Ultrasound catheter

Abstract

An ultrasound catheter is disclosed. The ultrasound catheter includes a micro-electro-mechanical (MEMS)-based piezoelectric micromachined ultrasound transducer (pMUT) array disposed within the distal end of the body. The ultrasound catheter also includes a plurality of electronic flex circuits, one end of which is connected to the handle connector and the other end of which is connected to the first layer of the AIC. The handle connector communicates ultrasonic signals to the distal end via a plurality of electronic flex circuits. Further, a distal pMUT interposer is disposed between the first layer and the second layer of the AIC, with an InvisiVia connection. The InvisiVia connection is configured to bring the electronic flex circuit from one side of the distal pMUT interposer to the other side. In addition, the MEMS-based pMUT array transmits pressure waves and receives returned pressure wave echoes via the InvisiVia connection of the distal pMUT interposer.

Description

Technical Field

[0001] The present disclosure generally relates to the field of ultrasound catheters. More specifically, some embodiments relate to ultrasound catheters having a distal piezoelectric micromachined transducer (pMUT) interposer with a connection referred to as "InvisiVia" for transmitting and receiving acoustic pulse information. Background Art

[0002] Recently, the use of catheter-based structures and electrophysiological procedures has expanded to more complex scenarios where precise definition of variable individual cardiac anatomies is key to obtaining optimal outcomes. Intracardiac echocardiography (ICE) is a unique imaging modality for high-resolution real-time visualization of cardiac structures, continuous monitoring of catheter position within the heart, and early identification of procedural complications such as pericardial effusion or thrombus formation. Additionally, the ICE imaging modality includes additional benefits such as excellent patient tolerance, reduced fluoroscopy time, and the need for neither general anesthesia nor secondary surgery. Currently, the ICE imaging modality has largely replaced transesophageal echocardiography as the preferred imaging modality for guiding certain procedures such as atrial septal defect closure and catheter ablation of arrhythmias, and plays an emerging role in other procedures including mitral valvuloplasty, transcatheter aortic valve replacement, and left atrial appendage closure.

[0003] ICE catheters involve the interconnection of multi-dimensional transducer arrays with electronic devices. A technical challenge for multi-dimensional transducer arrays is to create a secure and stable interconnection between the acoustic array and the associated echoes. With hundreds of different elements distributed two-dimensionally, some elements surrounded by other elements require interconnections along the z-axis (depth or range). Due to the small size of the elements, there is limited space for individually electrically connecting to each element. There are various ways to provide interconnections for multi-dimensional transducer arrays, such as chip-on-array, frame-based approaches, and multi-layer flex. In chip-on-array, the acoustic array is directly built on the input / output (I / O) of an application-specific integrated circuit (ASIC) chip. Due to possible failures in the acoustic array, very low process yields may result.

[0004] In frame-based approaches, the array is divided into several sections. Each section has a robust metal frame. Flexible circuits bent around the metal frame redistribute as many signals from the acoustic elements to the ASIC placed on the flexible circuit as there are acoustic elements. However, the signal routing in frame-based approaches is more complex than chip-on-array, resulting in higher electrical parasitics. In multi-layer flex approaches, the stack can be divided into flexible circuits to route signals to the elements without any hole segmentation. However, these approaches either ultimately result in an expensive interconnection structure for the multi-dimensional transducer array or there is some undesirable leakage to the bulk part substrate of the transducer array.

[0005] Accordingly, there is a need for an improved ultrasound catheter having a high density flexible circuit with electrically insulating interconnects for highly repeatable and stable signal transmission. SUMMARY OF THE INVENTION

[0006] As an introduction, the preferred embodiments described below include an easy-to-use ultrasound catheter. The ultrasound catheter includes a body having a longitudinal axis, a proximal end, and a distal end. Additionally, the ultrasound catheter includes a microelectromechanical systems (MEMS)-based piezoelectric micromachined ultrasonic transducer (pMUT) array disposed within the distal end of the body. The ultrasound catheter further includes a plurality of electronic flexible circuits having one end connected to a handle connector and the other end connected to a first layer of an adhesive interconnect (AIC). The handle connector transmits ultrasound signals to the distal end via the plurality of electronic flexible circuits. Additionally, the ultrasound catheter includes a distal pMUT interposer disposed between the flexible circuit layer and a second layer of anisotropic conductive film (ACF) or AIC-like, which we refer to as an "InvisiVia" connection.

