ELECTROSURGICAL INSTRUMENT, GENERATOR AND APPARATUS

Abstract

Various embodiments provide an electrosurgical instrument for delivering electromagnetic (EM) energy and ultrasonic vibrations for treating biological tissue. The electrosurgical instrument comprises: an instrument shaft arranged to convey EM energy and an electrical signal for driving a magnetostrictive ultrasound transducer; a distal end assembly arranged at a distal end of the instrument shaft to receive the EM energy from the instrument shaft and deliver the EM energy from the distal end assembly for tissue treatment; and a magnetostrictive ultrasound transducer arranged to receive the electrical signal from the instrument shaft and generate ultrasonic vibrations around the distal end assembly for tissue treatment. Other embodiments provide an electrosurgical generator, and an electrosurgical apparatus comprising the instrument and generator.

Claims

1. An electrosurgical instrument for delivering electromagnetic (EM) energy and ultrasonic vibrations for treating biological tissue, the electrosurgical instrument comprising: an instrument shaft arranged to convey EM energy and an electrical signal for driving a magnetostrictive ultrasound transducer; a distal end assembly arranged at a distal end of the instrument shaft to receive the EM energy from the instrument shaft and deliver the EM energy from the distal end assembly for tissue treatment; and a magnetostrictive ultrasound transducer arranged to receive the electrical signal from the instrument shaft and generate ultrasonic vibrations around the distal end assembly for tissue treatment.

2. The electrosurgical instrument of claim 1, wherein the instrument shaft comprises a coaxial transmission line having an inner conductor, an outer conductor, and a dielectric material separating the inner conductor from the outer conductor, the coaxial transmission line being arranged to convey the EM energy and the electrical signal.

3. The electrosurgical instrument of claim 2, wherein the magnetostrictive ultrasound transducer has first and second input terminals for receiving the electrical signal from the coaxial transmission line, the first input terminal being connected to the inner conductor by a first connection means, and the second input terminal being connected to the outer conductor by a second connection means.

4. The electrosurgical instrument of claim 3, wherein the magnetostrictive ultrasound transducer is mounted on or in the distal end assembly.

5. The electrosurgical instrument of claim 4, wherein the distal end assembly is a radiating tip portion arranged to radiate an EM field for tissue treatment, the radiating tip portion comprising: a dielectric tip, a distal conductive portion of the inner conductor, which extends longitudinally into the dielectric tip, an intermediate dielectric element surrounding a proximal part of the distal conductive portion and separating the dielectric material of the coaxial transmission line from the dielectric tip, and wherein the magnetostrictive ultrasound transducer is mounted on or in the intermediate dielectric element.

6. The electrosurgical instrument of claim 4, wherein the distal end assembly comprises: a pair of jaws that are movable relative to each other to open and close a gap between opposing inner surfaces thereof, the pair of jaws comprising an energy delivery structure arranged to emit the EM energy into the gap between the opposing inner surfaces, wherein the energy delivery structure comprises a microstrip antenna mounted on the inner surface of one or both of the pair of jaws.

7. The electrosurgical instrument of claim 6, wherein the distal end assembly further comprises: a blade comprising the magnetostrictive ultrasound transducer for cutting through biological tissue, the blade being slidably disposed within the distal end assembly to be movable through the region between the pair of jaws.

8. The electrosurgical instrument of claim 6, wherein the magnetostrictive ultrasound transducer is housed in or on one of the pair of jaws.

9. The electrosurgical instrument of claim 8, wherein the microstrip antenna is a coplanar microstrip antenna comprising: a planar dielectric substrate having a top surface that is exposed at the gap between the opposing inner surfaces, and an under surface on an opposite side of the planar dielectric substrate from the top surface; a ground conductor layer on the under surface; a ground conductive strip on the top surface and electrically connected to the ground conductor layer; and an active conductive strip on the top surface, the active conductive strip being spaced from the ground conductive strip, wherein the active conductive strip and the ground conductive strip are positioned to have a uniform closest spacing within the region between the pair of jaws, and wherein the magnetostrictive ultrasound transducer is positioned on the top surface of the planar dielectric substrate and in-between the active conductive strip and the ground conductive strip.

10. The electrosurgical instrument of claim 8, wherein the pair of jaws comprises a first jaw having the energy delivery structure mounted therein, and a second jaw which does not receive an EM energy feed, and wherein the magnetostrictive ultrasound transducer is housed in or on the second jaw.

11. The electrosurgical instrument of any of claim 1, wherein the magnetostrictive ultrasound transducer is mounted on or in the instrument shaft.

12. The electrosurgical instrument of claim 1, wherein the magnetostrictive ultrasound transducer comprises a magnetostrictive element made of Terfenol-D.

13. An electrosurgical generator comprising: an electromagnetic (EM) signal supply unit for generating EM energy; an electrical signal supply unit for generating an electrical signal for driving a magnetostrictive ultrasound transducer; an output port configured to be connectable to an electrosurgical instrument for delivering the EM energy from a distal end thereof and for generating ultrasonic vibrations using the electrical signal; and a feed structure for conveying the EM energy from the EM signal supply unit to the output port, and for conveying the electrical signal from the electrical signal supply unit to the output port, wherein the feed structure has a common signal pathway for conveying the EM energy and the electrical signal to the output port wherein the electrical signal supply unit comprises: a first power supply for outputting a first supply signal and a second supply signal; a signal source for outputting a first control signal and a second control signal; a first switching circuit having a control input coupled to the signal source for receiving the first control signal, a supply input coupled to the first power supply for receiving the first supply signal, and an output, wherein the first switching circuit is operable to provide at the output at least part of the electrical signal based on the first supply signal and the first control signal; a second switching circuit having a control input coupled to the signal source for receiving the second control signal, a supply input coupled to the second power supply for receiving the second supply signal, and an output, wherein the second switching circuit is operable to provide at the output a second part of the electrical signal based on the second supply signal and the second control signal, and a common signal pathway coupled the output of the first switching circuit for receiving a first part of the electrical signal, and coupled to the output of the second switching circuit for receiving the second part of the electrical signal, and for combining the first and second parts to form the electrical signal.

14. The electrosurgical generator of claim 13 wherein the EM signal supply unit comprises a microwave signal generator for generating microwave EM radiation having a first frequency, and wherein the feed structure comprises an electrical signal channel for 5 connecting the output port to the electrical signal supply unit, and a microwave channel for connecting the output port to the microwave signal generator, the electrical signal channel and microwave channel comprising physically separate signal pathways from the electrical signal supply unit and microwave signal generator respectively, wherein the feed structure includes a first combining circuit having a first input connected to receive the electrical signal from the electrical signal channel, a second input connected to receive the microwave EM radiation from the microwave channel, and an output in communication with the first and second inputs for transferring the electrical signal and the microwave EM radiation to the common signal pathway.

15. The electrosurgical generator of claim 14, wherein the microwave channel comprises a first filter arranged to permit the passage of microwave EM radiation from the microwave signal generator to the first combining circuit, but prevent the passage of the electrical signal from the first combining circuit to the microwave signal generator.

16. The electrosurgical generator of claim 13 or H, wherein the electrical signal channel comprises a second filter arranged to permit the passage of the electrical signal from the electrical signal supply unit to the first combining circuit, but prevent the passage of the microwave EM radiation from the first combining circuit to the electrical signal supply unit.

17. The electrosurgical generator of claim 13, wherein the electromagnetic signal supply unit comprises: a radiofrequency (RF) signal generator for generating RF EM radiation having a second frequency that is lower than the first frequency, wherein the feed structure comprises an RF channel for connecting the output port to the RF signal generator, the RF channel and microwave channel comprising physically separate signal pathways from the RF signal generator and microwave signal generator respectively, wherein the feed structure includes a second combining circuit connected to the electrical signal channel and having a first input connected to receive the electrical signal from the electrical signal supply unit and a second input connected to receive the RF EM radiation from the RF channel, and an output in communication with the first and second inputs for transferring the RF EM radiation and the electrical signal to the first combining circuit.

18. The electrosurgical generator of claim 17, wherein the electrical signal channel comprises a third filter arranged to permit the passage of the electrical signal from the electrical signal supply unit to the second combining circuit, but prevent the passage of the RF EM radiation from the second combining circuit to the electrical signal supply unit.

19. The electrosurgical generator of claim 17, wherein the RF channel comprises a fourth filter arranged to permit the passage of the RF EM radiation from the RF signal generator to the second combining circuit, but prevent the passage of the electrical signal from the second combining circuit to the RF signal generator.

20. The electrosurgical generator of claim 13, wherein the first power supply comprises a filtering circuit for blocking an alternating current signal received by the first power supply at its output.

21. The electrosurgical generator of claim 13, wherein the first switching circuit comprises a current source for generating the at least part of the electrical signal from the first supply signal and in accordance with a characteristic of the first control signal.

22. The electrosurgical generator of claim 13, wherein the first switching circuit comprises a signal conditioner coupled to a switch, the signal conditioner being operable to convert the control signal into a driving signal for operating the switch.

