Intravascular ultrasound (IVUS) imaging with frame sequencing and persistence, and associated systems, devices, and methods

Abstract

A system includes a processor that communicates with the circumferential array of an intravascular ultrasound catheter. The processor generates first ultrasound data associated with first echoes received at a first aperture of the circumferential array. The processor generates second ultrasound data associated with second echoes received at a second aperture of the circumferential array, where the second echoes are received after the first echoes. The processor combines the first ultrasound data and second ultrasound data to generate combined ultrasound data. The processor generates an ultrasound image from the combined ultrasound data, where the first aperture and second aperture are associated with different locations on the circumferential array.

Description

2024PF00440INTRAVASCULAR ULTRASOUND (IVUS) IMAGING WITH FRAME SEQUENCING AND PERSISTENCE, AND ASSOCIATED SYSTEMS, DEVICES, AND METHODSTECHNICAL FIELD

[0001] The present disclosure relates generally to intravascular ultrasound (IVUS) imaging using a catheter positioned inside of a blood vessel and, in particular, to frame sequencing and interpolation 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 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] Improved frame rates are often sought for IVUS imaging. Existing methods may achieve higher frame rates by reducing the amount of ultrasound generated during imaging. For example, beams may be skipped during an imaging sequence thus reducing the number of scan lines. In other words, existing methods achieve higher frame rates by acoustically undersampling the environment being imaged. However, undersampling results in a loss in image quality, which may make it unacceptable for imaging procedures.

[0004] 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.2024PF00440SUMMARY

[0005] Disclosed herein are systems, devices, and methods of frame sequencing and persistence for IVUS imaging during a pullback. Frame sequencing refers to the order in which frames are constructed during an imaging procedure, and frame persistence refers to the degree to which ultrasound data in early frames in a sequence is used to generate later frames. For frame sequencing during an IVUS pullback procedure, frames are obtained sequentially at different locations along the pullback, and the individual frames are acoustically under-sampled in the circumferential direction. Furthermore, sequential frames during the pullback are circumferentially offset. For frame persistence, a combined frame is generated by combining two sequential frames obtained during the pullback procedure. In one example, during the pullback procedure, frames alternate between odd frames, i.e., those with apertures centered on odd transducer elements, and even frames, i.e., those with apertures centered on even transducer elements. A combined frame is generated by combining a sequential even frame and odd frame. The combined frame may be displayed to a user. The IVUS imaging with frame sequencing and persistence advantageously improves frame rates for a display while maintaining image quality.

[0006] 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 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

[0007] Illustrative instances of the present disclosure will be described with reference to the accompanying drawings, of which:

[0008] Figure l is a schematic diagram of an intraluminal imaging system, according to aspects of the present disclosure.

[0009] Figure l is a schematic diagram of a processor circuit, according to instances of the present disclosure.

[0010] Figure 3A is a perspective view of an IVUS catheter at a first position along a body lumen, according to aspects of the present disclosure.2024PF00440

[0011] Figure 3B is a diagram of receive beam profiles of odd apertures of the IVUS catheter of Figure 3 A, according to aspects of the present disclosure.

[0012] Figure 4A is a perspective view of an IVUS catheter at a second position along a body lumen, according to aspects of the present disclosure.

[0013] Figure 4B is a diagram of receive beam profiles of even apertures of the IVUS catheter of Figure 4A, according to aspects of the present disclosure.

[0014] Figure 5A is a perspective view of an IVUS catheter at a third position along a body lumen, according to aspects of the present disclosure.

[0015] Figure 5B is a diagram receive beam profiles of odd apertures of the IVUS catheter of Figure 5 A, according to aspects of the present disclosure.

[0016] Figure 6A is a perspective view of an IVUS catheter at the first position and the second position along a body lumen as depicted in Figures 3 A and 4A, according to aspects of the present disclosure.

[0017] Figure 6B is a diagram of an overlap of circumferential receive beam profiles of the first aperture and second aperture of the IVUS catheter of Figure 6 A, according to aspects of the present disclosure.

[0018] Figure 7 is a diagram of overlapping longitudinal receive beam profiles for a first aperture of an IVUS catheter at two positions during a pullback, according to aspects of the present disclosure.

[0019] Figure 8 is a diagram of the varying intensity of a circumferential beam profile of a first aperture of an IVUS catheter, according to aspects of the present disclosure.

[0020] Figure 9 is a diagram of scan conversion of radial scan lines, according to aspects of the present disclosure.

[0021] Figure 10 is a diagram of the difference between intensities of overlapping circumferential beam profiles from a first aperture and second aperture of an IVUS catheter, according to aspects of the present disclosure.

[0022] Figure 11 is a flow diagram for a method combining a first and second frame of ultrasound data, according to aspects of the present disclosure.

[0023] Figure 12 is a flow diagram for a method scan-converting a first and second frame of ultrasound data, according to aspects of the present disclosure.2024PF00440

[0024] Figure 13 is a flow diagram for a method combining ultrasound data from a first and second aperture, 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. 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] Signal processing optimization techniques are desired to increase frame rates and produce better image resolution in IVUS imaging systems, including those for blood flow images (e.g., ChromaFlo) and B-mode images. Methods of improving frame rates, e.g., by acoustic undersampling, often result in reduced image quality. However, by combining image frames2024PF00440which are individually acoustically undersampled in a combined frame, image quality is improved without significant degradation of the frame rate. For example, during an IVUS pullback procedure, frames are obtained at different locations along pullback, and the individual frames are acoustically under-sampled in the circumferential direction (around the transducer array) because beam patterns’ main beam areas are not overlapping or are minimally overlapping in the circumferential direction. Each frame in a sequence of frames has sparse beam patterns that are circumferentially offset. By combining sequential frames from the sequence, a combined frame is generated that is acoustically oversampled in the circumferential direction. In one example, frames alternate between odd frames, i.e., those with apertures centered on odd transducer elements, and even frames, i.e., those with apertures centered on even transducer elements. A frame for display to, or use by, a user is made by combining a sequential even and an odd frame.

[0027] 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. The system as claimed herein may in one example be the processing system or console 106. This system may include the catheter, and optionally also the monitor or other display device. The processing system or console may take the form of a workstation, with or without the monitor or other display device, but this is not needed per se as other forms are contemplated too.

[0028] 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 array2024PF00440124 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.

