Intravascular ultrasound (IVUS) plane wave imaging

Abstract

An intravascular ultrasound (IVUS) catheter includes a flexible elongate member position-able within a blood vessel of a patient and a circumferential array of acoustic elements. Each acoustic element of the circumferential array is configured to transmit ultrasound energy and receive echoes associated with the transmitted ultrasound energy. Processor(s) communicate with the circumferential array. The processor(s) control a first aperture of the circumferential array to transmit a first ultrasound plane wave. The first aperture includes a first plurality of acoustic elements forming a first circumferential portion of the circumferential array. The processor(s) control the first aperture to receive echoes corresponding to the first ultrasound plane wave. The processor(s) generate a circumferential ultrasound image based on the echoes corresponding to the first ultrasound plane wave. The processor(s) output the circumferential ultrasound image to a display in communication with the processor.

Description

INTRAVASCULAR ULTRASOUND (IVUS) PLANE WAVE IMAGINGTECHNICAL FIELD

[0001] The present disclosure relates generally to intravascular ultrasound (IVUS) imaging using a catheter positioned inside of a blood vessel. In particular, phase dispersion can be used to use to generate plane wave for IVUS imaging.BACKGROUND

[0002] 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 or reflections to produce a cross-sectional image of the vessel where the device is placed.

[0003] Phased array (also known as digital or synthetic-aperture) IVUS catheters are one of the two types of IVUS devices commonly used today, the other type being the rotational IVUS catheter. Phased array 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 acoustic elements or imaging 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 element groups, the phased array IVUS system can synthesize the effect of a mechanically scanned ultrasound transducer but without moving parts.

[0004] Often, phased array IVUS imaging involves a single transmit and receive pair for each firing. For example, an ultrasound pulse or wave is emitted from element 1 and then received on element 1 ; subsequently another ultrasound pulse or wave is emitted from element 1and then received on element 2, and so on in order to build up an aperture. Therefore, time is needed to generate an IVUS aperture.

[0005] The information included in this Background section of the specification, including any references cited herein and any description or discussion thereof, is included for technical reference purposes only and is not to be regarded as subject matter by which the scope of the disclosure is to be bound.SUMMARY

[0006] Signal processing optimization techniques are desired to increase frame rates and produce better image resolution in IVUS imaging systems. An aperture for an IVUS imaging system has a natural tendency to focus on a particular point in space, which prevents the creation of a plane wave. However, using phase dispersion, an IVUS imaging system may counteract the aperture’s natural tendency to focus on a focal region, which generates a plane wave. An IVUS plane wave imaging system generates plane waves (1) without needing to change a steering angle during imaging, and (2) without needing to spatially compound the data. Generating a plane wave may be accomplished by transmitting on, e.g., a select group of transducer elements of the array. In some examples, transmitting a plane wave using all transducer elements of the array may also be used to determine the location of the IVUS catheter within in the vessel to determine if the IVUS catheter is centered within the vessel.

[0007] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter. A more extensive presentation of features, details, utilities, and advantages of the IVUS imaging system, as defined in the claims, is provided in the following written description of various instances of the disclosure and illustrated in the accompanying drawingsBRIEF DESCRIPTION OF THE DRAWINGS

[0008] Illustrative instances of the present disclosure will be described with reference to the accompanying drawings, of which:

[0009] Figure 1 is a schematic diagram of an intraluminal imaging system, according to aspects of the present disclosure.

[0010] Figure 2 is a schematic diagram of a processor circuit, according to instances of the present disclosure.

[0011] Figure 3 is a schematic, diagrammatic representation of the operation of an ultrasound transducer element, according to aspects of the present disclosure.

[0012] Figure 4A is a cross-sectional representation of an IVUS catheter transmitting an ultrasonic plane wave using a first aperture, according to aspects of the present disclosure.

[0013] Figure 4B is a cross-sectional representation of an IVUS catheter transmitting an ultrasonic plane wave using a second aperture, according to aspects of the present disclosure.

[0014] Figure 5 is a diagrammatic representation of transmitting ultrasonic wave signals using phase dispersion to generate plane waves, according to aspects of the present disclosure.

[0015] Figure 6 is a diagrammatic representation of transmitting ultrasonic wave signals using no phase dispersion to generate plane waves, according to aspects of the present disclosure.

[0016] Figure 7 is a schematic, diagrammatic representation, in block diagram form, of an example ultrasound transmit process, according to aspects of the present disclosure.

[0017] Figure 8 is a schematic, diagrammatic representation, in block diagram form, of an example ultrasound receive process, according to aspects of the present disclosure.

[0018] Figure 9 is a flowchart method for performing a portion of a plane wave pulse sequence, according to aspects of the present disclosure.

[0019] Figure 10 is another flowchart method for performing a portion of a plane wave pulse sequence, according to aspects of the present disclosure.

[0020] Figure 11 is a cross-sectional representation of an IVUS catheter transmitting ultrasonic plane waves, according to aspects of the present disclosure.

[0021] Figure 12A is a cross-sectional representation of an IVUS catheter transmitting ultrasonic plane waves, according to aspects of the present disclosure.

[0022] Figure 12B is a cross-sectional representation of an IVUS catheter receiving echo signals from the ultrasonic plane waves of Figure 12A, according to aspects of the present disclosure.

[0023] Figure 13A is another cross-sectional representation of an IVUS catheter transmitting ultrasonic plane waves, according to aspects of the present disclosure.

[0024] Figure 13B is another cross-sectional representation of an IVUS catheter receiving ultrasonic plane waves, according to aspects of the present disclosure.DETAILED DESCRIPTION

[0025] For the purposes of promoting an understanding of the principles of the present disclosure, reference will now be made to the aspects 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. In particular, it is fully contemplated that the features, components, and / or steps described with respect to one aspect may be combined with the features, components, and / or steps described with respect to other aspects of the present disclosure. Further, while the aspects of the present disclosure may be described with respect to a blood vessel, it will be understood that the devices, systems, and methods described herein may be configured for use in any suitable anatomical structure or body lumen including a blood vessel, blood vessel lumen, an esophagus, eustachian tube, urethra, fallopian tube, intestine, colon, and / or any other suitable anatomical structure or body lumen. In other aspects, the devices, systems, and methods described herein may 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 vessels, chambers or other parts of the heart, and / or other systems of the body. In addition to natural structures, the intraluminal devices, described herein, may be used to examine man-made structures such as, but without limitation, heart valves, stents, shunts, filters, and other devices. For the sake of brevity, however, the numerous iterations of these combinations will not be described separately.

[0026] The example aspects described below recognize that it may be desirable to have methods and apparatuses for ultrasonic imaging using a circumferential array such as an IVUS catheter. One benefit of using an IVUS catheter to create plane waves is that an IVUS catheter does not need to change a steering angle during imaging, nor does it need to spatially compound the data to create enough signal to noise to produce a desired ultrasound image. For example, each transducer element of an IVUS circumferential array is steered an suitable number ofdegrees differently, as a feature of being a circumferential array, which replaces the need for changing the steering angle. In some instances, the steering angle can be changed as part of plane wave imaging compounding

[0027] One or more aspects described below provide methods and apparatuses related to using phase dispersion to generate a plane wave image. For example, an aperture has a natural tendency to focus on a particular region in space. However, phase dispersion allows for parallel acoustic information in the tissue to be acquired using a plane wave.

[0028] One or more illustrative aspects described below provide transmitting a plane wave using all transducer elements of the array in order to produce higher acoustic pressure. In some examples, transmitting a plane wave using all transducer elements of the array may also be used to determine the location of the IVUS catheter within in the vessel to determine if the IVUS catheter is centered within the vessel.

[0029] One or more example aspects described below provide two or more conductors that are signal lines. In existing devices, catheters may have multiple conductors. For example, a catheter may include a high voltage conductor for powering the transducer array, one or two carry control signals, an electrical ground, etc.