[0007] The InvisiVia feature provides a conductive interconnect from one side of the flexible circuit to the other side of the flexible circuit. Thus, InvisiVia creates a flat and planar interconnect from the flexible circuit to the flexible pad by way of a thermo-piezoelectric connection. Additionally, the MEMS-based pMUT array receives an electronic pulse through the flexible circuit and through the conductive InvisiVia to the pMUT, generating a pressure wave, and the returning pressure wave stimulates the pMUT, creating a returning electrical signal through the conductive InvisiVia connection of the distal pMUT interposer.

[0008] It can be noted that the distal pMUT interposer corresponds to an ultra-high density interconnect (UHDI) flexible circuit interposer connected to the MEMS-based pMUT array through a UHDI pad array. The UHDI pad array is connected to the MEMS-based pMUT array by using near-zero evidence interface vias. Additionally, the use of conductive InvisiVia connections creates a higher percentage of flat and planar conductive surface area on the UHDI pads. In one embodiment, the InvisiVia connection creates a flat and planar interconnect diameter of less than 15 microns. Thus, the use of InvisiVia connections eliminates the possibility of unwanted surface topography, creates a larger percentage of conductive surface, and helps prevent leakage to the bulk silicon substrate of the MEMS-based pMUT array.

[0009] Other features and aspects of the present disclosure will become apparent from the following description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Various embodiments will be described below with reference to the accompanying drawings, which are used for illustration and do not limit the scope of the present disclosure in any way, where like reference numerals represent like elements, and wherein:

[0011] Figure 1 A perspective view of an ultrasonic catheter according to an embodiment of the present disclosure is shown;

[0012] Figure 2 A schematic front view of an ultrasonic catheter according to an embodiment of the present disclosure is shown;

[0013] Figure 3 A side - view stack showing an electronic flexible connection to a micro - electromechanical (MEMS) based piezoelectric micromachined ultrasonic transducer (pMUT) array or other type of transducer through one or more layers of adhesive - interconnect (AIC) such as anisotropic conductor film (ACF), anisotropic conductive paste (ACP) or similar anisotropic conductive adhesives (AC.As) or through a conductive epoxy adhesive (ECA) or other such conductive adhesives is shown;

[0014] Figure 4A A side view of an InvisiVia or blind - via connection shape according to an embodiment of the present disclosure is shown;

[0015] Figure 4B An InvisiVia connection with a flat and planar interconnect from a flexible circuit to a highly flat attachment land / pad surface according to an embodiment of the present disclosure is shown;

[0016] Figure 4C A three - dimensional view of an InvisiVia connection disposed within a distal pMUT interposer according to an embodiment of the present disclosure is shown;

[0017] Figure 5 A schematic view of a first layer of AIC that connects a plurality of electronic flexible circuits to a distal pMUT interposer according to an embodiment of the present disclosure is shown;

[0018] Figure 6 An interconnect diagram of a top - view stack of an InvisiVia connection through a second layer of AIC to a MEMS - based pMUT array according to an embodiment of the present disclosure is shown;

[0019] Figure 7 A schematic view showing an AIC layer connecting a distal pMUT interposer to a MEMS - based pMUT according to an embodiment of the present disclosure is shown; and

[0020] Figures 8 to 9 A cross - sectional image of a heart is shown, wherein the ultrasonic catheter is positioned within the right atrium of the heart, according to an embodiment of the present disclosure. Detailed implementation manners

[0021] The components of the embodiments generally described and illustrated in the accompanying drawings herein can be arranged and designed in a variety of different configurations. Thus, as represented in the figures, the following more detailed description of the various embodiments is not intended to limit the scope of the present disclosure, but merely represents the various embodiments. Although aspects of the embodiments are presented in the drawings, unless otherwise indicated, the drawings are not necessarily drawn to scale.

[0022] Some embodiments of the present disclosure will now be discussed in detail, which illustrate all features of the present disclosure. Words such as "including", "having", "containing", and "comprising" and their other forms are intended to be equivalent and are open, because one or more items following any of these words do not mean an exhaustive list of these one or more items, nor are they limited to the listed one or more items.

