HK40005675B - Electrosurgical apparatus and method for promoting haemostasis in biological tissue - Google Patents

Description

Electrosurgical device and method for promoting hemostasis in biological tissue

Field of the Invention

The present invention relates to an electrosurgical device for coagulating biological tissue. In particular, the present invention relates to a composite radiofrequency (RF) and microwave energy waveform for delivery from an electrosurgical generator to a bipolar electrode configuration at the distal end of an electrosurgical instrument. The composite radiofrequency (RF) and microwave energy waveform is arranged to promote effective hemostasis in biological tissue by effectively delivering thermal energy.

Background of the Invention

Surgical resection is a means of removing part of an organ from the human or animal body. Such organs may have a large number of blood vessels. When tissue is cut (incised or severed), tiny blood vessels called arterioles are damaged or ruptured. The initial bleeding is followed by a coagulation cascade, in which the blood is converted into a clot in an attempt to block the bleeding site. During the operation, it is desirable for the patient to lose as little blood as possible, so various devices have been developed in an attempt to provide bloodless resection. For endoscopic procedures, it is also undesirable to have bleeding and not treat it as quickly as possible or in a stopgap manner, because the blood flow may obstruct the operator's vision, which may lead to the need to terminate the procedure and use another method instead, such as open surgery.

Electrosurgical generators are ubiquitous in hospital operating rooms for both open and laparoscopic procedures and are increasingly found in endoscopy suites. During endoscopic procedures, electrosurgical accessories are typically inserted through a lumen within an endoscope. This lumen has a relatively narrow bore and is much longer than the equivalent access channel used for laparoscopic surgery. In the case of obese patients, the length of the surgical accessory from the handle to the RF tip can be 300 mm, while in the case of laparoscopy, the equivalent distance can exceed 2500 mm.

Instead of a sharp blade, it is known to use radiofrequency (RF) energy to cut biological tissue. Methods of cutting using RF energy operate on the following principle: when an electric current passes through the tissue matrix (by virtue of the ionic content of the cells and the intercellular electrolytes), the resistance to the flow of electrons across the tissue generates heat. When an RF voltage is applied to the tissue matrix, sufficient heat is generated within the cells to evaporate the tissue's moisture. Due to this enhanced dehydration, particularly near the instrument's RF emission region (which has the highest current density of the entire current path through the tissue), tissue near the instrument's cutting pole loses direct contact with the blade. The applied voltage then appears almost completely across this gap, which is then ionized, forming a plasma with a very high volume resistivity compared to the tissue. This differentiation is important because it concentrates the applied energy into the plasma, which completes the electrical circuit between the instrument's cutting pole and the tissue. Any volatile matter that enters the plasma slowly enough is evaporated, and thus the tissue-dissecting plasma is perceived.

GB 2 486 343 discloses a control system for an electrosurgical device for delivering both RF and microwave energy to treat biological tissue. The energy delivery profiles of both RF and microwave energy delivered to a probe are set based on sampled voltage and current information of the RF energy delivered to the probe, and sampled forward and reflected power information of the microwave energy delivered to and from the probe.

FIG3 shows a schematic diagram of an electrosurgical device 400 as described in GB 2 486 343. The device includes an RF channel and a microwave channel. The RF channel contains components for generating RF frequency electromagnetic signals and controlling them to a power level suitable for treating (e.g., cutting or dehydrating) biological tissue. The microwave channel contains components for generating microwave frequency electromagnetic signals and controlling them to a power level suitable for treating (e.g., coagulating or ablating) biological tissue.

The microwave channel has a microwave frequency source 402, followed by a power splitter 424 (e.g., a 3dB power splitter) that splits the signal from source 402 into two branches. One branch from power splitter 424 forms a microwave channel having a power control module comprising a variable attenuator 404 controlled by controller 406 via control signal _V10 and a signal modulator 408 controlled by controller 406 via control signal _V11 ; and an amplifier module comprising a driver amplifier 410 and a power amplifier 412 for generating forward microwave EM radiation for delivery from probe 420 at a power level suitable for treatment. Following 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 probe along a path between its first and second ports; a forward coupler 414 located at the first port of circulator 416; and a reflective coupler 418 located at the third port of circulator 416. After passing through the reflective coupler, the microwave EM energy from the third port is absorbed in the power dump load 422. The microwave signal coupling module further includes a switch 415, which is operated by the controller 406 through a control signal _V12 for connecting the forward coupled signal or the reflected coupled signal to the heterodyne receiver for detection.