[0030] Figure 1 is a schematic diagram of an intraluminal imaging system 100, according to aspects of the present disclosure. The intraluminal imaging system 100 can be an ultrasound imaging system. In some instances, the system 100 can be an intravascular ultrasound (IVUS) imaging system. The system 100 may include an intraluminal imaging device 102 (such as a catheter, guide wire, or guide catheter), a patient interface module (PIM) 104, a processing system or console 106, and a monitor 108. The intraluminal imaging device 102 can be an ultrasound imaging device. In some instances, the device 102 can be an IVUS imaging device, such as a solid-state IVUS device.

[0031] At a high level, the IVUS device 102 emits ultrasonic energy from a transducer array 124 included in scanner assembly 110, also referred to as an IVUS imaging assembly, mounted near a distal end of the flexible elongate member 121 (e.g., the body of the catheter). The ultrasonic energy is reflected by tissue structures in the surrounding medium, such as a vessel 120, or another body lumen surrounding the scanner assembly 110, and the ultrasound echoes are received by the transducer array 124. In that regard, the device 102 can be sized, shaped, or otherwise configured to be positioned within the body lumen of a patient. The transducer array124 generates electrical signals representative of the received ultrasound echoes and transmits these echo signals to the PIM 104. The PIM 104 transfers the received echo signals to the console or computer 106, where the ultrasound image (including flow information in some instances) is reconstructed and displayed on the monitor 108. The console or computer 106 can include a processor and a memory. The intraluminal imaging device 102, PIM 104, and / or computer or computing device 106 can be operable to facilitate the features of the intraluminal imaging system 100 described herein. For example, the processor can execute computer readable instructions stored on the non-transitory tangible computer readable medium.

[0032] The transducer array 124 can be stationary or fixed relative to the flexible elongate member. The transducer array 124 can be a circumferential array with any suitable number of ultrasound transducer elements. For example, the transducer array 124 can include between 10 and 1000 ultrasound transducer elements, between 50 and 100 ultrasound transducer elements, between 100 and 150 ultrasound transducer elements, including values, such as 30, 32, 60, 64, 75, 100, 120, 128, 150 ultrasound transducer elements, and / or other values both larger and smaller.

[0033] The PIM 104 facilitates communication of signals between the IVUS console 106 and the scanner assembly 110 included in the IVUS device 102. This communication includes the steps of: (1) providing commands to integrated circuit controller chip(s) 130 (e.g., application specific integrated circuits or ASICs) included in the scanner assembly 110 to 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) 130 to 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) 130. In some instances, the PIM 104 performs preliminary processing of the echo data prior to relaying the data to the console 106. In examples of such instances, the PIM 104 performs amplification, filtering, and / or aggregating of the data. In an instance, the PIM 104 also supplies high- and low- voltage DC power to support operation of the device 102 including circuitry within the scanner assembly 110.

[0034] The IVUS console 106 receives the echo data from the scanner assembly 110 by way of the PIM 104 and processes the data to reconstruct an image of the tissue structures in themedium surrounding the scanner assembly 110. The console 106 outputs image data such that an image of the vessel 120, such as a cross-sectional image of the vessel 120, is displayed on the monitor 108. The vessel 120 may represent fluid filled or surrounded structures, both natural and man-made. The vessel 120 may be within a body of a patient. The vessel 120 may 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 device 102 may 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 device 102 may be used to examine man-made structures such as, but without limitation, heart valves, stents, shunts, filters and other devices.

[0035] In some instances, 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. Patent No. 7,846,101 hereby incorporated by reference in its entirety. For example, the IVUS device 102 includes the scanner assembly 110 at or near a distal end of the flexible elongate member 121 and a transmission line bundle 112 extending longitudinally within and along flexible elongate member 121.

[0036] The transmission line bundle 112 terminates in a PIM connector 114 at a proximal end of the device 102. The PIM connector 114 electrically couples the transmission line bundle 112 to the PIM 104 and physically couples the IVUS device 102 to the PIM 104. In an instance, the IVUS device 102 further includes a guide wire exit port 116. Accordingly, in some instances the IVUS device is a rapid-exchange catheter. The guide wire exit port 116 allows a guide wire 118 to be inserted towards the distal end in order to direct the device 102 through the vessel 120.

[0037] In some instances, blood flow velocity determination algorithms such as Philips ChromaFlo, power Doppler, and / or color flow (Doppler) can be used. Examples of ChromaFlo imaging from apertures of a digital IVUS device for flow imaging can be found for example in U.S. Patent Application No. 17 / 872,203, filed 25 July 2022, as well as U.S. Patent Application No. 17 / 282,659, filed 02 April 2021 (Atty. Docket No. 2017PF02496WOUS / 44755.1859US01).

[0038] Figure 2 is a schematic diagram of a processor circuit 550, according to instances of the present disclosure. The processor circuit 550 may be implemented in the intraluminal imaging system 100, or other devices or workstations (e.g., third-party workstations, network routers, etc.), or on a cloud processor or other remote processing unit, as necessary to implement the method. As shown, the processor circuit 550 may include a processor 560, a memory 564, and a communication module 568. These elements may be in direct or indirect communication with each other, for example via one or more buses.

[0039] The processor 560 may include a central processing unit (CPU), a digital signal processor (DSP), an ASIC, a controller, or any combination of general-purpose computing devices, reduced instruction set computing (RISC) devices, application-specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or other related logic devices, including mechanical and quantum computers. The processor 560 may also comprise another hardware device, a firmware device, or any combination thereof configured to perform the operations described herein. The processor 560 may 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.

[0040] The memory 564 may include a cache memory (e.g., a cache memory of the processor 560), 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 instance, the memory 564 includes a non-transitory computer-readable medium. The memory 564 may store instructions 566. The instructions 566 may include instructions that, when executed by the processor 560, cause the processor 560 to perform the operations described herein. Instructions 566 may 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.

[0041] The communication module 568 can include any electronic circuitry and / or logic circuitry to facilitate direct or indirect communication of data between the processor circuit 550, and other processors or devices. In that regard, the communication module 568 can be an input / output (I / O) device. In some instances, the communication module 568 facilitates direct or indirect communication between various elements of the processor circuit 550 and / or the intraluminal imaging system 100. The communication module 568 may communicate within the processor circuit 550 through numerous methods or protocols. Serial communication protocols may include but are not limited to United States Serial Protocol Interface (US SPI), Inter- Integrated Circuit (I2C), Recommended Standard 232 (RS-232), RS-485, Controller Area Network (CAN), Ethernet, Aeronautical Radio, Incorporated 429 (ARINC 429), MODBUS, Military Standard 1553 (MIL-STD-1553), or any other suitable method or protocol. Parallel protocols include but are not limited to Industry Standard Architecture (ISA), Advanced Technology Attachment (ATA), Small Computer System Interface (SCSI), Peripheral Component Interconnect (PCI), Institute of Electrical and Electronics Engineers 488 (IEEE-488), IEEE- 1284, and other suitable protocols. Where appropriate, serial and parallel communications may be bridged by a Universal Asynchronous Receiver Transmitter (UART), Universal Synchronous Receiver Transmitter (USART), or other appropriate subsystem.

[0042] External communication (including but not limited to software updates, firmware updates, preset sharing between the processor and central server, or readings from the annular ultrasound imaging array) may be accomplished using any suitable wireless or wired communication technology, such as a cable interface such as a universal serial bus (USB), micro USB, Lightning, or FireWire interface, Bluetooth, Wi-Fi, ZigBee, Li-Fi, or cellular data connections such as 2G / GSM (global system for mobiles) , 3G / UMTS (universal mobile telecommunications system), 4G, long term evolution (LTE), WiMax, or 5G. For example, a Bluetooth Low Energy (BLE) radio can be used to establish connectivity with a cloud service, for transmission of data, and for receipt of software patches. The controller may be configured to communicate with a remote server, or a local device such as a laptop, tablet, or handheld device, or may include a display capable of showing status variables and other information. Information may also be transferred on physical media such as a USB flash drive or memory stick.

