Tissue-removing catheter including tissue-type detection

Abstract

A tissue-type detector for a tissue-removing catheter includes an acoustic sensor. The acoustic sensor senses an acoustic signal emanating from the catheter, such as a motor of the catheter. The acoustic sensor may be mounted on a handle or catheter body of the catheter. The tissue-type detector may include a processor and memory storing executable instructions for the processor. Using data from the acoustic sensor and the executable instructions, the processor determines a type of tissue being engaged by the catheter.

Description

TISSUE-REMOVING CATHETER INCLUDING TISSUE-TYPE DETECTION

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 612,834, filed December 20, 2023, the entire content of which is incorporated herein by reference.FIELD

[0002] The present technology is generally related to a tissue-removing catheter including a tissue-type detector.BACKGROUND

[0003] Vascular disease frequently arises from the accumulation of atheromatous material on the inner walls of vascular lumens, particularly arterial lumens of the peripheral and other vasculature, especially peripheral arteries, resulting in a condition known as atherosclerosis. Atherosclerosis occurs naturally as a result of aging, but may also be aggravated by factors such as diet, hypertension, heredity, vascular injury, and the like. Atheromatous deposits can have widely varying properties, with some deposits being relatively soft and others being fibrous and / or calcified. In the latter case, the deposits are frequently referred to as plaque.

[0004] Vascular disease can be treated in a variety of ways, including drugs, bypass surgery, and a variety of catheter-based approaches, including those which rely on intravascular debulking or removal of the atheromatous or other material occluding a blood vessel. A variety of methods for cutting or dislodging material and removing such material from the blood vessel have been proposed, generally being referred to as atherectomy procedures. Atherectomy catheters intended to cut or excise material from the blood vessel lumen may employ a rotatable cutting blade (or other tissue-removing element) which can be advanced into or past the occlusive material in order to cut and separate such material from the blood vessel lumen. It is important that the user does not perforate the vessel wall during debulking.SUMMARY

[0005] The techniques of this disclosure generally relate to detecting tissue type during operation of the tissue-removing catheter using acoustic data collected during the tissueremoving operation.

[0006] In one aspect, the present disclosure provides a tissue-removing catheter for removing tissue from a body lumen. The tissue-removing catheter comprises an elongate catheter body configured for insertion into the body lumen. The catheter body has opposite distal and proximal portions, and a longitudinal axis extending between the distal and proximal portions. A tissue-removing element is located generally at the distal portion of the catheter body and configured to rotate about a rotational axis and mechanically remove tissue from the body lumen. A motor is operably connected to the tissue-removing element to impart rotation of the tissue-removing element about the rotational axis during a tissue-removing operation of the catheter. A tissue-type detector including an acoustic sensor configured to sense an acoustic signal emanating from the catheter when the tissue-removing element engages the tissue in the body lumen during the tissue-removing operation of the catheter.

[0007] In another aspect, the disclosure provides a tissue-type detector for a tissueremoving catheter of the type including a handle housing a motor that drives a tissueremoving element. The tissue-type detector comprises an acoustic sensor configured to be coupled to the handle of the tissue-removing catheter. The acoustic sensor is configured to sense an acoustic signal emanating from the tissue-removing catheter during a tissueremoving operation and generate a sensed signals indicative of the acoustic signal. Memory includes processor-executable instructions. The processor-executable instructions include tissue-type classification instructions. A processor is in communication with the acoustic sensor and the memory. The processor is configured to execute the tissue-type classification instructions to determine a type of tissue being engaged by the tissue-removing element based on the sensed signal from the acoustic sensor.

[0008] The details of one or more aspects of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the techniques described in this disclosure will be apparent from the description and drawings, and from the claims.BRIEF DESCRIPTION OF DRAWINGS

[0009] FIG. l is a schematic, perspective representation of one embodiment of a tissueremoving catheter including a tissue-type detector.

[0010] FIG. 2 is an enlarged side view of a distal portion of the tissue-removing catheter in FIG. 1 received in a body lumen.

[0011] FIG. 3 A is an end view of the distal portion of the tissue-removing catheter in which the tissue-removing element is in a closed configuration.

[0012] FIG. 3B is a sectional view along the line A — A of FIG. 3 A.

[0013] FIG. 4A is an end view of the distal portion of the tissue-removing catheter in which the tissue-removing element is in an open configuration and extending outside a side window.

[0014] FIG. 4B is a sectional view along the line A — A of FIG. 4A.

[0015] FIG. 5 is an enlarged perspective of a handle of the tissue-removing catheter in FIG. 1.

[0016] FIG. 6 is similar to FIG. 5 with an upper portion of a handle housing of the handle being removed to show internal components.

[0017] FIG. 7 is another embodiment of a handle for the tissue-removing catheter of FIG.1.

[0018] FIG. 8 is an illustration of a neutral position of a lever of the handle.

[0019] FIG. 9 is an illustration of a tissue-removing position of the lever.

[0020] FIG. 10 is an illustration of a tissue-pacing position of the lever.

[0021] FIG. 11 is a schematic diagram of the tissue-type detector.

