Determining the condition of blood vessels in the body

Abstract

An intravascular device for determining the condition of a blood vessel in a body comprises an elongated wave-guiding element, such as a wire, and an actuation unit including an ultrasonic energy source for actuating the wave-guiding element and thus transmitting ultrasonic energy to an active distal portion of the wave-guiding element. A signal acquisition system acquires feedback signals from the device for interpreting the condition of the vessel. The signal acquisition system comprises at least one acoustic sensor for acquiring acoustic feedback signals generated by the device when the wave-guiding element is actuated. Data sets can be generated from the acoustic and non-acoustic feedback signals, and a combination of, or a comparison between, the data sets can characterize the condition of the vessel, including any lesions, such as occlusions, in the vessel.

Description

Technical Field

[0001] The present invention relates to a technique for determining the state of blood vessels in the body, including characterizing an occluded portion in such a blood vessel. The present invention particularly relates to elongated elements such as wires and catheters used to pass through or traverse an occluded portion in the body, for example for the purpose of treating ischemia. Thus, such elements are known in this technical field as crossing wires and crossing catheters.

[0002] In this specification, a crossing wire is used to illustrate the concept of the present invention, but it should be understood that the concept of the present invention is also applicable to crossing catheters. It should also be understood that crossing wires and crossing catheters may have additional functions such as guiding subsequent treatment after the occluded portion has been traversed.

[0003] Ischemia is a condition where an organ in the body is not adequately supplied with blood. In atherosclerotic blood vessels, ischemia occurs as a result of the blood vessel being blocked by an occlusion caused by a lesion in the vessel wall, an atherosclerotic plaque, or an embolism resulting from other causes. When the blood vessel is partially or completely occluded, the occluded portion restricts the flow of blood to the distal tissues from there, causing cell death and a rapid deterioration of the health of those tissues.

[0004] Occlusions such as chronic total occlusion (CTO) trigger ischemic responses to wounds and injuries, leading to intractable ulcer formation of wounds and lacerations, as well as other tissue damage. Because of these anticipated reactions, surgical intervention is undesirable. Therefore, the preferred method for treating such occlusions is minimally invasive endovascular procedures, such as angioplasty. In these procedures, a small-bore treatment device is introduced into the vascular structure via a guidewire or catheter, guided through the lumen of the vein and artery to the occlusion, and deployed at the lesion site to restore patency. Procedures used to revascularize coronary and peripheral artery occlusions by treating chronic atherosclerotic plaques can also be used to treat acute embolic occlusions, thrombi, or occlusive blood clots.

[0005] More generally, guidewires or catheters are used in other minimally invasive procedures to introduce other devices and instruments into blood vessels or other cavities within the body to enable examination, diagnosis, and different types of treatment. Other medical procedures that use guidewires or catheters include gastrointestinal, urological, and gynecological procedures, all of which may require the creation of a passage through an occlusion to facilitate the passage of often large devices to the lesion site or other target tissue distal to the lesion.

[0006] In endovascular procedures, an artery is selected and employed to gain access to the vascular structure. This selection is based on the artery's ability to pass the intended diagnostic or therapeutic device to the target site, and to the extent that tissue and patient trauma can be minimized.

[0007] Peripheral artery revascularization procedures often involve surgical incision and puncture of the femoral artery, popliteal artery, and ankle artery, commonly known in medical terminology as the Seldinger procedure. Once access is established, an introducer wire and introducer sheath are inserted into the vessel and secured at the site. This sheath acts as a port for device introduction, withdrawal, and replacement, minimizing arterial tissue dissection. Next, a catheter and guidewire are introduced into the artery to provide further protection and assist in advancing the device to the target site.

[0008] For example, a guidewire is carefully pushed along the lumen of a blood vessel to avoid trauma to the vessel wall and guided to the occlusion site. If the procedure is successful, the guidewire is pushed to the other side of the occlusion site or through the occlusion site and held in place, acting as a guide to track diagnostic or therapeutic devices such as balloon catheters and / or stents to the occlusion site. Visualization of the process by which guidewires, catheters, and other diagnostic or therapeutic devices pass through biological structures is generally performed by X-ray, dual ultrasound, or MRI.

[0009] In balloon angioplasty, a balloon catheter is introduced into the blood vessel along a guidewire and guided to the occluded area. Next, the balloon is inflated to push the occluding material outward and restore blood flow. A stent may also be placed in the lesion as a scaffold to maintain vascular patency. [Background technology]

[0010] Conventional intravascular wires come in a variety of structures and designs to facilitate access to and traverse of lesions in various biostructures and to support various devices. Such wires are available in a variety of outer diameters and lengths depending on the biostructure involved and the expected working distance. These wires are made from a variety of materials, the most common being stainless steel or NiTi (nitinol). Their manufacture typically involves cold working the material to form the wire, and then machining or grinding the wire into various shapes to achieve the desired performance. For example, a specific taper can be ground along the length of the wire to create different degrees of flexibility along its length.

[0011] The wire must have sufficient flexibility to conform to the tortuousness of the blood vessel, especially at its distal end, and must also have sufficient axial and torsional strength to transmit force to the distal tip and pass through the lesion. A balance is required between flexibility, expressed as "trackability," and rigidity, expressed as "pushability" or "steering ability." Pushability requires longitudinal cylindrical rigidity, while steering ability requires torsional rigidity.

[0012] Conventional endovascular wires are guided to the occlusion by being manipulated by pushing, pulling, or applying torque to their proximal end, and then pushed out through the occlusion. Therefore, conventional endovascular wires are passive in the sense that they do not transmit any energy other than that applied by the clinician.

[0013] The biological structures in which endovascular procedures can be performed include, but are not limited to, the coronary arteries, neurovascular arteries, and peripheral arteries acting on the lower extremities. Different biological structures are associated with different types of lesions. For example, lesions in various peripheral blood vessels present different challenges than those in the coronary arteries.

[0014] In many cases, occlusions are difficult to traverse with conventional endovascular elements such as guidewires. In this regard, atherosclerotic plaques are composed of material that gradually hardens over time. For example, the iliac, femoral, popliteal, and infrapopliteal arteries are susceptible to extensive calcification, which significantly impedes the success of endovascular procedures. Conventional endovascular elements are limited when attempting to traverse occlusions that are nearly or completely blocked and may also be significantly calcified.

[0015] For example, in a peripheral infra-iliac procedure, the occlusion may have a calcified proximal cap encountered in a preferred antegrade or femoral approach. A considerable amount of time may be spent attempting a conventional antegrade approach to traverse the lesion, and then escalating through different wires within the antegrade approach before switching to a retrograde approach. In a retrograde procedure, access to the lesion in the foot or ankle in the case of peripheral disease is obtained through distal vessels or through collateral (typically septal) vessels in the biotissue of the coronary arteries. In this respect, a retrograde procedure utilizes an occlusion that may have a softer distal cap that is easier to traverse than a calcified proximal cap. However, retrograde procedures are more complex, require higher skill, and take much longer to perform than antegrade procedures.

[0016] In more than 50% of peripheral artery cases, particularly in the popliteal, tibial, and peroneal arteries, the vessels are completely occluded by the lesion. In approximately 30% of cases, the target lesion is severely calcified. These calcified lesions actually consist of rigid, inelastic segments, usually 3-5 cm long, within longer, more extensive diffuse lesions on the order of 20-25 cm in average length. Selecting the appropriate treatment for such lesions requires insights into the length and composition of the lesions, which are not readily available through conventional imaging studies.

[0017] In peripheral arteries, occlusions are often severe or composed of highly resistant materials that prevent guidewires from easily passing through. In such cases, the procedure can take a considerable amount of time, and additional devices may be needed to traverse the lesion. In very many cases, the procedure is ultimately abandoned entirely, which prevents desirable subsequent procedures such as balloon angioplasty and stent placement, thus limiting the ability to treat the patient.

[0018] In view of these drawbacks, several ultrasound-activated guidewires and catheters have been proposed for use in atherectomy or thrombectomy, in which ultrasonic vibrations are transmitted along the element to the distal tip, stirring and excising the material at the occlusion. Thus, the element functions as a waveguide for transmitting ultrasonic energy distally. Much of the prior art related to the concept of ultrasound-activated technology in this context is described in the inventors' previous patent applications published as International Publication Nos. 2020 / 094747, 2021 / 089847, 2021 / 089859, and 2021 / 224357, the contents of which are incorporated herein by reference.

[0019] In a previous patent application of the inventors, published as International Publication No. 2020 / 094747, a system comprising, among other concepts, an ultrasonic source, an active transverse wire, and a signal acquisition, processing, and communication chipset or control circuit is disclosed. The chipset or circuit can generate signals for controlling the system and can provide outputs to the user and / or an external data acquisition system. In particular, the controller monitors the frequency and amplitude of the current and voltage in the ultrasonic source, as well as measured values ​​of the incident, reflected, and steady waveforms in the wire, thereby estimating the displacement of the distal tip. Modulation of these variables is monitored as the wire passes through biological structures and through various types of occlusions, including calcified CTOs. This makes it possible to determine whether a lesion is calcified or non-calcified, and to determine the duration or length of the calcified segment of the lesion. When a lesion determined to be calcified is encountered, the user can respond by controlling the system, for example by increasing the input power, or the system can self-control accordingly.

[0020] In International Publication No. 2020 / 094747, a digital signal processor is proposed to examine the generated measurements, provide feedback, and interpret and compare the relative contributions of losses due to anatomical tortuosity during guidance to the site and losses occurring when passing through the occlusion. The system processes data obtained from measurements that show the ultrasound waveform as resonant vibration transformations occur while passing through the vascular structure and through the occlusion. An algorithm converts the raw data into output relevant to the procedure. The system can compare and interpret the difference between calculated values ​​from an active system and a predetermined set of values ​​to characterize the properties of the material occluding the vessel.

