Bimodal Ultrasonic Handpiece System

Abstract

The ultrasonic handpiece includes a piezoelectric assembly. A control signal drives the piezoelectric assembly in a first vibration mode and a second vibration mode simultaneously. Feedback of a resultant vibration of the piezoelectric assembly is generated in the first mode and the second mode. Based on the feedback, the frequency of each of the first mode and the second mode is independently adjusted as necessary such that the resultant vibration of each of the first mode and the second mode is approximately at a respective resonant frequency.

Description

[Technical field]

[0001] Disclosed herein are example ultrasound systems and methods for controlling ultrasound devices. In some examples, systems and methods for operating an ophthalmic phacoemulsification ultrasound handpiece are disclosed. [Background technology]

[0002] A typical ultrasonic surgical device / system suitable for ophthalmic surgery includes an ultrasonically driven handpiece, an attached hollow working tip, an irrigation sleeve, and an electronic control console. The handpiece assembly is attached to the control console by an electrical cable and flexible tubing. Via the electrical cable, the console varies the power level transmitted from the handpiece to the attached working tip, and the flexible tubing is used to deliver irrigation fluid to and withdraw aspirate fluid from the eye via the handpiece assembly.

[0003] In some examples of such devices, the functional part of the handpiece is a centrally located hollow resonating bar or horn attached directly to a set of piezoelectric crystals forming a piezoelectric assembly. The crystals provide the necessary ultrasonic vibrations required to drive both the horn and the attached working tip in phacoemulsification and are controlled by a console. The crystal / horn assembly is suspended within the hollow body or shell of the handpiece. The handpiece body terminates in a reduced diameter section or nose cone at the distal end of the body. The nose cone is externally threaded to receive the irrigation sleeve. Similarly, the horn bore is internally threaded at its distal end to receive the external threads of the working tip. The irrigation sleeve also has an internally threaded bore that screws onto the external threads of the nose cone. The working tip is adjusted so that the tip protrudes a predetermined amount beyond the open end of the irrigation sleeve.

[0004] When used to perform phacoemulsification, the working tip and the end of the irrigating sleeve are inserted into a small incision of a predetermined width in the cornea, sclera, or elsewhere in ocular tissue to access the anterior chamber of the eye. The working tip is ultrasonically vibrated along its longitudinal axis within the irrigating sleeve by a crystal-driven ultrasonic horn, thereby emulsifying selected tissue in situ on contact. The hollow bore of the working tip communicates with the bore of the horn, which in turn communicates with an aspiration line from the handpiece to the console. A reduced pressure or vacuum source within the console draws or aspirates the emulsified tissue from the eye through the open end of the working tip, the bore of the working tip, the bore of the horn, the aspiration line, and into a retrieval device. Aspiration of the emulsified tissue is aided by a saline flushing solution or irrigant that is injected into the surgical site through a small annular gap between the inner surface of the irrigating sleeve and the outer surface of the working tip. Summary of the Invention

[0005] In some examples herein, a system is disclosed for operating an ultrasonic handpiece tool including a piezoelectric element assembly. In some examples, the system applies a control signal to drive the piezoelectric element assembly in a first vibration mode and a second vibration mode simultaneously. In some examples, the system generates feedback of a resultant vibration of the piezoelectric element assembly in the first mode and the second mode. In some examples, based on the feedback, the system adjusts the frequency of each of the first mode and the second mode independently as needed such that the resultant vibration of each of the first mode and the second mode is approximately at the respective resonant frequency. In some examples, a method is disclosed for operating an ultrasonic device in a first vibration mode and a second vibration mode. In some examples, based on the feedback, the method includes adjusting the frequency of each of the first mode and the second mode independently as needed such that the resultant vibration of each of the first mode and the second mode is approximately at the respective resonant frequency.