[0043] Figure 3 is a schematic, diagrammatic representation of the operation of an ultrasound transducer element 610, according to aspects of the present disclosure. In the example shown in Figure 3, the ultrasound transducer 610 receives a transmit trigger signal 620, such as a series of electrical pulses. In response, the transducer (which may for example be piezoelectric) changes size in response to the pulses of the transmit trigger signal 620, and thus emits pulses or waves of ultrasound imaging energy 630. When the emitted ultrasound energy 630 strikes a stationary or moving target 640, it generates reflected ultrasound echoes 650 with roughly the same frequency and bandwidth as the emitted ultrasound energy. If the target 640 is moving away from the transducer 610, then the Doppler effect will decrease the frequency and bandwidth of the ultrasound echoes 650 as a function of that velocity. Similarly, if the target 640 is moving toward the transducer 610, then the Doppler effect will increase the frequency and bandwidth of the ultrasound echoes 650 as a function of the velocity.

[0044] Figure 4A is a cross-sectional representation of an IVUS catheter 102 transmitting ultrasound pulses forming planar or plane wave 660, according to aspects of the present disclosure. The plane wave 660 includes wavefronts 662 that propagate from the IVUS catheter 102 towards the vessel wall 120 as time progresses. Visible are the ultrasound transducer elements 212 of the transducer array 124 surrounding the flexible elongate member 121. In the example shown in Figure 4A, the pulse 630 is transmitted by a first aperture 668. Each aperture (e.g., first aperture 668) can be a subset (e.g., n transducer elements) of the transducer array 124 (e.g., m transducer elements), in which the subset includes fewer transducer elements than the total number of the transducer elements in the transducer array 124 (e.g., n < tri).

[0045] Figure 4B is a cross-sectional representation of an IVUS catheter 102 transmitting ultrasound pulses forming planar or plane wave 670, according to aspects of the present disclosure. The plane wave 670 include wavefronts 672 that propagate from the IVUS catheter 102 towards the vessel wall 120 as time progresses. In the example shown in Figure 4B, the pulse 630 is transmitted by a different, second aperture 678. The second aperture 678 is different than the first aperture 668 (Fig. 4A) because the second aperture 678 is a different subset of ultrasound transducer elements of the transducer array 124. For example, the second aperture 678 can be shifted by any suitable number of ultrasound transducer elements relative to the first aperture 668. Because the second aperture 678 is different than the first aperture 668, the plane wave 670 propagates in a different direction / angle than the plane wave 660. In that regard, thesecond aperture 678 can be described as shifted by any suitable angle relative to the first aperture 668.

[0046] Depending on the implementation, apertures (e.g., the first aperture 668, the second aperture 678) may include a single transducer 212, a plurality of transducers, or as many as all 64 transducers. There can a performance tradeoff in which smaller apertures allow slower, higher- resolution imaging, while larger apertures allow faster, lower-resolution imaging. In one or more instances, the first aperture 668 represents a first plurality of transducer elements 212 forming a first circumferential portion of the circumferential array 124, and the second aperture 678 represents a second plurality of transducer elements 212 forming a second circumferential portion of the circumferential array 124. In some cases, the aperture size is fixed, and in other cases it may be varied dynamically (e.g., alternated between a smaller and a larger aperture such as the first aperture 668 may be smaller in size than the second aperture 678).

[0047] Figure 5 is diagrammatic representation of a system 800 for using phase dispersion to generate a plane wave 660 with a circumferential transducer array. Figure 5 can illustrate portions of the intravascular imaging system 100 (Fig. 1), such as the IVUS catheter 102 and / or the IVUS catheter 102 depicted in Figures 4A and 4B. For example, only a portion of the ultrasound transducer elements 212 forming the circumferential transducer array 124 is shown in Figure 5.

[0048] The system 800 includes a transmit beamformer ASIC 802. The transmit beamformer ASIC 802 can be part of the IVUS catheter 102, the PIM 104, and / or the processing system 106 (Fig. 1). The transmit beamformer ASIC 802 is configured to transmit a plurality of transmit signals using pulsers 804, which can be part of the scanner assembly 110 (Fig. 1). A plurality of signal lines 806 couples each pulser 804 to each individual transducer element 212. The plurality of signal lines 806 are operationally coupled to respective transducer elements 212, as shown in Figure 5. The pulsers 804 includes pulser 804a transmitting a first transmit signal and pulser 804b transmitting a second transmit signal. The first transmit signal of pulser 804a is sent at a different point in time from the second transmit signal of pulser 804b. The difference At between the second transmit signal from pulser 804b and the first transmit signal from the pulser of 804a is represented by 808.

[0049] In operation, the transmit beamformer ASIC 802 sends a plurality of transmit signals, using pulsers 804, along a plurality of signal lines 806. For example, the transmit signals aretransmited to an aperture of the array 124, indicated by subset of ultrasound transducer elements 212 that are shaded. The transmit beamformer ASIC 802 causes phase dispersion by sending the plurality of transmit signals at varying times using time delays. For example, the first transmit signal of pulser 804a is delayed and sent after the second transmit signal of pulser 804b and is separated by the At 808. The time delay allows for the generation of the plane wave 660. The plurality of transmit signals sent by the transmit beamformer ASIC 802 produces plane wave 660 with the wavefronts 662. The acoustic dispersion counteracts an aperture’s tendency to focus at a particular depth (such as a focal region), as shown in Figure 6.

[0050] Figure 6 is a diagrammatic representation for transmiting ultrasonic energy using no phase dispersion. The pulsers 804 includes pulser 804a that transmits a first transmit signal and pulser 804b that transmits a second transmit signal. The first transmit signal of pulser 804a is sent at a same point in time from the second transmit signal of pulser 804b. The plurality of transmit signals causes an aperture of the transducer array 124 to produce an acoustic wave or beam patern 812 with the wavefronts 818. The acoustic wave 812 focuses at focal region 820 as result of the focus of the aperture.

[0051] Figure 7 is a schematic, diagrammatic representation of an example ultrasound transmit process 822, according to aspects of the present disclosure. Figure 7 may illustrate portions of an intraluminal imaging system 100 of Figure 1, such as the IVUS catheter 102, PIM 104, and / or the processing system 106. In the example shown in Figure 7, a computer, console, or processing system 106, which includes a processor circuit 510 (e.g., a central processing unit (CPU), graphic processing unit (GPU), or otherwise), receives user input 824. The user input 824, for example, can initiate the ultrasound transmit process 822 and / or the recording the ultrasound images generated using the transmit process 822. The computer 106 processes the user input 824 and generates a control signal 826. This control signal 826 is passed to the patient interface module or patient interface monitor (“PIM”) 104, which includes a processor circuit 510 (e.g., a field programmable gate array (FPGA) that communicates with the IVUS catheter 102), a sequencer 828 (which controls the transducer array 124), and a transmit trigger signal generator 830. The transmit trigger signal generator 830 generates a trigger signal 832 (e.g., a series of pulses or waves) for each active transducer element 212 of the transducer array of the transmit aperture 834. The trigger signals 832 are conveyed to the IVUS catheter 102 based on a timing sequence 836 determined by the sequencer 828. The IVUS catheter 102 includes aprocessor circuit, such as one or more ASICs 840. The one or more ASICs may include one or more multiplexers 842 and one or more transmit pulsers 844. The one or more ASICs are coupled to the transducer array 124. The transducer array 124 includes a transmit aperture 834, which is a subset of ultrasound transducer elements of the transducer array 124.

