Patent ID: 12201473

DETAILED DESCRIPTION

For the purposes of promoting an understanding of the principles of the present disclosure, reference will now be made to the embodiments illustrated in the drawings, and specific language will be used to describe the same. It is nevertheless understood that no limitation to the scope of the disclosure is intended. Any alterations and further modifications to the described devices, systems, and methods, and any further application of the principles of the present disclosure are fully contemplated and included within the present disclosure as would normally occur to one skilled in the art to which the disclosure relates. For example, while the focusing system is described in terms of cardiovascular imaging, it is understood that it is not intended to be limited to this application. The system is equally well suited to any application requiring imaging within a confined cavity. In particular, it is fully contemplated that the features, components, and/or steps described with respect to one embodiment may be combined with the features, components, and/or steps described with respect to other embodiments of the present disclosure. For the sake of brevity, however, the numerous iterations of these combinations will not be described separately.

FIG.1is a schematic diagram of an intraluminal imaging system100, according to aspects of the present disclosure. The intraluminal imaging system100can be an ultrasound imaging system. In some instances, the system100can be an intravascular ultrasound (IVUS) imaging system. The system100may include an intraluminal imaging device102such as a catheter, guide wire, or guide catheter, a patient interface module (PIM)104, a processing system or console106, and a monitor108. The intraluminal imaging device102can be an ultrasound imaging device. In some instances, the device102can be an IVUS imaging device, such as a solid-state IVUS device.

At a high level, the IVUS device102emits ultrasonic energy from a transducer array124included in scanner assembly110, also referred to as an IVUS imaging assembly, mounted near a distal end of the catheter device. The ultrasonic energy is reflected by tissue structures in the surrounding medium, such as a vessel120, or another body lumen surrounding the scanner assembly110, and the ultrasound echo signals are received by the transducer array124. In that regard, the device102can be sized, shaped, or otherwise configured to be positioned within the body lumen of a patient. The PIM104transfers the received echo signals to the console or computer106where the ultrasound image (including flow information in some embodiments) 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 and206B, illustrated inFIG.2, included in the scanner assembly110to select the particular transducer array element(s), or acoustic element(s), to be used for transmit and receive, (2) providing the transmit trigger signals to the integrated circuit controller chip(s)206A and206B (FIG.2) 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)126of 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. The vessel120may represent fluid filled or surrounded structures, both natural and man-made. The 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 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 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 a plurality of conductors, including one, two, three, four, five, six, seven, or more conductors218(FIG.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 diagrammatic top view of a portion of a flexible assembly110, according to aspects of the present disclosure. The flexible 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 array124includes an array of ultrasound transducer elements212housing transducer elements512(shown inFIG.5). The transducer control logic dies206are mounted on a flexible substrate214into which the transducer elements212have been previously integrated. The flexible substrate214is shown in a flat configuration inFIG.2. Though six control logic dies206are shown inFIG.2, any number of control logic dies206may be used. For example, one, two, three, four, five, six, seven, eight, nine, ten, or more control logic dies206may be used.

The flexible substrate214, on which the transducer control logic dies206and the transducer elements212are 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, liquid crystal polymer, 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 inFIG.2, the flexible substrate214has a generally rectangular shape. As shown and described herein, the flexible substrate214is configured to be wrapped around a support member230(FIG.3) in some instances. Therefore, the thickness of the film layer of the flexible substrate214is generally related to the degree of curvature in the final assembled flexible assembly110. In some embodiments, the film layer is between 5 μm and 100 μm, with some particular embodiments being between 5 μm and 25.1 μm, e.g., 6 μm.

The set of transducer control logic dies206is a non-limiting example of a control circuit. The transducer region204is disposed at a distal portion221of the flexible substrate214. The control region208is disposed at a proximal portion222of the flexible substrate214. The transition region210is disposed between the control region208and the transducer region204. Dimensions of the transducer region204, the control region208, and the transition region210(e.g., lengths225,227,229) can vary in different embodiments. In some embodiments, the lengths225,227,229can be substantially similar or, the length227of the transition region210may be less than lengths225and229, the length227of the transition region210can be greater than lengths225,229of the transducer region and controller region, respectively.

The control logic dies206are not necessarily homogenous. In some embodiments, a single controller is designated a master control logic die206A and contains the communication interface for cable112, between a processing system, e.g., processing system106, and the flexible assembly110. 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 plurality of transducer elements512positioned on a transducer element212to emit an ultrasonic signal and selects a transducer element212to receive an echo. In the depicted embodiment, the master controller206A does not directly control any transducer elements212. In other embodiments, the master controller206A drives the same number of transducer elements212as the slave controllers206B or drives a reduced set of transducer elements212as compared to the slave controllers206B. In an exemplary embodiment, a single master controller206A and eight slave controllers206B are provided with eight transducers assigned to each slave controller206B.

To electrically interconnect the control logic dies206and the transducer elements212, in an embodiment, the flexible substrate214includes conductive traces216formed in the film layer that carry signals between the control logic dies206and the transducer elements212. In particular, the conductive traces216providing communication between the control logic dies206and the transducer elements212extend along the flexible substrate214within 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 1-5 μm. For example, in an embodiment, 5 μm conductive traces216are separated by 5 μm of space. The width of a conductive trace216on the flexible substrate may be further determined by the width of the conductor218to be coupled to the trace or pad.

The flexible substrate214can include a conductor interface220in some embodiments. The conductor interface220can be in a location of the flexible substrate214where the conductors218of the cable112are coupled to the flexible substrate214. For example, the bare conductors of the cable112are electrically coupled to the flexible substrate214at the conductor interface220. The conductor interface220can be tab extending 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 interface220extends from the proximal portion222of the flexible substrate214. In other embodiments, the conductor interface220is positioned at other parts of the flexible substrate214, such as the distal portion221, or the flexible substrate214may lack the conductor interface220. A value of a dimension of the tab or conductor interface220, such as a width224, can be less than the value of a dimension of the main body of the flexible substrate214, such as a width226. 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, Liquid Crystal Polymer (LCP), and/or other suitable materials.

FIG.3illustrates a perspective view of the scanner assembly110in a rolled configuration. In some instances, the flexible substrate214is transitioned from a flat configuration (FIG.2) to a rolled or more cylindrical configuration (FIG.3). 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 SENSING ASSEMBLY HAVING A FLEXIBLE SUBSTRATE,” each of which is hereby incorporated by reference in its entirety.

Depending on the application and embodiment of the presently disclosed invention, transducer elements212may be piezoelectric transducers, single crystal transducer, or PZT (lead zirconate titanate) transducers. In other embodiments, the transducer elements of transducer array124may be flexural transducers, piezoelectric micromachined ultrasonic transducers (PMUTs), capacitive micromachined ultrasonic transducers (CMUTs), or any other suitable type of transducer element. In such embodiments, transducer elements212may comprise an elongate semiconductor material or other suitable material that allows micromachining or similar methods of disposing extremely small elements or circuitry on a substrate.

In some embodiments, the transducer elements212and the controllers206can be positioned in an annular configuration, such as a circular configuration or in a polygon configuration, around a longitudinal axis250of a support member230. It is understood that the longitudinal axis250of the support member230may also be referred to as the longitudinal axis of the scanner assembly110, the flexible elongate member121, or the device102. For example, a cross-sectional profile of the imaging assembly110at the transducer elements212and/or the controllers206can be a circle or a polygon. Any suitable annular polygon shape can be implemented, such as one based on the number of controllers or transducers, flexibility of the controllers or transducers, etc. Some examples may include a pentagon, hexagon, heptagon, octagon, nonagon, decagon, etc. In some examples, the transducer controllers206may be used for controlling the ultrasound transducers512of transducer elements212to obtain imaging data associated with the vessel120.

