ULTRASOUND-BASED GUIDANCE FOR PHOTOACOUSTIC MEASUREMENTS AND ASSOCIATED DEVICES, SYSTEMS, AND METHODS

Systems, devices, and methods for performing photoacoustic measurements using ultrasound-based guidance are provided. In one embodiment, an imaging system includes: an ultrasound imaging probe comprising an ultrasound transducer array, a processor circuit in communication with the ultrasound imaging probe, and a light source configured to emit light. The processor circuit receives first ultrasound data representative of an anatomical feature within a field of view, identifies a location of the anatomical feature within the field of view, and performs a photoacoustic measurement using the identified location of the anatomical feature. Performing the photoacoustic measurement includes: controlling the light source to emit light into the field of view and processing second ultrasound data representative of photoacoustic energy generated in the anatomical feature by the light source. The processor circuit then outputs a graphical representation of the photoacoustic measurement to a display.

TECHNICAL FIELD

The present disclosure relates generally to the acquisition and processing of ultrasound images and photoacoustic data. In particular, the present disclosure is directed to systems and methods for guiding a photoacoustic measurement procedure using ultrasound image data.

BACKGROUND

Ultrasound imaging is frequently used to obtain images of internal anatomical structures of a patient. Ultrasound systems typically comprise an ultrasound transducer probe that includes a transducer array coupled to a probe housing. The transducer array is activated to vibrate at ultrasonic frequencies to transmit ultrasonic energy into the patient's anatomy, and then receive ultrasonic echoes reflected or backscattered by the patient's anatomy to create an image. Such transducer arrays may include various layers, including some with piezoelectric materials, which vibrate in response to an applied voltage to produce the desired pressure waves. These transducers may be used to successively transmit and receive several ultrasonic pressure waves through the various tissues of the body. The various ultrasonic responses may be further processed by an ultrasonic imaging system to display the various structures and tissues of the body.

Of recent interest is a form of ultrasound imaging that involves inducing acoustic vibrations in an anatomical feature using pulsed light waves, receiving or measuring the acoustic vibrations using an ultrasound transducer array, and computing a physiological measurement based on the received acoustic vibrations. This form of ultrasound imaging is referred to as photoacoustic imaging, and may beneficially provide for obtaining physiological measurements in a non-invasive manner. Photoacoustic imaging may be used to determine a variety of physiological parameters, including oxygen saturation of the blood vessels leading into an organ, hemoglobin concentration, and other parameters. For example, photoacoustic imaging may be used to measure the oxygen consumption of an organ of the body, such as the brain. Obtaining a photoacoustic measurement involves illuminating an anatomical feature of interest, such as a blood vessel, with sufficient intensity to induce acoustic vibrations that can be detected by the ultrasound transducer.

One of the central challenges in acquiring accurate photoacoustic measurements from human tissue is positioning the photoacoustic light source relative to the tissue volume of interest such that adequate acoustic signal can be received to make measurements. In that regard, the anatomical features of interest (e.g., blood vessel) may not be visible through the patient's skin such that a sonographer can properly place the light source. Another challenge with quantitative photoacoustic methods is selecting a photoacoustic waveform or region of interest in a photoacoustic image for analysis. Since many tissues absorb light and emit a photoacoustic signal, it can be difficult to assess which signal or portion of the signal came from the tissue region of interest.

SUMMARY

The present disclosure describes systems, devices, and methods for performing photoacoustic measurements using ultrasound-based guidance. In one embodiment, an ultrasound-based photoacoustic measurement system includes an ultrasound transducer array positioned with respect to a photoacoustic light source and configured to obtain ultrasound data representative of an anatomical feature, such as a vessel. A processor circuit or processing system identifies a location of the anatomical feature based on the ultrasound data, and uses the identified location to guide the photoacoustic measurement. In some aspects, guidance may be automated, and may be provided in the form of control signals, user instructions, and/or image processing parameters. For example, the processor circuit may use a location of a vessel identified from ultrasound image data to set a spatial or temporal region of interest for processing photoacoustic signals. In another example, the processor circuit may provide instructions to a user or a control signal to an actuator to adjust a position and/or orientation of the light source of the photoacoustic subsystem to better illuminate the vessel, thereby increasing the strength of the resulting photoacoustic signals.

According to one embodiment of the present application, an imaging system includes: an ultrasound imaging probe comprising an ultrasound transducer array configured to emit ultrasound energy toward an anatomical feature within a field of view of the ultrasound transducer array; and a processor circuit in communication with the ultrasound imaging probe and a light source configured to emit light at an orientation with respect to the field of view. The processor circuit is configured to: receive first ultrasound data obtained by the ultrasound imaging probe, wherein the first ultrasound data is representative of the anatomical feature within the field of view; identify, by image processing of the first ultrasound data, a location of the anatomical feature within the field of view; and perform a photoacoustic measurement using the identified location of the anatomical feature within the field of view. Performing the photoacoustic measurement includes: controlling the light source to emit the light into the field of view; and processing second ultrasound data obtained by the ultrasound imaging probe, wherein the second ultrasound data is representative of photoacoustic energy generated in the anatomical feature by the light source. The processor circuit is further configured to output a graphical representation of the photoacoustic measurement to a display in communication with the processor circuit.

In some embodiments, the first ultrasound data comprises at least one of B-mode data or Doppler data. In some embodiments, the processor circuit is configured to identify the location of the anatomical feature using the B-mode data and the Doppler data. In some embodiments, the processor circuit is configured to: determine, based on the identified location of the anatomical feature, a gate for processing the second ultrasound data; and perform the photoacoustic measurement using the gate. In some embodiments, the gate comprises a temporal gate. In some embodiments, the gate comprises a spatial gate. In some embodiments, the first ultrasound data comprises Doppler data, and the processor circuit is configured to: determine a region of flow in the anatomical feature based on the Doppler data; and determine the spatial gate based on the region of flow. In some embodiments, the imaging system further includes an actuator coupled to the light source and configured to adjust at least one of a position or an orientation of the light source relative to the field of view of the ultrasound transducer array. In some embodiments, the actuator is communicatively coupled to the processor circuit. In some embodiments, the processor circuit is configured to control the actuator, based on the identified location of the anatomical feature, to adjust the at least one of the position or orientation of the light source relative to the field of view of the ultrasound transducer array. In some embodiments, the processor circuit is configured to control the actuator, based on the identified location of the anatomical feature, to advance the light source toward the anatomical feature such that tissue between the anatomical feature and the light source is deformed.