[0022] FIG. 12 is a schematic diagram of catheter system communicating with a processor of the tissue-type detector.

[0023] FIG. 13 is a schematic of the processor and memory of the tissue-type detector.

[0024] FIG. 14 is a simplified algorithm flowchart of instructions executed by the processor.

[0025] FIG. 15 is a graphical representation of a hit-driven log of signals from the acoustic sensor.

[0026] FIG. 16 is an illustration of connected relationships between hardware of an experimental set up for machine learning training of the catheter as described in the Experimental Example.

[0027] FIG. 17 is a prototype of an acoustic sensor mounted on the catheter body of the catheter used in the Experimental Example.

[0028] FIG. 18 is a prototype of an acoustic sensor mounted on the handle of the catheter used in the Experimental Example.

[0029] FIG. 19 is a flow chart of data acquisition used in the Experimental Example.

[0030] FIG. 20 is a table showing the accuracies of machine learning models and data used from the acoustic sensor in predicting type of tissue being engaged by the catheter in the Experimental Example.

[0031] FIG. 21 are graphs comparing frequency feature of importance in the ranges of frequencies recorded in the Experimental Example.DETAILED DESCRIPTION

[0032] Embodiments of a tissue-type detector and a tissue-removing catheter including a tissue-type detector are disclosed. The tissue-type detector is configured to detect characteristic(s) of the tissue (or other material) being engaged (e.g., debulked or cut) by the tissue-removing catheter during debulking of a body lumen. In one or more example, the detected characteristics may be used by the tissue-type detector to determine the type of tissue being engaged and / or provide feedback to a user based on the detected characteristics. In one or more examples, the feedback provided by the tissue-type detector may be used to provide an alert or alarm to the user, and / or communicate the type or characteristics of the tissue being engaged, and / or automatically perform an operation to inhibit or reduce damaging the body lumen and / or the tissue-removing catheter. As explained in more detail below, the tissue-type detector is configured to detect acoustic signals (e.g., acoustic emissions) emanating from a motor of the tissue-removing catheter and analyze the acoustic emissions to determine characteristic(s) of the type of tissue being engaged (e.g., debulked or cut) by the tissue-removing catheter during debulking of the body lumen.

[0033] Embodiments of the tissue-type detector may be suitable for use with atherectomy catheters for removing (i.e., excising) an atheroma (i.e., plaque) from a blood vessel,including removing plaque due to in-stent restenosis and penetrating chronic total occlusions (CTO). The disclosed tissue-type detector embodiments, however, may also suitable for treating stenosis of other body lumens and other hyperplastic and neoplastic conditions in other blood vessels and body lumens, such as the ureter, the biliary duct, respiratory passages, the pancreatic duct, the lymphatic duct, and the like. Neoplastic cell growth will often occur as a result of a tumor surrounding and intruding into a body lumen. While the remaining discussion is directed toward tissue-type detectors for catheters for tissue-removing and passing through atheromatous or thrombotic occlusive material in an artery, it will be appreciated that the tissue-type detector may be employed with other types of catheters for removing and / or passing through a variety of occlusive, stenotic, or hyperplastic material in a variety of body lumens.

[0034] Referring now to FIGS. 1 and 2, one non-limiting example of a suitable tissueremoving catheter, for use with embodiments of the tissue-type detector disclosed below, is generally indicated at 20. It is understood that the operational control mechanism disclosed below may be used with other types of catheters for removing tissue from a body lumen, and is not necessarily limited to "side cutting" atherectomy and tissue-removing catheters.

[0035] The illustrated catheter 20 comprises a catheter body 22 having a proximal portion 24 and a distal portion 26. Proximal portion 24 can be coupled to distal portion 26 with a connection assembly 27 to allow pivoting or deflection of distal portion 26 relative to proximal portion 24. A tissue-removing element 28, such as a rotatable cutter or abrasive element, is disposed within a lumen 30 of the catheter body 22. The tissue-removing element 28 removes tissue from the lesion or obstruction. It is understood that the tissueremoving element 28 may be another type of element for removing tissue, other than the illustrated cutter, including for example, an abrasive element (e.g., a burr). The cutter 28 is typically rotatable within the distal portion 26 about an axis that is parallel to the longitudinal axis of the distal portion of catheter 20 and axially movable along the longitudinal axis. In the illustrated embodiment, the cutter 28 can access target tissue through a side opening window 32 in the distal portion 26, which is typically large enough to allow the cutter 28 to protrude through and move out of the window 32 a predetermined distance. The cutter 28 is coupled to a handle, generally indicated at 34, through a coiled drive shaft 36. Actuation of an input device or manual actuator 38 on the handle, whichforms part of the deployment mechanism in this embodiment, can activate the drive shaft 36 and the cutter 28, and move the cutter longitudinally over a cam so as to deflect the distal portion and move the cutter out of cutting window 32. Camming of the cutter 28 can cause the distal portion 26 to pivot or deflect relative to the proximal portion 24 so as to deflect and urge the cutter into the tissue in the body lumen.