23. An electrosurgical apparatus comprising: an electrosurgical instrument for delivering electromagnetic (EM) energy and ultrasonic vibrations for treating biological tissue, the electrosurgical instrument comprising: an instrument shaft arranged to convey EM energy and an electrical signal for driving a magnetostrictive ultrasound transducer; a distal end assembly arranged at a distal end of the instrument shaft to receive the EM energy from the instrument shaft and deliver the EM energy from the distal end assembly for tissue treatment and a magnetostrictive ultrasound transducer arranged to receive the electrical signal from the instrument shaft and generate ultrasonic vibrations around the distal end assembly for tissue treatment, and an electrosurgical generator comprising: an electromagnetic (EM) signal supply unit for generating EM energy; an electrical signal supply unit for generating an electrical signal for driving a magnetostrictive ultrasound transducer; an output port configured to be connectable to an electrosurgical instrument for delivering the EM energy from a distal end thereof and for generating ultrasonic vibrations using the electrical signal; a feed structure for conveying the EM energy from the EM signal supply unit to the output port, and for conveying the electrical signal from the electrical signal supply unit to the output port, wherein the feed structure has a common signal pathway for conveying the EM energy and the electrical signal to the output port wherein the electrical signal supply unit comprises: a first power supply for outputting a first supply signal and a second supply signal; a signal source for outputting a first control signal and a second control signal; a first switching circuit having a control input coupled to the signal source for receiving the first control signal, a supply input coupled to the first power supply for receiving the first supply signal, and an output, wherein the first switching circuit is operable to provide at the output at least part of the electrical signal based on the first supply signal and the first control signal; a second switching circuit having a control input coupled to the signal source for receiving the second control signal, a supply input coupled to the second power supply for receiving the second supply signal, and an output, wherein the second switching circuit is operable to provide at the output a second part of the electrical signal based on the second supply signal and the second control signal, and a common signal pathway coupled the output of the first switching circuit for receiving a first part of the electrical signal, and coupled to the output of the second switching circuit for receiving the second part of the electrical signal, and for combining the first and second parts to form the electrical signal, wherein the output of the electrosurgical generator is configured to be connectable to a proximal end of the instrument shaft of the electrosurgical instrument.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0089] Examples of the invention are described in more detail below with reference to the accompanying drawings, in which:

[0090] FIG. 1 is a schematic diagram of an electrosurgical generator in accordance with an embodiment;

[0091] FIG. 2 is a schematic diagram of an electrical signal supply unit of the electrosurgical generator of FIG. 1, in accordance with an embodiment;

[0092] FIG. 3 is a schematic diagram of an electrical signal supply unit of the electrosurgical generator of FIG. 1, in accordance with another embodiment;

[0093] FIG. 4 is a schematic diagram of an electrical signal supply unit of the electrosurgical generator of FIG. 1, in accordance with a further embodiment;

[0094] FIG. 5 is a schematic diagram of a feed structure of the electrosurgical generator of FIG. 1, in accordance with an embodiment;

[0095] FIG. 6A is a schematic diagram of a magnetostrictive ultrasound transducer in accordance with an embodiment;

[0096] FIG. 6B is a diagram of a magnetic hysteresis loop;

[0097] FIG. 7 is a schematic diagram of an electrosurgical apparatus, in accordance with an embodiment;

[0098] FIG. 8 is a schematic cross section view of an electrosurgical instrument, in accordance with an embodiment;

[0099] FIG. 9 is a schematic perspective view of an electrosurgical instrument, in an open configuration, in accordance with another embodiment;

[0100] FIG. 10 is a schematic perspective view of an underside of the electrosurgical instrument of FIG. 9;

[0101] FIG. 11 is a schematic perspective view of the electrosurgical instrument of FIG. 9, in a closed configuration;

[0102] FIG. 12A and 12B show opposing surfaces of an example coplanar microstrip antenna that can be used in the electrosurgical instrument of FIG. 9; and,

[0103] FIG. 13 shows a top surface of a coplanar microstrip antenna comprising multiple magnetostrictive ultrasound transducers, an accordance with an embodiment.

DETAILED DESCRIPTION; FURTHER OPTIONS AND PREFERENCES

[0104] FIG. 1 shows a schematic diagram of an electrosurgical apparatus 400. The apparatus comprises a RF channel, a microwave channel, and an electrical signal channel for conveying an electrical (e.g. current) signal for driving a magnetostrictive ultrasound transducer to generate ultrasonic vibrations. The RF channel contains components for generating and controlling an RF frequency electromagnetic signal at a power level suitable for treating (e.g. cutting or desiccating) biological tissue. The microwave channel contains components for generating and controlling a microwave frequency electromagnetic signal at a power level suitable for treating (e.g. coagulating or ablating) biological tissue. The electrical signal channel contains components for generating and controlling an electrical (e.g. current) signal for driving a magnetostrictive ultrasound transducer for forming ultrasound vibrations at a power level suitable for tissue treatment (e.g. dissecting, cutting, dividing).

[0105] The microwave channel has a microwave frequency source 402 followed by a power splitter 424 (e.g. a 3 dB power splitter), which divides the signal from the source 402 into two branches. One branch from the power splitter 424 forms a microwave channel, which has a power control module comprising a variable attenuator 404 controlled by controller 406 via control signal V.sub.10 and a signal modulator 408 controlled by controller 406 via control signal V.sub.11, and an amplifier module comprising drive amplifier 410 and power amplifier 412 for generating forward microwave EM radiation for delivery from an instrument (e.g. probe or pair of jaws) 420 at a power level suitable for treatment. After the amplifier module, the microwave channel continues with a microwave signal coupling module (which forms part of a microwave signal detector) comprising a circulator 416 connected to deliver microwave EM energy from the source to the instrument along a path between its first and second ports, a forward coupler 414 at the first port of the circulator 416, and a reflected coupler 418 at the third port of the circulator 416. After passing through the reflected coupler, the microwave EM energy from the third port is absorbed in a power dump load 422. The microwave signal coupling module also includes a switch 415 operated by the controller 406 via control signal V.sub.12 for connecting either the forward coupled signal or the reflected coupled signal to a heterodyne receiver for detection.

[0106] The other branch from the power splitter 424 forms a measurement channel. The measurement channel bypasses the amplifying line-up on the microwave channel, and hence is arranged to deliver a low power signal from the instrument. A primary channel selection switch 426 controlled by the controller 406 via control signal V.sub.13 is operable to select a signal from either the microwave channel or the measurement channel to deliver to the instrument. A high band pass filter 427 is connected between the primary channel selection switch 426 and the probe 420 to protect the microwave signal generator from low frequency RF signals and/or ultrasound frequency signals (produced by electrical signal supply unit 490). The high pass filter 427 is part of a feed structure which is described in more detail below with reference to FIG. 5.

[0107] The measurement channel includes components arranged to detect the phase and magnitude of power reflected from the instrument, which may yield information about the material e.g. biological tissue present at the distal end of the instrument. The measurement channel comprises a circulator 428 connected to deliver microwave EM energy from the source 402 to the probe along a path between its first and second ports. A reflected signal returned from the instrument is directed into the third port of the circulator 428. The circulator 428 is used to provide isolation between the forward signal and the reflected signal to facilitate accurate measurement. However, as the circulator does not provide complete isolation between its first and third ports, i.e. some of the forward signal may break through to the third port and interfere with the reflected signal, a carrier cancellation circuit may be used that injects a portion of the forward signal (from forward coupler 430) back into the signal coming out of the third port (via injection coupler 432). The carrier cancellation circuit include a phase adjustor 434 to ensure that the injected portion is 180° out of phase with any signal that breaks through into the third port from the first port in order to cancel it out. The carrier cancellation circuit also include a signal attenuator 436 to ensure that the magnitude of the injected portion is the same as any breakthrough signal.

[0108] To compensate for any drift in the forward signal, a forward coupler 438 is provided on the measurement channel. The coupled output of the forward coupler 438 and the reflected signal from the third port of the circulator 428 are connected to respective input terminal of a switch 440, which is operated by the controller 406 via control signal V.sub.14 to connect either the coupled forward signal or the reflected signal to a heterodyne receiver for detection. The output of the switch 440 (i.e. the output from the measurement channel) and the output of the switch 415 (i.e. the output from the microwave channel) are connect to a respective input terminal of a secondary channel selection switch 442, which is operable by the controller 406 via control signal V.sub.15 in conjunction with the primary channel selection switch to ensure that the output of the measurement channel is connected to the heterodyne receiver when the measurement channel is supplying energy to the instrument and that the output of the microwave channel is connected to the heterodyne receiver when the microwave channel is supplying energy to the instrument.

[0109] The heterodyne receiver is used to extract the phase and magnitude information from the signal output by the secondary channel selection switch 442. A single heterodyne receiver is shown in this system, but a double heterodyne receiver (containing two local oscillators and mixers) to mix the source frequency down twice before the signal enters the controller may be used if necessary. The heterodyne receiver comprises a local oscillator 444 and a mixer 448 for mixing down the signal output by the secondary channel selection switch 442. The frequency of the local oscillator signal is selected so that the output from the mixer 448 is at an intermediate frequency suitable to be received in the controller 406. Band pass filters 446, 450 are provided to protect the local oscillator 444 and the controller 406 from the high frequency microwave signals.

[0110] The controller 406 receives the output of the heterodyne receiver and determines (e.g. extracts) from it information indicative of phase and magnitude of the forward and/or reflected signals on the microwave or measurement channel. This information can be used to control the delivery of high power microwave EM radiation on the microwave channel or high power RF EM radiation on the RF channel. A user may interact with the controller 406 via a user interface 452, as discussed above.

[0111] The RF channel shown in FIG. 1 comprises an RF frequency source 454 connected to a gate driver 456 that is controlled by the controller 406 via control signal V.sub.16. The gate driver 456 supplies an operation signal for an RF amplifier 458, which is a half-bridge arrangement. The drain voltage of the half-bridge arrangement is controllable via a variable DC supply 460. An output transformer 462 transfers the generated RF signal on to a line for delivery to the instrument 420. A high pass filter 464 is connected on that line to protect the RF signal generator from ultrasound frequency signals produced by electrical signal supply unit 490. The filter 464 also forms part of the feed structure, which is described below with reference to FIG. 5.

[0112] A current transformer 466 is connected on the RF channel to measure the current delivered to the tissue load. A potential divider 468 (which may be tapped off the output transformer) is used to measure the voltage. The output signals from the potential divider 468 and current transformer 466 (i.e. voltage outputs indicative of voltage and current) are connected directly to the controller 406 after conditioning by respective buffer amplifiers 470, 472 and voltage clamping Zener diodes 474, 476, 478, 480 (shown as signals B and C in FIG. 1).