In some embodiments, the light source comprises a plurality of light elements positioned at different locations with respect to the ultrasound transducer array. In some embodiments, the processor circuit is configured to select, based on the identified location of the anatomical feature, one or more light elements of the plurality of light elements to perform the photoacoustic measurement. In some embodiments, the processor circuit is configured to: generate, using the identified location of the anatomical feature, a user instruction to reposition and least one of the light source or the ultrasound imaging probe; and output the user instruction to the display. In some embodiments, the processor circuit is configured to: generate a first image of the anatomical feature using the first ultrasound data; generate a second image of the anatomical feature using the second ultrasound data; and output the co-registered first and second images to the display.

In some embodiments, the processor circuit is configured to receive the first ultrasound data and the second ultrasound data at a same time. In some embodiments, the processor circuit is configured to receive the first ultrasound data and the second ultrasound data at different times in an interleaved fashion. In some embodiments, the imaging system further includes the light source. In some embodiments, the light source is coupled to the ultrasound imaging probe.

According to another embodiment of the present disclosure, a method for ultrasound imaging includes: receiving, by a processor circuit, first ultrasound data obtained by an ultrasound imaging probe comprising an ultrasound transducer array configured to emit ultrasound energy toward an anatomical feature within a field of view of the ultrasound transducer array, wherein the first ultrasound data is representative of the anatomical feature within the field of view; identifying, by image processing of the first ultrasound data, a location of the anatomical feature within the field of view; and performing a photoacoustic measurement using the identified location of the anatomical feature within the field of view. Performing the photoacoustic measurement includes: controlling a light source in communication with the processor circuit to emit light into the field of view at an orientation with respect to the field of view; and processing second ultrasound data obtained by the ultrasound imaging probe, wherein the second ultrasound data is representative of photoacoustic energy generated in the anatomical feature by the light source. The method further includes outputting a graphical representation of the photoacoustic measurement to a display in communication with the processor circuit.

DETAILED DESCRIPTION

InFIG. 1, an ultrasound-based photoacoustic measurement system100according to embodiments of the present disclosure is shown in block diagram form. In some aspects, the photoacoustic measurement system100includes devices and/or subsystems for ultrasound imaging, such as an ultrasound probe10having a transducer array12comprising a plurality of ultrasound transducer elements or acoustic elements. In some instances, the array12may include any number of acoustic elements. For example, the array12can include between 1 acoustic element and 100000 acoustic elements, including values such as 2 acoustic elements, 4 acoustic elements, 36 acoustic elements, 64 acoustic elements, 128 acoustic elements, 300 acoustic elements, 812 acoustic elements, 3000 acoustic elements, 9000 acoustic elements, 30,000 acoustic elements, 65,000 acoustic elements, and/or other values both larger and smaller. In some instances, the acoustic elements of the array12may be arranged in any suitable configuration, such as a linear array, a planar array, a curved array, a curvilinear array, a circumferential array, an annular array, a phased array, a matrix array, a one-dimensional (1D) array, a 1.X dimensional array (e.g., a 1.5D array), or a two-dimensional (2D) array. The array of acoustic elements (e.g., one or more rows, one or more columns, and/or one or more orientations) can be uniformly or independently controlled and activated. The array12can be configured to obtain one-dimensional, two-dimensional, and/or three-dimensional images of patient anatomy. In some embodiments, the ultrasound probe10includes a single transducer element, such as a mechanically-scanned transducer element.

Referring again toFIG. 1, the acoustic elements of the array12may comprise one or more piezoelectric/piezoresistive elements, lead zirconate titanate (PZT), piezoelectric micromachined ultrasound transducer (PMUT) elements, capacitive micromachined ultrasound transducer (CMUT) elements, and/or any other suitable type of acoustic elements. The one or more acoustic elements of the array12are in communication with (e.g., electrically coupled to) electronic circuitry14. In some embodiments, such as the embodiment ofFIG. 1, the electronic circuitry14can comprise a microbeamformer (μBF). In other embodiments, the electronic circuitry comprises a multiplexer circuit (MUX). The electronic circuitry14is located in the probe10and communicatively coupled to the transducer array12. In some embodiments, one or more components of the electronic circuitry14can be positioned in the probe10. In some embodiments, one or more components of the electronic circuitry14, can be positioned in a computing device or processing system28. The computing device28may be or include a processor, such as one or more processors in communication with a memory. As described further below, the computing device28may include a processor circuit as illustrated inFIG. 13. In some aspects, some components of the electronic circuitry14are positioned in the probe10and other components of the electronic circuitry14are positioned in the computing device28. The electronic circuitry14may comprise one or more electrical switches, transistors, programmable logic devices, or other electronic components configured to combine and/or continuously switch between a plurality of inputs to transmit signals from each of the plurality of inputs across one or more common communication channels. The electronic circuitry14may be coupled to elements of the array12by a plurality of communication channels. The electronic circuitry14is coupled to a cable16, which transmits signals including ultrasound imaging data to the computing device28.

In the computing device28, the signals are digitized and coupled to channels of a system beamformer22, which appropriately delays each signal. The delayed signals are then combined to form a coherent steered and focused receive beam. System beamformers may comprise electronic hardware components, hardware controlled by software, or a microprocessor executing beamforming algorithms. In that regard, the beamformer22may be referenced as electronic circuitry. In some embodiments, the beamformer22can be a system beamformer, such as the system beamformer22ofFIG. 1, or it may be a beamformer implemented by circuitry within the ultrasound probe10. In some embodiments, the system beamformer22works in conjunction with a microbeamformer (e.g., electronic circuitry14) disposed within the probe10. The beamformer22can be an analog beamformer in some embodiments, or a digital beamformer in some embodiments. In the case of a digital beamformer, the system includes anaolog-to-digital converters which convert analog signals from the array12into sampled digital echo data. The beamformer22generally will include one or more microprocessors, shift registers, and or digital or analog memories to process the echo data into coherent echo signal data. Delays are effected using various techniques such as by the time of sampling of received signals, the write/read interval of data temporarily stored in memory, or by the length or clock rate of a shift register as described in U.S. Pat. No. 4,173,007 to McKeighen et al., the entirety of which is hereby incorporated by reference herein. Additionally, in some embodiments, the beamformer can apply appropriate weight to each of the signals generated by the array12. The beamformed signals from the image field are processed by a signal and image processor24to produce 2D or 3D images for display on an image display30. The signal and image processor24may comprise electronic hardware components, hardware controlled by software, or a microprocessor executing image processing algorithms. It generally will also include specialized hardware or software which processes received echo data into image data for images of a desired display format such as a scan converter. In some embodiments, beamforming functions can be divided between different beamforming components. For example, in some embodiments, the system100can include a microbeamformer located within the probe10and in communication with the system beamformer22. The microbeamformer may perform preliminary beamforming and/or signal processing that can reduce the number of communication channels required to transmit the receive signals to the computing device28.