[0036] As shown in FIGS. 3-4, the cutter 28 will generally be movable between two or more positions using a deployment mechanism. In the illustrated embodiment, the actuator 38 actuates operation of the deployment mechanism, although in other embodiment, the deployment mechanism may be actuated by other actuators. In the illustrated embodiment, the deployment mechanism allows for the cutter 28 to be selectively moveable to a stowed or neutral position (FIGS. 3 A and 3B) in which the cutter is stowed in the distal portion 26 of the catheter body 22 and is not exposed through the window 32. Once the catheter 20 has reached the target site, the cutter 28 can be moved proximally to a tissue-removing position (FIGS. 4A and 4B), in which the cutter 28 extends through the cutting window 32 a distance LI beyond an outer diameter D of the distal portion 26. In some embodiments, in the tissue-removing position, the cutter 28 will have deflected the distal portion 26 and the cutter's axis of rotation will generally be in line with connection assembly 27 but angled or offset from longitudinal axis of the distal portion of the catheter body 22.

[0037] It is understood that in other embodiments, the tissue-removing catheter may be an orbital or rotational tissue-removing catheter. The rotatable tissue-removing element may be fully exposed outside a catheter body.

[0038] A first embodiment of the handle 34 is shown in FIGS. 5 and 6, and a second embodiment 34' is shown in FIG. 7. (The following description describes components of the handles 34, 34' that are the same, and identical or similar components are indicated by the same reference numerals. The differences between the embodiments are described below.) The handle 34, 34' includes a housing 40 that is sized and shaped to be held in a hand of the user. An electric motor 74 (e.g., a DC motor) is disposed in the housing 40, along with a power source 76 (e.g., a battery or other source of DC power) electrically connected to the motor for powering the motor. (The motor may be pneumatically drive or powered in some other way in other embodiments.) The drive shaft 36 is operatively coupled to the motor 74 when the catheter 20 is connected to the handle 34 for drivingrotation of the drive shaft and the cutter 28. In some embodiments, at maximum power the motor 74 can rotate drive shaft 36 between 1,000 rpm and 15,000 rpm or more, if desired. The manual actuator 38 (e.g., a lever, as illustrated) on the exterior of the housing 40 allows the user to control operations of the catheter 20. For example, in the illustrated embodiment the lever 38 is axially moveable relative to the housing 40. In particular, the lever 38 is movable to a neutral position (shown in FIG. 8), whereby the cutter 28 is in its non-exposed, neutral position (FIG. 3D). To expose the cutter 28 and activate the motor 74 to drive rotation of the cutter, the lever 38 is moved proximally from the neutral position to a proximal, tissue-removing position of the lever (see FIG. 9) to move the cutter proximally and out of cutting window 32 (FIG. 4B) to its tissue-removing position and simultaneously activate the motor 74. For example, proximal movement of the lever 38 to the proximal position may actuate (e.g., depress) an electrical switch 78 that electrically connects the power source 76 to the motor 74. To part off tissue, the lever 38 is moved distally from the proximal, tissue-removing position, back to its neutral position (FIG. 14) to drive (i.e., move) the cutter 28 distally into the distal portion of the catheter 20 (FIG. 3D). As the lever 38 is positioned in its neutral position, the electrical switch 78 is released (i.e., opened) so as to deactivate the electric motor 74. To pack the removed tissue in a collection chamber of the distal tip member 42, the lever 38 is moved distally from the neutral position to a distal position, packing position of the lever (see FIG. 10) to drive (i.e., move) the cutter 28 distally into the collection chamber and to its packing position. It should be appreciated, while the figures illustrate the use of a lever 38 or thumb switch, other embodiments of the present invention can use other types of actuators, such as separate buttons (e.g., a close window button, debulk tissue button, and packing button), or the like.

[0039] Referring to FIG. 11, the tissue-type detector 100 includes one or more acoustic sensors 110 (e.g., acoustic emission sensor(s)), one or more processors 120 in communication with the acoustic sensor, and memory 130 in communication with the processor and including instructions executable by the processor(s).

[0040] The processor(s) 120 may include multiple processors, a multi -threaded processor, a multi-core processor, and / or a multi -processor architecture. In some examples, the processor 120 may be an application specific integrated circuit (ASIC) or a field programmable integrated circuit (FPGA). In some implementations, the processor 120may be circuitry arranged to perform particular computations, such as, related to artificial intelligence (Al), graphics and machine learning. The processor 120 can include multiple processors, such as, for example, a central processing unit (CPU) and a graphics processing unit (GPU).

[0041] The memory 130 stores instructions 140 to be executed by the processor 120 as well as data elements used in the execution of those instructions. The memory 130 may include both volatile and nonvolatile memory, which are both examples of tangible media configured to store computer readable data and instructions to implement various embodiments of the processes described herein. Other types of tangible media include removable memory (e.g., pluggable USB memory devices, mobile device SIM cards), optical storage media such as CD-ROMS, DVDs, semiconductor memories such as flash memories, non-transitory read-only-memories (ROMS), dynamic random access memory (DRAM), NAND memory, NOR memory, phase-change memory, battery -backed volatile memories, networked storage devices, and the like. The memory 18 may include a number of memories including a main random access memory (RAM) for storage of instructions and data during program execution and a read only memory (ROM) in which read-only non-transitory instructions are stored. The memory 130 may include a file storage subsystem providing persistent (non-volatile) storage for program and data files. The memory 130 may further include removable storage systems, such as removable flash memory.

