Abstract:
An ultrasonic surgical dissection system and method that employs an ultrasonic waveform that provides improved dissection of tissue while simultaneously providing improved hemostasis is disclosed. The disclosed system provides an ultrasonic waveform that includes a carrier frequency that may be pulse modulated at a predetermined rate and/or duty cycle. Embodiments are presented wherein the disclosed system provides an ultrasonic waveform having a frequency modulated carrier frequency. Additionally or alternatively, the disclosed waveform may be amplitude modulated. In yet another embodiment, an amplitude modulation of the ultrasonic signal may be synchronized, at least in part, with a frequency modulation of the ultrasonic signal. The frequency modulation and/or amplitude modulation may include continuously variable modulations and/or substantially instantaneous transitions between a first frequency and a second frequency and/or a first amplitude and a second amplitude.

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates to systems and methods for providing energy to biological tissue and, more particularly, to an ultrasonic dissection system having frequency shifting and multifrequency operating modes, and methods of use therefor. 
     2. Background of Related Art 
     Energy-based tissue treatment is well known in the art. Various types of energy (e.g., electrical, ultrasonic, microwave, cryogenic, thermal, laser, etc.) are applied to tissue to achieve a desired result. Ultrasonic energy may be delivered to tissue using a surgical probe that includes a transducer coupled with an end effector, and configured to deliver ultrasonic energy to tissue. 
     The use of ultrasonic energy in surgical procedures is known to those skilled in the art to be a valuable resource for cutting and fragmenting tissue of a patient. Most of these apparatus incorporate a sinusoidal driving signal which causes the mechanical tip to vibrate at a selected frequency, usually in the range of 20 KHz to 60 KHz. 
     The benefits associated with the use of ultrasonic energy powered devices, and in particular, ultrasonic instruments for surgical use, are known. For example, the use of an ultrasonic generator in conjunction with a surgical scalpel facilitates faster and easier cutting of organic tissue while accelerating coagulation. Improved cutting may result from increased body tissue-to-scalpel contact caused by the high frequency of vibration of the scalpel blade in relation to body tissue. Improved coagulation may result from heat generated by contact between the high frequency vibrations of a scalpel blade and body tissue. 
     Ultrasonic instruments may include a variety of end effectors (e.g., cutting blades, shears, hook, ball, forceps, etc.) adapted for specific medical procedures. The ultrasonic end effector is disposed at a distal end of the ultrasonic instrument. These ultrasonic instruments are primarily used in a variety of medical procedures including open surgical procedures, luminal procedures and endoscopic procedures. 
     It is known that at the lower end of the preferred frequency spectrum, e.g., 20 KHz to 40 KHz, larger tip displacements are possible. It is also known that larger tip displacements provide a better tissue cutting effect than small tip displacements. Ultrasonic energy at the high end of the preferred frequency spectrum, e.g., 40 KHz to 60 KHz, can have a more hemostatic effect. This is due in part to the increased absorption of higher frequency energy by tissue. However, larger tip displacements are not feasible at these higher frequencies. Therefore, devices which operate in this realm may have reduced tissue cutting performance. 
     SUMMARY 
     Disclosed is an ultrasonic surgical dissection system and method that employs an ultrasonic waveform that may provide improved dissection (cutting) of tissue and, effectively and concurrently provide improved hemostasis (coagulation). In one embodiment, the disclosed system provides an ultrasonic waveform that includes a carrier frequency which may be pulse-modulated at a predetermined rate and/or duty cycle. In another embodiment, the disclosed system provides an ultrasonic waveform having a frequency-modulated carrier frequency. Additionally or alternatively, the disclosed waveform may be amplitude-modulated. In yet another embodiment, an amplitude modulation of the ultrasonic signal may be synchronized, at least in part, with a frequency modulation of the ultrasonic signal. The frequency modulation and/or amplitude modulation may include continuously variable modulations and/or substantially instantaneous transitions between a first frequency and a second frequency and/or a first amplitude and a second amplitude. The disclosed ultrasonic signal causes corresponding oscillation of at least one ultrasonic transducer included in an ultrasonic surgical instrument, which, in turn, is operably coupled to an end effector, e.g., a scalpel, to cut and/or coagulate tissue. In this manner, waveforms associated with improved dissection and waveforms associated with improved coagulation may be advantageously combined, in an essentially simultaneous manner, to enable a surgeon to effectuate dissection and hemostasis in a single operative step. Additionally, reduced power use may be realized, which may have advantages such as, without limitation, cooler operating temperatures, increased battery life, and reduced maintenance requirements. 