Control of ultrasound system parameters such as scanning mode (e.g., B-mode, Doppler, M-mode), probe selection, beam steering and focusing, and signal and image processing is done under control of a system controller26which is coupled to various modules of the system100. The system controller26may be formed by application specific integrated circuits (ASICs) or microprocessor circuitry and software data storage devices such as RAMs, ROMs, or disk drives. In the case of the probe10, some of this control information may be provided to the electronic circuitry14from the computing device28over the cable16, conditioning the electronic circuitry14for operation of the array as required for the particular scanning procedure. The user inputs these operating parameters with a user interface device20.

In some embodiments, the image processor24is configured to generate images of different modes to be further analyzed or output to the display30. For example, in some embodiments, the image processor can be configured to compile a B-mode image, such as a live B-mode image, of an anatomy of the patient. In other embodiments, the image processor24is configured to generate or compile a Doppler image, such as a color Doppler or Power Doppler image. A doppler image can be described as an image showing moving portions of the imaged anatomy.

It will be understood that the computing device28may comprise hardware circuitry, such as a computer processor, application-specific integrated circuit (ASIC), field-programmable gate array (FPGA), capacitors, resistors, and/or other electronic devices, software, or a combination of hardware and software. In some embodiments, the computing device28is a single computing device. In other embodiments, the computing device28comprises separate computer devices in communication with one another.

Further, it will be understood that although the present disclosure refers to synthetic aperture external ultrasound imaging using an external ultrasound probe, one or more aspects of the present disclosure can be implemented in any suitable ultrasound imaging probe or system, including external ultrasound probes and intraluminal ultrasound probes. For example, aspects of the present disclosure can be implemented in ultrasound imaging systems using a mechanically-scanned external ultrasound imaging probe, an intracardiac (ICE) echocardiography catheter and/or a transesophageal echocardiography (TEE) probe, a rotational intravascular ultrasound (IVUS) imaging catheter, a phased-array IVUS imaging catheter, a transthoracic echocardiography (TTE) imaging device, or any other suitable type of ultrasound imaging device.

In some aspects, the system100may be used to obtain photoacoustic measurements and/or images. In that regard, the system100further comprises a photoacoustic subsystem or subassembly that includes a light source40and an actuator42mechanically coupled to the light source40. The light source is configured to emit a beam52of light toward an anatomical feature5, which may comprise a blood vessel. The beam52may be pulsed to induce acoustic (e.g., ultrasonic) vibrations the anatomical feature5. In some embodiments, the probe10, light source40, and actuator42form an integral unit coupled to and/or positioned within a housing. In some embodiments, the light source40and the actuator42are coupled to the probe10via an attachment such that the light source40and/or the actuator42may be coupled to an existing commercially-available probe. In that regard, in some aspects, the light source40and the actuator42may be part of a photoacoustic subsystem of the system100. The light source40is maintained at a position and orientation relative to the transducer array12. In some aspects, the position and orientation of the light source40may be referred to as a pose. In that regard, the path of the beam52of light emitted by the light source40may be changed by adjusting the pose of the light source40.

In the illustrated embodiment, the light source40and actuator42are communicatively coupled to the computing device28via a cable18. In some embodiments, the light source40and the actuator42are coupled to the computing device28via separate cables. In some aspects, the controller26may be configured to control the probe10, actuator42, and light source40. In some embodiments, the controller26comprises separate controller units dedicated to each of the probe10, the light source40, and the actuator42. Further, in the illustrated embodiment, the actuator42includes a feedback sensor44configured to detect or monitor actuation of the light source40by the actuator42. For example, in some embodiments, the feedback sensor44is configured to detect a position and/or orientation of the light source40relative to the ultrasound transducer array12. In some embodiments, the feedback sensor44is configured to detect a position and/or orientation of the light source40relative to the patient (e.g., the anatomical feature5, the skin, etc.) In some embodiments, the feedback sensor44is configured to detect a force applied to the patient's skin by the light source40, and/or to detect an amount of deformation of the patient's skin or anatomy by the light source40. Accordingly, the feedback sensor44may be used by the controller26in controlling the actuator42using a feedback loop (e.g., a proportional-integral-derivative (PID) loop). In some embodiments, the feedback sensor is configured to measure displacement of the light source, force experienced by the moving subsystem, and/or displacement or collapse of the blood vessel under interrogation. In some embodiments, the processor circuit may utilize that information to control the amount of movement of the actuator and/or light source, and to adapt the photoacoustic signal processing based on the information from one of the above measurements.

The system100is configured to perform a photoacoustic measurement procedure to determine one or more physiological characteristics of an anatomical structure, such as a blood vessel. In an exemplary embodiment, the photoacoustic measurement procedure includes activating the light source40to emit the beam52of light into the body of a patient to induce photoacoustic vibrations in the anatomical feature5. The vibrations cause acoustic waves54to propagate through the tissue to the transducer array12, which receives the acoustic waves54and converts them into an electrical signal. Physiological characteristics of the anatomical feature5, such as oxygen concentration or hemoglobin concentration, can be inferred from the magnitude and/or frequency composition of the received acoustic signals. In an exemplary embodiment, the anatomical feature5comprises a blood vessel, such as a vein or artery. Photoacoustic measurements can be used to determine oxygen concentration of the blood flowing into and/or out of an organ of the body, such as the brain, to determine the oxygen consumption of the organ.

As described above, beams of light52from the light source40attenuate exponentially in the tissue. Accordingly, it is desirable to not only position and orient the light source40such that the anatomical feature is within the path of the beam52, but also to position and orient the light source40to reduce or minimize the distance between the light source40and the anatomical feature. However, in some instances, placing the light source40to obtain a reliable photoacoustic measurement can be a difficult and imprecise process. For example, many blood vessels are not externally visible. Further, even when the anatomical feature5is within the path of the beam52and reasonably close to the light source40, processing the photoacoustic data may involve significant amounts of error, as the light source40may induce photoacoustic vibrations in the tissue and other features within the tissue that are not of interest for the photoacoustic measurement. Accordingly, the present disclosure provides systems, methods, and devices for leveraging information obtained using ultrasound imaging techniques (e.g., B-mode image data and/or Doppler image data) to guide photoacoustic measurement procedures.