[0052] In some aspects, the processor circuit 510 controls the IVUS catheter 102. For example, the processor circuit 510 programs the one or more ASICs 840 to cause the transducer array 124 transmit an ultrasound plane wave.

[0053] In one example, all elements of the transmit aperture 834 transmit simultaneously. In another example, there is symmetric transmit by the transmit aperture 834, where two elements of a given aperture transmit at the same time, while other 2 element groups transmit and the same time but delayed from the first group. In another example, there is a steered divergent wave, in which all elements of the transmit aperture 834 are delayed independently.

[0054] In one or more aspects, the sequencer 828 programs the timing and the sequence of activations at the transducer elements 212 (e.g., for emitting ultrasound waves) of the transmit aperture 834 and the transmit trigger signal generator 830 generates trigger signals to activate the transducer elements 212 of the transmit aperture 834. In one or more aspects, the outputs of the sequencer 828 and the transmit trigger signal generator 830 are based on a detected device attribute or ultrasound attribute of the IVUS catheter 102.

[0055] In some instances, the transducers of the transducer array 124 may be grouped into transmit apertures 834, such as the first aperture 668 of Figure 4A. In some instances, the transducer array 124 may comprise multiple apertures (e.g., the first aperture 668 and the second aperture 678 in Figure 4A and 4B). Each transmit aperture 834 may include a subset of transducer elements less than the total number of transducer elements of the transducer array 124. In some instances, the first transmit aperture such as the first aperture 668 of Figure 4A includes a plurality of transducer elements 212 that form a first circumferential portion of the circumferential array 124, and the second transmit aperture such as the second aperture 678 of Figure 4B includes a plurality of transducer elements 212 that form a second circumferential portion of the circumferential array 124. The first circumferential portion is different than the second circumferential portion. In some instances, a third, fourth, or more transmit apertures include a plurality of transducer elements 212 that form additional different circumferential portions of the circumferential array 124 that are different from one another and different fromthe first circumferential portion and the second circumferential portion. In yet other instances, the transmit aperture 834 includes every element of the 64-element array. In some aspects, different transmit apertures have the same number of transducer elements or vary in the number of transducer elements.

[0056] The sequencer 828 may activate one or more transducer elements in the transmit aperture 834 to emit ultrasound waves 630 (e.g., ultrasound transmit pulses). The ultrasound waves 630 may be emitted towards a target anatomical structure 640 (Fig. 3), such as a blood vessel. The IVUS catheter 102 can include receive switching circuitries coupled to the transducer so that the sequencer 828 may also activate one or more transducers in the transmit aperture 834 to receive echo signals 650 reflected back from the target 640. The received echo signals 650 may create an A-line representing the target 640 (Fig. 3).

[0057] In some aspects, the phase dispersion described in Figure 5 is created by the sequencer 828 of the processing circuit 510 controlling the timing sequence 836 on the transmit trigger signals 832 to delay the start time of one or more transducer elements 212 of the transmit aperture 834. In one or more aspects, the timing sequence 836 is sent to the one or more ASICs 840 and the transmit pulsers 844 transits a wave pulse using the timing sequence 836.

[0058] The one or more ASICs of the IVUS catheter 102 can include transmit beamformer circuitry with transmit delays 850 (e.g., delays 808 of Fig. 5). The transmit delays 850 can be used as part of the timing to provide phase dispersion in order to generate plane waves. In some aspects, the transmit delays 850 can be provided for beam steering. For example, as part of the divergent beam creation, there can be some beam steering involved. In other instances, the transmit beamformer circuitry may not be in the catheter 102, and instead implemented in the PIM 104 and / or the computer 106.

[0059] In some aspects, the transmit pulsers 844 are not in the one or more ASICs 840 of the catheter 102. In such instances, the transmit pulsers 844 can be provided in the processor circuit 510 (e.g., FPGA) of the PIM 104.

[0060] In some instances, some transducers of the transducer array 124 may be coupled to the same transmit switching circuitry. In addition, in some instances, the sequencer 828 may be coupled to the trigger signal generator 830 and the trigger signal generator 830 can apply encoded trigger signals to the IVUS catheter 102. The encoded trigger signals can furtherinclude information indicating the transducers and or transmit aperture 834 selected by the sequencer 828.

[0061] In some instances, the one or more multiplexers 842 may include a plurality of transmit switching circuitries. Each transmit switching circuitry may be coupled to one of the transducer elements 212. Each transmit switching circuitry may include a driver that can activate ultrasound wave emissions at transducers 212 and a switch that can gate or allow an electrical signal (e.g., a trigger signal 832) to pass through to a corresponding transducer 212. In some instances, the switch can be used in a configuration with fewer transmit drivers to drive a greater number of transmit elements. The transmit switching circuitries in the one or more multiplexers 842 may receive trigger signals 832 the transmit trigger signal generator 830 and send the transmit trigger signals 832 through to the transducer array 124 according to the timing and sequence provided by the sequencer 828. For example, the sequencer 828 may provide a timing sequence 836 indicating a sequence (e.g., including an order and timing) for firing a plurality of transducers of the transducer array 124 such as within a transmit aperture 834.

[0062]

[0063] Figure 8 is a schematic, diagrammatic representation, in block diagram form, of an example ultrasound receive process 852, according to aspects of the present disclosure. Figure 8 may illustrate portions of an intraluminal imaging system 100 of Figure 1, such as the IVUS catheter 102, PIM 104, and / or the processing system 106.

[0064] The transducer array 124 includes receive aperture 854. The receive aperture 854 can be a subset of the transducer elements of transducer array 124, e.g., with fewer transducer elements than the total number of transducer elements in the array 124. In some instances, the receive 854 can be considered to have include a plurality of receive sub-apertures, such as receive sub-aperture 854a and receive sub-aperture 844b, which are themselves subsets of transducer elements of the receive aperture 854 (one or a plurality of ultrasound transducer elements). Additional receive sub-apertures can be included in the receive aperture 854. In some aspects, the receive sub-aperture 854a is the same size as the receive sub-aperture 854b. The transmit aperture 834, the receive aperture 854, and / or the receive sub-apertures 854a, 854b can be the same or different number of ultrasound transducer elements.

[0065] The processor circuit 510 can control the receive aperture 854 to receive echoes corresponding to the transmitted ultrasound plane wave (Fig. 7). The receive aperture 854receives ultrasound echoes, generates electrical signals representative of the echoes, and provides the echo signals to the one or more ASICs 840. The receive aperture 854 can include one or more elements from the transmit aperture 834 or one or more elements of the receive aperture 854 can be completely different than the elements of the transmit aperture 834. The received echo signals are transmitted from the IVUS catheter 102 to the PIM 104. The PIM 104 may include a processor circuit 510, which may or may not conduct some signal processing of the received echo signals. The PIM 104 can transmit the received echo signals to the computer 106 for processing. The computer 106 processes the received echo signals to construct an IVUS image 858. The IVUS image 858 is output from the computer 106 to be displayed on the display 108.

[0066] In some aspects, spatial compounding is not used. In other instances, spatial compounding could be used. This depends on the manner in which the computer generates the images 858. For example, a plane wave transmit beam can be generated and a number of receive elements can be beamformed. In another example, a plane wave transmit beam can be generated and the echo signals for x number of receive elements can be transmitted to the computer 106. In the latter case, compounding can be in the computer 106, there is no need to transmit separate beam angles to build up resolution laterally.

[0067] Generally, the ultrasound transmit process 822 (Fig. 7) occurs prior to the ultrasound receive process 855 (Fig. 8). For example, one or more processors such as processing circuit 510 is configured to activate each acoustic element of the transmit aperture 834 before the one or more processors are configured to control any of the transducer elements 212 of the receive aperture 85 are activated to perform receive. In some instances, receive will begin before all transmit events have started. The echo signals from different elements of the receive aperture are combined (beamformed) before being sent over a single cable (first signal line 856) or they are transmitted along separate paths (first signal line 856, second signal line 866, etc.). In several aspects, a sum element is included in the IVUS catheter 102. The summed value of the received echo signals of the plurality of transducer elements may be transmitted on the first signal line 856. In one or more instances, the echo signals being transmitted along the first signal line 856 are the same prior to entering the PIM 104 as the echo signals being transmitted along the first signal line 856 exiting the PIM. In other instances, the echo signals differ when exiting the PIM 104 as some signal processing may occur at the PIM 104.

