Wireless retracement distance sensor for IVUS system

Abstract

The present invention relates to intravascular techniques, such as intravascular ultrasound (IVUS) imaging, in which retracement distance measurements are important. Hardware, circuit architecture, and methods are described for wirelessly transmitting data related to the retraction distance of a catheter introduced into a blood vessel.

Description

Related Application Data

[0001] This application claims priority to U.S. Provisional Patent Application Serial No. 63 / 464,338, filed May 5, 2023, entitled “Wireless Pullback Distance Sensor,” the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0002] The present disclosure relates to intravascular ultrasound (IVUS), and more specifically, to systems and methods for measuring IVUS catheter pullback distance. BACKGROUND

[0003] Intravascular ultrasound (IVUS) is an imaging method used to assess vascular pathology and guide vascular interventions. IVUS is particularly valuable for coronary percutaneous intervention (PCI) because assessment of plaque and procedural guidance can be difficult when using only coronary angiography. Coronary IVUS was first commercialized in the early 1990s. The technology has steadily improved, and a large body of clinical evidence has accumulated supporting the benefits of IVUS for PCI. U.S. Patent No. 8,864,674 (Corl), entitled “Circuit Architecture and Electrical Interface for Rotational Intravascular Ultrasound (IVUS) Devices,” which is incorporated herein by reference in its entirety, describes an example of a conventional IVUS system. The additional imaging information provided by IVUS, such as identifying the presence and extent of plaque, more accurate vessel size measurements, external elastic membrane (EEM) measurements, and stent deployment assessment, has the potential to improve the safety of stent implantation, including optimizing the length of the vessel that needs stenting, selecting stent landing zones, and identifying lesions with higher risk of distal embolization during stent implantation. IVUS has been shown to be able to identify high-risk lesions, which also helps to implement strategies to prevent future coronary events. Clinical studies have shown that treatment decisions for individual patients are complex and often uncertain. Clinicians face challenging decisions every day that involve revascularization strategies (e.g., PCI versus bypass surgery) and important procedural issues regarding the likelihood of PCI success (e.g., identifying lesions that need treatment, length of vessel that needs treatment, optimal stent deployment, risk of distal embolization, and peri-procedural myocardial infarction (MI), among others).

[0004] While the vast majority of PCI procedures in the United States are performed under only angiographic guidance, coronary angiography alone does not provide sufficient information for these complex decisions. Importantly, since the angiogram is created by the transient flow of contrast in the artery, coronary angiography only shows the lumen of the vessel. Any information about the vessel wall (e.g., plaque burden) is not shown. Size accuracy is also limited due to low spatial resolution and many sources of image artifact (e.g., vessel tortuosity away or toward the detector). For quantitative determination of parameters (e.g., degree of stenosis) that determine whether to intervene, angiography is notorious for its highly variable interpretation. While angiography is an important tool for depicting the gross presence of disease and rough quantification of stenosis, it underestimates the extent of atherosclerosis, particularly in the early stages of disease where positive remodeling of the vessel can keep the lumen normal in size despite extensive plaque development in the vessel wall. Importantly, angiography also has significant limitations in accurately measuring plaque structure, providing no data on plaque composition beyond a rough estimate of calcification. Selection and placement of drug eluting coronary stents (DES) based on angiographic information alone has been shown to increase complications and lead to worse outcomes compared to IVUS guided PCI.

[0005] IVUS guided PCI has been shown to reduce stent complications (dissection, stent thrombosis or edge restenosis), geographic misplacement of the stent (stent ends in the diseased area or other non-optimal locations), and incomplete or malapposition of the stent expansion. As a comprehensive example of evidence, a meta-analysis of 11 studies comprising 19,619 patients demonstrated the superiority of direct coronary imaging compared to angiographic guidance in facilitating PCI. Another important study showed that IVUS guidance changed the clinician's decision in more than 75% of cases, leading to the use of longer, better sized and more effective stent deployment. Repeated studies have shown a relative risk reduction of more than 50% in the composite endpoint of cardiac death, myocardial infarction and stent thrombosis with PCI performed under IVUS guidance.

