Electromagnet energy distributions for electromagnetically induced mechanical cutting
Output optical energy pulses including relatively high energy magnitudes at the beginning of each pulse are disclosed. As a result of the relatively high energy magnitudes which lead each pulse, the leading edge of each pulse includes a relatively large slope. This slope is preferably greater than or equal to 5. Additionally, the full-width half-max value of the output optical energy distributions are between 0.025 and 250 microseconds and, more preferably, are about 70 microseconds. A flashlamp is used to drive the laser system, and a current is used to drive the flashlamp. A flashlamp current generating circuit includes a solid core inductor which has an inductance of 50 microhenries and a capacitor which has a capacitance of 50 microfarads.
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This application is a continuation of co-pending U.S. application Ser. No. 11/523,492, filed Sep. 18, 2006 (Att. Docket BI9066CON4), the contents of all which are expressly incorporated herein by reference. U.S. application Ser. No. 11/523,492 is a continuation of U.S. application Ser. No. 10/993,498 (U.S. Pat. No. 7,108,693; Att. Docket BI9066CON3), which is a continuation of U.S. application Ser. No. 10/164,451 (U.S. Pat. No. 6,821,272; Att Docket BI9066CON2), which is a continuation of U.S. application Ser. No. 09/883,607 (abandoned; Att Docket BI9066CON), which is a continuation of U.S. application Ser. No. 08/903,187 (U.S. Pat. No. 6,288,499; Att Docket BI9066P), which is a continuation-in-part of U.S. application Ser. No. 08/522,503 (U.S. Pat. No. 5,741,247; Att. Docket BI9001P), all of which are commonly assigned and the contents of which are expressly incorporated herein by reference. This application is related to U.S. application Ser. No. 10/624,967, filed Jul. 21, 2003 (Att. Docket BI9001DIV2CON).
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention relates generally to lasers and, more particularly, to output optical energy distributions of lasers.
2. Description of Related Art
A variety of laser systems are present in the prior art. A solid-state laser system generally comprises a laser rod for emitting coherent light and a stimulation source for stimulating the laser rod to emit the coherent light. Flashlamps are typically used as stimulation sources for Erbium laser systems, for example. The flashlamp is driven by a flashlamp current, which comprises a predetermined pulse shape and a predetermined frequency. The flashlamp current drives the flashlamp at the predetermined frequency, to thereby produce an output flashlamp light distribution having substantially the same frequency as the flashlamp current. This output flashlamp light distribution from the flashlamp drives the laser rod to produce coherent light at substantially the same predetermined frequency as the flashlamp current. The coherent light generated by the laser rod has an output optical energy distribution over time that generally corresponds to the pulse shape of the flashlamp current.
The pulse shape of the output optical energy distribution over time typically comprises a relatively gradually rising energy that ramps up to a maximum energy, and a subsequent decreasing energy over time. The pulse shape of a typical output optical energy distribution can provide a relatively efficient operation of the laser system, which corresponds to a relatively high ratio of average output optical energy to average power inputted into the laser system.
The prior art pulse shape and frequency may be suitable for thermal cutting procedures, for example, where the output optical energy is directed onto a target surface to induce cutting. New cutting procedures, however, do not altogether rely on laser-induced thermal cutting mechanisms. More particularly, a new cutting mechanism directs output optical energy from a laser system into a distribution of atomized fluid particles located in a volume of space just above the target surface. The output optical energy interacts with the atomized fluid particles causing the atomized fluid particles to expand and impart electromagnetically-induced mechanical cutting forces onto the target surface. As a result of the unique interactions of the output optical energy with the atomized fluid particles, typical prior art output optical energy distribution pulse shapes and frequencies have not been especially suited for providing optical electromagnetically-induced mechanical cutting. Specialized output optical energy distributions are required for optimal cutting when the output optical energy is directed into a distribution of atomized fluid particles for effectuating electromagnetically-induced mechanical cutting of the target surface.