[0021] Thus, the system of International Publication No. 2020 / 094747 takes into account typical characteristic loss variations when the active wire engages with various healthy and diseased tissue types. Distinctions are made between vascular loss and loss associated with lesions, and between lesions of different compositions, particularly between calcified and non-calcified lesions. Using characteristic responses to differential changes occurring in different media and as the intravascular wire passes through or is guided through different biostructures, individual algorithms are created to be used for 1) determining and compensating for the causes of loss in the system, 2) evaluating the tone of arterial vessels, and 3) determining the compositional details of lesions. These algorithms can, for example, provide compensation to the wire tip when it comes into contact with compliant, non-compliant, and calcified materials, and in the latter case, amplify the energy input to the system accordingly. [Prior art documents] [Patent Documents]

[0022] [Patent Document 1] International Publication No. 2020 / 094747 [Patent Document 2] International Publication No. 2021 / 089847 [Patent Document 3] International Publication No. 2021 / 089859 [Patent Document 4] International Publication No. 2021 / 224357 [Overview of the project] [Problems that the invention aims to solve]

[0023] The present invention starts from WO 2020 / 094747. The present invention aims to improve the quality of feedback regarding the behavior of an elongated waveguide element, such as a wire, actuated by ultrasound as it traverses and interacts with a biological structure and any occlusions or other lesions encountered within the biological structure. In this regard, when operated in situ, the element has been found to generate a characteristic acoustic signature indicative of various properties characterizing the lesion, the tissue of the blood vessel, and in some cases the blood flow along the blood vessel.

Means for Solving the Problem

[0024] Therefore, the present invention pertains to an intravascular device for determining the state of a blood vessel within a body, including any lesions within the blood vessel. The device comprises an elongated waveguide element, an ultrasonic energy source, a coupling section for coupling the ultrasonic energy source to the waveguide element to actuate the waveguide element, thereby transmitting ultrasonic energy from the ultrasonic energy source along the waveguide element to the active distal portion of the waveguide element, and an operating unit including the coupling section, and a signal acquisition system configured to obtain a feedback signal from the device for use in interpreting the state of the blood vessel. The signal acquisition system comprises at least one acoustic sensor for acquiring an acoustic feedback signal generated by the device when the waveguide element is operating.At least two acoustic sensors can be arranged at intervals along the longitudinal direction with respect to each other.

[0025] At least one acoustic sensor can be attached within or on the operating unit, for example, longitudinally aligned with the coupling section of the operating unit, or proximally or distally with respect to the coupling section of the operating unit. At least one acoustic sensor can be attached on or parallel to the waveguide element, for example, proximally or distally with respect to the length of the waveguide element.

[0026] The waveguide element may be a catheter, comprised of a catheter, or surrounded by a catheter, in which case at least one acoustic sensor can be attached to the catheter. In addition to or instead of this, the waveguide element may be a wire, comprised of a wire, in which case at least one acoustic sensor can be attached to the wire. A strain gauge can be fixed to the waveguide element, such as a wire, to obtain an operational feedback signal from the waveguide element. Such a strain gauge can function as an acoustic sensor.

[0027] At least one acoustic sensor may be an external sensor positioned to strike a part of the body, or an internal sensor positioned to be inserted into the body.

[0028] In a preferred embodiment, the signal acquisition system further comprises at least one electronic sensor configured to acquire an operating feedback signal representing the operating parameters of an ultrasonic energy source. These operating parameters may be the frequency and / or amplitude and / or phase of the current drawn in by the ultrasonic energy source, or the voltage drop across the ends of the ultrasonic energy source. The signal acquisition system may be configured to monitor fluctuations in the frequency or amplitude of vibrations of the waveguide element through the coupling.

[0029] The device may further include a signal processing system for processing feedback signals acquired by a signal acquisition system. Such a signal processing system may be configured to employ, for example, a numerical algorithm selected for a particular type of waveguide element.

[0030] The signal processing system can be configured to determine the characteristics of intravascular occlusion from the acquired feedback signal. The signal processing system can also be configured to compare the relative contribution of the loss due to anatomical tortuosity in guiding the active distal portion to occlusion with the loss resulting from the active distal portion passing through the occlusion.

[0031] The signal processing system can be configured to compare the acquired feedback signal with stored data that characterizes known blockages, and to characterize the blockage by referring to that comparison.

[0032] The signal processing system may further include outputs to a user interface and / or outputs to an external data acquisition system and / or inputs from the user interface and / or inputs from an external data network.

[0033] The device may further include a controller that responds to the signal processing system. Such a controller may be configured to modulate the excitation voltage applied to the ultrasonic energy source, or the excitation current supplied to the ultrasonic energy source. In particular, the controller may be configured to control the ultrasonic energy source by changing the frequency and / or amplitude of the excitation voltage applied to the ultrasonic energy source. Alternatively, the controller may be configured to drive the frequency of the excitation voltage by using the phase difference between the excitation voltage and the excitation current, in conjunction with the amplitude of the excitation voltage.

[0034] The controller may include an amplitude feedback controller and may be configured to use the resonant frequency as the operating point for control. The controller may be configured to pulse or vary the drive signal to the ultrasonic energy source.

[0035] The controller can be configured to monitor the modulation of the transmitted signal and automatically control the ultrasonic energy source to compensate for background energy loss occurring within the waveguide element as the active distal portion approaches the occlusion, and to distinguish between background energy loss and additional energy loss as the active distal portion passes through the occlusion, and to compensate for background energy loss to maintain the displacement in the active distal portion.

[0036] The controller can be configured to modify or change the control algorithm in response to variations in the operating parameters of the ultrasonic energy source resulting from the interaction between the active distal portion and the occlusion during use.

[0037] The concept of the present invention encompasses a communication system comprising the device of the present invention that communicates data with a computer system configured to receive data from the device, optimize and update a control algorithm accordingly, and output the optimized and updated control algorithm to the device. Optimally, two or more such devices communicate data with the computer system, and the computer system is configured to optimize a control algorithm according to data received from a plurality of actions performed using the device, and to output the optimized and updated control algorithm to the device.

[0038] The concept of the present invention also encompasses a corresponding method for determining the condition of blood vessels within the body. This method includes guiding the distal end of an elongated waveguide element to a site within a blood vessel, activating the waveguide element by transmitting ultrasonic energy to the distal end, acquiring an acoustic feedback signal generated while the waveguide element is activated, and interpreting the acoustic feedback signal to characterize the condition of the blood vessel.

[0039] The method of the present invention can evaluate the attenuation of the amplitude of the displacement of a waveguide element or the frequency shift caused by losses resulting from contact with intravascular substances such as the wall of a blood vessel or an occlusive lesion.

[0040] The distal portion of the activated waveguide element can be engaged with a lesion in a blood vessel, and the resulting changes in the acoustic feedback signal can be interpreted to characterize the lesion. Conveniently, the distal portion of the activated waveguide element can also destroy the lesion.

[0041] This method may further include comparing sensed data representing the response of the activated waveguide element to a lesion with stored data representing the corresponding response of the activated waveguide element to an interaction with a known lesion.

[0042] Acoustic feedback signals can be acquired in an external operating unit located proximal to the waveguide element, and / or at one or more locations along the waveguide element, and / or at distal locations inside the body along the waveguide element, and / or at one or more locations outside the blood vessel, and / or at two or more locations spaced longitudinally apart from each other.

[0043] Preferably, the method further includes obtaining a non-acoustic feedback signal representing the operating parameters of an ultrasonic energy source coupled to a waveguide element, or more generally, obtaining a non-acoustic feedback signal obtained by monitoring fluctuations in the frequency or amplitude of the vibration of the waveguide element. How the ultrasonic energy source responds when the waveguide element encounters a blood vessel and any lesion within the blood vessel can be determined from the operating parameters. For example, the non-acoustic feedback signal may represent fluctuations in the frequency and / or amplitude and / or phase of the current drawn in by the ultrasonic energy source, or the voltage dropping across the ends of the ultrasonic energy source. Conveniently, the attenuation of the waveguide element can be determined by monitoring the attenuation of the current signal over time.

[0044] Datasets can be generated from acoustic and non-acoustic feedback signals, and the state of blood vessels can be characterized using combinations of these datasets or comparisons between them. The amplitude or frequency of the ultrasonic energy transmitted distally along the waveguide element can be adjusted in response to the non-acoustic feedback signal. Furthermore, the ultrasonic energy source can be controlled in response to the non-acoustic feedback signal to maintain the resonant frequency within the waveguide element.

[0045] The method of the present invention may include outputting data to an external data network, receiving data from the network in response, and modifying or changing the control algorithm accordingly upon receiving data from the network. The method may also include outputting data to an external computer system, optimizing and updating the control algorithm in the external computer system according to that data, outputting the optimized and updated control algorithm from the external computer system, and controlling the operation of the waveguide element using the optimized and updated control algorithm. Preferably, the computer system can optimize the control algorithm according to data received from a plurality of procedures.

[0046] Two or more different waveforms can be continuously applied to the ultrasonic energy source, and these waveforms can be selected from, for example, sinusoidal waveforms, pulsed waveforms, multitone waveforms, chirp waveforms, or noise waveforms.

[0047] To improve sensitivity, the method may include advancing the distal end of the activated waveguide element closer to the lesion in the blood vessel, acquiring a baseline feedback signal, advancing the distal end of the activated waveguide element to engage with the lesion, acquiring an action feedback signal, and subtracting the baseline feedback signal from the action feedback signal.

