US20080151953A1

US20080151953A1 - Electromagnet energy distributions for electromagnetically induced mechanical cutting

Info

Publication number: US20080151953A1
Application number: US11/823,149
Authority: US
Inventors: Ioana M. Rizoiu; Andrew I. Kimmel
Original assignee: Biolase Technology Inc
Current assignee: Biolase Technology Inc
Priority date: 1995-08-31
Filing date: 2007-06-26
Publication date: 2008-06-26
Also published as: DE69832714D1; ES2311924T3; EP1560470B1; EP1560470A1; WO1998057526A3; US6821272B2; AU8071798A; US7696466B2; EP1016328A4; US20060043903A1; EP1560470B8; US6288499B1; US7108693B2; DE69832714T2; DE69839829D1; US20020014855A1; EP1016328B1; WO1998057526A2; US20070014322A1; US20020149324A1

Abstract

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.

Description

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 INVENTION

1. 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 INVENTION

The 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.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plot of flashlamp-driving current versus time according to the prior art;

FIG. 2 is a plot of output optical energy versus time for a laser system according to the prior art;

FIG. 3 is a schematic circuit diagram illustrating a circuit for generating a flashlamp-driving current in accordance with the present invention;

FIG. 4 is a plot of flashlamp-driving current versus time in accordance with the present invention;

FIG. 5 is a plot of output optical energy versus time for a laser system in accordance with the present invention;

FIG. 6 is a block diagram showing a fluid output used in combination with an electromagnetic energy source having a flashlamp driving circuit in accordance with the present invention;

FIG. 7 illustrates one embodiment of an electromagnetic cutter of the present invention;

FIGS. 8 and 9 illustrate a particular embodiment of an electromagnetically induced cutter that can be used with the invention;

FIG. 10 is a schematic block diagram illustrating an electromagnetically induced disruptive cutter according to an embodiment of the present invention;

FIG. 11 is an optical cutter with a focusing optic in accordance with an embodiment of the present invention;

FIG. 12 illustrates a control panel for programming a combination of atomized fluid particles according to an illustrated embodiment;

FIG. 13 is a plot of particle size versus fluid pressure in accordance with one implementation of the present invention;

FIG. 14 is a plot of particle velocity versus fluid pressure in accordance with one implementation of the present invention;

FIG. 15 is a schematic diagram illustrating a fluid particle, a source of electromagnetic energy, and a target surface according to an embodiment of the present invention;

FIG. 16 is a schematic diagram illustrating a “grenade” effect according to an embodiment of the present invention;

FIG. 17 is a schematic diagram illustrating an “explosive ejection” effect according to an embodiment of the present invention;

FIG. 18 is a schematic diagram illustrating an “explosive propulsion” effect according to an embodiment of the present invention;

FIG. 19 is a schematic diagram illustrating a combination of FIGS. 16-18;

FIG. 20 is a schematic diagram illustrating a “cleanness” of cut obtained by one implementation of the present invention; and

FIG. 21 is a schematic diagram illustrating a roughness of cut obtained by a prior art system.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