Another branch from power divider 424 forms a measurement channel. The measurement channel bypasses the amplification array on the microwave channel and is therefore arranged to deliver low-power signals from the probe. In this embodiment, a main channel selector switch 426, controlled by controller 406 via control signal _V13, is operable to select signals from either the microwave channel or the measurement channel for delivery to the probe. A high-bandpass filter 427 is connected between main channel selector switch 426 and probe 420 to protect the microwave signal generator from low-frequency RF signals.

The measurement channel includes components arranged to detect the phase and amplitude of power reflected from the probe, which can generate information about the substance (e.g., biological tissue present at the distal end of the probe). The measurement channel includes a circulator 428, which is connected to deliver microwave EM energy from source 402 to the probe along a path between its first and second ports. The reflected signal returning from the probe is directed into a 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, since the circulator does not provide complete isolation between its first and third ports, that is, a portion of the forward signal can pass through to the third port and interfere with the reflected signal, a carrier cancellation circuit is used, which injects a portion of the forward signal (from the forward coupler 430) back into the signal exiting the third port (via the injection coupler 432). The carrier cancellation circuit includes a phase adjuster 434 to ensure that the injected portion is 180° out of phase with any signal passing from the first port to the third port, so as to cancel it out. The carrier cancellation circuit also includes a signal attenuator 436 to ensure that the injected portion has the same amplitude as any punch-through signal.

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 terminals of a switch 440, which is operated by the controller 406 via a control signal _V14 to connect either the coupled forward signal or the reflected signal to a heterodyne receiver for detection.

The output of switch 440 (i.e., the output from the measurement channel) and the output of switch 415 (i.e., the output from the microwave channel) are connected to corresponding input terminals of a secondary channel selection switch 442. The secondary channel selection switch 442 can be operated by the controller 406 in conjunction with the main channel selection switch through a control signal _V15 to ensure that: when the measurement channel supplies energy to the probe, the output of the measurement channel is connected to the heterodyne receiver, and when the microwave channel supplies energy to the probe, the output of the microwave channel is connected to the heterodyne receiver.

The heterodyne receiver is used to extract phase and amplitude information from the signal output by the secondary channel selection switch 442. A single heterodyne receiver is shown in this system, but if desired, a dual heterodyne receiver (containing two local oscillators and a mixer) can be used to downmix the source frequency twice before the signal enters the controller. The heterodyne receiver includes a local oscillator 444 and a mixer 448 for downmixing 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 for reception in the controller 406. Bandpass filters 446 and 450 are provided to protect the local oscillator 444 and the controller 406 from high-frequency microwave signals.

Controller 406 receives the output of the heterodyne receiver and determines (e.g., extracts) information indicative of the phase and amplitude of the forward and/or reflected signals on the microwave or measurement channels based on the output. 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. As discussed above, a user can interact with controller 406 via user interface 452.

The RF channel shown in FIG3 includes an RF frequency source 454 connected to a gate driver 456, which is controlled by the controller 406 via a control signal _V16 . The gate driver 456 supplies an operating signal to an RF amplifier 458, which is a half-bridge arrangement. The drain voltage of the half-bridge arrangement can be controlled by a variable DC power supply 460. An output converter 462 transmits the generated RF signal to a line for delivery to the probe 420. A low-pass, band-pass, band-stop, or notch filter 464 is connected to that line to protect the RF signal generator from high-frequency microwave signals.

A current transformer 466 is connected to the RF channel to measure the current delivered to the tissue load. A potentiometer 468 (which can be tapped from the output transformer) is used to measure voltage. The output signals from potentiometer 468 and current transformer 466 (i.e., voltage outputs indicating voltage and current) are directly connected to controller 406 after being conditioned by corresponding buffer amplifiers 470, 472 and voltage clamping Zener diodes 474, 476, 478, 480 (as shown by signals B and C in FIG3 ).

To obtain phase information, the voltage and current signals (B and C) are also connected to a phase comparator 482 (e.g., an EXOR gate). The output voltage of the comparator is integrated by an RC circuit 484 to generate a voltage output (shown as A in FIG3 ) that is proportional to the phase difference between the voltage and current waveforms. This voltage output (signal A) is directly connected to the controller 406.

The microwave/measurement channel and the RF channel are connected to a signal combiner 114 that transmits both types of signals individually or simultaneously along a cable assembly 116 to a probe 420 from which they are delivered (eg, radiated) into the patient's biological tissue.