[0006] Atherosclerotic lesions exhibiting characteristics indicating an impending rupture tendency, known as vulnerable plaques, are of particular interest to interventional cardiologists and are considered a cause of most heart attacks. The in vitro pathological counterpart to vulnerable plaques is thin-cap fibroadenoma (TCFA), characterized by a large necrotic core and a thin (<65 μm) fibrous cap. Therefore, to begin interpreting potentially vulnerable plaques, an IVUS system must first possess sufficient contrast and tissue boundary differentiation (e.g., blood, luminal boundaries, external elastic lamina, thrombus, calcification, etc.) to quantify the so-called plaque burden (plaque size) to infer whether the plaque contains a necrotic core, and then the resolution must be sufficient (e.g., <50 μm) to observe the thin-cap region. Even the best IVUS systems currently available only offer moderate image quality, which may limit the ability to identify vulnerable plaques. The same image quality parameters associated with plaque characterization that predict patients’ long-term future event risk are also directly important for guiding patient procedures (precise stent placement relative to plaque location, stent size, confirmation of successful stent deployment, or assessment of stent healing during follow-up catheterization).

[0007] As previously mentioned, the measurement of lesion length and related parameters defined by the longitudinal position of the vessel are crucial. There are two basic types of catheters on the market—catheters with a single transducer element and a rotating, retractable core, and catheters with a multiplexed transducer array at the tip. Single-transducer rotating core catheters achieve cross-sectional image frames through high-speed rotation (typically 1800 RPM or 30 frames / second) and create volumetric images by retracting the core (so-called “retraction”) while continuing to acquire frames. The retraction length is tracked in the motor-driven unit by digitizing the distance the core is retracted relative to the sheath. Retraction information is transmitted to the console and image processing code via a wired connection between the motor-driven unit and the console. Catheters with a multiplexed transducer array at the tip (“phased array” catheters) generate images through a sequence of excitation and detection of cyclically arranged transducers to create virtual rotations and corresponding frames. Volumetric images are obtained by retracting the entire catheter from the vessel while continuing to acquire frames. Commercial retraction devices have long been notorious for their significant accuracy and variability issues. Summary of the Invention

[0008] In one embodiment, this disclosure relates to a retraction distance sensor for an intravascular ultrasound (IVUS) system. The sensor includes: a housing defining a central opening through which an IVUS catheter passes; a linear motion sensor disposed together with the housing, configured to detect motion of the IVUS catheter as it moves through the central opening of the housing; and a wireless communication device disposed together with the housing, communicating with the linear motion sensor to receive and wirelessly transmit signals representing the motion of the IVUS catheter detected by the linear motion sensor.

[0009] In another embodiment, this disclosure relates to an intravascular ultrasound (IVUS) system comprising: an IVUS patient interface module; an IVUS catheter extending from the patient interface module; an IVUS catheter introducer configured to receive the IVUS catheter; and a retraction distance sensing unit configured to be disposed around the IVUS catheter and generate a wireless signal indicating a retraction distance, wherein the wireless signal is received by an IVUS system controller.

[0010] In yet another embodiment, this disclosure relates to a method for measuring retraction distance in an intravascular ultrasound (IVUS) system, comprising: placing a retraction distance sensing unit housing around an IVUS catheter; pulling the IVUS catheter through the retraction distance sensing unit; detecting the travel distance of the IVUS catheter through the retraction distance sensing unit housing using at least a linear motion sensor disposed together with the unit housing; and wirelessly transmitting a signal indicating the travel distance from the retraction distance sensing unit housing to an IVUS system controller. Attached Figure Description

[0011] To illustrate this disclosure, the accompanying drawings show aspects of one or more embodiments of the disclosure. However, it should be understood that this disclosure is not limited to the precise arrangements and apparatus shown in the drawings, wherein:

[0012] Figure 1 is a schematic diagram of an IVUS system according to the present disclosure.

[0013] Figure 2 is a detailed view of a motion sensing and transmitting unit according to one embodiment of the present disclosure.

[0014] Figure 3 is a schematic diagram of the operation of a motion sensing and transmitting unit according to an embodiment of the present disclosure.

[0015] Figure 4 is a sensor communication block diagram according to one embodiment of the present disclosure.

[0016] Figure 5 is a schematic end view of an alternative embodiment of the sensing unit according to the present disclosure. Detailed Implementation

[0017] The IVUS system and method described herein include a motion sensing and transmitting unit configured to provide more accurate retraction measurements with higher accuracy and repeatability. Embodiments described herein and shown in the accompanying drawings include, but are not limited to: sensing the retraction position of the catheter via a small, disposable accessory connected to the Luer lock connector of the inserter, and continuously and wirelessly transmitting the information back to a motor-driven unit, wherein the sensing can be one or more of the following: purely optical (reflecting light from the side of the catheter), a wheel that contacts the catheter and rotates with the longitudinal movement of the catheter and has a slit disc with optical measurements, and / or the catheter may have graduations printed on its side to improve sensor accuracy; the sensor circuitry and digitization may be performed via an ASIC.