SUMMARY OF THE INVENTIONThe output optical energy distributions of the present invention comprise relatively high energy magnitudes at the beginning of each pulse. As a result of these relatively high energy magnitudes at the beginning of each pulse, the leading edge of each pulse comprises a relatively large slope. This slope is preferably greater than or equal to 5. Additionally, the full-width half-max (FWHM) values of the output optical energy distributions are greater than 0.025 microseconds. More preferably, the full-width half-max values are between 0.025 and 250 microseconds and, more preferably, are between 10 and 150 microseconds. The full-width half-max value is about 70 microseconds in the illustrated embodiment. A flashlamp is used to drive the laser system, and a current is used to drive the flashlamp. A flashlamp current generating circuit comprises a solid core inductor having an inductance of about 50 microhenries and a capacitor having a capacitance of about 50 microfarads.
The present invention, together with additional features and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying illustrative drawings.
Referring more particularly to the drawings,
The flashlamp 41 is close-coupled to laser rod (not shown), which preferably comprises a cylindrical crystal. The flashlamp 41 and the laser rod are positioned parallel to one another with preferably less than 1 centimeter distance therebetween. The laser rod is suspended on two plates, and is not electrically connected to the flashlamp-driving current circuit 30. Although the flashlamp 41 comprises the preferred means of stimulating the laser rod, other means are also contemplated by the present invention. Diodes, for example, may be used instead of flashlamps for the excitation source. The use of diodes for generating light amplification by stimulated emission is discussed in the book Solid-State Laser Engineering, Fourth Extensively Revised and Updated Edition, by Walter Koechner, published in 1996, the contents of which are expressly incorporated herein by reference.
The incoherent light from the presently preferred flashlamp 41 impinges on the outer surface of the laser rod. As the incoherent light penetrates into the laser rod, impurities within the laser rod absorb the penetrating light and subsequently emit coherent light. The impurities may comprise erbium and chromium, and the laser rod itself may comprise a crystal such as YSGG, for example. The presently preferred laser system comprises either an Er, Cr:YSGG solid state laser, which generates electromagnetic energy having a wavelength in a range of 2.70 to 2.80 microns, or an erbium, yttrium, aluminum garnet (Er:YAG) solid state laser, which generates electromagnetic energy having a wavelength of 2.94 microns. As presently preferred, the Er, Cr:YSGG solid state laser has a wavelength of approximately 2.78 microns and the Er:YAG solid state laser has a wavelength of approximately 2.94 microns. According to one alternative embodiment, the laser rod may comprises a YAG crystal, and the impurities may comprise erbium impurities. A variety of other possibilities exist, a few of which are set forth in the above-mentioned book Solid-State Laser Engineering, Fourth Extensively Revised and Updated Edition, by Walter Koechner, published in 1996, the contents of which are expressly incorporated herein by reference. Other possible laser systems include an erbium, yttrium, scandium, gallium garnet (Er:YSGG) solid state laser, which generates electromagnetic energy having a wavelength in a range of 2.70 to 2.80 microns; an erbium, yttrium, aluminum garnet (Er:YAG) solid state laser, which generates electromagnetic energy having a wavelength of 2.94 microns; chromium, thulium, erbium, yttrium, aluminum garnet (CTE:YAG) solid state laser, which generates electromagnetic energy having a wavelength of 2.69 microns; erbium, yttrium orthoaluminate (Er:YAL03) solid state laser, which generates electromagnetic energy having a wavelength in a range of 2.71 to 2.86 microns; holmium, yttrium, aluminum garnet (Ho:YAG) solid state laser, which generates electromagnetic energy having a wavelength of 2.10 microns; quadrupled neodymium, yttrium, aluminum garnet (quadrupled Nd:YAG) solid state laser, which generates electromagnetic energy having a wavelength of 266 nanometers; argon fluoride (ArF) excimer laser, which generates electromagnetic energy having a wavelength of 193 nanometers; xenon chloride (XeCl) excimer laser, which generates electromagnetic energy having a wavelength of 308 nanometers; krypton fluoride (KrF) excimer laser, which generates electromagnetic energy having a wavelength of 248 nanometers; and carbon dioxide (C02), which generates electromagnetic energy having a wavelength in a range of 9 to 11 microns.