A waveguide isolator (not shown) may be provided at the junction between the microwave channel and the signal combiner. The waveguide isolator may be configured to perform three functions: (i) allow very high microwave power (e.g., greater than 10 W) to pass through; (ii) block RF power from passing through; and (iii) provide a high withstand voltage (e.g., greater than 10 kV). A capacitive structure (also known as a DC disconnect) may also be provided at (e.g., within) or near the waveguide isolator. The purpose of the capacitive structure is to reduce capacitive coupling across the isolation barrier.

Summary of the Invention

Most generally, the present invention provides a waveform having both a radio frequency (RF) energy component and a microwave energy component, the waveform being arranged to perform effective hemostasis in biological tissue. In particular, the waveform is arranged to deliver energy rapidly, enabling hemostasis to occur within a short timeframe (e.g., 10 seconds or less, preferably 3 seconds or less) where the maximum available power is limited, for example due to limitations in the power delivery capabilities of the device being used, or to avoid undesirable thermal damage (e.g., dehydration or charring) to the biological tissue.

Thus, according to one aspect of the present invention, there is provided an electrosurgical apparatus comprising: an electrosurgical generator arranged to generate radio frequency (RF) electromagnetic energy and microwave electromagnetic energy; an electrosurgical instrument having a distal tip assembly for delivering the RF electromagnetic energy and the microwave electromagnetic energy into biological tissue; and a feeder cable connected to deliver the RF electromagnetic energy and the microwave electromagnetic energy from the electrosurgical generator to the bipolar electrosurgical instrument, wherein the electrosurgical generator is arranged to detect a voltage and a current associated with the delivered RF electromagnetic energy, and wherein the generator is operable to: determining an impedance based on the detected voltage and current; and delivering the RF electromagnetic energy and the microwave electromagnetic energy in a composite waveform for promoting hemostasis in biological tissue, the composite waveform comprising: a first portion, the first portion primarily comprising RF electromagnetic energy, and a second portion, following the first portion, the second portion primarily comprising microwave electromagnetic energy, wherein the second portion further comprises a plurality of RF pulses, wherein the first portion transitions to the second portion when either: a duration of the first portion reaches or exceeds a predetermined duration threshold, or an impedance determined by the generator during the first portion reaches or exceeds a predetermined impedance threshold.

In this arrangement, the composite waveform delivers thermal energy using the RF signal when the tissue is in a state capable of receiving energy delivery by conduction. Energy delivery continues in this manner until the tissue changes state (e.g., becomes dehydrated) in a manner that means RF energy can no longer be effectively delivered, or until a certain amount of thermal energy has been delivered. At this point, hemostatic treatment continues using microwave energy, which can provide a direct heating effect deeper into the tissue without the risk of scorching the tissue surface.

The predetermined duration threshold may be equal to or less than 1 second. In practice, the predetermined duration threshold may be set based on the expected energy delivered by the RF electromagnetic energy during the first portion. For example, it may be desirable to deliver 7 joules of energy during the first portion. The voltage and current of the RF electromagnetic energy may be controlled to ensure that no more energy than expected is delivered within the predetermined duration threshold.

The electrosurgical generator may be arranged to determine an initial impedance based on the detected voltage and current associated with the RF electromagnetic energy delivered at the beginning of the first portion, wherein the predetermined impedance threshold is a preset ratio of the initial impedance. This means that it is not necessary to set an absolute value for the predetermined impedance threshold. This is because as tissue dehydrates and becomes less conductive, its impedance increases. By monitoring this increase, the transition to the second portion can occur before dehydration reaches a level that presents an increased risk of permanent tissue damage, for example due to charring. The preset ratio may be equal to or greater than 1.25, i.e., the transition occurs when the determined impedance is 25% greater than the initial impedance.

The RF electromagnetic energy may be delivered as a continuous wave signal in the first portion. However, this is not required. The RF energy may be delivered as a series of pulses, for example, as described in WO2014/181078.

If a continuous wave signal is used for the RF electromagnetic energy, the signal may have an RMS voltage in the range of 90-120 V. This may ensure that heating gradually subsides as impedance increases in a manner that reduces the risk of inadvertent thermal damage.

Preferably, the generator is arranged to output only RF energy in the first portion, ie no microwave electromagnetic energy is delivered in the first portion.

