Patent Publication Number: US-8535341-B2

Title: Methods for ultrasonic tissue sensing and feedback

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a Continuation Application claiming the benefit of and priority to U.S. application Ser. No. 12/582,857, filed on Oct. 21, 2009, which is incorporated herein in its entirety by reference. 
    
    
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to an ultrasonic cutting device and method for sensing, measuring, and adjusting tissue properties. More particularly, the present disclosure relates to an ultrasonic cautery cutting device including a feedback mechanism for automatically adjusting, in real-time, ultrasonic waves applied to tissue. 
     2. Background of the Related Art 
     Ultrasonic instruments are effectively used in the treatment of many medical conditions, such as removal of tissue and cauterization of vessels. Cutting instruments that utilize ultrasonic waves generate vibrations with an ultrasonic transducer along a longitudinal axis of a cutting blade. By placing a resonant wave along the length of the blade, high-speed longitudinal mechanical movement is produced at the end of the blade. These instruments are advantageous because the mechanical vibrations transmitted to the end of the blade are very effective at cutting organic tissue and, simultaneously, coagulate the tissue using the heat energy produced by the ultrasonic frequencies. Such instruments are particularly well suited for use in minimally invasive procedures, such as endoscopic or laparoscopic procedures, where the blade is passed through a trocar to reach the surgical site. 
     For each kind of cutting blade (e.g., length, material, size), there are one or more (periodic) driving signals that produce a resonance along the length of the blade. Resonance results in optimal movement of the blade tip and, therefore, optimal performance during surgical procedures. However, producing an effective cutting-blade driving signal is not a trivial task. For instance, the frequency, current, and voltage applied to the cutting tool must all be controlled dynamically, as these parameters change with the varying load placed on the blade and with temperature differentials that result from use of the tool. 
       FIG. 1  shows a block schematic diagram of a prior-art circuit used for applying ultrasonic mechanical movements to an end effector. The circuit includes a power source  102 , a control circuit  104 , a drive circuit  106 , a matching circuit  108 , a transducer  110 , and also includes a handpiece  112 , and a waveguide  114  secured to the handpiece  112  (diagrammatically illustrated by a dashed line) and supported by a cannula  120 . The waveguide  114  terminates to a blade  116  at a distal end. A clamping mechanism referred to as an “end effector”  118 , exposes and enables the blade portion  116  of the waveguide  114  to make contact with tissue and other substances. 
     The drive circuit  106  produces a high-voltage self-oscillating signal. The high-voltage output of the drive circuit  106  is fed to the matching circuit  108 , which contains signal-smoothing components that, in turn, produce a driving signal (wave) that is fed to the transducer  110 . The oscillating input to the transducer  110  causes the mechanical portion of the transducer  110  to move back and forth at a magnitude and frequency that sets up a resonance along the waveguide  114 . For optimal resonance and longevity of the resonating instrument and its components, the driving signal applied to the transducer  110  should be as smooth a sine wave as may practically be achieved. For this reason, the matching circuit  108 , the transducer  110 , and the waveguide  114  are selected to work in conjunction with one another and are all frequency sensitive with and to each other. 
     Because a relatively high-voltage (e.g., 100 V or more) is required to drive a typical piezoelectric transducer  110 , the power source that is available and is used in prior-art ultrasonic cutting devices is an electric mains (e.g., a wall outlet) of, typically, up to 15 A, 120 VAC. Therefore, most ultrasonic cutting devices resemble that shown in  FIGS. 1 and 2  and utilize a countertop box  202  with an electrical cord  204  to be plugged into the electric mains  206  for supply of power. Resonance is maintained by a phase locked loop (PLL), which creates a closed loop between the output of the matching circuit  108  and the drive circuit  106 . For this reason, in prior art devices, the countertop box  202  includes all of the drive and control electronics  104 ,  106  and the matching circuit(s)  108 . A supply cord  208  delivers a sinusoidal waveform from the box  202  to the transducer  110  within the handpiece  112  and, thereby, to the waveguide  114 . 
     A disadvantage exists in the prior art due to the frequency sensitivity of the matching circuit  108 , the transducer  110 , and the waveguide  114 . By having a phase-locked-loop feedback circuit between the output of the matching circuit  108  and the drive circuit  104 , the matching circuit  108  is required to be located in the box  202 , near the drive circuit  108 , and separated from the transducer  110  by the length of the supply cord  208 . This architecture introduces transmission losses and electrical parasitics, which are common products of ultrasonic-frequency transmissions. 
     In addition, prior-art devices attempt to maintain resonance at varying waveguide  114  load conditions by monitoring and maintaining a constant current applied to the transducer. However, the only predictable relationship between current applied to the transducer  110  and amplitude is at resonance. Therefore, with constant current, the amplitude of the wave along the waveguide  114  is not constant across all frequencies. When prior art devices are under load, therefore, operation of the waveguide  114  is not guaranteed to be at resonance and, because only the current is being monitored and held constant, the amount of movement on the waveguide  114  may vary greatly. For this reason, maintaining constant current is not an effective way of maintaining a constant movement of the waveguide  114 . 