[0068] In some aspects, the one or more ASICs 840 can implement a receive beamformer with delays 862 and weights 864. The one or more ASICs 840 delays 862 and / or weights 864 to the received echoes prior to the received echoes being transmitted to the PIM 104. In other instances, the receive beamformer circuitry may not be in the catheter 102, and instead implemented in the PIM 104 and / or the computer 106.

[0069] In some aspects, echo signal representative of separate focal depths are sent along different signa lines 856, 866. In some aspects, dynamic beamforming takes place. For example, delays are changed in depth to dynamically focus at different depths, sometimes with aperture growth (limiting aperture size in the near field, for example).

[0070] Figure 9 is a flowchart of a method 884 for performing plane wave pulse sequence in accordance with an example instance. Method 884 is illustrated as a set of operations or blocks 886 through 896 and is described with continuing reference to Figures 1-14. The method 884 begins at a first point in time at the block 886 and progresses to block 896 at a later point in time evidenced by an arrow labeled time steps in Figure 9. Not all of the illustrated blocks 886 through 896 may be performed in all instances of method 884. One or more blocks that are not expressly illustrated in Figure 9 may be included before, after, in between, or as part of the blocks 886 through 896. In one or more instances, the blocks in method 884 are performed within the IVUS catheter 102, using the one or more ASICs 130 (Fig. 1) or 840 (Figs. 10, 12), the PIM 104, and / or the processing system 106. In general, the method 884 is related to using multiple transmit element apertures to produce plane waves in a frame rate efficient manner.

[0071] In an example aspect, method 884 includes transmitting an ultrasound plane wave with a transmit aperture (e.g., elements 1 through N) with delays / phase dispersion at a block 886; receiving ultrasound echoes with a first receive sub-aperture (one or multiple elements) at a block 888; transmitting electrical signal associated with receive by the first receive sub-aperture (one signal line) at a block 890; transmitting ultrasound plane wave with the transmit aperture with delays / phase dispersion at a block 892; receiving ultrasound echoes with a second receive sub-aperture (one or multiple elements) at a block 894; and transmitting an electrical signal associated with receive by the second receive sub-aperture (same one signal line) at a block 896. Similar steps can be repeated with different transmit apertures and different receive apertures / sub-apertures .

[0072] In some aspects, the method 884 forms all or a portion of the block 872 and / or the block 874 of the method 868. In various instances, the method 884 continues subsequently through other receive sub-apertures as described above in relation to first and second receive sub-apertures.

[0073] In one or more instances, the blocks 886 and / or 892 use the phase dispersion described in Figure 5. In one or more instances, the blocks 886 and / or 892 uses the architecture described in Figure 7. In some instances, the sequencer 828 provides a timing sequence 836 to delay the transmit pulsers 844 from sending the ultrasound plane wave. In some instances, the one or more ASICs 840 delays the transmitting of the ultrasound plane wave with the transmit aperture (e.g., elements 1 through N) using the transmit delays 850. Determining the phase dispersion / delays of the blocks 886 and / or 892 can occur within the IVUS catheter 102, the PIM 104, and / or computer 106.

[0074] In some instances, the blocks 888 and / or 894 receives the echo signals on only a single element (e.g., the first receive sub-aperture is a single element and the second receive subaperture is a single element). The other elements of the receive aperture do not receive the echo signals in block 888. In other instances, the blocks 888 and / or 894 can include multiple elements. In some instances, the blocks 888 and / or 894 uses the architecture described in Figure 8.

[0075] In one or more instances, the received echo signals are transmitted as an electrical signal down a single line in the block 890. In some instances, the single line is coupled to the PIM 104 and / or the computer 106. In one or more instances, an additional block between the block 888 and the block 890 is added to conduct signal processing.

[0076] In various instances, the block 892 occurs after the block 890. In one or more instances the block 892 is the same as the block 886, except for the point in time which the block 892 is implemented.

[0077] Figure 10 is a flowchart of a method 898 for performing plane wave pulse sequence in accordance with an example instance. Method 898 is illustrated as a set of operations or blocks 900 through 918 and is described with continuing reference to Figures 1-14. Not all of the illustrated blocks 900 through 918 may be performed in all instances of method 898. One or more blocks that are not expressly illustrated in Figure 10 may be included before, after, in between, or as part of the blocks 900 through 918. In one or more instances, the blocks in method 884 are performed within the IVUS catheter 102, using the one or more ASICs 130 (Fig.1) or 840 (Figs. 10, 12), the PIM 104, and / or the processing system 106. In general, the method 898 is related to using multiple transmit element apertures to produce plane waves in a frame rate efficient manner.

[0078] In an example aspect, method 898 includes transmitting an ultrasound plane wave with a transmit aperture (e.g., elements 1 through N) with delays / phase dispersion at a block 900; receiving ultrasound echoes with a first receive sub-aperture (one or multiple elements) at a block 902 and simultaneously receiving ultrasound echoes with a second receive sub-aperture (one or multiple elements) at a block 904; transmitting echo signals from the receive by the first receive sub-aperture (first signal line) at a block 906 and simultaneously transmitting echo signals from the receive by the second receive sub-aperture (second signal line) at a block 908; transmitting ultrasound plane wave with the transmit aperture with delays / phase dispersion at a block 910; receiving ultrasound echoes with a third receive sub-aperture at a block 912 and simultaneously receiving ultrasound echoes with a fourth receive sub-aperture at a block 914; and transmitting echo signals from the receive by the third receive sub-aperture (first signal line) at a block 916 and transmitting echo signals from the receive by the fourth receive sub-aperture (second signal line) at a block 918. Similar steps can be repeated with different transmit apertures and different receive apertures / sub-apertures.

[0079] In one or more instances, the blocks 900 and / or 910 use the phase dispersion described in Figure 5. In one or more instances, the blocks 900 and / or 910 use the architecture described in Figure 7. In some instances, the sequencer 828 provides a timing sequence 836 to delay the transmit pulsers 844 from sending the ultrasound plane wave. In some instances, the one or more ASICs 840 delays the transmitting of the ultrasound plane wave with the transmit aperture (e.g., elements 1 through N) using the transmit delays 850. In some instances, determining the phase dispersion / delays of the blocks 900 and / or 910 can occur within the IVUS catheter 102, the PIM 104, and / or computer 106.

[0080] In some instances, the blocks 888 and / or 894 receives the echo signals on only a single element (e.g., the first receive sub-aperture is a single element and the second receive subaperture is a single element). The other elements of the receive aperture do not receive the echo signals in block 888. In other instances, the blocks 888 and / or 894 can include multiple elements. In some instances, the blocks 888 and / or 894 uses the architecture described in Figure 8.

[0081] In one or more instances, the received echo signals associated with receive by the first receive sub-aperture are transmitted as an electrical signal down a first signal line in the block 906. In some instances, the first signal line is coupled to the PIM 104 and / or the computer 106. In one or more instances, the received echo signals associated with receive by the second receive sub-aperture are transmitted as an electrical signal down a second signal line in the block 908. In some instances, the second signal line is coupled to the PIM 104 and / or the computer 106.

[0082] In one or more instances, an additional block between the blocks 902 and 904 and blocks 906 and 908 to conduct signal processing. In some instances, the blocks 906 and 908 are omitted. Instead, the electrical signal associated with receive by element 1 and the electrical signal associated with receive by element 2 are summed within the IVUS catheter 102 and transmitted using only a single signal line.