[0006] Further embodiments, details, advantages and modifications will become apparent from the following detailed description of illustrative embodiments, which is to be read in conjunction with the accompanying drawings. [Brief description of the drawings]

[0007] [Figure 1] 1 is a perspective view and block diagram of a bimodal ultrasonic handpiece system according to some examples. [Diagram 2] FIG. 2 is a detailed block diagram of the ultrasonic handpiece system of FIG. 1, according to some examples. [Figure 3A-3B] FIG. 3A shows a prior art timing diagram for operating an ultrasonic handpiece using a controller, and FIG. 3B shows a timing diagram for operating an ultrasonic handpiece using the controller of FIG. 2 according to some examples. [Figure 4] FIG. 13 is a detailed block diagram of a bimodal ultrasonic handpiece system according to a further example. [Diagram 5] 5 is a detailed block diagram of the longitudinal quadrature amplitude demodulator and the twisted quadrature amplitude demodulator of FIG. 4, in accordance with some examples. [Figure 6] FIG. 13 is a detailed block diagram of a bimodal ultrasonic handpiece system according to a further example. [Figure 7] 7 is a detailed block diagram of the longitudinal quadrature demodulator and the twisted quadrature demodulator of FIG. 6, in accordance with some examples. [Figure 8] 2 is a flow diagram of an example of the functionality of the controller of FIG. 1 for simultaneously providing multiple vibration modes to an ultrasonic handpiece via a single piezoelectric element assembly, according to certain examples disclosed herein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] In some exemplary embodiments, an ultrasonic system for controlling an ultrasonic handpiece such that multiple vibration modes, i.e., longitudinal and torsional motions, can be applied simultaneously using a single piezoelectric element assembly is disclosed. In other exemplary embodiments, a method for controlling an ultrasonic handpiece in multiple vibration modes, i.e., longitudinal and torsional motions, simultaneously using a single piezoelectric element assembly is disclosed.

[0009] Reference will now be made in detail to exemplary embodiments of the present disclosure, some of which are illustrated in the accompanying drawings. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be apparent to those skilled in the art that the present disclosure may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail so as not to unnecessarily obscure aspects of the embodiments. Wherever possible, like reference numbers have been used to refer to like elements.

[0010] FIG. 1 is a perspective view and block diagram of a bimodal ultrasonic handpiece system 10 according to some exemplary embodiments. The system 10 may be used, for example, to perform phacoemulsification. FIG. 1 includes a perspective view of the handpiece 5 with the outer case removed and a block diagram of a controller 60 that controls the handpiece 5. The handpiece 5 includes an ultrasonic horn 12, for example made from a titanium alloy. The horn 12 has a plurality of helical slits. A plurality (usually one or more pairs) of piezoelectric elements or crystals form a piezoelectric element assembly 14. The piezoelectric elements or crystals may be ring-shaped and held against the horn 12 by a compression nut 15. Some handpieces may include multiple piezoelectric element assemblies 14, each physically separated from one another along the longitudinal axis of the handpiece 5, each forming a separate assembly / package. Each piezoelectric element assembly 14 may be separately electrically coupled to the controller 60.

[0011] An aspiration shaft or aspiration tube 16 extends along the length of the handpiece 5 through the horn 12, the piezo assembly 14, the nut 15, and a plug 18 at the proximal end of the handpiece 5. The aspiration tube 16 passes through a hollow working tip 20 attached to the horn 12, allowing material to be aspirated through and out of the handpiece 5. Although the hollow working tip 20 is shown as a straight tip, other tip configurations (e.g., a bent tip) can be used. The plug 18 provides a fluid-tight seal to the outer shell of the handpiece 5, allowing the handpiece 5 to be autoclaved without adversely affecting the piezo assembly 14. An additional groove 22 may be provided in the horn 12 for sealing an O-ring gasket (not shown).

[0012] 1 shows the locations of the longitudinal and torsional nodes (points where the velocity of each mode is zero) of the handpiece 5. The torsional node 26 is preferably located at the proximal longitudinal node 28 such that the torsional node 26 and the longitudinal node 28 are coincident, e.g., both located on the plug 18. The handpiece 5 also includes a distal longitudinal node 30 located at the reduced diameter portion 32 of the horn 12.

[0013] The controller 60 is typically located remotely from the handpiece 5 and may be part of an electronic control console (not shown). The controller 60 is coupled to the handpiece 5 at the piezo assembly 14 via an electrical cable or connector 65, or may be coupled via other communication means such as wireless. The electronic control console is further coupled to the handpiece 5 via flexible tubing (not shown) for irrigation and aspiration.