FIG. 13is a schematic diagram of a processor circuit150, according to embodiments of the present disclosure. The processor circuit150may be implemented in the computing device28, the signal and image processor24, the controller26, and/or the probe10ofFIG. 1. As shown, the processor circuit150may include a processor160, a memory164, and a communication module168. These elements may be in direct or indirect communication with each other, for example via one or more buses.

The processor160may include a central processing unit (CPU), a digital signal processor (DSP), an ASIC, a controller, an FPGA, another hardware device, a firmware device, or any combination thereof configured to perform the operations described herein. The processor160may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

The memory164may include a cache memory (e.g., a cache memory of the processor160), random access memory (RAM), magnetoresistive RAM (MRAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM), flash memory, solid state memory device, hard disk drives, other forms of volatile and non-volatile memory, or a combination of different types of memory. In an embodiment, the memory164includes a non-transitory computer-readable medium. The memory164may store instructions166. The instructions166may include instructions that, when executed by the processor160, cause the processor160to perform the operations described herein with reference to the processor28and/or the probe10(FIG. 1). Instructions166may also be referred to as code. The terms “instructions” and “code” should be interpreted broadly to include any type of computer-readable statement(s). For example, the terms “instructions” and “code” may refer to one or more programs, routines, sub-routines, functions, procedures, etc. “Instructions” and “code” may include a single computer-readable statement or many computer-readable statements.

The communication module168can include any electronic circuitry and/or logic circuitry to facilitate direct or indirect communication of data between the processor28, the probe10, and/or the display30. In that regard, the communication module168can be an input/output (I/O) device. In some instances, the communication module168facilitates direct or indirect communication between various elements of the processor circuit150and/or the processing system106(FIG. 1).

FIG. 2is a diagrammatic view of a photoacoustic measurement system200obtaining a photoacoustic measurement, according to aspects of the present disclosure. In that regard, the system200includes an ultrasound transducer array212comprising a plurality of ultrasound transducer elements configured to obtain ultrasound image data and/or photoacoustic data from the body of the patient. The system200further includes a light source240configured to emit a beam of light252toward a blood vessel5within the tissue215. InFIG. 2, the imaging plane or field of view of the ultrasound transducer array212is parallel with the longitudinal axis of the vessel5to obtain a longitudinal cross-sectional view of the vessel5. The light source240is shown slightly pressed into the skin surface211of the tissue215. As described further below, in some aspects, it may be advantageous to press the light source240into the tissue215by deforming the skin211of the patient to reduce the path length217between the light source240and the vessel5. For example, in some embodiments, the light source240is movable such that it can be pressed into the skin surface211by a displacement distance213to reduce the path length217between the light source240and the vessel5. In some embodiments, the system200further includes a feedback sensor configured to measure displacement of the moving subsystem, force experienced by the moving subsystem, and/or displacement or collapse of the blood vessel under interrogation. The processor circuit may be configured to utilize these measurements to adapt the photoacoustic signal processing.

FIG. 3shows the system200shown inFIG. 2with the ultrasound transducer array212positioned such that the imaging plane or field of view is perpendicular to the blood vessel5to obtain a radial cross-sectional view of the vessel5. In some aspects, the light source240may be considered optimally placed and oriented with respect to the vessel5to obtain a photoacoustic measurement in bothFIG. 2andFIG. 3. However, even when optimally placed, it may be desirable to identify specific regions or portions of a photoacoustic image corresponding to the vessel5to obtain a photoacoustic image. Since many tissues and anatomical structures within a given field of view of the ultrasound transducer absorb light and emit a photoacoustic signal, it can be difficult to assess which signals came from the tissue region of interest (e.g., the vessel5), and which signals came from tissues that are not of interest. Accordingly, the present disclosure provides for ultrasound-based guidance for identifying portions of photoacoustic signals and/or images to analyze for photoacoustic measurements. By using ultrasound images to localize the tissue region of interest, one or more gates can be determined for processing the photoacoustic image or signal, thereby focusing the photoacoustic measurement on the regions more likely to yield accurate photoacoustic measurements.

FIGS. 4A-5Bshow ultrasound images302,306and photoacoustic images304,308obtained using the system200shown inFIGS. 2 and 3. In that regard, the images302,304ofFIGS. 4A and 4Bare obtained according to configuration shown inFIG. 2in which the field of view of the ultrasound transducer array212is parallel to the vessel5.FIG. 4Ais a combined B-mode and Doppler image302obtained using the first field of view, andFIG. 4Bis a photoacoustic image304obtained using the first field of view. The images306,308ofFIGS. 5A and 5Bare obtained according to configuration shown inFIG. 3in which the field of view of the ultrasound transducer array212is perpendicular to the vessel5.FIG. 5Ais a combined B-mode and Doppler image306obtained using the second field of view, andFIG. 5Bis a photoacoustic image308obtained using the second field of view.

As shown inFIG. 4A, the combined image includes B-mode information representative of a vessel wall of the vessel310, and Doppler information representative of flowing blood within the vessel310. The B-mode information of the vessel wall is shown as the white outlines of the vessel310, and the Doppler information is shown as the patterned interior portion of the vessel310. In some embodiments, the Doppler information is used to localize coarse region of flow in the vessel initially. This coarse information could feed back to a beamforming unit to perform high resolution (e.g., line density, low F #) B-mode or harmonic imaging to determine much higher resolution echogenicity changes indicating the proximal vessel wall. By determining the boundaries of the vessel wall, a spatial gate320can be computed that corresponds to a detected location of the vessel310in the image. Using this gate320, the processor circuit analyzes the region of the photoacoustic image304within the gate320to more readily identify relevant portions of the photoacoustic image304of the vessel310, as shown inFIG. 4B. In some aspects, the gate320determined from the ultrasound image302may be used as a search region320in the corresponding photoacoustic image304. In some aspects, using the gate320obtained by the ultrasound data may improve the accuracy and/or efficiency of the photoacoustic measurement.

