is no gap between the sutured tissue pieces and a coagulated cylindrical layer is surrounding the carbonized framework the firmness of the suture may be even higher that of the former option. Moreover, the joint point can be formed not on the whole depth of sutured pieces but placed only near the border between them, thereby leading to a reduction of traumatic effect.
  • a prototype system of this invention is shown in the block diagram below. This diagram represents experimental prototype, which has been used in experiments.
  • Advanced prototype production prototype
  • production prototype can have a different layout, with a corresponding block diagram dependent on the configuration of the advanced prototype, e.g., with some of the various modules being combined.
  • the production prototype schematic can be represent as a following diagram:
  • the prototype assembly consists of a set of lasers with selective radiation in the wavelength range of about 0.5 microns to about 1.3 microns.
  • a set of lasers with re-tunable wavelength may be used instead.
  • a unit for transportation of laser radiation is represented by a set of fiber-optics cooled with water (particularly since the required power is expected to exceed 0.53 W/cm 2 ).
  • a main element of the prototype shown in the above diagram is an endoscopic device, which includes some or all of the following components:
  • a laser beam focusing unit 2) a tightening unit to hold tissue pieces in contact, and optionally to compress the tissue pieces in the course of laser welding,
  • a surface stmcture control for monitoring the surface stmcture of the welded tissue sample (e.g., a polarizing device to measure refraction and absorption indices of the welded tissue surface)
  • a firmness control for determining the firmness of welded suture
  • a visualization system including a CCD TV camera
  • the method and system of the present invention can be used to provide an optimal combination of tissue weld strength with reduced trauma. Without intending to be bound by theory, it would appear that this combination occurs, in part, by virtue of the ability to press the tissue portions together in order to force blood from the weld site and increase the density thereof. In turn, the transfer of radiation between pieces can be increase by about an order of magnitude, so that the amount of heat discharged on the upper layers will be significantly less than the amount discharged at the interface between the pieces. This approach also permits the user to focus a laser beam on this border (e.g., by means of a focal cross-over), thereby increasing the effective heat discharge.
  • the radial temperature gradients beyond the scope of the beam aperture are as great as possible, thereby ensuring that the thermal action of radiation is maintained locally and with lesser chance to influence the surrounding tissue.
  • This can be balanced with the desire to maintain a zone of denatured protein that is typically as large as possible, to establish necessary firmness of a suture.
  • the system of this invention permits an optimal balance to be established between the exposure time, focal point and beam size, in order to achieve an desired and optimal balance between the size of the thermal destmction zone and the firmness and stability of the individual weld elements, and in turn, the overall weld line.
  • a mathematical model of the temperature field in the course of laser irradiation of tissue, as described herein, can be performed using any suitable software language, e.g., FORTRAN.
  • the software can have the following stmcture:
  • a module for initial data input including initial conditions of the tissue itself, including thermophysical parameters of the tissue portions, as well as relevant aspects of the laser apparatus, including laser power capacity and or pulse power, mode of radiation, various relevant constant parameters, laser focusing parameters, and the like.
  • a control module in which initial conditions are stated, and information is received from the program application, which are together processed to solve a system of ordinary differential equations.
  • the modes of system integration can be corrected at this time, and improvements can be made to the laser tissue irradiation modes.
  • This module is the main software for the integration of a system of ordinary differential equations.
  • a standard program is provided for the integration of rigid systems of ordinary differential equations, incorporating an algorithm for the simulation of absorption and scattering.
  • a subroutine can be included for calculating nonstationary heat transfer equations under conditions of axial symmetry and in a specified impulse, involving the processes of heating the tissue water component and the formation of various zones or cavities in the tissue portions.
  • This subroutine can be called up by a program for integrating a system of ordinary differential equations over time.
  • One or more subroutines for calculating various thermophysical parameters of the tissue, and specific heat extraction, basedon time and the temperature of a tissue fragment can be used by the program to calculate various values for the nonstationary heat transfer equation described above.