[0014] Controller 60 includes a processor 40, a memory 42, and a controller circuit 50. Processor 40 may be any type of general-purpose processor or may be a processor designed specifically for handpiece 5, such as an application specific integrated circuit ("ASIC"). Processor 40 may be the same processor that runs the entire system 10, or it may be a separate processor.

[0015] The memory 42 may be any type of storage device or non-transitory computer readable medium, such as random access memory ("RAM") or read only memory ("ROM"). The memory 42 stores instructions executed by the processor 40, including instructions to simultaneously (i.e., at the same time) provide multiple vibration modes (e.g., bimodal) via the single piezoelectric element assembly 14, as well as other functionality disclosed herein. The controller circuitry 50 also provides functionality to provide multiple vibration modes simultaneously via the single piezoelectric element assembly 14, in addition to the functionality of the processor 40. In an exemplary embodiment, the functionality disclosed herein may be provided by a combination of the processor 40 and memory 42 (i.e., software-based), or the controller circuitry 50 (i.e., hardware-based), or both.

[0016] Control of ultrasonic motion for a handpiece such as handpiece 5 can be implemented by a number of different methods. One method involves a control loop that servos the frequency of the drive voltage by using the electrical impedance of the piezoelectric drive transducer as feedback. In such a method, the impedance feedback of the piezoelectric transducer is calculated as the ratio of the root mean square ("RMS") value of the transducer drive voltage to the RMS value of the drive current.

[0017] In certain instances, it is advantageous to utilize two or more different vibration modes in an ultrasonic handpiece, such as orthogonal longitudinal and torsional modes, however, each vibration mode has a distinct resonance of operation that must be independently controlled to maintain an optimal operating frequency in response to various influences such as load and temperature.

[0018] In some known ultrasonic handpiece systems, the handpiece is controlled to provide ultrasonic longitudinal motion of the cutting tip and rotational / torsional motion of the tip. Such known ultrasonic handpiece systems for phacoemulsification may include a drive circuit that monitors both the torsional and longitudinal modes and controls these modes using two different drive frequencies. The torsional drive signal is approximately 31 kHz (kilohertz) and the longitudinal drive signal is approximately 45 kHz, although these frequencies may vary depending on the piezoelectric element assembly 14 used, as well as the size and shape of the horn 12 and slit 24. The frequencies of both the longitudinal and torsional modes are tracked and controlled such that the frequencies of these motions are generally at their respective resonant frequencies when applied.

[0019] However, known systems for providing both longitudinal and torsional motion typically alternate between these motions on a single piezoelectric element assembly 14, or use multiple different piezoelectric element assemblies 14 for each different motion. Known systems are unable to simultaneously determine the resonant frequencies of both modes, and are unable to simultaneously make the necessary adjustments to the operating frequencies of both modes to maintain their optimal resonant frequencies in response to various frequency shifting factors, such as temperature.

[0020] FIG. 2 is a detailed block diagram of an ultrasonic handpiece system 10, according to some examples. FIG. 2 shows details of a controller 60 coupled to an ultrasonic handpiece 5. In general, in FIG. 2, the controller 60 tracks the resonance by measuring the electrical impedance (i.e., voltage and current measurements) reflected to the primary side of the output transformer 102. The RMS value voltage is measured by an RMS-to-DC converter RMS / DC 106 and a voltage sense 104, and the current (simultaneous with the voltage) is measured by an RMS / DC 107 and a current sense 105, as well as A / D (analog-to-digital) converters 110 and 111. The measurements generate an impedance feedback 120 ("Z(t)"). Based on the measured impedance feedback, control loops 130 and 131 adjust the frequency to maintain the resonant frequency. The longitudinal control 130 and the torsional control 131 provide separate adjustments using switch functions 140 and 141, which are always in either the longitudinal control position or the opposite position for the torsional control position, as shown in FIG. 2.

[0021] In the embodiment of Figure 2, when multiple vibration modes are operated, the RMS values ​​of the measured voltage and resulting current are indicative of the sum of all component frequencies present in the measured voltage and current signals. As a result, the embodiment of Figure 2 does not allow for independent isolation of information (i.e., impedance magnitude) for each controlled resonance.