[0042] As shown in FIG. 13, the memory 130 may be configured to store the basic programming and data constructs that provide the functionality of the disclosed processes and other embodiments thereof that fall within the scope of the present embodiments. The memory 130 stores the instructions 140 including customized processing instructions. These instructions may include acoustic signal processing instructions 144, tissue-type identification instructions 146, and operational instructions 148, as will be discussed in more detail below. Memory 130 also stores data including recorded acoustic signals 150 and tissue-type information 152. During operation, the processor 120 executes instructions 140 to implement various embodiments, as described in more detail below. The memory 130 may also provide a repository for storing data used by the instructions 140 or data generated by execution of the instructions including acoustical signal recordings generated during past procedures.

[0043] The acoustic sensor 110 (e.g., acoustic emission sensor) senses acoustic waves (e.g., acoustic emissions) emitting from the catheter 20 during operation. These signals are communicated via wired or wireless connection to the processor 120 and are analyzed by the processor, based on the instructions 140 stored in memory, to determine one or more characteristics (i.e., tissue type) of the tissue being engaged by the catheter (e.g., the cutter) during operation, as explained in more detail below. The acoustic sensor 110 may be a piezoelectric sensor, transducer, or other type of sensor. The acoustic sensor 110 may be a suitable sensor for sensing acoustic emissions having frequencies from about 10kHz to about 2 MHz, for example. In one or more embodiments, as shown in FIG. 11, the tissue-type detector 100 may also include a pre-amplifier 160 receiving an output signal from the acoustic sensor 110, and an analog filter 170 (e.g., band-pass filter) filtering the output signal from the pre-amplifier before being received by the processor 120.

[0044] In one embodiment, as shown in FIGS. 6 and 7, the acoustic sensor 110 is coupled or couplable to the handle 34, 34' for receiving acoustic emissions of the catheter 20. It is believed that the acoustic emissions received from the handle 34, 34' originate from the motor 74. In particular, it is believed that the motor 74 emits different acoustic signals depending on the type of tissue or other material being engaged by the catheter during operation (i.e., during operation of the motor rotating the tissue-removing element). These acoustic signals are transmitted to the component of the handle 34, 34' to which the acoustic sensor 110 is coupled, whereupon the handle component emits acoustic emissions that are sensed by the acoustic emission sensor.

[0045] In one embodiment, the acoustic sensor 110 may be coupled to the handle 34, 34'. In one example, such as shown in FIG. 7, the acoustic sensor 110 is mounted on (or otherwise coupled to) the exterior of the handle body 40, such as adjacent to the motor 74. The sensor 110 may be non-removably coupled to the handle body 40, such that the sensor is incorporated in the handle body. In another embodiment, the acoustic sensor 110 may be removably attached to the handle body, such as by using a sensor adaptor 174 (e.g., a clip, a clamp, an adhesive) or in other ways. In another example, the acoustic sensor 110 is disposed inside the handle body 40. The acoustic sensor 110 may be coupled to the handle body 40, such as an interior surface of the handle, or one of the components disposed inside the handle (e.g., the motor 74 or the power source 76).

[0046] In another embodiment, the acoustic sensor 110 may be removably or non- removably coupled to the catheter body 22 or a component of the catheter body, such as the drive shaft 36. In one example, the acoustic sensor 110 may be coupled to the exterior of the catheter body 22 adjacent the distal end of the body (e.g., the tip) for example. The acoustic sensor may be disposed at other locations of the catheter 20. Moreover, in one embodiment, the acoustic sensor 110 may not be coupled to the catheter 20, but may be a separate sensor.

[0047] Referring to FIGS. 5 and 6, in one example the acoustic sensor 110, the processor 120, and the memory 130 are incorporated in the handle 34. In this example, the acoustic sensor 110 may be disposed inside the handle body 40 adjacent to the motor 74. In this example, for reasons explained below, a display 170 and / or other visual feedback interface (e.g., an LED 172) may be incorporated in the handle 34.

[0048] Referring to FIG. 7, in another example, the processor 120 and the memory 130 are not incorporated in the handle, but instead may be standalone capital equipment. The acoustic sensor 110 may be incorporated in the handle or configured to be removably secured to the handle body 40, as shown in FIG. 7. For example, the acoustic sensor may be secured to the handle using the sensor adapter 174. The acoustic sensor 110 is in communication with the processor 120 and memory 130 via a wired or wireless connection. In this example, the display 170' may also be separate from the handle 34' and in communication with the processor 120.

[0049] In one or more embodiments, the processor 120 receives the analog signal from the acoustic signal (such as after the signal goes through the pre-amp 160 and the bandpass filter 170) and performs processes on the signal in accordance with the instructions 140 saved in the memory 130. A flowchart illustrated exemplary instructions 140 for execution by the processor 120 is shown in FIG. 14.