[0048] In summary, the present invention involves acoustically characterizing the effects of intraluminal elements such as ultrasonically operated wires. In particular, the present invention employs ultrasonic guided devices such as transverse wires not only for excavating lesions and destroying calcified intraluminal or intramural plaques within blood vessels, but also for characterizing vascular lumens. These characteristics may include the inner diameter of the blood vessel, the vascular tension of the blood vessel, and the mechanical characteristics and composition of any material blocking the blood vessel.

[0049] In International Publication No. 2020 / 094747, the inventors proposed that different wires having known features, such as a ground tapered shape, specific combinations of land length and diameter, respond to lesions in a manner that can distinguish between calcifying and non-calcifying lesions. The inventors determined that by further analyzing and processing the spectra, a more sensitive assessment of the lesion and / or other surfaces that the wire may come into contact with within the vascular structure can be provided. More specifically, the invention aims to enable the assessment of the inner diameter of a blood vessel and to characterize the mechanical properties of the vascular wall and any material that may be occluding the vessel by interpolation. Thus, the invention makes it possible to identify whether the occlusion consists of gelatinous plaque, calcified material, thrombus, or any other form of embolic material. Of particular interest is determining whether the occlusion is a fragile soft plaque or calcified plaque, or, if the occlusion is a thrombus, characterizing what type of thrombus is present.

[0050] In the examples described, the system of the present invention comprises a wire manufactured with a specific grinding profile toward its distal end, and having a longitudinally continuous portion having a specific diameter and length. Examples of such wire features are taught in the inventors' aforementioned prior patent applications. These features allow the distal end portion of the wire to actuate in a specific manner at the resonant frequency (and harmonic frequencies associated with or matching the resonant frequency) of a piezoelectric ultrasonic transducer acting on the wire.

[0051] The coupling mechanism allows the wire to be coupled to the transducer. The transducer is driven by an ultrasonic signal generator that can excite the transducer and therefore the wire at a desired frequency and amplitude. The control circuit monitors and controls the electrical load between the ends of the transducer to produce the desired operation.

[0052] According to the present invention, at least one acoustic sensor detects and substantially listens to acoustic radiation from wires, couplers, and / or transducers. The system can monitor and analyze the detected acoustic spectrum and present the processed information to the user in a meaningful manner. The acoustic information can be used in combination with other information, such as inputs to or outputs from control circuits, to improve the quality of analysis, detection, and decision-making. The processed information can also be stored in an external database, such as a cloud, and shared from there, which is more preferable to educate physicians and to further refine the analysis algorithms, along with an increasing number of samples representing the use of the present invention in actual procedures.

[0053] This invention utilizes the insight that a means of interpreting tissue characteristics can be provided by interpreting the acoustic spectrum emitted while a vibrating wire or other waveguide passes through a vascular structure. This is possible because when the wire is forced into contact with any surface, such as the inner surface of a blood vessel or a lesion blocking the vessel, the contact modulates the frequency and / or amplitude of the acoustic waveform traveling through the wire. These modulations can be associated with specific characteristics of the biostructure of the blood vessel. Furthermore, at such high ultrasonic frequencies, interaction with the blood vessel wall can break down calcified material within the wall, thus allowing for the assessment of vascular stiffness while simultaneously softening plaque.

[0054] Furthermore, by examining the acoustic spectrum alone, and / or other inputs from the environment, it is possible to interpret from the deformation of the wire what structures or materials it may come into contact with as it passes through the internal morphology of the vascular lumen. This includes any occlusions that may exist within the lumen, or, if the wire is excavating or removing such occlusions, the features of those occlusions.

[0055] The rationale for such an evaluation is that the amplitude of axial or radial displacement associated with resonance in the system changes with the input amplitude, and its attenuation or frequency displacement is related to the loss caused by the wire coming into contact with other materials or surfaces at its ends or along its length. These changes in acoustics detected along the wire can be used to characterize blood vessels, their lumen, and occlusions. Furthermore, the impedance of the transducer can also be modulated as a result of the changes in losses in the system as the wire is attenuated or more or less constrained, so the superposition of these electrical responses can be used to more accurately analyze and describe the characteristics of blood vessels, their lumen, and any occlusions.

[0056] To detect emitted sound and subtract ambient noise, one or more acoustic sensors can be placed, for example, on, inside, or near the transducer housing, or on a wire, or on a catheter, or inside or in contact with the patient's body. The resulting acoustic spectrum is processed and analyzed by an algorithm that recognizes specific types of interference and acoustic spectra characteristic of resonant and harmonic frequencies. As described above, the sensitivity of the acoustic algorithm can be improved by examining variations in the electrical signal used to drive the transducer at its resonant frequency.

[0057] The system compares the acoustic spectrum with the ultrasonic spectrum within a device employing an intravascular waveguide, such as a wire, which resonates at frequencies and amplitudes that allow the distal end of the wire to resonate with axial and radial displacement. In the case of a transverse wire, the primary purpose of axial and radial displacement is to excavate material occluding the blood vessel. In this invention, these displacements are used for another or additional purpose, namely to generate acoustic signals that vary as they move through the vascular structure and encounter and engage with lesions. The acoustic signals also vary in different ways when engaging with different types of lesions and thus function as acoustic signatures characterizing the lesions.

[0058] As described in the inventors' previous patent application mentioned above, the dimensions and profile of the transverse wire allow the wire to resonate at harmonic and subharmonic frequencies in various displacement modes, particularly at its distal end. Modulation occurs when the wire comes into contact with various surfaces. For example, when the distal end of the wire encounters a calcified occlusion that suppresses its lateral displacement, the displacement mode of the wire transitions from "fixed-free" to "fixed-fixed". "Fixed-free" can be visualized as a wave node at the proximal end of the wire and a wave antinode at the distal end of the wire, while "fixed-fixed" can be visualized as a wave node at both the proximal and distal ends. This modulation slightly shifts the wavelength, thus changing the acoustic signal transmitted by the wire.

[0059] The system can detect what type of substance disrupted its wavelength and frequency by analyzing changes in wavelength, and thus determine the type of substance in contact with the distal end of the wire. In this way, interpreting the acoustic spectrum emitted as the waveguide passes through the vascular structure provides a means to interpret the characteristics of the tissue in contact with the wire. Furthermore, the acoustic spectrum or electrical signal characteristics indicating how the wire responds to the internal morphology of the lumen when removing an occlusion in a blood vessel can be interpolated by mathematical transformation.

[0060] Because the system is dynamic, the characterization of the mode in which the system responds must be dynamic in order to be faithful to the comparison between electronic control and acoustically emitted variables. Dynamic investigation and subtraction of features, or addition in the case of patterned excitations, must be monitored in a timely manner. In this regard, feedback can be examined from compared programmed inputs, such as pulses or patterns, to determine variations in specific features. Feedback can also be examined from compared temporal variations, such as quality factors or Q values ​​representing decay.

[0061] Therefore, the present invention embodies the principle of acoustic characterization and proposes that an active element, such as a wire in situ within a blood vessel, generates characteristic acoustics when it comes into contact with the vessel wall and an occlusion of either a thrombus (soft or fibrous) or an atherosclerotic lesion (hard or soft) within the lumen or vessel wall. The captured acoustic signature is characteristic of the vascular lumen and surrounding tissue. We propose that direct comparative measurements, interpolated or extrapolated, can be used with post-processing analysis and appropriate algorithms to generate reliable diagnostic output relating these characteristic acoustic spectra to the nature and integrity of the tissue.

[0062] In a preferred embodiment of the present invention, two sensors that operate simultaneously are employed, namely an electrical or electronic sensor and an acoustic sensor.

[0063] The electronic sensor acts on features such as transducers that generate ultrasonic energy, determining how the transducer is operating and setting the range of its ability to sense and generate data that can be investigated. The electronic sensor also detects the electrically driven frequency and the manner in which the system responds to variability or instability caused by a wire moving through a meandering blood vessel to a lesion. The electrically driven frequency is modulated by encountering occlusions in the vessel wall and lumen. The driver electronic circuit responds to this modulation by tracking variables of phase angle, current, and / or voltage. This invention aims to investigate this dynamic control variation in key variables in order to provide characteristic features that can be associated with the physical features of the blood vessel and any occlusion within the vessel.

[0064] One or more acoustic sensors or microphones listen to all or part of the acoustic radiation passing through and from biological tissue when an active wire is in a living body, whether intravascular, intraluminal, or extravascular. The acoustic sensors, in particular, listen to acoustic radiation from a wire operating internally within the lumen of a blood vessel. This invention makes it possible to investigate variations in acoustic radiation affected by interference between the wire and any intravascular object, such as a vascular tissue ostomy or cytotoxic ostomy (CTO).

[0065] Datasets from acoustic sensors are far richer than those from the small range of operating frequencies used to activate the wire (even though acoustic radiation is generated by that small operating range). As a result, a vast amount of additional data is obtained, which can be mined and features extracted using various mathematical methods, and these features can be correlated with the properties of blood vessels and their contents, the behavior of the wire, and the properties of the new channels drilled by the use of the wire. In this way, integrating acoustic data can greatly enhance electronic datasets.

[0066] Examining the entire range and spectrum of various frequencies being expressed requires considerable post-processing and evaluation; therefore, a cloud-based machine learning approach is preferable for the operation, development, and updating of advanced algorithms. However, if a properly programmed onboard processor is available on a local device, it will be possible to manipulate the data with appropriate algorithms and provide at least "binary" feedback, such as whether the lesion is calcified or non-calcified, or hard or soft. It should be emphasized that no form of post-processing is a requirement, whether cloud-based or not. Such processing may be performed locally in real time.