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 a 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, ('220 application) the entirety of which is hereby incorporated by reference herein. In some embodiments, support member230may be composed of 303 stainless steel. The support member230can be a ferrule having a distal flange or portion232and a proximal flange or portion234. The support member230can be tubular in shape and define a lumen236extending longitudinally therethrough. The lumen236can be sized and shaped to receive the guide wire118. The support member230can be manufactured using any suitable process. For example, the support member230can be machined and/or electrochemically machined or laser milled, such as by removing material from a blank to shape the support member230, or molded, such as by an injection molding process or a micro injection molding process.

Referring now toFIG.4, shown therein is a diagrammatic cross-sectional side view of a distal portion of the intraluminal imaging device102, including the flexible substrate214and the support member230, according to aspects of the present disclosure. The lumen236may be connected with the entry/exit port116and is sized and shaped to receive the guide wire118(FIG.1). 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 and stands242,243, and244, that are fixedly coupled to one another. In some cases, the support member230and/or one or more components thereof may be completely integrated with inner member256. In some cases, the inner member256and the support member230may be joined as one, e.g., in the case of a polymer support member.

Stands242,243, and244that extend vertically are provided at the distal, central, and proximal portions respectively, of the support member230. The stands242,243, and244elevate and support the distal, central, and proximal portions of the flexible substrate214. In that regard, portions of the flexible substrate214, such as the transducer portion204(or transducer region204), can be spaced from a central body portion of the support member230extending between the stands242,243, and244. The stands242,243,244can have the same outer diameter or different outer diameters. For example, the distal stand242can have a larger or smaller outer diameter than the central stand243and/or proximal stand244and can also have special features for rotational alignment as well as control chip placement and connection.

To improve acoustic performance, the cavity between the transducer array212and the surface of the support member230may be filled with an acoustic backing material246. The liquid backing material246can be introduced between the flexible substrate214and the support member230via passageway235in the stand242, or through additional recesses as will be discussed in more detail hereafter. The backing material246may serve to attenuate ultrasound energy emitted by the transducer array212that propagates in the undesired, inward direction.

The cavity between the circuit controller chips206and the surface of the support member230may be filled with an underfill material247. The underfill material247may be an adhesive material (e.g. an epoxy) which provides structural support for the circuit controller chips206and/or the flexible substrate214. The underfill247may additionally be any suitable material.

In some embodiments, the central body portion of the support member can include recesses allowing fluid communication between the lumen of the unibody and the cavities between the flexible substrate214and the support member230. Acoustic backing material246and/or underfill material247can be introduced via the cavities (during an assembly process, prior to the inner member256extending through the lumen of the unibody. In some embodiments, suction can be applied via the passageways235of one of the stands242,244, or to any other suitable recess while the liquid backing material246is fed between the flexible substrate214and the support member230via the passageways235of the other of the stands242,244, or any other suitable recess. The backing material can be cured to allow it to solidify and set. In various embodiments, the support member230includes more than three stands242,243, and244, only one or two of the stands242,243,244, or none of the stands. In that regard the support member230can have an increased diameter distal portion262and/or increased diameter proximal portion264that is sized and shaped to elevate and support the distal and/or proximal portions of the flexible substrate214.

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. As the term is used herein, the shape of the support member230may reference a cross-sectional profile of the support member230. Different portions of the support member230can be variously shaped in other embodiments. For example, the proximal portion264can have a larger outer diameter than the outer diameters of the distal portion262or a central portion extending between the distal and proximal portions262,264. In some embodiments, an inner diameter of the support member230(e.g., the diameter of the lumen236) 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.

A proximal inner member256and a proximal outer member254are coupled to the proximal portion264of the support member230. The proximal inner member256and/or the proximal outer member254can comprise a flexible elongate member. The proximal inner member256can be received within a proximal flange234. The proximal outer member254abuts and is in contact with the proximal end of flexible substrate214. A distal tip member252is coupled to the distal portion262of the support member230. For example, the distal member252is positioned around the distal flange232. The tip member252can abut and be in contact with the distal end of flexible substrate214and the stand242. In other embodiments, the proximal end of the tip member252may be received within the distal end of the flexible substrate214in its rolled configuration. In some embodiments there may be a gap between the flexible substrate214and the tip member252. The distal member252can be the distal-most component of the intraluminal imaging device102. The distal tip member252may be a flexible, polymeric component that defines the distal-most end of the imaging device102. The distal tip member252may additionally define a lumen in communication with the lumen236defined by support member230. The guide wire118may extend through lumen236as well as the lumen defined by the tip member252.

One or more adhesives can be disposed between various components at the distal portion of the intraluminal imaging device102. For example, one or more of the flexible substrate214, the support member230, the distal member252, the proximal inner member256, the transducer array212, and/or the proximal outer member254can be coupled to one another via an adhesive. Stated differently, the adhesive can be in contact with e.g. the transducer array212, the flexible substrate214, the support member230, the distal member252, the proximal inner member256, and/or the proximal outer member254, among other components.

FIG.5is a schematic diagram of a processor circuit, according to aspects of the present disclosure. The processor circuit510may be implemented in the control system130ofFIG.1, the intraluminal imaging system101, and/or the x-ray imaging system151, or any other suitable location. In an example, the processor circuit510may be in communication with intraluminal imaging device102, the x-ray imaging device152, the display132within the system100. The processor circuit510may include the processor134and/or the communication interface140(FIG.1). One or more processor circuits510are configured to execute the operations described herein. As shown, the processor circuit510may include a processor560, a memory564, and a communication module568. These elements may be in direct or indirect communication with each other, for example via one or more buses.

The processor560may include a CPU, a GPU, a DSP, an application-specific integrated circuit (ASIC), a controller, an FPGA, another hardware device, a firmware device, or any combination thereof configured to perform the operations described herein. The processor560may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

The memory564may include a cache memory (e.g., a cache memory of the processor560), random access memory (RAM), magnetoresistive RAM (MRAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM), flash memory, solid state memory device, hard disk drives, other forms of volatile and non-volatile memory, or a combination of different types of memory. In an embodiment, the memory564includes a non-transitory computer-readable medium. The memory564may store instructions566. The instructions566may include instructions that, when executed by the processor560, cause the processor560to perform the operations described herein with reference to the probe110and/or the host130(FIG.1). Instructions566may also be referred to as code. The terms “instructions” and “code” should be interpreted broadly to include any type of computer-readable statement(s). For example, the terms “instructions” and “code” may refer to one or more programs, routines, sub-routines, functions, procedures, etc. “Instructions” and “code” may include a single computer-readable statement or many computer-readable statements.

The communication module568can include any electronic circuitry and/or logic circuitry to facilitate direct or indirect communication of data between the processor circuit510, the probe110, and/or the display132and/or display132. In that regard, the communication module568can be an input/output (I/O) device. In some instances, the communication module568facilitates direct or indirect communication between various elements of the processor circuit510and/or the probe110(FIG.1) and/or the host130(FIG.1).

FIG.6is a diagrammatic cross-sectional view of the ultrasound imaging assembly110illustrating paths of transmitted and received ultrasound pulses over time, according to aspects of the present disclosure.FIG.6includes several depictions of the ultrasound imaging assembly110as ultrasound imaging data is obtained during an imaging procedure.

As shown inFIG.6, multiple ultrasound transducers612are positioned in a circumference around the surface of the ultrasound imaging assembly110. As previously described each of these ultrasound transducers612may be configured to transmit ultrasonic energy into a surrounding anatomy and receive reflections from various structures within the anatomy. For example, the processor circuit510(FIG.5) may be configured to control the circumferential array of ultrasound transducers612to emit multiple ultrasound pulses.

As shown inFIG.6, at a time692, the ultrasound imaging assembly110may excite an ultrasound transducer612(1)positioned on the outer surface of the assembly110. As the transducer612(1)is excited or as a membrane of the transducer612(1)moves in response to receiving an electrical signal, an ultrasound pulse620may be transmitted into the surrounding anatomy. The pulse620may propagate through the anatomy and reflect off a structure650within the anatomy. The reflection630, may propagate back towards the ultrasound imaging assembly110. In response to a command from the processor circuit510, the ultrasound imaging assembly110may receive the reflection630with the same transducer612(1), as shown inFIG.6.