[0018] As shown in Figure 1, a system embodiment according to this disclosure includes a patient interface module (PIM) 10, which may include an IVUS motor drive unit and a communication device (not shown) such as a Wi-Fi, custom radio, or Bluetooth module. An IVUS catheter 12 extends from the PIM 10, passing through a sensing unit 14 and a vascular applicator 16. In some embodiments, the sensing unit and the applicator are connected via a conventional Luer lock connector 18. The sensing unit 14 may include a connector 19 at one end that can be connected to the Luer lock connector 18. The catheter 12 extends distally from the applicator needle 20. The vascular applicator 16 also includes a saline / flushing line 22 as known in the art. The motion sensing unit 14 includes a motion sensing element 24 and a communication device 26, which are respectively disposed with, on, or within the housing of the sensing unit 14. The communication device 26 generates a wireless communication signal 28. The wireless communication signal 28 may be directionally transmitted to and received by the PIM 10, or may be received by an IVUS console (not shown) that includes system processing and image display to the operator, as is also known in the art.

[0019] Sensing element 24 detects the movement of the IVUS catheter as it passes through the sensing element, such as by sliding or translational motion, and can take many different forms. For example, as shown in FIG2, in one embodiment, it includes a combination of a linear motion sensor and a triaxial accelerometer. In other embodiments, it may include only a linear motion sensor. Examples of linear motion sensors include mechanical sensors, such as a wheel or encoder wheel in contact with the catheter that rotates with the longitudinal movement of the catheter, the rotation of the wheel being sensed optically or by other rotational position / sensing methods that can be configured by those skilled in the art. Other known linear motion / position sensing devices, such as magnetic, inductive, capacitive, or eddy current sensing, can be used in conjunction with appropriate sensing processing on or within the outer surface of the catheter 12. Magnetic distance sensors convert magnetic energy into electronic signals. Inductive linear sensors use electromagnetic induction to detect displacement. Capacitive sensors use dielectric materials to detect motion. Eddy currents can utilize any metal sheet and can detect any distance or change in the movement of the metal sheet. The linear motion sensor of sensing element 24 is configured to detect the amount and direction of longitudinal movement of the catheter 12 through sensing unit 14, such as during retraction during the creation of an IVUS image. In an embodiment where a triaxial accelerometer is also employed in the sensing element 24, longitudinal motion information is combined with triaxial accelerometer information that detects the three-dimensional motion of the sensing unit 14 to detect longitudinal catheter motion and potential displacement of the sensing unit 14 during the surgical procedure.

[0020] In one example, as shown in Figure 3, the linear sensor of sensing element 24 may include a transmitter / detector pair 30, such as an optical sensor in an optical computer pointing device (like a mouse). In this embodiment, sensor 30 uses the surface texture of the conduit as a guide for calculating displacement and is capable of providing micron-level displacement information. In some embodiments, as shown in Figure 3, scale markings 32 may be provided on conduit 12 to improve optical sensing sensitivity and accuracy and can be used to correct for sudden slippage. When included in sensing element 24 along with optical sensor 30, a triaxial accelerometer further collects information indicating the three-dimensional motion of sensing unit 14. To improve the accuracy of three-dimensional motion sensing, the accelerometer may include a triaxial gyroscope and a triaxial compass. Such a triaxial accelerometer may be configured as a MEMS device.

[0021] In some implementations, as shown in FIG4, an optional signal processor 34 may be included within the motion sensing unit 14. For example, the processor 34 may be configured to amplify the output of the sensing element 30 and digitize the signal when the sensing element 30 generates an analog output signal. For example, the processor 34 may be a Bluetooth® or Bluetooth® Low Energy (BLE) wireless microcontroller unit (MCU). In one implementation, those skilled in the art may implement the processor 34 as an ASIC based on the teachings herein. The processor 34 may also combine information from all the sensors in unit 14 to extract the exact amount of displacement of the catheter stylet and inserter needle relative to each other and calculate the accurate displacement of the catheter stylet relative to the blood vessel. This information can be used to generate the retraction length and may eliminate the need for a separate IVUS electric retraction device in some implementations. Alternatively, the processor 34 may be omitted, and the raw linear displacement and three-dimensional sensor information may be transmitted as is. In this configuration, the raw information will be processed by a wireless system console (not shown) to generate the aforementioned catheter displacement information.

[0022] The sensing unit 14 can be configured as an inexpensive, disposable, add-on device, easily adaptable to existing IVUS systems by connecting the Luer lock connector 18 before the insertion catheter 12. Using the sensing unit 14 allows for greater control and more accurate understanding of catheter position and retraction distance than current systems. The wireless communication signal 28 from the communication device 26 can be directionally transmitted to and received by the interface unit / motor drive unit 10, or received by a wireless system console (not shown) that includes system processing and image display to the operator. The sensing unit 14 can also be used in conjunction with an electric retraction unit (not shown), whether or not the wireless communication of the sensing signal 28 is directly with the retraction unit. In some embodiments, it may be necessary to operate the electric retraction unit under feedback control from the sensing unit 14.