During the second portion, the microwave energy can be delivered as a continuous wave (e.g., having a preset (preferably user-selectable) power level). The plurality of RF pulses can be supplied concurrently with the microwave electromagnetic energy, i.e., the RF electromagnetic energy and the microwave electromagnetic energy can be supplied simultaneously for the duration of each RF pulse. Alternatively, the delivery of the microwave electromagnetic energy can be paused during each RF pulse. Each RF pulse in the plurality of RF pulses can be arranged to have a negligible thermal effect on the biological tissue. For example, the voltage and current associated with the RF pulses and/or the duration can be limited in a manner that prevents thermal effects but enables impedance measurements to be obtained.

The plurality of RF pulses may be supplied in a regular, eg, periodic, manner.

The generator may be arranged to determine an impedance value based on the detected voltage and current associated with each of the plurality of RF pulses delivered during the second portion. These determined impedance values may be used to calculate an amount of thermal energy delivered by the electrosurgical instrument.

The generator may be operable to terminate the second portion upon either: the amount of thermal energy delivered by the electrosurgical instrument reaches or exceeds a predetermined thermal energy threshold, or the duration of the composite waveform reaches or exceeds a predetermined total duration threshold. The predetermined total duration threshold may be set to prevent thermal diffusion effects from causing unwanted damage to tissue surrounding the treatment area. The risk of such damage may depend on the area of the patient's body being treated. Thus, the predetermined total duration threshold may be capable of varying depending on the type of treatment, and in one example, the predetermined total duration threshold may be equal to or less than 10 seconds. In another example, the predetermined total duration threshold may be equal to or less than 3 seconds.

Alternatively or additionally, the generator may be operable to terminate the second portion when an impedance determined based on the detected voltage and current reaches or exceeds a predetermined threshold. In other words, information derived from the plurality of RF pulses may be used to shorten the second portion, for example to prevent tissue from burning or adhering to the instrument.

The generator may include a display configured to display any one or more of: an impedance determined from the detected voltage and current; a selected power of the microwave electromagnetic energy; an amount of energy delivered from the electrosurgical instrument; and information indicative of tissue status at the distal tip assembly. The information indicative of tissue status may be derived from the determined impedance value and may be, for example, a simple graphical indicator showing the presence or absence of bleeding in the tissue being treated.

The electrosurgical instrument can be a device suitable for delivering RF and microwave energy. For example, the electrosurgical instrument can have a bipolar energy delivery configuration, wherein the distal tip assembly includes a first electrode and a second electrode separated by a dielectric material. The first and second conductive elements can be arranged to function as: an active electrode and a return electrode for conducting RF electromagnetic energy through biological tissue located near the distal tip assembly; and a near-field antenna for radiating the microwave electromagnetic energy into the biological tissue.

The feed cable may be a coaxial cable having an inner conductor separated from an outer conductor by a dielectric material. The inner conductor may be electrically connected to the first electrode or form a part thereof. The outer conductor may be electrically connected to the second electrode or form a part thereof.

The apparatus of the present invention may include or be used with a surgical viewing device (e.g., an endoscope, a gastroscope, a laparoscope, etc.). The viewing device may have a housing for positioning outside a patient's body, and an instrument cord extending from the housing and insertable into the patient's body to reach a treatment site. The instrument cord may have an instrument channel extending therethrough, wherein the electrosurgical instrument and the feeder cable may be sized to fit within the instrument channel to deliver the RF electromagnetic energy and the microwave electromagnetic energy to the treatment site.

The present invention can be particularly advantageous when used in a scoping device environment, particularly where the maximum available microwave electromagnetic energy power at the distal end of the instrument channel is limited due to losses along the cable. If the maximum available microwave electromagnetic energy power is equal to or less than 40 W, the composite waveform of the present invention can achieve more rapid and effective hemostasis using microwave energy alone.

The generator described above may be an independent aspect of the present invention.

In another aspect of the present invention, a method of delivering RF electromagnetic energy and microwave electromagnetic energy from an electrosurgical generator to an electrosurgical instrument having a distal tip assembly for delivering RF electromagnetic energy and microwave electromagnetic energy into biological tissue is provided, the method comprising: operating the generator to deliver the RF electromagnetic energy and the microwave electromagnetic energy in a composite waveform for promoting hemostasis in biological tissue, the composite waveform comprising: a first portion, the first portion primarily comprising RF electromagnetic energy, and a second portion, following the first portion, the second portion primarily comprising microwave electromagnetic energy, wherein the second portion further comprises a plurality of RF pulses, wherein the first portion transitions to the second portion when either: a duration of the first portion reaches or exceeds a predetermined duration threshold, or an impedance determined by the generator during the first portion reaches or exceeds a predetermined impedance threshold.