     In an embodiment, the disclosed ultrasonic surgical system may include a variable frequency oscillator that is configured to generate an oscillator output signal. The oscillator output signal frequency may be determined in accordance with an oscillator control signal provided by a controller. The disclosed ultrasonic surgical system may include a variable gain amplifier having a signal input and a control input. The amplifier signal input is operably coupled to the oscillator output. The amplifier is configured to amplify the oscillator output signal by an amount determined according to an amplifier control signal provided by the controller, to generate an ultrasonic driving signal. The controller is operably coupled to the oscillator and the amplifier, and is configured to provide an oscillator control signal and an amplifier control signal in response to a user input. A user interface operably coupled to the controller is adapted to convey a user input to the controller. An actuator is also operably coupled to the controller and is adapted to convey an actuation signal (to, e.g., activate and deactivate the system to control the delivery of ultrasonic energy to tissue). The disclosed system additionally may include an ultrasonic instrument operably coupled to the amplifier, including at least one transducer adapted to convert the ultrasonic driving signal into ultrasonic energy for application to tissue. The transducer may be configured to selectively generate at least one of longitudinal vibrations, lateral vibrations, or torsional vibrations. 
     In an embodiment, the disclosed ultrasonic surgical system may include one or more sensors configured to sense an operating parameter of the system, including without limitation a parameter relating to the variable frequency oscillator and/or the variable gain amplifier, and to provide a sensor signal corresponding to the sensed parameter to the controller. The sensor may include a zero-crossing detector. 
     Also disclosed is a method for generating an ultrasonic surgical waveform, comprising the steps of generating an electromagnetic oscillator signal having a first carrier frequency, and modulating the amplitude of the electromagnetic oscillator signal to generate an electromagnetic driving signal including a plurality of carrier frequency bursts. The resulting electromagnetic driving signal is transduced into an ultrasonic surgical waveform. The disclosed method may further include generating an electromagnetic oscillator signal having a second carrier frequency, wherein successive carrier frequency bursts alternate between the first carrier frequency and the second carrier frequency. Additionally or alternatively, successive carrier frequency bursts may alternate between a first amplitude and a second amplitude. 
     Further, disclosed is an ultrasonic surgical generator, including a variable frequency oscillator configured to generate an oscillator output signal having a frequency determined according to an oscillator control signal. The ultrasonic surgical generator may include a variable gain amplifier operably coupled to the oscillator, that is configured to amplify the oscillator output signal by an amount determined according to an amplifier control signal, which, in turn generates a driving signal. A controller is operably coupled to the oscillator and the amplifier, and is configured to provide an oscillator control signal and an amplifier control signal in response to a user input. The disclosed ultrasonic surgical generator may additionally include a user interface operably coupled to the controller and adapted to convey a user input to the controller. The generator additionally includes an actuator input, operably coupled to the controller, and adapted to receive an actuation signal from an actuator to convey the actuation signal to the controller. An ultrasonic instrument output is also provided, to deliver the ultrasonic driving signal to an ultrasonic instrument. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features, and advantages of the present disclosure will become more apparent in light of the following detailed description when taken in conjunction with the accompanying drawings in which: 
         FIG. 1  shows a schematic diagram of an embodiment of an ultrasonic dissection and coagulation system in accordance with the present disclosure; 
         FIG. 2  shows a functional block diagram of an embodiment of an ultrasonic dissection and coagulation system in accordance with the present disclosure; 
         FIG. 3  depicts an ultrasonic waveform generated by an embodiment of an ultrasonic dissection and coagulation system in accordance with the present disclosure; 
         FIG. 4  depicts another ultrasonic waveform generated by an embodiment of an ultrasonic dissection and coagulation system in accordance with the present disclosure; 
         FIG. 5  depicts yet another ultrasonic waveform generated by an embodiment of an ultrasonic dissection and coagulation system in accordance with the present disclosure; and 
         FIG. 6  depicts still another ultrasonic waveform generated by an embodiment of an ultrasonic dissection and coagulation system in accordance with the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Particular embodiments of the present disclosure are described hereinbelow with reference to the accompanying drawings, however, it is to be understood that the disclosed embodiments are merely exemplary of the disclosure, which may be embodied in various forms. Well-known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present disclosure in virtually any appropriately detailed structure. 