  • Subroutine to address danger degrees of radiation can also provide the ability to visualize the temperature field on a real time scale, with calculations being relayed to form a colored image of the temperature field within the tissue on a monitor screen. This feature permits the operator to view the dynamics of the process directly, and as the calculations are made.
  • the calculations of specific heat extraction from the radiated tissue can be executed by a separate program or subroutine, with a technique for the simulation of absorption and scattering at various radiuses of an aperture in the radiated tissue fragment, and can be averaged to account for discrete elements.
  • the influence of laser radiation spectral-power features on the efficiency of welding has been analyzed in some published papers, but it appears that Applicants are the first to have considered and incorporated the influence of time- spatial distribution.
  • tissue radiation absorption index for a given wavelength is the tissue radiation absorption index for a given wavelength.
  • the radiation absorption index in tissue is described by the law of Bouguer, and absorption index values for above mentioned wavelengths have been published (12). Since the primary component of most tissues is water, the radiation absorption index for water is sometimes used to approximate spectral efficiency. In medical applications the average tissue thickness is approximately 1.5 mm
  • Laser tissue welding studies to date have typically used wavelengths in the range 0.63 ⁇ m to l. ⁇ m, presumably because 1) this range is highly supported with many types of medical lasers being produced commercially, including semiconductor, helium-neon and neodim (with the various additives) lasers, and 2) because tissue absorption tends to be smaller within this wavelength range, and wavelengths with this range tend to penetrate into the tissue more deeply.
  • Tissue portions to be welded typically provide a variety of different structural and morphological components. Inside the tissue layers discreet stmctures exist, including sensitive nerve endings, capillary blood vessels and a net of thin nerves, connecting these stmctures with each other and transmitting signals to and from the central nerve system. Changes within or in the relationship(s) between these various components can affect spectral characteristics, and in turn, tissue absorption characteristics, just as these components and characteristics can differ as between in vitro and in vivo applications.
  • a tissue welding laser of this invention is selected and used in a manner that maintains a desired laser radiation energy (power) at the welding zone.
  • a preferred average tissue welding power density is between about 10 W/cm and about 50 W/cm 2 .
  • Specified power density can be achieved in any suitable fashion, and preferably in a manner that provides an optimal combination of laser radiation power and beam cross-section area at the welding zone.
  • Laser beam power at levels higher than optimal can lead to technical and economical problems. For example, if the laser radiation power exceeds several watts it may be necessary to use a cooled fiber optical cable to deliver the radiation to the welding zone, thus increasing the complexity and cost of the apparatus, as well as requiring that the user meet whatever relevant safety precautions may exist.
  • the laser beam in a welding zone is formed by focusing optics.
  • the transverse dimensions of the beam are provided in the focal cross-over zone and depend on laser beam divergence at the entrance of the focusing optics, it's focal distance and aberrations. Beam divergence for commercially produced gas and semiconductor lasers, for instance, are typically in the range of about 3 mrad to about 4 mrad.
  • the transverse size of the laser waist should be about 0.015 cm to about 0.02 cm. If aberrations take place the size of laser waste may be much larger.
  • the use of short- focused aberration-free lenses, together with laser radiation having small divergence can reduce laser waste by up to about 0.0075cm to about 0.01 cm. It is thus possible to use lasers with lower power capacity while also expanding the range of variance by duration of exposure.
  • EXAMPLE 2 Multispectral laser welding Experimental equipment included laser radiation sources, focusing lenses, tissue fastening units as well as diagnostic devices, according to the functional schematic shown in Fig. 4.
  • Laser sources identified as LI -L3 were a conventional He-Ne gas laser, a semi-conductor laser, and a Nd laser, respectively.
  • the He-Ne laser (LI) with wavelength 0.63 ⁇ m was operated in a continuous mode.
  • the average radiation power was 25 mW.
  • Divergence of laser beam was 3 mrad.
  • An electromechanical modulator (EMM) was used to control the laser beam exposure time.
  • a variable duration pulse generator (PG) and a supplementary control unit (CU) were used to control the EMM.