The method may include any of the operations discussed above as performed by the generator.

In this specification, "microwave" is used broadly to refer to the frequency range of 400 MHz to 100 GHz, but is preferably used to refer to the range of 1 GHz to 60 GHz. Specific frequencies considered are: 915 MHz, 2.45 GHz, 3.3 GHz, 5.8 GHz, 10 GHz, 14.5 GHz, and 24 GHz. In contrast, this specification uses "radio frequency" or "RF" to refer to a frequency range at least three orders of magnitude lower, for example, up to 300 MHz, preferably 10 kHz to 1 MHz.

The present invention may be combined with any or all of the components (alone or in any combination) described above with reference to the electrosurgical apparatus 400 set out in GB 2 486 343. For example, the RF channel and microwave channel may comprise any or all of the components of the RF channel and microwave channel, respectively, described above.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention are discussed below with reference to the accompanying drawings, in which:

FIG1 is a schematic diagram illustrating an electrosurgical system for use in one embodiment of the present invention;

FIG2 is a cross-sectional view through an electrosurgical instrument suitable for use in the present invention;

FIG3 is an overall schematic system diagram of an electrosurgical apparatus in which the present invention may be used; and

FIG4 is a schematic representation of a composite coagulation waveform according to one embodiment of the present invention.

DETAILED DESCRIPTION

FIG1 is a schematic diagram of a complete electrosurgical system 100 capable of supplying RF energy and microwave energy to the distal end of an electrosurgical instrument. System 100 includes a generator 102 for controllably supplying radiofrequency (RF) and microwave energy. As shown, generator 102 may be included in electrosurgical device 400 discussed above with reference to FIG3 . Generator 102 may be arranged to monitor reflected signals received from the instrument to determine an appropriate signal to transmit to the instrument. For example, the generator may be arranged to calculate the impedance experienced at the distal end of the instrument to determine the optimal power level to be delivered. This is discussed in more detail below.

The generator 102 is connected to the interface connector 106 by the interface cable 104. The interface connector 106 can also be connected to receive a fluid supply 107 from a fluid delivery device 108 (such as a syringe), although this is not required. If necessary, the interface connector 106 can accommodate an instrument control mechanism that can be operated by a sliding trigger 110 to, for example, control the longitudinal (forward and backward) movement of one or more control lines or a push rod (not shown). If there are multiple control lines, multiple sliding triggers can be present on the interface connector to provide complete control. The function of the interface connector 106 is to combine the inputs from the generator 102, the fluid delivery device 108, and the instrument control mechanism into a single flexible shaft 112 extending from the distal end of the interface connector 106.

The flexible shaft 112 can be inserted through the entire length of an instrument (working) channel of a surgical scope 114 (such as an endoscope, gastroscope, laparoscope, etc.).

The surgical viewing device 114 includes a main body 116 having a plurality of input ports and an output port from which an instrument cord 120 extends. The instrument cord 120 includes an outer sheath surrounding a plurality of lumens. The plurality of lumens transmit various things from the main body 116 to the distal end of the instrument cord 120. One of the lumens is the instrument channel discussed above. Other lumens may include channels for transmitting optical radiation, for example, to provide illumination at the distal end or to collect images from the distal end. The main body 116 may include an eyepiece 122 for observing the distal end. In order to provide illumination at the distal end, a light source 124 (e.g., an LED, etc.) may be connected to the main body 116 by an illumination input port 126.

Flexible shaft 112 has a distal assembly 118 (not drawn to scale in FIG1 ) shaped to pass through an instrument channel of surgical scope 114 and protrude at the distal end of a bronchoscope tube (e.g., into a patient's body). The distal end assembly includes an active tip for delivering radiofrequency and/or microwave energy into biological tissue.

The distal assembly 118 can be configured to have a maximum outer diameter equal to or less than 2.0 mm, such as less than 1.9 mm (and more preferably less than 1.5 mm), and the flexible shaft can have a length equal to or greater than 1.2 m.

