Rolled flexible substrate with integrated window for intraluminal ultrasound

An intraluminal ultrasound imaging device includes a flexible elongate member configured to be inserted into a body lumen of a patient, the flexible elongate member comprising a proximal portion and a distal portion. The device includes an ultrasound scanner assembly disposed at the distal portion of the flexible elongate member. The ultrasound scanner assembly includes a flexible substrate comprising a longitudinal width extending from an inner edge to an outer edge; a control region embedded in the flexible substrate; a transducer region embedded in the flexible substrate; and a window region disposed between the outer edge of the flexible substrate and the transducer region, and wherein the window region, the transducer region, and the control region are radially arranged relative to one another. Associated devices, systems, and methods are also described.

TECHNICAL FIELD

The present disclosure relates generally to intravascular ultrasound (IVUS) imaging and, in particular, to the distal structure of an intravascular imaging device. For example, the distal structure can include a support structure and and/or a flexible substrate that are rolled to facilitate efficient assembly and operation of the intravascular imaging device.

BACKGROUND

Intravascular ultrasound (IVUS) imaging is widely used in interventional cardiology as a diagnostic tool for assessing a diseased vessel, such as an artery, within the human body to determine the need for treatment, to guide the intervention, and/or to assess its effectiveness. An IVUS device including one or more ultrasound transducers is passed into the vessel and guided to the area to be imaged. The transducers emit ultrasonic energy in order to create an image of the vessel of interest. Ultrasonic waves are partially reflected by discontinuities arising from tissue structures (such as the various layers of the vessel wall), red blood cells, and other features of interest. Echoes from the reflected waves are received by the transducer and passed along to an IVUS imaging system. The imaging system processes the received ultrasound echoes to produce a cross-sectional image of the vessel where the device is placed.

Solid-state (also known as synthetic-aperture) IVUS catheters are one of the two types of IVUS devices commonly used today, the other type being the rotational IVUS catheter. Solid-state IVUS catheters carry a scanner assembly that includes an array of ultrasound transducers distributed around its circumference along with one or more integrated circuit controller chips mounted adjacent to the transducer array. The controllers select individual transducer elements (or groups of elements) for transmitting an ultrasound pulse and for receiving the ultrasound echo signal. By stepping through a sequence of transmit-receive pairs, the solid-state IVUS system can synthesize the effect of a mechanically scanned ultrasound transducer but without moving parts (hence the solid-state designation). Since there is no rotating mechanical element, the transducer array can be placed in direct contact with the blood and vessel tissue with minimal risk of vessel trauma. Furthermore, because there is no rotating element, the electrical interface is simplified. The solid-state scanner can be wired directly to the imaging system with a simple electrical cable and a standard detachable electrical connector, rather than the complex rotating electrical interface required for a rotational IVUS device.

Manufacturing an intravascular imaging device that can efficiently traverse anatomic structures within the human body is challenging. In that regard, imaging components may create an area of high rigidity and large diameter at the distal portion of the intravascular imaging device, which increase the likelihood of kinking as the intravascular device is steered through anatomical lumens (including, for example but without limitation, small diameter vasculature such as coronary vessels).

Thus, there remains a need for intravascular ultrasound imaging system that overcomes the limitations of a relatively large diameter and rigid imaging assembly to facilitate access to small diameter vasculature and/or other anatomical spaces while maintaining efficient assembly and operation. In particular, there remains a need for new phased array architectures that allow for ease of manufacture while minimizing the overall profile to the imaging portion of the intravascular device (e.g., by reducing the diameter and/or the stiff length).

SUMMARY

Embodiments of the present disclosure provide an improved intravascular ultrasound imaging system for generating images of a blood vessel. A distal portion of an intravascular imaging device can comprise an imaging assembly including a flexible substrate and a support member around which the flexible substrate is wrapped. The flexible substrate can include proximal, distal, and central portions. The imaging assembly may comprise transducer regions and control regions positioned laterally on the central portion of the flexible substrate. When the flexible substrate is rolled or wrapped about the support member, the transducer region is wrapped around or stacked circumferentially atop the control region. Accordingly, the stiff length and overall diameter of the imaging assembly, including the flexible substrate, the transducer region, and the control region, are minimized, thereby facilitating navigation of the intravascular imaging device into small diameter anatomical lumens. The flexible substrate can include an integrally formed support structure that is wrapped/rolled along with the control and transducer regions. The flexible substrate can include an integrally formed imaging window that that is wrapped/rolled along with the control and transducer regions. The sidewalls of the transducer elements can be angled such that the transducer elements are arranged adjacent to one another without colliding when the transducer region is wrapped/rolled.

In an exemplary aspect, an intraluminal ultrasound imaging device is provided. The device includes a flexible elongate member configured to be inserted into a body lumen of a patient, the flexible elongate member comprising a proximal portion and a distal portion; an ultrasound scanner assembly disposed at the distal portion of the flexible elongate member, the ultrasound scanner assembly comprising: a flexible substrate comprising a longitudinal width extending from an inner edge to an outer edge; a control region embedded in the flexible substrate; a transducer region embedded in the flexible substrate; and a window region disposed between the outer edge of the flexible substrate and the transducer region, and wherein the window region, the transducer region, and the control region are radially arranged relative to one another.

In some aspects, the window region comprises an integrated part of the flexible substrate. In some aspects, the window region is disposed adjacent the transducer region and defines the outer edge of the flexible substrate. In some aspects, the window region includes a variable thickness from an inner window edge to an outer window edge. In some aspects, the thickness of the window region is greatest in an area overlying the transducer region when the flexible substrate is in a rolled configuration. In some aspects, flexible substrate includes a central axis extending through a longitudinal width of the flexible substrate, and the window region, the transducer region, and the control region are stacked adjacent one another along the central axis. In some aspects, the window region, the transducer region, and the control region are coaxially aligned along the central axis. In some aspects, the flexible substrate is rolled into a layered, annular scanner assembly with the control region forming an inner layer, the transducer region forming a middle layer, and the window region forming an outer layer of the scanner assembly. In some aspects, the flexible substrate further comprises a support region disposed between the inner edge of the flexible substrate and the control region, wherein the window region, the transducer region, the control region, and the support region are laterally disposed adjacent one another. In some aspects, the flexible substrate is rolled into a layered, annular scanner assembly with the support region forming an innermost first layer defining a cylindrical lumen, the control region forming a second middle layer, the transducer region forming a third middle layer, and the window region forming an outermost layer of the scanner assembly. In some aspects, the window region comprises a flange extending from the outer edge of the flexible substrate. In some aspects, the flexible substrate further comprises a transition region disposed between the window region and the transducer region. In some aspects, the transition region is sized and configured to enable the rolling of the transducer region and the window region of flexible substrate into separate, nested cylinders.

In an exemplary aspect, a method of assembling an intraluminal ultrasound imaging device. The method includes obtaining a flexible substrate comprising a central axis extending along the width of the flexible substrate from an inner edge to an outer edge; positioning an ultrasound transducer region, a control region, and a window region laterally along the central axis of the flexible substrate, wherein the window region is disposed between the outer edge and the ultrasound transducer region; and rolling the flexible substrate into a layered cylindrical shape, wherein the control region forms an inner layer, the ultrasound transducer region forms a middle layer, and the window region forms an outer layer.