[0023] In another alternative embodiment, as shown in Figure 5, the sensing unit 14 may have a longitudinal opening 36 that can be closed by a cover or door 38 to allow the sensing unit to be placed on and removed from the catheter 12 without removing the catheter from the inserter. In another alternative, the sensing unit 14 may be detached from the vascular inserter 16 and Luer lock connector 18 (or any other relatively fixed structure) and instead held by the operator during catheter 12 retraction. With the sensing unit 14 held by hand, the accelerometer of the sensing element 24 can be used to process movements in the operator's hand that may affect the retraction measurement of the linear motion sensor.

[0024] The foregoing content is a detailed description of the illustrative embodiments of this disclosure. It should be noted that, unless specifically stated or indicated, in this specification and the appended claims, the conjunction language used in phrases such as "at least one of X, Y, and Z" and "one or more of X, Y, and Z" should be understood to mean that each item in the conjunction list can exist alone in any number, excluding any other items in the list, or can exist in any number in combination with any other or all items in the conjunction list, wherein each item can also exist in any number. Applying this general rule, in the foregoing example, the conjunction phrases consisting of X, Y, and Z in the conjunction list should each include: one or more X; one or more Y; one or more Z; one or more X and one or more Y; one or more Y and one or more Z; one or more X and one or more Z; and one or more X, one or more Y, and one or more Z.

[0025] Various modifications and additions may be made without departing from the spirit and scope of this disclosure. The features of the various embodiments described above may be suitably combined with features of other described embodiments to provide multiple combinations of features in related new embodiments. Furthermore, while many individual embodiments have been described in the foregoing, what is described herein is merely an illustration of the application of the principles of this disclosure. Additionally, although specific methods may be shown and / or described herein in a particular order, the ordering in implementing this disclosure is highly variable within the scope of ordinary art. Therefore, this description is by way of example only and does not otherwise limit the scope of this disclosure.

[0026] Exemplary embodiments have been disclosed above and described in the accompanying drawings. Those skilled in the art will understand that various changes, omissions, and additions can be made to the specific disclosure herein without departing from the spirit and scope of this disclosure.

Claims

1. A retraction distance sensor for an intravascular ultrasound system (IVUS), comprising: A housing that defines a central opening through which an IVUS catheter passes; A linear motion sensor is disposed together with the housing, the linear motion sensor being configured to detect the movement of the IVUS catheter as it moves through the central opening of the housing; as well as A wireless communication device is provided together with the housing, which communicates with the linear motion sensor to receive and wirelessly transmit signals representing the IVUS catheter movement detected by the linear motion sensor.

2. The retraction distance sensor according to claim 1 further includes an acceleration sensor disposed together with the housing and communicating with the wireless communication device, wherein, The accelerometer generates three-dimensional position information relative to the housing, which is wirelessly transmitted by the communication device.

3. The retraction distance sensor according to claim 1 or 2 further includes a connecting connector disposed at one end of the housing around the central opening, the connecting connector being used to allow connection to a connector or hub of an IVUS system inlet.

4. The retraction distance sensor according to claim 1 or 2, wherein, The housing also defines a configuration that allows the housing to be placed on the IVUS catheter, and includes a closure for the longitudinal opening.

5. The retraction distance sensor according to claim 4, wherein, The housing is configured as a handheld housing.

6. The retraction distance sensor according to claims 1 to 5, wherein, The linear motion sensor includes a wheel configured to contact the IVUS duct as it is pulled through the housing.

7. The retraction distance sensor according to claims 1 to 5, wherein, The linear motion sensor includes an optical sensor configured to detect surface motion of the IVUS catheter as it is pulled through the housing.

8. The retraction distance sensor according to claim 7, wherein, The optical sensor includes a transmitter-detector pair.

9. The retraction distance sensor according to claim 7 or 8, wherein, The graduation marks are set on the surface of the IVUS catheter.

10. The retraction distance sensor according to claims 1 to 5, wherein, The linear motion sensor includes a magnetic linear position sensor, and the IVUS catheter includes one or more magnetic elements along its length.

11. The retraction distance sensor according to claims 1 to 5, wherein, The linear motion sensor includes a linear position sensor, and the IVUS conduit includes a magnetic core or magnetic element along its length.