[0113] To derive phase information, the voltage and current signals (B and C) are also connected to a phase comparator 482 (e.g. an EXOR gate) whose output voltage is integrated by RC circuit 484 to produce a voltage output (shown as A in FIG. 1) that is proportional to the phase difference between the voltage and current waveforms. This voltage output (signal A) is connected directly to the controller 406.

[0114] The electrical signal channel is provided in part by the electrical signal supply unit 490, an embodiment of which is shown in more detail in FIG. 2. The electrical signal supply unit 490 includes a signal source 500 for generating one or more control signals (e.g. voltage signals). In an embodiment, the signal source 500 is a microcontroller (e.g. an Arduino™ microcontroller), a Colpitts oscillator, a Hartley oscillator or a 555 timer. The signal source 500 generates control signals in the form of low power oscillating (or alternating) signals (e.g. pulsed, square, sinusoidal, ramp, trapezoidal, exponential) which drive the remaining parts of the electrical signal supply unit to form an electrical (e.g. current) signal having an ultrasound frequency for driving a magnetostrictive ultrasound transducer (e.g. on the instrument 420) so as to generate ultrasound vibrations for treating biological tissue. Specifically, the signal source 500 generates two control signals, a first (e.g. positive) control signal which is provided to a control input of a first switching circuit 502, and a second (e.g. negative) control signal which is provided to a control input of a second switching circuit 504. Example diagrammatic representations of the first and second control signals are shown in FIG. 2, wherein the first control signal is a positive square wave, and the second control signal is a negative square wave that is 180° or it out of phase with the first control signal. The control signals are shown as voltage signals in FIG. 2 because the first and second switching circuits 502 and 504 include voltage controlled current sources, as is described in more detail below. However, it is to be understood that the control signals could be oscillating low power current signals if, for example, the first and second switching circuits 502, 504 include current controlled current sources.

[0115] In an embodiment, the first control signal oscillates at an ultrasound frequency between 0 V and 5 V and with minimal current (e.g. <1 mA), and the second control signal oscillates at an ultrasound frequency (e.g. the same ultrasound frequency as the first control signal) between 0 V and −5 V and with minimal current (e.g. <1 mA). The first switching circuit 502 has a supply input coupled to a first power supply 506. Also, the second switching circuit 502 has a supply input coupled to a second power supply 508. In an embodiment, the first and second power supply units may be DC power supply units. The first switching circuit 502 provides a first part of an output electrical (e.g. current) signal of the electrical signal supply unit 490. Specifically, the first switching circuit 502 comprises a current source (e.g. a MOSFET, BJT, or IGFET) and uses the first supply signal received from the first power supply 506 to generate an oscillating current signal based on the oscillations of the first control signal. This is diagrammatically shown in FIG. 2 by the positive square wave which oscillates between a current +i Amps and 0 Amps (+i Amps may be 100 A in an embodiment). Also, the second switching circuit 504 provides a second or remaining part of the output electric current signal of the electrical signal supply unit 490. Specifically, the second switching circuit 504 comprises a current source (e.g. a MOSFET, BJT, or IGFET) and uses the second supply signal received from the second power supply 508 to generate an oscillating current signal based on the oscillations of the second control signal. This is diagrammatically shown in FIG. 2 by the negative square wave which oscillates between a current −i Amps and 0 Amps (−i Amps may be −100 Amps in an embodiment).

[0116] As seen on FIG. 2, the output (i.e. the first part of the electrical signal) from the first switching circuit 502 and the output (i.e. the second part of the electrical signal) from the second switching circuit 504 are combined together on a common signal path to form a combined output electrical (e.g. current) signal from the electrical signal supply unit 490. Therefore, the output from the electrical signal supply unit 490 is an electrical signal which varies at the same ultrasound frequency as the signal source 500 and between the maximum current values provided by the first and second switching circuits (i.e. between +i and −i). That is, the electrical (e.g. current) signal output from the electrical signal supply unit 490 is a compound signal made up from two portions: a first (e.g. positive) portion provided by the signal source 500, the first power supply 506 and the first switching circuit 502; and, a second (e.g. negative) portion provided by the signal source 500, the second power supply 508 and the second switching circuit 504. It is to be understood that the positive portion will cause a positive H-field in the magnetostrictive ultrasound transducer and so cause a change in dimension in one direction, whereas the negative portion will cause a negative H-field in the transducer and so cause a change in dimension in a second (e.g. opposite) direction.

[0117] An advantage of having two power supplies 506, 508 and two switching circuits 502, 504 which provide the first and second parts of the output electrical (e.g. current) signal is that the waveform of the output electrical signal can be adapted to improve performance of the ultrasound transducer. For example, the first and second control signals can be adapted to introduce a delay between the two parts of the output electrical signal in order to provide time for the transducer (e.g. its coil and/or its magnetostrictive element) to cool after being driven in one direction and before being driven in the opposite direction. In turn, this may increase the useable lifespan of the transducer and/or reduce the chances of it breaking or malfunctioning. In an embodiment, the operation of the signal source may be controlled by the controller 406, for example, via a dedicated control signal received therefrom.

[0118] Returning to FIG. 1, a transformer 492 is coupled at one side to the electrical signal supply unit 490 and at the other side to a low pass filter 494. The transformer 492 functions to isolate the instrument 420 (and a patient) from the electric supply unit 490. In an embodiment, the transformer 492 may be an opto-isolator. Also, the transformer 492 may be absent in some embodiments. In any case, the low pass filter 464 is connected to the RF channel by signal combiner 496, and the low pass filter 494 operates to protect the electrical signal supply unit from RF signals generated on the RF channel. The filter 494 and the signal combiner 496 also form part of the feed structure, which is described below with reference to FIG. 5.

[0119] The microwave/measurement channel is connected to a signal combiner 417. Also, the signal combiner 417 is connected to the signal combiner 496 via a low pass filter 498, which functions to protect both the RF channel and the electrical signal channel from microwave energy. Further, the microwave, RF and electrical signal are conveyed separately or simultaneously along cable assembly 419 to the instrument 420. The instrument 420 delivers (e.g. radiates) microwave and/or RF energy into the biological tissue of a patient. Also, the instrument 420 includes a magnetostrictive ultrasound transducer, and the electrical signal drives the transducer to generate ultrasonic vibrations for tissue treatment.

[0120] It is to be understood that in some embodiments, only one of the microwave and RF channels may be present and so the instrument may deliver only one of RF and microwave energy. Also, the measurement channel may be absent in some embodiments.

[0121] FIG. 3 shows a more detailed embodiment of the electrical signal supply unit 600. The electrical signal supply unit 600 is analogous to the electrical signal supply unit 490 of FIG. 2, wherein like reference numerals relate to like components. As is clear from FIG. 3, the electrical signal supply unit 600 includes the signal source 500. However, in FIG. 3, the first switching circuit 502 of FIG. 2 is constructed from a first gate driver 602 and a first switch 604 comprising a current source. Additionally, the second switching circuit 504 of FIG. 2 is constructed from a second gate driver 606 and a second switch 608 comprising a current source. In an embodiment, the first and second switches 604, 608 are MOSFETs (i.e. voltage controlled current sources), for example, switch 604 may be a P-channel MOSFET and switch 608 may be an N-channel MOSFET. Also, the gate drivers 602, 606 function to condition the control signals received from the signal source 500 into suitable signals for driving the switches 604, 608, respectively. For example, as mentioned previously, the first control signal is a low power oscillating positive signal which oscillates at an ultrasound frequency between, for example, 0 V and 5 V and with minimal current (e.g. <1 mA). Also, the second control signal is a low power oscillating negative signal which oscillates at an ultrasound frequency (e.g. the same ultrasound frequency as the first control signal) between, for example, 0 V and −5 V and with minimal current (e.g. <1 mA). However, switches 604 and 608 (e.g. MOSFETs) may require a higher voltage and current in order to operate and, therefore, the gate drivers 602 and 606 condition the control signals by increasing their voltage and/or current such that the conditioned signals can drive the switches 604, 608. For example, larger signals may be required in order to charge-up inherent capacitances of the MOSFETs. In an embodiment, the gate driver 602 may condition the first control signal into an oscillating signal which oscillates between 0 V and 15 V and with a current of 1 A. Also, the gate driver 606 may condition the second control signal into an oscillating signal which oscillates between 0 V and −15 V and with a current of 1 A. The gate drivers 602, 606 may be referred to as signal conditioners.

[0122] Also, in FIG. 3, the first power supply 506 of FIG. 2 includes a capacitive circuit C1, C2 which performs two functions. Also, the second power supply 508 of FIG. 2 includes a capacitive circuit C3, C4 which performs the same two functions. Firstly, the capacitive circuits (C1, C2 and C3, C4) provide power supply decoupling that prevents alternating current (AC) or spikes from entering the output of the DC power supplies, i.e. it takes such AC currents or spikes to ground. This reduces the chances that the DC power supply will be damaged by such AC currents or spikes. Secondly, the capacitive circuits (C1, C2 and C3, C4) cause the output electrical signal from the electrical signal supply unit 600 to be provided from the capacitive circuits rather than directly from the power supplies. In turn, this increases the current available for generating the output electrical (e.g. current) signal. In an embodiment, capacitors C1 and C3 may each have a value of 100 μF, whereas capacitors C2 and C4 may each have a value of 0.1 μF.