In some aspects, the method further includes obtaining a support member comprising a lumen running therethrough. In some aspects, the method further includes positioning the support member adjacent the control region before rolling the flexible substrate. In some aspects, rolling the flexible substrate into a layered cylindrical shape comprises wrapping the control region around the support member, wherein the control region forms an inner layer surrounding the support member, the ultrasound transducer region forms a middle layer surrounding the control region, and the window region forms an outer layer surrounding the ultrasound transducer region. In some aspects, the window region is radially spaced from the ultrasound transducer region, the ultrasound transducer region is radially spaced from the control region, and the control region is radially spaced from the support member. In some aspects, the window region is radially spaced from the ultrasound transducer region and the ultrasound transducer region is radially spaced from the control region. In some aspects, the method further includes inserting acoustic matching medium between the window region and the ultrasound transducer region.

In some aspects, the flexible substrate further comprises a transition region disposed between the transducer region and the window region. In some aspects, the window region has a generally rectangular shape. In some aspects, the control region is disposed adjacent the inner edge of the flexible substrate. In some aspects, the transducer region comprises a plurality of transducers, and the control region comprises a plurality of controllers. In some aspects, the plurality of transducers comprises a plurality of capacitive micromachined ultrasound transducers.

DETAILED DESCRIPTION

FIG.1is a diagrammatic schematic view of an intravascular ultrasound (IVUS) imaging system100, according to aspects of the present disclosure. The IVUS imaging system100may include a solid-state IVUS device102such as a catheter, guide wire, or guide catheter, a patient interface module (PIM)104, an IVUS processing system or console106, and a monitor108.

At a high level, the IVUS device102emits ultrasonic energy from a transducer array124included in scanner assembly110mounted near a distal end of the catheter device. The ultrasonic energy is reflected by tissue structures in the medium, such as a vessel120, surrounding the scanner assembly110, and the ultrasound echo signals are received by the transducer array124. The PIM104transfers the received echo signals to the console or computer106where the ultrasound image (including the flow information) is reconstructed and displayed on the monitor108. The console or computer106can include a processor and a memory. The computer or computing device106can be operable to facilitate the features of the IVUS imaging system100described herein. For example, the processor can execute computer readable instructions stored on the non-transitory tangible computer readable medium.

The PIM104facilitates communication of signals between the IVUS console106and the scanner assembly110included in the IVUS device102. This communication includes the steps of: (1) providing commands to integrated circuit controller chip(s)206A,206B, illustrated inFIG.2, included in the scanner assembly110to select the particular transducer array element(s) to be used for transmit and receive, (2) providing the transmit trigger signals to the integrated circuit controller chip(s)206A,206B included in the scanner assembly110to activate the transmitter circuitry to generate an electrical pulse to excite the selected transducer array element(s), and/or (3) accepting amplified echo signals received from the selected transducer array element(s) via amplifiers included on the integrated circuit controller chip(s)206A, B of the scanner assembly110. In some embodiments, the PIM104performs preliminary processing of the echo data prior to relaying the data to the console106. In examples of such embodiments, the PIM104performs amplification, filtering, and/or aggregating of the data. In an embodiment, the PIM104also supplies high- and low-voltage DC power to support operation of the device102including circuitry within the scanner assembly110.

The IVUS console106receives the echo data from the scanner assembly110by way of the PIM104and processes the data to reconstruct an image of the tissue structures in the medium surrounding the scanner assembly110. The console106outputs image data such that an image of the vessel120, such as a cross-sectional image of the vessel120, is displayed on the monitor108. Generally, the system100and/or the device102can be used in any suitable lumen of a patient body. In that regard, the system100can be an intraluminal ultrasound imaging system100, and the device102can be an intraluminal ultrasound imaging system100. The system100and/or the device102can be referenced as an interventional device, a therapeutic device, a diagnostic device, etc. The device102can be sized and shaped, structurally arranged, and/or otherwise configured to be positioned within the vessel or lumen120. Lumen or vessel120may represent fluid filled or surrounded structures, both natural and man-made. The lumen or vessel120may be within a body of a patient. The vessel120may be a blood vessel, such as an artery or a vein of a patient's vascular system, including cardiac vasculature, peripheral vasculature, neural vasculature, renal vasculature, and/or or any other suitable lumen inside the body. For example, the device102may be used to examine any number of anatomical locations and tissue types, including without limitation, organs including the liver, heart, kidneys, gall bladder, pancreas, lungs; ducts; intestines; nervous system structures including the brain, dural sac, spinal cord and peripheral nerves; the urinary tract; as well as valves within the blood, chambers or other parts of the heart, and/or other systems of the body. In addition to natural structures, the device102may be may be used to examine man-made structures such as, but without limitation, heart valves, stents, shunts, filters and other devices.

In some embodiments, the IVUS device includes some features similar to traditional solid-state IVUS catheters, such as the EagleEye® catheter available from Volcano Corporation and those disclosed in U.S. Pat. No. 7,846,101 hereby incorporated by reference in its entirety. For example, the IVUS device102includes the scanner assembly110near a distal end of the device102and a transmission line bundle112extending along the longitudinal body of the device102. The transmission line bundle or cable112can include one conductor or a plurality of conductors, including two, three, four, five, six, seven, or more conductors218(as shown inFIG.2). It is understood that any suitable gauge wire can be used for the conductors218. In an embodiment, the cable112can include a four-conductor transmission line arrangement with, e.g., 41 AWG gauge wires. In an embodiment, the cable112can include a seven-conductor transmission line arrangement utilizing, e.g., 44 AWG gauge wires. In some embodiments, 43 AWG gauge wires can be used.

The transmission line bundle112terminates in a PIM connector114at a proximal end of the device102. The PIM connector114electrically couples the transmission line bundle112to the PIM104and physically couples the IVUS device102to the PIM104. In an embodiment, the IVUS device102further includes a guide wire exit port116. Accordingly, in some instances the IVUS device is a rapid-exchange catheter. The guide wire exit port116allows a guide wire118to be inserted towards the distal end in order to direct the device102through the vessel120.

FIG.2is a perspective view of the top of an ultrasound scanner assembly110in an unrolled or flat configuration according to an embodiment of the present disclosure.FIG.3is a perspective view of the bottom of the scanner assembly110shown inFIG.2in a flat configuration and a support member230, according to aspects of the present disclosure. In particular,FIG.3illustrates the flexible substrate214and the support member230prior to the flexible substrate214being rolled around the support member230.

The assembly110includes a transducer array124formed in a transducer region204and transducer control logic dies206(including dies206A and206B) formed in a control region208, with a transition region210disposed therebetween. The transducer array202is a non-limiting example of a medical sensor element and/or a medical sensor element array. The transducer control logic dies206is a non-limiting example of a controller or a control circuit.