[0022] FIG. 3A shows a prior art timing diagram for operating an ultrasonic handpiece using a controller similar to controller 60 of FIG. 2, but with different control functions. In FIG. 3A, torsional and longitudinal modes are applied separately to a single piezoelectric element 14. Specifically, at 301, torsional mode is applied and longitudinal mode is off (i.e., when 140 and 141 are switched to torsional control). At 302, longitudinal mode is applied and torsional mode is off (i.e., when 140 and 141 are switched to longitudinal control). During "dead" times 304 and 305, neither mode is applied and each previously applied mode is adjusted by either control loop 130 or 131 to maintain its respective resonant frequency based on impedance feedback. This "dead" time is necessary to allow the energy of one mode to decay before exciting another mode. However, because the alternating vibration modes are multiplexed in time, as opposed to being applied simultaneously, as shown in FIG. 3A, tissue cutting efficiency is sacrificed when used to perform, for example, phacoemulsification.

[0023] FIG. 3B illustrates a timing diagram for operating an ultrasonic handpiece 5 using the controller 60 of FIG. 2, according to some exemplary embodiments. In contrast to FIG. 3A, in periods 321-324, both longitudinal and torsional modes are simultaneously applied to a single piezoelectric element 14 (i.e., exciting the piezoelectric element at both longitudinal and torsional frequencies simultaneously) while maintaining independent control of each vibration mode. In feedback periods 331 and 332, the longitudinal mode is turned on to allow the torsional energy to dissipate, and the torsional mode is turned off to obtain longitudinal impedance feedback samples. Similarly, in feedback periods 341 and 342, the torsional mode is turned on to allow the longitudinal energy to dissipate, and the longitudinal mode is turned off to obtain torsional impedance feedback samples.

[0024] FIG. 3B provides feedback timing such that the simultaneous application of multiple vibration modes may be maintained at a high duty cycle. In the timing shown in FIG. 3B, the simultaneous application of multiple vibration modes to a single piezoelectric element 14 is activated approximately 80% of the time. In this mode of operation, long periods of simultaneous drive periods 321-324 are alternated in time followed by short periods of feedback measurement periods 331, 332, 341, 342. Each feedback period is used to sample the feedback of one vibration mode, and alternating feedback periods alternate between the modes of feedback. In one example, each simultaneous drive period 321-324 may last 8 ms (milliseconds) followed by a 2 ms feedback measurement period 331, 341, 332, 342.

[0025] FIG. 4 is a detailed block diagram of an ultrasonic handpiece system 10 according to a further exemplary embodiment. In contrast to the embodiment of FIG. 2 and FIG. 3B, where the simultaneous application of multiple vibration modes to a single piezoelectric element 14 is active less than 100% of the time, for example about 80% of the time, in FIG. 4 the simultaneous application is active 100% of the time. Furthermore, in contrast to the embodiment of FIG. 2 and FIG. 3B, which samples the RMS values, in FIG. 4 the composite voltage 401 and composite current 402 are sampled so that the magnitude and phase of each of the independent vibration modes can be extracted. FIG. 4 includes a longitudinal quadrature amplitude demodulator 410 and a torsional quadrature amplitude demodulator 411 that extract the specific vibration mode feedback. The extracted longitudinal impedance magnitude 424 ("Zl(t)") and torsional impedance magnitude 425 ("Zt(t)") are then fed back to control loops 420 and 421, respectively. The function of FIG. 4 continuously and simultaneously applies feedback to multiple drive modes and each vibration mode as follows: "mode1" is the longitudinal mode (in FIG. 4, "ωl" is the longitudinal angular frequency (radian / second), and "ωlt" is the longitudinal angular frequency multiplied by time (seconds)), and "mode2" is the torsional mode (in FIG. 4, "ωt" is the torsional frequency (radian / second), and "ωtt" is the torsional angular frequency multiplied by time (seconds)).

number

[0026] FIG. 5 is a detailed block diagram of a longitudinal quadrature amplitude demodulator 410 and a torsional quadrature amplitude demodulator 411 that may be used in the example of FIG. 4, according to some exemplary embodiments. As shown in FIG. 5, the demodulators 410 and 411 implement equation (1) above and provide a mixing function that separates the sinusoidal signals resulting from the longitudinal and torsional forces generated simultaneously on a single piezoelectric element 14. In contrast, the embodiment of FIG. 2 does not digitize the entire sinusoidal signal, since it only digitizes the envelope of the RMS value. FIG. 5 is a digitized composite signal used to extract the amplitude / magnitude information of each vibration mode. In FIG. 5, "V" refers to voltage, "I" refers to current, "θ" refers to current phase angle, and "φ" refers to voltage phase angle.