     Furthermore, in the prior art, handpieces  112  and transducers  110  are replaced after a finite number of uses, but the box  202 , which is vastly more expensive than the handpiece  112 , is not replaced. As such, introduction of new, replacement handpieces  112  and transducers  110  frequently causes a mismatch between the frequency-sensitive components ( 108 ,  110 , and  112 ), thereby disadvantageously altering the frequency introduced to the waveguide  114  and the energy applied to tissue. One way to avoid such mismatches is for the prior-art circuits to restrict themselves to precise frequencies. This precision brings with it a significant increase in cost. 
     SUMMARY 
     Notwithstanding all these frequency control arrangements, there is a continuing need for improvement in the control of energy delivery to tissue and the determination when tissue treatment has reached an optimal level. 
     The present disclosure is intended to overcome the drawbacks of other methods by measuring and adjusting the output with load variations. Specifically, an ultrasonic surgical instrument for applying energy to tissue is presented including an ultrasonic transmission member having a proximal end and a distal end. An ultrasonically-actuated cutting element is provided having a tissue contacting surface and is located at the distal end of the transmission member. A clamp member is supported adjacent to the cutting element for clamping the tissue, the clamp member includes a sensing mechanism for sensing load variations on tissue. A handle member is located at the proximal end of the transmission member for moving the clamp member relative to the cutting element and a feedback mechanism for supplying information related to the load variations. An output of the tissue cutting element is adjusted based on the sensed load variations supplied to the feedback mechanism. 
     The present disclosure further relates to a method for applying energy to tissue, including positioning an ultrasonically-actuated cutting element having a tissue contacting surface at the distal end of a transmission member, positioning a clamp member adjacent to the cutting element for clamping the tissue, and moving the clamp member relative to the cutting element via a handle member located at the proximal end of the transmission member. The method further includes sensing load variations on tissue via a sensing mechanism and supplying information related to the load variations to the ultrasonic surgical instrument via a feedback mechanism operatively coupled to the sensing mechanism. The method further includes adjusting an output of the tissue cutting element based on the sensed load variations supplied from the feedback mechanism. 
     The present disclosure further relates to an ultrasonic surgical instrument an ultrasonic transmission member having a proximal end and a distal end. The instrument further includes an ultrasonically-actuated cutting element located at the distal end of the transmission member, a clamp member supported adjacent to the cutting element and a handle member located at the proximal end of the transmission member that moves the clamp member relative to the cutting element. The proximal end includes a sensing mechanism that senses load variations and supplies information related to the load variations. An output of the tissue cutting element is adjusted based on the sensed load variations supplied to the feedback mechanism. 
     Other features that are considered as characteristic for the disclosure are set forth in the appended claims. As required, detailed embodiments of the present disclosure are disclosed herein; however, it is to be understood that the disclosed embodiments are merely examples of the disclosure, which may be embodied in various forms. 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 of ordinary skill in the art to variously employ the present disclosure in virtually any appropriately detailed structure. Further, the terms and phrases used herein are not intended to be limiting; but rather, to provide an understandable description of the disclosure. While the specification concludes with claims defining the features of the disclosure that are regarded as novel, it is believed that the disclosure will be better understood from a consideration of the following description in conjunction with the drawing figures, in which like reference numerals are carried forward. The figures of the drawings are not drawn to scale. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various embodiments of the present disclosure will be described herein below with reference to the figures wherein: 
         FIG. 1  is an illustration of components of a prior-art ultrasonic cutting device with separate power, control, drive and matching components in block diagram form; 
         FIG. 2  is a diagram illustrating the prior-art ultrasonic cutting device of  FIG. 1 ; 
         FIG. 3  is a block circuit diagram of an ultrasonic cutting device, in accordance with an example embodiment of the present disclosure; 
         FIG. 4  is a side, elevational view of a left side of an ultrasonic cutting device handle with fully integrated control, drive and matching components and removable transducer and power supply, in accordance with an example embodiment of the present disclosure; 
         FIG. 5  is a side, elevational view of the handle of  FIG. 4  with the left-side shell removed and with the upper slide cover removed to show the integrated control, drive and matching components and removable power supply therein, in accordance with an example embodiment of the present disclosure; 
         FIG. 6  is a perspective view of a transducer assembly removed from the handle of  FIG. 5 , in accordance with an example embodiment of the present disclosure; 
         FIG. 7  is a perspective and partially hidden view of the transducer assembly of  FIG. 6 , in accordance with an example embodiment of the present disclosure; 
         FIG. 8  is a perspective and partially hidden view of the pack shown in the handle of  FIG. 5 , in accordance with an example embodiment of the present disclosure; 
         FIG. 9  is a side, elevational view of an handle with the left-side shell removed to show a transducer and generator, a removable power supply, and a blade and waveguide attached to the spindle, in accordance with an example embodiment of the present disclosure; 
         FIG. 10  is a side, elevational view of an handle with the left-side shell removed to show electronic coupling between the generator and transducer assembly of the transducer and generator, in accordance with an example embodiment of the present disclosure; 
         FIG. 11  is a side, elevational view of an handle with the left-side shell removed to show a transducer, generator, and load cell, in accordance with an example embodiment of the present disclosure; 
         FIG. 12  is a side, elevational view of an handle with the left-side shell removed to show a transducer, generator, and laser interferometry configuration, in accordance with an example embodiment of the present disclosure; and 
         FIG. 13  is a laser interferometer as shown in  FIG. 12 , in accordance with an example embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Particular embodiments of the present disclosure are described hereinbelow with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail. 