[0029] 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 32 and 10000 ultrasound transducer elements, between 50 and 100 ultrasound transducer elements, between 100 and 150 ultrasound transducer elements, including values, such as 32, 60, 64, 75, 100, 120, 128, 150 ultrasound transducer elements, and / or other values both larger and smaller.

[0030] 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.

[0031] 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 the medium surrounding the scanner assembly 110. The console 106 outputs image data such that2024PF00440an 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 structures and / or associated 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.

[0032] 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.

[0033] 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 to direct the device 102 through the vessel 120.

[0034] In some instances, blood flow determination algorithms such as Philips ChromaFlo, power Doppler, and / or color flow (Doppler) can be used. Examples of blood flow imaging from apertures of a IVUS device can be found for example in U.S. Pub. No. 2022 / 0361841, U.S. Pub. No. 2021 / 0345989, U.S. Pat. No. 5,921,931m as well as U.S. Pub. No. 2015 / 0087986. Further example, include U.S. Provisional Patent Application No. 61 / 587,834, and U.S. Provisional Patent Application No. 61 / 646,080, the content of each of which is incorporated by reference herein its entirety.2024PF00440

[0035] Figure l is a schematic diagram of a processor circuit 250, according to aspects of the present disclosure. The processor circuit 250 may be implemented in the intraluminal imaging system 100, e.g. in the processing system 106, or it may be implemented in 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 250 may include a processor 260, a memory 264, and a communication module 268. These elements may be in direct or indirect communication with each other, for example via one or more buses. The processor circuit may be partly or entirely implemented in the PIM. In some embodiments the processor circuit is partly implemented in the PIM and partly implemented in the processing system 106.

[0036] The processor 260 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 260 may also comprise another hardware device, a firmware device, or any combination thereof configured to perform the operations described herein. The processor 260 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.

[0037] The memory 264 may include a cache memory (e.g., a cache memory of the processor 260), 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 264 includes a non-transitory computer-readable medium. The memory 264 may store instructions 266. The instructions 266 may include instructions that, when executed by the processor 260, cause the processor 260 to perform the operations described herein. Instructions 266 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”2024PF00440may 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.

[0038] The communication module 268 can include any electronic circuitry and / or logic circuitry to facilitate direct or indirect communication of data between the processor circuit 250, and other processors or devices. In that regard, the communication module 268 can be an input / output (I / O) device. In some instances, the communication module 268 facilitates direct or indirect communication between various elements of the processor circuit 250 and / or the intraluminal imaging system 100. The communication module 268 may communicate within the processor circuit 250 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.

[0039] 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.2024PF00440Information may also be transferred on physical media such as a USB flash drive or memory stick.

[0040] Figures 3 A-6B depict an IVUS catheter at three sequential positions along a vessel during an IVUS pullback procedure. Associated with each position is a frame’s worth of ultrasound data that has been collected from echoes received at a transducer array. The ultrasound data for each frame is collected from a set of apertures, each aperture having an expected receive beam pattern. The expected receive beam patterns are three-dimensional and continuously varying in intensity. For ease of depiction, receive beam patterns are shown in two-dimensional cross-sections. The first type of cross-section, shown in Figures 3B, 4B, 5B, 6B, and 8-10 is a circumferential cross-section, i.e., a cross-section through the transducer array and orthogonal to the elevation / longitudinal direction of the transducer elements. The second type of cross-section, shown in Figure 7, is a longitudinal cross-section, i.e., a cross-section parallel to the elevation direction of the transducer elements. Furthermore, as a proxy for the continuously varying receive beam pattern, the receive beam patterns are depicted as level sets or profiles that include an inner region (indicative of higher sensitivities of the receive beam pattern), intermediate region (indicative sensitivities lower than those in the inner region), and outer region (indicative of sensitivities lower than those in the intermediate region).

[0041] As described in more detail below, the frames generated for each position are acoustically undersampled, and the expected beam patterns of each sequential frame are circumferentially offset from the previous and next frame. Acoustic undersampling occurs when the expected receive beam patterns of neighboring apertures do not overlap or minimally overlap. Due to the circumferential offset between sequential frames, combining two or more sequential frames may improve acoustic sampling.

[0042] Figure 3A is a perspective view of an IVUS catheter 102 at a first position 305 along a vessel 120, according to aspects of the present disclosure. As described in Figure 1, a catheter 102 may include a transducer array 124 that is capable of transmitting and receiving ultrasonic acoustic waves. The acoustic waves received by the transducer array 124 may be referred to as echoes. Transducer array 124 may receive echoes from earlier transmitted acoustic pulses reflecting off features surrounding the catheter 102, e.g., blood, vessel walls, and other structures within and around the vessel 120 in the line of sight of transducer array 124.2024PF00440

[0043] Imaging of the vessel 120 and surrounding structures may occur during a pullback of the IVUS catheter 102. During a pullback procedure, a physician or other medical professional may cause the catheter, manually or by use of a motor, to move through the vessel 120. As the pullback procedure proceeds the vessel, flow within the vessel, or other anatomical features along the vessel may be imaged and analyzed at different positions. The catheter 102 may move in a direction, e.g., along the vessel 120, indicated by arrow 302 during the pullback procedure.

[0044] Figure 3B is a diagram of receive beam profiles of odd apertures of the IVUS catheter 102 of Figure 3 A, according to aspects of the present disclosure. A first odd aperture may be centered on transducer element 124(i) and have an expected receive beam profile 310, which includes an inner region 320, intermediate region 330, and outer region 340. A second odd aperture may be centered on transducer element 124(3) and have an expected receive beam profile 315 with inner region, intermediate region, and outer region, similar to those of receive beam profile 310. Apertures centered on the remaining odd numbered transducer elements have similar expected receive beam profiles. Only two are visible in Fig. 3B for clarity of illustration.

[0045] As described in Figure 1, transducer array 124 may include several ultrasonic transducer elements, including a first transducer element 124(i), second transducer element 124(2), and third transducer element 124(3). The transducer elements of the transducer array 124 may receive ultrasonic echoes. Transducer elements may be grouped into apertures which are used to construct ultrasound data. For example, a five-element aperture might be centered on the first transducer element 124(i) and include the first transducer element 124(i) and two nearest transducer elements on both sides of the first transducer element 124(i). In some aspects, an aperture can be constructed in a synthetic aperture sequence in which individual transmit / receive element pairs or element groups (more than single element transmit and more than single element receive) are combined subsequently in signal processing by, e.g., PIM 104 and / or processing system 106. Each aperture has a receive beam profile reflecting the sensitivity of the aperture to received echoes. A five-element aperture is just one example — apertures could include any number of suitable elements, e.g., 1, 2, 3, ... , N transducer elements, where N is limited by the number of transducers in the transducer array.