  • the time of exposure could be varied in the range from 0.5 s up to several minutes.
  • the semi-conductor laser (L2, wavelength 0.68 ⁇ m) also worked in a continuous mode. Thus the average radiation power was 30 mW. Collimating optics provided semiconductor laser beam divergence on the order of that found with the He-Ne laser. An external pulse generator was used to modulate the laser beam pulse rate from units of Hz up to several tenfold of kHz and the duration of pulses - from a hundred nanoseconds (ns) up to hundred milliseconds (ms).
  • the Nd laser radiated a pulse mode at wavelengths of 0.53 ⁇ m and 1.06 ⁇ m.
  • the pulse rate was controlled by an external pulse generator which could generate pulses in a unitary mode, and in a periodic mode with frequencies from 1 up to 5 Hz.
  • the pulse duration was 20 ns.
  • the pulse radiation energy was equal to 8 mJ.
  • the beam divergence was 10 mrad.
  • the power and timing parameters of laser radiation were supervised by diagnostic devices.
  • the laser radiation was directed to diagnostic equipment by means of first and second beam splinters BSl and BS2.
  • the average power capacity and energy of radiation were measured by means of a conventional device (HMO-2) .
  • Measuring the pulse duration of a semiconductor laser was achieved by means of a photo-electronic amplifier PR1 (on the basis of a silicon photo diode ( ⁇ Ha-28) and oscilloscope OS1 of a type Cl-94.
  • Measuring of the Nd laser pulse duration was achieved by means of a photocoaxial amplifier PR2 of the type FEK-31 KP. It was connected to the oscilloscope (OS2) of the type Cl-11 through a wave resistance matching unit.
  • the laser beam focusing unit and tissue fastening unit were developed so that they could be used in the subsequent design of an equipment of laser tissue welding.
  • a lens with small aberrations was used in focusing unit.
  • the light aperture diameter was made 4 cm and the focal length 3.5 cm.
  • the focusing unit was furnished with special technological rigging, enabling to supervise the location of the laser waist central part and to measure distribution of laser radiation in cross section area.
  • the fastening of tissue was accomplished by means of a specially developed technological unit, the simplified schematics of which is shown in figures 5a (top view), 5b and 5c.
  • This unit permits to influence tissue with a laser beam that has specified levels of the power density on a specified plane (point) of tissue.
  • the unit includes two optical tables (1, 2) and a mandrel (3). Optical tables could be moved linearly at two orthogonal directions. Each table was supported with a scale (4, 5), enabling to determine linear displacement with step-type behavior 0.0025 cm.
  • the mandrel (3) (Fig. 5b, 5c) has three windows (6), which are used for fastening the tissue, the fine-tuning element and an optical slit to measure the cross-sectional energy distribution of the laser beam.
  • the specified elements were fixed in the mandrel by means of clamping springs (7).
  • the cell for tissue disposition consisted of two flat-parallel quartz plates with thickness 0.1 cm and 0.5 cm. The spectral characteristics of the plates are shown in Fig. 6. The tissue under research was placed between these plates, the distance between the plates being fixed by means of precious gaskets. The quartz plates were chosen so that to ensure identical transmission factors (the constancy of the contribution of optical elements) in a wide spectral range.
  • Cross-sectional laser beam energy distribution at the laser beam waist has been obtained by means of the optical table (1) (Fig. 5a) together with an optical slit.
  • the lightning size of the optical slit was equal 0.001 cm.
  • a fine tuning element (mirror) was used to accomplish accurate placing of a certain zone of the laser waist on a specified tissue site. Fine-tuning was achieved by means of the optical table (2).
  • a site visualization system was developed. This system consisted of a CCD TV camera (type SK 1004) with a frame-grabber and a PC.
  • the effect on the tissue surface by means of laser irradiation was investigated.
  • the pieces of natural tissue were used.
  • the tissue surface was placed within the laser beam laser waist.
  • the cross section area size of the laser beam on the tissue surface constituted 0.015 cm.