The gate320may be determined or computed to focus on a proximal region of the vessel310closer to the ultrasound transducer. In some aspects, the photoacoustic signals may be stronger in the portion of the vessel310that is closer to the ultrasound transducer. In other embodiments, the gate is determined or computed to include an entirety of the vessel310. While the gate320shown inFIGS. 4A-5Bis rectangular, it will be understood that the gate320may comprise other shapes, such as a polygonal shape, circular shape, elliptical shape, irregular shape, or any other suitable shape or combinations thereof. For example, in some embodiments, the shape of the gate320matches a determined shape of a vessel feature, such as the vessel310lumen or the vessel wall.

In some embodiments, the system200is configured to determine a temporal gate for the photoacoustic signals, rather than a spatial gate. In that regard,FIG. 6shows a temporal gate420determined using B-mode and/or Doppler image data of a vessel, as applied to a photoacoustic signal430. Similar to the spatial gate320shown inFIGS. 4A-5B, the temporal gate420may isolate a portion of the photoacoustic signal430used to obtain a photoacoustic measurement.

In some instances, it may be challenging to properly position and orient a light source of a photoacoustic measuring system to illuminate the vessel of interest. For example, the blood vessel may not be externally visible to the physician. Accordingly, the present disclosure provides for ultrasound-based guidance for photoacoustic light source placement. As described further below, an imaging system may use ultrasound image data (e.g., B-mode and/or Doppler data) of an anatomical feature, in addition to a known position and/or orientation of the light source relative to the ultrasound transducer array to adjust a position and/or orientation of the light source to direct more light to the anatomical feature.

In some embodiments, guidance is output by the system in the form of a user instruction to adjust a position of an ultrasound probe and/or light source. The user instruction may be output to a display, speaker, and/or other user interface device. In some embodiments, guidance is output as a computer command to an actuator configured to mechanically adjust a pose (i.e. position and/or orientation) of the light source relative to the ultrasound transducer array. For example, the actuator may comprise an electric motor, gears, rack and pinion, servo motor, hinge, and/or other mechanical components coupled to the light source and configured to adjust the pose of the light source in one or more degrees of freedom. In some embodiments, the actuator is controllable to by a processor circuit to automatically perform a motorized adjustment of the pose of the light source. In some embodiments, the actuator is manually controllable by a user to adjust the pose of the light source. Accordingly, in some embodiments, the light source is movable by the actuator in a manner so as to reduce the distance between a blood vessel and the light source. The actuator may allow for translation along the surface of the skin as well as the capability to deform the skin surface such that the light source is made to be closer to the vessel of interest. In other embodiments, the light source may include a plurality of light source elements (e.g., optical fibers or bundles of optical fibers) that can be selectively activated according to the instructions output by a guidance system.

FIG. 7Ais a diagrammatic view of a photoacoustic measurement system400, according to an embodiment of the present disclosure. The system400includes an ultrasound transducer array412configured to be positioned with respect to a patient to obtain ultrasound image data of the anatomy of a patient, including a vessel5and tissue415. The system400further includes a light source440co-located with the ultrasound transducer array and configured to illuminate the vessel5and/or tissue415. The system400further includes an actuator442or actuator assembly coupled to the light source440and configured to adjust a pose of the light source440(and therefore, a path of the beam452of light) relative to the ultrasound transducer array412.FIG. 7Bis an ultrasound image402representative of the vessel5and obtained by the ultrasound transducer array412as shown inFIG. 7A. Specifically,FIG. 7Bis a combined B-mode and Doppler image402of a radial cross-sectional view of the vessel5.FIG. 7Cis a photoacoustic image404obtained using the same field of view shown inFIG. 7Band with the light source440positioned relative to the ultrasound transducer array412and the vessel5as shown inFIG. 7A. Referring toFIG. 7B, the vessel5is depicted within the field of view of the transducer array412. By contrast, the vessel5is not shown in the photoacoustic image404ofFIG. 7Cbecause, although the vessel5is within the field of view of the transducer array412, the vessel5is not within the beam path452of the light source440. Accordingly, any photoacoustic energy generated by the vessel5is not detected by the ultrasound transducer array412.

FIG. 8Ais a diagrammatic view of the photoacoustic measurement system400shown inFIG. 7A, with the pose of the light source440adjusted relative to the transducer array412such that the beam452illuminates the vessel5.FIG. 8Bshows a combined B-mode/Doppler image406obtained with the transducer array412positioned as inFIG. 8A. In that regard, the image406ofFIG. 8Bis substantially the same as inFIG. 7Bbecause the transducer array412has not moved relative to the vessel5. However, the photoacoustic image408shown inFIG. 8Cnow shows the vessel5, as the light source is positioned such that a sufficient amount of the beam452illuminates the vessel5to perform a photoacoustic measurement. In some embodiments, the vessel5is shown in the same position in the ultrasound image406and the photoacoustic image408because the same field of view is used to obtain both images406,408. In other embodiments, the vessel5is shown in different locations and/or in different sizes in the respective images406,408. For example, different fields of view of the transducer array412may be used to obtain the ultrasound image406and the photoacoustic image408.

The actuator442shown inFIGS. 7A and 8Amay be in communication with a controller or processor circuit configured to generate control signals for the actuator442based on a location of the vessel5detected based on ultrasound image data. For example, the processor circuit may determine a location of the vessel5within the field of view by image processing the ultrasound image data. Based on the determined location and a known position and/or orientation of the light source440with respect to the field of view of the ultrasound transducer array412, the processor circuit computes a movement to position the light source440such that the beam452illuminates the vessel5. The processor circuit then generates a control signal to activate the actuator442to carry out the computed movement. In some embodiments, the actuator442comprises one or more of an electric motor, a servo motor, gears, a rack and pinion, pneumatic devices, springs, magnets, hinges, pistons, and/or any other suitable actuating mechanism controllable by the processor circuit to adjust the pose of the light source440. In some embodiments, the photoacoustic measurement system400does not include a controllable actuator, but includes a mechanical coupling assembly that can be manually adjusted by an operator to change the position and/or orientation of the light source440with respect to the ultrasound transducer array412.

As shown inFIGS. 9 and 10, in some embodiments, an ultrasound probe410may include a light source having a plurality of individual light elements444positioned at different locations with respect to the ultrasound transducer array. The light elements444can be selectively activated by the processor circuit based on the determined location of the vessel and the known position and/or orientation of the light elements444with respect to the field of view of the transducer array412. In some embodiments, the light elements444are co-located with the transducer array412on the probe410. For example, in the embodiment shown inFIG. 9, the light elements444are disposed around a periphery of the ultrasound transducer array412on a surface of the probe410. In the embodiment shown inFIG. 10, the light elements444are positioned within the transducer array412.