     It is to be understood that the disclosed embodiments are merely examples of the present disclosure, which may be embodied in various forms. 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. Further, the terms and phrases used herein are not intended to be limiting; but rather, to provide an understandable description of the present disclosure. 
     Before the present disclosure is disclosed and described, it is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. In this document, the terms “a” or “an”, as used herein, are defined as one or more than one. The term “plurality,” as used herein, is defined as two or more than two. The term “another,” as used herein, is defined as at least a second or more. The terms “including” and/or “having,” as used herein, are defined as comprising (i.e., open language). The term “coupled,” as used herein, is defined as connected, although not necessarily directly, and not necessarily mechanically. Relational terms such as first and second, top and bottom, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms “comprises,” “comprising,” or any other variation thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by “comprises . . . a” does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element. 
     As used herein, the term “about” or “approximately” applies to all numeric values, whether or not explicitly indicated. These terms generally refer to a range of numbers that one of skill in the art would consider equivalent to the recited values (i.e., having the same function or result). In many instances these terms may include numbers that are rounded to the nearest significant figure. In this document, the term “longitudinal” should be understood to mean in a direction corresponding to an elongated direction of the object being described. 
     It will be appreciated that embodiments of the disclosure described herein may be comprised of one or more conventional processors and unique stored program instructions that control the one or more processors to implement, in conjunction with certain non-processor circuits and other elements, some, most, or all of the functions of ultrasonic cutting devices described herein. The non-processor circuits may include, but are not limited to, signal drivers, clock circuits, power source circuits, and user input and output elements. Alternatively, some or all functions could be implemented by a state machine that has no stored program instructions, or in one or more application specific integrated circuits (ASICs), in which each function or some combinations of certain of the functions are implemented as custom logic. Of course, a combination of the two approaches could also be used. Thus, methods and means for these functions have been described herein. 
     The present disclosure, according to one embodiment, overcomes problems with the prior art by providing a lightweight, hand-holdable, ultrasonic cutting device that includes a feedback mechanism for automatically adjusting, in real-time, ultrasonic waves applied to tissue. 
     Referring to  FIG. 3 , a block circuit diagram  300  is shown, which includes a microprocessor  302 , a clock  330 , a memory  326 , a power supply  304  (e.g., a battery), a switch  306  (e.g., a MOSFET power switch), a drive circuit  308  (PLL), a transformer  310 , a signal smoothing circuit  312  (also referred to as a matching circuit), a sensing circuit  314 , a transducer  316 , and a waveguide, which terminates into an ultrasonic cutting blade  318 , referred to herein simply as the waveguide  318 . The block circuit diagram  300  also includes a cannula  320  for covering and supporting the waveguide  318 . As used herein, the “waveguide-movement-generation assembly” is a sub-assembly including at least the transducer  316 , but may also include other components, such as the drive circuit  308  (PLL), transformer  310 , signal smoothing circuit  312 , and/or the sensing circuit  314 . The block circuit diagram  300  also includes a display  322 , an on/off switch  324 , and a temperature sensor  332 . 
     In operation, the output of the battery  304  is fed to and powers the processor  302 . The processor  302  receives and outputs signals and, as is described below, functions according to custom logic or in accordance with computer programs that are executed by the processor  302 . The block circuit diagram  300  may also include a main memory  326  that stores computer-readable instructions and data. 
     The output of the battery  304  is also fed to a switch  306  that has a duty cycle controlled by the processor  302 . By controlling the on-time for the switch  306 , the processor  302  is able to dictate the total amount of power that is ultimately delivered to the transducer  316 . The output of the switch  306  is fed to a drive circuit  308  that contains, for example, a phase detecting PLL and/or a low-pass filter and/or a voltage-controlled oscillator. The output of the switch  306  is sampled by the processor  302  to determine the voltage and current of the output signal (referred to in  FIG. 3  respectively as AD 2  V In and AD 3  I In). These values are used in feedback architectures to adjust the pulse width modulation of the switch  306 . 
     The drive circuit  308 , which receives the signal from the switch  306 , includes an oscillatory circuit that turns the output of the switch  306  into an electrical signal having a single ultrasonic frequency, e.g., 55 kHz (referred to as VCO in  FIG. 3 ). A smoothed-out version of this ultrasonic waveform is ultimately fed to the transducer  316  to produce a resonant sine wave along the waveguide  318 . Resonance is achieved when current and voltage are substantially in phase at the input of the transducer  316 . For this reason, the drive circuit  308  uses a PLL to sense the current and voltage input to the transducer  316  and to synchronize the current and voltage with one another. This sensing is performed over line  328 . 