[0023] It must also be noted that, unless the context otherwise requires, the singular forms "a", "an", and "the" used in this specification and the appended claims include plural references. Although any systems and methods similar or equivalent to those described herein may be used in the practice or testing of the embodiments of the present disclosure, the preferred systems and methods are now described. The terms "proximal" and "distal" are opposite directional terms. For example, the distal end of a device or component is the end of the component that is farthest from the physician during normal use. The proximal end refers to the opposite end, or the end that is closest to the physician during normal use.

[0024] Embodiments of the present disclosure will be described more fully hereinafter with reference to the accompanying drawings, in which like numerals refer to like elements throughout several views, and in which example embodiments are shown. However, the embodiments of the present disclosure may be embodied in alternative forms and should not be construed as limited to the embodiments set forth herein. The examples set forth herein are non-limiting examples and are merely examples among other possible examples.

[0025] Figure 1 A perspective view of an ultrasonic catheter 100 according to an embodiment of the present disclosure is shown. The ultrasonic catheter 100 may include a body 102 having a longitudinal axis 104, a proximal end 106, and a distal end 108, a handle assembly 110, a steering control unit 112 having a steering handle 114 and a housing 116, and a distal tip 118.

[0026] The handle assembly 110 can be positioned between the proximal end 106 and the distal end 108 of the ultrasound catheter 100. Additionally, the steering control unit 112 can be positioned within the handle assembly 110. The steering control unit 112 can be provided for articulating the distal tip 118 of the ultrasound catheter 100. Further, the steering control unit 112 can align the surface of a microelectromechanical (MEMS)-based piezoelectric micromachined ultrasonic transducer (pMUT) array (not shown) towards different fields of view, which include anterior and posterior positions within the heart. Additionally, the steering control unit 112 can include a steering handle 114 and a housing 116 that encapsulates an actuator (not shown) and a steering hub (not shown). It can be noted that internal friction occurs between the actuator and the steering hub and between the actuator and the housing 116, which causes the ultrasound catheter 100 to maintain its adjusted configuration without operator attention. Further, the steering handle 114 can be rotated to facilitate the positioning of the distal tip 118 of the ultrasound catheter 100.

[0027] In one embodiment, the steering handle 114 can be rotated to position the distal tip 118 within a chamber of a patient's heart. In one embodiment, the steering control unit 112 can include a set of steering wires controlled by the steering control unit 112 to articulate the distal section of the ultrasound catheter 100 in multiple directions when the ultrasound catheter 100 is placed within the heart. Additionally, the ultrasound catheter 100 can be disposed within a chamber of a patient's heart and coupled to an imaging system (not shown) using a coaxial cable (not shown) for displaying two-dimensional (2D) or three-dimensional (3D) images of the heart chamber using ultrasonic waves and acoustic pulses.

[0028] Furthermore, the ultrasound catheter 100 can be used to perform electrophysiology (EP). The ultrasound catheter 100 can be combined with another imaging modality such as x-ray, fluoroscopy, magnetic resonance, computed tomography, or an optical system for diagnosis and / or treatment. Both imaging modalities can scan the patient to generate images to assist the doctor. By locating markers within the images of the other modality that have a known spatial relationship to the ultrasound scan, data from different modalities can be aligned. In other embodiments, the ultrasound catheter 100 can be a flexible cylindrical portion without markers and / or without other imaging modalities. In one embodiment, the ultrasound catheter 100 can utilize a microelectromechanical (MEMS) system defined as piezoelectric micromachined ultrasonic transducers (pMUTs) or other types of MEMS transducers interconnected using matched flexible circuits. In one embodiment, the ultrasound catheter 100 can correspond to an intracardiac echocardiogram (ICE) MEMS ultrasound catheter that utilizes high-density flexible circuits for all transmissions and electrical interconnections. It can be noted that highly repeatable and stable transmissions and return signals can be achieved using high-density flexible circuits. Additionally, the high-density flexible circuit transmission lines can transmit electrical energy from one end of the ultrasound catheter 100 to the other end.