     In the drawings and in the descriptions that follow, the term “proximal,” as is traditional, shall refer to the end of the instrument that is closer to the user, while the term “distal” shall refer to the end that is farther from the user. 
       FIG. 1  illustrates an ultrasonic dissection and coagulation system  10  that includes an ultrasonic instrument  12 , an ultrasonic generator module  14 , and a remote actuator  16 . Ultrasonic generator module  14  is operatively connected to ultrasonic instrument  12  by an electrically conductive cable  18  and functions to control the power and frequency of current supplied to ultrasonic instrument  12 . Actuator  16 , e.g., a foot switch, is operatively connected to ultrasonic generator module  14  by cable  20 . Actuator  16  may be actuated to activate generator module  14 , which, in turn, causes an ultrasonic driving signal to be delivered to a transducer  30  of ultrasonic instrument  12 . Generator module  14  includes a user interface module  17 . 
     Transducer  30  is operably coupled with ultrasonic end effector  21  of instrument  12  by way of a vibration coupler (contained within barrel portion  26  and body portion  24 , not explicitly shown). Transducer  30  converts an ultrasonic driving signal received from generator module  14  into ultrasonic energy (e.g., acoustic or mechanical wave energy), which, in turn, is delivered to end effector  21  to cut and/or coagulate tissue. Transducer  30  may be any suitable transducer capable of converting an ultrasonic driving signal, such as an alternating current electronic signal, into an acoustic or mechanical vibration. By way of example, transducer  30  may include any of a variety of electromechanical conversion elements, e.g., electrodynamic, voice coil, piezoelectric, and/or magnetostrictive elements. 
     Transducer  30  may include one or more electromechanical conversion elements having distinct ultrasonic characteristics. As an example only, and with respect to a longitudinal axis “A-A” of instrument  12 , a first electromechanical conversion element may be adapted to provide a longitudinal wave, a second electromechanical conversion element may be adapted to provide a lateral wave, a third electromechanical conversion element may be adapted to provide a torsional wave, and so forth. One or more electromechanical conversion elements may be selectively activated to enable the generation of longitudinal, lateral, and/or torsional ultrasonic energy, as desired. The disclosed ultrasonic instrument  12  may include one or more transducers  30 . 
     Ultrasonic instrument  12  includes housing  22  and elongated body portion  24  extending distally therefrom. Housing  22  may be formed from molded housing half-sections  22   a  and  22   b  and includes a barrel portion  26  having a longitudinal axis aligned with the longitudinal axis of body portion  24 , and a stationary handle portion  28  extending obliquely from barrel portion  26 . Ultrasonic transducer  30  is supported within and extends from the proximal end of housing  22  and is coupled to ultrasonic generator module  14  via cable  18 . Transducer  30  may be a separate component, or incorporated into and/or within ultrasonic instrument  12 . Ultrasonic generator module  14  supplies an alternating current electrical signal having an ultrasonic frequency to the transducer  30  to cause oscillation thereof. 
     The ultrasonic end effector  21  is disposed adjacent the distal end of elongated body portion  24  and is actuated by moving movable handle  36  with respect to stationary handle portion  28 . Movable handle  36  and stationary handle portion  28  may include openings  38  and  40 , respectively, defined therein that facilitate gripping and actuation of ultrasonic instrument  12 . Elongated body portion  24  is supported within rotatable knob  34  and may be selectively rotated by rotating knob  34  with respect to housing  22  to change the orientation of the distal end of ultrasonic instrument  12 . 