[0050] Referring to FIG. 14, at step 144 the acoustic signal processing instructions 24 instruct the processor 120 on processing the received acoustic signals before proceeding to the tissue-type identification instructions 146. In one example, the analog signal from the acoustic sensor 110 (e.g., the amplified and filtered signal) is first sampled at step 144Ato convert the analog signal to a digital signal. For example, the analog signal may be sampled at a rate of 5 megasamples per second (5MSPS). In one example, the analog signal may be continuously sampled (converted to digital signal) and saved to memory130 for analysis by the processor 120. In another example, shown in FIG. 14, only portions of the digital signal are labeled for analysis. This is a "hit-driven" design. The hit-driven design is able to efficiently measure all detected signals and record digital descriptions for each individual feature (detailed later in this section). Once a new signal is meets the pre-defined amplitude (decibel) threshold, the system records the hit or hits, and the data is logged for analysis, as indicated at instruction 144B. As shown in FIG. 15, each hit may include one or more counts or threshold crossings. Suitable, non-limiting parameters for the hit-driven design are described in Example 1, below.

[0051] In one or more embodiments, the sampled or digital acoustic signal waveform data, representing voltages over time, may be further processed by the processor 120. The processor 120, using the signal processing instructions at step 144C, computes the discrete Fourier transform (DFT) of the data using the fast Fourier transform algorithm to convert the data from the time domain (amplitude / time) into the frequency domain (amplitude / frequency). In one or more embodiments, the digital data may be processed to determine peak-to-peak values, which is the maximum voltage plus the absolute value of the minimum voltage. In one more embodiments, one or more of the signal processing steps may be performed.

[0052] The processor, by executing the tissue-type identification instructions 146, analyzes the processed acoustic data from step (e.g., compares FFT data to saved FFT data at step 146A) to determine the type or classification of tissue being engaged by the catheter (at step 146B). In one or more embodiments, the processor 120 is configured (i.e., instructed) to identify atheroma plaque, atheroma calcium, soft tissue (e.g., lumen wall). In one more embodiments, the tissue-type identification instructions 146 are developed using one or more machine-learning models. These machine learning models may be based on supervised learning, unsupervised learning, semi-supervised learning, and / or reinforced learning. Suitable known models include Gradient Boost model using the voltage / time waveform and / or peak-to-peak waveform as input(s), XGBoost model using the voltage / time waveform and / or peak-to-peak waveform and / or the Fourier transformed waveform as input(s), and / or CNN model using the voltage / time waveform as an input. Below are experiments performed using these models and supervised learning in developing tissue-type identification instructions 146.

[0053] Next, the processor, by executing the operational instructions 148, actuates one or more operations of the catheter. In one or more embodiments, at step 148Athe processor 120 is configured (i.e., instructed) to adjust torque of the motor (e.g., adjust voltage applied to the motor) and / or provide user feedback if / when the processor determines that the catheter is engaging (e.g., cutting) the lumen wall. The processor 120 may be configured to a communicate with a PWM 180 (shown in FIG. 12) to adjust the voltage and power supplied to the motor 74. In one example, the processor 120 may be configured to reduce the duty cycle supplied to the motor 74 to 0V, for example, to inhibit the catheter 20 from further damaging the body lumen wall. The catheter 20 may be configured to stop the motor in other ways, such as by applying a brake (e.g., dynamic brake) to the motor or actuating a switch to shut off power to the motor.

[0054] In one or more examples, the processor 120, at step 148B, actuates the indicator 172 for communicating to the user that the processor determined that the catheter 20 (e.g., the rotational tissue-removing element 28) has engaged the lumen wall and the processor is shutting off (or has already shut off), or is reducing the power supplied to, the motor 74. In one example, shown in FIGS. 5 and 6, the indicator 172 is an LED or other light on the handle. In another example, the indicator 172 may be a device that provides tactile or audible feedback to the user. Other types of indicators 172 for communicating to the user that the processor 120 is shutting off the motor 74 (or has already shut off) or is significantly reducing the power supplied to the motor do not depart from the scope of the present disclosure.

[0055] In one or more embodiments that includes the display 170, 170' in communication with the processor 120, the processor, at step 148C, may be configured to display feedback relating to percentages of tissue being engaged by the catheter 20. For example, the processor 120 may display the following percentages relating to tissue being engaged: % of calcium; % of non-calcium plaque; and % of healthy tissue (e.g., body lumen wall). The processor 120 may provide additional information on the display.