The transducer control logic dies206and the transducers212are mounted on a flexible substrate214(or flex circuit214) that is shown in an unrolled or flat configuration inFIG.2. The flexible substrate214includes three zones or portions extending along an overall longitudinal length L1: a proximal portion209, a distal portion211, and a central portion213. In the embodiment shown inFIG.2, the transducer region204, the transition region210, and the control region208are laterally disposed (or stacked) adjacent one another within the central portion213. Thus, the transducers212are positioned laterally (or stacked) relative to the transducer control logic dies206within the central portion213of the flexible substrate214. The term “adjacent” as used herein does not necessitate that the transducer region204and the control region are in contact with each other. The term “adjacent” is used to mean simply that the two regions are generally positioned in a coaxial fashion. In other embodiments, the transducers212and/or the transducer control logic dies206may be disposed at least partially within the proximal portion209and/or the distal portion211. As the names imply, the transducer region204contains the transducers212, and the control region208contains the transducer control logic dies206. This lateral arrangement of the transducers212and the transducer control logic dies206, where the transducer region204and the control region208are positioned side-by-side along a longitudinal width W1 of the flexible substrate, minimizes the overall longitudinal length L1 and an overall stiff length L2 of the scanner assembly110. In this embodiment, the stiff length L2 of the scanner assembly110comprises the length of the longer of the two stiff components included on the flexible substrate214, which in this case is the length of the transducer control logic dies206. In contrast, for example, positioning the transducers212distal to the transducer control logic dies206on the flexible substrate214would necessarily require an increase in both the overall length L1 of the flexible substrate214and the stiff length L2 of the scanner assembly110(namely, the combined lengths of the transducer control logic dies206, the transition region110, and the transducers212). The length L1 may measure between 0.5 mm and 5 mm, including values between 0.5 mm and 1.5 mm, such as 0.5 mm, 1 mm, 1.5 mm, 2 mm, and/or other suitable values both larger and smaller. The length L2 may measure between 0.5 mm and 5 mm, or between 1 mm and 5 mm, including values such as a 0.5 mm, 1 mm,1.5and/or other suitable values both larger and smaller.

In the pictured embodiment, both the transducer region204and the control region208are aligned along a central axis CA extending through the central portion213from an inner edge222to an outer edge223of the flexible substrate214. Although the transducers212and the transducer control logic dies206are shown as coxially aligned along the central axis CA in the pictured embodiment inFIG.2, the transducers212and the transducer control logic dies206may be disposed upon flexible substrate214in dissimilar, unaligned patterns in other embodiments. The transducer region204is disposed adjacent the outer edge223of the flexible substrate214. The control region208is disposed adjacent the inner edge222of the flexible substrate214. In some embodiments, the transducer region204and/or the control region208may be spaced apart from the outer edge223and the inner edge222, respectively, of the flexible substrate214. The transition region210is disposed between the control region208and the transducer region204. The dimensions of the transducer region204, the control region208, and the transition region210(e.g., widths W2, W3, and W4, respectively) can vary in different embodiments. In various embodiments, the widths W2, W3, and W4 can be substantially similar or dissimilar. For example, in the pictured embodiment, the width W3 of the transition region210is substantially smaller than the widths W2 and W4 of the transducer region204and the control region208, respectively. The width W2 of the transducer region204and/or the width W3 of the control region208can be between approximately 1 and 5 mm, for example. The width W4 of the transition region210can be any suitable value, including between approximately 1 and 5 mm. The width W2 of the transducer region204and/or the width W3 of the control region208can be between approximately 1 and 5 mm, and/or other suitable values both larger and smaller, for example. The width W4 of the transition region210can be any suitable value, including between approximately 1 and 5 mm and/or other suitable values both larger and smaller, for example.

The transducer array124may include any number and type of ultrasound transducers212, although for clarity only a limited number of ultrasound transducers are illustrated inFIG.2. In the pictured embodiment, the transducer array124includes 40 individual ultrasound transducers212. In a further embodiment, the transducer array124includes 64 ultrasound transducers212. In a further embodiment, the transducer array124includes 32 ultrasound transducers212. Other numbers, both larger and smaller, are both contemplated and provided for. With respect to the types of transducers, in some embodiments, the ultrasound transducers212are capacitive micromachined ultrasound transducers (cMUTs), for example as disclosed in U.S. application Ser. No. 14/812,792, filed Jul. 29, 2015, and titled “Intravascular Ultrasound Imaging Apparatus, Interface Architecture, and Method of Manufacturing,” which is hereby incorporated by reference in its entirety. Incorporating cMUTs minimize the overall profile and diameter of the scanner assembly110because cMUTs are significantly smaller and thinner than several other types of transducers. Moreover, incorporating cMUTs may advantageously increase the ease of assembly by allowing the flexible substrate to be efficiently made atop the silicon wafer on which cMUTs and their conductive traces are already created. In addition, the definition of more precise transducer islands of the cMUT fabrication process and the slim, flexible nature of the silicon wafer may decrease the amount or degree of dicing of the flexible substrate214to enable adequate curvature of the scanner assembly110. In other embodiments, the ultrasound transducers212can be piezoelectric micromachined ultrasound transducers (PMUTs) fabricated on a microelectromechanical system (MEMS) substrate using a polymer piezoelectric material, for example as disclosed in U.S. Pat. No. 6,641,540, which is hereby incorporated by reference in its entirety. In alternate embodiments, the transducer array includes piezoelectric zirconate transducers (PZT) transducers such as bulk PZT transducers, single crystal piezoelectric materials, other suitable ultrasound transmitters and receivers, and/or combinations thereof.

The scanner assembly110may include various transducer control logic, which in the illustrated embodiment is divided into discrete control logic dies206. In various examples, the control logic of the scanner assembly110performs: decoding control signals sent by the PIM104across the cable112, driving one or more transducers212to emit an ultrasonic signal, selecting one or more transducers212to receive a reflected echo of the ultrasonic signal, amplifying a signal representing the received echo, and/or transmitting the signal to the PIM across the cable112. In the illustrated embodiment, a scanner assembly110having 40 ultrasound transducers212divides the control logic across five control logic dies206. Designs incorporating other numbers of control logic dies206, including 8, 9, 16, 17 and more, are utilized in other embodiments. In general, the control logic dies206are characterized by the number of transducers they are capable of driving, and an exemplary control logic dies206drive4,8, and/or16transducers.

The control logic dies are not necessarily homogenous. In some embodiments, a single controller is designated a master control logic die206A and contains the communication interface for the cable112(i.e., the conductors218). Accordingly, the master control circuit may include control logic that decodes control signals received over the cable112, transmits control responses over the cable112, amplifies echo signals, and/or transmits the echo signals over the cable112. The remaining controllers are slave controllers206B. The slave controllers206B may include control logic that drives a transducer212to emit an ultrasonic signal and selects a transducer212to receive an echo. In some embodiments, the master controller206A does not directly control any transducers212. In other embodiments, the master controller206A drives the same number of transducers212as the slave controllers206B or drives a reduced set of transducers212as compared to the slave controllers206B. In an exemplary embodiment, a single master controller206A and four slave controllers206B are provided with ten transducers assigned to each slave controller206B.

The flexible substrate214, on which the transducer control logic dies206and the transducers212are mounted, provides structural support and interconnects for electrical coupling. The flexible substrate214may be constructed to include a film layer of a flexible polyimide material such as KAPTON™ (trademark of DuPont). Other suitable materials include polyester films, polyimide films, polyethylene napthalate films, or polyetherimide films, other flexible printed semiconductor substrates as well as products such as Upilex® (registered trademark of Ube Industries) and TEFLON® (registered trademark of E.I. du Pont). In the flat configuration illustrated inFIGS.2and3, the flexible substrate214has a generally rectangular shape. Although the flexible substrate214is shown herein as having a generally rectangular shape, other embodiments may include a flexible substrate214having alternative shapes (e.g., square). In some instances, the flexible substrate214further comprises metallic interconnection circuitry formed from a malleable metal (such as gold) deposited by means of known sputtering, plating and etching techniques employed in the fabrication of microelectronic circuits upon a chromium adhesion layer on a surface of the flexible substrate214.