     It is to be understood that ultrasonic end effector  21  is an illustrative embodiment of an ultrasonic implement and that other types and/or forms of ultrasonic implements are envisioned, such as a blade, a hook, or a ball, and/or an aspirator assembly. Similarly, it will be appreciated that ultrasonic instrument  12  is an illustrative embodiment of an ultrasonic device and that other instrument forms, e.g., pencil, forceps, scalpel, vessel sealer, and so forth are contemplated within the scope of the present disclosure. 
     It is to be understood that the ultrasonic dissection and coagulation system  10  and the ultrasonic generator module  14  are provided and explained in detail for example only, and should not be construed as limiting the embodiments of the present disclosure. Indeed, the embodiments disclosed herein may be employed in non-surgical applications including ultrasonic welding, ultrasonic mass flow meters, ultrasonic atomizers or any other suitable electro-mechanical ultrasonic system. 
       FIG. 2  is a control block diagram of the disclosed ultrasonic dissection and coagulation system  10  having an ultrasonic generator module  14  that includes (in an operably connected configuration) an oscillator  50 , an amplifier  52 , a controller  54 , and an ultrasonic instrument  12 . Oscillator  50  is configured to provide a variable frequency output signal in a range of about 20 KHz to about 60 KHz and includes a signal output  51 , and an oscillator control input  53  that is adapted to receive at least one oscillator control signal from controller  54 . Oscillator  50  may utilize any suitable manner of ultrasonic signal generation, such as without limitation, a voltage-controlled oscillator (VCO), digitally-controlled oscillator (DCO), digital waveform synthesis, wavetable lookup (e.g., a waveform lookup table with digital to analog conversion), and the like. 
     Amplifier  52  includes a signal input  55 , a driving signal output  59 , and an amplifier control input  57 . Output  51  of oscillator  50  is operatively coupled to input  55  of amplifier  52 . Amplifier  52  is configured to respond to an amplifier control signal received at control input  57  from an amplifier control signal output  63  of controller  54  to adjust an amplifier operating parameter, including without limitation, gain, attenuation, phase, output voltage, output current, output power, and the like. Driving signal output  59  is operatively coupled with ultrasonic instrument  12  to provide an ultrasonic driving signal thereto. Amplifier  52  may utilize any amplification suitable for the dynamic processing of ultrasonic waveforms, including without limitation a voltage-controlled amplifier (VCA), a digitally-controlled amplifier (DCA), class D pulse width modulation, resistor ladder network, and the like. 
     Ultrasonic dissection and coagulation system  10  includes a controller  54  that is in operable communication with oscillator  50 , amplifier  52 , actuator  16 , and user interface module  17 . The communication may be continuous or intermittent. The communicated control data may be communicated in analog form, digital form, using a pulse width modulated signal, using a frequency or analog modulated signal, or any other communication technology. Controller  54  is programmed to at least process data to control the generation of the ultrasonic energy, as described herein. Controller  54  may be embodied in any of hardware, software, software in execution, firmware, microcode, bytecode, in virtualization, in a hardware description language, logic gates, circuitry, digital circuitry, RAM, ROM, MEMS, and the like. 
     User interface module  17  is configured to receive user input, and provide at least one user interface signal to controller  54 . Controller  54  interprets the user input and controls the operation of ultrasonic dissection and coagulation system  10  in accordance therewith. More particularly, controller  54  is configured to control oscillator  50  and amplifier  52  to generate at least one ultrasonic dissection and/or coagulation waveform as described herein. In particular, oscillator  50  generates waveforms in a range of about 20 KHz to about 60 KHz, which may be processed by amplifier  53  to generate one or more ultrasonic dissection and/or coagulation waveforms having various duty cycles, frequencies, peak voltages, peak currents, peak power, and other suitable characteristics. 
     Controller  54  is further configured to receive at actuator input  65  at least one input from an actuator  16  to selectively control the generation of a desired ultrasonic drive signal. In embodiments, ultrasonic dissection and coagulation system  10  may include two or more actuators  16  that may be coupled to corresponding actuator inputs  65  of controller  54  to enable a user, e.g., a surgeon, to selectively activate ultrasonic dissection and coagulation system  10  in one or more predetermined operating modes. 