[0046] In some aspects, a first frame (also referred to as an odd frame) may be constructed from the ultrasound data gathered by apertures centered on odd numbered transducer elements, e.g., an aperture centered on element 124(i), 123(3), etc. Ultrasound data is generated by the2024PF00440echoes received at transducer elements of apertures centered on odd numbered transducer elements. As described above, the first frame is acoustically undersampled in the circumferential direction, as shown by the minimal overlap of first receive beam pattern 310 and second receive beam pattern 315.

[0047] In some aspects, apertures may be associated with different locations on the circumferential array. For example, when there are an odd number of acoustic elements in an aperture, the aperture may be centered at the location of the middle acoustic element in the aperture, e.g., the second element in a three-element aperture, the third element in a five-element aperture, etc. In another example, when there are an even number of acoustic elements in an aperture, the aperture may be centered at a location between two acoustic elements, e.g., for apertures with even numbers of acoustic elements. In this way, a two-element aperture may be centered at a point between the first and second acoustic elements, such as the midpoint. These examples are merely exemplary. Other configurations of acoustic elements in an aperture may be utilized, resulting in an aperture centered at or between acoustic elements of the circumferential array. In some aspects, the location at which an aperture is centered may also correspond to the orientation of the aperture’s receive beam profile. In some aspects, as used herein, a reference made to an aperture centered on an acoustic element should be understood to include an aperture centered between or around acoustic elements of the circumferential array.

[0048] Figure 4A is a perspective view of an IVUS catheter at a second position 405 along a vessel 120, according to aspects of the present disclosure. Figure 4A depicts the catheter 102 of Figure 3 A after it has moved a short distance to a second position 405, e.g. during a pullback procedure. Imaging of the vessel 120 and surrounding structures occurs at or near the second position 405 of the transducer array 124.

[0049] Figure 4B is a diagram of receive beam profiles of even apertures of the IVUS catheter of Figure 4A, according to aspects of the present disclosure. A first even aperture may be centered on transducer element 124(2) and have an expected receive beam profile 410, which includes an inner region 420, intermediate region 430, and outer region 440. A second even aperture may be centered on transducer element 124(4) and have an expected receive beam profile 415 with inner region, intermediate region, and outer region, similar to those of receive beam profile 410. Apertures centered on the remaining even numbered transducer elements have similar expected receive beam profiles. Only two are visible in Fig. 4B for clarity of illustration.2024PF00440

[0050] Transducer elements may be grouped into apertures which are used to construct ultrasound data. For example, a five-element aperture might be centered on the second transducer element 124(2) and include the second transducer element 124(2) and two nearest transducer elements on both sides of the second transducer element 124(2). Each aperture has a receive beam profile reflecting the sensitivity of the aperture to received echoes. Aperture of various sizes may be used, e.g., including 1, 2, 3, ... , N transducer elements, where N is limited by the number of transducers in the transducer array.

[0051] In some aspects, a second frame (also referred to as an even frame) may be constructed from the ultrasound data gathered by apertures centered on even numbered transducer elements, e.g., the first even aperture centered on element 124(2), second even aperture centered on element 124(4), etc. Ultrasound data is generated by the echoes received at transducer elements of apertures centered on even numbered transducer elements. As described above, the second frame is acoustically undersampled in the circumferential direction, as shown by the minimal overlap of first receive beam pattern 410 and second receive beam pattern 415.

[0052] Figure 5A is a perspective view of an IVUS catheter at a third position 505 along a vessel 120, according to aspects of the present disclosure. Figure 5A depicts the catheter 102 of Figure 3 A and 4A after it has moved a short distance to a third position 505, e.g. during a pullback procedure. Imaging of the vessel 120 and surrounding structures occurs at or near the third position 505 of the transducer array 124.

[0053] Figure 5B is a diagram of receive beam profiles of odd apertures of the IVUS catheter of Figure 5 A, according to aspects of the present disclosure. Figure 5B is similar to Figure 3B and the features identified therein are described similarly. After the second position 405 (second frame with even apertures), the next position (the third position 505) generates a third frame (odd frame) with odd apertures. As described above, the third frame is acoustically undersampled, as shown by the minimal overlap of first receive beam pattern 310 and second receive beam pattern 315.

[0054] Additional frames can be generated as catheter 102 is pulled through vessel 120. Each next frame at the next position of the catheter will be circumferentially offset, e.g., by alternating between even and odd frames and described above.

[0055] The use of apertures centered at odd and even numbered transducer elements is one example of how ultrasound data may be gathered to generate frames. In some aspects, a frame2024PF00440may be constructed from apertures centered on every third element. For example, a first frame may be constructed from echoes received at apertures centered on transducer element 1, 4, 7, ... ; a second frame may be constructed from echoes received at apertures centered on transducer elements 2, 5, 8, ... ; a third frame may be constructed from echoes received at apertures centered on transducer elements 3, 6, 9, ... ; and then the sequence of frames repeats as the catheter moves through a vessel. Similarly, apertures centered on every fourth element, fifth element, sixth element, etc. may be used to construct a frame from echoes received at every fourth, fifth, sixth, etc. apertures. As another example, a first frame may be constructed from echoes received at apertures centered on transducer elements 1, 5, 9, ... ; a second frame may be constructed from echoes received at apertures centered on transducer elements 3, 7, 11, ... ; and then the sequence of frames repeats as the catheter moves through a vessel. Other spacings between the apertures are encompassed by this disclosure. In some aspects, apertures separated by N elements may be used, where N=l,2,3, ...8. In some aspects, wider bandwidth transducers may be used, where lower frequency transmit (creating wider beams) allows for additional skipping of elements while still maintaining image quality and sufficiently low image artifacts.

[0056] In some aspects the position(s) of the IVUS catheter, e.g., 305, 405, 505, may be known, e.g., based on tracking radiopaque markers in X-ray image frames and / or coregistration between the intravascular images and x-ray images. In some aspects, the position(s) of the IVUS catheter, e.g., 305, 405, 505, may not be known. When the position(s) of the IVUS catheter are not known, frame data may be used to determine how well correlated the frames are, for example, and determine weighting(s) of different frame data based on the degree of correlation.