[0123] FIG. 4 shows an alternative embodiment of the electrical signal supply unit 700. Specifically, comparing the electrical signal supply unit 700 with the electrical signal supply unit 490 of FIG. 2, it is clear that the unit 700 includes a signal source 702 which generates a single control signal for a single switching circuit 704. Also the switching circuit 704 receives a supply signal from a single power supply 706. As such, the output electrical (e.g. current) signal provided by the electrical signal supply unit is either positive (e.g. between 0 and +i) or negative (e.g. between 0 and −i). This is in contrast to the arrangement of FIG. 2 in which the output electrical (e.g. current) signal is a compound signal constructed from a two parts (e.g. a positive part and a negative part). Whilst the arrangement of FIG. 4 is simpler and cheaper to manufacture, it can provide a smaller magnitude range compared to the arrangement of FIG. 2, since it tends to generate either a positive or a negative signal. Additionally, since the output electrical signal is not a combination of two control signals, it is not possible to use the control signals to introduce a delay between the positive and negative portions of the output electrical signal. A further embodiment of the electrical signal supply unit maybe formed as a variant of the electrical signal supply unit of FIG. 3, wherein a single gate driver may receive a single control signal from the signal source 500, and the single gate driver may condition that single control signal to drive both the switch 604 and the switch 608. In this way, advantageously, the output electrical signal may have the wider current range of the arrangement of FIG. 2 (e.g. +i to −i). However, as with the arrangement of FIG. 4, this variant would be unable to introduce a delay between the positive and negative portions of the output electrical signal. That is, the conditioned control signal from the single gate driver must switch the switch 604 ON at the same time as switching the switch 608 OFF (and vice versa).

[0124] FIG. 5 shows a schematic view of a feed structure of the generator in accordance with the embodiment of FIG. 1. The feed structure receives as inputs a microwave EM signal from the microwave channel, an electrical signal for driving the ultrasound transducer from the electrical signal channel, and an RF EM signal from the RF channel. The feed structure provides as an output one or more of the three input signals (separately or simultaneously) for onward transmission to the instrument 420 via the feed line 419. The feed structure includes one or more signal combiners and one or more filters in order to combine together these different signals in such a way as to avoid damage to the separate but interconnected mechanisms for generating these different signals. Specifically, the feed structure includes a first signal combiner 417 which combines the microwave channel and the electrical signal channel into a common signal path. Additionally, the feed structure includes a second signal combiner 496 for combining the RF channel with the electrical signal channel. The RF EM signal and the electrical signal may cause damage to the mechanisms for generating the microwave EM signal and, therefore, positioned in the microwave channel and before the signal combiner 417 is the high-pass filter 427 with a relatively high cut-off frequency (e.g. about 300 MHz). This high pass filer 427 passes microwave EM frequency energy, but blocks the lower frequencies of the electrical signal (which has an ultrasound frequency) and the RF signal. For example, a 1 pF capacitor may be used as the filter 427.

[0125] Additionally, the microwave EM signal may cause damage to the mechanisms for generating the electrical signal and the RF EM signal and, therefore, positioned in-between the first and second signal combiners 417, 496 is the low-pass filter 498 with a relatively high cut-off frequency (e.g. about 300 MHz) such that it passes the electrical signal that has an ultrasound frequency and the RF EM signal, but blocks the higher frequency microwave energy. For example, one or more (e.g. three) microwave stubs may be used, wherein the stubs are arranged to filter out a signal having the same frequency as the microwave energy. The stubs may be as disclosed in WO2017103209A1.

[0126] Additionally, the RF EM signal may cause damage to the mechanisms for generating the electrical signal and, therefore, positioned in the electrical signal channel and before the signal combiner 496 is the low-pass filter 494 which has a relatively low cut-off frequency (e.g. about 100 KHz) such that it passes the electrical signal having an ultrasound frequency, but blocks RF signals. For example, an inductor may be used. Also, the electrical signal may cause damage to the mechanisms for generating the RF EM signal and, therefore, positioned in the RF channel and before the signal combiner 496 is the high-pass filter 464 with a relatively low cut-off frequency (e.g. about 100 kHz) such that it passes RF frequency energy but blocks the lower ultrasound frequency of the electrical signal. For example, a 1 μF capacitor may be used as the filter 464.

[0127] As such, the feed structure conveys EM energy (e.g. microwave and/or RF) from respective EM energy supply units and conveys the electrical signal from the electrical signal supply unit. Also, the feed structure includes a common signal pathway for conveying the EM energy and the electrical signal to the output port for onward transmission to the instrument 420. Moreover, the feed structure includes a circuit or network of signal combiners and filters which function to ensure that these separate and different input signals do not damage the various separate and different mechanisms for producing those signals.

[0128] FIG. 6A illustrates a magnetostrictive ultrasound transducer in accordance with an embodiment. The transducer includes a housing 802 within which is located a coiled conductor 804 which is wrapped around an element 806 of magnetostrictive material. The element 806 may be substantially elongate or rod shaped, and may be referred to as a solenoid. In an embodiment, the element 806 may be approximately the same length as the coil, or just longer than the coil, for example, 1 cm or 1.2 cm. Also, the element 806 may be substantially cylindrical and have a diameter of about 0.5 cm or 0.6 cm. The coiled conductor 804 is connected at a first end to a first terminal 808 of the transducer 800, and at a second end to a second terminal 810 of the transducer 800. In use, the first terminal 808 and the second terminal 810 are connected to the cable assembly 419 of FIG. 1 in order that the electrical signal is provided to the transducer 800 so that the transducer 800 generates ultrasonic vibrations. Specifically, magnetostriction is a property of ferromagnetic materials which causes them to expand or contract (i.e. change their physical dimensions) in response to a magnetic field (H-field). This effect allows magnetostrictive materials to convert electromagnetic energy into mechanical energy. As a magnetic field is applied to the material, its molecular dipoles and magnetic field boundaries rotate to align with the field. This causes the material to strain and elongate.

[0129] FIG. 6B shows an example magnetic hysteresis loop. A magnetic hysteresis loop is produced when a ferromagnetic material is magnetised in one direction, until it reaches a saturation point (e.g. point 824 on FIG. 6B), then the magnetic field strength is demagnetised in the opposite direction to the reverse saturation point (e.g. point 826 on FIG. 6B). When the magnetic field direction is alternated, a loop is formed which goes back and forth from the saturation point and reverse saturation point. This loop can be viewed in FIG. 6B. The magnetising field (H) provides the required stress to produce the required change in magnetisation (M or B) or the strain. The magnetisation (M) of the ferromagnetic material when the magnetic field strength (H) is at zero is called remanence. As the magnetisation falls back to zero, the magnetic field strength (H) needed to demagnetise after saturation is called the coercivity. The point marked 820 can be referred to as the remanence point and is a measure of the remaining magnetisation when the driving field is dropped to zero. This illustrates that when the driving magnetic field drops to zero, the ferromagnetic material retains a considerable degree of magnetisation. The point marked 822 can be referred to as the coercivity point and is a measure of the reverse field needed to drive the magnetisation to zero after being saturated. This illustrates that the driving magnetic field must be reversed and then increased to drive the magnetisation to zero again. Point 824 indicates a point at which the ferromagnetic material is magnetised to saturation by alignment of magnetic domains in one direction (e.g. north pole), whereas the point 826 indicates a point at which the ferromagnetic material is magnetised to saturation by alignment of magnetic domains in the opposite direction (e.g. south pole). A width 828 of the hysteresis loop indicates if a material retains a large or small fraction of the saturation field when the driving field is removed. The width may vary between different magnetostrictive materials. A narrow hysteresis loop implies that a small amount of dissipated energy is repeatedly reversing the magnetisation. Embodiments are directed to the use of magnetostrictive materials in the production of ultrasound vibrations. Given the relatively high frequency of ultrasound vibrations, the switching between saturation points must occur relatively quickly, e.g. between 20,000 and 5,000,000 times per second (i.e. 20 kHz to 5 MHz). Therefore, an aim is to keep the hysteresis loop as narrow as possible (i.e. to keep width 828 as low as possible) so that the change (or switch) of the magnetisation occurs at a much faster rate and so that energy dissipation and subsequent heating remains small.

[0130] Terfenol-D has been selected as a particularly suitable magnetostrictive material from which to make the element 806. Terfenol-D is a good material to use because it possesses a large magnetisation and magnetostriction at room temperature, which is about 2400 ppm, which occurs due to rhombohedral distortion of the lattice structure of the Terfenol-D material. That is, Terfenol-D, relative to other magnetostrictive materials, produces a large strain (i.e. change in physical dimension) for a given stress (i.e. applies change in magnetic driving field). For example, Galfenol has a magnetostriction of about 400 ppm and Alfenol has a magnetostriction of about 200 ppm. However, since Terfenol-D is a relatively expensive material, the element 806 may be constructed from two portions: a first portion that is substantially the same length as the coil and is made from Terfenol-D, and a second portion that is an extension of the first portion and is made from a cheaper material, such as, steel.

[0131] The following provides some example calculations to determine a possible structure of the coil 804 and element 806, in accordance with an embodiment. It is known that the magnetic field strength (H) can be found from equation (1) below:

[00001]$\begin{array}{cc}H=\frac{\mathrm{NI}}{L}& \left(1\right)\end{array}$

[0132] where N refers to the number of turns of wire on the coil 804, I is the current of the electrical signal used to drive the transducer 800, and L is the length of the coil 804 (labelled “L” in FIG. 6A).

[0133] In an embodiment, it may be considered that a magnetic field strength of 2000 Oersted (Oe) will produce a maximum strain of 2400 ppm for a certain Terfenol-D magnetostrictive element 806. If 1 Oe is equivalent to 79.58 A/m, then 2000 Oe is equivalent to 159,155 A/m.

[0134] From equation (1), if a current of 100 A is driven into the coil 804, then N/L=1,592. N/L is the ratio of the number of turns of wire on the coil 804 divided by the length (L) of the coil 804. If the length of the coil is 1 cm (0.01 m), then the number of turns required will be: (N=H*L)/I=(159155*0.01)/100=15.9 turns—i.e. about 16 turns.