     At the output of the drive circuit  308  is a transformer  310  able to step up the low voltage signal(s) to a higher voltage. It is noted that all upstream switching, prior to the transformer  310 , has been performed at low (i.e., battery driven) voltages. This is at least partially due to the fact that the drive circuit  308  advantageously uses low on-resistance MOSFET switching devices. 
       FIGS. 4 to 8  illustrate various example embodiments of a “gun” type device  1300  suitable to hold and/or contain the components illustrated in  FIG. 3 . More specifically, as shown in the cutaway view of  FIG. 5 , the ultrasonic surgical device  1300  includes a disposable ultrasonic cutting tool handle  1408  that has a water-tight sealable battery-holding compartment  1422 , a driving-wave generation circuit  1420  in electrical contact with the battery-holding compartment  1422 , a transducer attachment dock  1404  accessible from an exterior of the handle and operable to releasably physically couple the transducer  1302  to a waveguide  1310  (represented as a dotted line in  FIG. 4 ) coupled to the handle  1408  through a waveguide attachment dock  1406  that is disposed to accept and physically couple the ultrasonic waveguide  1310  to the transducer  1302 . 
     The ultrasonic surgical device  1300  includes a disposable handle body  1308  defining a battery-holding compartment  1422  shaped to receive a battery  1700  therein and operable to couple a proximal end of the ultrasonic waveguide  1310  to the ultrasonic transducer  1302  therethrough. The handle body  1308  further includes a waveguide attachment dock  1428  shaped to align and attach the proximal end of the waveguide  1310  to the transducer  1302  and thereby hold the waveguide  1310  and the transducer  1302  at least partially within the body when the transducer  1302  is docked in the transducer dock  4102  and the waveguide  1310  is docked in the waveguide attachment dock  1428 . 
     An upper portion of the handle body  1308  houses a disposable driving-wave generation circuit  1420  that is in electrical contact with the battery  1700  and the transducer  1302  when the battery  1700  and transducer are disposed, respectively, in the battery-holding compartment  1422 . The generation circuit  1420  is operable to generate an output waveform sufficient to generate ultrasonic movement along the waveguide by exciting the transducer when the transducer is coupled to the waveguide  1310 . 
     The transducer  1302  is generally secured by screwing the transducer  1302  onto a waveguide  1310 , both being at least partially within the transducer port  1404 . The physical couple between the handle  1408  and the transducer  1302 , once attached, may be water-tight and, in some embodiments, may be aseptic. The transducer  1302  imparts the physical forces to the waveguide  1310  at the proper frequency and force and receives power from the battery  1700 . The transducer assembly  1302  is shown in greater detail in  FIGS. 6 and 7  described below. 
     Referring to  FIG. 6 , the reusable cordless transducer assembly  1402  is shown separate from the device  1300 . The transducer assembly  1402  includes a shaft  1504  with an ultrasonic waveguide couple  1508  that is able to attach to a waveguide and, upon activation of the transducer shaft  1504 , excite the attached waveguide, i.e., impart ultrasonic waves along the length of the waveguide. The transducer assembly  1402  also has a housing  1506  that protects and seals the internal working components (see  FIG. 7 ) from the environment. It is advantageous for the transducer assembly  1402  to be selectively removable from the device  1300 . As a separate component, the transducer assembly  1402  may be medically disinfected or sterilized, e.g., put in an autoclave, and used for multiple surgeries, while the less-expensive gun itself may be disposable. In addition, the transducer assembly  1402  may be used in multiple guns or in the same gun up to a desired maximum number of times before it is required to be disposed. 
       FIG. 7  shows one example embodiment of the transducer assembly  1302 . Within the housing  1506  is the movable shaft  1504 . When an electric field is created in the piezoelectric crystal stack  1604  at one end  1606  of the shaft  1504 , the shaft  1504  moves laterally within and relative to the housing  1506 . In this embodiment, the waveguide coupler  1508  is male and includes threads  1610 , which are used to secure the transducer assembly  1302  to the waveguide  1310  by screwing the waveguide  1310  onto the threads  1610  with an appropriate amount of torque. In contrast, in  FIG. 6 , the waveguide coupler  1508  was female allowing the waveguide to be screwed into the waveguide coupler  1508 . 
     One feature of the transducer  1402  is its ability to mechanically and electrically connect at the same time.  FIG. 6  shows an example embodiment of electrical connector rings  1510  of the transducer  1402 . As the transducer  1402  is being coupled by the waveguide couple  1508  to a waveguide attached to the handle  1408 , the connector rings  1510  are brought into contact with, for example, a set of power contacts (not shown). The power contacts place the piezoelectric crystal stack  1604  in contact with the power source  1700  of the handle  1408 . Additionally, the transducer assembly  1302  and the transducer assembly housing  1404  may be sealed so that, in the rare event of surgical fluids contacting the transducer assembly  1302 , they do not introduce themselves into the interior of the housing  1506 . 