In some embodiments, immediately after the ultrasound transducer612(1)transmits an ultrasound pulse and receives any reflections, the ultrasound system100may repeat the same process described again. For example, the ultrasound transducer612(1)may emit an ultrasound pulse and the same transducer612(1)may receive a reflection of the pulse. The process of repeating the same transmitting and receiving procedure more than one time in succession may be referred to as accumulation.

The arrows693and695illustrated between the depictions of the ultrasound imaging assembly110inFIG.6signify a chronological progression. For example, at a time692, the transducer612(1)may emit an ultrasound pulse620and receive the reflection630. A period of time may then pass after time692, as shown by the arrow693. At time694, the transducer612(1)may emit an additional ultrasound pulse622. The pulse622may propagate through the surrounding medium and reflect off the structure650. The ultrasound imaging assembly110may then select the transducer612(2), positioned adjacent to the transducer612(1), to receive the resulting reflection632. A shown by the arrow695, an additional period of time may then elapse and at time696, the transducer612(1)may emit another ultrasound pulse624. The pulse624may propagate through the anatomy and reflect off the structure650. The imaging assembly110may select the transducer612(3), adjacent to the transducer612(2), to receive the reflection634.

As illustrated by the arrow697, an additional period of time may elapse, and the process may continue in a similar manner. For example, the transducer612(1)may emit additional ultrasound pulses and the imaging assembly110may walk through the neighboring transducers in turn to receive reflections. For example, after the time period697, the transducer612(4)may receive a reflection of a pulse emitted by the transducer612(1), followed by the transducers612(5),612(6), and so on.

In some embodiments, the processor circuit510(FIG.5) of the system100may determine which transducers612will be selected to receive reflections based on the characteristics of the emitted ultrasound pulse. For example, as will be described in more detail with reference toFIG.8, an emitted ultrasound pulse may propagate from a transmitting transducer according to a radiation pattern. The radiation pattern may depend on the size and shape of the transducer and the frequency of the ultrasound pulse, among other contributing factors. A receiving transducer may receive reflections according to a similar radiation pattern. The receiving radiation pattern may also depend on the size and shape of the receiving transducer as well as the frequency of reflections received. In some embodiments, the processor circuit510(FIG.5) may determine the number of allowable transducers along the circumference between a transmitting and a receiving transducer based on the radiation patterns of the transmitting and receiving transducers. For example, the processor circuit510may specify that a transducer act as a receiving transducer for a chosen transmitting transducer if the structure650being imaged lies within the radiation pattern of both the transmitting transducer and the receiving transducer. In some embodiments, all transducers with radiation patterns which overlap with the radiation pattern of the transmitting transducer may be selected as receiving transducers and may iteratively be chosen to receive reflections from an emitted pulse in turn, as described with reference toFIG.6.

In the example shown inFIG.6, after all receiving transducers have received reflections from the ultrasound pulse emitted by the transducer612(1), the same process may be repeated with transducer612(2)acting as the transmitting transducer. Specifically, transducer612(2)may emit an ultrasound pulse. The same transducer612(2)may receive any reflections. Then, transducer612(2)may emit another ultrasound pulse and transducer612(3)may receive reflections, and so on. This sequence may be followed until each transducer612has acted as the transmitting transducer and all corresponding receiving transducer has received reflections. The acquired data may then be processed to generate and display an intravascular ultrasound (IVUS) image.

As described inFIG.6, the intravascular ultrasound imaging system includes an IVUS imaging device configured to be positioned within a blood vessel of a patient and the IVUS imaging device includes a circumferential array of acoustic elements. The processor circuit510(FIG.5) is configured to control the circumferential array to emit and/or receive multiple ultrasound pulses.

A transmitting transducer, such as transducer612(1)at time694, and a receiving transducer, such as transducer612(2)at time694, intended to transmit an ultrasound pulse and receive a resulting reflection respectively may be referred to as a transmit-receive pair. The sequence of the transmitting a pulse with the transmitting transducer and subsequently receiving the reflection with the receiving transducer may be referred to as a transmit-receive event. In this way, the time692shown inFIG.6may be a single transmit receive event with a transmit-receive pair including the same transducer,612(1). Similarly, the time696may be a single transmit-receive event with a transmit pair including612(1)and612(3).

FIG.7is a diagrammatic view of an intraluminal ultrasound image700with an artifact caused by a high pulse repetition frequency, according to aspects of the present disclosure.FIG.7includes a depiction of the ultrasound imaging assembly110, as well as an artifact710.

The timing and sequence of transmitting and receiving ultrasound pulses, as described with reference toFIG.6, can have implications on data collected and the resulting image. For example, the rate at which ultrasound pulses are emitted by the transducers612(FIG.6) can lead to inaccuracies in the ultrasound data and artifacts in the ultrasound images created. The pulse repetition interval (PRI) may refer to the amount of time between emissions of ultrasound pulses. In some embodiments, a PRI for an ultrasound imaging assembly may be any suitable number, such as 1 μs, 10 μs, 100 μs or more, or any suitable number between these values. As the PRI is decreased, there is less time for an emitted pulse to be attenuated before the next pulse is emitted. If the PRI is too low, a receiving transducer may receive ultrasound data from multiple ultrasound pulses, leading to inaccuracies. For example, referring again toFIG.6, at time692, transducer612(1)emits a pulse620and receives the reflection630. At time694, transducer612(1)emits another pulse622and transducer612(2)receives reflection632. If the time between time692and694is too short, transducer612(2)may receive some ultrasonic energy left over from pulse620. This leftover energy may be referred to as reverberation. Reverberation from past ultrasound pulses may be effectively attenuated by surrounding tissues or other structures. In some anatomies, however, reverberation may be increased by hard plaque formations or stents in the anatomy.

The effect of receiving transducers receiving reverberation energy from previous pulses is shown inFIG.7as artifact710. Artifact710makes it appear to a user of the system100as if a structure is present within the lumen720. When in fact, no such structure is present. The artifact710may also be referred to as a false target. As the PM is decreased, artifacts such as artifact710inFIG.7are more prominent.

FIG.8is a diagrammatic cross-sectional view of transmitting and receiving radiation patterns of ultrasound transducers of the ultrasound imaging assembly110, according to aspects of the present disclosure.FIG.8includes a transmitting transducer812(1)and a receiving transducer812(2)with a transmitting radiation pattern820, a receiving radiation pattern822, and an overlapping region824.FIG.8also depicts a partial cross-sectional portion of the ultrasound imaging assembly110showing two transducers of the circumferential array of transducers.

The circumferential array can include features similar or identical to the array124(FIGS.1and2). The circumferential array may include any number of ultrasound transducers, two of which are illustrated inFIG.8. The ultrasound transducers812(1)and812(2)can include features similar or identical to the transducers212ofFIGS.2,3, and4. The ultrasound transducers812(1)and812(2)can emit ultrasound pulses and/or receive ultrasound echoes or reflections corresponding to the emitted ultrasound pulses. The ultrasound transducers812(1)and812(2)can be referenced as acoustic elements, transducer elements, or ultrasound transducer elements, or by any other suitable term. The ultrasound transducers812(1)and812(2)can emit an ultrasound pulse in response to an electrical signal that excites the transducers to vibrate. The ultrasound transducers812(1)and812(2)can receive an ultrasound echo by vibrating as a result of incident acoustic energy and converting the received acoustic energy into an electrical signal. The ultrasound transducer812(1)can be a single acoustic element or multiple acoustic elements. Similarly, the ultrasound transducer812(2)can be a single acoustic element or multiple acoustic elements. In embodiments with multiple acoustic elements812, acoustic elements can be adjacent to one another around the array (e.g., without intervening acoustic elements between the acoustic elements) or can be near or otherwise proximate to one another on the array505(e.g., with intervening acoustic elements between the acoustic elements). Each of the acoustic elements of the circumferential array can be oriented differently based on its circumferential position around the array. For example, acoustic element812(1)is oriented differently than the acoustic element812(2). For example, the emitting or outer surfaces of the transducers812(1)and812(2)can be tangential to the surface of the array and/or the surface of the imaging assembly110(FIG.1,3) at their respective positions. For example, the transducers812(1)and812(2)may emit ultrasound pulses and/or receive ultrasound echoes primarily in a direction perpendicular or normal to the outer surface of the imaging assembly110.