12. The retraction distance sensor according to claims 1 to 5, wherein, The linear motion sensor includes a capacitive linear position sensor, and the IVUS conduit includes a dielectric material such as ceramic or glass along its length.

13. The retraction distance sensor according to claims 1 to 5, wherein, The linear motion sensor includes an eddy current linear position sensor, and the IVUS conduit includes conductive metal strips or strip-shaped elements along its length.

14. The retraction distance sensor according to any one of the preceding claims further includes a signal processor disposed together with the housing, the signal processor communicating at least with the linear motion sensor and the wireless communication device, wherein, The signal processor is configured to determine the retraction distance of the IVUS catheter based on input from the sensor.

15. The retraction distance sensor according to claim 14, wherein, The signal processor is configured to receive acceleration sensing signals from the accelerometer to determine the three-dimensional motion of the housing.

16. An intravascular ultrasound system (IVUS) comprising: IVUS patient interface module; IVUS catheter extending from the patient interface module; An IVUS catheter introducer configured to receive the IVUS catheter; A retraction distance sensing unit is configured to be positioned around the IVUS catheter and generate a wireless signal indicating the retraction distance, wherein the wireless signal is received by the IVUS system controller.

17. The intravascular ultrasound system (IVUS) according to claim 16, wherein, The IVUS system controller that receives the wireless signal includes the IVUS patient interface module.

18. The intravascular ultrasound system (IVUS) according to claim 17, wherein, The IVUS system controller also includes an IVUS console, which additionally or alternatively receives the wireless signal.

19. The intravascular ultrasound system (IVUS) according to any one of claims 16 to 18, wherein, The retraction distance sensing unit includes: A housing defined and configured to slidably receive a central opening through which the IVUS catheter passes; A linear motion sensor, disposed together with the housing, is configured to detect movement of the IVUS catheter as it moves through the central opening of the housing; and A wireless communication device is provided together with the housing, which communicates with the linear motion sensor to receive and wirelessly transmit signals representing the IVUS catheter movement detected by the linear motion sensor.

20. The intravascular ultrasound system (IVUS) according to claim 19, wherein, The retraction distance sensing unit further includes an accelerometer sensor disposed together with the housing and communicating with the wireless communication device, wherein the accelerometer sensor generates three-dimensional position information relative to the housing, and the three-dimensional position information is wirelessly transmitted by the communication device.

21. The intravascular ultrasound system (IVUS) of claim 19 or 20 further includes a connector disposed at one end of the housing surrounding the central opening, the connector being configured to allow direct or indirect connection to the IVUS catheter introducer.

22. The intravascular ultrasound system (IVUS) according to claim 19 or 20, wherein, The housing also defines a configuration that allows the housing to be placed on the IVUS catheter, and includes a closure for the longitudinal opening.

23. The intravascular ultrasound system (IVUS) according to claim 22, wherein, The retraction distance sensing unit is configured as a handheld unit.

24. The intravascular ultrasound system (IVUS) according to any one of claims 19 to 23, wherein, The linear motion sensor includes a wheel configured to contact the IVUS duct as it is pulled through the housing.

25. The intravascular ultrasound system (IVUS) according to any one of claims 19 to 23, wherein, The linear motion sensor includes an optical sensor configured to detect surface motion of the IVUS catheter as it is pulled through the housing.

26. A method for measuring the retraction distance in an intravascular ultrasound (IVUS) system, comprising: Place the retraction distance sensing unit housing around the IVUS catheter; The IVUS catheter is pulled through the retraction distance sensing unit; At least a linear motion sensor, which is provided together with the unit housing, is used to detect the travel distance of the IVUS catheter through the retraction distance sensing unit housing; as well as The retraction distance sensing unit housing wirelessly transmits a signal indicating the travel distance to the IVUS system controller.

27. The method according to claim 26, wherein, The IVUS system controller includes one or both of an IVUS console and an IVUS patient interface module.

28. The method of claim 26 or 27, further comprising directly or indirectly connecting the retraction distance sensing unit housing to the IVUS catheter inserter to place the IVUS catheter within the patient's vascular system.

29. The method of claim 26 or 27, further comprising, during at least the pulling and detection steps, having the retraction distance sensing unit housing held by a system operator's hand.

30. The method according to any one of claims 26 to 29, further comprising processing signals from at least the linear motion sensor within the housing of the retraction distance sensing unit to determine the retraction distance, and wirelessly transmitting the determined retraction distance.

31. The method of claim 30, further comprising processing signals from a triaxial accelerometer included together with the linear motion sensor to determine three-dimensional motion of the retraction distance sensing unit housing, and optionally correcting the determined retraction distance based on the determined three-dimensional motion.

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