[0057] Figures 6A-7 depict configurations, including overlap, of expected receive beam patterns of apertures between consecutive frames. Figures 6A-6B depict how combining two sequential frames can lead to improved acoustic sampling. Figure 7 depicts a factor that may be indicative that combining frames will not suffer from distortion or a degradation of image quality.

[0058] Figure 6A is a perspective view of an IVUS catheter at the first position 305 and the second position 405 along a vessel 120 as depicted in Figures 3A and 4A, according to aspects of the present disclosure. The catheter at the first position 305 is shown in dashed lines; solid lines are used for the catheter at the second position 405.2024PF00440

[0059] Figure 6B is a diagram of an overlap of circumferential receive beam profiles of the first odd aperture and first even aperture of the IVUS catheter of Figure 6 A, according to aspects of the present disclosure. Figure 6B depicts the acoustic oversampling that would occur if apertures centered at each next transducer were used to generate a frame. The acoustic oversampling is indicated by the overlap of the inner receive beam profile regions 320 and 420 of the receive beam profile 310 of the first aperture associated with a first odd frame, as shown in Figure 3B, and the receive beam profile 410 of the first even aperture associated with a second frame, as shown in Figure 4B. Thus, while the individual frames generated at the first position 305 and second position 405 may be acoustically undersampled in the circumferential direction, their combination would have greater acoustic sampling. That is, their combination is acoustically oversampled in the circumferential direction.

[0060] Figure 7 is a diagram of overlapping longitudinal receive beam profiles 720, 730 for a first aperture of an IVUS catheter at two sequential positions during a pullback, according to aspects of the present disclosure. As discussed herein, combining frames to generate new frame provides numerous benefits. To realize those benefits, the longitudinal cross sections of the receive beam patterns between two positions (each position associated with a frame’s worth of ultrasound data) should overlap, i.e., be acoustically oversampled in the elevation / longitudinal direction. Having acoustic oversampling in the elevation direction of the transducer array 124 (similar to longitudinal direction of the IVUS catheter 102) between two positions ensures the features surround the catheter 102 are sufficiently unchanged. In this way, cross-sectional image frames may be combined even though generated from ultrasound data at two different positions of the catheter 102 during pullback.

[0061] As shown in Figures 3 A-5B and described above, multiple frames may be constructed, i.e., a first frame associated with the first position 305 of transducer array 124, a second frame associated with the second position 405 of transducer array 124, and a third frame associated with the third position 505 of transducer array 124. The first frame includes first ultrasound data generated from echoes received at the apertures centered on odd numbered transducer elements, e.g., as shown in Figure 3B. The second frame includes second ultrasound data generated from echoes received at the apertures centered on even numbered transducer elements, e.g., as shown in Figure 4B. The third frame includes third ultrasound data generated2024PF00440from echoes received at the apertures centered on odd numbered transducer elements, e.g., as shown in Figure 5B.

[0062] The three frames, and others generated during a pullback procedure, may be combined and weighted in different configurations to generate combined frames for display or use by a user. For example, the first frame and second frame may be added together or combined to get a first combined frame for display. In other words, the first combined frame includes the ultrasound data of both the first frame and second frame. Similarly, the second frame and third frame may be added together or combined to get a second combined frame for display. In other words, the second combined frame includes the ultrasound data of both the second frame and third frame. Additional ways of combining and weighting frames are included in the description of Figures 8-10 below. For example, frames may be combined with different weightings based on characteristics and differences between the expected receive beam profiles of apertures used in the frames to be combined. Furthermore, combinations and weightings of frames may occur before or after scan conversion, i.e., combination made using the ultrasound data in the form of radial scan lines or combinations made in cartesian coordinates after scan conversion of the radial scan lines of a frame.

[0063] As described herein, a frame may be referred to as a past frame, current frame, or future frame. A current frame may refer to the frame generated from ultrasound data associated with the position of the IVUS catheter to be displayed to a user. A past frame may refer to the frame generated from ultrasound data associated with a previous position of the IVUS catheter. A future frame may refer to the frame generated from ultrasound data associated with a future position of the IVUS catheter. Using Figures 3A-5B as an example, a combined frame may be generated that depicts an image of structures surrounding position 405 of the catheter. The combined frame may be generated by combining one or more of a past frame, current frame, or future frame. In this example, the current frame is the frame comprising the ultrasound data associated with position 405 (as depicted in Figures 4A-4B), the past frame is the frame comprising ultrasound data associated with position 305 (as depicted in Figures 3A-3B), and the future frame is the frame comprising ultrasound data associated with position 505 (as depicted in Figures 5A-5B). In other words, “past,” “current,” and “future” refer to the sequence of frames generated from ultrasound data during an IVUS pullback.2024PF00440

[0064] Figures 8-10 depicts several ways ultrasound data and frames may be weighted to generate combined frames. The combined frame that is displayed on a display to a user may be the results of various weightings and combinations of frames as shown in Figures 3 A-5B and described above. Frames may be combined before, concurrently with, or after scan conversion. In other words, frames may be combined using the radial scan lines in polar coordinates within the circumferential cross-section perpendicular to the elevation direction of the transducer array. Alternatively, the scan line data for each separate frame, e.g., the first odd frame and first even frame described above with respect to Figure 3B and 4B, may be scan converted into pixel data in cartesian coordinates, while at the same time the ultrasound data may be weighted based the pixel location within the expected receive beam profile (this is described below with respect to Figure 8). As used herein, weightings refer to numerical factors that multiply a particular pixel intensity. Furthermore, references to “point” or “points” being weighted refer to the associated pixel intensities at the location of the point(s) being weighted.

[0065] Figure 8 is a diagram of the varying intensity of a circumferential receive beam profile of a first aperture of an IVUS catheter, according to aspects of the present disclosure. As described in Figure 1, an inner beam profile portion 320 has a higher intensity than an intermediate beam profile portion 330, and the intermediate beam profile portion has a higher intensity than outer beam profile portion 340. During signal processing of the ultrasound data into a frame intended for viewing by a user, ultrasound data may be weighted based on the intensity of the received beam profile at a pixel location. For example, first point 805 may receive a higher weight than second point 810, because point 805 is in the inner beam profile portion 320, while second point is in the intermediate beam profile portion 330. More specifically, the higher weight of point 805 and lower weight of points 810 are based on the radial distance (also called depth) from the transducer array. In some aspects, the difference in weighting for two pixels at different angular locations, i.e., their lateral displacement around the transducer array, may not depend on the angular location.