     The gun  1300 , according to an example embodiment of the present disclosure, has, within its handle  1408 , a power assembly  1700  (including power source  1702  and a generator  1704 ), shown in detail in  FIG. 8 . The battery  1702  within the power assembly  1700  may be a single battery or a plurality of battery cells operating as a unit. 
     The battery  1702  powers the generator  1704 , which may include some or all of the components shown in  FIG. 3  and described in detail above. Specifically, the generator  1704  powers the transducer and includes the processor  302 , the switch  306  (e.g., a MOSFET power switch), the drive circuit  308  (PLL), the transformer  310 , the signal smoothing/matching circuit  312 , and the sensing circuit  314  of  FIG. 3 . 
     As shown in  FIG. 5 , for example, the handle  1408  is also provided with a closable door  1412 , for instance, at its bottom  1401 . This provides a variety of possible assemblies. In one assembly, the gun body  1414 , which includes the transducer coupling port  1404  and the triggering mechanisms  1418 , is disposable and usually not used more than for a single surgery. 
     An example procedure for use of the device with the power assembly  1700  is explained with regard to  FIGS. 4 and 5 . In operation, a person in the sterile field opens a sealed package containing the new sterile gun body  1408  and removes it for use during the operation. The gun body  1408  may either already include the cannula  320  and waveguide  1310  (indicated with a dashed line) or may be coupled to a cannula  320  and waveguide  1310  after the package is opened. Next, the sterile (autoclaved) transducer assembly  1302  is inserted into the gun body  1408  and appropriately attached to the waveguide  1310 . The surgeon then presents the underside of the gun body  1408  (with the door  1412  open) to the circulating nurse, who drops the power assembly  1700  into the grip portion  1424  of the gun handle  1408  without contacting the exterior of the gun body  1408 . Someone in the operating field (e.g., the surgeon) then closes the door  1412 , thereby securing the non-sterile power assembly  1700  within the gun  1300  through a sterile seal  1401  and preventing it from contaminating the sterile field. Because the power assembly  1700  is sealed within the handle  1408 , it is “outside” the sterile field during surgery. 
       FIGS. 9-10  show an example embodiment of the present disclosure, which includes a waveguide  2508  with a blade  2504 , and includes the transducer and generator, as described above. 
     Referring now to  FIG. 9 , when an ultrasonic-movement-generator assembly  2502  is coupled to a handle  2514 , the transducer  2516  is caused to be releasably physically coupled to a waveguide  2508  through the transducer attachment port  2518  and waveguide attachment port  2520 . It is envisioned that the transducer assembly  2516  may be temporarily locked into a fixed rotational position so that the waveguide  2508  may be attached to the threads  1610  (see  FIG. 7 ) with sufficient force. This physical coupling between the waveguide  2508  and the transducer assembly  2516  allows the transducer assembly  2516  to impart movement to the waveguide  2508  when power is applied to the transducer assembly  2516 . 
     The gun  2500  has a spindle  2506  that attaches to the waveguide  2508 . The spindle  2506  has indentions that allow a surgeon to easily rotate the spindle  2506  and, therefore, the attached waveguide  2508  and transducer assembly  2516  that is attached to the waveguide  2508 . Such a configuration is useful for obtaining the proper cutting-blade angle during surgery. To provide for this rotation, in one example embodiment, the transducer assembly  2516  is able to rotate freely within the transducer housing  2510 . 
     During initial coupling of the transducer assembly  2516  and waveguide  2508 , all that is needed is that one of the transducer assembly  2516  and the waveguide  2508  remains relatively stationary with respect to the other. According to one example embodiment of the present disclosure, when the transducer assembly  2516  is located inside the housing  2510  (where it cannot be readily secured by the operator, for example, by holding it steady by hand when the waveguide  2508  is being secured) the ultrasonic-movement-generator assembly  2502  is provided with a button (not shown) that slides into a recess in the housing  2510  or, alternatively, by fixing the rotation of the transducer assembly  2516  at a maximum rotational angle so that, once the maximum rotation is reached, for example, 360 degrees of rotation, no additional rotation is possible and the waveguide  2508  may be screwed thereon. Of course, a maximum rotation in the opposite direction allows the waveguide  2508  to be removed as well. 
       FIG. 10  shows one example of how the generator assembly  2512  and transducer assembly  2516  are electrically coupled so that a physical rotation of the transducer assembly  2516  with respect to the generator assembly  2512  is possible. In this example, the generator assembly  2516  has a pair of contacts  2602  protruding from its underside, adjacent the transducer assembly  2516 . Proximity of the transducer assembly  2516  to the generator assembly  2512  places one of the pair of contacts  2602  (circled) in physical communication with a pair of contact rings  2604  at the transducer body  2610  so that a driving signal may be steadily applied to the transducer assembly  2516  when needed. Advantageously, the pair of contacts  2602  maintains electrical contact regardless of an angle of rotation of the transducer assembly  2516 . Therefore, the transducer assembly  2516  may rotate without any limitations as to the maximum angle or number of rotations. 