[0135] In an embodiment, the coil is made from copper wire with an outer diameter of 0.5 mm, and so it is possible to get 20 turns within a 1 cm length and a single layer winding. Additionally, it is possible to have multi-layer windings. However, it should be noted that the number of turns in an opposite direction should be minimised in order to avoid having a cancelling-out effect. For example, a double layer winding for providing 20 turns could include 11 turns in a first direction (layer 1), a single return turn (which would cancel out one of the original turns—i.e. the 11 turns reduces to 10 turns) (layer 2), followed by 10 more turns in the first direction (layer 3). Using multi-layer windings in this manner makes it possible to reduce the coil length required and, therefore, reduce the overall size of the transducer 800. For example, the coil length could be reduced to 0.5 cm or less. Another mechanism for reducing the coil length required and, therefore, reduce the overall size of the transducer 800, is to increase the current of the driving electrical signal applied to the input terminals, 808, 810 of the transducer 800. For example, considering the arrangement of FIG. 3, this could be done by increasing the size of the power supplies (e.g. +V.sub.DD, 31 V.sub.DD) and the size of the current sources (e.g. MOSFETs).

[0136] FIG. 7 is a schematic diagram of a complete electrosurgery system (or apparatus) 100 that is capable of supplying RF energy, microwave energy, or an electrical signal for driving a magnetostrictive ultrasound transducer to generate ultrasound vibrations. The system 100 comprises a generator 102 for controllably supplying RF energy, microwave energy, and the electrical signal suitable for driving a magnetostrictive ultrasound transducer to generate ultrasound vibrations. In an embodiment, the generator 102 is the same as generator 400 described above with reference to FIGS. 1 to 5.

[0137] The generator 102 is connected to an interface joint 106 by an interface cable 104. If needed, the interface joint 106 can house an instrument control mechanism that is operable by sliding a trigger 110, e.g. to control longitudinal (back and forth) movement of one or more control wires or push rods (not shown). If there is a plurality of control wires, there may be multiple sliding triggers on the interface joint to provide full control. The function of the interface joint 106 is to combine the inputs from the generator 102 and instrument control mechanism into a single flexible shaft 112, which extends from the distal end of the interface joint 106.

[0138] The flexible shaft 112 is insertable through the entire length of an instrument (working) channel of a surgical scoping device 114, such as an endoscope, laparoscope, bronchoscope, gastroscope or the like.

[0139] The surgical scoping device 114 comprises a body 116 having a number of input ports and an output port from which an instrument cord 120 extends. The instrument cord 120 comprises an outer jacket which surrounds a plurality of lumens. The plurality of lumens convey various things from the body 116 to a distal end of the instrument cord 120. One of the plurality of lumens is an instrument channel. Other lumens may include a channel for conveying optical radiation, e.g. to provide illumination at the distal end or to gather images from the distal end. The body 116 may include an eye piece 122 for viewing the distal end. In order to provide illumination at the distal end, a light source 124 (e.g. LED or the like) may be connected to the body 116 by an illumination input port 126.

[0140] The flexible shaft 112 has a distal assembly 118 (not drawn to scale in FIG. 7) that is shaped to pass through the instrument channel of the surgical scoping device 114 and protrude (e.g. inside the patient) at the distal end thereof. The distal end assembly includes an active tip for delivering microwave energy into biological tissue as discussed herein. The distal assembly 118 may be analogous to the instrument 420 of FIG. 1, and the flexible shaft 112 may be analogous to the feed line 419 of FIG. 1.

[0141] The structure of the distal assembly 118 discussed below may be designed to have a maximum outer diameter equal to or less than 2.0 mm, e.g. less than 1.9 mm (and more preferably less than 1.5 mm) and the length of the flexible shaft can be equal to or greater than 1.2 m.

[0142] The body 116 includes a power input port 128 for connecting to the flexible shaft, which comprises a coaxial cable (e.g. a conventional coaxial cable) capable of conveying the microwave energy, RF energy and an electrical signal from the generator 102 to the distal assembly 118. Alternatively, different means may be provided to conveying one or more of these signals. For instance, the microwave energy may be conveyed by the coaxial cable, but the electrical signal and/or the RF energy may be conveyed by a twisted cable pair or the like. Coaxial cables that are physically capable of fitting down the instrument channel of a surgical scoping device are available with the following outer diameters: 1.19 mm (0.047″), 1.35 mm (0.053″), 1.40 mm (0.055″), 1.60 mm (0.063″), 1.78 mm (0.070″). Custom-sized coaxial cables (i.e. made to order) may also be used.

[0143] As discussed above, it is desirable to be able to control the position of at least the distal end of the instrument cord 120. The body 116 may include a control actuator 130 that is mechanically coupled to the distal end of the instrument cord 120 by one or more control wires (not shown), which extend through the instrument cord 120. The control wires may travel within the instrument channel or within their own dedicated channels. The control actuator 130 may be a lever or rotatable knob, or any other known catheter manipulation device. The manipulation of the instrument cord 120 may be software-assisted, e.g. using a virtual three-dimensional map assembled from computer tomography (CT) images.

[0144] The coaxial cable for delivering the microwave radiation to the target site should be low-loss, have a small cross-section and be flexible. The cable should be low loss to avoid or reduce heating during treatment and so that there is enough power at the distal end to produce the desired radiation from the antenna.

[0145] If the cable is not separated from the body by the use of a sealed scoping device, catheter or other protective sheath, then the cable should be made of, or be coated with, a biologically inert material to avoid unwanted interaction with the body.

[0146] A preferred cable type is a coaxial cable which is made up of an inner conductor axially surrounded by a dielectric sheath which is in turn axially surrounded by an outer conductor. The radiating portion in an antenna produced from such a cable may be made up of a section of inner conductor and dielectric sheath which protrudes from the end of the outer conductor of the coaxial cable.

[0147] In an embodiment, the outer conductor of the coaxial cable may be as physically thick as possible to increase its thermal mass and heat capacity. In this way, all or a majority of the heat generated in the cable due to conveying microwave energy can be held within the structure of the cable rather than, for example, being leaked inside the patient. In an embodiment, the outer conductor may be 0.5 mm thick.

[0148] The invention also seeks to provide an antenna with a well-defined radiation pattern. It is desirable that a practitioner would be able to select an instrument for the treatment of a specific area of tissue, such that the radiation of target tissue is maximised and the radiation of healthy tissue is minimised. For example, in some circumstances it can be desirable to produce a generally spherically symmetric radiation pattern with a substantially uniform power absorption distribution, so that the amount of radiation received by an area of tissue can be more easily controlled by the practitioner.

[0149] It is also preferable that the instrument can be operated alongside other instruments to enable practitioners to receive information from the target site. For example, a scoping device may aid the steering of the instruments around obstacles within a patient's body. Other instruments may include a thermometer or camera.

[0150] In the following description, unless stated otherwise, the length of a component refers to its dimension in the direction parallel to the longitudinal axis of the coaxial cable.

[0151] FIG. 8 is a cross-sectional view of the distal end of an electrosurgical instrument 200 that is an embodiment of the invention. The electrosurgical instrument 200 may include the distal assembly 118 of FIG. 7, or the instrument 420 of FIG. 1. The electrosurgical instrument 200 may therefore be used to deliver microwave energy and/or RF energy into biological tissue for tissue treatment. Also, the instrument 200 includes a magnetostrictive ultrasound transducer for converting an electrical (e.g. current) signal into ultrasonic vibrations in biological tissue for tissue treatment. The electrosurgical instrument 200 comprises a coaxial cable 202 that is connected at its proximal end to an electrosurgical generator (e.g. generator 400 of FIG. 1 or generator 102 of FIG. 7) in order to convey microwave energy. The coaxial cable 202 comprises an inner conductor 206, which is separated from an outer conductor 208 by a first dielectric material 210. The coaxial cable 202 is preferably low loss for microwave energy. A choke (not shown) may be provided on the coaxial cable to inhibit back propagation of microwave energy reflected from the distal end and therefore limit backward heating along the device.

[0152] The device may include a temperature sensor at the distal end. For example, in FIG. 8 a thermocouple 230 is mounted on the outer conductor to transmit a signal back to the proximal end that is indicative of temperature at the distal end of the instrument.

[0153] Other techniques for temperature monitoring can be used. For example, one or more micromechanical structures whose physical configuration is sensitive to temperature may be mounted in the distal portion of the device, e.g. in or on the outer sheath discussed below. These structures can be interfaced with an optical fibre, whereby changes in a reflected signal caused by movement of the structure can be indicative of temperature changes.

[0154] The coaxial cable 202 terminates at its distal end with a radiating tip section 204. In this embodiment, the radiating tip section 204 comprises a distal conductive section 212 of the inner conductor 206 that extends beyond a distal end 209 of the outer conductor 208. The distal conductive section 212 is surrounded at its distal end by a dielectric tip 214 formed from a second dielectric material, which is different from the first dielectric material 210. The length of the dielectric tip 214 is shorter than the length of the distal conductive section 212. An intermediate dielectric sleeve 216 surrounds the distal conductive section 212 between the distal end of the coaxial cable 202 and the proximal end of the dielectric tip 214. The intermediate dielectric sleeve 216 is formed from a third dielectric material, which is different from the second dielectric material but which may be the same as the first dielectric material 210.

[0155] In this embodiment, the coaxial cable 202 and radiating tip section 204 have an outer sheath 218 formed over their outermost surfaces. The outer sheath 218 may be formed from a biocompatible material. The outer sheath 218 has a thickness that is small enough to ensure that it does not significantly interfere with the microwave energy radiated by the radiating tip section 204 (i.e. radiating pattern and return loss). In an embodiment, the sheath is made from PTFE, although other materials are also appropriate. The thickness of the wall of the sheath is selected to withstand breakdown voltages equal to or greater than 200 kV/m.