[0066] Figure 9 is a diagram of scan conversion of radial scan lines, according to aspects of the present disclosure. Figure 9 is a zoomed-in version of Figure 3B with additional points identified. Point 910 and point 915 represent the location of two pixels of radial scan line data generated by the first odd aperture (e.g., associated with receive beam profile 310) centered on transducer element 124(i). Point 920 and point 925 represent the location of two pixels of radial2024PF00440scan line data generated by the second odd aperture (e.g., associated with receive beam profile 315) centered on transducer element 124(3). Point 905 represents the location of a cartesian pixel whose value is to be determined from the radial scan line pixel data, i.e., points 910, 915, 920, 925. In some aspects, bilinear interpolation may be used to determine the cartesian pixel value of point 905 from points 910, 915, 920, 925 and distances between each of the points. The points and distances between the points shown in Figure 9 are not necessarily shown to scale. For example, in vascular ultrasound, there may be 512 points per 14mm, or approximately 27pm per pixel and transducer element spacing may be approximately 45pm, so pixel dimensions would be roughly half the element spacing. After scan conversion is completed, the original frame which includes a plurality of radial scan lines is transformed into a cartesian frame comprising a rectangular array of pixels.

[0067] In some aspects, a synthetic beam pattern for an aperture may be generated from the beam patterns of surrounding apertures. The synthetic beam pattern may be weighted and added to subsequent (or previous) frame data from frames with non-synthetic beams centered at the same location as the synthetic beam pattern. For example, a beam centered on 124(2) may be generated from the information at 124(i) and 124(3). The synthetic beam pattern may be weighted and added to subsequent (or previous) frame data from later-generated frames with non-synthetic beams centered at 124(2). These beams may be referred to as "synthetic beams" and / or "interpolated beams." In this way, an interpolated beam may be compared with the next or previous frame’s "real" beams centered at 124(2) in order to potentially improve the correlation of the in-between interpolated beam by comparing the data in the current frame, with beam interpolation with the subsequent and future frame with elevation displaced, but somewhat overlapping acoustic data (in elevation)

[0068] Figure 10 is a diagram of the difference between intensities of overlapping circumferential beam profiles from a first aperture and second aperture of an IVUS catheter, according to aspects of the present disclosure. In some aspects, frame pixel data at a particular location may be weighted based on the difference between the receive beam profiles associated with two apertures. As shown in Figure 10, a few exemplary points are identified. Pixel data at point 1010 is in the intermediate region 430 of receive beam profile 410 and in the inner region 320 of receive beam profile 310. Therefore, the pixel value at point 1010 in a combined frame will be the sum of pixel data from the first frame and the second frame with a greater weighting2024PF00440placed on the first frame because of the higher receive beam intensity at point 1010. Pixel data at point 1015 is in the intermediate region 430 of receive beam profile 410 and in the intermediate region 330 of receive beam profile 310. Therefore, the pixel value at point 1015 in a combined frame will be the sum of pixel data from the first frame and the second frame with an equal weighting for each pixel because of the equal expected receive beam intensity. Pixel data at point 1020 is in the inner region 420 of receive beam profile 410 and further outside of the receive beam profile 310 than outer region 340, i.e., extremely small intensity for expected receive beam profile 310. Therefore, the pixel value at point 1020 in a combined frame will be the sum of pixel data from the first frame and the second frame with a significantly greater weighting placed on the second frame because of the higher receive beam intensity at point 1020 of the expected receive beam profile 410. Similar determinations of weights apply to other points. In some aspects, where an expected receive beam intensity for one profile is higher than for another profile at a point, greater weight should be given to the pixel data associated with the higher intensity beam profile. In some aspects, the relative frame weight can be adjusted based on the specific imaging information inherent in each frame sequence.

[0069] Figures 11-13 present several methods of combining ultrasound data from different frames (e.g., the frames described in Figures 3 A-5B). While the methods are described individually, multiple methods of combining ultrasound data may be used. For example, as described below, two frames of ultrasound data may be combined based on the expected difference between the intensity of expected receive beam profiles and they may be combined based on a comparison of the mean, median, or average flow amplitude of each frame.

[0070] Figure 11 is a flow diagram for a method combining a first and second frame of ultrasound data, according to aspects of the present disclosure. It is understood that the steps of method 1100 may be performed in a different order than shown in Figure 11, additional steps can be provided before, during, and after the steps, and / or some of the steps described can be replaced or eliminated in other aspects. One or more of steps of the method 1100 can be carried by one or more devices and / or systems described herein, such as components of the intraluminal imaging system 100 and / or processor circuit 250.

[0071] At step 1110, a first frame and second frame of ultrasound data are generated, e.g., the first frame and the second frame described above with respect to Figures 3B and 4B,2024PF00440respectively. Both the first frame and second frame may comprise ultrasound data in the form of radial scan lines, each scan line generated from the echoes received at the associated aperture.

[0072] Method 1100 includes two techniques / sub-methods of combining the first and second frame generated in step 1110. The first technique / sub-method includes steps 1120 and 1130, and the second technique / sub-method includes steps 1125 and 1135.

[0073] At step 1120, each of the first frame and second frame may be scan converted (e.g., as shown in Figure 9 and described above), resulting in a rectangular array of pixel data for each frame, and / or each of the first frame and second frame may have their radial scan line data weighted based on expected beam profile intensity (e.g., as shown in Figure 8 and described above) at the location of each pixel in the radial scan line. For example, referring to Figure 8, the pixel at point 805 may have a higher weighting relative to the pixel at point 810. In some aspects, weighting based on expected beam profile intensity may be done after the first frame and second frame are scan converted. In that case, the location of the rectangular pixel can be used to determine the receive beam profile intensity relative to receive beam profile intensity at other locations and the associated weightings may be determined as described in Figure 8.

[0074] At step 1130, the scan-converted first frame and second frame may be combined using weightings based on the expected receive beam profile amplitude difference between the first frame and second frame (e.g., as shown in Figure 10 and described above). In some aspects, the scan-converted first frame and second frame may be combined without weighting, i.e., equally weighted.