The body 116 includes a power input port 128 for connection to the flexible shaft, which includes a coaxial cable (e.g., a conventional coaxial cable) capable of transmitting RF and microwave energy from the generator 102 to the distal assembly 118. Coaxial cables that are physically capable of fitting into the instrument channel of the ENB device are available in the following outer diameters: 1.19 mm (0.047 in), 1.35 mm (0.053 in), 1.40 mm (0.055 in), 1.60 mm (0.063 in), and 1.78 mm (0.070 in). Custom-sized (i.e., purpose-built) coaxial cables may also be used.

It may be desirable to control the position of at least the distal end of the instrument cord 120. The body 116 may include a control actuator 130 mechanically coupled to the distal end of the instrument cord 120 by one or more control wires (not shown) extending through the instrument cord 120. The control wires may be routed within the instrument channel or within their own dedicated channels. The control actuator 130 may be a joystick or a rotatable knob, or any other known catheter manipulation device. Manipulation of the instrument cord 120 may be software-assisted, for example using a virtual three-dimensional map assembled from a computed tomography (CT) image.

FIG2 is a cross-sectional view of the distal end of an electrosurgical instrument 200 that can be used in the distal assembly 118 to deliver RF energy and microwave energy into biological tissue. The electrosurgical instrument 200 includes a coaxial cable 202 connected at its proximal end to an electrosurgical generator (not shown) for transmitting radio frequency (RF) and microwave energy. The coaxial cable 202 includes an inner conductor 206 separated from an outer conductor 208 by a first dielectric material 210. The coaxial cable 202 preferably has low loss for microwave energy. A choke (not shown) can be provided on the coaxial cable to inhibit reverse propagation of microwave energy reflected from the distal end and thereby limit heating backward along the device.

The coaxial cable 202 terminates at its distal end in a radiating end section 204. In this embodiment, the radiating end section 204 includes a distal conductive section 212 of the inner conductor 206 that extends ahead of the distal end 209 of the outer conductor 208. The distal conductive section 212 is surrounded at its distal end by a dielectric end 214 formed of a second dielectric material that may be the same as or different from the first dielectric material 210. The length of the dielectric end 214 is shorter than the length of the distal conductive section 212.

The coaxial cable 202 and the radiating end section 204 may have a biocompatible outer sheath (not shown) formed over their outermost surfaces. The outer sheath 218 may be formed of a biocompatible material.

The dielectric tip 214 may have any suitable distal shape, such as any of a dome shape, a cylinder shape, a cone shape, etc. A smooth dome shape may be preferred because it increases the mobility of the antenna as it is maneuvered through small passages.

FIG4 is a schematic representation of a composite coagulation (hemostasis) waveform 500 for delivery from an electrosurgical instrument such as discussed above in one embodiment of the present invention. In FIG4 , the waveform 500 is depicted as a graph having time along the x-axis and signal intensity along the y-axis. The waveform 500 includes an RF signal 502 and a microwave signal 504 supplied separately or simultaneously according to the modes set forth below.

The composite waveform 500 of the present invention includes a first portion 506 in which RF energy 502 is delivered alone or with microwave energy 504 at a level that has negligible effect on biological tissue. The impedance at the tip of the instrument is monitored by detecting the voltage and current associated with the delivered RF energy (e.g., using the detection setup discussed above with reference to FIG3 ).

Following the first portion 506, the composite waveform 500 includes a second portion 508, in which microwave energy 504 is delivered into the biological tissue. During the second portion, multiple short pulses 510 of concurrent RF energy are delivered in a periodic manner. The duration of each pulse 510 is arranged to enable an impedance measurement to be obtained. This impedance measurement can be used to determine the duration of the second portion 508, i.e., when to terminate the waveform 500. Additionally or alternatively, the measured impedance can be used to update a display (not shown) on the generator. The display can display the impedance value, or it can display a graphical representation of the tissue state at the distal end of the instrument, for example, to provide a concise indication of whether the tissue is bleeding. In another example, the impedance measurement can be used to update a calculation of the amount of energy delivered to the tissue, for example, using known information about the delivered power. The delivered energy dose can also be displayed to the operator. The display can be updated periodically, for example, at one-second intervals.

The transition between the first portion 506 and the second portion 508 occurs when the duration 512 of the first portion 506 reaches or exceeds a predetermined threshold, or when the detected impedance obtained during the first portion 506 reaches or exceeds a predetermined threshold, whichever occurs first. The predetermined threshold duration may be equal to or less than one second, and the predetermined threshold tissue impedance may be set as a specific ratio of the initial measured impedance. For example, the predetermined threshold may be set at 25% above the initial impedance value.