[0156] The purpose of the dielectric tip 214 is to alter the shape of the radiated energy. The second dielectric material is selected to reduce the wavelength of the microwave energy, which results in the radiated energy exhibiting a more spherical radiation pattern. To do this, the second dielectric material preferably has a large dielectric constant (relative permittivity ϵ.sub.r). The dielectric constant of the second dielectric material is preferably chosen to enable the length of the dielectric tip 214 to be minimised whilst still constituting a non-negligible portion of a wavelength of the microwave energy when it propagates through the second dielectric material. It is desirable for the dielectric tip 214 to be as short as possible in order to retain flexibility in the device, especially if the second dielectric material is rigid. In an embodiment, the dielectric tip 214 may have a length equal to or less than 2 mm. The dielectric constant of the second dielectric material may be greater than 80, and is preferably 100 or more at the frequency of the microwave energy. The second dielectric material may be TiO.sub.2 (titanium dioxide).

[0157] The wavelength of radiation in a material becomes shorter as the dielectric constant of the material increases. Therefore a dielectric tip 214 with a greater dielectric constant will have a greater effect on the radiation pattern. The larger the dielectric constant, the smaller the dielectric tip 214 can be while still having a substantial effect on the shape of the radiation pattern. Using a dielectric tip 214 with a large dielectric constant means that the antenna can be made small and so the instrument can remain flexible. For example the dielectric constant in TiO.sub.2 is around 100. The wavelength of microwave radiation having a frequency of 5.8 GHz is about 6 mm in TiO.sub.2 compared to around 36 mm in PTFE (which may be the material used for the first and/or third dielectric materials). A noticeable effect on the shape of the radiation pattern can be produced in this arrangement with a dielectric tip 214 of approximately 1 mm. As the dielectric tip 214 is short, it can be made from a rigid material whilst still maintaining flexibility of the antenna as a whole.

[0158] The dielectric tip 214 may have any suitable distal shape. In FIG. 8 it has a dome shape, but this is not necessarily essential. For example, it may be cylindrical, conical, etc. However, a smooth dome shape may be preferred because it increases the mobility of the antenna as it is manoeuvred through small channels (e.g. inside blood vessels). The dielectric tip 214 may be coated with a non-stick material such as Parylene C or Parylene D, or PFTE to prevent the tissue from sticking to the instrument. The whole instrument can be coated in this way.

[0159] The properties of the intermediate dielectric sleeve 216 are preferably chosen (e.g. through simulation or the like) so that the radiating tip section 204 forms a quarter wave impedance transformer for matching the input impedance of the generator into a biological tissue load in contact with the radiating tip section 204.

[0160] During treatment, the surrounding tissue absorbs the radiated energy. The volume of tissue into which the energy is delivered depends on the frequency of the microwave energy.

[0161] As seen on FIG. 8, the radiating tip portion 204 includes magnetostrictive transducer 240 which is coupled to the inner conductor 206 (e.g. directly or via distal conductive section 212) by a first connector 242 and which is coupled to the outer conductor 208 by a second connector 244. In the embodiment of FIG. 8, the transducer 240 is encased (e.g. partly or completely) in the intermediate dielectric sleeve 216; however, it is to be understood that the transducer 240 may instead be positioned on an inner or outer surface of the intermediate dielectric sleeve 216.

[0162] Further, the transducer 240 may alternatively be positioned elsewhere on the radiating tip portion, for example, in or on the radiating tip 214. In an embodiment, the transducer 240 has the same or similar construction to the transducer 800 of FIG. 6A.

[0163] In use, an electrical (e.g. current) signal for driving the transducer 240 may be introduced into the coaxial cable 202 at its proximal end (e.g. by generator 102, or generator 400). As described above with reference to FIGS. 1 to 5, the electrical signal may oscillate at an ultrasound frequency. On receiving this electrical signal, the coil of the transducer 240 induces an oscillating magnetic field around the magnetostrictive element the transducer 240 such that the magnetostrictive effect causes the magnetostrictive element to rapidly expand and contract at the ultrasonic frequency thereby generating ultrasonic vibrations. Since the transducer 240 is coupled to the radiating tip portion 204, these ultrasonic vibrations travel into the radiating tip portion and are then radiated out of the instrument 200 and into the surrounding biological tissue. The vibrations produce mechanical friction that generates thermal energy thereby resulting in extracellular heating followed subsequently by intracellular heating. In this way, the ultrasound vibrations can be used to treat (e.g. cut or coagulate) the biological tissue.

[0164] A further embodiment of an electrosurgical instrument will now be described with reference to FIGS. 9 to 12B, wherein the instrument comprises an electrosurgical vessel sealer device capable of delivering microwave energy, RF energy and ultrasonic vibrations to seal blood vessels. The electrosurgical vessel sealer may include the distal assembly 118 of FIG. 7, or the instrument 420 of FIG. 1. The electrosurgical vessel sealer may be used in open surgery, but may find particular use in procedures where there is restricted access to the treatment site. For example, the electrosurgical vessel sealer may be adapted to fit within the instrument channel of a surgical scoping device i.e. laparoscope, endoscope, or the like, as described above with reference to the scoping device of FIG. 7.

[0165] FIG. 9 shows a schematic perspective view of a distal end assembly 300 of an electrosurgical instrument that is an embodiment of the invention. The distal end assembly 300 is connected to an instrument shaft 302 which is dimensioned to fit within the instrument channel of a laparoscope or other surgical scoping device. The instrument shaft 302 comprises a tubular sheath that conveys a coaxial cable for carrying EM power (e.g. microwave and/or RF) to the distal end assembly together with various control wires or rods that are arranged to control physical manipulation of the distal end assembly, as discussed below.

[0166] In this example, the distal end assembly 300 comprises a pair of jaws 308, 310. The jaws 308, 310 are operably coupled to a collar 304 that is mounted on a distal end of the instrument shaft 302. In this example, the pair of jaws 308, 310 comprise a movable jaw 308 which is pivotal around a laterally extending pin 306 in the collar 304 to enable a gap between opposing inner surfaces of the jaws 308, 310 to be opened and closed. Although there is only one movable jaw in this example, in other embodiments, both jaws may be arranged to pivot relative to the collar 304. The collar 304 may be arranged to ensure that the jaws remain laterally aligned as they are moved together.

[0167] In the example shown in FIG. 9, the pair of jaws 308, 310 comprises a static jaw 310 that has an energy delivery structure 312 on its top surface, i.e. the surface that opposes a corresponding surface on the movable jaw 308. In use, the distal end assembly 308 is intended to grip biological tissues (and in particular a blood vessel) between the pair of jaws 308, 310. The pair of jaws 308, 310 are arranged to apply pressure to the biological tissue between the opposed surfaces and deliver energy (preferably microwave electromagnetic energy) into the tissue from the energy delivery structure 312.

[0168] In this embodiment, the energy delivery structure is present only on the static jaw 310. However, in other arrangements, there may be an energy delivery structure on both jaws, or only on a single movable jaw.

[0169] In this example, the energy delivery structure 312 comprises a coplanar microstrip antenna fabricated in the top surface of the status jaw 310. The coplanar microstrip antenna comprises a substrate 320 made of nonconductive dielectric material, e.g. ceramic or the like. The dielectric substrate 320 has a conductive layer fabricated on its underside (not visible in FIG. 9). On its top surface (i.e. the surface opposite the underside) the dielectric substrate 320 has a first conductive region in the form of a longitudinally extending finger electrode 314 disposed centrally thereon. A U-shaped second conductive region 316 is disposed on the top surface of the dielectric substrate 320 around the finger electrode 314 with a gap of exposed dielectric 315 separating the finger electrode 314 from the U-shaped region 316. A plurality of through holes 318 are formed, e.g. machined, through the U-shaped region 316 and dielectric substrate 315. The through holes 318 are filled with conductive material to electrically connect the conductive layer on the underside of the dielectric substrate 320 with the U-shaped conductive region 316. The finger electrode 314 has a contact pad 317 at a proximal end thereof. The inner conductor of the coaxial cable conveyed by the instrument shaft 302 is electrically coupled to the contact pad 317, e.g. by extending from the instrument shaft 302 to physically contact the contact pad 317. The finger electrode 314 provides an active region for the coplanar microstrip antenna. The conductive layer on the underside of the dielectric substrate 320 is electrically connected to an outer conductor of the coaxial cable conveyed by the instrument shaft 302. In conjunction with the conductive communication through the through holes 318, the U-shaped conductive region 310 forms a ground electrode for the coplanar microstrip antenna.

[0170] The configuration of the coplanar microstrip antenna shown in FIG. 9 is particularly advantageous because it confines the emitted field within the region defined by the pair of jaws 308, 310. As discussed below, very little energy is delivered to a region outside the pair of opposing surfaces. Moreover, by arranging the U-shaped conductive region 316 to extend around a distal end of the finger electrode 314, the coplanar microstrip antenna structure can prevent energy from escaping in the longitudinal direction distal to assembly 300.

[0171] The conductive layers mentioned above may be made from any suitable conductive material. Silver and gold are preferred because of their high conductivity and biocompatibility. Copper may also be used, although it is preferably plated with silver or gold in regions likely to contact biological tissue.

[0172] The coplanar microstrip antenna structure may be fabricated independently of the static jaw 310, e.g. using thin film deposition techniques. This construction of the coplanar microstrip antenna ensures two important performance features. Firstly, it ensures that the projected energy applied to the biological tissue of the gripped vessel is focused inwardly within the grasp of the instrument jaws. This provides a localised energy delivery effect, whereby the applied energy is efficiently delivered to a desired region of tissue.

[0173] Moreover, the use of thin film conductive layers means that the thermal mass of the conductive lines is minimal. In combination with the effective thermal barrier provided by the dielectric substrate 320, this means that any residual heat within the conductive lines quickly dissipates. The effect can be further enhanced by providing a layer on the surface opposing the coplanar microstrip antenna that also acts as a thermal barrier. In the embodiments shown in FIG. 9, the moveable jaw 308 has a layer of resiliently deformable material 322 formed on its inner surface. The layer 322 may be formed from silicone rubber or other compliant polymer material that can withstand the temperatures that occur during treatment and are biocompatible. They may be fabricated from an elastomeric thermoplastic polymer, for example. This layer both assists in efficient delivery of energy to gripped biological tissue, but also facilitates retaining the biological tissue within the jaws.