Referring more particularly to the drawings, FIG. 1 illustrates a plot of flashlamp-driving current versus time according to the prior art. The flashlamp-driving current 10 initially ramps up to a maximum value 12. The initial ramp 14 typically comprises a slope (current divided by time) of between 1 and 4. After reaching the maximum value 12, the flashlamp-driving current 10 declines with time, as illustrated by the declining current portion 16. The prior art flashlamp-driving current 10 may typically comprise a frequency or repetition rate of 1 to 15 hertz (Hz). Additionally, the flashlamp-driving current 10 of the prior art may typically comprise a pulse width greater than 300 microseconds. The full-width half-max value of the flashlamp-driving current 10 is typically between 250 and 300 microseconds. The full-width half-max value is defined as a value of time corresponding to a length of the full-width half-max range plotted on the time axis. The full-width half-max range is defined on the time axis from a beginning time, where the amplitude first reaches one half of the peak amplitude of the entire pulse, to an ending time, where the amplitude reaches one half of the peak amplitude a final time within the pulse. The full-width half-max value is the difference between the beginning time and the ending time.
FIG. 2 illustrates a plot of energy versus time for the output optical energy of a typical prior art laser. The output optical energy distribution 20 generally comprises a maximum value 22, an initial ramp 24, and a declining output energy portion 26. The micropulses 28 correspond to population inversions within the laser rod as coherent light is generated by stimulated emission. The average power of the laser can be defined as the power delivered over a predetermined period of time, which typically comprises a number of pulses. The efficiency of the laser system can be defined as a ratio of the output optical power of the laser, to the input power into the system that is required to drive the flashlamp. Typical prior art laser systems are designed with flashlamp-driving currents 10 and output optical energy distributions 20 which optimize the efficiency of the system.
FIG. 3 illustrates a flashlamp-driving circuit 30 according to the presently preferred embodiment. The flashlamp-driving circuit 30 comprises a high-voltage power supply 33, a capacitor 35, a rectifier 37, an inductor 39, and a flashlamp 41. The capacitor 35 is connected between the high-voltage power supply 33 and ground, and the flashlamp 41 is connected between the inductor 39 and ground. The high-voltage power supply 33 preferably comprises a 1500 volt source, having a charging rate of 1500 Joules per second. The flashlamp 41 may comprise a 450 to 700 torr source and, preferably, comprises a 450 torr source. The capacitor 35 preferably comprises a 50 microfarad capacitor, and the rectifier 37 preferably comprises a silicon-controlled rectifier. The inductor 39 preferably comprises a 50 microhenry solid-core inductor. In alternative embodiments, the inductor 39 may comprise a 13 microhenry inductance. In still other alternative embodiments, the inductor 39 may comprise inductance values of between 10 and 15 micro-henries. Other values for the inductor 39 and the capacitance 35 may be implemented in order to obtain flashlamp-driving currents having relatively large leading amplitudes, for example, as discussed below.
FIG. 4 illustrates the flashlamp driving current 50 of the present invention, which passes from the inductor 39 to the flashlamp 41. The flashlamp driving current of the present invention preferably has a pulse width which is greater than about 0.25 microseconds and, more preferably, which is in a range of 100 to 300 mircoseconds. In the illustrated embodiment, the pulse width is about 200 microseconds. The flashlamp driving current 50 comprises a maximum value 52, an initial ramp portion 54, and a declining current portion 56. The flashlamp 41 preferably comprises a cylindrical glass tube having an anode, a cathode, and a gas therebetween such as Xenon or Krypton. An ionizer circuit (not shown) ionizes the gas within the flashlamp 41. As the flashlamp-driving current 50 is applied to the anode of the flashlamp 41, the potential between the anode and the cathode increases. This potential increases as the flashlamp-driving current increases, as indicated by the initial ramp 54. Current flows through the gas of the flashlamp 41, resulting in the flashlamp 41 emitting bright incoherent light.
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, FIG. 5). As the particles on the ground level are again stimulated back up to the metastable state, the number of photons being emitted decreases, decreases, corresponding to a downward slope in the micropulse 64, for example. The micropulse continues to decline, corresponding to a decrease in the emission of coherent photons by the laser system. The number of particles stimulated to the metastable level increases to an amount where the stimulated emissions occur at a level sufficient to increase the number of coherent photons generated. As the generation of coherent photons increases, and particles on the metastable level decay, the number of coherent photons increases, corresponding to an upwardly rising micropulse.