Particles, such as electrons, associated with the impurities absorb energy from the impinging incoherent radiation and rise to higher valence states. The particles that rise to metastable levels remain at this level for periods of time until, for example, energy particles of the radiation excite stimulated transitions. The stimulation of a particle in the metastable level by an energy particle results in both of the particles decaying to a ground state and an emission of twin coherent photons (particles of energy). The twin coherent photons can resonate through the laser rod between mirrors at opposing ends of the laser rod, and can stimulate other particles on the metastable level, to thereby generate subsequent twin coherent photon emissions. This process is referred to as light amplification by stimulated emission. With this process, a twin pair of coherent photons will contact two particles on the metastable level, to thereby yield four coherent photons. Subsequently, the four coherent photons will collide with other particles on the metastable level to thereby yield eight coherent photons.
The amplification effect will continue until a majority of particles, which were raised to the metastable level by the stimulating incoherent light from the flashlamp 41, have decayed back to the ground state. The decay of a majority of particles from the metastable state to the ground state results in the generation of a large number of photons, corresponding to an upwardly rising micropulse (64, for example,
The output optical energy distribution over time of the laser system is illustrated in
According to the present invention, the output optical energy distribution 60 comprises a large magnitude. This large magnitude corresponds to one or more sharply-rising micropulses at the leading edge of the pulse. As illustrated in
As mentioned above, the full-width half-max range is defined from a beginning time, where the amplitude first rises above one-half the peak amplitude, to an ending time, where the amplitude falls below one-half the peak amplitude a final time during the pulse width. The full-width half-max value is defined as the difference between the beginning time and the ending time.
The location of the full-width half-max range along the time axis, relative to the pulse width, is closer to the beginning of the pulse than the end of the pulse. The location of the full-width half-max range is preferably within the first half of the pulse and, more preferably, is within about the first third of the pulse along the time axis. Other locations of the full-width half-max range are also possible in accordance with the present invention. The beginning time preferably occurs within the first 10 to 15 microseconds and, more preferably, occurs within the first 12.5 microseconds from the leading edge of the pulse. The beginning time, however, may occur either earlier or later within the pulse. The beginning time is preferably achieved within the first tenth of the pulse width.
Another distinguishing feature of the output optical energy distribution 70 is that the micropulses 64, 66, 68, for example, comprise approximately one-third of the maximum amplitude 62. More preferably, the leading micropulses 64, 66, 68 comprise an amplitude of approximately one-half of the maximum amplitude 62. In contrast, the leading micropulses of the prior art, as shown in
The slope of the output optical energy distribution 60 is greater than or equal to 5 and, more preferably, is greater than about 10. In the illustrated embodiment, the slope is about 50. In contrast, the slope of the output optical energy distribution 20 of the prior art is about 4.
The output optical energy distribution 60 of the present invention is useful for maximizing a cutting effect of an electromagnetic energy source 32, such as a laser driven by the flashlamp driving circuit 30, directed into an atomized distribution of fluid particles 34 above a target surface 3, as shown in
The flashlamp current generating circuit 30 of the present invention generates a relatively narrow pulse, which is on the order of 0.25 to 300 microseconds, for example. Additionally, the full-width half-max value of the optical output energy distribution 60 of the present invention preferably occurs within the first 70 microseconds, for example, compared to full-width half-max values of the prior art occurring within the first 250 to 300 microseconds. The relatively quick frequency, and the relatively large initial distribution of optical energy in the leading portion of each pulse of the present invention, results in efficient mechanical cutting. If a number of pulses of the output optical energy distribution 60 were plotted, and the average power determined, this average power would be relatively low, compared to the amount of energy delivered to the laser system via the high-voltage power supply 33. In other words, the efficiency of the laser system of the present invention may be less than typical prior art systems.