[0067] Therefore, disclosed is an ultrasound system that induces vibrations in a customized endovascular surgical wire device and applies artificial intelligence, examining acoustic feedback and optionally other feedback within the system. This feedback can be used to optimize the system's performance when guiding to an endovascular occlusion, when traversing an endovascular occlusion, and when characterizing and modifying the structure and characteristics of the endovascular occlusion.

[0068] A programmable circuit system for acquiring and processing data and for controlling system operation may include an integrated or onboard programmable digital signal processing chipset. This chipset processes monitored, transmitted and received, or input acoustic and / or electrical or electronic signals using algorithms for examining responses, comparing the effects of ultrasonic feedback and resonant frequency standing waves, estimating the size of the opening through which an activated tip penetrates a lesion, and modulating the system power via voltage amplitude and system frequency.

[0069] Analog and digital signal analysis and power control of the device, along with a communication module, enable wired and wireless connectivity of the device and its data to a wider data network and the internet. This, for example, can facilitate the development of more intelligent algorithms for managing the system.

[0070] When ultrasonic vibrations are transmitted through a transmitting member acting as a waveguide, the distal tip of the transmitting member vibrates at a predetermined frequency and amplitude that has the ability to favorably destroy lesional tissue or other material. Digital signal processing and control circuits respond to acoustic and other feedback to enable semi-autonomous holistic characterization of the lesion, power control, and estimation of the size of the opening in the system.

[0071] When an ultrasonic system is activated, the emitted waves travel along the wire to its distal end, where they are either reflected or transmitted to nearby materials. Reverberations occurring in the wire at various transition points establish a series of secondary and tertiary reflections. These waves are characteristic of different wire designs and features and can be optimized to highlight differences in signal characteristics. Reflections are determined to consist of specific waveform response patterns for any given input, and their variations are associated with perturbations or differences in the surrounding environment. The waveforms produce characteristic acoustic emissions that can be used alone or in conjunction with other feedback signals.

[0072] The amplitude of displacement along the wire at specific frequencies changes during the procedure as it is guided to the lesion site, or when it is in contact with lesional tissue, non-conforming tissue, or calcified tissue at the lesion, as a result of attenuation due to contact with surrounding tissue. Reverberation within the system and the resulting acoustic radiation are similarly affected in a characteristic manner and can be used to characterize the cause and nature of the attenuation.

[0073] To produce a constant vibration amplitude, the ultrasonic transducer is controlled by an appropriate feedback controller. In the case of ultrasonic waveforms, phase feedback control and comparison can be performed using electrical equivalence models such as the Butterworth-vanDyke model.

[0074] An ultrasonic transducer can be controlled by the frequency and amplitude of the excitation voltage. Changing the frequency can affect the phase between the voltage and current. The amplitude of the excitation voltage controlling the current is proportional to the vibration amplitude at resonance. This allows the control algorithm to drive the frequency using only phase and amplitude.

[0075] In a preferred embodiment, the approach, in combination with an amplitude feedback controller, drives the system using the resonant frequency as the control operating point and manages this operation using a customized program control algorithm specific to each wire type.

[0076] The advantage of a resonant drive system with low damping is that it requires a low voltage and has a high effective power value. This solution also offers advantages in controlling the response of nitinol wire to ultrasonic action.

[0077] Temperature effects in nitinol, as well as changes in loading conditions during treatment due to interactions with surrounding tissue, may alter the resonant frequency and vibration amplitude, but these can be compensated for within a given range by a given transducer.

[0078] Thus, with regard to the use of voltage and current, differential changes over time and length can be monitored using control and analysis through resonant frequencies, and this investigation and correction can be used to characterize the properties of intravascular biostructures. The ability to capture acoustic radiation from the interaction between the system and adjacent tissues provides an additional distinct means of inferring or characterizing the properties of tissue, since the tissue's response to interaction with the wire is determined by the structural properties of the tissue.

[0079] The comparison and analysis of primary emission signals and tertiary feedback responses in wires considers typical characteristic loss variations when the active component engages different tissue types, such as healthy and diseased tissue. These types of losses within blood vessels are distinguished from losses associated with lesions of different compositions (e.g., calcified and non-calcified lesions).

[0080] The resistive loads encountered and the acoustic radiation recorded by the system vary. As the active components pass through various biological structures, analog signals are examined and adjusted by an onboard digital signal processor, and parametric outputs are processed by algorithms and added to data from acoustic feedback to characterize the response, define the feedback, and control it.

[0081] The algorithm may be customized to suit the wire type. The algorithm can characterize the properties of the material through which the wire passes, using the range of change, rate of change, and derivative order of the change, filtered by a signal processing circuit. This can be communicated to the physician during the procedure to help determine the appropriate treatment.

[0082] To improve performance, the algorithm can be trained with benchmark ex-vivo and in-vivo data. The latter possibility is made possible by a communication model that provides data transfer to and from the device. The system can enable wired or wireless communication of data between the device and another device or cloud service for analysis and storage.

[0083] Therefore, the quality of device operation and interpretation can be improved over time by interpolating more data sets from additional procedures built upon user experience. Such data can inform the design of iterative generation of control and interpretation algorithms. As a result, onboard, local, and / or cloud-based improvements to the algorithms can improve the design and operating interface of therapeutic devices, allowing for customized device operation to suit various wire shapes and biostructures, as well as providing more detailed feedback to physicians using the devices.

[0084] The frequency at which the transducer generates the mechanical signal may be a set short-range frequency sweep over a short frequency range to accommodate losses from interactions and collisions due to various forces along the length of the wire. The speed of the microprocessor allows the device to process small fluctuations in resonance in real time.

[0085] The signal used to drive the ultrasonic generator can be pulsed or modified to reduce heating and optimize the analysis and matching of offsets at the resonant frequency. For example, pulse modulation of a voltage over a small frequency range can actuate a transverse wire, and a digital signal processor unit can examine the measurements taken, provide feedback, and interpret and compare the relative contributions of losses from anatomical meandering during guidance to the site and losses resulting from passing through the occlusion.

[0086] The present invention employs a method of examining feedback signals to collect data about the traversed lesion, such as its length and composition, which are facets that characterize the blood vessel or lesion being traversed by the wire and indicate how the target lesion can be treated by the physician. This data may also be provided to the physician as feedback in tactile and / or visual and / or audible formats on a display to assist the physician in operating the device. For example, this feedback allows the physician to monitor the traversing procedure while displaying and evaluating the characteristics of the lesion using a simple backlit screen on a small operating unit.

[0087] In another embodiment, if the user has access to a network, data from the procedure may be captured anonymously to protect patient confidentiality and transmitted from the device to a data storage and processing platform where it can be analyzed in real time or later. Lesion characterization may also be presented to the user so that it can be analyzed and interpreted while the procedure is being performed.

[0088] Using an attachment, the displacement of the wire as it traverses the vascular structure can be recorded and measured, and this data can be mapped to the lesion composition from the feedback to characterize the characteristics of the lesion as a function of displacement through the lesion.

[0089] The characteristic capacitance of the transducer, along with the resulting variations in the magnitude of current, voltage, and frequency input and control parameters, provides a measurement and control matrix that can be used in conjunction with acoustic feedback to determine power and characterize the lesion being traversed.

[0090] Monitoring acoustic emissions and electronic responses such as currents can support the interpretation of lesions, and modulating the voltage allows for power amplification and frequency recovery as the device activates the contact surface to reduce offset. A series of measurements in such a small frequency range can characterize the overall composition of the lesion, such as calcification, fibrous, or gelatinous, over the entire or partial length of the lesion. These interpolated characteristic components do not represent the absolute characteristics of the lesion, but rather indicate the composition, degree of calcification, and whether the lesion is hard, compressed, or deaggregated. This indicates the nature of the lesion and can inform the physician of the best treatment to consider. This can, for example, help determine whether the composition or viscosity of the lesion is compressed calcified particles, uncompressed fibrous, or hard or soft gelatinous.

[0091] By employing a specific algorithm for each standard wire type, it is possible to estimate the diameter mapped out by various levels of frequency and power, as well as the displacement of the distal tip when excited in the device configuration, under the conditions relevant to the procedure. This provides an estimate of the diameter of the resulting tunnel-like channel through the occlusion.

[0092] The system can process data obtained from ultrasonic waveform measurements when the ultrasonic waveform is generated, when the waveform passes through a wire or other transmission member, when resonant vibration conversion occurs, and when the reflected waveform is attenuated by the transmission member while passing through vascular structures and occlusions.

[0093] By monitoring and analyzing the modulation of the transmitted signal, energy losses within the system can be automatically adjusted through voltage control to increase the system's power and compensate for energy losses occurring within the wire as it passes through the vascular structure to the occlusion. Furthermore, by monitoring and analyzing the modulation of the transmitted signal, these losses can be distinguished from additional losses that occur as the wire passes through the occlusion, and these additional losses can be compensated for in order to maintain displacement at the distal end.