  • the following power flow densities were achieved: He-Ne laser - 110 W/cm 2 , semi-conductor laser - 130 W/cm 2 , Nd laser - 3 J/cm 2 .
  • the received power characteristics appreciably exceeded allowable values of power densities for laser tissue welding indicated in (4).
  • the duration of laser irradiation of the tissue surface has been varied in the range from several seconds up to two minute.
  • EXAMPLE 3 Experimental research of the tissue spectral characteristics. A study of the spectral characteristics of tissue samples was performed in a wavelengths range from 0.1 microns up to 10.6 microns. Two spectrophotometers (MPS-2000 from Shimadzu, 0.19-0.9 microns, IR-435 from Shimadzu, 2.5-10.6 microns) were used to measure reflection and transmission indexes of researched materials. All listed devices were developed on the two-beam basis the tuning and measurements being accomplished with microprocessors.
  • Figs. 7 and 8 the optical circuits of MPS-2000 and U-3400 are shown.
  • model MPS-2000 a Cemy-Tumer monochromator is used.
  • Model U-3400 a double monochromator is used as well as a photomultiplier (spectral range 0.19-0.9 microns) and a PbS photoconductor (spectral range 0.9-2.5 microns).
  • To conduct measurements of specular and diffuse reflection indices both monochromators were equipped with special supplementary units which schematics are shown in Figs. 9 and 10.
  • the multitarget unit RTA-2000 (Fig. 9) was used to proceed measurements of tissue diffuse reflection index in the wavelength range 0.19-0.9 microns the comparison method on an integrating sphere being applied. The latter was coated with BaSO .
  • FIG. 10 shows the optical circuit of spectral photometer IR-435 to be used in medium IR radiation range.
  • the spectral measurements were based on a method called the optical zero, which is established by an optical wedge, entered in the reference channel of the spectral photometer.
  • Such a circuit is more preferable for the medium IR range since the linearity and dynamic range of the photometry measurements are higher.
  • a distinctive feature of applied absorption index measuring technique is that in all measurements the same cell for tissue disposition was used.
  • the spectral characteristics of source and target windows of a cell are shown in Fig. 6.
  • the thickness of the cell was chosen to ensure identity for the tissue samples being used in experiments on laser welding.
  • the double thickness of a tissue sample is 0.3 cm. In the case when the influence of tissue thickness on its spectral characteristics was investigated the sample thickness was changed from 0.13 cm up to 0.15 cm.
  • the graph of the reflection index has distinctive oscillations in the short-wave spectral range 0.2-0.4 microns. This phenomenon appears to be due to some features of excitation in organic compositions.
  • the values of indices in this range do not exceed 0.2.
  • the fluctuations of the reflection index are essentially less than in the shortwavelength range.
  • the average value for the reflection index is 0.14.
  • the reflection index does appear to depend on wavelength and its value is 0.2.
  • a distinctive feature in behavior of a transmission index is its extremely low values for wavelengths less than 0.4 microns and appreciable increase in the range 0.4-0.9 microns. Maximum value of transmission index is achieved at wavelength 0.9 microns and is 0.38. It could be seen from Fig. 11, that the transmission index for investigated tissue samples strongly enough ( ⁇ 5 times) differs from the same index considered in (12). The absorption indices were calculated being based on the results of reflection and transmission indices measurements. The results are shown in Fig. 11. The analysis of the indicated graph shows, that the tissue has reasonably large absorption index (0.85) in the wavelength range 0.2-0.4 microns. On wavelengths from 0.4 microns up to 0.82 microns the value of absorption index decreases down to 0.38. Between 0.82 and 0.9 microns its value is almost constant.
  • the results of the tissue spectral characteristics research in the IR-range (2-25 microns) are shown in Fig. 13.
  • the transmission index was equal to 0 practically in the whole wavelength range and the reflection index was of an order of a few percents.
  • an oscillatory spectmm of a water was found in a region besides wavelength 3.3 microns.
  • the seemed increase of the reflection index at wavelengths above 4 microns is stipulated by sample heating with IR irradiation and the beginning of it's own radiation.