The transition region210can be non-rectangular and may include one or more cutouts or slots that increase the flexibility of the flexible substrate214and/or enable the separate regions of the flexible substrate to partially nest within each other to more easily assume a rolled configuration with a reduced profile. In the pictured embodiment, the flexible substrate214includes a slot215disposed within the transition region210. The slot215comprises a sacrificial area that may be removed from the flexible substrate214by any of a variety of fabrication processes known to one of skill in the art, including without limitation, chemical etching, laser etching, mechanical sawing, and/or other suitable etching/removal process. In the pictured embodiment, the slot215is spaced slightly from the control region and is adjacent the transducer array124. Conductive traces216connect the transducer array124, the transducer control logic dies206, and the transmission line bundle or cable112(i.e., the conductors218). The slot215may extend through the flex circuit from a first surface217of the flexible substrate214to an opposite second surface219, as shown inFIGS.2and3, or may be an indentation within the second surface219. The slot215is shaped and configured to facilitate the wrapping or rolling the flexible substrate214into a generally cylindrical shape, as shown inFIGS.4and5, such that the transducer region204forms a complete cylinder (as shown inFIG.6).

As shown and described herein, the flexible substrate214is configured to be wrapped around a support member230(as shown inFIG.3) to form a cylindrical toroid in some instances. Therefore, the thickness T1of the film layer of the flexible substrate214is generally related to the degree of curvature in the final assembled scanner assembly110. The thickness T1extends from the first surface217of the flexible substrate214to the second surface219of the flexible substrate214. In some embodiments, the thickness of the film layer is between 2 μm and 10 μm. In some instances, the thickness T1of the flexible substrate214is twice as thin as the flex circuit of the EagleEye® catheter available from Volcano Corporation, thereby allowing for a smaller bending radius and more “rolls” or layers of the flexible substrate214to wrap around the support member230(shown inFIG.3). In the pictured embodiment, the flexible substrate214includes embedded tracks on which both the ultrasound transducers212and the control logic dies206are mounted, thereby facilitating a thin profile and reduced overall thickness T2of the scanner assembly110in the flat configuration. Having embedded tracks for the transducers212and the control logic dies206enables rolling of the flexible substrate214(and overall scanner assembly110) into a desirable form (e.g., a cylindrical form) with an optimally small diameter, as shown inFIG.5. Such embedded tracks may be formed in the flexible substrate214by any of a variety of fabrication processes known to one of skill in the art. These embedded tracks are in the range of 0.5 to 1 micron and do not substantively add to the overall diameter.

In some embodiments, to electrically interconnect the control logic dies206and the transducers212, the flexible substrate214further includes conductive traces216formed on the film layer. The conductive traces216couple and carry signals between the control logic dies206and the transducers212. In particular, the conductive traces216providing communication between the control logic dies206and the transducers212extend along the flexible substrate214across the transition region210. In some instances, the conductive traces216can also facilitate electrical communication between the master controller206A and the slave controllers206B. The conductive traces216can also provide a set of conductive pads that contact the conductors218of cable112when the conductors218of the cable112are mechanically and electrically coupled to the flexible substrate214. Suitable materials for the conductive traces216include copper, gold, aluminum, silver, tantalum, nickel, and tin, and may be deposited on the flexible substrate214by processes such as sputtering, plating, and etching. In an embodiment, the flexible substrate214includes a chromium adhesion layer. The width and thickness of the conductive traces216are selected to provide proper conductivity and resilience when the flexible substrate214is rolled. In that regard, an exemplary range for the thickness of a conductive trace216and/or conductive pad is between 0.5 and 1.5 μm. For example, in an embodiment, 20 μm wide conductive traces216are separated by 20 μm of space. In some embodiments, the width of the traces can be as small as 3 microns with spaces of 3 microns. The width of a conductive trace216on the flexible substrate214may be further determined by the width of the conductor218to be coupled to the trace/pad. This selected magnitude for the thickness, the width, and separation of the conductive traces216enables the conductive traces216to be sufficiently conductive while maintaining relative flexibility and resiliency so that the conductor lines do not break or malfunction after rolling the flexible substrate214into the cylindrical shape shown inFIGS.4and5. The conductive traces216within the flexible substrate also lend a measure of structure and stiffness to the flexible substrate214. In some instances, the combination of the flexible substrate214and the conductive traces216is referred to as a flex circuit214. Although the flexible substrate214may occasionally described herein as a flex circuit, it is understood that the transducers and/or controllers may be arranged to form the imaging assembly110in other configurations, including those omitting a flex circuit.

The flexible substrate214includes a conductor interface220(shown by dotted lines inFIG.2) in the pictured embodiment. The conductor interface220defines the portion of the flexible substrate214where the conductors218of the transmission line bundle112are coupled to the flexible substrate214. For example, the bare conductors218of the transmission line bundle112are electrically coupled to the flexible substrate214at the conductor interface220. The conductor interface220is positioned in the proximal portion of the flexible substrate214. In some embodiments, the conductor interface220can be a tab or flange extending proximally from the main body of flexible substrate214. In that regard, the main body of the flexible substrate214can refer collectively to the transducer region204, controller region208, and the transition region210. In the illustrated embodiment, the conductor interface220is positioned adjacent the inner edge222and the control region208of the flexible substrate214. In other embodiments, the conductor interface220may be positioned adjacent other parts of the flexible substrate214, such as the outer edge223, the transition region210, or the transducer region204. In other embodiments, the flexible substrate214lacks the conductor interface220. A value of a dimension of the tab or conductor interface220, such as a length L3, can be less than the value of a dimension of the main body of the flexible substrate214, such as the length L1. The length L1 includes the lengths of the proximal portion209, the central portion213, and the distal portion211of the flexible circuit214.

In some embodiments, the substrate forming the conductor interface220is made of the same material(s) and/or is similarly flexible as the flexible substrate214. In other embodiments, the conductor interface220is made of different materials and/or is comparatively more rigid than the flexible substrate214. For example, the conductor interface220can be made of a plastic, thermoplastic, polymer, hard polymer, etc., including polyoxymethylene (e.g., DELRIN®), polyether ether ketone (PEEK), nylon, and/or other suitable materials. As described in greater detail herein, the support member230, the flexible substrate214, the conductor interface220and/or the conductor(s)218can be variously configured to facilitate efficient manufacturing and operation of the scanner assembly110.

According to the illustrated embodiments herein, the scanner assembly110is transitioned from a flat configuration (as shown inFIGS.2and3) to a rolled, generally cylindrical configuration (as shown inFIG.5). For example, in some embodiments, techniques are utilized as disclosed in one or more of U.S. Pat. No. 6,776,763, titled “ULTRASONIC TRANSDUCER ARRAY AND METHOD OF MANUFACTURING THE SAME” and U.S. Pat. No. 7,226,417, titled “HIGH RESOLUTION INTRAVASCULAR ULTRASOUND TRANSDUCER ASSEMBLY HAVING A FLEXIBLE SUBSTRATE,” each of which is hereby incorporated by reference in its entirety.

FIGS.4and5are diagrammatic perspective views of the scanner assembly110shown inFIGS.2and3in a rolled configuration around the support member230, according to aspects of the present disclosure. In particular,FIG.4illustrates the scanner assembly110in a partially rolled configuration around the support member230, andFIG.5illustrates the scanner assembly110in a completely rolled configuration around the support member230.

In the pictured embodiment, the support member230comprises a cylindrical tube having a lumen232extending therethrough. The support member230has a distal end234and a proximal end236. The support member230can be referenced as a unibody in some instances. The support member230can be composed of a metallic material, such as stainless steel, or non-metallic material, such as a plastic or polymer as described in U.S. Provisional Application No. 61/985,220, “Pre-Doped Solid Substrate for Intravascular Devices,” filed Apr. 28, 2014, the entirety of which is hereby incorporated by reference herein. The lumen232is in communication with the exit port116and is sized and shaped to receive the guide wire118(shown inFIG.1). The lumen232can be sized and shaped to accommodate a flexible, inner, proximal member and/or a guide wire.