The light source440and/or light elements444may comprise, for example, one or more optical fibers, light-emitting diodes, lasers, incandescent light bulbs, fluorescent bulbs, or any other suitable type of light element. Further, the light source440may include lenses, mirrors, prisms, or other optical components configured to direct light to a location (e.g., a vessel) and/or to control characteristics of the light, such as frequency, bandwidth, focus, or other characteristics. In some embodiments, the light source may be configured to emit light having a frequency profile that includes multiple frequencies or frequency peaks. For example, the frequency profile may include frequencies associated with a photoacoustic response of blood and/or tissue. In some embodiments, the frequency profile includes one or more frequencies in the infrared (IR) and/or near-infrared (NIR) spectrum. In some embodiments, the frequency profile includes one or more frequencies between 500 nm and 1100 nm. In some embodiments, the frequency profile includes one or more frequencies or frequency peaks centered at approximately (i.e., +/−10%) 600 nm, 700 nm, 800 nm, 900 nm, and/or 1050 nm.

FIG. 11is a flow diagram illustrating a method500for performing a photoacoustic measurement using ultrasound-based guidance, according to an embodiment of the present disclosure. It will be understood that the method500may be performed using the devices and/or systems described above, such as the system100shown inFIG. 1, including the ultrasound probe10, the light source40, the actuator, the computing device28, and/or the display30. In step510, an ultrasound transducer array obtains first ultrasound data representative of an anatomical feature within a field of view of the ultrasound transducer array. In that regard, the first ultrasound data may be representative of a blood vessel. The first ultrasound data may be obtained when a user, such as a sonographer or physician, places the transducer array of an ultrasound probe against the skin of the patient proximate a vessel of interest to emit ultrasound energy toward the vessel. In some instances, the sonographer may desire to obtain photoacoustic images and/or measurements that can be used to determine oxygen consumption of a patient's organ, such as the patient's brain. Accordingly, the sonographer may place the ultrasound probe against the patient's neck at a location proximate a vessel leading into or away from the brain, such as a carotid artery, a vertebral artery, occipital artery, and/or any other suitable vessel.

In step520, the processor receives the first ultrasound data. The first ultrasound data may be used to generate B-mode and/or Doppler data (e.g., power Doppler, color Doppler, etc.). In that regard, in some embodiments, the first ultrasound data is obtained by interleaving B-mode image sequences and Doppler imaging sequences. In some embodiments, the ultrasound transducer array provides ultrasound signals or data, and a processor circuit generates B-mode image data and Doppler image data based on the same ultrasound signals. In some embodiments, only B-mode image data is generated. In other embodiments, only Doppler data is generated. In some embodiments, the processor circuit receives the first ultrasound data from the ultrasound imaging probe. In some embodiments, the processor circuit receives or retrieves the first ultrasound data from a memory device.

In step530, the processor circuit identifies, by image processing of the first ultrasound data, a location of the vessel within the field of view of the ultrasound transducer array. In some embodiments, the processor circuit generates ultrasound image data, such as B-mode image data and/or Doppler data using the first ultrasound data, and performs image processing on the B-mode and/or Doppler data to identify the location of the vessel within the field of view. In some embodiments, the processor circuit uses the Doppler data as seed points and B-mode image data to determine one or more boundaries of the vessel such as the inner diameter. Image processing may include one or more of erosion, dilation, segmentation, border detection, and/or any other suitable morphological or image processing technique to identify an anatomical feature in the ultrasound data. Additional information regarding morphological processing techniques can be found in, for example, U.S. Patent Application Publication No. 2017/0273658 titled “Acoustic streaming for fluid pool detection and identification” filed Aug. 12, 2015 with Shougang Wang et al. as inventors, U.S. Patent Application Publication No. 2014/0334680 titled “Image processing apparatus,” filed Nov. 14, 2012 with Iwo Willem Oscar Serile et al., as inventors, and Shawn Lankton, et al., “Localizing Region-Based Active Countrs,” IEEE Transactions on Image Processing, Vol. 17, No. 11 (November 2008), each of which is hereby incorporated by reference in its entirety.

In step540, the processor circuit generates an output based on the identified location of the vessel. The output may be generated based on the identified location of the vessel and a known position and/or orientation of the light source with respect to the field of view of the ultrasound transducer array. In some embodiments, the pose of the light source relative to the ultrasound transducer array may be fixed. In other embodiments, the pose of the light source relative to the ultrasound transducer array is adjustable. In some embodiments, the pose is manually adjustable by a user. In other embodiments, the light source is mechanically coupled to an actuator configured adjust the pose of the light source. In that regard, in some embodiments, the output generated in step540includes a control signal for controlling the actuator to adjust the pose of the light source. In some embodiments, the control signal is received by an electric motor (e.g., stepper motor), a servo motor, pneumatic control valve, and/or any other suitable actuator component configured to adjust the pose of the light source. In some embodiments, the output indicates which of a plurality of individual light elements to activate to illuminate the vessel. In some embodiments, the output is sent to a display and includes an indicator instructing a user to adjust a position of the ultrasound probe and/or the light source. For example, the indicator may include a textual instruction, a graphical instruction, and/or an audible instruction. The instruction may relate to a translation, tilt, fan, sweep, compression, or any other suitable type of movement of the ultrasound probe and/or the light source to direct light from the light source to the vessel.

In step550, the light source is adjusted based on the output. In some embodiments, the pose of the light source is automatically adjusted by the processor circuit and the actuator to illuminate the vessel. In some embodiments, the light source is coupled to an ultrasound probe at a fixed pose, position, and/or orientation relative to the ultrasound transducer array. In some embodiments, the pose, position, and/or orientation of the light source is manually adjusted by the user according to instructions output to a display, speaker, and/or other interface device. For example, in some embodiments, the light source movable in a manner so as to reduce the distance between a blood vessel and the light source. In some embodiments, a movable component allows translation along the surface of the skin as well as the capability to deform the skin surface such that the optical source is made to be closer to the vessel of interest. In some embodiments, the pose, position, and/or orientation of the light source may be adjusted by the user by following on-screen instructions associated with the output generated in step540to adjust the pose, position, and/or orientation of the ultrasound probe. For example, the light source may be coupled to the ultrasound probe by a jig or attachment that is sized, shaped, and structurally arranged to be coupled to the ultrasound probe. The jig or attachment may be configured to be attached to an existing or commercially-available ultrasound probe. The light source may also be coupled to the jig or attachment. In other embodiments, the light source and the ultrasound probe form an integral device including a single housing sized, shaped, and structurally arranged to be grasped by the hand of a user. In some embodiments, the light source is separate from the ultrasound probe and/or manually repositionable relative to the ultrasound probe. Accordingly, in some embodiments, the pose of the light source may be adjusted manually by a user independently of the pose, position, and/or orientation of the ultrasound probe. In some embodiments, the processor circuit determines, based on the identified location of the vessel in the field of view, that the current pose, position, and/or orientation of the light source is acceptable or optimal, and no adjustment of the light source is performed. Whether the pose of the light source is adjusted by an actuator or manually by moving the probe, the output may instruct the adjustment to place a vessel of interest within the optical path of the beam of light of the light source and/or improve the signal-to-noise ratio (SNR) of the photoacoustic signals from the vessel.