[0094] The measured parameters and variables can be numerically manipulated to determine their rates of change relative to each other and to other parameters. By comparing these calculated values ​​from the active system with the differences between a given set of values ​​and interpreting them numerically, the properties of the substance occluding the blood vessel can be characterized. [Brief explanation of the drawing]

[0095] To make the present invention easier to understand, please refer to the attached drawings as an example. [Figure 1] This is a perspective view of an apparatus for carrying out the present invention. [Figure 2] This is a schematic side view of the transverse wire of this device during operation. [Figure 3a] These represent the first, second, third, and fourth harmonic waveforms, with the wavelengths of the second, third, and fourth waveforms being half the wavelength of the preceding waveform. [Figure 3b] This shows the fundamental composite waveform generated from the harmonic waveforms in Figure 3a. [Figure 4] This is a detailed side view of the active wire of this device, which protrudes distally from the catheter. [Figure 5] This is a series of diagrams showing the wires in operation, which are excavating a tunnel through a lesion that was blocking a blood vessel. [Figure 6] This is a series of diagrams showing the active wires that excavate tunnels into lesions. [Figure 7] This is a series of diagrams showing the active wires that excavate tunnels into lesions. [Figure 8] This is a series of diagrams showing the active wires that excavate tunnels into lesions. [Figure 9] This is a graph of acoustic signals over time, showing the response of the active wire when it encounters a calcium sample representing a lesion. [Figure 10] This is a block diagram of an embodiment of the present invention. [Figure 11] This is a block diagram of another embodiment of the present invention. [Figure 12] Figure 1 shows typical oscilloscope images of the voltage and current waveforms applied to the transducer of the device shown. [Figure 13] This is a side view of the longitudinal cross-section of the transverse wire and catheter connected to the operating unit, showing the possible locations of acoustic sensors within the operating unit. [Figure 14] This is a side view of the transverse wire and catheter connected to the operating unit, showing the possible locations of acoustic sensors on the catheter. [Figure 15] This is a perspective view of a catheter including a transverse wire, showing the possible locations of acoustic sensors on the catheter. [Figure 16] This is a perspective view of the transverse wire, showing the possible locations of acoustic sensors on the wire. [Figure 17] This is a schematic cross-sectional view of the patient's leg, showing the acoustic sensor of the present invention incorporated into an adhesive patch attached to the leg at a location close to the lesion site of the patient's vascular structure. [Figure 18] This corresponds to Figure 17, but instead of an adhesive patch, it shows an acoustic sensor unit that is attached to the leg and held in place at a position close to the lesion. [Figure 19] This corresponds to Figure 18, and shows an acoustic sensor in the form of a handheld scanner that sweeps the leg at a position close to the lesion. [Figure 20] This is a schematic lateral view of a patient's leg, showing the acoustic sensor of the present invention embedded subcutaneously in the leg. [Figure 21]This is a schematic cross-sectional view corresponding to Figure 19, showing one of the acoustic sensors implanted near the lesion site in the patient's vascular structure. [Figure 22] This shows the acoustic signals emitted in the frequency range up to 125 kHz as the active wire crosses the chalk sample. [Figure 23] This corresponds to Figure 22, but focuses on the range up to 10 kHz. [Figure 24] The image shows the acoustic signals emitted in the frequency range up to 125 kHz as the active wire crosses a sample of BegoStone gypsum. [Figure 25] This corresponds to Figure 24, but focuses on the range up to 10 kHz. [Figure 26] The image shows the emitted acoustic signal in a frequency range up to 125 kHz when the active wire is not crossing the sample, but is instead active in water. [Figure 27] This corresponds to Figure 26, but focuses on the range up to 10 kHz. [Modes for carrying out the invention]

[0096] Figure 1 of the drawings shows the overall configuration of a system for carrying out the present invention and illustrates some of the main components of such a system. This example features a handheld ultrasonic actuator unit 2 through which a flexible transmission member in the form of an intravascular waveguide or wire 4 extends, aligned to the center. In this example, a portion of the wire 4 extends both proximal and distal from the actuator unit 2. This arrangement is advantageous for various reasons, as described in the inventors' previous patent application, but is described here for illustrative purposes only and not to limit the present invention. The present invention can be advantageously used in combination with more conventional, actuated transverse elements, which may extend only distally from the ultrasonic actuator, for example.

[0097] Wire 4 is inserted into the patient's vascular structure and can be traversed to move its distal end to the location of the lesion. When a complex lesion that resists traversal is encountered by wire 4, or even before, the actuation unit 2 can be coupled to wire 4 at an appropriate longitudinal position. When actuated, the actuation unit 2 transmits ultrasonic vibrations to and along wire 4, enhancing wire 4's ability to traverse the lesion via ablation and other mechanisms. This allows wire 4 to remain in situ, functioning as a traversing wire to pass through the occlusion within the vessel and then as a guide wire to deliver subsequent therapeutic devices to treat the lesion.

[0098] Generally, the length of the wire 4 can be longer than 2m, up to a maximum of 3m. For example, access to a lesion in or through the foot may involve the wire traveling a distance of typically 1200mm to 2000mm within the vascular structure, depending on whether an ipsilateral, contralateral, or radial approach is chosen. In this regard, the wire 4, which tapers distally to become a thinner wire at its tip, can be guided into the foot arteries and around the arch of the foot between the dorsal and plantar arteries. However, the present invention is not limited to the subinguinal or peripheral vessels of the foot, and can also be used in coronary artery applications, for example, where the ability of the wire 4 to advance and excavate within tortuous small-diameter arteries is also beneficial.

[0099] The actuation unit 2 may include a user control unit 6 and optionally a display. The actuation unit 2 further comprises a distal hand toggle 8 that the user can rotate around the central longitudinal axis of the unit 2 and the wire 4. In particular, the actuation unit 2 can slide along the wire 4 and can be coupled to the wire 4 at multiple longitudinally spaced positions by applying torque to rotate the toggle 8.

[0100] To perform the coupling, as shown in later drawings, the toggle 8 surrounds the wire 4 and acts on a collet in the actuation unit 2 that is coaxial with the wire 4. When the toggle 8 is tightened, the collet grips the wire 4 and transmits ultrasonic energy from the integrated ultrasonic transducer in the actuation unit 2 through an amplifier horn optionally coupled to the transducer. In some embodiments, the wire 4 may be directly coupled to the transducer, in which case the horn may be omitted.

[0101] The toggle 8 can be reversed to release the actuation unit 2 from the wire 4. This allows for the replacement of the wire 4 with different dimensions, configurations, or materials for different purposes. It is also possible to replace the transducer, horn, and / or collet within the actuation unit 2.

[0102] In the exploded configuration illustrated in Figure 1, the ultrasonic signal generator 10 is separate from the operating unit 2 and is connected to the operating unit 2 by a connector cable 12. An integrated configuration in which the ultrasonic signal generator 10 is incorporated into the housing of the operating unit 2 is also possible.

[0103] The example shown in Figure 1 has an externally powered ultrasonic signal generator 10 and therefore includes a power cable 14 connected to an external power source. Other examples may be powered by an internal battery that can be incorporated into the ultrasonic signal generator unit 10 or the operating unit 2.

[0104] Generally, the components of the system are preferably portable, and more preferably handheld. The components may be wireless, rechargeable, reusable, and recyclable. Any external cables 12, 14 for transmitting power or signals may be coupled through slip rings to allow free rotation of the cables 12, 14 and to avoid entanglement with the wires 4.

[0105] The diameter of the distal end of wire 4 determines its distal flexibility and its ability to easily conform to the shape of the biostructure through which it is intended to pass. For example, for a particular nitinol with a specific thermal transition temperature, a distal end having an appropriate length and a diameter of, for example, 0.005 to 0.007 inches provides both appropriate flexibility and the ability to excavate occluding material in tortuous biostructures (such as the foot or coronary arteries).

[0106] When using ultrasonic energy to excite wire 4, it is desirable to optimize the displacement amplitude at and around the distal tip of the wire in order to excavate and traverse the lesion. Conversely, it is desirable to minimize the displacement or movement of the proximal end portion of wire 4, which is outside the patient's body and may have a portion hanging freely from the proximal side of the actuator unit 2. To achieve this, the distal length of wire 4 from the distal tip to where the actuator unit 2 is coupled to wire 4 should be an odd multiple of a quarter wavelength of ultrasound. This creates a standing wave in the wire with an antinode vibrating at the distal tip, and the amplitude of the vibration at the distal tip is maximized.

[0107] Referring here to Figure 2, the wire 4 includes a region in which its geometric shape tapers to produce a change in diameter. Specifically, the wire 4 shown in Figure 2 comprises a substantially straight proximal portion 16 and a substantially straight distal tip portion 18 that provides a drilling portion for traversing the lesion. The distal portion 18 may be thinner than the proximal portion 16 and may be tapered, or its diameter may be uniform along its length.

[0108] The distal portion 18 is joined to the proximal portion 16 by a transition portion 20 that is tapered distally. The proximal portion 16, the distal portion 18, and the transition portion 20 are coaxially aligned with each other along the central longitudinal axis of the wire 4, but are substantially flexible so that they can be bent along their lengths.

[0109] The purpose of the tapered transition section 20 is to provide gain and sustain the transmission of ultrasonic energy through the wire 4. For amplification purposes, the change in cross-sectional area represents the level of gain for both lateral and longitudinal displacement amplitudes in the wire 4. The length and diameter of the distal section 18 determine the modes and magnitudes of displacement in the axial and radial directions. The transition section 20 also influences how the lateral modes of displacement can be established in the distal section 18 of the wire.

[0110] As with all intravascular wires, a balance is required between flexibility, expressed as "trackability," and rigidity, expressed as "pushability" or "steering ability." As mentioned earlier, pushability requires longitudinal cylindrical rigidity, and steering ability requires torsional rigidity. However, unlike passive wires, wire 4 also needs to be able to transmit ultrasonic energy to the distal portion 18 to assist in traversing the lesion. In this way, wire 4 functions as an excavator not only at its tip but also along part of its length. In particular, the distal portion 18 acts radially as a lateral excavation device for creating an opening in the intravascular lesion. Wire 4 may also have a distal portion formed to amplify radial excavation.

[0111] Since the target of the activated wire 4 is to pass through the lesion, its dimensions are optimized to excavate the largest possible opening with a given input. Specifically, the distal portion 18 of the wire 4, when activated by ultrasonic energy as shown in Figure 2, moves in primary longitudinal modes, moving inward and outward, and also radially, and excavates by mapping out a larger volume at the distal end through lateral movement or radial displacement along the wire 4. The distal portion 18 of the wire 4 is also found to move through lateral and undulating motion at or near the driving frequency under resonant waves and second-order modes of differential harmonics, depending on the operating frequency, the length of the distal portion 18, and the meandering of the anatomical structure. These waveforms may interfere with each other and may be more or less effective in excavating material at different moments.