The purpose of the first portion 506 is to enable energy to be delivered as quickly as possible without causing tissue charring. The RF energy 502 in this portion can be a continuous wave signal having an RMS voltage set to a level that causes heating to gradually decrease as tissue impedance rises. For example, the RMS voltage of the RF energy can be set in the range of 90 to 120 V. The second portion 508 is arranged to be turned on after the first portion 506 to maintain the tissue heating (hemostasis) effect without the risk of tissue charring. Even if the tissue has already undergone a certain degree of local dehydration during the first portion, the microwave field emitted by the device can propagate through such dehydrated (and therefore non-conductive) tissue so that the coagulation performance does not cease.

The use of microwave frequency energy after applying RF energy is beneficial because a greater depth of direct tissue heating can be achieved, as opposed to the thermal diffusion effect that can be obtained from tissue heated only peripherally with the instrument.

The frequency of the microwave energy is selected to provide the desired heating depth. In general, the lower the microwave frequency, the greater the direct heating depth of biological tissue. Therefore, if treatment is to be performed in a location where there is concern about not damaging the muscle layer underlying the tissue to be treated, it is desirable to select a microwave frequency (such as 5.8 GHz or higher) so as to limit energy delivery to the desired area.

For similar reasons, it is desirable to deliver RF energy from an instrument with a bipolar electrode configuration, i.e., one in which the path of RF energy is localized in the area surrounding the instrument tip. This avoids limitations associated with monopolar instruments, in which the electrical pathway between the monopolar electrode tip in contact with tissue and its associated patient return pad follows the path of least resistance, which in turn can result in significant heating at some (unknown) distance from the instrument's point of contact with the tissue. In practice, the path of least resistance often passes through the contents of the blood vessel, which can increase the risk and extent of remote thermal damage.

Another constraint on the selection of the frequency of the microwave energy, which is particularly relevant when the instrument is inserted along the instrument channel of a surgical scope, is that the higher the microwave frequency, the greater the partial losses in the energy delivery cable. Losses in the cable lead to intraluminal heating, which must be limited or removed to prevent unwanted collateral damage along the length of the cable. Removing intraluminal heating may require circulating coolant, which requires a more complex delivery structure in an already constrained working environment. Limiting cable losses necessarily means that lower power is available at the distal end of the instrument. This may mean that more time is required to provide the required total amount of heat, which may be undesirable because the longer the treatment period, the greater the impact of thermal diffusion, which may cause damage to surrounding muscle tissue and lead to perfusion cooling, where blood flow acts to draw thermal energy away from the local treatment site.

Waveform 500 represents a balance between the factors summarized above. A first portion 506 delivers RF energy at a time when biological tissue is most receptive to RF energy (without causing charring or other undesirable thermal damage), while a second portion 508 continues the hemostatic effect initiated by the RF energy in the first portion 506 to deliver the total amount of thermal energy for the desired duration.

The duration 514 of the waveform 500 is preferably equal to or less than ten seconds in order to control the area of tissue damage caused by thermal diffusion. However, the actual duration acceptable may vary depending on the location of the treatment area. For example, treatment in the lower gastrointestinal tract may need to have a shorter total treatment time, such as equal to or less than three seconds, in order to avoid damage to surrounding muscle tissue. On the other hand, if the bleeding to be coagulated is in tissue that is not tightly coupled to the wall of the gastrointestinal tract, such as in the case of a pedunculated polyp, then the coagulation waveform 500 can be repeatedly applied without causing unwanted damage. During the second portion 508, the microwave energy can be supplied as a continuous wave signal having a preset (e.g., user-defined) power level.

Claims (22)