     Referring to  FIGS. 4-10 , and especially to  FIG. 9 , the example embodiments of the present disclosure include a feedback mechanism. For instance, a plurality of sensors  2570  (see  FIG. 9 ) may be located at the blade  2504  of the gun  2500 . The plurality of sensors  2570  may be connected to a feedback mechanism  2574  via one or more wires  2572  extending from the distal end to the proximal end of the gun  2500 . The one or more wires  2572  are positioned within the waveguide  2508 . However, one skilled in the art may contemplate an external configuration of wires for linking the plurality of sensors  2570  to the feedback mechanism  2574 . The feedback mechanism  2574  may be positioned within the handle  2514  or any other portion of the gun  2500 . The feedback mechanism  2574  may even be positioned on an outer portion of the gun  2500 . 
     The feedback mechanism  2574  may be provided to interact with any sensors  2570  provided to enable more effective ligation, cutting, dissection, coagulation, etc. For example, the feedback mechanism  2574  may terminate operation of the gun  2500  if one or more sensors of the plurality of sensors  2570  indicate that tissue temperature or ultrasonic or electrical impedance has exceeded a predetermined maximum. The feedback mechanism  2574  may be selectively activated and deactivated and/or controlled or monitored by a surgeon to provide the surgeon with more flexibility in operating the gun  2500 . Activating or exciting the end effector of gun  2500  at ultrasonic frequencies induces longitudinal vibratory movement that generates localized heat within adjacent tissue, facilitating both cutting and coagulating. 
     The transducer  2516  may be constructed of one or more piezoelectric or magnetostrictive elements in the handle  2514 . Vibrations generated by the transducer  2516  are transmitted to the blade  2504  via an ultrasonic waveguide extending from the transducer  2516  to the surgical end effector. The waveguides  2504 ,  2508  are designed to resonate at the same frequency as the transducer  2516 . When a blade  2504  is attached to the transducer  2516 , the overall system frequency may be the same frequency as the transducer  2516  itself. However, it is contemplated that the transducer  2516  and the blade  2504  may be designed to resonate at two different frequencies and when joined or coupled may resonate at a third frequency. 
     The blade  2504  of the gun  2500  operates or vibrates at a frequency of about 55 kHz when no tissue is applied to the tip. When tissue is applied to the tip, the tip or blade  2504  may vibrate at a frequency other than 55 kHz. Such frequency depends on, for example, the thickness of the tissue. Thus, the tissue applies a load to the blade  2504 . The load is a variable load that may change as the gun  2500  is used during a surgical procedure. The example embodiments of the present disclosure enable the gun  2500  to determine what is causing the load when the gun  2500  is activated. The load may be caused by a number of variables or parameters. For example, such load varying parameters may include, but are not limited to tissue impedance, tissue type, tissue clarity, tissue compliance, and temperature of the tissue. 
     The waveguide  2508  or blade  2504  may also include a plurality of sensors  2570  for measuring a number of different variables or parameters, such as, but not limited to temperature of the cutting element, water content in tissue, water motality in tissue, and energy delivery. The sensors  2570  may measure one or more parameters (or variables) associated with the tissue or with the gun  2500  and relay such information back to a controller mechanism (not shown) within the gun  2500  which operatively communicates with other controllers to adjust, in real-time, and in an automatic manner, the one or more sensed and measured parameters based upon the information provided by sensors  2570 . 
     These changes in the movement of the waveguide  2508  and/or blade  2504  are measured and fed back into controllers (not shown) of the gun  2500  to provide for automatic, real-time adjustments of the one or more parameters. Thus, movement, vibration, waves, and/or resonance produced by a plurality of parameters or variables may be continuously measured in real-time (as load differentials) and fed back into the controllers in order to automatically readjust such parameters or variables. Movement, vibration, waves, and/or resonance may be measured on any portion of the gun  2500  and/or on any portion of the tissue applied to the blade  2504 . Further, the energy source of the gun  2500  may be responsive to a power control signal of a controller. The feedback mechanism  2574  may be coupled to, or included with, the power controller. The power controller may include at least one electrical switch for selectively controlling the energy supplied to the instrument to coagulate tissue, or to cut tissue, depending on the electrical switch setting. In other words, any type of manual or automatic feedback mechanism  2574  may be envisioned by one skilled in the art. 
     The controllers may be any type of electrical, or electro-mechanical mechanism that provides additional force on a drive assembly (not shown) to modify/alter/readjust one or more parameters of the blade  2504  or waveguide  2508  of the gun  2500 . Thus, in the automated system, the characteristics of the tissue are monitored and adjusted during activation based upon a continually-sensed surgical condition from the sensors  2570  relating to any one or more of a series of tissue or waveguide parameters (e.g., tissue impedance, tissue type, tissue clarity, tissue compliance, temperature of the tissue or jaw members, water content in tissue, jaw opening angle, water motality in tissue, energy delivery, etc.) utilizing an open or closed feed back control loop. 