In some embodiments, adjusting the position and/or orientation of the light source may include pressing the light source into the skin of the patient to reduce the distance between the light source and the anatomical feature (e.g., vessel) of interest. Accordingly, in some embodiments, the actuator is configured to cause the light source to deform the skin of the patient by advancing the light source toward the anatomical feature. In some embodiments, the planar position and orientation of the light source is first adjusted based on image data, and then the light source is pressed into the skin along the axis of the light source. In some embodiments, the position adjustment and pressing movement are performed simultaneously. In some embodiments, the adjustments are carried out by the actuator automatically based on input from image processing and/or from other sensors or feedback devices. In that regard, in some embodiments, a feedback sensor is communicatively coupled to the light source and is configured to detect or measure one or more aspects associated with the movement (e.g., force, position), which is used as feedback to control the actuator. For example, the feedback sensor may include a load sensor, an encoder (e.g., rotary encoder), linear variable differential transformer (LVDT), hall effect sensor, proximity sensor, or any other suitable type of sensor capable of measuring the position and/or orientation of the light source relative to the ultrasound probe or transducer array. Controlling the actuation or movement of the light source may include using a feedback loop with the output of the feedback sensor and an input. For example, a PID loop may be used to control the actuation. In some embodiments, the processor circuit is further configured to detect using, for example, image processing of the image data and/or photoacoustic data, that the vessel of interest has collapsed, indicating excessive force applied by the light source. In response to detecting the collapse or deformation of the vessel, the processor circuit may be configured to adjust the force applied by the actuator on the light source. Further, the processor circuit may be configured to change photoacoustic signal processing parameters based on information obtained by the feedback sensor and/or the ultrasound imaging data.

In some embodiments, the movement of the light source may be performed manually by a user. For example, the light source may be separate or separable from the ultrasound probe, and the processor circuit may be configured to generate and output user instructions to move the light source (e.g., translation, tilt, compression into the skin) based on the output generated in step540. In some embodiments, the light source is movably coupled to the ultrasound probe by a jig, brace, or other attachment that allows for movement in one or more degrees of freedom. In some embodiments, the system further includes an acoustic coupling fluid dispensing subassembly configured to dispense an acoustic coupling gel in response to detecting insufficient contact between the ultrasound transducer and the skin of the patient. For example, the processor circuit may be configured to perform image processing on the image data obtained by the ultrasound transducer to detect poor acoustic coupling between the transducer and the skin of the patient. Based on this detection, the processor circuit may dispense acoustic coupling fluid at or near the ultrasound transducer to improve acoustic coupling. Accordingly, the fluid dispensing subassembly may ensure acoustic coupling after movement of the ultrasound probe and/or light source wherein the fluid or acoustic coupling gel is made to cover a void if created by the movement.

In some aspects, controlling the light source to reduce the distance to the vessel of interest may reduce the photoacoustic path length and allow for photoacoustic measurements to be made from blood vessels that are deep within the tissue under the skin surface. In some instances, for example, a physician may desire to obtain blood oxygenation measurements using the photoacoustic techniques described herein to determine an amount of oxygenated perfusion to the brain. For example, the techniques described herein may be used to obtain photoacoustic measurements from the internal jugular vein, which provide an indicator of oxygenated perfusion to the brain.

In step560, the processor circuit controls the light source to emit light into the anatomy. In some embodiments, the light source comprises a laser, such as a Helium Neon, Argon, Krypton, or Xenon Ion, Yttrium Aluminum Garnet (YAG), Semiconductor Diode, Diode, and/or any other suitable type of laser. The laser may be configured to operate in one or more modes, including continuous wave (CW), single pulsed, single pulsed Q-switched, mode-locked, repetitively pulsed, and/or any other suitable mode. In other embodiments, the light source comprises an incandescent bulb, a diode, such as a light-emitting diode (LED), fluorescent bulb, halogen bulb, or any other suitable source. In some embodiments, one or more optical fibers are coupled to a light element (e.g., laser, light bulb) and configured to deliver light within the field of view of the ultrasound transducer array. In some embodiments, the light source is co-located with the ultrasound transducer array. The light may comprise light or electromagnetic energy in the IR spectrum, NIR spectrum, microwave spectrum, visible spectrum, ultraviolet (UV) spectrum, or any other spectrum suitable to induce acoustic vibrations in the vessel.

In step570, with the light source activated to direct light to the vessel, second ultrasound data, such as photoacoustic data, is obtained using the ultrasound transducer array. The second ultrasound data or photoacoustic data is representative of the acoustic vibrations induced by the light source. In some embodiments, a photoacoustic measuring device includes distinct ultrasound transducers or transducer arrays to receive the first ultrasound data and the second ultrasound data, respectively. In some embodiments, the second ultrasound data is obtained at a same time as the first ultrasound data. In that regard, in some embodiments, the processor circuit is configured to generate ultrasound image data (e.g., B-mode data, Doppler data) in addition to photoacoustic data from the same ultrasound signals obtained by the ultrasound transducer array. In other embodiments, the first ultrasound data is obtained at a different time than the second ultrasound data. In some embodiments, the second ultrasound data is obtained in a sequence that interleaves the acquisition of the first ultrasound data and the second ultrasound data.