[0083] In various instances, the block 910 occurs after the simultaneously occurring blocks 906 and 908. In one or more instances the block 910 is the same as the block 900, except for the point in time which the block 910 is implemented.

[0084] In one or more instances, the received echo signals associated with receive by element 3 are transmitted as an electrical signal down the first signal line in the block 916. In some instances, the first signal line is coupled to the PIM 104 and / or the computer 106. In one or more instances, the received echo signals associated with receive by element 4 are transmitted as an electrical signal down the second signal line in the block 918. In some instances, the second signal line is coupled to the PIM 104 and / or the computer 106.

[0085] In one or more instances, an additional block between the blocks 912 and 914 and blocks 916 and 918 to conduct signal processing. In some instances, the blocks 916 and 918 are omitted. Instead, the electrical signal associated with receive by element 3 and the electrical signal associated with receive by element 4 are summed within the IVUS catheter 102 and transmitted using only a single signal line. In some instances, the block 888 uses the architecture described in Figure 8.

[0086] Figure 11 is a cross-sectional representation of an IVUS catheter 102 transmitting ultrasonic planar waves 1040, 1050, according to aspects of the present disclosure. The planar wave 1040 includes wavefront 1042. The planar wave 1040 extends in a first direction. Visible are the transducer elements 212 of the transducer array 124 surrounding the flexible elongate member 121. In the example shown in Figure 11, each pulse transmission 1040 is transmitted bya first aperture 1048 (e.g., N elements 212). As the planar wave 1040 propagates, the wavefront 1042 moves toward the vessel wall 120 over time. The planar wave 1050 includes wavefront 1052. The planar wave 1050 extends in a different, second direction. In the example shown in Figure 11, each pulse transmission 1050 is transmitted by a second sub-aperture 1058 (e.g., a different N elements 212). As the planar wave 1050 propagates, the wavefront 1052 moves toward the vessel wall 120.

[0087] In some instances, the first aperture 1048 and the second aperture 1058 can be any suitable number of ultrasound transducer elements. In one or more aspects, the first aperture 1048 is a same size or a different size than the second aperture 1058. In various aspects, the first aperture 1048 and the second aperture 1058 are rotated any suitable angle (e.g., 90 degrees, 120 degrees, 180 degrees, etc.), so that both the first aperture 1048 and the second aperture 1058 include different transducer elements. In some instances, the planar wave 1040 of the first aperture 1048 is sent simultaneously to the planar wave 1050 of the second aperture 1058, as described above. In other instances, the planar wave 1040 of the first aperture 1048 is sent at a different time than the planar wave 1050 of the second aperture 1058. In order to get the planar waves 1040, 1050, phase dispersion is used as described above.

[0088] Figure 12A is a cross-sectional representation of an IVUS catheter 102 transmitting ultrasonic planar waves 1060, according to aspects of the present disclosure. The planar wave 1060 is circumferentially extending around the transducer elements 212 and propagating out toward the vessel wall 120 and the plaque 1062 coupled to the vessel wall 120. Visible are the transducer elements 212 of the transducer array 124 surrounding the flexible elongate member 121. In the example shown in Figure 12A, the planar wave 1050 is transmitted by an aperture including all transducer elements of the circumferential array 124.

[0089] Figure 12B is a cross-sectional representation of an IVUS catheter 102 receiving echo signals 1064 of the ultrasonic planar waves 1060, according to aspects of the present disclosure. The echo signals 1064 are propagating away from the vessel wall 120 including the plaque 1062 toward the transducer elements 212. Visible are the transducer elements 212 of the transducer array 124 surrounding the flexible elongate member 121. In the example shown in Figure 12B, the echo signals 1064 are sampled using a plurality of receive sub-apertures 1066 (e.g., with M transducer elements each)

[0090] In operation, with continuing reference to Figure 12A and Figure 12B, the transmit beamformer ASIC 802 sends electric signals to the pulsers 804. The pulsers 804 transmit the ultrasonic pulse down the plurality of signal lines 806 to the ultrasound transducer elements 212 of the array 124. Using phase dispersion, the ultrasonic planar wave 1060 is emitted. The planar wave 1060 propagates from the transducer elements 212 toward the vessel wall. When the planar wave 1060 contacts the vessel wall 120 and the plaque 1062, the planar wave 1060 move the vessel wall 120 and / or the plaque 1062. Echo signals are sent back toward the transducer elements 212 and are representative of the motion of the vessel wall 120.

[0091] Figure 13A is a cross-sectional representation of an IVUS catheter 102 transmitting ultrasonic planar waves 1060, according to aspects of the present disclosure. The planar wave 1060 is circumferentially extending around the transducer elements 212 and propagating out toward the vessel wall 120 and the plaque 1062 coupled to the vessel wall 120. The vessel wall 120 includes first portion 120a and a second portion 120b. The first portion 120a is opposite the second portion 120b on the vessel wall 120. Visible are the transducer elements 212 of the transducer array 124 surrounding the flexible elongate member 121. In the example shown in Figure 13 A, the planar wave 1050 is transmitted by an aperture including all transducer elements of the circumferential array 124.

[0092] Figure 13B is a cross-sectional representation of an IVUS catheter 102 receiving echo signals 1064 of the ultrasonic planar waves 1060, according to aspects of the present disclosure. The echo signals 1064 are propagating away from the vessel wall 120 including the first portion 120a of the vessel wall 120 and the second portion 120b of the vessel wall 120 toward the transducer elements 212. Visible are the transducer elements 212 of the transducer array 124 surrounding the flexible elongate member 121. In the example shown in Figure 13B, the echo signals 1064 are sampled using a plurality of receive sub-apertures 1066 (e.g., with M transducer elements each).

[0093] In operation, with continuing reference to Figure 12A and Figure 12B, the transmit beamformer ASIC 802 sends electric signals to the pulsers 804. The pulsers 804 transmit the ultrasonic pulse down the plurality of signal lines 806 to the ultrasound transducer elements 212 of the array 124. Using phase dispersion, the ultrasonic planar wave 1060 is emitted. The planar wave 1060 propagates from the transducer elements 212 toward the vessel wall. When the planar wave 1060 contacts or push the vessel wall 120 and the plaque 1062, echo signals 1064 are sentback toward the transducer elements 212. The plurality of receive sub-apertures 1066 are used to sample the echo signal 1064 in different places of the vessel. This time-of-flight information may be used to determine if the IVUS catheter 102 and / or the ultrasound transducer array 124 is centered within the vessel 120. As shown in Figures 22A and 22B, the IVUS catheter 102 is closer to the first portion of the vessel wall 120 than the second portion 120b of the vessel wall 120. The echo signals 1064 that return from the second portion 120b of the vessel wall 120 will take longer to return to a receive sub-aperture 1066 than the echo signals 1064 from the first portion 120a of the vessel wall 120, since the distance from the IVUS catheter 102 to the second portion 120b of the vessel wall 120 is greater than the distance from the IVUS catheter 102 to the first portion of the vessel wall 120.

[0094] It will also be understood that one or more of the steps of the methods described above can be performed by one or more components of an ultrasound imaging system, such as the processing system, a multiplexer, a beamformer, a signal processing unit, an image processing unit, or any other suitable component of the system. For example, activating the scan sequences may be carried out by a processor in communication with a multiplexer configured to select or activate one or more elements of an ultrasound transducer array. In some instances, generating the ultrasound images may include beamforming incoming signals from the ultrasound imaging device and processing the beamformed signals by an image processor. The processing components of the system can be integrated within the ultrasound imaging device, contained within an external console, or may be a separate component.