[0029] In addition, the ultrasound catheter 100 may include a catheter shaft 120. The catheter shaft 120 may be coupled to the handle assembly 110 at one end and to the distal tip 118 of the ultrasound catheter 100 at the other end. Additionally, the catheter shaft 120 may enclose an electronic flexible circuit (not shown) and a plurality of steering cables (not shown). In one embodiment, the electronic flexible circuit may be referred to as a flexible cable. It can be noted that the electronic flexible circuit may be bent or tilted towards the front position and / or the rear position within the heart chamber. In one embodiment, the electronic flexible circuit may include strands, wires, and / or threads, and is preferably made of a low-profile, durable, inelastic, and non-conductive material. In one embodiment, the steering cable or steering wire may be made of stainless steel. In another embodiment, the steering cable may be made of a synthetic material, such as nylon or a similar synthetic fiber, or a plastic material, such as polyurethane, polyethylene, multi-strand nylon, or gel-spun polyethylene fiber. For example, the steering cable may be a multi-strand brand nylon thread, sold as fishing line (10-pound test).

[0030] The ultrasound catheter 100 may be provided for transmitting ultrasound signals within a patient's heart chamber. In one embodiment, the ultrasound catheter 100 may be a flexible elongate member, where one end of the body 102 has the catheter shaft 120 and the other end has the handle assembly 110. In one embodiment, the distal tip 118 of the ultrasound catheter 100 may be coated with an insulating material. Additionally, the insulating material may be disposed at the distal end 108 above the imaging window (not shown) to prevent electrical breakdown and leakage of electrical signals from the ultrasound catheter 100. The insulating material may be a copolymer material, such as but not limited to polyether block amide (e.g., PEBA, sold under the trade name PEBAX'), and thermoplastic elastomer (TPE). In one embodiment, the insulating material provides a low-loss acoustic window. It can be noted that when the ultrasound catheter 100 is inserted into a patient's heart, the insulating material provides a low-loss path for acoustic echoes.

[0031] Figure 2 A schematic diagram of an ultrasound catheter 100 according to an embodiment of the present disclosure is shown. Figure 2 In conjunction with Figure 1 is described.

[0032] The ultrasonic catheter 100 may include a microelectromechanical systems (MEMS)-based piezoelectric micromachined ultrasonic transducer (pMUT) array 202 and a substrate 204. The MEMS-based pMUT array 202 may be disposed above the substrate 204 toward the distal end 108 of the ultrasonic catheter 100. Additionally, the MEMS-based pMUT array 202 may be disposed within the distal tip 118 of the ultrasonic catheter 100.

[0033] The catheter shaft 120 may be coupled between the handle assembly 110 and the MEMS-based pMUT array 202 via a distal pMUT interposer (not shown). An electronic flexible circuit within the catheter shaft 120 may receive at least one signal from the MEMS-based pMUT array 202 and may transmit the received signal back to an imaging device (not shown). Additionally, the MEMS-based pMUT array 202 may send a pressure wave toward a target and receive a returned pressure wave echo from the target. In one embodiment, the target may be within a heart chamber of a patient. The MEMS-based pMUT array 202 may transmit the received pressure wave echo back to the imaging device via the electronic flexible circuit for further analysis of the pressure wave echo for image generation. The MEMS-based pMUT array 202 includes a plurality of MEMS-based pMUT array elements (not shown) disposed on the substrate 204.

[0034] In one embodiment, the ultrasonic catheter 100 may employ an MEMS-based pMUT array 202 having a bulk piezoelectric transducer (PZT), a piezoelectric micromachined (pMUT) transducer, or a capacitive micromachined transducer (CMUT) array to be introduced via a subclavian access for lead implantation of a pacemaker, defibrillator, and structural heart implants, as well as other cardiac procedures.

[0035] Figure 3 An interconnect diagram is shown in accordance with an embodiment of the present disclosure, which shows a side view stack of an electronic flexible connection through a multi-layer AIC with a microelectromechanical systems (MEMS)-based piezoelectric micromachined ultrasonic transducer (pMUT) array. Figure 3 In combination with Figure 1 and Figure 2 is described.