  • the power flow density was evaluated in an arbitrary tissue cross-section P(x), referred to power density on the tissue surface P 0 , for wavelengths 0.5 microns, 0.6 microns, 0.7 microns and 0.9 microns.
  • the results of calculations for an unfocused and focused laser beams are shown accordingly in Fig. 14 and Fig. 15.
  • the more preferable radiation wavelength is 0.9 microns.
  • the gradient of the power density along the laser beam grows. The largest gradient is observed at wavelength 0.5 microns.
  • the apparent advantage of near-IR radiation is connected with one rather essential problem.
  • Appointed spatial distribution could be formed in the long-focus mode. In this mode the size of a beam in the focal zone is essentially larger, than in the short-focus mode. Therefore for optimum maintenance of energy contribution it is necessary to increase the exposure duration or the laser power.
  • the former causes a decrease in welding speed and the latter increases the complexity of equipment maintenance.
  • the increase of exposure reduces speed of laser welding while an increase in laser radiation power complicates devices for laser tissue welding.
  • the short- focus mode Fig.
  • the more uniform power density distribution is provided on a wavelength equal to 0.5 microns.
  • wavelength increase the gradient of power density along the laser beam grows. It is obvious, that this case of radiation in visible range 0.5-0.6 microns is more preferably, than near-IR. It should be noted, that in the short-focus mode it is possible to ensure high power densities with a rather less powerful laser. Therefore this range is more preferable for laser tissue welding.
  • argon, xenon, krypton lasers and lasers on copper vapor should be mentioned.
  • the former type radiates in the wavelength range 0.49-0.51 microns and delivers a few watts of power.
  • the latter delivers several dozens watts of power in the range 0.51 up to 0.578 microns.
  • a single channel functional scheme of experimental equipment shown in Fig. 4 was applied.
  • the beam focusing unit and the tissue fastening were the same, as in researches on multispectral experimental equipment. Since the laser operated at a two wavelength pulse-periodic mode the equipment for diagnostics differed from the equipment, applied in multispectral research.
  • the power density on the tissue surface was equal to 625 W/cm 2 .
  • the image of a tissue sample being influenced with laser irradiation during 20 s is shown in Fig. 17.
  • the area where the -laser beam has been interacting with the tissue is brightly characterized by an expressed hole through the tissue and a peripheral zone around it. The inner walls of the hole are carbonized.
  • Tissue samples were investigated at following exposure duration: 2 samples - at 1.5 s, 7 samples - at 5 s, 1 sample - 10s, 5 samples - 20 s, 1 sample - 30 s.
  • Fig. 18 - 20 sample tissue images are shown being influenced by a laser beam at the exposure time intervals 1.5, 5 and 20 s. It could be seen that with an exposure duration increase the bum-through hole diameter is increased. At the exposure duration's 1.5 and 5 s on the contrary of the case of 20 s exposure no carbonization has been registered.
  • the tissue area in a vicinity of the burn-through hole had three characteristic zones: a purely bum-through zone and two ring zones.
  • the bu -through zone is represented by a circular open-through aperture, which size depends on the exposure time. For exposure times 1.5, 5 and 20 s the aperture diameter measured accordingly 1, 1.5 and 2.5 mm.
  • the periphery of the bum-through hole (internal wall) at exposure times 1.5 and 5 s had characteristic hardening caused apparently by tissue coagulation. At the exposure time 20 s carbonization was observed on the periphery of the burn-through zone.
  • the first and the second ring zone in all cases looked like a kind of concentric rings.
  • the sizes of these rings for all investigated exposure times were roughly identical.
  • the outer diameter of the first ring measured 3.0-3.5 mm, and outside - 4.3- 4.8 mm.
  • On appearance the tissue mo ⁇ hology within the second ring did not differ from the tissue, not subjected to the effect of laser radiation.
  • the first ring was characterized by a prominence and it's surface looked like being coated with a glass- like film.