[0056] In one or more embodiments, the processor 120, at step 148D, is configured to adjust the torque of the motor 74 based on the type of tissue determined to be engaged by the catheter. For example, the processor 120 may be configured to increase torque applied to the motor 74 (e.g., communicate to PWM 180 to increase the duty cycle) if it is determined that the catheter 20 is engaging calcified plaque. This may help with the cutter28 breaking up the calcified plaque. The processor 120 may be configured to decrease torque applied to the motor 74 (e.g., communicate to PWM 180 to decrease the duty cycle) if it is determined that the catheter 20 is engaging soft tissue of the lesion. This may help with cutter 28 engagement with the soft tissue. Moreover, the processor 120 may be configured to further adjust the torque when it is determined that the cutter 28 is not engaging tissue. This may also help with initial cutter engagement with the lesion.Experimental Example

[0057] An experimental tissue-type detector was developed to test the feasibility of using acoustic signals (e.g., acoustic emissions) of an atherectomy catheter emitted during tissue removal to determine the type of tissue being engaged or cut. The atherectomy catheter used was a directional atherectomy catheter sold by Medtronic under the name HawkOne. Briefly, the catheter includes an electric motor housed in a handle that drive an elongate drive shaft to impart rotation to a cutter at a distal end of a catheter body. The following were additional components / materials used in the experiment: artificial body lumens formed in a plate to mimic blood vessel diameters; 5 types of material to simulate tissue: i) Syndaver cardiac muscle, ii) DragonSkin silicone with shells, iii) DragonSkin silicone with aragonite, iv) Dragon Skin silicone, and v) Syndaver subcutaneous fat; acoustic emission sensor from Physical Acoustics (PICO - 200-750 kHz lightweight miniature AE sensor with integral coaxial cable; 26 dB gain IL-LP preamp (5V) from Physical Acoustics; 20kHz- 1MHz analog bandpass filter with no signal attenuation; a commercially available data acquisition system; a computer; and supervised machine learning models: Gradient Boost, XGBoost, and CNN. An exemplary relationship for the data acquisition method is shown in FIG. 16.

[0058] To train the supervised machine learning models, the AE sensor was attached to the catheter in two different locations. In the first test embodiment, the AE sensor was mounted on the catheter body adjacent the distal end thereof. The AE was mounted using a mount shown in FIG. 17. In the second test embodiment, the AE sensor was mounted on the exterior of the handle. The AE was mounted on the exterior of the handle using wax as shown in FIG. 18. Each embodiment was tested on each of the 5 different materials received in the artificial body lumens. In the first test embodiment, the catheter was "dry" run through the artificial body lumens with the materials and no material received therein (i.e., the artificial body lumens were not submerged in a water bath). In the second testembodiment, the catheter was "wet" run through the artificial body lumen with the materials and no material received therein (i.e., the artificial body lumens were submerged in water bath).

[0059] For each run, the acoustic signal data was recorded in the method shown in FIG. 19. It was assumed that it takes about 5 seconds to complete a run or cut-pass. In general, the acquired data from the sensor was recorded at the beginning of the cut-pass for 5 seconds. The analog signal from the sensor was sampled at 5 megasamples per second. The system used a hit method for logging certain recorded data. The hit settings were as follows:Threshold: 45dBZero gainPeak definition time = lOOusHit lockout time = lOOusHit definition time = 1msMax duration = 1000msWaveform setup: 5MSPS, 128pre-trigger 10k length

[0060] Using the acquired data, each of the supervise machine learning models were trained to determine the accuracy of each model. After training, the tests for each material were run again to determine if the trained processor accurately predicted the type of tissue being cut by the catheter.

[0061] As shown in FIG. 20, it was determined that the handle-mounted sensor performed better in terms of accuracy for both time-based and frequency -based analysis. As shown in FIG. 20, it was determined that XGBoost using Fourier transformed data was the most accurate model for predicting tissue type being cut, although other models were also accurate and may be more accurate if more data is collected. As shown in FIG. 21, it was found that the most important features were in the frequency range of less than 250 kHz and between 700 and 900 KHz. Using data in these frequency ranges provided the most accurate prediction for the type of tissue being cut. Moreover, it was determined that the most important 500 features were collected in the first 0.61 ms of a hit.

[0062] The following examples are a non-limiting list of clauses in accordance with one or more techniques of this disclosure.

[0063] The invention may be further described by reference to the following numbered Examples:

[0064] Example 1. A tissue-removing catheter for removing tissue from a body lumen, the tissue-removing catheter comprising: an elongate catheter body configured for insertion into the body lumen, the catheter body having opposite distal and proximal portions, and a longitudinal axis extending between the distal and proximal portions; a tissue-removing element located generally at the distal portion of the catheter body and configured to rotate about a rotational axis and mechanically remove tissue from the body lumen; a motor operably connected to the tissue-removing element to impart rotation of the tissue-removing element about the rotational axis during a tissue-removing operation of the catheter; and a tissue-type detector including an acoustic sensor configured to sense an acoustic signal emanating from the catheter when the tissue-removing element engages the tissue in the body lumen during the tissue-removing operation of the catheter.

[0065] Example 2. The tissue-removing catheter according to Example 1, wherein the tissue-type detector is configured to sense an acoustic signal emanating from the motor.

[0066] Example 3. The tissue-removing catheter according to any of Examples 1 or 2, wherein the acoustic sensor comprises an acoustic emission sensor.

[0067] Example 4. The tissue-removing catheter according to any of Examples 1 to 3, further comprising a handle having a handle housing in which the motor is disposed, wherein the acoustic sensor is coupled to one of the handle and the catheter body.

[0068] Example 5. The tissue-removing catheter according to Example 4, wherein the acoustic sensor is mounted on an exterior of the handle housing.

[0069] Example 6. The tissue-removing catheter according to Example 5, wherein the acoustic sensor is mounted on an interior of the handle housing.