The radiation pattern820of the transducer812(1)can be representative of the direction of acoustic energy (e.g., ultrasound pulses and/or ultrasound echoes) that can be produced or received by the transducer812(1). Similarly, the radiation pattern822of the transducer812(2)can be representative of the direction of acoustic energy that can be produced or received by the transducer812(2). The two-dimensional (2D) shape of the radiation patterns820and822illustrated inFIG.8is merely exemplary. The radiation patterns820and822may extend in three-dimensional (3D) space. In addition, the shape of the radiation patterns820and822shown inFIG.8may be merely exemplary. As previously described, the shape of the radiation patterns820and822may be determined by various characteristics of the transducers812, the imaging assembly110, the emitted or received pulses or reflections, and the surrounding anatomy, etc.

As shown inFIG.8, the radiation patterns820and822may overlap in a region824. The region824may be referred to as the combined radiation pattern of the transducers812(1)and812(2). In some embodiments, the transmitting transducer812(1)and the receiving transducer812(2)may be referred to as a transmit-receive aperture. As shown inFIG.8, the transmit element812(1)may be spaced from the receiving element812(2). Correspondingly, the radiation patterns820and822are also spaced apart. In some embodiments, transmit element and the receive element can be the same element such that there is no spacing between the transmit and receive elements. In such embodiments, the radiation patterns820and820may be the same pattern.

In the example shown inFIG.8, the structure850is located in the environment around the IVUS imaging assembly110. The structure850may scatter and/or reflect acoustic energy emitted by the transmit element812(1). The structure850may be a structure within the anatomy of a patient, such as a vessel wall, an obstruction, blood, or other structure, or may be any other structure, including synthetic materials such as a stent.

The combined radiation pattern824is representative of the region in which a structure may be imaged by the transmitting transducer812(1)and the receiving transducer812(2). In this way, objects within the radiation pattern of a particular transducer may be said to be within the field of view (FOV) of that transducer. An object, such as the structure850, within the combined radiation pattern824of transducers812(1)and812(2)may be within the FOV of these two transducers. As previously mentioned, the field of view for each transducer as defined by its radiation pattern while either transmitting or receiving may define the distance by which a transmitting transducer and receiving transducer may be separated along an array. This distance may then determine how many receiving transducers may be used in conjunction with a single transmitting transducer.

The present disclosure describes systems, devices, and methods that maximize the likelihood that a receiving transducer only receives ultrasound energy corresponding to the transmit-receive event of a given transmit-receive pair and does not receive any reverberation from previous transmit-receive events. This advantageously minimizes reverberation artifacts in the resulting IVUS image, which is an improvement in IVUS image quality and the user's ability to understand the IVUS image and make clinical decisions based on the image.

FIG.9Ais a diagrammatic cross-sectional view of transmitting and receiving radiation patterns for two pairs of ultrasound transducers spaced from one another on the ultrasound imaging assembly, according to aspects of the present disclosure.FIG.9Amay illustrate two separate transmit-receive events. These transmit-receive events may occur at different times or may occur simultaneously.

FIG.9Aillustrates a circumferential array of transducer elements912positioned around the exterior of the scanner assembly110. In some embodiments, the processor circuit may configured to control the circumferential array to emit multiple ultrasound pulses. These ultrasound pulses may include a pulse emitted by the ultrasound transducer912(1)inFIG.9A. The pulse emitted by the ultrasound transducer912(1)is illustrated by the radiation pattern920extending radially outward from the imaging assembly110. In some embodiments, an ultrasound pulse may be emitted by more than one transducer element. For example, the ultrasound transducers912(1)and912(2)may together form a subset of the circumferential array of ultrasound transducers. This subset may include additional ultrasound transducers. In some embodiments, a subset of ultrasound transducers may include only one transducer. The ultrasound transducers which together form a subset and emit an ultrasound pulse may be positioned adjacent to each other, like the transducers912(1)and912(2), or may be spaced from each other according to any suitable configuration. In some embodiments, the ultrasound transducer(s) which emit(s) an ultrasound pulse may be referred to as an aperture.

At one particular time, the processor circuit510(FIG.5) may be configured to control the circumferential array of transducer elements912and cause the transducer912(1)to emit an ultrasound pulse. Immediately after the transducer912(1)has emitted the pulse, the processor circuit may cause the transducer912(1)to receive one or more reflections or echoes associated with the pulse. Both the transmit and receive radiation patterns may be illustrated by the pattern920inFIG.9A.

After the transducer912(1)has transmitted a pulse and received any reflections or echoes, the processor circuit may control the circumferential array and cause a different transducer912(a), or subset of transducers which may include one or more transducers, to emit an additional ultrasound pulse. The transducer912(a)may be any transducer912of the circumferential array. In some embodiments, the transducer912(a)is a different transducer from transducer912(1). In some embodiments, the transducer912(a)is spaced from the transducer912(1)by some angle990. The angle990separating transducer912(1)from transducer912(a)may be any suitable angle. The minimum acceptable value of angle990may be determined by the processor circuit510(FIG.5) based on the radiation patterns associated with the transducers912(1)and912(a). For example, as shown inFIG.9A, the radiation pattern920may correspond to the transducer912(1)and the radiation pattern930may correspond to the transducer912(a). The minimum value of angle990may be smallest value at which the radiation patterns920and930do not overlap. If the angle990is chosen such that the radiation patterns920and930do not overlap, when a pulse is emitted and received first by transducer912(1)in the region of pattern920and a second pulse is emitted and received by transducer912(a)in the region of pattern930immediately after, any leftover acoustic energy, or reverberation from the first pulse of912(1)is not likely to be received by transducer912(a)because of the physical separation between the transducers.

As described with reference toFIG.6, emitting and receiving an ultrasound pulse may be performed by two different ultrasound transducers (i.e., a transmit-receive pair). For example, after the transducer912(1)has emitted and received an ultrasound pulse and transducer912(a)has emitted and received an ultrasound pulse, a transmit-receive pair of transducers912(1)and912(2)may transmit and receive an additional pulse. As shown inFIG.9A, the radiation pattern920may correspond to a transmitted pulse from transducer912(1)and the radiation pattern922may correspond to a received reflection received by transducer912(2). Combined, these radiation patterns may define the region924. The transmit receive pair of transducers912(1)and912(2)may, therefore, have a field of view corresponding to this region924.

After the transmit-receive pair of transducers912(1)and912(2)have completed respectively transmitting and receiving an ultrasound pulse, the transmit-receive pair of transducers912(a)and912(b)may perform a similar transmit-receive event. For example, the radiation pattern930may correspond to a transmitted pulse from transducer912(a)and the radiation pattern932may correspond to a received reflection received by transducer912(b). Combined, these radiation patterns may define the region934. The transmit receive pair of transducers912(a)and912(b)may, therefore, have a field of view corresponding to this region934. In the example described, because the angle990is chosen such that the radiation patterns920,922, and924do not overlap with the patterns930,932, and934, when a pulse is emitted and received first by transducer pair912(1)and912(2)and a second pulse is emitted and received by transducer pair912(a)and912(b)immediately after, any leftover acoustic energy, or reverberation from the first pulse of912(1)is not likely to be received by transducer912(b)because of the physical separation between the transducers. Stated differently, the transducers912(a)and912(b)are out of the field of view (also referred to as a line of sight) of the transducers912(1)and912(2). Similarly, the transducers912(1)and912(2)are out of the line of sight of the transducers912(a)and912(b).