The support member230can be manufactured accordingly to any suitable process. For example, the support member230can be machined, such as by removing material from a blank to shape the support member230, or molded, such as by an injection molding process. In some embodiments, the support member230may be integrally formed as a unitary structure, while in other embodiments the support member230may be formed of different components, such as a ferrule (i.e., a cylindrical body or ring) and stands (e.g., at the distal end234and a proximal end236of the support member230) that are fixedly coupled to one another. Although not shown inFIGS.2-5, the proximal portion236and distal portion234of the support member230may be shaped and configured to elevate and support the proximal portion209and the distal portion211of the flexible substrate214. In that regard, portions of the flexible substrate214, such as the transducer portion204and the control portion208, can be spaced from a central body portion238(shown inFIG.3) of the support member230extending between the proximal end236and distal end234of the support member230.

The support member230can be substantially cylindrical in some embodiments. Other shapes of the support member230are also contemplated including geometrical, non-geometrical, symmetrical, non-symmetrical, cross-sectional profiles. Different portions the support member230can be variously shaped in other embodiments. The support member230can be shaped to compliment the optimal orientation of the flexible substrate214around the support member230. The proximal end236and distal end234of the support member230can have the same outer diameter or different outer diameters. For example, the support member may have a tapered profile where the distal end234has a larger or smaller outer diameter than the proximal end236. In one embodiment, the proximal end236may have a larger outer diameter than the outer diameters of the distal end234or the central body portion238extending between the distal and proximal end234,236. In some embodiments, an inner diameter of the support member230(e.g., the diameter of the lumen232) can correspondingly increase or decrease as the outer diameter changes. In other embodiments, the inner diameter of the support member230remains the same despite variations in the outer diameter. The support member230may be sized and shaped to allow greater flexibility for the intravascular device. For example, the support member230may compliment the size and shape the rolled flexible substrate214. The dimensions of the support member230can be selected such that the intravascular device102has a diameter between approximately 2 Fr and approximately 10 Fr, for example.

As shown inFIG.3, before commencement of the rolling process, the support member230is positioned atop the control region208on the second surface219of flexible substrate214. In particular, the support member230is positioned adjacent the inner edge222of the flexible substrate214. The support member230is positioned such that the distal portion211of the flexible substrate214is adjacent the distal end234of the support member230and the proximal portion209of the flexible substrate214is adjacent the proximal end236of the support member230. In some embodiments, one or more adhesives can be disposed between various components at the distal portion of the intravascular device102. For example, the flexible substrate214and the support member230may be coupled to one another via an adhesive prior to the rolling process. After the support member230is appropriately positioned, the rolling process begins by rolling the support member230and the flexible substrate214simultaneously in the direction of the arrow A1. Alternatively or additionally, the flexible substrate214may be wrapped around the stationary support member230in the direction of arrow A2. After the rolling process or wrapping process is concluded, as shown in the cross-sectional view illustrated inFIG.6, the scanner assembly110resembles a multilayered cylindrical structure with stacked imaging components, with the support member230forming an inner layer, the control region208forming a middle layer, and the transducer region204forming an outer layer of the scanner assembly110.

FIG.6is a diagrammatic front view of a distal portion of the scanner assembly110in a completely rolled configuration around the support member230, according to aspects of the present disclosure. The scanner assembly110will generally be positioned at a distal portion of the IVUS device102, as shown inFIG.1. The generally cylindrical shape shown inFIGS.5and6is obtained by wrapping or rolling the flat flexible substrate214and embedded imaging components shown inFIG.2around the support member230into an annular, stacked structure by means of the rolling or wrapping process described above with reference toFIGS.3-5. The flexible substrate214is typically formed into a very small cylindrical shape in order to accommodate the space limitations of blood vessels. In such instances, the range of diameters for cylindrically shaped ultrasound transducer assemblies is typically within the range of 0.5 mm to 3.0 mm. However, it is contemplated that an overall diameter D1of the cylindrical, stacked scanner assembly110in the IVUS device102may be on the order of 0.8 mm. to 1.2 mm. In some embodiments, the slim profile and flexible nature of the cMUT transducers on the flexible substrate214allow for a decrease in the overall diameter of the distal end of the IVUS imaging device102and a decrease in the overall stiff length of the scanner assembly110. The thinner profiles of each of the layered components (i.e., the control region208and the transducer region204) allow for a slimmer overall profile and reduced overall diameter of the scanner assembly110. Moreover, the laterally stacked imaging components (i.e., the control region208and the transducer region204) on the flexible substrate214allow for a decrease in the overall stiff length of the scanner assembly110. Both of these features of the scanner assembly110can advantageously increase the flexibility of the IVUS device102and decrease the likelihood of kinking while the intravascular device is maneuvered through a patient's anatomy (e.g., including the coronary vasculature).

To improve acoustic performance, any cavities between the flexible substrate214and the surface of the support member230are generally filled with a backing material246. The liquid backing material246has a relatively low acoustic impedance, and can be introduced between the flexible substrate214and the support member230via passageways in the support member230(not shown). The backing material246fills the space between the support member230and the transducer array124as well as the gaps between adjacent individual transducers212. The backing material246possesses the ability to highly attenuate the ultrasound which is transmitted by the transducer array124. The backing material246also provides support for the transducer elements. The backing material246can be cured to allow it to solidify and set in a sufficiently short period of time to meet manufacturing needs. A number of known materials meeting the above described criteria for a good backing material will be known to those skilled in the art. An example of such a backing material comprises a mixture of epoxy, hardener and phenolic microballoons providing high ultrasound signal attenuation and satisfactory support for the ultrasound transducer assembly.

FIGS.7and8illustrate the scanner assembly300, which includes several components that are substantially similar in form and function to the scanner assembly110described above with respect toFIGS.2-6. In particular,FIG.7is a perspective view of the top of an ultrasound scanner assembly300in an unrolled or flat configuration, according to an embodiment of the present disclosure.FIG.8is a perspective view of the bottom of the scanner assembly300shown inFIG.7in a flat configuration.

The scanner assembly300comprises a flexible substrate314and several embedded imaging components. The flexible substrate314is substantially similar to the flexible substrate214except for the differences described herein.FIG.7illustrates a flexible substrate314prior to the flexible substrate314being rolled into a cylindrical shape. In particular, unlike the flexible substrate214, the flexible substrate314comprises a support region301and a second transition region302in addition to a transducer region304, a control region308, and a first transition region310. The support region301comprises a tab or flange extending from a main body305of the flexible substrate314. The main body305comprises the portion of the flexible substrate314that includes the second transition region302, the control region308, the first transition region310, and the transducer region304. In the pictured embodiment, the second transition region302is part of the main body305and lies between the control region308and the support region301. InFIG.7, the second transition region302has relatively a same length L5 as the main body of the flexible substrate314. In other embodiments, the second transition region302may be sized differently than the main body305of the flexible substrate314. The second transition region302includes a width W5 that facilitates the rolling of the flexible substrate314into separate, nested cylinders, where each cylinder is formed from one of the support region303, the control region208, and the transducer region304. The width W5 of the transition region310can be any suitable value, including between approximately 5 and 15 mm. The support region301defines an inner edge322of the flexible substrate314, and the transducer region304defines the outer edge323of the flexible substrate314. The support region301, the second transition region302, the control region308, the first transition region310, and the transducer region304are all arranged laterally and adjacent to one another along a central axis running along a width W8 of the entire flexible substrate314. This has the advantage of reducing an overall longitudinal length L4 of the scanner assembly300.