The output optical energy distribution over time of the laser system is illustrated in FIG. 5 at 60. The output optical energy distribution of the present invention preferably has a pulse width that is greater than about 0.25 microseconds and, more preferably, in a range of 125 to 300 mircoseconds. In the illustrated embodiment, the pulse width is about 200 microseconds. The output optical energy distribution 60 comprises a maximum value 62, a number of leading micropulses 64, 66, 68, and a portion of generally declining optical energy 70.
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 FIG. 5, the micropulse 68 comprises a maximum value 62 which is at or near the very beginning of the pulse. Additionally, the full-width half-max value of the output optical energy distribution in FIG. 5 is approximately 70 microseconds, compared to full-width half-max values of the prior art typically ranging from 250 to 300 microseconds. Applicant's invention contemplates pulses comprising full-width half-max values greater than 0.025 microseconds and, preferably, ranging from 10 to 150 microseconds, but other ranges may also be possible. Additionally, Applicant's invention contemplates a pulse width of between 0.25 and 300 microseconds, for example, compared to typical prior-art pulse widths which are greater than 300 microseconds. Further, a frequency of 20 Hz is presently preferred. Alternatively, a frequency of 30 Hz may be used. Applicants' invention generally contemplates frequencies between 1 and 100 Hz, compared to prior art frequencies typically ranging from 1 to 15 Hz.
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 FIG. 2, are relatively small in amplitude.
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 FIG. 6. An apparatus for directing electromagnetic energy into an atomized distribution of fluid particles above a target surface is disclosed in U.S. Pat. No. 5,741,247, entitled ATOMIZED FLUID PARTICLES FOR ELECTROMAGNETICALLY INDUCED CUTTING, the entire contents of which are incorporated herein by reference. The high- intensity leading micropulses 64, 66, and 68 impart large amounts of energy into atomized fluid particles which preferably comprise water, to thereby expand the fluid particles and apply mechanical cutting forces to the target surface of, for example, tooth enamel, tooth dentin, tooth cementum, bone, and cartilage, skin, mucosa, gingiva, muscle, heart, liver, kidney, brain, eye or vessels. The trailing micropulses after the maximum micropulse 68 have been found to further enhance the cutting efficiency. According to the present invention, a single large leading micropulse 68 may be generated or, alternatively, two or more large leading micropulses 68 (or 64, 66, for example) may be generated.
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.
FIG. 7 shows an embodiment of an electromagnetically induced disruptive cutter, according to an aspect of the present invention, in which a fiberoptic guide 61, an air tube 63, and a fluid tube, such as a water tube 65, are placed within a hand-held housing 67. The fluid tube 65 can be operated under a relatively low pressure, and the air tube 63 can be operated under a relatively high pressure.
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.
FIGS. 8 and 9 illustrate another embodiment of the electromagnetically induced mechanical cutter. The atomizer for generating atomized fluid particles comprises a nozzle 71, which may be interchanged with other nozzles (not shown) for obtaining various spatial distributions of the atomized fluid particles, according to the type of cut desired. A second nozzle 72, shown in phantom lines, may also be used. In a simple embodiment, a user controls the air and water pressure entering into the nozzle 71. The nozzle 71 is thus capable of generating many different user-specified combinations of atomized fluid particles and aerosolized sprays. 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. The cone angle may be controlled, for example, by changing the physical structure of the nozzle 71. For example, various nozzles 71 may be interchangeably placed on the electromagnetically induced disruptive cutter. Alternatively, the physical structure of a single nozzle 71 may be changed.
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.
FIG. 10 is a block diagram illustrating a electromagnetically induced disruptive cutter system of the present invention. As shown in FIG. 10, an electromagnetic energy source 351 is coupled to both a controller 353 and a delivery system 355. The delivery system 355 imparts cutting forces onto the target surface 357. In one implementation, the delivery system 355 comprises a fiberoptic guide 23 (FIG. 8) for routing energy from the electromagnetic energy source 351 through an optional interaction zone 359 and toward the target surface 357.
Referring to FIG. 11, an optical cutter according to one aspect of the present invention is shown, wherein a fiber guide tube 5, a water line 7, and an air line 9 may be fed into the optical cutter. A cap 15 fits onto the optical cutter and is secured via threads. The fiber guide tube 5 abuts within a cylindrical metal piece 19. Another cylindrical metal piece 21 is a part of the cap 15. When the cap 15 is threaded onto the optical cutter, the two cylindrical metal pieces/ tubes 19 and 21 are moved into close proximity of one another. The laser energy exits from the fiber guide tube 23 and is applied to a target surface within the patient's mouth, according to a predetermined surgical plan.