As shown in subsequent figures, the angle990may be any suitable angle. As will be discussed in more detail, both the value of the angle990and the value of the pulse repetition interval (PRI) (i.e., the time between ultrasound pulses), may be adjusted with differing effects on the amount of unwanted reverberation received by receiving transducers. Adjusting these values may also, then, affect the location and extent of artifacts or false targets in resulting IVUS images.

As described,FIG.9Aillustrates how a processor circuit510may control a circumferential array of ultrasound transducers to emit a first ultrasound pulse emitted by a first subset of the circumferential array and a second ultrasound pulse emitted by a second subset of the circumferential array. The first subset of the circumferential array may include one or more ultrasound transducers. The second subset of the circumferential array may include one or more ultrasound transducers. The second subset of the circumferential array may include different ultrasound transducers than the first subset of the circumferential array. The second ultrasound pulse occurs immediately after the first ultrasound pulse in a succession of the multiple ultrasound pulses. The first subset of ultrasound transducers of the circumferential array and the second subset of ultrasound transducers of the circumferential array are circumferentially spaced from one another around the circumferential array and the second subset is outside of a line of sight of first ultrasound echoes associated with the first ultrasound pulse. The processor circuit510(FIG.5) may also be configured to generate an IVUS image based on the ultrasound pulses and output the IVUS image to a display in communication with the processor circuit. In some embodiments, the first the first ultrasound pulse is associated with a first aperture of the circumferential array, and the second ultrasound pulse is associated with a second aperture of the circumferential array. In some embodiments, the processor circuit510(FIG.5) is configured to control the circumferential array to receive the first ultrasound echoes and receive second ultrasound echoes associated with the second ultrasound pulse and generate the IVUS image based on ultrasound data representative of the first ultrasound echoes and the second ultrasound echoes.

In some embodiments, the processor circuit510is configured to control the circumferential array to obtain IVUS imaging data. The IVUS imaging data is representative of a first transmit-receive aperture comprising a first combined radiation pattern and associated with at least one first acoustic element of the circumferential array and a second transmit-receive aperture comprising a second combined radiation pattern and associated with at least one second acoustic element of the circumferential array. The IVUS imaging data representative of the second transmit-receive aperture is obtained immediately after the IVUS imaging data representative of the first transmit-receive aperture. In some embodiments, the at least one first acoustic element and the at least one second acoustic element are circumferentially spaced from one another around the circumferential array such that the first combined radiation pattern and the second combined radiation pattern are non-overlapping or minimally overlapping.

FIG.9Bis a diagrammatic cross-sectional view of transmitting and receiving radiation patterns for two pairs of ultrasound transducers spaced from one another on the ultrasound imaging assembly, according to aspects of the present disclosure.FIG.9Bmay illustrate a sequence of transmitting and receiving ultrasound pulses and reflections, however, the transmit-receive pairs may be spaced from one another by some angle992which is smaller than the angle990ofFIG.9A, causing the radiation patterns of the transmit-receive pairs to overlap. This overlap950may cause reverberations from the first pulse to be received by the receiving transducer associated with the second pulse causing artifacts or false targets.

At one particular time, the transducer912(1)may emit an ultrasound pulse as illustrated by the radiation pattern920. The transducer912(2)may receive reflections of this first pulse as shown by the radiation pattern922. Combined, these radiation patterns may define the region924. The transmit receive pair of transducers912(1)and912(2)may, therefore, have a field of view corresponding to this region924.

After the transmit-receive pair of transducers912(1)and912(2)have completed respectively transmitting and receiving an ultrasound pulse, the transmit-receive pair of transducers912(c)and912(d)may perform a similar transmit-receive event. For example, the radiation pattern940may correspond to a transmitted pulse from transducer912(c)and the radiation pattern942may correspond to a received reflection received by transducer912(d). Combined, these radiation patterns may define the region944. The transmit-receive pair of transducers912(c)and912(d)may, therefore, have a field of view corresponding to this region944. In the example described, because the angle992is chosen such that the radiation patterns920,922, and924overlap with the patterns940,942, and944, as shown by the region950, when a pulse is emitted and received first by transducer pair912(1)and912(2)and a second pulse is emitted and received by transducer pair912(c)and912(d)immediately after, some leftover acoustic energy, or reverberation, from the first pulse of912(1)may be received by transducer912(d)because of the smaller physical separation between the transducers. Stated differently, the transducers912(c)and912(d)are within of the field of view (also referred to as a line of sight) of the transducers912(1)and912(2). Similarly, the transducers912(1)and912(2)are within the line of sight of the transducers912(c)and912(d). The example illustrated inFIG.9Bmay be one in which the separation angle992between the transmit-receive pair912(1)and912(2)and the transmit-receive pair912(c)and912(d)is too small to effectively reduce reverberation. In one exemplary embodiment, the minimum spacing between two consecutively emitting transmit-receive pairs may be 60 degrees. In another exemplary embodiment, the minimum spacing may be 45 degrees. However, the minimum spacing between two consecutively emitting transit-receive pairs may depend on the angular sensitivity of the transducers, the geometry and/or orientation of the transducer elements, the driving frequency of the transmitting pulse, or other factors. At this spacing, the combined radiation patterns of two transmit-receive pairs of transducers is said to be minimally overlapping. In some embodiments, the combined radiation pattern of one transmit-receive pair of transducers and the combined radiation pattern of a second transmit-receive pair of transducers are non-overlapping or minimally overlapping.

In some embodiments, two transmit-receive pairs of ultrasound transducers may be minimally overlapping when the level of reverberation from the first transmit-receive pair and received by the second transmit-receive pair is a certain level below the thermal noise of the ultrasound transducers. For example, in some embodiments, the system100or a user of the system100may determine that two transmit-receive pairs of transducers are minimally overlapping when reverberation signals between the two are 3 dB below the thermal noise level. The thermal noise level, levels corresponding to emitted pulses and received reflections, and reverberation, may all depend on various aspects of the transducer array, such as the geometry and/or orientation of the array, the size and/or sensitivity of the transducers including the angular sensitivity of the transducers, the frequency of the emitted pulses, the excitation voltage corresponding to the pulse signal, coherence of transmitted and/or received signals, or other factors. In some embodiments, reverberation signals which are beamformed and in the ultrasound range of 62 dB post beamforming will create an artifact in the image. In some embodiments, 62 dB may correspond to a level of speckle noise. However, acquired data before beamforming in IVUS imaging may be in the signal-to-noise ratio range of 26 to 40 dB range above the thermal noise of the transducers.

FIG.9Cis a diagrammatic cross-sectional view of transmitting and receiving radiation patterns for two pairs of ultrasound transducers spaced from one another on the ultrasound imaging assembly, according to aspects of the present disclosure.FIG.9Cmay illustrate a sequence of transmitting and receiving ultrasound pulses and reflections, however, the transmit-receive pairs may be spaced from one another by some angle994which is larger than the angle990ofFIG.9A. This angle994may correspond to a 180 degree separation. In other words, the transmit transducer912(1)is on the opposite side of the circumferential array as the transmit transducer912(e).

At one particular time, the transducer912(1)may emit an ultrasound pulse as illustrated by the radiation pattern920. The transducer912(2)may receive reflections of this first pulse as shown by the radiation pattern922. Combined, these radiation patterns may define the region924. The transmit receive pair of transducers912(1)and912(2)may, therefore, have a field of view corresponding to this region924.

After the transmit-receive pair of transducers912(1)and912(2)have completed respectively transmitting and receiving an ultrasound pulse, the transmit-receive pair of transducers912(e)and912(f)may perform a similar transmit-receive event. For example, the radiation pattern950may correspond to a transmitted pulse from transducer912(c)and the radiation pattern952may correspond to a received reflection received by transducer912(d). Combined, these radiation patterns may define the region954. The transmit-receive pair of transducers912(e)and912(f)may, therefore, have a field of view corresponding to this region954. In the example described, because the angle994is creates the maximum spacing between the radiation patterns920,922, and924and the patterns960,962, and964, when a pulse is emitted and received first by transducer pair912(1)and912(2)and a second pulse is emitted and received by transducer pair912(e)and912(f)immediately after, there is the least likelihood of leftover acoustic energy, or reverberation, being received by transducer912(f).