[0070] Example 7. The tissue-removing catheter according to Example 4, wherein the acoustic sensor is mounted to the catheter body adjacent the distal portion.

[0071] Example 8. The tissue-removing catheter according to any of Examples 1 to 7, wherein the tissue-type detector further includes a processor in communication with the acoustic sensor for receiving a sensed signal indicative of the acoustic signal, and memory storing instructions for execution by the processor.

[0072] Example 9. The tissue-removing catheter according to Example 8, wherein the memory includes stored tissue-type classification instructions, wherein the processor isconfigured to execute the stored tissue-type classification instructions, using the sensed signal from the acoustic sensor, to determine a type of tissue being engaged by the tissueremoving element during the tissue-removing operation of the catheter.

[0073] Example 10. The tissue-removing catheter according to any of Examples 8 or 9, wherein the memory includes stored signal processing instructions, wherein the processor is configured to execute the stored signal processing instruction, using the sensed signal from the acoustic sensor, to transform the sensed signal from time domain to frequency domain.

[0074] Example 11. The tissue-removing catheter according to any of Examples 8 to 10, wherein the tissue-type detector further includes a display in communication with the processor, wherein the memory includes stored operational instructions, the processor configured to execute the stored operational instructions to display the detected types of tissue being engaged by the tissue-removing element.

[0075] Example 12. The tissue-removing catheter according to Example 8, wherein the memory includes stored tissue-type classification instructions, wherein the processor is configured to execute the stored tissue-type classification instructions, using the sensed signal from the acoustic sensor, to determine if the tissue-removing element is engaging a wall of the body lumen during the tissue-removing operation of the catheter.

[0076] Example 13. The tissue-removing catheter according to Example 12, wherein the memory includes stored operational instructions, wherein the processor is configured to execute the stored operational instructions to stop the motor if the processor determines the tissue-removing element is engaging the wall of the body lumen during the tissueremoving operation of the catheter.

[0077] Example 14. A method of using the tissue-removing catheter according to any of Examples 1 to 13, the method comprising: inserting the catheter body into the body lumen, wherein the body lumen is a blood vessel; debulking the blood vessel by driving rotation of the tissue-removing element using the motor; and sensing acoustic signals emanating from the tissue-removing catheter during said debulking.

[0078] Example 15. A tissue-type detector for a tissue-removing catheter of the type including a handle housing a motor that drives a tissue-removing element, the tissue-type detector including: an acoustic sensor configured to be coupled to the handle of the tissueremoving catheter, the acoustic sensor configured to sense an acoustic signal emanatingfrom the tissue-removing catheter during a tissue-removing operation and generate a sensed signals indicative of the acoustic signal; memory including processor-executable instructions, the processor-executable instructions including tissue-type classification instructions; and a processor in communication with the acoustic sensor and the memory, wherein the processor is configured to execute the tissue-type classification instructions to determine a type of tissue being engaged by the tissue-removing element based on the sensed signal from the acoustic sensor.

[0079] Example 16. The tissue-type detector according to Example 15, wherein the processor-executable instructions include signal processing instructions, wherein the processor is configured to execute the signal processing instructions, using the sensed signal from the acoustic sensor, to transform the sensed signal from time domain to frequency domain.

[0080] Example 17. The tissue-removing catheter according to any of Examples 15 to 16, wherein the tissue-type detector further includes a display in communication with the processor, wherein the memory includes stored operational instructions, the processor configured to execute the stored operational instructions to display the detected type of tissue being engaged by the tissue-removing element.

[0081] Example 18. The tissue-removing catheter according to Example 15, wherein the memory includes stored tissue-type classification instructions, wherein the processor is configured to execute the stored tissue-type classification instructions, using the sensed signal from the acoustic sensor, to determine if the tissue-removing element is engaging a wall of the body lumen during the tissue-removing operation of the catheter.

[0082] Example 19. The tissue-removing catheter according to Example 18, wherein the memory includes stored operational instructions, wherein the processor is configured to execute the stored operational instructions to stop the motor if the processor determines the tissue-removing element is engaging the wall of the body lumen during the tissueremoving operation of the catheter.

[0083] Example 20. The tissue-removing catheter according to any of Examples 15 to 19, further comprising a sensor adaptor configured to removably couple the acoustic sensor to the handle.

[0084] It should be understood that various aspects disclosed herein may be combined in different combinations than the combinations specifically presented in the description andaccompanying drawings. It should also be understood that, depending on the example, certain acts or events of any of the processes or methods described herein may be performed in a different sequence, may be added, merged, or left out altogether (e.g., all described acts or events may not be necessary to carry out the techniques). In addition, while certain aspects of this disclosure are described as being performed by a single module or unit for purposes of clarity, it should be understood that the techniques of this disclosure may be performed by a combination of units or modules associated with, for example, a medical device.

[0085] In one or more examples, the described techniques may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored as one or more instructions or code on a computer-readable medium and executed by a hardware-based processing unit. Computer-readable media may include non-transitory computer-readable media, which corresponds to a tangible medium such as data storage media (e.g., RAM, ROM, EEPROM, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer).