     In one embodiment, temperature sensors  2570  may be disposed on the waveguide  2508 . The temperature sensors  2570  may be a thermocouple probe having thermocouple wires twisted together and soldered together at a junction. The temperature sensors  2570  may provide temperature feedback to the feedback mechanism  2574 , which may then adjust the power delivered to the distal end of the gun  2500  in response to the temperature readings. In other words, when the temperature reaches the desired level for the selected function, indicating a desired tissue condition, a signal is provided to a control unit or the user, at which time the energy supply is switched off or attenuated. The feedback signal may, for example, provide a visual, audible or tactile signal to a user, and/or may provide instructions to a control unit to automatically readjust the energy supply to the tissue. Of course, such steps may be taken in regards to any parameter that is being sensed and measured by the gun  2500 . 
     In addition to temperature feedback, the gun  2500  may also be configured to interrogate tissue to determine various tissue properties. In one embodiment, the transducer  2516  is energized to produce an ultrasound interrogation pulse (e.g., A-mode ultrasound). The interrogation pulse may be transmitted periodically during the procedure or after the commencement thereof to determine, for instance, the thickness or type of tissue being grasped at the distal end of the gun  2500 . The interrogation pulse may be of different frequency and amplitude than the treatment pulses used to seal tissue. 
     In summary, the feedback mechanism  2574  may supply a variety of information related to one or more parameters to the ultrasonic surgical instrument or gun  2500 . According to the information received by the ultrasonic surgical instrument or gun  2500 , the one or more parameters may be adjusted based on load variations created by the tissue. The load variations include resonance or vibration patterns located across a length of the instrument or gun  2500 . Specifically, the load variations may be located and measured at the cutting element (blade  2504 ), the clamp member  2576 , the handle member (handle  2514 ) or the ultrasonic transmission member (waveguide  2508 ). Additionally, the information may include ultrasonic wave information, where the ultrasonic wave information is used to adjust one or more power levels of waves applied to the tissue. The information received by the gun  2500  may be automatically provided in real-time during electrical activation of the gun  2500  for enabling automatic adjustment of the one or more parameters. Also, the energy applied to the tissue may be continuously and automatically regulated as a function of the load variations. 
     The ultrasonic transmission member or waveguide  2508  may be constructed from titanium, where the titanium expands/elongates and contracts/shrinks along a longitudinal direction during electrical activation of the gun  2500 . Of course, the waveguide  2508  may be fabricated from aluminum, steel, or any other suitable material. In the example embodiments, when the titanium member is heated by an electric current, the titanium expands and when cooled the titanium returns to its original dimensions. The variation of the titanium dimensions may be one parameter sensed, measured, and adjusted by the gun  2500 . Thus, energy applied to the distal end of the gun  2500  may be adjusted based on the expansion and contraction of the materials used to fabricate and/or manufacture the components/elements of the gun  2500 . Of course, one skilled in the art may contemplate a sensing, measuring, and adjusting a plurality of different variables in order to determine load differential due to tissue application. 
     Moreover, the load variations may be measured by load cells  2700  (as shown in  FIG. 11 ) or the load variations may be measured by a laser interferometry configuration  2710  (as shown in  FIGS. 12 and 13 ). A load cell  2700  may be a type of transducer that converts physical force into measurable, quantifiable electric energy. Because of the various types of load cells  2700  needed to operate different pieces of machinery, there are many configurations, but the most popular are of the strain gauge variety. This is a device which measures strain, and then transfers that force into electric energy which manifests as measurement for operators of the machinery. One skilled in the art may envision using hydraulic, pneumatic, and/or strain gauge load cells  2700  in accordance with the example embodiments of the present disclosure. Additionally, interferometry is a technique of diagnosing the properties of two or more lasers or waves by studying the pattern of interference created by their superposition. The instrument used to combine the waves together is called an interferometer. Interferometry makes use of the principle of superposition to combine separate waves together in a way that causes the result of their combination to have some meaningful property that is diagnostic of the original state of the waves. Both the load cells  2700  and the laser interferometry configuration  2710  may be located within the handle  2514 . Of course, the load cells  2700  and the laser interferometry configuration  2710  may be located on any external or in any internal location of the gun  2500  (e.g., such as in the main body of the gun  2500 ). 
     The sensing methods (e.g.,  2700  and  2710 ) described above may be based on analyzing the interferometric features associated with the reverberation of ultrasound in a medical instrument, such as the gun  2500 . Reflected light from a continuous source (not shown) may be detected by the interferometer to probe the ultrasonic vibrations across the various portions of the gun  2500 . Motions or vibrations or waves along the gun  2500  at ultrasonic frequencies generate a shift in the frequency of the continuous light source. This modulation of the continuous light source frequency may be monitored by the interferometer and may be converted to a signal that is recorded and processed by, for example, a processor or a computer. Signal processing may involve identifying the resonance frequencies of ultrasonic motion across different surfaces of the gun  2500 . These resonant frequencies, in conjunction with some physical properties of the material of the gun  2500  may be used to determine, for example, whether to automatically shut off the gun  2500 . Additionally, measurements of the intensity of the scattered laser light at the output of the interferometer may be used to generate a prestabilization signal. Also, the intensity of the scattered laser light at the input of the interferometer may be measured to generate a reference signal. These measurements may be used to electronically generate a ratio signal indicative of the ratio between the reference signal and the pre-stabilization signal and processing of the ratio signal may be used to generate a final stabilization signal which is used to ensure a proper operation of the interferometer. Thus, the phase of the returned ultrasound signals could be used to perform interferometry to locate any changes in one or more desired parameters to be monitored. 