FIG.10is a diagrammatic cross-sectional view of the ultrasound imaging assembly illustrating paths of transmitted and received ultrasound pulses over time, according to aspects of the present disclosure.FIG.10may illustrate an exemplary pulse emission sequence.

As shown inFIG.10, a scanner assembly110is illustrated including multiple ultrasound transducers1012. The transducers1012may be substantially similar to any of the other transducers described herein. In the example shown inFIG.10, the scanner assembly may include 64 ultrasound transducers1012, though each transducer1012may or may not be illustrated inFIG.10. As previously mentioned, the scanner assembly110may include any suitable number of transducers1012.

At time1090, the processor circuit510(FIG.5) may cause an ultrasound transducer1012(1)to emit an ultrasound pulse1020. The ultrasound pulse1020may propagate through the surrounding medium and reflect off a structure1050. This reflection may create a reflection1030which propagates back towards the scanner assembly110. The processor circuit510may cause the same transducer1012(1)to receive this reflection1030.

As shown by the arrow1091, some amount of time may pass after the ultrasound transducer1012(1)receives the reflection1030and before the next transmit-receive event occurs at time1092. In some embodiments, however, no time may pass between the time ultrasound transducer1012(1)receives reflection1030, but the transducer1012(33)may emit an ultrasound pulse immediately after the reflection1030is received. As previously mentioned, in some embodiments, the transducers1012(1)and1012(33)may be configured to emit ultrasound pulses simultaneously such that time1090and1092are the same time. In some embodiments, the transducer1012(33)may be configured to emit an ultrasound pulse at some time after the transducer1012(1)emits the pulse1020but before it receives the reflection1030.

At time1092, a transducer element1012(33)may emit a pulse1022. The pulse1022may propagate radially outward through the surrounding medium and reflect off a structure1052. This reflection may create a reflection1032which propagates back towards the scanner assembly110. The processor circuit510may cause the same transducer1012(33)to receive this reflection1032.

As shown by the arrow1093, some amount of time may or may not pass after the ultrasound transducer1012(33)receives the reflection1032and before the next transmit-receive event occurs at time1094.

At time1094, the transducer element1012(1)may emit a pulse1024. The pulse1024may propagate radially outward through the surrounding medium and reflect off the structure1050. This reflection may create a reflection1034which propagates back towards the scanner assembly110. The processor circuit510may cause a transducer1012(2)to receive this reflection1034.

As shown by the arrow1095, some amount of time may or may not pass after the ultrasound transducer1012(2)receives the reflection1034and before the next transmit-receive event occurs at time1096.

At time1096, the transducer element1012(33)may emit an additional pulse1026. The pulse1026may propagate radially outward through the surrounding medium and reflect off the structure1052. This reflection may create a reflection1036which propagates back towards the scanner assembly110. The processor circuit510may cause a transducer1012(34)to receive this reflection1036.

This process may continue until all receiving transducers respectively associated with the transmitting transducers1012(1)and1012(33)have received reflections. For example, after the time1096, the transducer1012(1)may emit an additional pulse and a transducer1012(3)may receive it. Then the transducer1012(33)may emit an additional pulse and a transducer1012(35)may receive it and so on. Then, the transducers1012(2)and1012(34)may serve as the transmitting transducers and the process may continue.

In the example shown inFIG.10, the ultrasound transducer1012(1)may be referred to as a first subset of the circumferential array. At time1090, the first subset may emit a pulse and receive reflections of that pulse. The transducer1012(33)may be referred to as a second subset of the circumferential array. At time1092, the second subset may emit a pulse and receive reflections of that pulse. The transducer1012(2)may be referred to as third subset of the circumferential array. At time1094, the first subset may emit a pulse and the third subset may receive reflections from that pulse. The transducer1012(34)may be referred to as a fourth subset of the circumferential array. At time1096, the second subset may emit a pulse and the fourth subset may receive reflections from that pulse. In the example shown, the third subset is within the line of sight of the first ultrasound echoes, and the fourth subset is within the line of sight of the second ultrasound echoes. In some instances, such as at time1090, the first subset and the third subset are identical. At time1092, the second subset and the fourth subset may be identical.

In some embodiments, additional repetitive transmit-receive events may be included in the sequence described with reference toFIG.10. For example, after time1092, the processor circuit510may cause the scanner assembly to repeat the transmit-receive events of time1090and1092. Specifically, after transducer1012(33)has emitted and received a pulse, transducer1012(1)may again transmit and receive a pulse. Then the transducer1012(33)may again transmit and receive a pulse. Similarly, after the time1096, the transmit-receive events of1094and1096may be repeated. This process may be referred to as accumulation and may increase the accuracy of ultrasound data received. In some embodiments, the transmit-receive events may be repeated in succession. For example, the transducer1012(1)may emit and receive a pulse two times in succession and then the transducer1012(33)may emit and receive a pulse two times in succession. In other words, the transit-receive event of time1090may be completed twice and immediately afterward, the transmit-receive event of1092may be completed twice. In this way, the processor circuit510may cause the scanner assembly to emit an additional first ultrasound pulse occurring immediately after the first ultrasound pulse in the succession of the plurality of ultrasound pulses and an additional second ultrasound pulse occurring immediately after the additional second ultrasound pulse in the succession of the plurality of ultrasound pulses.

For pedagogical purposes, the sequence of which ultrasound transducers are configured to transmit and which are configured to receive at what times may be described with the following shorthand. An instruction for the first transducer, inFIG.10this would be transducer1012(1), to emit an ultrasound pulse may be written as “Tx1.” An instruction for the first transducer to receive an ultrasound reflection may be written as “Rx1.” An instruction for the second transducer, inFIG.10this would be transducer1012(2), to emit an ultrasound pulse may be written as “Tx2” and so forth. A transmit-receive event in which the first transducer is to emit an ultrasound pulse and the second transducer is to receive may be written as “Tx1Rx2.” Different transmit-receive events may be separated by an arrow. A written sequence corresponding to that described inFIG.10and corresponding to an imaging assembly110including 64 transducer elements and spacing different transmit receive pairs by 180 degrees may therefore be as follows:
Tx1Rx1→Tx33Rx33→Tx1Rx2→Tx33Rx34→Tx1Rx3→Tx33Rx35→ . . .
After the last receiving transducer associated with the first transmitting transducer has completed receiving reflections, the second transducer may act as the transmitting transducer and the process resumes as follows:
Tx2Rx2→Tx34Rx34→Tx2Rx3→Tx34Rx35→Tx2Rx4→Tx34Rx36→ . . .
After the last receiving transducer associated with the second transmitting transducer has completed receiving reflections, the third transducer may act as the transmitting transducer and so on until the transmitting transducer32and64have emitted ultrasound pulses as follows:
Tx32Rx32→Tx64Rx64→Tx32Rx33→Tx64Rx1→Tx32Rx34→Tx64Rx2→ . . .
After the last receiving transducer associated with the last transmitting transducer has completed receiving reflections, the ultrasound data acquisition process may be complete.

It is also noted, that any accumulation transmit-receive events may be included in these sequences. For example, a sequence including an accumulation where each transmit-receive event is completed twice may progress as follows:
Tx1Rx1→Tx33Rx33→Tx1Rx1→Tx33Rx33→Tx1Rx2→Tx33Rx34→ . . .
Alternatively, it may be arranged in this manner:
Tx1Rx1→Tx1Rx1→Tx33Rx33→Tx33Rx33→Tx1Rx2→Tx1Rx2→ . . .
It is understood that a sequence may include any suitable number of accumulation events and may be organized according to any suitable pattern. For example, a transmit-receive event may be repeated, two, three, four, or more times.