     Controller  54  may include a microprocessor (not explicitly shown) operably connected to a memory (not explicitly shown) which may be volatile type memory (e.g., RAM) and/or non-volatile type memory (e.g., flash media, disk media, etc.). Controller  54  may include any suitable logic processor (e.g., control circuit), hardware, software, firmware, or any other logic control adapted to perform the features discussed herein. 
     The user interface module  17  may include one or more input controls, such as without limitation, buttons, continuous controls, rotary and/or linear potentiometers, encoders, switches, touch screens, and the like, for controlling at least one operating parameter of ultrasonic dissection and coagulation system  10 . Additionally or alternatively, user interface module  17  may include one or more visual indicators and/or display screens (not explicitly shown) for providing the user with variety of output information (e.g., intensity settings, treatment complete indicators, etc.). 
     The user interface module  17  allows a user (e.g., a surgeon, nurse, or technician) to adjust the ultrasonic energy parameters (e.g., operating mode, output power, waveform, duty cycle, drive voltage, drive current, frequency, and/or other parameters) to achieve the desired ultrasonic energy characteristics suitable to achieve a surgical objective (e.g., dissection, coagulating, tissue sealing, etc.). Additionally or alternatively, user interface module  17  may include a user-selectable desired tissue effect (e.g., hemostasis, coagulation, ablation, dissection, cutting, and/or sealing tissue). Ultrasonic dissection and coagulation system  10  may also include one or more input controls (not explicitly shown) that may be redundant with user interface module  17 . 
     During use, a user, typically a surgeon, may utilize user interface  17  to input one or more operating parameters to controller  54 . Actuation of actuator  16  by a use causes controller  54  to communicate one or more control signals to oscillator  50  and/or amplifier  52  which, in turn, causes oscillator  50  and/or amplifier  52  to generate at least one waveform which corresponds to the desired operating parameters. For example, and without limitation, a desired operating parameter may include single frequency mode enable, dual frequency mode enable, a first burst time, a second burst time, a first burst frequency, a second burst frequency, a first burst amplitude, a second burst amplitude, a duty cycle, an on time, an off time, a burst orientation (e.g., longitudinal wave, lateral wave, torsional wave), a burst pattern, and the like. In one embodiment, the disclosed system  10  may include the capability to utilize user interface  17  to store one or more predetermined parameters in a volatile and/or non-volatile memory included within controller  54 , which may be selectively recalled for use. 
     In one embodiment, the disclosed system  10  may be configured to generate a waveform  100  as shown in  FIG. 3 . As can be seen, a carrier frequency is amplitude-modulated to form a succession of carrier frequency bursts  102  having an on-time  110 , with a null period  104  having an off-time  112  therebetween. The on-time  110  of a carrier frequency burst  102  may be any desired value, e.g., within a range of about fifteen (15) microseconds to about one (1) second, however, it is contemplated that the on-time  110  of a carrier frequency burst  102  may be about twenty (20) milliseconds. The off-time  112  of null period  104  may be any desired value, e.g., within a range of about fifteen (15) microseconds to about one (1) second, however, it is contemplated that the off-time  112  may be about ten (10) milliseconds. Accordingly, a burst repetition interval  114  may be within a range of about thirty (30) microseconds to about two (2) seconds, and may be about thirty (30) milliseconds. 
     In an embodiment, disclosed system  10  may include at least one sensor  70 ,  72  that is configured to sense a property of oscillator output  51 , amplifier input  55 , amplifier output  59 , and/or waveform  100 , and is operably coupled to controller  54  to provide a waveform property signal thereto. By way of example, the sensor  70 ,  72  may include a zero-crossing detector adapted to sense a zero crossing of a waveform, and to provide a zero-crossing signal to a sensor input  71 ,  73  of controller  54 . During use, controller  54  may process the zero crossing signal to ensure that a burst  102  begins and/or ends on a zero crossing. In this manner, high frequency transients caused by sharp rising or falling edges, e.g., ringing or glitching, may be minimized or eliminated, which may increase operating efficiency and/or improve cooling of the system  10  and components thereof. 