According to one aspect of the present invention, the laser energy from the fiberoptic guide 61 focuses onto a combination of air and fluid, from the air tube 63 and the fluid tube 65, at an interaction zone 59. Fluid particles (e.g., atomized fluid particles) in the air and fluid mixture absorb energy from the laser energy of the fiberoptic tube 61, and explode. The explosive forces from these atomized fluid particles can in certain implementations impart disruptive (e.g., mechanical) cutting forces onto the target 57.
The electromagnetically induced disruptive cutter of the present invention uses the laser energy to expand fluid particles (e.g., atomized fluid particles) to thus impart disruptive cutting forces onto the target surface. The atomized fluid particles are heated, expanded, and cooled before contacting the target surface. The electromagnetically induced disruptive cutter of the present invention can use a relatively small amount of water and, further, can use only a small amount of laser energy to expand atomized fluid particles generated from the water. According to the electromagnetically induced disruptive cutter of the present invention, additional water may not be needed to cool the area of surgery, since the exploded atomized fluid particles are cooled by exothermic reactions before they contact the target surface. Thus, atomized fluid particles of the present invention are heated, expanded, and cooled before contacting the target surface. The electromagnetically induced disruptive cutter of the present invention is thus capable of cutting without charring or discoloration.
The emitted energy may have an output optical energy distribution that may be useful for achieving or maximizing a cutting effect of an electromagnetic energy source, such as a laser, directed toward a target surface. The cutting and/or ablating effects created by the energy may occur on or at the target surface, within the target surface, and/or above the target surface. For instance, using desired optical energy distributions, it is possible to disrupt a target surface by directing electromagnetic energy toward the target surface so that a portion of the energy is absorbed by fluid wherein fluid absorbing the energy may be on the target surface, within the target surface, above the target surface, or a combination thereof.
Referring to
Water from the water line 7 and pressurized air from the air line 9 are forced into a mixing chamber, which is disposed proximally of a mesh screen 31. The air and water mixture is very turbulent in the mixing chamber, and exits this chamber through the mesh screen 31, and through an aperture through which the fiber guide tube 23 extends, moving distally. The air and water mixture travels distally along the outside of the fiber guide tube 23, and then leaves the tube 23 and contacts the area of surgery. Air and water spray leaving the distal tip of the fiber guide tube 23 help to cool the target surface being cut and to remove materials cut by the laser.
The optical cutter further comprising a focusing optic 335 between the two metal cylindrical objects 19 and 21. The focusing optic 335 prevents undesired dissipation of laser energy from the fiber guide tube 5. Although shown coupling two fiber guide tubes having optical axes disposed in a straight line, the focusing optic 335 may be implemented/modified in other embodiments: to couple fiber guide tubes having non parallel optical axes (e.g., two fiber guide tubes having perpendicularly aligned optical axes); to facilitate rotation of one or both of the fiber guide tubes about its respective optical axis; and/or to consist of or comprise one or more of a mirror, pentaprism, or other light directing or transmitting medium. Specifically, energy from the fiber guide tube 5 dissipates slightly before being focused by the focusing optic 335. The focusing optic 335 focuses energy from the fiber guide tube 5 into the fiber guide tube 23.