The support region301includes a plurality of parallel elongated wires303that are embedded into the flexible substrate314. In the pictured embodiment, the wires303extend the length L4 of the flexible substrate314. In some embodiments, the wires303may measure less or greater in length than the overall longitudinal length L4 of the entire flexible substrate314. The support region301includes a width W6 that measures less than the width W7 of the main body305of the flexible substrate314. The wires303may be formed of any of a variety of rigid elements, including without limitation, embedded tracks and/or metal wires, configured to create a reinforced lumen when the support region301is rolled into a cylindrical shape. In some embodiments, the wires303may be 15 micron Tungsten wires. Different dimensions for the wires303are contemplated.

As shown inFIG.8, the flexible substrate314has a thickness T3extending from a first surface317(shown inFIG.8) to a second, opposite surface318. Similar to the flexible substrate214, the flexible substrate314includes embedded tracks on which both the ultrasound transducers212and the control logic dies206are mounted, thereby facilitating a thin profile and reduced overall thickness T4(shown inFIG.8) of the scanner assembly300in the flat configuration. The lateral arrangement of the ultrasound transducers212and the control logic dies206within a central portion313of the flexible substrate214is substantially similar to the scanner assembly300. This lateral arrangement of the transducers212and the transducer control logic dies206, where a transducer region304and a control region308are positioned side-by-side along a longitudinal width W7 of the flexible substrate, minimizes the overall stiff length L4 of the scanner assembly300. In this embodiment, the stiff length L4 of the scanner assembly300comprises the length of the longest of the three stiff components included on the flexible substrate214, which in this case is the length of the elongated wires303. At least a portion of the scanner assembly300, such as a slot315of the first transition region310, the first transition region310itself, and/or the second transition region302, can be shaped and sized to facilitate the rolling of the flexible substrate314into separate, nested cylinders, where each cylinder is formed from one of the support region303, the control region208, and the transducer region304.

FIG.9is a perspective view of the scanner assembly300in a partially rolled configuration, according to aspects of the present disclosure. More views of the scanner assembly300in a partially rolled configuration are illustrated inFIGS.13-15.FIG.10is a perspective view of a scanner assembly300in a completely rolled configuration, according to aspects of the present disclosure. Given the slender nature of the wires303, the support region310is transformed or re-shaped into a very thin-walled support member330by rolling the inner edge322of the flexible substrate314in the direction of arrow A3. In the pictured embodiment, the support region301is rolled in the direction of the arrow A3into a cylindrical support member330defining an integrated, wire-reinforced lumen335. The luminal walls of the lumen335are formed by the second surface318of the support region301of flexible substrate314. The inner edge322adjacent the support region301forms the inner edge of the roll. As shown inFIGS.9and10, the length L4 of the support member330may exceed the length L5 of the main body305of the flexible substrate314. In other embodiments, the length L5 of the support member330may be equal the length L4 of the main body305of the flexible substrate314, thereby reducing the overall stiff length of the scanner assembly300.

In the pictured embodiment, the second transition region302may be removed or the flexible substrate314may be sliced across the second transition region302to enable the support region301to be rolled into a perfectly cylindrical support member330. In other embodiments, the second transition region302may form a bridge connecting the support member330to the remainder of the scanner assembly300(e.g., the control region308and the transducer region304), and the support member330may be rolled into a spiral form. The second transition region302is a continuous portion of the flexible substrate314, and provides a connection between the cylinder and the rolled prism.

The wires303are configured to lend sufficient stiffness to the flexible substrate314in the support region310to enable the wire-reinforced lumen of the support member330to adequately shield the guidewire during use of the IVUS device102. The wires303provide mechanical reinforcement to the support member330as well as electrical shielding of the lumen335. Moreover, the addition of the wire-reinforced support region301to the flexible substrate314eliminates the need for a separate support member (e.g., the support member230shown inFIGS.3-6). Thus, embodiments with an integrated, wire-reinforced support region301provide for a scanner assembly300having a reduced profile and overall diameter by reducing the overall diameter of the support member. Embodiments with an integrated, wire-reinforced support region301also allow for a more flexible distal tip of the IVUS imaging device102by providing a more flexible support member than the conventional rigid support member (e.g., the support member230described above with reference toFIGS.2-6). In addition, embodiments with an integrated, wire-reinforced support region301enhance manufacturing of the scanner assembly300by facilitating ease of assembly (e.g., by decreasing the complexity and number of parts of the scanner assembly and reducing the time required for manufacture) and by decreasing costs of manufacture.

FIG.11is a diagrammatic perspective view of the top of an exemplary scanner assembly400in a flat configuration, according to aspects of the present disclosure.FIG.12is a diagrammatic perspective view of the bottom of the scanner assembly400in a flat configuration, according to aspects of the present disclosure. Several IVUS imaging devices, such as those including cMUT arrays, utilize an outer window or outer shield to contain adequate acoustic matching medium and to provide adequate electrical and mechanical protection to the imaging components.

The scanner assembly400comprises an outer window region405attached to an exemplary flexible substrate embedded with imaging components in any of a variety of configurations suitable for intravascular imaging. In the pictured embodiment, for the sake of simplicity, the scanner assembly400comprises the outer window region405coupled to the scanner assembly300described above with respect toFIGS.7-10. In the pictured embodiment, the outer window region405is formed as an integrated part of the flexible substrate314. The outer window region405is disposed adjacent the transducer region304at the outer edge323of the flexible substrate314. The outer window region405extends from an outer window edge410to an inner window edge415. The inner window edge415of outer window region405is coupled to the outer edge323of the flexible substrate314. In the pictured embodiment, a third transition region420forms a bridge between the outer window region405and the transducer region304of the flexible substrate314. The third transition region420is shaped as a rectangular portion of flexible substrate and/or window material. In other embodiments, the scanner assembly400lacks a third transition region420, and the outer window region405is coupled directly to the transition region304.

In the flat configuration illustrated inFIGS.11and12, the outer window region405has a generally rectangular shape. Although the outer window region405is shown herein as having a generally rectangular shape, other embodiments may include an outer window region having alternative shapes (e.g., square). The outer window region405has a length L6. The length L6 measures between 2 and 5 mm. The length L6 may be equal or greater in length than the length L4 of the wire-reinforced support region301of the scanner assembly300. In the pictured embodiment, the length L6 is equal to the length L4. In some embodiments, the outer window region405is formed atop an extension of the flexible substrate314. Materials for the outer window region405may be selected for their biocompatibility, durability, hydrophilic or hydrophobic properties, low-friction properties, ultrasonic permeability, and/or other relevant criteria. For example, the outer window region405may include Parylene™. Other suitable materials include polyester, polyethylene, or Polyimide.

FIGS.13,14, and15illustrate the scanner assembly shown inFIG.12in a partially rolled configuration, according to aspects of the present disclosure. In particular,FIG.13is a diagrammatic perspective view of the scanner assembly,FIG.14is a side view of the scanner assembly, andFIG.15is an oblique view of the scanner assembly. In the pictured embodiment, the scanner assembly300is rolled in the direction of the arrow A4, rolling the support region301into a cylindrical support member330defining an integrated, wire-reinforced lumen335, and rolling the control region308into a pentagonal prism shape. As indicated inFIG.14, the outer window region405includes a thickness T5which may be smaller or larger than the thickness T3of the remainder of the flexible substrate T3(shown inFIG.8). In some embodiments, the thickness T3measures between 2 and 10 microns.