FIG.11Ais a diagrammatic cross-sectional view of the ultrasound imaging assembly illustrating paths of transmitted and received ultrasound pulses, according to aspects of the present disclosure.FIGS.11A through11Dillustrate that a transmit-receive sequence may include more than two transmit-receive pairs with spacing between each pair according to any suitable angle of separation. For example, the sequence pattern shown inFIG.11Aincludes two transmit-receive pairs alternating performing transmit-receive events spaced from one another by 180 degrees.

The transmit-receive sequence shown inFIG.11Amay be similar the sequence described with reference toFIG.10. For example, an ultrasound transducer1112(1)may emit an ultrasound pulse1120. The same transducer1112(1)may receive a reflection1130from the structure1150. Then, an ultrasound transducer1112(33)may emit an ultrasound pulse1121. The same transducer1112(33)may receive a reflection1131from the structure1151. The transducer1112(1)may then emit an additional pulse1120and the transducer1112(2)may receive a reflection1130. The transducer1112(33)may then emit an additional pulse1121and the transducer1112(34)may receive a reflection1131and so on. One embodiment of a sequence shown inFIG.11Amay be written as follows:
Tx1Rx1→Tx33Rx33→Tx1Rx2→Tx33Rx34→Tx1Rx3→Tx33Rx35→ . . .

FIG.11Bis a diagrammatic cross-sectional view of the ultrasound imaging assembly illustrating paths of transmitted and received ultrasound pulses, according to aspects of the present disclosure.FIG.11Bmay illustrate three transmit-receive pairs alternating performing transmit-receive events spaced from one another by 120 degrees.

An ultrasound transducer1112(1)may emit an ultrasound pulse1120. The same transducer1112(1)may receive a reflection1130from the structure1150. Then, an ultrasound transducer1112(22)may emit an ultrasound pulse1122. The same transducer1112(22)may receive a reflection1132from a structure1152. Then, an ultrasound transducer1112(43)may emit an ultrasound pulse1123. The same transducer1112(43)may receive a reflection1133from a structure1153. The transducer1112(1)may then emit an additional pulse1120and the transducer1112(2)may receive a reflection1130. The transducer1112(22)may then emit an additional pulse1122and the transducer1112(23)may receive a reflection1131and so on. One embodiment of a sequence shown inFIG.11Bmay be written as follows:
Tx1Rx1→Tx22Rx22→Tx43Rx43→Tx1Rx2→Tx22Rx23→Tx43Rx44→ . . .

FIG.11Cis a diagrammatic cross-sectional view of the ultrasound imaging assembly illustrating paths of transmitted and received ultrasound pulses, according to aspects of the present disclosure.FIG.11Cmay illustrate four transmit-receive pairs alternating performing transmit-receive events spaced from one another by 90 degrees.

An ultrasound transducer1112(1)may emit an ultrasound pulse1120. The same transducer1112(1)may receive a reflection1130from the structure1150. Then, an ultrasound transducer1112(17)may emit an ultrasound pulse1124. The same transducer1112(17)may receive a reflection1134from a structure1154. Then, an ultrasound transducer1112(33)may emit an ultrasound pulse1125. The same transducer1112(33)may receive a reflection1135from a structure1155. Then, an ultrasound transducer1112(49)may emit an ultrasound pulse1126. The same transducer1112(49)may receive a reflection1136from a structure1156. The transducer1112(1)may then emit an additional pulse1120and the transducer1112(2)may receive a reflection1130. The transducer1112(17)may then emit an additional pulse1122and the transducer1112(18)may receive a reflection1134and so on. One embodiment of a sequence shown inFIG.11Cmay be written as follows:
Tx1Rx1→Tx17Rx17→Tx33Rx33→Tx49Rx49→Tx1Rx2→Tx17Rx18→Tx33Rx34→Tx49Rx50→ . . .

FIG.11Dis a diagrammatic cross-sectional view of the ultrasound imaging assembly illustrating paths of transmitted and received ultrasound pulses, according to aspects of the present disclosure.FIG.11Dmay illustrate six transmit-receive pairs alternating performing transmit-receive events spaced from one another by 60 degrees.

An ultrasound transducer1112(1)may emit an ultrasound pulse1120. The same transducer1112(1)may receive a reflection1130from the structure1150. Then, an ultrasound transducer1112(11)may emit an ultrasound pulse1127. The same transducer1112(11)may receive a reflection1137from a structure1157. Then, an ultrasound transducer1112(22)may emit an ultrasound pulse1128. The same transducer1112(22)may receive a reflection1138from a structure1158. Then, an ultrasound transducer1112(33)may emit an ultrasound pulse1129. The same transducer1112(33)may receive a reflection1139from a structure1159. Then, an ultrasound transducer1112(43)may emit an ultrasound pulse1140. The same transducer1112(43)may receive a reflection1141from a structure1160. Then, an ultrasound transducer1112(54)may emit an ultrasound pulse1142. The same transducer1112(54)may receive a reflection1143from a structure1161. The transducer1112(1)may then emit an additional pulse1120and the transducer1112(2)may receive a reflection1130. The transducer1112(11)may then emit an additional pulse1127and the transducer1112(12)may receive a reflection1137and so on. One embodiment of a sequence shown inFIG.11Dmay be written as follows:
Tx1Rx1→Tx11Rx11→Tx22Rx22→Tx33Rx33→Tx43Rx43→Tx54Rx54→Tx1Rx2→Tx11Rx12→Tx22Rx23→Tx33Rx34→Tx43Rx44→Tx54Rx55→ . . .

As shown inFIGS.11A through11D, in some embodiments, the transmit-receive pairs may be spaced from one another symmetrically. For example, the processor circuit510(FIG.5) may be configured to control the circumferentially spaced array to cause the first subset and the second subset of ultrasound transducers to be spaced from one another around the circumferential array.

As previously mentioned, in some embodiments, the processor circuit510(FIG.5) may control the circumferentially spaced array in such a way as to cause more than one transmit-receive pair of ultrasound transducers to perform a transmit-receive event simultaneously. For example, the IVUS imaging device may include multiple communication lines in communication with the circumferential array of acoustic elements and the multiple communication lines may include a first data channel and a second data channel. The multiple ultrasound pulses may include a third ultrasound pulse emitted by a third subset of the circumferential array and a fourth ultrasound pulse emitted by a fourth subset of the circumferential array, wherein the processor circuit is configured to control the circumferential array to emit the first ultrasound pulse and the third ultrasound pulse simultaneously. The first ultrasound pulse is associated with the first data channel and the third ultrasound pulse is associated with the second data channel and the processor circuit is configured to control the circumferential array to emit the second ultrasound pulse and the fourth ultrasound pulse simultaneously. The third ultrasound pulse is associated with the first data channel and the fourth ultrasound pulse is associated with the second data channel.

FIG.12Ais a diagrammatic view of an intraluminal ultrasound image with multiple artifacts caused by high pulse repetition frequency, according to aspects of the present disclosure.FIG.12Aincludes an IVUS image1200showing various structures1220within the imaged anatomy as well as multiple artifacts1201.

The presence of artifacts1201within the IVUS image1200is one example of inaccuracies that may be introduced in the received ultrasound imaging data as a result of reverberation. For example, the methods used to obtain the image1200shown inFIG.12Amay be similar to the methods described with reference toFIG.6. Specifically, when obtaining the ultrasound data corresponding to the image1200, the processor circuit510may have used a sequence of transmitting and receiving ultrasound pulses that included a first transducer emitting a and receiving a pulse and then the same transducer emitting a pulse again instead of alternating transmit-receive events with other different transmit-receive pairs. In addition, a high pulse repetition frequency may have been used to obtain the ultrasound image data corresponding to the IVUS image1200. As a result, the likelihood of one receiving transducer of receiving reverberation, or unwanted, leftover acoustic energy from a previous ultrasound pulse is higher. Without using multiple transmit-receive pairs of transducers in alternation, the receiving transducers are both spaced closely to one another, and are within one another's field of view or line of sight and, with a high PM, there is not sufficient time for previous ultrasound pulses to attenuate or die out in time for the next ultrasound pulse to be received.