In step580, the processor circuit processes the second ultrasound data or photoacoustic data to compute a photoacoustic measurement. In some embodiments, computing the photoacoustic measurement includes generating a photoacoustic image based on the second ultrasound data. Computing the photoacoustic measurement may include performing a spectral or frequency analysis on the second ultrasound data. For example, computing the photoacoustic measurement may include comparing the intensity of one frequency band or bands to another frequency band or bands. In some embodiments, computing the photoacoustic measurement includes comparing a magnitude of the second ultrasound data to a local energy deposition. In some embodiments, computing the photoacoustic measurement includes analyzing dual optical wavelength photoacoustic waveforms detected by an ultrasound transducer array.

In step590, the processor circuit outputs a graphical representation of the computed photoacoustic measurement to a display or interface device. The photoacoustic measurement may include an oxygen saturation, oxygen concentration, and/or hemoglobin concentration value. The photoacoustic measurement may be associated with oxygenated hemoglobin (HbO2) and/or deoxygenated hemoglobin (Hb). In some embodiments, a photoacoustic image may be output to a display along with the graphical representation of the photoacoustic measurement. In some embodiments, the photoacoustic image is co-registered with a corresponding ultrasound image generated based on the first ultrasound data. For example, the processor circuit may be configured to output, to the display, a combined B-mode and Doppler image, alongside a photoacoustic image. The ultrasound image and the photoacoustic image may be obtained using an interleaved sequence in which ultrasound and photoacoustic image streams are received by the processor and output to show respective real-time or live views of the vessel.

It may be beneficial, in some instances, to gate photoacoustic measurements to specific areas or a photoacoustic image or specific time windows in a photoacoustic signal. Gating may increase the accuracy and/or efficiency of the photoacoustic measurement by the processor circuit. Gating may be used in addition to the approaches (e.g., method500) described above with respect to adjusting the position of the light source, or independently of the adjustment of the light source.FIG. 12illustrates a method600for computing a photoacoustic measurement using a gate determined using ultrasound image data, according to some embodiments of the present disclosure. It will be understood that the method600may be performed using one or more of the devices, systems, and/or methods described above, such as the system100shown inFIG. 1.

In Step610, the processor circuit receives first ultrasound data obtained by an ultrasound transducer array. The first ultrasound data may be used to generate B-mode and/or Doppler data (e.g., power Doppler, color Doppler, etc.). In that regard, in some embodiments, the first ultrasound data is obtained by interleaving B-mode and Doppler imaging sequences. In some embodiments, the ultrasound transducer array provides ultrasound signals or data, and a processor circuit generates B-mode image data and Doppler image data based on the same ultrasound signals. In some embodiments, only B-mode image data is generated. In other embodiments, only Doppler data is generated. In some embodiments, the processor circuit receives the first ultrasound data from the ultrasound imaging probe. In some embodiments, the processor circuit receives or retrieves the first ultrasound data from a memory device.

In step620, the processor circuit identifies, by image processing of the first ultrasound data, a location of the vessel within the field of view of the ultrasound transducer array. In some embodiments, the processor circuit generates ultrasound image data, such as B-mode image data and/or Doppler data using the first ultrasound data, and performs image processing on the B-mode and/or Doppler data to identify the location of the vessel within the field of view. In some embodiments, the processor circuit uses the Doppler data as seed points and B-mode image data to determine one or more boundaries of the vessel such as the inner diameter. Image processing may include one or more of erosion, dilation, segmentation, border detection, and/or any other suitable image processing technique to identify an anatomical feature in the ultrasound data.

In step630, the processor circuit determines a gate based on the identified location of the vessel. In some embodiments, the gate comprises a spatial gate specifying a region in which the vessel is located within the ultrasound image and/or photoacoustic image. Embodiments of spatial gates are shown inFIGS. 4A-5B. In other embodiments, the gate comprises a temporal gate indicating a time window for processing ultrasound signals of the second ultrasound data, as shown inFIG. 6, for example. In one embodiment, power- or color-Doppler imaging is used to localize coarse flow regions in the vessel initially. This coarse information is then fed back to a beamforming unit to perform high resolution (e.g. line density, low F #) b-mode or harmonic imaging to determine much higher resolution echogenicity changes indicating the proximal vessel wall. In step640, the processor circuit receives second ultrasound data, or photoacoustic data. The second ultrasound data or photoacoustic data is representative of the acoustic vibrations induced by the light source. In some embodiments, a photoacoustic measuring device includes distinct ultrasound transducers or transducer arrays to receive the first ultrasound data and the second ultrasound data, respectively. In some embodiments, the second ultrasound data is obtained at a same time as the first ultrasound data. In that regard, in some embodiments, the processor circuit is configured to generate ultrasound image data (e.g., B-mode data, Doppler data) in addition to photoacoustic data from the same ultrasound signals obtained by the ultrasound transducer array. In some embodiments, the second ultrasound data is obtained in a sequence that interleaves the acquisition of the first ultrasound data and the second ultrasound data. In some embodiments, the processor circuit automatically detects and localizes the vessel of interest using a Doppler image and a B-mode image generated based on the first ultrasound data, and a photoacoustic image generated based on the second ultrasound data. The processor circuit then sets the a priori analysis region in the photoacoustic image and/or photoacoustic waveforms of the second ultrasound data.

In step650, the processor circuit computes a photoacoustic measurement using the second ultrasound data and the gate determined or computed in step630. In step660, the processor circuit outputs the photoacoustic measurement to the display. The photoacoustic measurement may be output as an oxygen saturation, oxygen concentration, and/or hemoglobin concentration. The photoacoustic measurement may be associated with oxygenated hemoglobin (HbO2) and/or deoxygenated hemoglobin (Hb). In some embodiments, a photoacoustic image may be output to a display along with the photoacoustic measurement. In some embodiments, the photoacoustic image is co-registered with a corresponding ultrasound image generated based on the first ultrasound data. For example, the processor circuit may be configured to output, to the display, a combined B-mode and Doppler image, alongside a photoacoustic image. In some embodiments, a graphical representation of the gate determined in step630is also output to the display. In some embodiments, only one of the ultrasound image generated using the first ultrasound data or the photoacoustic image generated using the second ultrasound data is output to the display.

It will be understood that one or more of the steps of the methods500,600described above may be performed by one or more components of an ultrasound imaging system, such as a processor or processor circuit, a multiplexer, a beamformer, a signal processing unit, an image processing unit, or any other suitable component of the system. For example, one or more steps described above may be carried out by the processor circuit150described with respect toFIG. 13. The processing components of the system can be integrated within the ultrasound imaging device, contained within an external console, contained within a separate component, and/or distributed in various hardware components between the ultrasound imaging device, the external console, and/or the separate component.