Intense energy emitted from the fiberoptic guide 23 can be generated from a coherent source, such as a laser. In an illustrative embodiment, the laser comprises an erbium, chromium, yttrium, scandium, gallium garnet (Er, Cr:YSGG) solid state laser, which generates light having a wavelength in a range of 2.70 to 2.80 microns. As presently embodied, this laser has a wavelength of approximately 2.78 microns. Fluid emitted from the optical cutter (e.g., screen 31 and/or nozzle 71 of
The delivery system 355 of
In one embodiment, an output optical energy distribution includes a plurality of high-intensity leading micropulses, comprising high peak amounts of energy, that are directed toward a target surface. The energy is directed toward the target surface to obtain the desired cutting effects. For example, the energy may be directed into atomized fluid particles, as discussed above. The output optical energy distribution may also include one or more trailing micropulses after the maximum leading micropulse that may further help with removal of material. According to the present invention, a single large leading micropulse may be generated or, alternatively, two or more large leading micropulses may be generated. In accordance with one aspect of the present invention, relatively steeper slopes of the pulse and shorter duration of the pulses may lower an amount of residual heat produced in the material.
The output optical energy distribution may be generated by a flashlamp current generating circuit that is configured to generate a relatively narrow pulse, which is on the order of 0.25 to 300 microseconds, for example. Additionally, the full-width half-max value of the optical output energy distribution of the present invention can occur within the first 30 to 70 microseconds, for example, compared to full-width half-max values of the prior art occurring within the first 250 to 300 microseconds. The relatively quick frequency, and the relatively large initial distribution of optical energy in the leading portion of each pulse of the present invention, can result in relatively efficient disruptive cutting (e.g., mechanical cutting). The output optical energy distributions of the present invention can be adapted for cutting, shaping and removing tissues and materials, and further can be adapted for imparting electromagnetic energy into atomized fluid particles over a target surface, or other fluid particles located on or within the target surface. The cutting effect obtained by the output optical energy distributions of the present invention can be both clean and powerful and, additionally, can impart consistent cuts or other disruptive forces onto target surfaces.
Referring back to the figures, and in particular
According to one implementation of the present invention, materials can be removed from a target surface at least in part by disruptive cutting forces, instead of by conventional (e.g., thermal) cutting forces. In such implementations, energy is used only to induce disruptive forces onto the targeted material. Thus, the atomized fluid particles act as the medium for transforming the electromagnetic energy of the laser into the disruptive (e.g., mechanical) energy required to achieve the disruptive cutting effect of the present invention. The disruptive (e.g., mechanical) interaction of the present invention can be safer, faster, and can in certain implementations attenuate or eliminate negative thermal side-effects typically associated with conventional laser cutting systems.
The fiberoptic guide 23 (e.g.,
Additionally, applicants have found that this orientation of the nozzle 71, pointed toward the target surface, can enhance the cutting efficiency of the present invention. Each atomized fluid particle contains a small amount of initial kinetic energy in the direction of the target surface. When electromagnetic energy from the fiberoptic guide 23 contacts an atomized fluid particle, the spherical exterior surface of the fluid particle acts as a focusing lens to focus the energy into the water particle's interior.
As shown in
These disruptive forces cause the target surface 407 to break apart from the material surface through a “chipping away” action. The target surface 407 does not undergo vaporization, disintegration, or charring. The chipping away process can be repeated by the present invention until the desired amount of material has been removed from the target surface 407. Unlike prior art systems, certain implementations of the present invention may not require a thin layer of fluid. In fact, while not wishing to be limited, a thin layer of fluid covering the target surface may in certain implementations interfere with the above-described interaction process. In other implementations, a thin layer of fluid covering the target surface may not interfere with the above-described interaction process.
These various parameters can be adjusted according to the type of cut and the type of tissue. Hard tissues include tooth enamel, tooth dentin, tooth cementum, bone, and cartilage. Soft tissues, which the electromagnetically induced disruptive cutter of the present invention is also adapted to cut, include skin, mucosa, gingiva, muscle, heart, liver, kidney, brain, eye, and vessels. Other materials may include glass and semiconductor chip surfaces, for example. A user may also adjust the combination of atomized fluid particles exiting the nozzle 71 to efficiently implement cooling and cleaning of the fiberoptic 23 (
Looking again at
The diameters of the atomized fluid particles can be less than, almost equal to, or greater than the wavelength of the incident electromagnetic energy. In each of these three cases, a different interaction occurs between the electromagnetic energy and the atomized fluid particle.