  • the thickness of the glass-like film was by the order of 0.1 - 0.2 mm.
  • the prominence amplitude did not exceed 0.2 - 0.3 mm for the tissue sample being exposed at 5 s.
  • the amplitude of the first ring for a tissue sample being exposed at 20 s was 1.5 - 2 times larger.
  • the second ring was characterized by a weak cavity the amplitude of which at exposure time 5 s did not exceed 0.2 mm.
  • Fig. 21 shows a tissue sample being under the test of welded suture firmness. The suture exposed at 1.5 s has appeared to be weak, sutures exposed at 5 and 20 s were had sustained forces applied to them.
  • HDP and D20 from 0.7 Jim to 10 lim.- Infrared Phys., 1963, 3, pp.211-223.

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Abstract

La présente invention porte sur un procédé et un système (5a) qui permettent de souder des parties de tissu adjacentes au moyen de lasers, le procédé consistant à former une pluralité d'éléments non contigus formés par laser le long d'une ligne de soudure, les éléments étant positionnés suivant un motif prédéterminé les uns par rapport aux autres et ayant chacun une configuration prédéterminée en coupe transversale. Les éléments peuvent être créés indépendamment pour assurer un degré absolu et relatif de dénaturation, de coagulation et/ou de carbonisation au sein des tissus et particulièrement à l'intérieur des éléments individuels. En utilisation, l'énergie émise par une source laser peut être appliquée sur une surface accessible des tissus en contact, de manière à produire une combinaison optimale a) du nombre et de la disposition relative des éléments le long de la ligne de soudure; b) de la section transversale des éléments individuels le long de la ligne de soudure; et c) un impact sur les tissus à l'intérieur et autour de chaque élément (par exemple en termes de degré absolu et/ou relatif de dénaturation, de coagulation et/ou de carbonisation au sein de chaque élément). Le procédé et le système (5a) peuvent comprendre un dispositif de diagnostic qui permet à l'opérateur de disposer d'une évaluation en temps réel de divers paramètres pour réaliser ainsi une soudure optimale.
PCT/US2000/022726 1999-08-20 2000-08-18 Procede et systeme permettant de souder des tissus au moyen d'un faisceau laser WO2001013810A1 (fr)

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Cited By (12)

* Cited by examiner, † Cited by third party
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WO2003020113A2 (fr) * 2001-08-30 2003-03-13 Pacgen Cellco Llc Utilisation d'un rayonnement laser de faible puissance pour une vascularisation renforcee de greffons de tissus et de constructions tissulaires
EP2150182A2 (fr) * 2007-05-10 2010-02-10 Seraffix Ltd Système et procédé pour coller un tissu vivant
US7914527B2 (en) 2003-03-27 2011-03-29 Terumo Kabushiki Kaisha Energy based devices and methods for treatment of patent foramen ovale
US7922716B2 (en) 2003-03-27 2011-04-12 Terumo Kabushiki Kaisha Energy based devices and methods for treatment of anatomic tissue defects
US7972330B2 (en) 2003-03-27 2011-07-05 Terumo Kabushiki Kaisha Methods and apparatus for closing a layered tissue defect
US8021362B2 (en) 2003-03-27 2011-09-20 Terumo Kabushiki Kaisha Methods and apparatus for closing a layered tissue defect
US8038672B2 (en) 2003-03-27 2011-10-18 Terumo Kabushiki Kaisha Energy based devices and methods for treatment of patent foramen ovale
US8052678B2 (en) 2003-03-27 2011-11-08 Terumo Kabushiki Kaisha Energy based devices and methods for treatment of patent foramen ovale
US8109274B2 (en) 2005-04-11 2012-02-07 Terumo Kabushiki Kaisha Methods and electrode apparatus to achieve a closure of a layered tissue defect
US8133221B2 (en) 2004-06-21 2012-03-13 Terumo Kabushiki Kaisha Energy based devices and methods for treatment of anatomic tissue defects