     Any type of interferometer known in the art may be used. For example, the interferometer used in embodiments of the present disclosure may include, but not be limited to, time delay interferometers (TD-LCI), such as, scanning Michelson interferometers and autocorrelators, and optical frequency domain interferometers (OFDI), such as, spectral domain low-coherence interferometers, and these interferometers may be used to detect interference between one or more reference optical signals and one or more backscattered sample optical signals or birefringence caused by the sample. Such optical probes may be embedded in the gun  2500  or may be located on the outer surfaces of the proximal end of the gun  2500 . 
     Moreover, the sensing mechanism may be used as a safety mechanism for the gun  2500 . For example, the sensing mechanism may sense that no tissue or no object is found between the jaws of the blade  2504  and automatically shut off operation of the gun  2500 . The advantages of using load cells  2700  or an interferometer  2710  as discussed with reference to  FIGS. 11-13  may include (1) calibration of the interferometric apparatus in real-time, (2) automatically stabilizing frequencies across a medical instrument, and/or (3) providing an improved sensing method and apparatus useful for ultrasonic non-destructive testing of the medical instrument. 
     Concerning feedback mechanism, several types of feedback systems may be used. For example, a pressure detector or strain gauge may be used to detect tissue presence, status or type. Electrical parameters may be used to sense and determine the variation in load conditions on the cutting element as acoustical impedance is related to the system impedance of the generator and instrument. In such a system, either phase differences of voltage and current or magnitude ratios of voltage and current supplied to the transducer  2516 , are used to make this determination. In addition to the feedback mechanism  2574 , a method of performing the present disclosure may include the steps of supplying ultrasonic energy to tissue, supplying high-frequency electrical energy to tissue, sensing and measuring one or more tissue parameters or waveguide parameters, and altering or readjusting the output of the ultrasonic generator in response to measured tissue or waveguide parameters in a continuous and automatic manner in real-time. 
     It is also contemplated that operation of gun  2500  may be automatically controlled through the use of a computer, for example, in a wireless manner. In one alternative embodiment of the presently disclosed system, a computer (not explicitly shown) may receive data from the sensors  2570  positioned on the blade  2504  of the gun  2500 . As discussed above, sensors  2570  may be provided to monitor different characteristics of the tissue being operated upon including, inter alia, temperature and/or ultrasonic or electrical impedance. The computer may include circuitry to process an analog signal received from the sensors  2570  and to convert the analog signal to a digital signal. This circuitry may include means to amplify and filter the analog signal. Thereafter, the digital signal may be evaluated and operation of the gun  2500  (e.g., application of energy) may be modified to achieve the desired effect in or on the tissue and prevent damage to surrounding tissue. Thus, all the information gathered by the sensors  2570  may be wirelessly transferred to the computer in a local or remote location for further processing (e.g., tracking and recording historical information/data), as discussed below. 
     As stated, the information gathered (e.g., from the computer described above) may be stored separately in a local or remote database for further processing. This may be a unique database designed solely for storing and analyzing such different types of information/data. Also, once a history of adjustments are collected and stored for each of the one or more parameters, that history may be evaluated in the future for determining which parameter modifications achieved the best desired results for the surgeon. In other words, the parameter changes that took place (past changes) may be stored and later compared against each other and ranked in order of best achieved results. 
     In addition to the advantages of reduced cost, reduced size, elimination of a tethering cord for supplying power and carrying signals, real-time feedback, and automatic energy application adjustment, the present disclosure provides unique advantages for maintaining a sterile environment in an operating or other environment. More specifically, in example embodiments of the present disclosure, the handle includes an aseptic seal. An “aseptic” seal, as used herein, means a seal that sufficiently isolates a compartment (e.g., inside the handle) and components disposed therein from a sterile field of an operating environment into which the handle has been introduced so that no contaminants from one side of the seal are able to transfer to the other side of the seal. 
     Although specific embodiments of the present disclosure have been disclosed, those having ordinary skill in the art will understand that changes may be made to the specific embodiments without departing from the spirit and scope of the disclosure. The scope of the disclosure is not to be restricted, therefore, to the specific embodiments, and it is intended that the appended claims cover any and all such applications, modifications, and embodiments within the scope of the present disclosure. 
     From the foregoing, and with reference to the various figure drawings, those skilled in the art will appreciate that certain modifications may also be made to the present disclosure without departing from the scope of the same. While several embodiments of the disclosure have been shown in the drawings and/or discussed herein, it is not intended that the disclosure be limited thereto, as it is intended that the disclosure be as broad in scope as the art will allow and that the specification be read likewise. Therefore, the above description should not be construed as limiting, but merely as exemplifications of particular embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.