[0112] Figures 3a and 3b illustrate one of the reasons for these complex movements of the distal portion 18 when the wire 4 is in operation. Figure 3a shows the first, second, third, and fourth harmonic waveforms 22A, 22B, 22C, and 22D. Note that the wavelengths of the second, third, and fourth harmonic waveforms 22B, 22C, and 22D are each half the wavelength of the preceding waveform. Figure 3b shows the composite waveforms 24A, 24B, and 24C generated from the combination or superposition of the harmonic waveforms 22B, 22C, and 22D with the harmonic waveform 22A in Figure 3a.

[0113] As shown in Figure 4 of the drawings, if the distal portion 18 of the wire 4 extends beyond the surrounding sheath or catheter 26, further low-frequency transverse vibrations may occur. The degrees of freedom of motion allow for the expression of transverse components, some of which may arise from the cantilever effect. In this regard, Figure 4 shows a method by which the wire 4 is sleeved in this way, allowing a desired distal length to vibrate freely in the transverse direction as shown. The distal range of the sleeve, and therefore the length of the free end of the wire 4, controls the drilling by the distal portion 18 of the wire 4. By sleevening or covering the wire 4 to the resonant length or harmonic wavelength such that the distal end of the catheter 26 substantially coincides with the resonant length or harmonic wavelength, the wire 4 can drill a larger opening.

[0114] Optionally, the catheter 26 and / or wire 4 can be moved longitudinally relative to each other in the distal and proximal directions, as shown in the figure, by rotating, for example, a thumbwheel on the actuation unit 2 that acts on the outer sleeve of the catheter 26. Furthermore, the behavior of the wire 4 can be influenced by adjusting the radial gap between the catheter 26 and the wire 4, or by applying a radially inward force from the catheter 26 around the wire 4, as schematically shown in Figure 4. The effect of constricting or forcibly restraining the wire radially using a collar such as a balloon will vary depending on the frequency at the time, the relative position of the sound source, and the position where it is coupled to the wire.

[0115] The diameters of the various sections 16, 18, and 20 of the wire 4 are selected for the optimal balance between pushability and trackability, in addition to allowing subsequent devices of standard dimensions to use the wire 4 as a guide wire. For example, the proximal section 16 may have a diameter of 0.43 mm, and the distal section 18 may have a diameter of 0.18 mm or 0.25 mm. The taper of the intermediate transition section 20 is slight and is therefore greatly exaggerated in Figure 2. The transition section 20 may extend over a length that is a multiple of λ or a length that is a fraction of λ, where the numerator is preferably 1 and the denominator is an even number (e.g., an sequence of 1 / 2, 1 / 4, 1 / 8, etc.), while the distal section 18 may have a length that is λ / 2 or a multiple of λ / 2 or a fraction of λ / 2 such as λ / 4. For the materials considered for parts 18 and 20, the optimal lengths we found are λ, λ / 2, and potentially λ / 4 for lower harmonics and thinner wires.

[0116] The overall geometric shape of wire 4, including its nominal diameter and length, as well as the driving frequency of the system, are determined by the natural velocity of sound in the wire's material. This characteristic is a function of the material's properties and its geometric shape. The selected frequency generates harmonics along the length of the wire, and the load at the end of wire 4 helps establish a standing wave. The system can generate lateral and longitudinal displacements over frequency ranges far from the driving frequency range, often occurring in the harmonics of the frequency at the distal end 18.

[0117] In one embodiment, without excluding other dimensions, a wire 4 having a core cross-sectional diameter of 0.43 mm defining a proximal portion 16 has a tapered transition section 20 optimally positioned to transition to a distal portion 18 with a diameter of 0.18 mm. The lengths of each portion 16, 18, and 20 of the wire 4 can be selected to have a longitudinal resonant mode at a driving frequency, for example, 40 kHz or nearby, and strong harmonics at 20 kHz or nearby, 10 kHz, etc. With appropriate design, there are adjacent lateral modes at 40 kHz and 20 kHz, etc. Amplification of about 2.4 times or other appropriate values ​​may be possible across the tapered transition section 20.

[0118] As a result, even when wire 4 is driven by longitudinal vibration, the desired lateral mode is excited, as shown in Figure 2, by appropriately selecting the material, geometry, and distal design features. Both longitudinal and lateral vibrations work together to excavate the lesion, and as a result, wire 4 opens an opening or lumen in the lesion with an inner diameter substantially larger than the diameter of wire 4.

[0119] Therefore, when activated, the wire 4 functions as a drilling tool that tunnels its own path by drilling material distal to the tip 18 of the wire 4 through its longitudinal movement, and then by providing a lateral offset that widens the tunnel diameter through the offset translational or lateral movement of the wire 4 within the vascular structure. As a result, the wire 4 scrapes the inner surface of the occlusion not only at its distal tip but also along a portion of its length extending proximal from the distal tip, forming a wider opening for subsequent treatment devices on the wire 4 to pass through. This effect is shown in Figures 5 to 8 of the drawings.

[0120] Figure 5 shows how the distal portion 18 of the wire 4 can excavate an opening 28 within the lesion 30, which has a diameter larger than the diameter of the wire 4, thereby forming a larger lumen into which treatment can be introduced into the lesion 30. The active wire 4 performs both longitudinal, axial, or directional excavation and radial, transverse, or orbital excavation by orbiting the outside of the axial plane of the wire 4 in a consistent, monotonous manner with different harmonics.

[0121] Wire 4 can be guided along the blood vessel 32 to the lesion 30 in either active or passive mode. When activated and in contact with the lesion 30, wire 4 transitions from a "fixed-free" state to a "fixed-fixed" state, which attenuates the amplitude generated in wire 4 to some extent. As wire 4 passes through the lesion 30, a low-harmonic displacement is generated, and then, when wire 4 returns to the "fixed-free" state, a lateral low-harmonic component is generated, excavating a larger opening 28. In this way, the lateral vibration of wire 4 cuts open a channel through the lesion 30 in the lumen of the blood vessel 32.

[0122] Figures 6, 7, and 8 illustrate how the ability to change the relative longitudinal position of the wire 4 and catheter 26 can be used to influence the lateral movement of the distal end of the wire 4, thereby influencing the secondary or lateral excavation, perforation, or tunneling of the lesion 30 by the wire 4 within the lesion 30. In particular, Figures 6, 7, and 8 schematically illustrate how the distal end of the wire 4 first penetrates the lesion 30 as shown in Figure 6 to form a longitudinal opening 28, and then the lateral vibration of the wire 4 is optimized to widen the opening 28 and form a lumen of a desired diameter, as shown in Figures 7 and 8.

[0123] When the free end of wire 4 extends distally beyond the lesion 30, the lateral vibration at the free end portion initiates lateral excavation of the distal segment of lesion 30, as shown in Figure 7. Next, when the working wire 4 is pulled back proximal through lesion 30, the opening 28 expands and widens, aided by the optimization of lateral vibration in the portion of wire 4 between catheter 26 and lesion 30, as shown in Figure 8. If necessary, the working wire 4 can be pushed distally through lesion 30 to further widen the opening 28.

[0124] Referring again to Figures 2-8, it will be clear that the behavior of the active wire 4, particularly its distal tip 18, changes as the wire 4 is affected by the changing environment during its use in a biological structure. Therefore, the behavior of the wire 4 depends on the position of the distal tip 18 in the biological structure, the medium through which the distal tip 18 moves, and especially the material and structure in contact with the distal tip 18. These behaviors, and the changes between them, manifest in relation to wavelength, frequency, amplitude, and the representation of harmonic and composite waveforms.

[0125] The present invention embodies the principle that these characteristics of the behavior of the active wire 4 generate unique acoustic radiation, and by detecting and analyzing this acoustic radiation, the behavior of the active wire 4 can be determined, and thereby the factors that generate that behavior can be inferred. Therefore, it is possible to infer information such as the medium through which the distal tip 18 is moving, and the material and structure in contact with the distal tip 18, using the acoustic signature.

[0126] To illustrate this principle, Figure 9 shows the acoustic signature of the active wire 4 before contact with the lesion 30 on the left and the acoustic signature while in contact with the lesion 30 on the right. Two acoustic signatures are shown on the right side of Figure 9: one from an acoustic sensor located distally, near the active tip of the wire 4, and the other from an acoustic sensor located proximal, for example, within or adjacent to the actuation unit 2. The acoustic signatures are plotted as frequency on the vertical axis against time on the horizontal axis. In this example, the lesion 30 was represented by a sample of calcium carbonate in the form of chalk. The wire 4 was driven at a frequency of 40 kHz.

[0127] As shown on the left side of Figure 9, it is clear that before contact with lesion 30, wire 4 exhibits vibrations mainly around the 20 kHz harmonic. Conversely, as shown on the right side of Figure 9, while in contact with lesion 30, wire 4 begins to exhibit vibrations at various harmonic frequencies below 20 kHz, as indicated by ellipse A. Thus, the acoustic signature reflects that wire 4 is currently in the process of passing through lesion 30. Furthermore, by analyzing the aspect of the acoustic signature and comparing it with known signatures, lesion 30 itself can be characterized. For example, the occurrence of cavitation is usually characterized by an increase in broadband noise.

[0128] Figure 10 shows the components and elements of the system 34 that detect and act upon acoustic feedback from the active wire 4. Figure 10 also shows the data flow through the system, including communication. A controller 36, which may be located within the housing of the actuation unit 2, controls an ultrasonic generator 38 to generate a signal that is converted into ultrasonic energy by a transducer 40. The ultrasonic energy is supplied to the active wire 4, which is guided through the vascular structure and traverses an occlusion such as a CTO, via a coupling 42 such as the aforementioned collet and an optional acoustic horn.