[0095] A system of one or more computers can be configured to perform particular operations or actions by virtue of having software, firmware, hardware, or a combination of them installed on the system that in operation causes or cause the system to perform the actions. One or more computer programs can be configured to perform particular operations or actions by virtue of including instructions that, when executed by data processing apparatus, cause the apparatus to perform the actions. Aspects can include corresponding computer systems, apparatus, and computer programs recorded on one or more computer storage devices, each configured to perform the actions of the methods.

[0096] One general aspect includes a system an intravascular ultrasound (IVUS) catheter may include: a flexible elongate member configured to be positioned within a blood vessel of a patient; and a circumferential array of acoustic elements, where each acoustic element of thecircumferential array is configured to transmit ultrasound energy and receive echoes associated with the transmitted ultrasound energy; and one or more processors configured for communication with the circumferential array, where the one or more processors is configured to: control a first aperture of the circumferential array to transmit a first ultrasound plane wave, where the first aperture may include a first plurality of acoustic elements forming a first circumferential portion of the circumferential array; control the first aperture to receive echoes corresponding to the first ultrasound plane wave; generate a circumferential ultrasound image based on the echoes corresponding to the first ultrasound plane wave; and output the circumferential ultrasound image to a display in communication with the processor.

[0097] Implementations may include one or more of the following features. The system where the first plurality of acoustic elements may include a first acoustic element and a second acoustic element, where, to control the first aperture to transmit the first ultrasound plane wave, the one or more processors is configured to provide a time delay between activation of the first acoustic element to transmit the ultrasound energy and the activation of the second acoustic element to transmit the ultrasound energy. The time delay is configured to prevent the ultrasound energy transmitted by the first plurality of acoustic elements from focusing such that the transmitted ultrasound energy forms the first ultrasound plane wave. The IVUS catheter further may include a transmit beamformer integrated circuit (IC) configured to provide the time delay, where the transmit beamformer IC is one of the one or more processors. The system the one or more processors is configured to activate each acoustic element of the first plurality of acoustic elements to transmit the ultrasound energy before the processor controls any one acoustic element of the first plurality of acoustic elements to receive the echoes. The one or more processors is configured to: control a plurality of second apertures of the circumferential array to transmit a plurality of second ultrasound plane waves; control the plurality of second apertures to receive the echoes corresponding to the plurality of second ultrasound plane waves; and generate the circumferential ultrasound image based on the received echoes corresponding to the plurality of second ultrasound plane waves, and where each second aperture of the plurality of second apertures may include a second plurality of acoustic elements forming a second circumferential portion of the circumferential array, where the first aperture and the plurality of second circumferential apertures are distributed around the circumferential array. Each acoustic element of the circumferential array is angled relative to an adjacent acoustic element of thecircumferential array such that the first ultrasound plane wave and each second ultrasound plane wave of the plurality of second ultrasound planes waves are transmitted in different directions around the circumference. To control the first aperture to receive the echoes, the processor is configured to control a first sub-aperture and a second sub-aperture of the first aperture to simultaneously receive the echoes, where the IVUS catheter may include a plurality of electrical conductors in communication with the circumferential array, where the plurality of electrical conductors may include: a first electrical conductor configured to carry electrical signals representative of the echoes received by the first sub-aperture from a distal portion of the IVUS catheter to a proximal portion of the IVUS catheter; and a second electrical conductor configured to carry electrical signals representative of the echoes received by the second sub-aperture from the distal portion of the IVUS catheter to the proximal portion of the IVUS catheter. To control the first aperture to receive the echoes, the processor is configured to control a first sub-aperture and a second sub-aperture of the first aperture to simultaneously receive the echoes, where the IVUS catheter may include a receive beamformer integrated circuit (IC) configured to perform beamforming for electrical signals representative of the echoes received by the first sub-aperture and electrical signals representative of the echoes received by the second sub-aperture, where the receive beamformer IC is one of the one or more processors. The IVUS catheter further may include a flexible substrate positioned at a distal portion of the flexible elongate member and a beamformer integrated circuit (IC) configured perform at least one of transmit beamforming or receive beamforming, where the circumferential array and the beamformer IC are coupled to the flexible substrate.

[0098] One general aspect includes a method providing an intravascular ultrasound (IVUS) catheter may include: a flexible elongate member configured to be positioned within a blood vessel of a patient; and a circumferential array of acoustic elements, where each acoustic element of the circumferential array is configured to transmit ultrasound energy and receive echoes associated with the transmitted ultrasound energy; control, with one or more processors in communication with the circumferential array, a first aperture of the circumferential array to transmit a first ultrasound plane wave, where the first aperture may include a first plurality of acoustic elements forming a first circumferential portion of the circumferential array; controlling, with the one or more processors, the first aperture to receive echoes corresponding to the first ultrasound plane wave; generating, with the one or more processors, a circumferential ultrasoundimage based on the echoes corresponding to the first ultrasound plane wave; and outputting, with the one or more processors, the circumferential ultrasound image to a display in communication with the processor.

[0099] One general aspect includes a system an intravascular ultrasound (IVUS) catheter may include: a flexible elongate member configured to be positioned within a blood vessel of a patient; and a circumferential array of acoustic elements, where each acoustic element of the circumferential array is configured to transmit ultrasound energy and receive echoes associated with the transmitted ultrasound energy; and one or more processors configured for communication with the circumferential array, where the one or more processors is configured to: control all of the acoustic elements of the circumferential array to transmit an ultrasound plane wave; control the circumferential array to receive echoes corresponding to the ultrasound plane wave; generate a graphical representation associated with the blood vessel based on the echoes corresponding to the ultrasound plane wave; and output the graphical representation of the blood vessel to a display in communication with the processor.

[0100] Implementations may include one or more of the following features. The system where the processor is configured to determine if the IVUS catheter is centered within the blood vessel based on the echoes, where the graphical representation corresponds to the determination.

[0101] One general aspect includes a method providing an intravascular ultrasound (IVUS) catheter may include: a flexible elongate member configured to be positioned within a blood vessel of a patient; and a circumferential array of acoustic elements positioned around a circumference of the flexible elongate member, where each acoustic element of the circumferential array is configured to transmit ultrasound energy and receive echoes associated with the transmitted ultrasound energy; controlling, with the one or more processors in communication with the circumferential array, all of the acoustic elements of the circumferential array to transmit an ultrasound plane wave; controlling, with the one or more processors, the circumferential array to receive echoes corresponding to the ultrasound plane wave; generating, with the one or more processors, a graphical representation associated with the blood vessel based on the echoes corresponding to the ultrasound plane wave; and outputting, with the one or more processors, the graphical representation of the blood vessel to a display in communication with the processor.

[0102] It is noted that flow diagrams and block diagrams are provided herein for exemplary purposes; a person of ordinary skill in the art will recognize myriad variations that nonetheless fall within the scope of the present disclosure. For example, block diagrams may show a particular arrangement of components, modules, services, steps, processes, or layers, resulting in a particular data flow. It is understood that some instances of the systems disclosed herein may include additional components, that some components shown may be absent from some instances, and that the arrangement of components may be different than shown, resulting in different data flows while still performing the methods described herein.

[0103] Similarly, the logic of flow diagrams may be shown as sequential. However, similar logic could be parallel, massively parallel, object oriented, real-time, event-driven, cellular automaton, or otherwise, while accomplishing the same or similar functions. In order to perform the methods described herein, a processor may divide each of the steps described herein into a plurality of machine instructions and may execute these instructions at the rate of several hundred, several thousand, several million, or several billion per second, in a single processor or across a plurality of processors. Such rapid execution may be necessary in order to execute the method in real time or near-real time as described herein.

[0104] The logical operations making up the instances of the technology described herein are referred to variously as operations, steps, objects, elements, components, modules, etc. Furthermore, it should be understood that these may occur or be performed or arranged in any order, unless explicitly claimed otherwise or a specific order is inherently necessitated by the claim language.