[0036] Refer to Figure 3, the first layer 308 of the AIC and the second layer 310 of the AIC are used to achieve a compression connection between the catheter handle connector 302, the plurality of electronic flexible circuits 304, the MEMS-based pMUT array 202, and the distal pMUT interposer 306. The AIC can be made of a material selected from a group of materials including anisotropic conductor film (ACF), anisotropic conductive paste (ACP), or a similar anisotropic conductive adhesive (ACM), or made by a conductive adhesive (ECA) or other such conductive adhesives. The first layer 308 and the second layer 310 of the AIC can sandwich the distal pMUT interposer 306 therebetween and create a compression connection between the plurality of electronic flexible circuits 304 and the distal pMUT interposer 306. In addition, the first layer 308 of the AIC can be coupled to the catheter handle connector 302 via the plurality of electronic flexible circuits 304, and the second layer 310 of the AIC can be coupled between the MEMS-based pMUT array 202 and the distal pMUT interposer 306. In addition, the catheter handle connector 302 can transmit ultrasonic signals through the plurality of electronic flexible circuits 304 to the distal end 108 of the ultrasonic catheter 100. In addition, the catheter handle connector 302 can include a board edge connector (not shown) and connector pins (not shown) to transmit ultrasonic signals to the distal end 108 of the ultrasonic catheter 100.

[0037] In one embodiment, the first layer 308 and the second layer 310 of the AIC can provide a lead-free and environmentally friendly adhesive interconnection system. As Figure 4A shown, the first layer 308 and the second layer 310 of the AIC can be used to create a conductive adhesive for flexible circuits and rigid circuits. In addition, the first layer 308 and the second layer 310 of the AIC can provide an extremely fine pitch capability for the pressure echoes received from the MEMS-based pMUT array 202.

[0038] In addition, as Figure 4AAs shown, the distal pMUT interposer 306 is sandwiched between the first layer 308 of the AIC and the second layer 310 of the AIC, and has an InvisiVia connection 402. In one embodiment, the distal pMUT interposer 306 may be referred to as a distal pMUT flexible cable interposer. Additionally, the distal pMUT interposer 306 may correspond to a UHD flexible circuit interposer connected to the MEMS-based pMUT array 202 via ultra-high density (UHD) interconnect pads (not shown). The UHD interconnect pads may be connected to the MEMS-based pMUT array 202 by using near-seamless interface vias. In one embodiment, the first layer 308 of the AIC may provide connections between multiple electronic flexible circuits 304 and the UHD interconnect pads. The second layer 310 of the AIC may provide connections between the UHD interconnect pads and the MEMS-based pMUT array 202.

[0039] It should be noted that the MEMS-based pMUT array 202 may send pressure waves and receive returned pressure wave echoes via the InvisiVia connection 402 of the distal pMUT interposer 306. Additionally, using the InvisiVia connection 402 can create a flat and planar interconnect with the UHD interconnect pads. In one example, the InvisiVia connection 402 creates a flat and planar interconnect diameter of no more than 5um. Moreover, the InvisiVia connection 402 is crucial for the electrical performance of the ultrasonic catheter 100. In one embodiment, the InvisiVia connection 402 can eliminate the possibility of undesired leakage to the bulk silicon substrate of the MEMS-based pMUT array 202. In one embodiment, the InvisiVia connection 402 can range from 16 to 128.

[0040] Referring Figure 4B to, according to an embodiment of the present disclosure, an InvisiVia connection 402 with a flat and planar interconnect from a flexible circuit to a highly flat attachment ground / pad surface is disclosed.

[0041] The InvisiVia connection 402 may be configured to bring an electronic flexible circuit connection from one side of the distal pMUT interposer 306 to the other side. It can be noted that the purpose of the InvisiVia connection 402 is that the second layer 310 of the AIC should not be connected to the silicon on the side of the MEMS-based pMUT array 202. Additionally, the InvisiVia connection 402 can create a flat and planar interconnect from the electronic flexible circuit to the second layer 310 of the AIC, as Figure 5 and Figure 6 shown. In one embodiment, the flexible pads are electrically connected to the MEMS-based pMUT array 202 using a thermocompression adhesive system.

[0042] In addition, the InvisiVia connection 402 can be a tapered portion having a first end 404 and a second end. The InvisiVia connection 402 can be disposed within the distal pMUT interposer 306, as Figure 4C shown. The first end 404 and the second end 406 can have diameter ranges of 10um to 25um and 0um to 8um, respectively. In one embodiment, the InvisiVia connection 402 is provided with an InvisiVia plating 408 between the first end 404 and the second end 406. In one embodiment. The first end 404 and the second end 406 can correspond to the top and bottom ends of the InvisiVia connection 402. The first end 404 of the InvisiVia connection 402 can be connected to the second layer 310 of the AIC via a trace 412. In addition, the second end 406 of the InvisiVia connection 402 can be connected to the MEMS-based pMUT array 202 through the second layer 310 of the AIC. It can be noted that the InvisiVia connection 402 can facilitate the MEMS-based pMUT array 202 to have an extremely flat and planar surface, having the largest surface area due to no copper penetration or only minimal copper penetration.