[0129] Acoustic feedback from the active wire 4 is received by one or more acoustic sensors 44, such as microphones, or other transducers, amplified by an amplifier 46, filtered by a series of bandpass filters 48, and then converted to analog-to-digital 50 to generate feedback data that is sent to the processor 52. The controller 36 controls a preferred wireless communication system 54, for example, using a Wi-Fi network or Bluetooth connection, to receive the data from the processor 52 and transmit that data from the housing unit to local storage 56 and / or the cloud 58. Figure 4 also shows means of providing feedback to the user, such as the aforementioned display 60 and / or haptic feedback system.

[0130] The system 62 shown in Figure 11 is an improvement on the system 34 in Figure 10. Similar features are represented by similar numbers. In the system 62 of Figure 11, non-acoustic feedback is obtained from a second additional source, namely a feedback receiver 64. The signal from the feedback receiver 64 is amplified by an amplifier 46, filtered by a bandpass filter 48, and then subjected to an analog-to-digital conversion 50 to generate additional auxiliary feedback data that is sent to the processor 52.

[0131] The feedback receiver 64 can, for example, detect changes in the impedance of the transducer 40 driving the wire 4, and these changes result from changes in losses in the system as the wire 4 becomes attenuated or more or less constrained. For example, as attenuation increases, the Q value of the system decreases.

[0132] The Q value can be measured as shown in Figure 12. The upper trace in Figure 12 shows the voltage applied to the transducer 40 by the ultrasonic generator 38. The lower trace shows the current flowing through the transducer, as measured by the feedback receiver 64. When the voltage signal is suddenly stopped, the system continues to resonate for a time length proportional to Q. By curve-fitting an exponential decay function to the current signal, the processor 52 can derive the value of Q, and therefore the decay. This value is influenced by the nature of the lesion 30.

[0133] Characterizing impedance changes may involve separating differences based on position or dynamic variations and comparing variations in voltage, current, and phase angle over different time periods. Using the superposition of data representing this electrical response and data representing the corresponding acoustic response at a given time point, the characteristics of the blood vessel 32, its lumen, and the lesion 30 can be more accurately analyzed and described.

[0134] Similarly, it may be possible to employ two or more acoustic sensors 44 at different locations within the system or relative to the lesion 30 to provide additional acoustic data to corroborate and confirm the measured characteristics of the blood vessel 32, its lumen, and any lesion 30. Figures 12–20 illustrate various possibilities in this regard, but it is understood that one, two, or more acoustic sensors 44 may be employed at or near any of the locations described and illustrated.

[0135] Generally, the acoustic sensor 44 may be placed at any of several locations within the system. Different sensor locations will yield different acoustic signatures. By placing multiple acoustic sensors around the transducer 40 and associated collets, different relative patterns of characteristic spectra can be generated that can be examined for correlation with various features. External acoustic sensors may also integrate lighting, such as LEDs, to provide visual feedback on the system's performance. This can be interpolated from changes in the acoustic signature or by superimposing the acoustic response on top of the system's electronic or electrical response.

[0136] Next, referring to Figure 13, which shows an ultrasonic actuator 2 with a wire 4 extending longitudinally. In this example, the actuator 2 is powered externally and optionally supplied with an ultrasonic signal via cable 12.

[0137] Figure 13 shows that the actuator unit 2 includes an ultrasonic transducer 40 and a distally tapered acoustic horn 66 attached to the distal surface of the transducer 40. A collet 68 connects the wire 4 to the distal end of the horn 66. The transducer 40, the horn 66, and the collet 68 have a central lumen through which the wire 4 can pass. This allows the wire 4 to extend along the entire length of the actuator unit 2 and exit proximal to the actuator unit 2. The actuator unit 2 can be moved along the wire 4 and then coupled at any of the various positions along the wire 4 to transmit ultrasonic energy to the wire 4. In an alternative configuration, the wire 4 can instead exit laterally from the actuator unit 2 at a position proximal to the collet 68.

[0138] In Figure 13, a catheter 26 surrounding and supporting the wire 4 can be coupled to the distal region of the wire 4. In this example, the coupling is performed by a distal annular balloon 70 within the catheter 26, which expands into the distal lumen of the catheter 26 around the wire 4. The balloon 36 can be inflated via an inflation port 38 on the catheter 26. The catheter 26 may also include additional ports and lumens, for example, for aspirating embolisms or fragments or particles generated during excavation.

[0139] Optionally, the balloon 70 or other connector can be configured to grip the wire 4 and apply an inward clamping force to the distal portion of the wire 4. In this way, ultrasonic energy is coupled through the waveguide element of the catheter 26, and electromechanical energy can be transmitted from the catheter 26 to the distal tip region of the wire 4 via the connector provided by the balloon 70.

[0140] The proximal end of the catheter 26 is coupled to the transducer 40 by an adapter element 72. The proximal end of the adapter element 72 abuts against the distal end of the horn 66 around the collet 68, thereby coupling to the transducer 40 to receive ultrasonic energy. In principle, the adapter element 72 can facilitate the transmission of energy from the transducer 40 in any of the three operating modes: operating the wire 4 independently, operating the catheter 26 independently, or operating the catheter 26 and wire 4 simultaneously.

[0141] The acoustic sensor 44 can be positioned outside the actuation unit 2, inside the body of the actuation unit 2, or on different parts of the catheter 26. Having the acoustic sensor in different positions allows for the provision of unique interference and characteristic patterns in the acoustic spectrum.

[0142] In the example shown in Figure 13, the acoustic sensor 44 is positioned adjacent to the collet 68 and proximal to the collet 68 on an adapter element 72, which is mounted on the housing of the actuation unit 2.

[0143] In addition to arranging the acoustic sensor 44 inside the housing or casing of the actuation unit 2, it is also possible to arrange the acoustic sensor 44 outside the housing, for example, along the catheter 26. In this regard, Figure 14 shows the appearance of the actuation unit 2 having a catheter 26 extending distally from the unit 2. Here, various acoustic sensors 44 are arranged distal to the collet 68. One acoustic sensor 44 is located at the distal end of the unit 2, specifically on or within the toggle 8 that acts on the internal collet 68. Two more acoustic sensors 44 are shown on the catheter 26, one near the proximal end of the catheter 26 and the other near the distal end.

[0144] Figure 15 shows the catheter 26 and the wire 4 within it, separated from the operating unit 2. An acoustic sensor 44 is shown near the distal end of the catheter 26. Thus, the catheter 26 provides a means for introducing the acoustic sensor into a blood vessel.

[0145] A method is provided for measuring the mode of interaction between the wire 4, blood, and any acoustic effects resulting from the interaction between the wire 4 and the blood vessel 32 or any occlusion 30 therein, by incorporating an acoustic sensor 44 into the catheter 26 and introducing the catheter 26 to the location of the occlusion on the wire 4 or to the distal end of the wire 4. As described above, it is possible to adjust and control the distance the wire 4 extends beyond the microcatheter sleeve, and therefore the length of the wire 4 exposed in the lumen of the blood vessel 32. This provides additional control over how the wire 4 is excited and how acoustic emissions can be formed from within the blood vessel 32.

[0146] By housing the acoustic sensor 44 inside or on the catheter 26, the entire system becomes more efficient. The proximity of the wire 4 and the acoustic sensor 44, along with its ability to capture radiation from the catheter 26, increases the reliability of acoustic sensing and reduces potential variability due to tissue variations, while becoming more sensitive to potential variability in the acoustic radiation pattern resulting from the interaction between the wire 4 and the catheter 26.

[0147] Figure 16 shows that sensors can also be attached to the wire 4 itself, for example, in the form of an electrical or optical strain gauge 74. In this example, the strain gauge is attached to the proximal end 16 of the wire 4, near the tapered transition 20 that leads to the thinner distal end 18 of the wire 4. Such a sensor can function as an acoustic sensor, or the behavior of the wire 4 can be more directly determined from the strain generated in the wire 4 when it is activated. For example, by incorporating an acoustic emitter or microarray on the surface of the wire 4, a means can be provided to optimize radiation in a particular range of interest. The signal from the strain gauge 74 can further corroborate data received from an acoustic sensor 44, in addition to, or instead of, non-acoustic feedback from a feedback receiver 64 as shown in Figure 11.

[0148] Figures 17–21 illustrate various methods for positioning acoustic sensors on or within a patient's body, exemplified here by the patient's leg 76. In each case, an active wire 4 is advanced through the patient's vascular structure into a vessel 32 occluded by a lesion 30, shown here in the lower leg 76. The distal end of the wire 4 is engaged with the lesion 30 and, activated by ultrasonic energy, is attempting to begin drilling a channel through the lesion 30.

[0149] Figures 16 to 19 show the external placement of the acoustic sensor 44. By placing the acoustic sensor 44 outside the body, acoustic radiation from the wire 4 and blood vessel 32 can be examined through the surrounding tissue.

[0150] In Figure 16, the acoustic sensor 44 is incorporated into a surgical patch or embodied in a surgical band or the like to bring it close to the tissue. The acoustic sensor 44 is positioned along the length of the blood vessel 32 or near the region of interest in the area of ​​the patient's body affected by the disease of the blood vessel 32. Alternatively, an ultrasound probe can be used as the acoustic sensor 44 to detect acoustic emissions, as shown in Figure 17 as a fixed unit and in Figure 18 as a handheld unit that can sweep over the patient's skin near the lesion 30. The data from the probe can then be used directly to interpolate the location and proximity of the lesion 30, as well as the manner in which the wire movement is obstructed, and to characterize any occlusions that may be present.