FIGS.16,17, and18illustrate the scanner assembly shown inFIG.12in a rolled configuration, according to aspects of the present disclosure. In particular,FIG.16is a diagrammatic perspective view of the scanner assembly,FIG.17is a side view of the scanner assembly, andFIG.18is an oblique view of the scanner assembly. The outer window region405provides a protective layer around the electrical and mechanical components of the scanner assembly300when the scanner assembly400assumes a rolled configuration as shown inFIGS.16-18. In a rolled configuration, the scanner assembly400has an outer profile that is substantially cylindrically-shaped. The outer surfaces of the outer window region405, the transducer region304, and the control region308may form a continuous, spiral surface. Other configurations of the outer window region405is also contemplated. For example, in other embodiments, the flexible substrate314may be sectioned and separated from the outer window region405, which may form a separate, annular cylinder around the scanner assembly300. In some embodiments, the window region405may vary in thickness along its length L6. For example, in some embodiments, the thickness T5of the outer window region405may be greater in a transducer window region430positioned to overlay the transducer region304(i.e., the outer window region405may be thicker in areas overlaying the transducer region304than the areas overlaying the proximal portion209or distal region211of the flexible substrate314). Thus, the outer window region405acts as a shield that circumferentially encases the scanner assembly300and protects it from the surrounding environment during use. Embodiments with an integrated, outer window region405enhance manufacturing of the scanner assembly400by facilitating ease of assembly (e.g, by decreasing the complexity and number of parts of the scanner assembly and reducing the time required for manufacture) and by decreasing costs of manufacture.

FIGS.19and20illustrate the scanner assembly400in a rolled configuration, according to aspects of the present disclosure. In particular,FIG.19is a diagrammatic perspective view of the scanner assembly400, andFIG.20is a diagrammatic front view of a distal portion of the scanner assembly400. The outer window405acts to contain acoustic matching medium425between the outer window region405and the transducer region304. In other embodiments, the scanner assembly400may include a scanner assembly other than the scanner assembly300. For example, the scanner assembly400need not include a wire-reinforced support member330. Regardless, embodiments with an integrated, outer window region405provide for a scanner assembly400having a reduced profile by reducing the overall diameter of the support member. Embodiments with an integrated, outer window region405may allow for a more flexible distal tip of the IVUS imaging device102by providing a more flexible window region than conventional outer membranes. In addition, embodiments with an integrated, outer window region405enhance manufacturing of the scanner assembly400by facilitating ease of assembly (e.g., by decreasing the complexity and number of parts of the scanner assembly and reducing the time required for manufacture) and by decreasing costs of manufacture.

Conventional scanner assemblies may include phased array transducer elements (i.e., an array of transducer elements wrapped or positioned around a central lumen) positioned on a substrate to include trenches defined by the perpendicular side walls of individual transducer elements. By using a flexible substrate with embedded metal tracks on which the ultrasound transducer elements are manufactured, it is possible to roll such a flexible transducer array into a desirable form factor with a very small diameter. Such transducer arrays may consist of rigid silicon islands or silicon strips on which the transducers are built, and flexible substrates connecting adjacent strips at their top side. Trenches are created between the transducer elements, and the trenches are defined by the opposing sidewalls of the adjacent strips. Typically, the trenches between adjacent elements are realized by means of deep reactive ion etching (“DRIE”), which generally renders straight sidewalls that are perpendicular to the substrate surface (i.e., the silicon surface). When these flexible transducer arrays are shaped into a convex shape (e.g., a cylinder), the bottom edges of opposing sidewalls of adjacent transducer elements (i.e., adjacent transducer strips or islands) may collide, thus limiting the attainable radius of curvature. The perpendicular trenches can cause unwanted buckling upon curvature of the transducer elements as the transducer elements contact one another upon curving the substrate. Moreover, perpendicular sidewalls between neighboring transducer elements cause the transducer elements to only partially abut one another upon curving or flexing the substrate, thereby minimizing the potential curvature of the substrate and minimizing the surface area available for transducer elements. This collision and resultant radius of curvature depends upon several factors, including trench width, transducer element thickness, and the desired radius of curvature. For optimal mechanical robustness, the individual transducer elements (i.e., transducer islands or strips) need to have a certain minimum thickness (for example, without limitation, 40 μm). The thickness may range between 30 and 50 microns. To achieve a smaller radius of curvature for a given thickness of the transducer elements, the trench width would need to be increased. However, increasing the trench width or separation between the transducer elements would undesirably reduce the usable active transducer region on the substrate. Alternatively, including non-perpendicular and/or non-straight sidewalls, such that the bottom edges of the transducer elements are spaced further apart than the top edges of the transducer elements (i.e., where the transducer elements connect to the substrate), enables the use of narrow trenches on tightly curved transducers without the risk of colliding opposing bottom edges. This arrangement preserves the maximum surface area of the substrate for active transducer use while also providing for a smaller overall diameter of the rolled transducer region. This advantage increases with a decreasing transducer diameter.

FIGS.21and22illustrate an array440of transducer elements442arranged on a substrate444according to aspects of the present disclosure. In particular,FIG.21is a diagrammatic side view of the array440of transducer elements442a-ewith the substrate444in a flat configuration, andFIG.22is a diagrammatic side view of the array440of transducer elements442a-ewith the substrate444in a curved (or rolled) configuration. As shown inFIG.21, the transducer elements442a-eare arranged linearly on the substrate444. In some embodiments, the substrate444comprises a flexible substrate. The transducer elements442include a thickness T7. The thickness T7may range from 30 to 50 microns. The transducer elements442a-einclude angled sidewalls446a-j. The sidewalls446are non-perpendicular to one another, thereby defining wedge-shaped trenches448between the non-perpendicular sidewalls446. In some examples, the sidewalls446can be angled approximately between 1° and 45°, between 1° and 30°, between 1° and 15°, between 1° and 10°, between 1° and 5°, including values such as 22.5°, 11.25°, 9°, 5.625°, 4.5°, 2.8125°, and/or other suitable values, both larger and smaller. The angle of the sidewalls446can be based on the number of transducer elements442, the diameter of the scanner assembly110, the diameter of the imaging device102, the dimensions of the transducer elements442, the spacing between adjacent transducer elements442, etc. In some embodiments, the sidewalls446of all transducer elements can be angled by the same amount. In other embodiments, the sidewalls446of different transducers elements are angled by different amounts.

As shown inFIG.22, when the substrate444is curved or flexed, the transducer elements442contact one another along the entire length of their sidewalls. For example, the sidewall446bof the transducer element442acomes into full contact with the sidewall446cof the transducer element442b. Thus, this non-perpendicular trench configuration maximizes the surface area available on the substrate for the transducer elements442. Other non-perpendicular separations of the transducer elements442are contemplated. For example, in some embodiments, the sidewalls446may be curved or serpentine, where neighboring sidewalls446are configured to rest against one another or contact one another along at least a portion of the length of the trench448when the flexible substrate444is flexed or in a curved configuration. One method of manufacture may be anisotropic dry etching or an appropriate combination of anisotropic dry etching and isotropic dry etching, such that the desired trench sidewall profile is obtained.