[0043] In one embodiment, the distal pMUT interposer 306 is aligned and bonded, and the pressure echo can be electrically transmitted through the InvisiVia connection 402 of the distal pMUT interposer 306. This provides a z-axis routing of the ultrasonic signal from the MEMS-based pMUT array 202. The first layer 308 of the AIC and the second layer 310 of the AIC can include an adhesive material to physically hold the distal pMUT interposer 306 to the MEMS-based pMUT array 202. The InvisiVia connection 402 can be created from a z-axis interconnect of two or more signal layers or ground layers using an ultraviolet (UV) laser 410 having a hole diameter not exceeding 10um, and then copper-plated to a closed and highly planar attachment ground / pad surface. In one embodiment, the UV laser 410 can have a beam width of less than 25um.

[0044] Figure 5 A schematic diagram of the first layer 308 of the AIC according to an embodiment of the present disclosure is shown, which connects a plurality of electronic flexible circuits 304 to the distal pMUT interposer 306.

[0045] In addition, the distal pMUT interposer 306 can be coupled to the plurality of electronic flexible circuits 304 via the first layer 308 of the AIC. The first layer 308 of the AIC can include a plurality of conductive particles 502. It can be noted that the plurality of conductive particles 502 can create a compressive connection between the plurality of electronic flexible circuits 304 and the distal pMUT interposer 306. Thus, stable transmission of ultrasonic signals is achieved through the first layer 308 of the AIC between the plurality of electronic flexible circuits 304 and the distal pMUT interposer 306. The first layer 308 of the AIC can provide an extremely fine pitch capability for pressure echoes received from the MEMS-based pMUT array 202.

[0046] Figure 6 An interconnection diagram according to an embodiment of the present disclosure is shown, which shows a top-down stack of the InvisiVia connection 402 with the MEMS-based pMUT array 202 through the second layer 310 of the AIC.

[0047] In addition, as Figure 6 shown, the distal pMUT interposer 306 can be coupled to the MEMS-based pMUT array 202 via the second layer 310 of the AIC. It can be noted that the distal pMUT interposer 306 can create a compressive connection between the InvisiVia connection 402 of the distal pMUT interposer 306 and the MEMS-based pMUT array 202 via the plurality of conductive particles 502 of the second layer 310 of the AIC. It can also be noted that the second layer 310 of the AIC can also provide an extremely fine pitch capability for pressure echoes received from the MEMS-based pMUT array 202. In one embodiment, the InvisiVia connection 402 can create a flat and planar interconnect diameter of no greater than 5 um.

[0048] Figure 7 A schematic diagram according to an embodiment of the present disclosure showing the AIC layer connecting the distal pMUT interposer 306 to the MEMS-based pMUT array 202 is shown.

[0049] Multiple electronic flexible circuits 304 are connected to the distal pMUT interposer 306 via the first layer 308 of the AIC. The distal pMUT interposer 306 is connected to the MEMS-based pMUT array 202 via the second layer 310 of the AIC. It can be noted that the distal pMUT interposer 306 may correspond to a UHD flexible circuit interposer connected to the MEMS-based pMUT array 202 through UHD interconnect pads. The UHD interconnect pads can be connected to the MEMS-based pMUT array 202 by using near-seamless via holes. In addition, a flat and planar interconnection with the MEMS-based pMUT array 202 can be created using InvisiVia connection 402. Further, a compression connection can be achieved between the multiple electronic flexible circuits 304, the first layer 308 of the AIC, the distal pMUT interposer 306, the second layer 310 of the AIC, and the MEMS-based pMUT array 202. In one embodiment, using InvisiVia connection 402 can eliminate the possibility of unwanted leakage from the bulk silicon substrate of the MEMS-based pMUT array 202.