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 FIG. 8) comprises water in an illustrated embodiment, other fluids may be used and appropriate wavelengths of the electromagnetic energy source may be selected to allow for high absorption by the fluid. 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:YALO3) 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 (CO2), which generates electromagnetic energy having a wavelength in a range of 9.0 to 10.6 microns.
The delivery system 355 of FIG. 10 is depicted comprising a fluid output. In exemplary embodiments implementing a fluid output, water can be chosen as a preferred fluid because of its biocompatibility, abundance, and low cost. The actual fluid used may vary as long as it is properly matched (meaning it is highly absorbed) to the selected electromagnetic energy source (i.e. laser) wavelength. The delivery system 355 can comprise an atomizer for delivering user-specified combinations of atomized fluid particles into the interaction zone 359. The controller 353 controls various operating parameters of the laser 351, and further controls specific characteristics of the user-specified combination of atomized fluid particles output from the delivery system 355, thereby mediating cutting effects on and/or within the target 357.
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 FIG. 12, a control panel 377 for allowing user-programmability of the atomized fluid particles is illustrated. By changing the pressure and flow rates of the fluid, for example, the user can control the atomized fluid particle characteristics. These characteristics determine absorption efficiency of the laser energy, and the subsequent cutting effectiveness of the electromagnetically induced disruptive cutter. This control panel may comprise, for example, a fluid particle size control 378, a fluid particle velocity control 379, a cone angle control 380, an average power control 381, a repetition rate 382, and a fiber selector 383.
FIG. 13 illustrates a plot 385 of mean fluid particle size versus pressure. According to this figure, when the pressure through the nozzle 71 is increased, the mean fluid particle size of the atomized fluid particles decreases. The plot 387 of FIG. 14 shows that the mean fluid particle velocity of these atomized fluid particles increases with increasing pressure.
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., FIG. 8) can be placed into close proximity of the target surface. This fiberoptic guide 23, however, does not actually contact the target surface. Since the atomized fluid particles from the nozzle 71 are placed into the interaction zone 59, the purpose of the fiberoptic guide 23 is for placing laser energy into this interaction zone, as well. One feature of the present invention is the cleaning effect of the air and water, from the nozzle 71, on the fiberoptic guide 23. The present inventors have found that this cleaning effect is optimal when the nozzle 71 is pointed somewhat directly at the target surface. For example, debris from the disruptive cutting can be removed by the spray from the nozzle 71.
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 FIG. 15, the water particle 401 has an illuminated side 403, a shaded side 405, and a particle velocity 407. The focused electromagnetic energy is absorbed by the water particle 401, causing the interior of the water particle to heat and explode rapidly. This exothermic explosion cools the remaining portions of the exploded water particle 401. The surrounding atomized fluid particles further enhance cooling of the portions of the exploded water particle 401. A pressure-wave is generated from this explosion. This pressure-wave, and the portions of the exploded water particle 401 of increased kinetic energy, are directed toward the target surface 407. The incident portions from the original exploded water particle 401, which are now traveling at high velocities with high kinetic energies, and the pressure-wave, impart strong, concentrated, disruptive (e.g., mechanical) forces onto the target surface 407.
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.
FIGS. 16, 17 and 18 illustrate various types of absorptions of the electromagnetic energy by atomized fluid particles. The nozzle 71 can be configured to produce atomized sprays with a range of fluid particle sizes narrowly distributed about a mean value. The user input device for controlling cutting efficiency may comprise a simple pressure and flow rate gauge or may comprise a control panel as shown in FIG. 12, for example. Upon a user input for a high resolution cut, relatively small fluid particles are generated by the nozzle 71. Relatively large fluid particles are generated for a user input specifying a low resolution cut. A user input specifying a deep penetration cut causes the nozzle 71 to generate a relatively low density distribution of fluid particles, and a user input specifying a shallow penetration cut causes the nozzle 71 to generate a relatively high density distribution of fluid particles. If the user input device comprises the simple pressure and flow rate gauge, then a relatively low density distribution of relatively small fluid particles can be generated in response to a user input specifying a high cutting efficiency. Similarly, a relatively high density distribution of relatively large fluid particles can be generated in response to a user input specifying a low cutting efficiency. Other variations are also possible.