[0151] Figures 20 and 21 show the internal placement of the acoustic sensor 44 on the probe 78, which is positioned inside the body. This allows the acoustic sensor 44 to be introduced through the tissue into compartments surrounding the blood vessel 32, and to approach the area of ​​the blood vessel 32 where the lesion 30 is being treated or the area of ​​the blood vessel 32 where the lesioned inner tissue is being evaluated.

[0152] A method is provided for approaching the area of ​​a lesion 30 or blood vessel 32 by surgically inserting a probe 78 carrying an acoustic sensor 44 at its distal tip into the tissue. This makes it possible to detect acoustic radiation generated by the interaction between the wire 4 and its surroundings and transmitted through the blood vessel 32 without the loss and aberration of the acoustic spectrum that can occur by passing through considerable thickness of muscle and skin.

[0153] Finally, Figures 22–27 show how acoustic signals, particularly at specific frequencies, are generated as the active wire passes through various materials. The selected materials are chalk (Figures 22 and 23), BegoStone (Figures 24 and 25), and water (Figures 26 and 27). BegoStone® is a commercially available ultra-hard gypsum originally developed for dental use. In each case, the wire and sample were placed in a water tank, and signals were acquired using a hydrophone placed near the distal end of the wire. The signals were captured on an oscilloscope and no post-processing was performed.

[0154] For each material, the acoustic signals are shown across a wide frequency range up to 125 kHz (Figures 22, 24, and 26) and a narrower low (audible) resonance range up to 10 kHz (Figures 23, 25, and 27). The lower range is taken from a larger dataset, which itself is a sample in time.

[0155] Nominally, the system is designed to be driven at 40 kHz, but with wire 4 and collet 68 in place, the system actually resonates at a slightly different frequency of approximately 38 kHz (hence the electronics driving the system). Therefore, after subtracting all other acoustic effects, it is expected that only a line will be visible at a frequency of approximately 38 kHz. Such a line is obvious and can be measured electronically by the feedback receiver 64, as well as the 40 kHz line to which wire 4 is designed to resonate. However, several more emitted resonant frequencies are observed as features that appear at different frequencies, particularly harmonics of the system's driving frequency, as well as at other frequencies. Thus, in addition to the 38 kHz line, large amplitude acoustic radiation can be seen at harmonics of 8 kHz, 19 kHz, and 76 kHz, and at even higher frequencies such as 114 kHz. Other characteristic features appear around and between these harmonics of the driving frequency. Characteristic radiation at different frequencies also appears in the lower range shown in Figures 23, 25, and 27.

[0156] Many other modifications are possible within the scope of the concept of the present invention. For example, one or more acoustic sensors 44 can be arranged on a distal tube, as disclosed in the inventors' previous patent application published as International Publication No. 2021 / 224357. Such a tube extends distally from the actuation unit 2 and protects and guides the wire 4 inside, relieves strain, and / or applies a damping force to the wire 4. Such a tube can also function as a connector to a structure located distal to the actuation unit 2, such as a Luer fitting or other inlet port.

[0157] In another variation, it is possible to intentionally change the nature of the stimulus signal applied to transducer 40. In the typical case (and as shown in Figures 21-26), the applied stimulus is a continuous sine wave of a single frequency. However, by using other waveforms such as pulse waveforms, multitone waveforms, chirp waveforms, and noise waveforms, different features can be extracted from the corresponding response signals. This utilizes the ability of processor 52 to correlate the input stimulus with the output response.

[0158] To maximize the system's sensitivity when analyzing response signals from the feedback receiver 64 and / or acoustic sensor 44, it is possible to create a “baseline” response signal that can be later subtracted from the changing response signal. The baseline is most usefully obtained when the distal tip of wire 4 is close to but not touching the lesion 30. In this way, the baseline response signal encapsulates all the fundamental features of the system, including the tortuosity of the vascular structure to which wire 4 extends to the lesion 30. Alternatively, the baseline may be acquired continuously and automatically, and the system itself can determine when to apply the subtraction algorithm.

Claims

1. An intravascular device for determining the condition of blood vessels in the body, wherein the device is A long, thin waveguide element which is a wire, An operating unit including an ultrasonic energy source, and a coupling portion for coupling the ultrasonic energy source to the wire and operating the wire, thereby transmitting ultrasonic energy from the ultrasonic energy source along the wire to the active distal portion of the wire, The system comprises a signal acquisition system configured to acquire feedback signals from the device in order to interpret the state of blood vessels, The signal acquisition system comprises at least one acoustic sensor for acquiring an acoustic feedback signal generated as a vibration response by the interaction between the active distal portion of the wire and adjacent tissue or occlusion when the wire is operating, wherein the at least one acoustic sensor is located outside the housing of the operating unit. The at least one acoustic sensor, An external sensor positioned to make contact with a part of the body, or, An internal sensor that is positioned to be inserted into the body, or, Attached to the catheter surrounding the aforementioned wire, An intravascular device wherein the acoustic feedback signal includes a signal indicating the displacement of the vibration amplitude, frequency, or attenuation of the active distal portion, which is generated by interaction with adjacent tissue or occlusion.

2. The apparatus according to claim 1, wherein at least one acoustic sensor is mounted in or on the operating unit.

3. The apparatus according to claim 2, wherein at least one acoustic sensor is mounted longitudinally aligned with the coupling portion of the actuation unit, or proximal to the coupling portion of the actuation unit.

4. The apparatus according to claim 2 or 3, wherein at least one acoustic sensor is mounted distal to the coupling portion of the operating unit.

5. The apparatus according to any one of claims 1 to 4, wherein at least one acoustic sensor is mounted parallel to the wire.

6. The apparatus according to any one of claims 1 to 5, wherein a strain gauge is fixed to the wire in order to obtain an operational feedback signal from the wire.

7. The apparatus according to claim 6, wherein the strain gauge functions as an acoustic sensor.

8. The apparatus according to any one of claims 1 to 7, wherein the signal acquisition system comprises at least two acoustic sensors spaced apart from each other in the longitudinal direction.

9. The apparatus according to any one of claims 1 to 8, further comprising at least one electronic sensor configured to acquire an operational feedback signal representing the operating parameters of the ultrasonic energy source.

10. The apparatus according to claim 9, wherein the operating parameter is the frequency and / or amplitude and / or phase of the current drawn in by the ultrasonic energy source, or the voltage drop across both ends of the ultrasonic energy source.

11. The apparatus according to claim 9 or 10, wherein the signal acquisition system is configured to monitor fluctuations in the frequency or amplitude of vibration of the wire via the coupling portion.

12. The apparatus according to any one of claims 1 to 11, further comprising a signal processing system for processing a feedback signal acquired by the signal acquisition system.

13. The apparatus according to claim 12, wherein the signal processing system is configured to employ a numerical algorithm selected for a particular type of wire.

14. The apparatus according to claim 12 or 13, wherein the signal processing system is configured to determine the characteristics of intravascular occlusion from the acquired feedback signal.

15. The apparatus according to any one of claims 12 to 14, wherein the signal processing system is configured to compare the relative contribution of the loss due to anatomical tortuosity when guiding the active distal portion to occlusion with the loss that occurs when the active distal portion passes through the occlusion.

16. The apparatus according to any one of claims 12 to 15, wherein the signal processing system is configured to compare the acquired feedback signal with stored data characterizing known blockages, and to characterize the blockage with respect to the comparison.

17. The apparatus according to any one of claims 12 to 16, wherein the signal processing system further comprises an output to a user interface and / or an output to an external data acquisition system.

18. The apparatus according to any one of claims 12 to 17, wherein the signal processing system further comprises inputs from a user interface and / or from an external data network.

19. The apparatus according to any one of claims 12 to 18, further comprising a controller that responds to the signal processing system.

20. The apparatus according to claim 19, wherein the controller is configured to modulate the excitation voltage applied to the ultrasonic energy source or the excitation current supplied to the ultrasonic energy source.

21. The apparatus according to claim 20, wherein the controller is configured to control the ultrasonic energy source by changing the frequency and / or amplitude of the excitation voltage applied to the ultrasonic energy source.

22. The apparatus according to claim 20 or 21, wherein the controller is configured to drive the frequency of the excitation voltage by using the phase difference between the excitation voltage and the excitation current in combination with the amplitude of the excitation voltage.

23. The apparatus according to any one of claims 19 to 22, wherein the controller comprises an amplitude feedback controller and is configured to use a resonant frequency as the operating point of the control.

24. The apparatus according to any one of claims 19 to 23, wherein the controller is configured to pulse or change the drive signal to the ultrasonic energy source.

25. The aforementioned controller, The modulation of the transmitted signal is monitored, and the ultrasonic energy source is automatically controlled to compensate for background energy loss occurring in the wire as the active distal portion approaches occlusion. The apparatus according to any one of claims 19 to 24, configured to distinguish between the background energy loss and the additional energy loss when the active distal portion passes through the occlusion, and to correct the background energy loss so as to maintain the displacement in the active distal portion.

26. The apparatus according to any one of claims 19 to 25, wherein the controller is configured to modify or change the control algorithm in response to fluctuations in the operating parameters of the ultrasonic energy source resulting from the interaction between the active distal portion and the occlusion during use.

27. A communication system comprising the device described in any one of claims 1 to 26, wherein the communication system communicates data with a computer system configured to receive data from the device, optimize and update a control algorithm accordingly, and output the optimized and updated control algorithm to the device.

28. The communication system according to claim 27, wherein two or more of the devices communicate data with the computer system, the computer system is configured to optimize a control algorithm according to data received from a plurality of actions performed using the devices, and to output the optimized and updated control algorithm to the devices.

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