FIG.23is a diagrammatic top view of an exemplary scanner assembly450in a flat configuration, according to aspects of the present disclosure. The scanner assembly450is substantially similar to the scanner assembly110described above with reference toFIGS.2-6. The assembly450includes a flexible substrate452embedded with tracks defining a control region456, a transducer region454, and a transition region455. The flexible substrate452is shown in an unrolled or flat configuration. The transducer region454includes a transducer array458. The control region456includes transducer control logic dies460. The transition region455is disposed between the transducer region454and the control region456. The transition region410includes a slot or cutout457. The flexible substrate452includes multiple conductive traces462configured to connect the transducer array458and the transducer control logic dies460. The transducer array458is a non-limiting example of a medical sensor element and/or a medical sensor element array. The transducer control logic dies460is a non-limiting example of a control circuit.

In the embodiment shown inFIG.23, the transducer region454, the transition region455, and the control region456are laterally disposed (or stacked) adjacent one another within a central portion464of the flexible substrate452. The central portion464of the flexible substrate452extends between a proximal edge464and a distal edge466of the flexible substrate. Both the transducer region454and the control region456are aligned along a central axis CA extending through the central portion464from an inner edge468to an outer edge470of the flexible substrate452. The transducer region454is disposed adjacent the outer edge470of the flexible substrate452. The control region456is disposed adjacent the inner edge468of the flexible substrate452. In some embodiments, the transducer region454and/or the control region456may be spaced apart from the outer edge470and the inner edge468, respectively, of the flexible substrate452. Thus, the transducer array458is positioned laterally (or stacked) relative to the transducer control logic dies460within the central portion464of the flexible substrate452. This lateral arrangement of the transducer array458and the transducer control logic dies460, where the transducer region454and the control region456are positioned side-by-side along a longitudinal width of the flexible substrate, minimizes the overall longitudinal length and the overall stiff length of the scanner assembly450. In this embodiment, the stiff length L8 of the scanner assembly450comprises the length of the longer of the two stiff components included on the flexible substrate452, which in this case is the length of the transducer control logic dies460.

FIGS.24aand24billustrate an exemplary scanner assembly475, according to aspects of the present disclosure. In particular,FIG.24ais a diagrammatic top view of the scanner assembly475in a flat configuration, andFIG.24bis a diagrammatic front view of a distal portion of the scanner assembly475in a rolled configuration. As shown inFIG.24a, the scanner assembly475is assembled in a “double stacking” configuration, where a transducer region476is bracketed on both sides by two separate control regions478,480. In the pictured embodiment, a flexible substrate482includes the first control region478, the transducer region480, and the second control region480arranged laterally (e.g., side-by-side) along a central axis CA extending through the flexible substrate482from a first edge484to a second edge486. The central axis CA extends in parallel with a longitudinal width W8 of the flexible substrate482. As shown inFIG.24b, the scanner assembly475assumes a rolled configuration when each control region478and480is rolled in an opposite direction in the directions of arrows A5and A6to form an annular cylindrical shape. This embodiment gives shorter leads between CMUT elements and the control electronics.

FIG.25is a flow diagram of a method500of assembling an intravascular imaging device. It is understood that the steps of method500may be performed in a different order than shown inFIG.25, additional steps can be provided before, during, and after the steps, and/or some of the steps described can be replaced or eliminated in other embodiments. The steps of the method500can be carried out by a manufacturer of the intravascular imaging device.

At step510, the method500includes obtaining a flexible substrate embedded with conductive traces for coupling a transducer region to a control region. The flexible substrate may be configured to include three distinct regions extending along its length: a proximal portion, a central portion, and a distal portion.

At step520, a control region, a transition region, and a transducer region are arranged laterally along a central axis of the flexible substrate. In some embodiments, the transducer region, the transition region, and the control region are arranged side-by-side within the central portion of the flexible substrate.

At step530, a first support member is obtained. In some embodiments, the first support member is separate from the flexible substrate. It may be sized and shaped so that the flexible substrate can be wrapped around it to form a generally cylindrical scanner assembly.

At step540, the first support member is laid atop or adjacent the control region along an inner edge of the flexible substrate.

At step550, the flexible substrate is rolled or wrapped about the first support member into a cylindrical spiral, with the control region forming an inner cylinder (or prism), the transition region forming a bridge, and the transducer region forming an outer cylinder around the control region.

FIG.26is a flow diagram of a method600of assembling an intravascular imaging device. It is understood that the steps of method600may be performed in a different order than shown inFIG.26, additional steps can be provided before, during, and after the steps, and/or some of the steps described can be replaced or eliminated in other embodiments. The steps of the method600can be carried out by a manufacturer of the intravascular imaging device.

At step610, the method600includes obtaining a flexible substrate embedded with conductive traces for coupling a transducer region to a control region. The flexible substrate may be configured to include three distinct regions extending along its length: a proximal portion, a central portion, and a distal portion.

At step620, a support region, a second transition region, a control region, a first transition region, and a transducer region are arranged laterally along a central axis of the flexible substrate. In some embodiments, the control region, the first transition region, and the transducer region are arranged side-by-side within the central portion of the flexible substrate. The support region comprises a wire-reinforced integral portion of the flexible substrate. It may be sized and shaped so that the flexible substrate can be wrapped around it to form a generally cylindrical scanner assembly.

At step630, the support region is rolled into a cylindrical form to act as a support member for the scanner assembly. The support region forms a support member including a lumen passing therethrough. The lumen may be sized and shaped to accommodate a guidewire or other medical instrument.

At step640, the flexible substrate is rolled or wrapped about the support member into a cylindrical spiral, with the support region forming an inner cylindrical support member, and the control region forming a cylinder (or prism) around the support region, and the transducer region forming an outer cylinder around the control region. In this instance, the support region and the transducer region circumferentially sandwich or envelop the control region. The support region, the transducer region, and the control region remain radially spaced from one another when the scanner assembly is in the rolled configuration.

FIG.27is a flow diagram of a method700of assembling an intravascular imaging device. It is understood that the steps of method700may be performed in a different order than shown inFIG.27, additional steps can be provided before, during, and after the steps, and/or some of the steps described can be replaced or eliminated in other embodiments. The steps of the method700can be carried out by a manufacturer of the intravascular imaging device.

At step710, the method700includes obtaining a flexible substrate embedded with conductive traces for coupling a transducer region to a control region. The flexible substrate may be configured to include three distinct regions extending along its length: a proximal portion, a central portion, and a distal portion.

At step720, a support region, a second transition region, a control region, a first transition region, a transducer region, a third transition region, and an integrated outer window region are arranged laterally along a central axis of the flexible substrate. In some embodiments, the control region, the first transition region, and the transducer region are arranged side-by-side within the central portion of the flexible substrate. The support region may comprise a wire-reinforced integral portion of the flexible substrate. It may be sized and shaped so that the flexible substrate can be wrapped around it to form a generally cylindrical scanner assembly. Some embodiments lack a third transition region.

At step730, the support region is rolled into a cylindrical form to act as a support member for the scanner assembly. The support region forms a support member including a lumen passing therethrough. The lumen may be sized and shaped to accommodate a guidewire or other medical instrument. In other embodiments, the flexible substrate lacks a support region and a second transition region. In such embodiments, the support member is formed separately from the flexible substrate, and is overlaid atop the control region prior to step740.

At step740, the flexible substrate is rolled or wrapped about the support member into a cylindrical spiral, with the support region forming an inner cylindrical support member, and the control region forming a cylinder (or prism) around the support region, the transducer region forming a cylinder around the control region, and the outer window region forming an outer cylinder around the transducer region. In this instance, the outer window region forms a shield circumferentially wrapped around the remainder of the flexible substrate. The window region, the support region, the transducer region, and the control region remain radially spaced from one another when the scanner assembly is in the rolled configuration.