[0027] Figure 6 is a detailed block diagram of an ultrasonic handpiece system 10 according to a further exemplary embodiment. The embodiment of Figure 6 is similar to the embodiment of Figure 4, except that instead of using the magnitude of the impedance for feedback, the phase of the impedance is used. A longitudinal quadrature demodulator 610 generates longitudinal phase feedback 624 ("Δl(t)") and a torsional quadrature demodulator 611 generates torsional phase feedback 625 ("Δt(t)").

[0028] Figure 7 is a detailed block diagram of a longitudinal quadrature demodulator 610 and a twisted quadrature demodulator 611 that may be used in the example of Figure 6, according to some exemplary embodiments, which are used to extract phase information.

[0029] In another embodiment, the controller combines aspects of the controller 60 of Figure 4 and the controller 60 of Figure 6 to improve the stability of the feedback control, minimize losses, and improve efficiency. In one embodiment, both amplitude / magnitude and phase control are combined.

[0030] In another embodiment, both the primary and secondary side of the transformer resonant frequency are combined (as opposed to the embodiments of Figures 2, 4 and 6 where only the primary resonant frequency is monitored). Instead of feedback control to find the primary resonant frequency, the embodiment includes two feedback loops such that the phase is appropriately adjusted based on achieving the best secondary frequency and the outer loop drives the amplitude to achieve the primary resonant frequency.

[0031] In another embodiment, a non-linear feedback control of the frequency is implemented, where the controller gain and integral time are automatically adjusted in response to the control error.

[0032] 8 is a flow diagram of an example of the functionality of the controller 60 of FIG. 1 for simultaneously providing multiple vibration modes to the ultrasonic handpiece 5 via a single piezoelectric element 14, according to one embodiment. In one embodiment, the functionality of the flow diagram of FIG. 8 is implemented by software stored in a memory or other computer readable or tangible medium and executed by a processor. In other embodiments, the functionality may be performed by hardware (e.g., through the use of an application specific integrated circuit ("ASIC"), a programmable gate array ("PGA"), a field programmable gate array ("FPGA"), etc.), or any combination of hardware and software.

[0033] At 802, multiple drive vibration modes are simultaneously applied to an ultrasonic handpiece via a single piezoelectric element. In an embodiment, the multiple vibration modes are a torsional drive signal, for example at about 31 kHz, and a longitudinal drive signal, for example at about 45 kHz. In other embodiments, other frequencies may be used. Each mode has a resonant frequency of operation that should be maintained to optimize efficiency and effectiveness.

[0034] At 804, feedback of the applied vibration modes is generated. In one embodiment, the feedback is based on the RMS value of each of the modes. In another embodiment, the feedback is based on the magnitude of the combined modes. In another embodiment, the feedback is based on the phase of the combined modes. In some embodiments, the feedback is generated at an interim period when only one of the modes is applied. In other embodiments, the feedback is generated simultaneously when both modes are applied.

[0035] Based on the feedback, each of the applied modes is adjusted, if necessary, to maintain the resonant frequency at 806. Adjustments may include independently adjusting the frequencies of the components of the drive voltage so that the resulting vibration of each mode is approximately at its resonant frequency.

[0036] Experimental phacoemulsification results compared known systems in which longitudinal and torsional modes are applied separately to a single piezoelectric element ("separate") (e.g., FIG. 3A) against an embodiment of the present invention in which longitudinal and torsional modes are applied simultaneously to a single piezoelectric element ("simultaneous"). The results showed that the average phacoemulsification time was 5.48 seconds per milligram ("s / mg") for separate versus 2.79 s / mg for simultaneous. The average efficiency was 6.79 Joules per milligram ("J / mg") for separate versus 1.09 J / mg for simultaneous. The total efficiency improvement for simultaneous versus separate is a 49.13% time reduction.