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 (FIG. 8), as well. According to an illustrated embodiment, the combination of atomized fluid particles may comprise a distribution, velocity, and mean diameter to effectively cool the fiberoptic guide 23, while simultaneously keeping the fiberoptic guide 23 clean of particular debris which may be introduced thereon by the surgical site.
Looking again at FIG. 15, electromagnetic energy contacts each atomized fluid particle 401 on its illuminated side 403 and penetrates the atomized fluid particle to a certain depth. The focused electromagnetic energy is absorbed by the fluid, inducing explosive vaporization of the atomized fluid particle 401.
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. FIG. 16 illustrates a case where the atomized fluid particle diameter is less than the wavelength of the electromagnetic energy (d<lambda.). This case causes the complete volume of fluid inside of the fluid particle 401 to absorb the laser energy, inducing explosive vaporization. The fluid particle 401 explodes, ejecting its contents radially. Applicants refer to this phenomena as the “explosive grenade” effect. As a result of this interaction, radial pressure-waves from the explosion are created and projected in the direction of propagation. The direction of propagation is toward the target surface 407, and in one embodiment, both the laser energy and the atomized fluid particles are traveling substantially in the direction of propagation.
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 FIG. 16, the small diameter of the fluid particle 401 allows the laser energy to penetrate and to be absorbed violently within the entire volume of the liquid. Explosion of the fluid particle 401 can be analogized to an exploding grenade, which radially ejects energy and shrapnel. The water content of the fluid particle 401 is evaporated due to the strong absorption within a small volume of liquid, and the pressure-waves created during this process produce the material cutting process.
FIG. 17 shows a case where the fluid particle 401 has a diameter, which is approximately equal to the wavelength of the electromagnetic energy (d approximately equal to lambda). According to this “explosive ejection” effect, the laser energy travels through the fluid particle 401 before becoming absorbed by the fluid therein. Once absorbed, the fluid particle's shaded side heats up, and explosive vaporization occurs. In this case, internal particle fluid is violently ejected through the fluid particle's shaded side, and moves rapidly with the explosive pressure-wave toward the target surface. As shown in FIG. 17, the laser energy is able to penetrate the fluid particle 401 and to be absorbed within a depth close to the size of the particle's diameter. The center of explosive vaporization in the case shown in FIG. 17 is closer to the shaded side 405 of the moving fluid particle 401. According to this “explosive ejection” effect shown in FIG. 17, the vaporized fluid is violently ejected through the particle's shaded side toward the target surface 407.
A third case shown in FIG. 18 is the “explosive propulsion” effect. In this case, the diameter of the fluid particle is larger than the wavelength of the electromagnetic energy (d>lambda). In this case, the laser energy penetrates the fluid particle 401 only a small distance through the illuminated surface 403 and causes this illuminated surface 403 to vaporize. The vaporization of the illuminated surface 403 tends to propel the remaining portion of the fluid particle 401 toward the targeted material surface 407. Thus, a portion of the mass of the initial fluid particle 401 is converted into kinetic energy, to thereby propel the remaining portion of the fluid particle 401 toward the target surface with a high kinetic energy. This high kinetic energy is additive to the initial kinetic energy of the fluid particle 401. The effects shown in FIG. 18 can be visualized as a micro-hydro rocket with a jet tail, which helps propel the particle with high velocity toward the target surface 407. The exploding vapor on the illuminated side 403 thus supplements the particle's initial forward velocity.
The combination of FIGS. 16-18 is shown in FIG. 19. The nozzle 71 produces the combination of atomized fluid particles which are transported into the interaction zone 59. Laser is focused on this interaction zone 59. Relatively small fluid particles 431 explode via the “grenade” effect, and relatively large fluid particles 433 explode via the “explosive propulsion” effect. Medium sized fluid particles, having diameters approximately equal to the wavelength of the laser and shown by the reference number 435, explode via the “explosive ejection” effect. The resulting pressure-waves 437 and exploded fluid particles 439 impinge upon the target surface 407. FIG. 20 illustrates the clean, high resolution cut produced by the electromagnetically induced disruptive cutter of the present invention. Unlike the cut of the prior art shown in FIG. 21, the cut of the present invention can be clean and precise. Among other advantages, this cut can provide an ideal bonding surface, can be accurate, and may not stress remaining materials surrounding the cut.
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 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.