1. An electrosurgical device comprising: An electrosurgical generator, which is arranged to generate radio frequency (RF) electromagnetic energy and microwave electromagnetic energy; A bipolar electrosurgical instrument having a distal terminal assembly for delivering RF electromagnetic energy and microwave electromagnetic energy into biological tissue; and A feed cable is connected to deliver the RF electromagnetic energy and the microwave electromagnetic energy from the electrosurgical generator to the bipolar electrosurgical instrument. The electrosurgical generator is configured to detect the voltage and current associated with the delivered RF electromagnetic energy, and The generator described therein can be operated to: The impedance is determined based on the detected voltage and current; The RF electromagnetic energy and the microwave electromagnetic energy are delivered using a composite waveform for promoting hemostasis in biological tissues, the composite waveform comprising: The first part mainly includes RF electromagnetic energy, and The second part, following the first part, mainly includes microwave electromagnetic energy. The second part also includes multiple RF pulses. The generator is arranged to: During the first part, the impedance is determined based on the detected voltage and current; and The composite waveform transitions from the first part to the second part under any of the following conditions: The duration of the first portion reaches or exceeds a predetermined duration threshold, or The impedance determined during the first part reaches or exceeds a predetermined impedance threshold. 2. The electrosurgical device of claim 1, wherein the predetermined duration threshold is equal to or less than 1 second. 3. The electrosurgical device of claim 1 or 2, wherein the electrosurgical generator is arranged to determine an initial impedance based on detected voltage and current associated with the RF electromagnetic energy delivered at the beginning of the first portion, and wherein the predetermined impedance threshold is a preset proportion of the initial impedance. 4. The electrosurgical device according to claim 3, wherein the preset ratio is equal to or greater than 1.25. 5. The electrosurgical device according to claim 1 or 2, wherein the generator is arranged to deliver the RF electromagnetic energy as a continuous wave signal in the first part. 6. The electrosurgical device according to claim 5, wherein the continuous wave signal of the RF electromagnetic energy has an RMS voltage in the range of 90-120V. 7. The electrosurgical device according to claim 1 or 2, wherein the generator is arranged to prevent the delivery of microwave electromagnetic energy in the first part. 8. The electrosurgical device according to claim 1 or 2, wherein the generator is arranged to deliver the microwave energy as a continuous wave in the second part. 9. The electrosurgical device of claim 1 or 2, wherein the generator is arranged to determine an impedance value based on the detected voltage and current associated with each of the plurality of RF pulses delivered during the second portion. 10. The electrosurgical device of claim 9, wherein the generator is arranged to calculate the amount of thermal energy delivered by the bipolar electrosurgical instrument based on the determined impedance value. 11. The electrosurgical device according to claim 1 or 2, wherein the generator is arranged to supply the plurality of RF pulses concurrently with the microwave electromagnetic energy. 12. The electrosurgical device of claim 1 or 2, wherein the generator is arranged to supply the plurality of RF pulses in a periodic manner. 13. The electrosurgical device according to claim 1 or 2, wherein each of the plurality of RF pulses is arranged to have a negligible thermal effect on the biological tissue. 14. The electrosurgical device according to claim 1 or 2, wherein the generator is operable to: Determine the amount of thermal energy delivered by the bipolar electrosurgical instrument; and The second part shall be terminated under any of the following circumstances: The amount of thermal energy determined by the generator reaches or exceeds a predetermined thermal energy threshold, or The duration of the composite waveform reaches or exceeds a predetermined total duration threshold. 15. The electrosurgical device of claim 14, wherein the predetermined total duration threshold is equal to or less than 10 seconds. 16. The electrosurgical device of claim 14, wherein the predetermined total duration threshold is equal to or less than 3 seconds. 17. The electrosurgical device according to claim 1 or 2, wherein the generator is operable to: The impedance is determined based on the detected voltage and current associated with one of the plurality of RF pulses; and The second part terminates when the determined impedance reaches or exceeds a predetermined threshold. 18. The electrosurgical device of claim 1 or 2, wherein the generator includes a display arranged to display one or more of the following: The impedance is determined based on the detected voltage and current; The selected power of the microwave electromagnetic energy; The amount of energy delivered from the bipolar electrosurgical instrument; Information indicating the tissue status at the distal end assembly. 19. The electrosurgical device of claim 1 or 2, wherein the distal end assembly comprises a first electrode and a second electrode separated by a dielectric material. 20. The electrosurgical device of claim 19, wherein the first electrode and the second electrode are arranged to serve as: Active and return electrodes are used to conduct RF electromagnetic energy through biological tissue located near the distal end component, and A near-field antenna is used to radiate the microwave electromagnetic energy into biological tissue. 21. The electrosurgical device of claim 1 or 2, comprising a surgical endoscope having an instrument cord for insertion into a patient to reach a treatment site, the instrument cord having an instrument channel extending therethrough, wherein the bipolar electrosurgical instrument and the feed cable are sized to fit within the instrument channel to deliver the RF electromagnetic energy and the microwave electromagnetic energy to the treatment site. 22. The electrosurgical device of claim 21, wherein the maximum available microwave electromagnetic power at the distal end of the instrument channel is equal to or less than 40W.