     The system  10  may be configured to generate a waveform  200  as shown in  FIG. 4 , wherein a carrier frequency is frequency-modulated to form a succession of first carrier frequency bursts  202  and second carrier frequency bursts  204 . The first burst time  210  and second burst time  212  may be any desired length of time, e.g., within a range of about fifteen (15) microseconds to about one (1) second, however, it is contemplated that a first burst time  210  and a second burst time  212  may be about twenty (20) milliseconds each, respectively. As shown, a first burst  202  has a higher frequency, e.g., a frequency in a range of about 40 KHz to about 60 KHz, while a second burst  204  has a lower frequency, e.g., a frequency in a range of about 20 KHz to about 40 KHz. In this manner, improved coagulation may be achieved during a first burst  202  while improved cutting may be achieved during a second burst  204 . The described frequency modulation may thus provide overall improved cutting and coagulating in an essentially simultaneous manner, which may in turn reduce operative times and improve patient outcomes. 
     In another variation illustrated in  FIG. 5 , the system  10  may be configured to generate a waveform  300  wherein a carrier frequency is frequency modulated to form a succession of first carrier frequency bursts  302  and second carrier frequency bursts  304 , wherein a first null period  306  having a first off-time  312  follows a first carrier frequency burst  302 , and a second null period  307  having a second off-time  316  follows a second carrier frequency burst  304 . The first burst time  310  and second burst time  312  may be any desired length of time, e.g., within a range of about 15 microseconds to about one second, however, it is contemplated that a first burst time  310  and a second burst time  312  may be about twenty (20) milliseconds each, respectively. As shown, a first burst  302  has a higher frequency, e.g., a frequency in a range of about 40 KHz to about 60 KHz, while a second burst  304  has a lower frequency, e.g., a frequency in a range of about 20 KHz to about 40 KHz. In this manner, improved coagulation may be achieved during a first burst  302  while improved cutting may be achieved during a second burst  304 . Additionally, the first null period  306  and/or the second null period  307  may provide improved cooling of the system  10  and the components thereof, and/or may provide improved temperature control at the operative site which may, in turn, improve patient outcomes. 
     Controller  54  may utilize a sensor signal provided by the at least one sensor  70 ,  72  to ensure that a transition from a first frequency to a second frequency, and/or vice versa, occurs at a zero crossing of waveform  300 . 
     In yet another variation illustrated in  FIG. 6 , the system  10  may be configured to generate a waveform  400  wherein a carrier frequency is frequency-modulated to form a succession of first carrier frequency bursts  402  and second carrier frequency bursts  404 . The carrier frequency is additionally amplitude-modulated such that the first carrier frequency burst  402  has a first amplitude  420 , and the second carrier frequency burst  404  has a second amplitude  422 . As shown, first amplitude  420  may be greater than second amplitude  422 , however, it is contemplated that first amplitude  420  may be less than second amplitude  422 . The first burst time  410  and second burst time  412  may be any desired length of time as discussed hereinabove, however it is contemplated that a first burst time  410  and a second burst time  412  may be about twenty (20) milliseconds each, respectively. As shown, a first burst  402  has a lower frequency, e.g., a frequency in a range of about 20 KHz to about 40 KHz, while a second burst  404  has a higher frequency, e.g., a frequency in a range of about 40 KHz to about 60 KHz. In this manner, greater larger tip displacements may be achieved during a first burst  402  having a greater amplitude  420 , which may provide improved and faster cutting, while, in an essentially simultaneous manner, providing improved control of coagulation during a second burst  404 . Additionally or alternatively, an off-time (not explicitly shown) may be provided between first burst  402  and second burst  404 , which may provide improved cooling of the system  10  and the components thereof, and/or may provide improved temperature control at the operative site which may, in turn, improve patient outcomes. 
     The described embodiments of the present disclosure are intended to be illustrative rather than restrictive, and are not intended to represent every embodiment of the present disclosure. Further variations of the above-disclosed embodiments and other features and functions, or alternatives thereof, may be made or desirably combined into many other different systems or applications without departing from the spirit or scope of the disclosure as set forth in the following claims both literally and in equivalents recognized in law.