[0174] Alternatively or additionally, a coating may be applied to the surface of the coplanar microstrip antenna itself. This may be a coating applied only to the conductive regions, e.g. to minimise tissue sticking. In embodiments arranged to deliver microwave energy, it may not be necessary for the inner surfaces of the jaws to make direct electrical conductive contact with tissue. Accordingly, the coating may be a thin high temperature polymeric material, e.g. applied across the whole face of the antenna. The specific material may be chosen to exhibit high loss and appear transparent to the microwave energy.

[0175] The coating may conform to the shape of the jaws. It may comprise a silicone-based passivation material similar to that used as a protective coating on printed circuit boards. Other examples include polyimide, PTFE or FEP type materials.

[0176] As shown in FIG. 9, the layer 322 has a plurality of ridges moulded into it. It therefore presents a textured or toothed surface with which to contact biological tissue. A similar ridged or textured grip may be provided around the periphery of the coplanar microstrip antenna. As mentioned above, these textured surfaces can aid the release of gas during the vessel sealing operation.

[0177] The coplanar microstrip antenna has a size suitable for receiving and sealing biological vessels. For example, the coplanar microstrip antenna may be arranged to provide an effective treatment area having a width (i.e. dimension extending laterally with respect to the axis of the coaxial cable) of 2 to 5 mm and a length (along the axis of the device) of 15 to 26 mm.

[0178] Operation of the instrument 300 may be controlled by an actuation mechanism (e.g. the trigger 110 of FIG. 7), which may take the form of a scissor-type handle, slider, rotatable dial, level, trigger or the like. The actuation mechanism can be operably coupled to the instrument 300 via one or more control wires that extend along the instrument shaft 302, e.g. within the instrument channel of a scoping device. In one example, the actuation mechanism may include a force limiter arranged to limit the maximum actuation force that can be supplied to the instrument. Limiting the maximum actuation force may assist in preventing damage to delicate components in the instrument 300, and can ensure that the force applied to tissue remains within desired parameters. The force limited may comprise a compression spring or ratchet mechanism as part of the actuation mechanism. In some examples it may be desirable to vary the maximum actuation force, e.g. by provide a dial or switch on the interface joint 106 that adjusts the maximum actuation force associated with the actuation mechanism.

[0179] The pair of jaws may include a stand-off (not shown) that ensures that the jaws remain separated by a minimum distance irrespective of the closure force applied by an associated actuation mechanism located at the proximal end of the instrument shaft 302. The stand-off may be a physical projection on one or both jaws that engages the inner surface of the opposite jaw.

[0180] It is desirable for the pressure applied by jaws to tissue held therebetween to be uniform in a longitudinal direction along the inner surfaces of the jaws. In a development of the structure shown in FIG. 9, the movable jaw 308 may comprise an engagement plate at its inner surface that is capable of articulating back into the jaw 308 about a pivot point located at a distal end of the jaw 308. A resiliently deformable support element may be mounted in the jaw 308 behind the engagement plate to urge it outwardly. With this arrangement, tissue in the region between the jaws is grasped between the inner surface of the static jaw and the engagement plate of the movable jaw. As the jaws are closed, the pressure applied along the jaws is generated by a combination of the pivoting action of the jaws and the articulation of the engagement plate. The location of the pivot point and properties of the resiliently deformable support element can be selected so that the non-uniformity in applied force that arises changing mechanical advantage along the jaws away from the pivot is balanced by a cooperating non-uniformity arising from the pivotable articulation of the engagement plate.

[0181] The energy delivery structure 312 described with respect to FIG. 9 is a coplanar microstrip antenna. The configuration of that antenna may be as shown in FIG. 9, however, alterative microwave radiator structures can be used. For example the top surface of the static jaw 310 may be provided with other microstrip-based energy delivery configurations, e.g. meandering or interdigitated microstrip lines. In another embodiment, the energy delivery structure may be a travelling wave antenna.

[0182] In addition to the function of the vessel sealing, the electrosurgical instrument of the present invention also functions as a vessel divider, e.g. to cut through and separate a sealed section of a blood vessel. In one embodiment, the vessel sealer may be provided with a blade 326 that is slidably mounted with respect to the pair of jaws 308, 310 to cut through biological tissue held between the jaws. In FIG. 9, the blade 326 is shown as protruding into the region between the open jaws in FIG. 9. However, in practice, it is desirable for the instrument to prevent forward movement of the blade until after the jaws are closed and microwave energy is applied.

[0183] In the embodiment shown in FIG. 9, the blade 326 is movable in a longitudinal direction, e.g. along the axis of the device. The opposed surfaces of the jaws 308, 310 contain respective recess or guide grooves 328, 324 for receiving the blade as it travels. The guide groove 324 in the static jaw 310 is formed within the finger electrode 314 so that it moves through the centre of the applied field.

[0184] In other embodiments, the blade may be mounted within one of the jaws and arranged to move laterally with respect to the longitudinal direction, i.e. to extend out of one of the opposed surfaces into gripped tissue. The sharp edge of the blade may lie below the opposed surface during the vessel gripping and sealing operation.

[0185] In one embodiment, the cutting functionality of the blade is provided or enhanced by a magnetostrictive ultrasound transducer (not visible in FIG. 9). The transducer may have the same construction as the transducer 800 of FIG. 6A. The location of the transducer may vary between embodiments, but generally speaking it is located towards a proximal end of the blade 326 so that when the transducer generates ultrasonic vibrations, those vibrations travel along the blade 326 to enable or assist in the cutting action of the blade 326. In an embodiment, the transducer is connected to a proximal end portion of the blade 326. Where the electric drive signal for the transducer is conveyed by the coaxial cable in the instrument shaft 302, the transducer has a first input terminal coupled to one conductor (e.g. inner conductor) of the coaxial cable and a second input terminal coupled to the other conductor (e.g. outer conductor) of the coaxial cable. For example, first and second connectors (e.g. wires, tracks, cables, and conductors) may couple each terminal to its respective conductor of the coaxial cable. In this way, an electrical (e.g. current) signal for driving the magnetostrictive ultrasound transducer may be conveyed by the coaxial cable, and delivered to the transducer at the proximal end of the blade 326. In operation, the transducer may generate ultrasonic vibrations which enable or enhance a cutting action of the blade 326. Specifically, as described above with reference to FIGS. 1 to 5, the electrical signal may oscillate at an ultrasound frequency. On receiving this electrical signal, the coil of the transducer induces an oscillating magnetic field around the magnetostrictive element the transducer such that the magnetostrictive effect causes the magnetostrictive element to rapidly expand and contract at the ultrasonic frequency thereby generating ultrasonic vibrations. Since the transducer is coupled to the blade 326, these ultrasonic vibrations travel into the blade 326 and are then radiated into the tissue surrounding the blade 326. The vibrations produce mechanical friction that generates thermal energy thereby resulting in extracellular heating followed subsequently by intracellular heating. In this way, the ultrasound vibrations can be used to treat (i.e. cut) the biological tissue.

[0186] The distal end assembly may be configured to perform functions in addition to vessel sealing. For example, the distal end assembly may have an auxiliary radiofrequency (RF) cutting blade mounted on a distal tip thereon. In the example shown in FIG. 9, an RF dissector element 330 is mounted on the distal end of the static jaw 310. The RF dissector element 330 is a bipolar structure that comprises an active electrode mounted on a protruding body, and a return electrode, which may be fabricated on or integrated with the static jaw 310 in the vicinity of the protruding body.

[0187] FIG. 10 shows the underside of the distal end assembly 300, where the RF dissector element 330 can be seen in more detail. The RF dissector element 330 can be used for fine bloodless tissue cutting and tissue dissection. In the arrangement shown in FIGS. 9 and 10, the RF dissector element 330 presents a leading edge that sits proud of the distal end of the static jaw 310 This position can enable both side and end-on dissection to be performed. In dry field treatment scenarios (i.e. in the absence of saline or other electrically conductive fluid) it is desirable for the return electrode to be in close proximity to the active electrode that is on the RF dissector element 330. The ratio of the exposed tissue contacting electrode areas is also important to ensure that current flow occurs in a desired manner that causes maximum current density to occur on the leading edge of the RF dissector element 330.

[0188] Although the RF dissector element 330 is shown at the distal end of the static jaw in FIGS. 9 and 10, it can be mounted in a variety of orientations or locations on the distal end assembly, e.g. vertically, horizontally, at an angle, on one side, and on either jaw.

[0189] The pair of jaws may have any suitable shape. For example, the jaws may be tapered along their length towards the distal tip, or may be bent or hooked if desired for any particular treatment scenario.

[0190] Opening and closing of the jaws 308, 310 may be controlled by an actuation mechanism that is operable by a user at an external handle of the surgical scoping device, i.e. at a proximal end of the instrument shaft 302 (e.g. trigger 110 of interface joint 106). The actuation mechanism may include a pressure control device arranged to enable a user to control closure of the pair of jaws based on an amount of pressure applied to the biological tissue that is captured between the jaws. In one example, a user may select a desired (e.g. maximum) closure pressure for the jaws, and the actuation mechanism may be arranged to inhibit further movement of the jaws towards each other once the desired pressure is reached.

[0191] As mentioned above, in some embodiments, both of the jaws may be active in the sense that they are electrically connected to a coaxial cable within the instrument shaft. In one example the pair of jaws comprise different elements of a single microwave energy delivery device. For example, one of the jaws may comprise a ground electrode, and the other may comprise an active electrode for an antenna structure. In another example, each jaw may comprise its own independent microwave energy delivery structure, e.g. corresponding to the coplanar microstrip antenna described above.