[0075] At step 1125, before scan conversion, combine the first and second frame in polar coordinates (i.e., combine the radial scan lines of each frame). The combination may be done using equal weighting 1126 of the first and second frame, higher weighting for the current frame than the past frame 1127 (e.g., weight the second frame higher than the first frame as described above with respect to Figures 4B and 3B, respectively), weighting based on mean or medial flow amplitudes of each frame 1128, or any other image weighting and combination scheme 1129 described herein. In some aspects, the systems and methods described herein may be utilized with blood flow imaging (e.g., ChromaFlo imaging, which determines the amplitude of blood flow around the catheter 102). As used herein, average may refer to mean, median, or mode. The average flow amplitude of each frame may be determined from all the pixel data indicative of flow in a frame. When the average flow amplitude is equal or approximately equal between two2024PF00440frames, then the weightings may be equal or nearly equal. When the average flow amplitude differs between two frames, the current frame may be weighted higher than past frame (and the future frame if three frames are combined). In some aspects, the greater the difference between the average flow amplitudes, the greater the weighting for the current frame compared to the past frame (and future frame).

[0076] At step 1135, the combined frame resulting from step 1125 may be scan converted (e.g., as shown in Figure 9 and described above).

[0077] It is noted that flow 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, 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. 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.

[0078] Figure 12 is a flow diagram for scan-converting a first and second frame of ultrasound data, according to aspects of the present disclosure. It is understood that the steps of method 1200 may be performed in a different order than shown in Figure 12, additional steps can be provided before, during, and after the steps, and / or some of the steps described can be replaced or eliminated in other aspects. One or more of steps of the method 1200 can be carried by one or more devices and / or systems described herein, such as components of the intraluminal imaging system 100 and / or processor circuit 250.

[0079] At step 1210, a first frame and second frame of ultrasound data are received. For example, the first frame and the second frame described above with respect to Figures 3B and 4B, respectively. Both the first frame and second frame may comprise ultrasound data in the form of radial scan lines, each scan line generated from the echoes received at the associated aperture.

[0080] Method 1200 includes two techniques / sub-methods of combining and scan converting the first and second frames received in step 1210. The first technique / sub-method includes steps 1220 and 1230, and the second technique / sub-method includes steps 1225 and 1235. Generally,2024PF00440the two techniques / sub-methods are distinguished by whether the frames are scan converted first or combined first, respectively.

[0081] At step 1220, the first frame and second frame are scan converted. For example, scan conversion as shown in Figure 9 and described above may be applied to the first frame (e.g., the frame described above with respect to Figure 3B) and the second frame (e.g., the frame described above with respect to Figure 4B).

[0082] At step 1230, the scan-converted first and second frame of step 1220 are combined. The scan-converted frames may be combined using any of the techniques described herein.

[0083] At step 1225, the first and second frame are combined (before scan converting). The first and second frame may be combined in their polar form using any of the techniques described herein.

[0084] At step 1235, the combined frame generated at step 1225 is scan-converted (e.g., as shown in Figure 9 and described above. In some aspects, the bilinear interpolation used for scan conversion may further incorporate weightings based on the expected difference between beam profiles as shown in Figure 10 and described above. In some aspects, a processor scan converting a combined frame or an individual frame may concurrently apply weightings as described herein, e.g., based on expected receive beam intensity shown in Figure 8 and described above.

[0085] It is noted that flow 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, 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. 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.

[0086] Figure 13 is a flow diagram for combining ultrasound data from a first and second aperture, according to aspects of the present disclosure. It is understood that the steps of method 1300 may be performed in a different order than shown in Figure 13, additional steps can be provided before, during, and after the steps, and / or some of the steps described can be replaced or eliminated in other aspects. One or more of steps of the method 1300 can be carried by one or2024PF00440more devices and / or systems described herein, such as components of the intraluminal imaging system 100 and / or processor circuit 250.

[0087] At step 1310, first ultrasound data is generated, where the first ultrasound data is associated with first echoes received at a first aperture of the circumferential array (e.g., transducer array 124). First ultrasound data may be the radial scan line generated from echoes received at the first odd aperture centered on transducer element 124(i) as shown in Figure 3B and described above, as well as other odd apertures, as well as other even apertures (centered on odd transducer elements).

[0088] At step 1320, second ultrasound data is generated, where the second ultrasound data is associated with second echoes received at a second aperture of the circumferential array (e.g., transducer array 124). Second ultrasound data may be the radial scan line generated from echoes received at the first even aperture centered on transducer element 124(2) as shown in Figure 4B and described above, as well as other even apertures (centered on even transducer elements).

[0089] At step 1330, the first ultrasound data and second ultrasound may be combined to generate combined ultrasound data. First ultrasound data and second ultrasound data may be combined using any of the techniques described herein, e.g., as shown in Figures 8-10 and described above. As another example, the first ultrasound data and second ultrasound data may be added together using weights determined by the difference between the average flow amplitudes between a first frame and second frame comprising the first ultrasound data and second ultrasound data, respectively.

[0090] Step 1330 may be broken up into several separate sequential processing steps. For example, the first ultrasound data and second ultrasound data may be separately weighted based on expected beam profiles for their respective apertures. Next, the weighted first ultrasound data and weighted second ultrasound data may each be scan converted. And finally, the scan-converted weighted first ultrasound data and scan-converted weighted second ultrasound data may be combined using weightings determined by the difference between the expected receive beam profile intensities of their respective apertures at each pixel location.

[0091] At step 1340, an ultrasound image is generated from the combined ultrasound data. For example, the combined ultrasound data may be scan converted into a rectangular pixel array which is displayed to a user. In some aspects, a processor may combine the ultrasound data before generating an ultrasound image. Alternatively, in some aspects, the processor may2024PF00440concurrently combine ultrasound data and generate an ultrasound image as a single concurrent process. The processor outputs the ultrasound image to a display in communication with the processor.

[0092] It is noted that flow 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, 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. 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.

[0093] 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.

[0094] 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.2024PF00440

[0095] In one general aspect, the present disclosure is directed to a system an intravascular ultrasound (IVUS) catheter that 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 a processor configured for communication with the circumferential array, where the processor is configured to: generate first ultrasound data associated with first echoes received at a first aperture of the circumferential array; generate second ultrasound data associated with second echoes received at a second aperture of the circumferential array, where the second echoes are received after the first echoes; combine the first ultrasound data and second ultrasound data to generate combined ultrasound data; and generate an ultrasound image from the combined ultrasound data, where the first aperture and second aperture are associated with different locations on the circumferential array.