US8308723B2 (en) 2009-10-09 2012-11-13 Coaptus Medical Corporation Tissue-penetrating guidewires with shaped tips, and associated systems and methods
US9302125B2 (en) 2003-06-10 2016-04-05 The Foundry, Llc Methods and apparatus for non-invasively treating atrial fibrillation using high intensity focused ultrasound

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US5766167A (en) * 1993-12-17 1998-06-16 United States Surgical Corporation Monopolar electrosurgical Instruments

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US5766167A (en) * 1993-12-17 1998-06-16 United States Surgical Corporation Monopolar electrosurgical Instruments

Cited By (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003020113A2 (fr) * 2001-08-30 2003-03-13 Pacgen Cellco Llc Utilisation d'un rayonnement laser de faible puissance pour une vascularisation renforcee de greffons de tissus et de constructions tissulaires
WO2003020113A3 (fr) * 2001-08-30 2003-08-07 Pacgen Cellco Llc Utilisation d'un rayonnement laser de faible puissance pour une vascularisation renforcee de greffons de tissus et de constructions tissulaires
US8038673B2 (en) 2003-03-27 2011-10-18 Terumo Kabushiki Kaisha Energy based devices and methods for treatment of patent foramen ovale
US8052678B2 (en) 2003-03-27 2011-11-08 Terumo Kabushiki Kaisha Energy based devices and methods for treatment of patent foramen ovale
US7922716B2 (en) 2003-03-27 2011-04-12 Terumo Kabushiki Kaisha Energy based devices and methods for treatment of anatomic tissue defects
US7972330B2 (en) 2003-03-27 2011-07-05 Terumo Kabushiki Kaisha Methods and apparatus for closing a layered tissue defect
US8021362B2 (en) 2003-03-27 2011-09-20 Terumo Kabushiki Kaisha Methods and apparatus for closing a layered tissue defect
US8038672B2 (en) 2003-03-27 2011-10-18 Terumo Kabushiki Kaisha Energy based devices and methods for treatment of patent foramen ovale
US8038671B2 (en) 2003-03-27 2011-10-18 Terumo Kabushiki Kaisha Energy based devices and methods for treatment of patent foramen ovale
US8038669B2 (en) 2003-03-27 2011-10-18 Terumo Kabushiki Kaisha Energy based devices and methods for treatment of patent foramen ovale
US8852181B2 (en) 2003-03-27 2014-10-07 Terumo Kabushiki Kaisha Energy based devices and methods for treatment of anatomic tissue defects
US7914527B2 (en) 2003-03-27 2011-03-29 Terumo Kabushiki Kaisha Energy based devices and methods for treatment of patent foramen ovale
US8066701B2 (en) 2003-03-27 2011-11-29 Terumo Kabushiki Kaisha Energy based devices and methods for treatment of patent foramen ovale
US8070747B2 (en) 2003-03-27 2011-12-06 Terumo Kabushiki Kaisha Energy based devices and methods for treatment of patent foramen ovale
US8075554B2 (en) 2003-03-27 2011-12-13 Terumo Kabushiki Kaisha Energy based devices and methods for treatment of patent foramen ovale
US9302125B2 (en) 2003-06-10 2016-04-05 The Foundry, Llc Methods and apparatus for non-invasively treating atrial fibrillation using high intensity focused ultrasound
US8133221B2 (en) 2004-06-21 2012-03-13 Terumo Kabushiki Kaisha Energy based devices and methods for treatment of anatomic tissue defects
US8109274B2 (en) 2005-04-11 2012-02-07 Terumo Kabushiki Kaisha Methods and electrode apparatus to achieve a closure of a layered tissue defect
EP2150182A4 (fr) * 2007-05-10 2012-01-18 Seraffix Ltd Système et procédé pour coller un tissu vivant
EP2150182A2 (fr) * 2007-05-10 2010-02-10 Seraffix Ltd Système et procédé pour coller un tissu vivant
US8308723B2 (en) 2009-10-09 2012-11-13 Coaptus Medical Corporation Tissue-penetrating guidewires with shaped tips, and associated systems and methods

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