[0105] All directional references e.g., upper, lower, inner, outer, upward, downward, left, right, lateral, front, back, top, bottom, above, below, vertical, horizontal, clockwise, counterclockwise, proximal, and distal are only used for identification purposes to aid the reader’s understanding of the claimed subject matter, and do not create limitations, particularly as to the position, orientation, or use of the multi-frequency IVUS imaging system. Connection references, e.g., attached, coupled, connected, joined, or “in communication with” are to be construed broadly and may include intermediate members between a collection of elements and relative movement between elements unless otherwise indicated. As such, connection references do not necessarily imply that two elements are directly connected and in fixed relation to each other. The term “or” shall be interpreted to mean “and / or” rather than “exclusive or.” The word“comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. Unless otherwise noted in the claims, stated values shall be interpreted as illustrative only and shall not be taken to be limiting.

[0106] The above specification, examples and data provide a complete description of the structure and use of exemplary instances of the IVUS imaging system using plane waves as defined in the claims. Although various instances of the claimed subject matter have been described above with a certain degree of particularity, or with reference to one or more individual instances, those skilled in the art could make numerous alterations to the disclosed instances without departing from the spirit or scope of the claimed subject matter.

[0107] Still other instances are contemplated. It is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative only of particular instances and not limiting. Changes in detail or structure may be made without departing from the basic elements of the subject matter as defined in the following claims.

Claims

CLAIMSWhat is claimed is:

1. A system, comprising: an intravascular ultrasound (IVUS) catheter comprising: a flexible elongate member configured to be positioned within a blood vessel of a patient; and a circumferential array of acoustic elements, wherein each acoustic element of the circumferential array is configured to transmit ultrasound energy and receive echoes associated with the transmitted ultrasound energy; and one or more processors configured for communication with the circumferential array, wherein the one or more processors is configured to: control a first aperture of the circumferential array to transmit a first ultrasound plane wave, wherein the first aperture comprises a first plurality of acoustic elements forming a first circumferential portion of the circumferential array; control the first aperture to receive echoes corresponding to the first ultrasound plane wave; generate a circumferential ultrasound image based on the echoes corresponding to the first ultrasound plane wave; and output the circumferential ultrasound image to a display in communication with the processor.

2. The system of claim 1, wherein the first plurality of acoustic elements comprises a first acoustic element and a second acoustic element, wherein, to control the first aperture to transmit the first ultrasound plane wave, the one or more processors is configured to provide a time delay between activation of the first acoustic element to transmit the ultrasound energy and the activation of the second acoustic element to transmit the ultrasound energy.

3. The system of claim 2, wherein the time delay is configured to prevent the ultrasound energy transmitted by the first plurality of acoustic elements from focusing such that the transmitted ultrasound energy forms the first ultrasound plane wave.

4. The system of claim 2, wherein the IVUS catheter further comprises a transmit beamformer integrated circuit (IC) configured to provide the time delay, wherein the transmit beamformer IC is one of the one or more processors.

5. The system of claim 1, the one or more processors is configured to activate each acoustic element of the first plurality of acoustic elements to transmit the ultrasound energy before the processor controls any one acoustic element of the first plurality of acoustic elements to receive the echoes.

6. The system of claim 1, wherein the one or more processors is configured to: control a plurality of second apertures of the circumferential array to transmit a plurality of second ultrasound plane waves; control the plurality of second apertures to receive the echoes corresponding to the plurality of second ultrasound plane waves; and generate the circumferential ultrasound image based on the received echoes corresponding to the plurality of second ultrasound plane waves, and wherein each second aperture of the plurality of second apertures comprises a second plurality of acoustic elements forming a second circumferential portion of the circumferential array, wherein the first aperture and the plurality of second circumferential apertures are distributed around the circumferential array.

7. The system of claim 6, wherein each acoustic element of the circumferential array is angled relative to an adjacent acoustic element of the circumferential array such that the firstultrasound plane wave and each second ultrasound plane wave of the plurality of second ultrasound planes waves are transmitted in different directions around the circumference.

8. The system of claim 1, wherein, to control the first aperture to receive the echoes, the processor is configured to control a first sub-aperture and a second sub-aperture of the first aperture to simultaneously receive the echoes, wherein the IVUS catheter comprises a plurality of electrical conductors in communication with the circumferential array, wherein the plurality of electrical conductors comprises: a first electrical conductor configured to carry electrical signals representative of the echoes received by the first sub-aperture from a distal portion of the IVUS catheter to a proximal portion of the IVUS catheter; and a second electrical conductor configured to carry electrical signals representative of the echoes received by the second sub-aperture from the distal portion of the IVUS catheter to the proximal portion of the IVUS catheter.

9. The system of claim 1, wherein, to control the first aperture to receive the echoes, the processor is configured to control a first sub-aperture and a second sub-aperture of the first aperture to simultaneously receive the echoes, wherein the IVUS catheter comprises a receive beamformer integrated circuit (IC) configured to perform beamforming for electrical signals representative of the echoes received by the first sub-aperture and electrical signals representative of the echoes received by the second sub-aperture, wherein the receive beamformer IC is one of the one or more processors.

10. The system of claim 1 , wherein the IVUS catheter further comprises a flexible substrate positioned at a distal portion of the flexible elongate member and a beamformer integrated circuit (IC) configured perform at least one of transmit beamforming or receive beamforming,wherein the circumferential array and the beamformer IC are coupled to the flexible substrate.

11. A method, comprising: providing an intravascular ultrasound (IVUS) catheter comprising: a flexible elongate member configured to be positioned within a blood vessel of a patient; and a circumferential array of acoustic elements, wherein each acoustic element of the circumferential array is configured to transmit ultrasound energy and receive echoes associated with the transmitted ultrasound energy; control, with one or more processors in communication with the circumferential array, a first aperture of the circumferential array to transmit a first ultrasound plane wave, wherein the first aperture comprises a first plurality of acoustic elements forming a first circumferential portion of the circumferential array; controlling, with the one or more processors, the first aperture to receive echoes corresponding to the first ultrasound plane wave; generating, with the one or more processors, a circumferential ultrasound image based on the echoes corresponding to the first ultrasound plane wave; and outputting, with the one or more processors, the circumferential ultrasound image to a display in communication with the processor.

12. A system, comprising: an intravascular ultrasound (IVUS) catheter comprising: a flexible elongate member configured to be positioned within a blood vessel of a patient; and a circumferential array of acoustic elements, wherein each acoustic element of the circumferential array is configured to transmit ultrasound energy and receive echoes associated with the transmitted ultrasound energy; and one or more processors configured for communication with the circumferential array, wherein the one or more processors is configured to:control all of the acoustic elements of the circumferential array to transmit an ultrasound plane wave; control the circumferential array to receive echoes corresponding to the ultrasound plane wave; generate a graphical representation associated with the blood vessel based on the echoes corresponding to the ultrasound plane wave; and output the graphical representation of the blood vessel to a display in communication with the processor.

13. The system of claim 12, wherein the processor is configured to determine if the IVUS catheter is centered within the blood vessel based on the echoes, wherein the graphical representation corresponds to the determination.

14. A method, comprising: providing an intravascular ultrasound (IVUS) catheter comprising: a flexible elongate member configured to be positioned within a blood vessel of a patient; and a circumferential array of acoustic elements positioned around a circumference of the flexible elongate member, wherein each acoustic element of the circumferential array is configured to transmit ultrasound energy and receive echoes associated with the transmitted ultrasound energy; controlling, with the one or more processors in communication with the circumferential array, all of the acoustic elements of the circumferential array to transmit an ultrasound plane wave; controlling, with the one or more processors, the circumferential array to receive echoes corresponding to the ultrasound plane wave; generating, with the one or more processors, a graphical representation associated with the blood vessel based on the echoes corresponding to the ultrasound plane wave; and outputting, with the one or more processors, the graphical representation of the blood vessel to a display in communication with the processor.

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