[0192] If both of the jaws are active, they may be fed from a common coaxial transmission line within the instrument shaft by providing a microwave power divider or splitter at the distal end of the coaxial transmission line, e.g. at the distal end of the instrument shaft, or within the collar 304. The microwave power splitter may be implemented in any known manner. For example, the power splitter could be implemented as a Wilkinson power splitter, as two quarter wavelength (or odd multiple thereof) impedance transformers or as a half wavelength balun arrangement, where the distal end of the coaxial line forms an unbalanced feed that is input to the first jaw, and where the second jaw is fed from a point that is half an electrical wavelength away from the feed. Alternatively, the power splitter may be implemented as half electrical wavelength impedance transformers that are fabricated using flexible substrate materials, which are able to flex to allow for moving one or both jaws.

[0193] In arrangements where the distal end assembly also includes an auxiliary device for delivering RF energy, the instrument may be arranged to receive the RF energy for the auxiliary device and the microwave energy for delivery from the jaws along a common energy delivery pathway, which may be a coaxial transmission line within the instrument shaft. In one example, RF energy may be delivered at 400 kHz, whereas the microwave energy may be delivered at 5.8 GHz. In order to prevent the microwave energy from entering the auxiliary device an inductive blocking or filtering component may be mounted within the distal end assembly. The inductive block may be a wire-wound inductor, which permits RF energy to pass through the use of parasitic effects, but blocks microwave energy. Alternatively, the inductive block may be provided by one or more quarter wavelength open stubs located at half wavelength intervals along a transmission line between the coaxial cable and the auxiliary RF device. In order to prevent RF energy from entering the microwave energy delivery structure in the jaws, a capacitive block or filter element may be mounted between the coaxial cable and the microwave energy delivery structure. The capacitive filter element may be a parallel plate capacitor that operates at microwave frequencies, or a waveguide cavity or coupled microstrip line where an insulating dielectric breaks the conductive path in the manner that blocks flow of RF energy.

[0194] Similar blocks or filters may be used at the generator to prevent RF energy from entering the microwave source and microwave energy from entering the RF source. For example one or more chokes may be provided to prevent microwave energy from radiating into the RF source.

[0195] In the example above, the RF and microwave energy is carried along the instrument shaft by a common coaxial transmission line. In other examples, the separation of the RF and microwave energy may occur before they are delivered into the instrument shaft. In this arrangement, separate energy conveying structures are provided for the RF energy and microwave energy respectively. For example, the RF energy can be conveyed by a twisted wire pair or two insulated wire assemblies mounted in parallel, whilst the microwave energy is carried by a suitable coaxial transmission line. Power for the ultrasound transducer can be delivered in a similar manner, e.g. in a coaxial cable with the microwave EM energy (and RF EM energy), or separately from the coaxial cable in a twisted wire pair (e.g. separately or with the RF EM energy).

[0196] FIG. 11 shows a view of the underside of the distal end assembly when the jaws 308, 310 are closed. This is a configuration in which the instrument may be introduced to an instrument channel of a laparoscope.

[0197] FIGS. 12A and 12B show in more detail a first example of a coplanar microstrip antenna that can be used as an energy delivery structure 312 in an embodiment of the invention. The coplanar microstrip antenna comprises a dielectric substrate 320 which has a conductive ground layer 336 on its under surface (see FIG. 12B) and a pair of conductor lines 314, 316 on its upper surface. The ground layer 336 and the conductor lines 314, 316 may be formed on the substrate using any suitable technique, e.g. metallisation, thin film deposition and patterning (etching), etc.

[0198] As discussed above, the pair of conductive lines 314, 316 in this example comprise a finger electrode 314 that is surrounded along its length and around its distal end by a U-shaped conductive region 316. The U-shaped conductive region 316 is electrically connected to the ground layer 336 via through holes 318, 338 which are filled with conductive material to provide an electrical connection. The finger electrode 314 and u-shaped conductive region 316 are separated by a gap 315 across which the microwave field is concentrated in use. The ground conductor 336 is in electrical communication with an outer conductor of a coaxial feedline, whereas the finger electrode 314 is electrically connected to an inner conductor of the coaxial feedline.

[0199] In a variant of the embodiment of FIGS. 9 to 12B, the blade 326 or blade mechanism may not include a magnetostrictive ultrasound transducer and, instead, the blade 326 may provide a “cold” cut, and comprise a sharp scalpel-type structure, made of steel or other hard material. However, cutting functionality could additionally or alternatively be provided or enhanced by thermal means other than ultrasonic vibration, e.g. a radiofrequency (RF) monopolar or bipolar energy delivery structure. An arrangement for delivering auxiliary power down the instrument shaft, e.g. for an RF cutting blade, is discussed above. In such cases, the magnetostrictive ultrasound transducer may be located elsewhere in the distal tip assembly. Three different embodiments will now be described.

[0200] Firstly, the magnetostrictive ultrasound transducer may be located in or on one of the jaws. Where the transducer is “in” one of the jaws, the transducer may be completely inside the jaw's volume, and where the transducer is “on” one of the jaws, the transducer may be on a surface of the jaw and, possibly, partly inside the jaw's volume. As such, when the transducer generates ultrasonic vibrations the whole jaw vibrates to assist in treating (e.g. dividing) tissue positioned between the jaws. In the case where the jaw 308 does not include a microwave or RF delivery structure, the jaw 308 may contain the transducer encased (partly or completely) within its volume. As such, the jaw 310 may function to deliver microwave EM energy into tissue positioned between the jaws, and the jaw 308 may function to deliver ultrasonic vibrations into tissue positioned between the jaws. It is to be understood, that in this embodiment the transducer is electrically coupled to the structure (e.g. coaxial cable, twisted wire pair) for conveying the transducer's electrical drive signal through the instrument shaft 302.

[0201] Secondly, in another embodiment in which one of the jaws includes the magnetostrictive ultrasound transducer for delivering ultrasonic energy to perform cutting, the transducer may be mounted on an independently slidable member that can be longitudinally extended and retracted with respect to the instrument shaft 302. This can assist in improving visibility of fine treatment using the transducer, as it can be extended into the field of view of the surgical scoping device independently of the rest of the distal end assembly 300. In one embodiment, the independently slidable member may be the static jaw 310, which can be dislocated from the collar 304 to enable it to slide longitudinally. The static jaw may be either retractable proximally away from its normal hinged location, or may be extendable distally away from its normal hinged location. In the latter scenario, the transducer may be located on the static jaw, so that it is can be moved into a distalmost position. In the former scenario, transducer may be located on the opposing jaw so that is occupies a distalmost position having good visibility when the static jaw is retracted.

[0202] Thirdly, in a further embodiment, a single jaw (e.g. jaw 310) may deliver both microwave EM energy and ultrasonic vibrations into tissue positioned in-between the jaws. For example, considering the coplanar microwave antenna structure of FIGS. 12A and 12B, one or more magnetostrictive ultrasound transducers may be positioned within the coplanar microwave structure, e.g. in-between the active conductive strip and the ground conductive strip. For example, the one or more transducers may be arranged in—between the finger electrode 314 and the U-shaped electrode 316. Since space is restricted in this location, it may be necessary to include multiple transducers because the maximum size for each individual transducer may be smaller compared to the aforementioned embodiments in which the transducer positioned either at the proximal end of the blade 326 or in/on one of the jaws. Therefore, the combined magnitude of the ultrasonic vibrations generated by multiple smaller transducers positioned in-between the electrodes 314 and 316 may be comparable to the magnitude of the ultrasonic vibrations generated by a single larger transducer positioned either at the proximal end of the blade 326 or in/on one of the jaws. Furthermore, each transducer positioned in-between the electrodes 314 and 316 may be located at or near a top surface of the dielectric substrate 320 such that the source of the ultrasonic vibrations is as close as possible to the tissue being treated, in order to minimise attenuation of the vibrations before they reach the tissue. In an embodiment, two, three, five, ten or more transducers may be positioned in-between the electrodes 314 and 316. An embodiment with eight such transducers 350a-h is shown in FIG. 13. Though connection lines are not visible in FIG. 13, it is to be understood that each transducer is electrically coupled to the structure for conveying the transducer's electrical drive signal through the instrument shaft 302 (e.g. coaxial cable, twisted wire pair). For example, each transducer 350a-h may have a first terminal coupled to ground layer 336 (e.g. via electrode 316) and a second terminal coupled to the electrode 314. Also, each transducer 350a-h may be driven by the same or separate electrical drive signals.

[0203] In the aforementioned description with respect to FIGS. 8 to 13, various embodiments have been described in which one or more magnetostrictive ultrasound transducers are positioned on a distal end assembly of an electrosurgical instrument. However, in a further embodiment, the distal end assembly may not include any magnetostrictive ultrasound transducers and, instead, the instrument shaft (e.g. a distal end) may include one or more magnetostrictive ultrasound transducers. In this way, the or each transducer can be easily coupled to the structure within the shaft which conveys the electrical signal for driving the or each transducer. Also, the ultrasonic vibrations generated by the or each transducer are generated at the distal end of the shaft can travel through the distal end assembly of the instrument to reach biological tissue for tissue treatment. An advantage of this arrangement is that finding a suitable space for housing the transducer and providing connections between the shaft and transducer may be easier.

[0204] The features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

[0205] While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.

[0206] For the avoidance of any doubt, any theoretical explanations provided herein are provided for the purposes of improving the understanding of a reader. The inventors do not wish to be bound by any of these theoretical explanations.

[0207] Throughout this specification, including the claims which follow, unless the context requires otherwise, the words “have”, “comprise”, and “include”, and variations such as “having”, “comprises”, “comprising”, and “including” will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

[0208] It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent “about,” it will be understood that the particular value forms another embodiment. The term “about” in relation to a numerical value is optional and means, for example, ±10 %.

[0209] The words “preferred” and “preferably” are used herein refer to embodiments of the invention that may provide certain benefits under some circumstances. It is to be appreciated, however, that other embodiments may also be preferred under the same or different circumstances. The recitation of one or more preferred embodiments therefore does not mean or imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the disclosure, or from the scope of the claims.