[0086] Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Accordingly, the term “processor” as used herein may refer to any of the foregoing structure or any other physical structure suitable for implementation of the described techniques. Also, the techniques could be fully implemented in one or more circuits or logic elements.

Claims

CLAIMS:

1. A tissue-removing catheter (20) for removing tissue from a body lumen, the tissueremoving catheter comprising: an elongate catheter body (22) configured for insertion into the body lumen, the catheter body (22) having opposite distal and proximal portions, and a longitudinal axis extending between the distal and proximal portions; a tissue-removing element (28) located generally at the distal portion of the catheter body (22) and configured to rotate about a rotational axis and mechanically remove tissue from the body lumen; a motor (74) operably connected to the tissue-removing element (28) to impart rotation of the tissue-removing element (28) about the rotational axis during a tissueremoving operation of the tissue-removing catheter (20); and a tissue-type detector (100) including an acoustic sensor (110) configured to sense an acoustic signal emanating from the tissue-removing catheter (20) when the tissueremoving element (28) engages the tissue in the body lumen during the tissue-removing operation of the tissue-removing catheter (20).

2. The tissue-removing catheter (20) according to claim 1, wherein the tissue-type detector (100) is configured to sense an acoustic signal emanating from the motor (74).

3. The tissue-removing catheter (20) according to any of claims 1 or 2, wherein the acoustic sensor (110) comprises an acoustic emission sensor.

4. The tissue-removing catheter (20) according to any of claims 1 to 3, further comprising a handle (34, 34') having a handle body (40) in which the motor (70) is disposed, wherein the acoustic sensor (110) is coupled to one of the handle body (40) and the catheter body (22).

5. The tissue-removing catheter (20) according to claim 4, wherein the acoustic sensor (110) is mounted on an exterior of the handle body (40).

6. The tissue-removing catheter (20) according to claim 5, wherein the acoustic sensor (110) is mounted on an interior of the handle body (40).

7. The tissue-removing catheter (20) according to claim 4, wherein the acoustic sensor (110) is mounted to the catheter body (22) adjacent the distal portion.

8. The tissue-removing catheter (20) according to any of claims 1 to 7, wherein the tissue-type detector (100) further includes a processor (120) in communication with the acoustic sensor (110) for receiving a sensed signal indicative of the acoustic signal, and memory (130) storing instructions for execution by the processor (120).

9. The tissue-removing catheter (20) according to claim 8, wherein the memory (130) includes stored tissue-type classification instructions, wherein the processor (120) is configured to execute the stored tissue-type classification instructions, using the sensed signal from the acoustic sensor (110), to determine a type of tissue being engaged by the tissue-removing element (28) during the tissue-removing operation of the tissue-removing catheter (20).

10. The tissue-removing catheter (20) according to any of claims 8 or 9, wherein the memory (130) includes stored signal processing instructions, wherein the processor (120) is configured to execute the stored signal processing instruction, using the sensed signal from the acoustic sensor (110), to transform the sensed signal from time domain to frequency domain.

11. The tissue-removing catheter (20) according to any of claims 8 to 10, wherein the tissue-type detector (100) further includes a display (170) in communication with the processor (120), wherein the memory (130) includes stored operational instructions, the processor (120) configured to execute the stored operational instructions to display the detected types of tissue being engaged by the tissue-removing element (28).

12. The tissue-removing catheter (20) according to claim 8, wherein the memory (130) includes stored tissue-type classification instructions, wherein the processor (120) isconfigured to execute the stored tissue-type classification instructions, using the sensed signal from the acoustic sensor (110), to determine if the tissue-removing element (28) is engaging a wall of the body lumen during the tissue-removing operation of the tissueremoving catheter (20).

13. The tissue-removing catheter (20) according to claim 12, wherein the memory (130) includes stored operational instructions, wherein the processor (120) is configured to execute the stored operational instructions to stop the motor (74) if the processor determines the tissue-removing element (28) is engaging the wall of the body lumen during the tissue-removing operation of the tissue-removing catheter (20).

14. A tissue-type detector (100) for a tissue-removing catheter (20) of the type including a handle (34, 34') housing a motor (74) that drives a tissue-removing element (28), the tissue-type detector (100) comprises: an acoustic sensor (110) configured to be coupled to the handle (34, 34') of the tissue-removing catheter (20), the acoustic sensor (110) configured to sense an acoustic signal emanating from the tissue-removing catheter (20) during a tissue-removing operation and generate a sensed signals indicative of the acoustic signal; memory (130) including processor-executable instructions, the processorexecutable instructions including tissue-type classification instructions; and a processor (120) in communication with the acoustic sensor (110) and the memory (130), wherein the processor (120) is configured to execute the tissue-type classification instructions to determine a type of tissue being engaged by the tissueremoving element (28) based on the sensed signal from the acoustic sensor (110).

15. The tissue-type detector (100) according to claim 14, wherein the processorexecutable instructions include signal processing instructions, wherein the processor (120) is configured to execute the signal processing instructions, using the sensed signal from the acoustic sensor (110), to transform the sensed signal from time domain to frequency domain.

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