[0050] Referring Figures 8 to 9 , a cross-sectional image of the heart 800 is disclosed, where the ultrasound catheter 100 is positioned within the right atrium 802 of the heart 800. The distal tip 118 of the ultrasound catheter 100 can be inserted into the right atrium 802 via the inferior vena cava (not shown). To perform adequate imaging of the interatrial septum (IAS) 804 and its adjacent structures, two standardized views can be used. The movement of the distal tip 118 of the ultrasound catheter 100 within the right atrium 802 can be controlled by the steering control unit 112. Further, by moving the distal tip 118 clockwise or counterclockwise by the steering control unit 112, the imaging window can be allowed to move from a posterior view to an anterior view, and vice versa.

[0051] In addition, as Figures 8 to 9 shown, to correctly position the MEMS-based pMUT array 202 at the location of imaging the right atrium 802 and the mitral valve 806, a flexible sheath can be introduced into the patient's vascular structure via the femoral vein (not shown). Using fluoroscopic imaging to monitor the position of the ultrasound catheter, the clinician can advance the distal end 108 of the ultrasound catheter 100 into the right atrium 802. To guide the ultrasound catheter 100 through a turn in the patient's vascular structure, the clinician can rotate the distal tip 118 clockwise or counterclockwise to allow the imaging window to move from an anterior position to a posterior position, and vice versa. Once the distal tip 118 of the ultrasound catheter 100 enters the right atrium 802, the clinician can rotate the distal tip 118 to introduce an acute bend in the flexible sheath, thereby guiding the MEMS-based pMUT array 202 through the tricuspid valve 808 and into the right ventricle 810, as Figure 6As shown. At this position, the field of view of the MEMS-based pMUT array 202 can include the right ventricle 810, the IAS 804, the mitral valve 806, the left ventricle 812, the left atrium 814, and a portion of the left ventricular wall. In one embodiment, when the MEMS-based pMUT array 202 is guided clockwise, the right ventricle 810 and the right ventricular wall can be imaged. It can be noted that a clinician may twist the ultrasound catheter 100 when the ultrasound catheter 100 is positioned within the heart 800 as Figures 8 to 9 shown, and the MEMS-based pMUT array 202 will swing around the axis, which may damage the tricuspid valve 808 or cause the MEMS-based pMUT array 202 to impact the IAS 804. Figure 8 A vertical short-axis view is shown to visualize the internal portion of the IAS 804. The internal portion of the IAS 804 includes the aorta 902 and the mitral valve 904 facing the left ventricle 812.

[0052] In one exemplary embodiment, the standard view is obtained by placing the ultrasound catheter 100 in the middle of the right atrium and placing the MEMS-based pMUT array 202 in the neutral position facing the tricuspid valve 808. The standard view provides imaging of the right atrium 802, the tricuspid valve 808, the right ventricle 810, and is generally an oblique or short-axis view of the aortic valve.

[0053] In addition, when the ultrasound catheter 100 can be rotated clockwise, the aortic valve and the outflow tract of the right ventricle 810 on the long axis are observed. In this view, the tricuspid valve 808 closer to the MEMS-based pMUT array 202 or the distal tip 118 is the non-coronary cusp, which is closely related to the membranous septum and the para-Hisian region, while the opposite is the right coronary cusp, which is the most anterior part of the aortic valve cusp and is directly behind the infundibulum of the outflow tract of the right ventricle 810 and the pulmonary valve. The left ventricle 812 is visualized in front of the most septal part of the right atrium 802, and the opening of the coronary sinus becomes apparent. In this view, the long axis of the outflow tract of the left ventricle 812 is identified, and the left ventricle 812 is exactly located directly below the non-coronary cusp.

[0054] In addition, further clockwise rotation of the ultrasound catheter 100 allows visualization of the mitral valve 904 and the IAS 804, where the left atrial appendage is in front and the coronary sinus is behind. Examine whether there is a thrombus at the opening of the left atrial appendage of the left atrium 814, and color Doppler can be used to evaluate mitral regurgitation.

[0055] In one embodiment, most catheters for intravascular applications, particularly those with ultrasonic transducers, have a diameter of at least about 6 French. The electronics and wires required for an ultrasonic transducer array make it impractical and expensive to reduce the size of such catheters below about 6 French. However, reducing the diameter of the catheter is beneficial, and technological advancements can enable further reduction in the size of the electronics and control structures. The coaxial cable, steering and pivot cables, and the bundled arrangement of the steering and pivot mechanisms will be described in more detail below, which enables effective reduction of the diameter to below about 6 French, about 5 French, about 4 French, about 3 French, or even about 2 French.