[0096] In some aspects, implementations may include one or more of the following features. The system where the first ultrasound data is associated with a first frame and the second ultrasound data is associated with a second frame. To combine the first ultrasound data and second ultrasound data, the processor is configured to equally weight the first ultrasound data and the second ultrasound data. To combine the first ultrasound data and second ultrasound data, the processor is configured to weight the second ultrasound data differently than the first ultrasound data. To combine the first ultrasound data and second ultrasound data, the processor is configured to weight the first ultrasound data and second ultrasound data based on a first average flow amplitude determined from the first ultrasound data and a second mean or median flow amplitude determined from second ultrasound data. To generate the ultrasound image, the processor is configured to: apply scan conversion to the combined ultrasound data. To combine the first ultrasound data and second ultrasound data, the processor is configured to: apply a first plurality of weights to first ultrasound data to generate weighted first ultrasound data based on a first expected receive beam profile associated with the first aperture; and apply a second plurality of weights to second ultrasound data to generate weighted second ultrasound data based on a second expected receive beam profile associated with the first aperture. To combine the first ultrasound data and second ultrasound data, the processor is configured to: apply scan conversion to the weighted first ultrasound data to generate cartesian first ultrasound data; and apply scan2024PF00440conversion to the weighted second ultrasound data to generate cartesian second ultrasound data. To combine the first ultrasound data and second ultrasound data, the processor is configured to: combine the cartesian first ultrasound data and the cartesian second ultrasound data to generate combined ultrasound data based on a plurality of differences between the first expected receive beam profile and the second expected receive beam profile. The first echoes are representative of a first position along the blood vessel and the second echoes are representative of a second position different from the first position along the blood vessel. The first position and second position are associated with the location of the IVUS catheter during an IVUS pullback procedure through the blood vessel. The one or more processors is configured to: generate third ultrasound data associated with third echoes received at a third aperture of the circumferential array; and combine the first ultrasound data, the second ultrasound data, and the third ultrasound data to generate the combined ultrasound data, and where the first aperture, second aperture, and third aperture are associated with different locations on the circumferential array. A first receive beam profile is associated with the first aperture and a second receive beam profile is associated with the second aperture, and where the first receive beam profile and the second receive beam profile overlap in a circumferential direction. The first receive beam profile and the second receive beam profile overlap in a longitudinal direction. To combine the first ultrasound data and second ultrasound data to generate combined ultrasound data, the processor is configured to apply a plurality of weights to the first ultrasound data and the second ultrasound data.

[0097] In one general aspect, the present disclosure is directed to a method. The method also includes receiving, at a circumferential array of acoustic elements of an intravascular ultrasound (IVUS) catheter, first echoes at a first aperture and second echoes at a second aperture, where the first aperture and second aperture are associated with different locations on the circumferential array. The method also includes generating, with one or more processors in communication with the circumferential array, first ultrasound data associated with first echoes. The method also includes generating, with the one or more processors, second ultrasound data associated with second, where the second echoes are received after the first echoes. The method also includes combining, with the one or more processors, the first ultrasound data and second ultrasound data to generate combined ultrasound data. The method also includes generating, with the one or more processors, an ultrasound image from the combined ultrasound data.2024PF00440

[0098] 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.

[0099] 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. 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 to execute the method in real time or near-real time as described herein.

[0100] 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.

[0101] 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 word2024PF00440“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.

[0102] The above specification, examples and data provide a complete description of the structure and use of exemplary instances of the IVUS imaging system 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.

[0103] 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.

[0104] Additional embodiments (clauses):Clause 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; anda 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; anda processor configured for communication with the circumferential array, wherein the processor is configured to:generate first ultrasound data associated with first echoes received at a first aperture of the circumferential array;generate second ultrasound data associated with second echoes received at a second aperture of the circumferential array, wherein the second echoes are received after the first echoes; combine the first ultrasound data and second ultrasound data to generate combined ultrasound data; andgenerate an ultrasound image from the combined ultrasound data,2024PF00440wherein the first aperture and second aperture are associated with different locations on the circumferential array.Clause 2. The system of clause 1, wherein the first ultrasound data is associated with a first frame and the second ultrasound data is associated with a second frame.Clause 3. The system of clause 1, wherein, to combine the first ultrasound data and second ultrasound data, the processor is configured to equally weight the first ultrasound data and the second ultrasound data.Clause 4. The system of clause 1, wherein, to combine the first ultrasound data and second ultrasound data, the processor is configured to weight the second ultrasound data differently than the first ultrasound data.Clause 5. The system of clause 1, wherein, to combine the first ultrasound data and second ultrasound data, the processor is configured to weight the first ultrasound data and second ultrasound data based on a first average flow amplitude determined from the first ultrasound data and a second mean or median flow amplitude determined from second ultrasound data.Clause 6. The system of clause 5, wherein, to generate the ultrasound image, the processor is configured to:apply scan conversion to the combined ultrasound data.Clause 7. The system of clause 1, wherein, to combine the first ultrasound data and second ultrasound data, the processor is configured to:apply a first plurality of weights to first ultrasound data to generate weighted first ultrasound data based on a first expected receive beam profile associated with the first aperture; andapply a second plurality of weights to second ultrasound data to generate weighted second ultrasound data based on a second expected receive beam profile associated with the first aperture.2024PF00440Clause 8. The system of clause 7, wherein, to combine the first ultrasound data and second ultrasound data, the processor is configured to:apply scan conversion to the weighted first ultrasound data to generate cartesian first ultrasound data; andapply scan conversion to the weighted second ultrasound data to generate cartesian second ultrasound data.Clause 9. The system of clause 8, wherein, to combine the first ultrasound data and second ultrasound data, the processor is configured to:combine the cartesian first ultrasound data and the cartesian second ultrasound data to generate combined ultrasound data based on a plurality of differences between the first expected receive beam profile and the second expected receive beam profile.Clause 10. The system of clause 1, wherein the first echoes are representative of a first position along the blood vessel and the second echoes are representative of a second position different from the first position along the blood vessel.Clause 11. The system of clause 10, wherein the first position and second position are associated with the location of the IVUS catheter during an IVUS pullback procedure through the blood vessel.Clause 12. The system of clause 1,wherein the one or more processors is configured to:generate third ultrasound data associated with third echoes received at a third aperture of the circumferential array; andcombine the first ultrasound data, the second ultrasound data, and the third ultrasound data to generate the combined ultrasound data, andwherein the first aperture, second aperture, and third aperture are associated with different locations on the circumferential array.2024PF00440Clause 13. The system of clause 1,wherein a first receive beam profile is associated with the first aperture and a second receive beam profile is associated with the second aperture, andwherein the first receive beam profile and the second receive beam profile overlap in a circumferential direction.Clause 14. The system of clause 13, wherein the first receive beam profile and the second receive beam profile overlap in a longitudinal direction.Clause 15. The system of clause 1, wherein, to combine the first ultrasound data and second ultrasound data to generate combined ultrasound data, the processor is configured to apply a plurality of weights to the first ultrasound data and the second ultrasound data.Clause 16. A method, comprising:receiving, at a circumferential array of acoustic elements of an intravascular ultrasound (IVUS) catheter, first echoes at a first aperture and second echoes at a second aperture, wherein the first aperture and second aperture are associated with different locations on the circumferential array; generating, with one or more processors in communication with the circumferential array, first ultrasound data associated with first echoes;generating, with the one or more processors, second ultrasound data associated with second, wherein the second echoes are received after the first echoes;combining, with the one or more processors, the first ultrasound data and second ultrasound data to generate combined ultrasound data; andgenerating, with the one or more processors, an ultrasound image from the combined ultrasound data.Clause 17. The method of claim 16 wherein the method is for controlling a system of any one of clauses 1 to 15.