The resulting portions from the explosion of the water particle 401, and the pressure-wave, produce the “chipping away” effect of cutting and removing of materials from the target surface 407. Thus, according to the “explosive grenade” effect shown in
A third case shown in
The combination of
An illustrated embodiment of light delivery for medical applications of the present invention is through a fiberoptic conductor, because of its light weight, lower cost, and ability to be packaged inside of a handpiece of familiar size and weight to the surgeon, dentist, or clinician. Non-fiberoptic systems may be used in both industrial applications and medical applications, as well. The nozzle 71 is employed to create an engineered combination of small particles of the chosen fluid. The nozzle 71 may comprise several different designs including liquid only, air blast, air assist, swirl, solid cone, etc. When fluid exits the nozzle 71 at a given pressure and rate, it is transformed into particles of user-controllable sizes, velocities, and spatial distributions.
Although an exemplary embodiment of the invention has been shown and described, many other changes, modifications and substitutions, in addition to those set forth in the above paragraphs, may be made by one having ordinary skill in the art without necessarily departing from the spirit and scope of this invention.
Claims
1. A flashlamp current generating circuit, comprising:
- a solid core inductor having an inductance of about 50 microhenries;
- a capacitor coupled to the inductor, the capacitor having a capacitance of 50 microfarads; and
- a flashlamp coupled to the solid core inductor.
2. A pulse for driving a flashlamp that is used as a stimulation source for a laser rod, comprising:
- a leading edge having a slope which is greater than or equal to about 5, the slope being defined on a plot of the pulse as y over x (y/x) where y is current in amps and x is time in microseconds; and
- a full-width half-max value in a range from 0.025 to 250 microseconds.
3. The pulse for driving a flashlamp as recited in claim 2, wherein the full-width half-max value is in a range from 10 to 150 microseconds.
4. The pulse for driving a flashlamp as recited in claim 3, wherein the full-width half-max value is about 70 microseconds.
5. The pulse for driving a flashlamp as recited in claim 2, wherein the slope is greater than or equal to about 10.
6. The pulse for driving a flashlamp as recited in claim 2, wherein the slope is greater than or equal to about 100.
7. The pulse for driving a flashlamp as recited in claim 6, wherein the slope is about 240.
8. A method, comprising:
- focusing or placing a peak concentration of energy into an interaction zone above a target;
- outputting atomized fluid particles from a plurality of atomizers into the interaction zone; and
- at least a portion of the atomized fluid particles in the interaction zone highly absorbing at least a portion of the energy and expanding, wherein disruptive forces are imparted onto the target.
9. The method as recited in claim 8, wherein an output axis of a first one of the plurality of atomizers is not parallel to an output axis of a second one of the plurality of atomizers and both of the output axes point toward the interaction zone.
10. The method as recited in claim 8, wherein the energy is generated using the flashlamp current generating circuit of claim 1.
11. The method as recited in claim 8, wherein the energy is generated using the pulse of claim 2
12. A flashlamp current generating circuit, comprising:
- an inductor having an inductance less than about 16 microhenries;
- a capacitor coupled to the inductor, the capacitor having a capacitance of 50 microfarads; and
- a flashlamp coupled to the inductor.
13. The flashlamp current generating circuit as recited in claim 12, wherein the inductor comprises an inductance within a range of about 10 to 15 microhenries.
14. The flashlamp current generating circuit as recited in claim 12, wherein the inductor comprises a solid core inductor.
15. The flashlamp current generating circuit as recited in claim 14, wherein the a solid core inductor has a rated inductance of about 50 microhenries.
Type: Application
Filed: Jun 26, 2007
Publication Date: Jun 26, 2008
Applicant:
Inventors: Ioana M. Rizoiu (Dana Point, CA), Andrew I. Kimmel (San Clemente, CA)
Application Number: 11/823,149
International Classification: H01S 3/0915 (20060101);