FIG.12Bis a diagrammatic view of an intraluminal ultrasound image obtained using a reverberation signal reduction sequence, according to aspects of the present disclosure.FIG.12Aincludes an IVUS image1250showing the same structures1220within the imaged anatomy but does not include any artifacts1201from reverberation.

The IVUS image1250may have been obtained according to the methods of alternating transmit-receive pairs as described inFIGS.10, and11A through11D. By alternating transmit-receive pairs, after one transducer emits an ultrasound pulse and a corresponding transducer receives it, the pulse has more time to attenuate and die out as a different transmit-receive pair of transducers performs a transmit-receive event. In this way, when the original transmit-receive pair emits and receives another ultrasound pulse, there are no left over reverberations from the previous pulse.

FIG.13Ais a diagrammatic view of an intraluminal ultrasound image with artifacts caused by high pulse repetition frequency, according to aspects of the present disclosure. Pulse repetition frequency (PRF) may be inversely related to the pulse repetition interval. As PM decreases, PRF increases and vice versa.FIG.13Awill be described in conjunction with bothFIG.13BandFIG.13C.FIG.13Bis a diagrammatic view of an intraluminal ultrasound image obtained using a reverberation signal reduction sequence, according to aspects of the present disclosure.FIG.13Cis a diagrammatic view of an intraluminal ultrasound image obtained using a reverberation signal reduction sequence, according to aspects of the present disclosure.

In some embodiments, the PRI and spacing between transmit-receive pairs of transducers may be adjusted to provide the clearest image. For example, as the PM for a particular imaging procedure is decreased, the likelihood of reverberation artifacts increases. This is because as the time between ultrasound pulses decreases, there is less time for ultrasound pulses to attenuate before the next pulse is emitted. In addition, as the number of alternating transmit-receive pairs are increased, the likelihood of reverberation artifacts may increase or decrease. For example, if the number of transmit-receive pairs is increased from one to two spaced apart by a 180 degree separation, the likelihood of reverberation artifacts may decrease. This is because, as previously described, there is more time for a pulse from a transmit-receive pair of transducers to attenuate before the same pair is directed to emit another pulse. Similarly, if the number of transmit-receive pairs is increased from one to three spaced by a 120 degree separation, the likelihood of reverberation artifacts may decrease for the same reason. In this case, more time passes after one particular transmit-receive pair emits a pulse before it is directed to emit another pulse. As the number of transmit-receive pairs is continually increased, however, the likelihood of reverberation artifacts may increase if the separation between transmit-receive pairs becomes small enough that the radiation patterns of adjacent transmit-receive pairs begin to overlap. As a result, a user of the system100may adjust the number of alternating transmit-receive pairs and the PRI for a particular imaging procedure to minimize the likelihood of reverberation artifacts.

In some embodiments, referring again toFIG.11D, the processor circuit510may alter the sequence of emitted pulses from different transmit-receive pairs of transducers to further decrease the likelihood of reverberation artifacts. For example, the processor circuit510may cause the transducers to emit pulses according to a “star” pattern, such that if there are five or more alternating transmit-receive pair of transducers used, after a transmit-receive pair emits a pulse, a pair furthest from that emitting pair will emit a pulse next. In this way, if the spacing between pairs inFIG.11Dis 60 degrees for example, transmit-receive pairs positioned 60 degrees apart next to each other will not emit pulses sequentially. As an exemplary sequence, the processor circuit may direct1112(1)to emit a pulse, then transducer1112(43), then transducer1112(11), then transducer1112(54), then transducer1112(22), then transducer1112(1), then transducer1112(33), then transducer1112(11), and so on. Various other sequences may also be used. By emitting pulses in such a way that neighboring transmit-receive pairs do not emit pulses consecutively, both the benefit of an increased number of transmit-receive pairs (i.e., more time between pulse emissions, or increased effective PM) and the benefit of a decreased number of transmit-receive pairs (i.e., larger effective spacing between transmit-receive pairs) may be realized. This may lead to a decreased likelihood of reverberation artifacts in the resulting IVUS image.

Turning toFIG.13A, an IVUS image1300is presented.FIG.13Adepicts a structure1055. The structure1055may be a vessel wall or some other structure within the surrounding anatomy.FIG.13Aalso depicts a reverberation artifact1010and a reverberation artifact1020. The reverberation artifacts1010and1020may be caused by a low PM or by too small of spacing between consecutively emitting transmit-receive pairs of transducers.

FIG.13Bshows an IVUS image1302. The IVUS image1302depicts the same structure1055. However, the image1302includes two less pronounced reverberation artifacts, namely artifact1015and artifact1025. The IVUS image1302may be the result of altering parameters associated with the ultrasound data acquisition. For example, the image1302may have been obtained while increasing the PRI. Alternatively, the image1302may have been obtained while increasing the spacing between consecutively emitting transmit-receive pairs of transducers. Either of these adjustments may have the effect of decreasing the presence of reverberation artifacts in the resulting IVUS image.

Turning now toFIG.13C, an IVUS image1304is presented.FIG.13Cdepicts the same structure1055but does not exhibit any reverberation artifacts. This may be a result of further adjustments to the PRI or spacing of emitting transmit-receive pairs of transducers as has been explained.

FIG.14is a flow diagram for a method1400for reducing reverberation signals in intravascular ultrasound imaging, according to aspects of the present disclosure. As illustrated, the method1400includes a number of enumerated steps, but embodiments of the method1400may include additional steps before, after, or in between the enumerated steps. In some embodiments, one or more of the enumerated steps may be omitted, performed in a different order, or performed concurrently. The steps of the method1400can be carried out by any suitable component within the system100and all steps need not be carried out by the same component. In some embodiments, one or more steps of the methods1400can be performed by, or at the direction of, a processor circuit of the system100(e.g., the processor circuit510ofFIG.5), including, e.g., the processor560or any other component.

At step1410, the method1400includes controlling the circumferential array to emit a plurality of ultrasound pulses. The plurality of ultrasound pulses includes a first ultrasound pulse and a second ultrasound pulse. Step1410includes controlling a first subset of the circumferential array to emit the first ultrasound pulse and controlling a second subset of circumferential array to emit the second ultrasound pulse immediately after the first ultrasound pulse. The second subset of the circumferential array is circumferentially spaced from the first subset of the circumferential array. For example, step1410can include controlling the circumferential array to obtain IVUS imaging data. The IVUS imaging data is representative of a first transmit-receive aperture. The first transmit-receive aperture may include a first combined radiation pattern and may be associated with at least one first acoustic element of the circumferential array. IVUS imaging data may also be representative of a second transmit-receive aperture. The second transmit-receive aperture may include a second combined radiation pattern and may be associated with at least one second acoustic element of the circumferential array. The IVUS imaging data representative of the second transmit-receive aperture is obtained immediately after the IVUS imaging data representative of the first transmit-receive aperture. The at least one first acoustic element and the at least one second acoustic element are circumferentially spaced from one another around the circumferential array such that the first combined radiation pattern and the second combined radiation pattern are non-overlapping or minimally overlapping.

At step1420, the method1400includes generating an IVUS image based on the plurality of ultrasound pulses. For example, step1420can include generating an IVUS image based on the IVUS imaging data.

At step1430, the method1400includes outputting the IVUS image to a display in communication with the processor circuit. For example, step1430can include outputting the IVUS image to a display in communication with the processor circuit.

Persons skilled in the art will recognize that the apparatus, systems, and methods described above can be modified in various ways. Accordingly, persons of ordinary skill in the art will appreciate that the embodiments encompassed by the present disclosure are not limited to the particular exemplary embodiments described above. In that regard, although illustrative embodiments have been shown and described, a wide range of modification, change, and substitution is contemplated in the foregoing disclosure. It is understood that such variations may be made to the foregoing without departing from the scope of the present disclosure. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the present disclosure.