[0056] Although certain specific structures embodying various embodiments of the present invention are shown and described herein, those skilled in the art will appreciate that various modifications and rearrangements of the components can be made without departing from the spirit and scope of the basic inventive concept, and that such modifications and rearrangements are not limited to the specific forms shown herein except as indicated by the scope of the appended claims.

Claims

1. An ultrasonic catheter, the ultrasonic catheter comprising: A body having a longitudinal axis, a proximal end, and a distal end; A microelectromechanical (MEMS)-based piezoelectric micromachined ultrasonic transducer (pMUT) array disposed within the distal end of the body; A plurality of electronic flexible circuits connected at one end to a handle connector and at the other end to a first layer of an adhesive interconnect (AIC), wherein the handle connector transmits ultrasonic signals to the distal end via the plurality of electronic flexible circuits; and A distal pMUT interposer disposed between the first layer of the AIC and a second layer of the AIC, the distal pMUT interposer having InvisiVia connections, wherein the InvisiVia connections are configured to bring the electronic flexible circuits from one side of the distal pMUT interposer to the other side, wherein the MEMS-based pMUT array transmits pressure waves and receives returned pressure wave echoes via the InvisiVia connections of the distal pMUT interposer.

2. The ultrasonic catheter according to claim 1, wherein, Use the AIC to achieve compression connections between the plurality of electronic flexible circuits, the first layer of the AIC, the distal pMUT interposer, the second layer of the AIC, and the MEMS-based pMUT array.

3. The ultrasonic catheter according to claim 1, wherein, The distal pMUT interposer corresponds to an ultra-high density (UHD) flexible circuit interposer connected to the MEMS-based pMUT array via ultra-high density (UHD) interconnect pads.

4. The ultrasonic catheter according to claim 3, wherein, The UHD interconnect pads are connected to the MEMS-based pMUT array by using near-seamless via holes.

5. The ultrasonic catheter according to claim 1, wherein, The InvisiVia connections provide a connection between the first layer of the AIC and the second layer of the AIC.

6. The ultrasonic catheter according to claim 3, wherein, The first layer of the AIC provides a connection between the plurality of electronic flexible circuits and the UHD interconnect pads.

7. The ultrasonic catheter according to claim 3, wherein, The second layer of the AIC provides a connection between the UHD interconnect pads and the MEMS-based pMUT array.

8. The ultrasonic catheter according to claim 4, wherein, Use the InvisiVia connections to create a flat and planar interconnect with the UHD interconnect pads.

9. The ultrasonic catheter according to claim 1, wherein, The InvisiVia connections create a flat and planar interconnect diameter no greater than 5um.

10. The ultrasonic catheter according to claim 1, wherein, Use the InvisiVia connections to eliminate the possibility of unwanted leakage to the bulk silicon substrate of the MEMS-based pMUT array.

11. The ultrasonic catheter according to claim 1, wherein, The InvisiVia connections provide an extremely flat and planar surface with a maximum surface area due to minimal copper penetration.

12. The ultrasonic catheter according to claim 1, wherein, The number of the InvisiVia connections is between 30 and 128.

13. The ultrasonic catheter according to claim 1, wherein, The InvisiVia connections are created from z-axis interconnections of two or more signal layers or ground layers using an ultraviolet (UV) laser with a hole diameter not exceeding 10um, which is subsequently copper-plated to a closed and highly planar attachment pad / surface.

14. The ultrasonic catheter according to claim 1, wherein, The InvisiVia connections have a first end and a second end with diameter ranges of 5um to 25um and 0um to 10um, respectively.

15. The ultrasonic catheter according to claim 1, wherein, The InvisiVia connections are provided with an InvisiVia plating between the first end and the second end.

16. The ultrasonic catheter according to claim 1, wherein, The MEMS-based pMUT array includes a plurality of MEMS-based pMUT array elements.

17. The ultrasonic catheter according to claim 16, wherein, Each of the plurality of MEMS-based pMUT array elements is a linear phased array.

18. The ultrasonic catheter according to claim 16, wherein, The plurality of MEMS-based pMUT array elements create separate focused beams.

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