[0037] As disclosed, embodiments operate an ultrasound handpiece, such as a phacoemulsifier, by simultaneously applying multiple vibration modes using a set of piezoelectric elements forming a piezoelectric element assembly.

[0038] The features, structures, or characteristics of the present disclosure described throughout this specification may be combined in any suitable manner in one or more embodiments. For example, the use of "one embodiment," "some embodiments," "certain embodiment," "certain embodiment," or other similar words throughout this specification refers to the fact that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the present disclosure. Thus, the appearance of the phrases "one embodiment," "some embodiments," "certain embodiment," "certain embodiment," or other similar words throughout this specification do not necessarily all refer to the same embodiments, and the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0039] Those skilled in the art will readily appreciate that embodiments such as those described above may be implemented with steps in a different order and / or elements in a different configuration than those disclosed. Thus, while the present disclosure has in mind the embodiments outlined, it will be apparent to those skilled in the art that certain modifications, variations, and alternative configurations are apparent without departing from the spirit and scope of the present disclosure. Accordingly, reference should be made to the appended claims to determine the metes and bounds of the present disclosure.

Claims

1. 1. A method of operating an ultrasonic handpiece comprising a piezoelectric element assembly, the method comprising: applying a control signal to drive the piezoelectric element assembly in a first vibration mode and a second vibration mode simultaneously; generating a feedback of a resultant vibration of the piezoelectric element assembly in the first mode and in the second mode; adjusting, based on the feedback, the application of the control signal such that the resultant vibration in the first mode and the resultant vibration in the second mode are each at approximately a respective resonant frequency; A method comprising:

2. The method of claim 1 , wherein the first vibration mode comprises longitudinal motion and the second vibration mode comprises torsional motion.

3. The method of claim 1 , wherein the ultrasound handpiece comprises a phacoemulsifier.

4. 2. The method of claim 1, wherein generating the feedback comprises determining a root mean square (RMS) value of a measured voltage and a resulting current in each of the first and second modes.

5. The method of claim 1 , wherein generating the feedback comprises determining a composite voltage and current magnitude of the resulting oscillation.

6. The method of claim 1 , wherein generating the feedback comprises determining a composite voltage and a composite current phase of the resulting oscillation.

7. The method of claim 1 , wherein the piezoelectric element assembly comprises one or more pairs of ring-shaped piezoelectric elements.

8. The method of claim 1 , wherein the ultrasonic handpiece comprises additional piezoelectric assemblies, each piezoelectric assembly spaced apart along a longitudinal axis of the ultrasonic handpiece.

9. a handpiece including a piezoelectric element assembly; a controller coupled to the piezoelectric element assembly, the controller comprising: applying a control signal to drive the piezoelectric element assembly in a first vibration mode and a second vibration mode simultaneously; generating feedback of a resultant vibration of the piezoelectric element assembly in the first mode and in the second mode; Adjusting the application of the control signal based on the feedback such that the resulting vibration in the first mode and the resulting vibration in the second mode are each at approximately a respective resonant frequency. The controller and An ultrasonic handpiece system comprising:

10. 10. The ultrasonic handpiece system of claim 9, wherein the first vibration mode comprises longitudinal motion and the second vibration mode comprises torsional motion.

11. the ultrasound handpiece is configured for phacoemulsification; An ultrasonic horn; A suction tube; With hollow tip The ultrasonic handpiece system of claim 9 further comprising:

12. 10. The ultrasonic handpiece system of claim 9, wherein generating the feedback includes determining a root mean square (RMS) value of the measured voltage and resulting current in each of the first mode and the second mode.

13. The ultrasonic handpiece tool system of claim 9 , wherein generating the feedback includes determining a composite voltage and current magnitude of the resulting vibration.

14. The ultrasonic handpiece tool system of claim 9 , wherein generating the feedback includes determining a phase of a composite voltage and a composite current of the resulting vibration.

15. The ultrasonic handpiece tool system of claim 9 , wherein the piezoelectric element assembly comprises one or more pairs of ring-shaped piezoelectric elements.

16. The ultrasonic handpiece tool system of claim 11 , wherein the ultrasonic handpiece further comprises additional piezoelectric element assemblies, each piezoelectric element assembly spaced apart along a longitudinal axis of the ultrasonic handpiece.

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