Claims

2024PF00440CLAIMSWhat is claimed is:

1. A system, comprising:a processor configured for communication with 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 wherein the circumferential array is comprised in an intravascular ultrasound (IVUS) catheter, the catheter further comprising a flexible elongate member configured to be positioned within a blood vessel of a patient, wherein the processor is configured to:generate first ultrasound data associated with first echoes received at a first aperture of the circumferential array;generate second ultrasound data associated with second echoes received at a second aperture of the circumferential array, wherein the second echoes are received after the first echoes;combine the first ultrasound data and second ultrasound data to generate combined ultrasound data; andgenerate an ultrasound image from the combined ultrasound data, wherein the first aperture and second aperture are associated with different locations on the circumferential array.

2. The system of claim 1, wherein the first ultrasound data is associated with a first frame and the second ultrasound data is associated with a second frame.

3. The system of claim 1 or 2, wherein, to combine the first ultrasound data and second ultrasound data, the processor is configured to equally weight the first ultrasound data and the second ultrasound data.2024PF004404. The system of claim 1 or 2, wherein, to combine the first ultrasound data and second ultrasound data, the processor is configured to weight the second ultrasound data differently than the first ultrasound data.

5. The system of any one of claims 1 to 4, wherein, to combine the first ultrasound data and second ultrasound data, the processor is configured to weight the first ultrasound data and second ultrasound data based on a first average blood flow amplitude determined from the first ultrasound data and a second mean or median blood flow amplitude determined from second ultrasound data.

6. The system of any one of claims 1 to 5, wherein, to generate the ultrasound image, the processor is configured to:apply scan conversion to the combined ultrasound data.

7. The system of any one of claims 1 to 6, wherein, to combine the first ultrasound data and second ultrasound data, the processor is configured to:apply a first plurality of weights to first ultrasound data to generate weighted first ultrasound data based on a first expected receive beam profile associated with the first aperture; andapply a second plurality of weights to second ultrasound data to generate weighted second ultrasound data based on a second expected receive beam profile associated with the first aperture.

8. The system of any one of claims 1 to 7, wherein, to combine the first ultrasound data and second ultrasound data, the processor is configured to:apply scan conversion to the weighted first ultrasound data to generate cartesian first ultrasound data; andapply scan conversion to the weighted second ultrasound data to generate cartesian second ultrasound data.2024PF004409. The system of claim 8, wherein, to combine the first ultrasound data and second ultrasound data, the processor is configured to:combine the cartesian first ultrasound data and the cartesian second ultrasound data to generate combined ultrasound data based on a plurality of differences between the first expected receive beam profile and the second expected receive beam profile.

10. The system of any one of claims 1 to 9, wherein the first echoes are representative of a first position along the blood vessel and the second echoes are representative of a second position different from the first position along the blood vessel, optionally wherein the first position and second position are further associated with the location of the intravascular (IVUS) catheter during an IVUS pullback procedure through the blood vessel.

11. The system of any one of claims 1 to 10,wherein a first receive beam profile is associated with the first aperture and a second receive beam profile is associated with the second aperture,wherein the first receive beam profile and the second receive beam profile overlap in a circumferential direction, andoptionally, wherein the first receive beam profile and the second receive beam profile overlap in a longitudinal direction.

12. The system of any one of claims 1 to 11, wherein, to combine the first ultrasound data and second ultrasound data to generate combined ultrasound data, the processor is configured to apply a plurality of weights to the first ultrasound data and the second ultrasound data.

13. The system of any one of the claims 1 to 12, comprising the intravascular ultrasound (IVUS) catheter.

14. A method, comprising:receiving,;generating, with one or more processors in communication with a circumferential array of acoustic elements of an intravascular ultrasound (IVUS) catheter, first ultrasound data2024PF00440associated with first echoes, the first echoes received at a first aperture of the circumferential array of acoustic elements of the intravascular ultrasound (IVUS) catheter, first echoes at a first aperture and second echoes at a second aperture;generating, with the one or more processors wherein the first aperture and second aperture are associated with different locations on the circumferential array, second ultrasound data associated with second echoes received at a second aperture of the circumferential array of acoustic elements of the intravascular ultrasound (IVUS) catheter, wherein the second echoes are received after the first echoes and wherein the first aperture and second aperture are associated with different locations on the circumferential array;combining, with the one or more processors, the first ultrasound data and second ultrasound data to generate combined ultrasound data;generating, with the one or more processors, an ultrasound image from the combined ultrasound data; andoptionally, outputting, with a display device in communication with the one or more processors, the combined ultrasound data.

15. A computer program comprising computer readable instructions which, when run on one or more processors, cause the method of claim 14 to be performed.

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