Method and system for obtaining a 3D vector flow field

Abstract

A method for obtaining a 3D vector flow field from color Doppler ultrasound data is provided. The method comprises obtaining color Doppler ultrasound data from a plurality of acquisition positions, wherein the plurality of acquisition positions comprises a target acquisition position and one or more additional acquisition positions, wherein the one or more additional acquisition positions are adjacent to the target acquisition position. A 3D vector flow field is then derived from the obtained color Doppler ultrasound data.

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of ultrasound imaging, and more specifically to the field of ultrasound flow measurement. BACKGROUND

[0002] Color Doppler imaging allows a user to visualize flow information along the ultrasound beam. This functionality has become widely deployed in echography systems.

[0003] Color Doppler data provides coarse flow orientation information, either along the beam orientation towards the probe or away from the probe. However, flow information outside the beam orientation is usually lost. Therefore, several attempts have been made to derive complete vector flow information from color Doppler data.

[0004] A method has been proposed which is to employ an ultrafast scanning scheme, such as the method described in Osmanski, B.-F., M. Pernot, G. Montaldo, A. Bel, E. Messas, and M. Tanter, "Ultrafast Doppler imaging of blood flow dynamics in the myocardium," IEEE Transactions on Medical Imaging 31, no. 8, 2012, which makes use of planar or diverging transmit waves. This method requires redesigning the ultrafast acquisition sequence and redesigning the ultrasound system front-end to make it suitable for ultrafast use.

[0005] Another method includes estimating flow from existing Doppler measurements based on a physical model, such as the method described in Garcia et al., "Two-dimensional intraventricular flow mapping by digital processing conventional color-Doppler echocardiography images," IEEE Trans. Med. Imag., vol. 29, no. 10, pp. 1701-1713, Oct. 2010. The model-based approach proposed in the above document reconstructs a 2D flow field for 2D color Doppler frames. However, in this method, three-dimensional flow information is missing. Therefore, to reconstruct a 3D flow field, a full volume acquisition would be required; however, the requirement of having a full 3D volume results in a reduced frame rate.

[0006] EP 3586758 A1 discloses a method for generating a quantification of the transvalvular pressure within a cavity, which comprises acquiring a plurality of color Doppler ultrasound image frames, wherein the image frames comprise a view of a valve, one of which is then presented to a user. The user can then provide an input to indicate the location of the valve within the image frame. The location of the valve is then tracked within the remaining image frames based on the user input. A vector flow is estimated based on the color Doppler image frames and the tracked location of the valve, which can be used to estimate the flow across the valve(s) and the flow within the cavity.

[0007] US 2015 / 366531 A1 discloses an ultrasonic diagnostic apparatus including an ultrasonic sensor that transmits ultrasonic waves and senses echo signals of the ultrasonic waves, a signal processor that processes a signal sensed by the ultrasonic sensor, a B-mode image generation unit that generates a brightness mode (B-mode) image in a 2D plane based on a signal processing result obtained by the signal processor, and extracts left ventricular boundary data from the generated B-mode image, a C-mode image generation unit that generates Doppler data based on a signal processing result obtained by the signal processor for generating a C-mode image, and a blood flow velocity vector calculation unit that calculates a blood flow velocity vector in a 2D image plane based on a relationship equation between the extracted left ventricular boundary data, the Doppler data, and the blood flow velocity vector, and a simultaneous equation composed of a 2D Navier-Stokes equation obtained from image data generated by the signal processor through signal processing, wherein the Navier-Stokes equation also uses a mass source term as a variable, the mass source term representing a distribution of sources and sinks of mass with respect to the 2D image plane.

[0008] Thus, there is a need for means to derive complete 3D flow information from limited input data. SUMMARY

[0009] The invention is defined by the claims.

[0010] According to examples in accordance with an aspect of the invention, there is provided a method for obtaining a 3D vector flow field from color Doppler ultrasound data, the method comprising:

[0011] obtaining color Doppler ultrasound data from a plurality of acquisition positions, wherein the plurality of acquisition positions comprises:

[0012] a target acquisition position; and

[0013] one or more additional acquisition positions, wherein the one or more additional acquisition positions are adjacent to the target acquisition position; and

[0014] deriving a 3D vector flow field from the obtained color Doppler ultrasound data.

[0015] The method provides a means to derive 3D vector flow information from standard color Doppler ultrasound data acquisition.

[0016] By considering color Doppler data acquired from multiple adjacent acquisition positions, it is possible to derive complete detailed 3D vector flow information without the need for a fully implemented 3D ultrasound acquisition.

[0017] In embodiments, deriving the 3D vector flow field comprises:

[0018] obtaining a flow divergence equation;

[0019] solving the flow divergence equation to match the obtained color Doppler ultrasound data; and

[0020] deriving a 3D flow vector field based on the solved flow divergence equation.

[0021] In this way, it is possible to derive a 3D vector flow field from an equation that contains known physical constraints (which is solved to match the acquired data), thereby obtaining accurate 3D vector flow information that matches the acquired data.

[0022] In further embodiments, the flow divergence equation comprises a divergence, and wherein the divergence is zero.

[0023] In this way, it is possible to utilize the physical constraint of incompressibility of a fluid to accurately model the behavior of blood within the equation.

[0024] In embodiments, the multiple acquisition positions comprise a first additional acquisition position and a second additional acquisition position, wherein the first additional acquisition position and the second additional acquisition position are adjacent to the target acquisition position such that the target acquisition position is positioned between the first additional acquisition position and the second additional acquisition position.

[0025] In this way, it is possible to use additional information to obtain a 3D vector flow field, thereby improving the accuracy of the final 3D flow information.

[0026] In further embodiments, the first additional acquisition position and the second additional acquisition position are positioned adjacent to the target acquisition position in an elevation direction.

[0027] In embodiments, deriving the 3D vector flow field is performed using a travel window across the multiple acquisition positions.

[0028] In this way, it is possible to obtain a 3D vector flow field without the need to acquire color Doppler data from the entire field of view of the probe.

[0029] In embodiments, the plurality of acquisition positions comprises more than three acquisition positions, and wherein the travel window comprises the target acquisition position and two additional acquisition positions.

[0030] In embodiments, the derived 3D vector flow field is iteratively refined using the output of the travel window.

[0031] In this way, the 3D vector flow field can be refined as data acquisition continues to occur.

[0032] In embodiments, the plurality of acquisition positions comprises:

[0033] 3D acquisition subvolumes; and / or

[0034] 2D acquisition planes; and / or

[0035] 1D scan lines.

[0036] In this way, 3D vector flow fields can be obtained using any color Doppler data, including 3D, 2D, and ID Doppler data.

[0037] In further embodiments, the plurality of acquisition positions comprises ID scan lines, and wherein the plurality of acquisition positions further comprises one or more additional acquisition positions positioned adjacent to the target acquisition position in an azimuthal direction.

[0038] In this way, the accuracy of the 3D vector flow field derived from the acquisition of ID scan lines can be improved.

[0039] According to examples in accordance with an aspect of the present application, there is provided a computer program comprising computer program code means adapted to perform the above-mentioned method when said computer program is run on a computer.

[0040] According to examples in accordance with an aspect of the present application, there is provided a system for obtaining a 3D vector flow field from color Doppler ultrasound data, the system comprising a processor adapted to:

[0041] obtain color Doppler ultrasound data from a plurality of acquisition positions, wherein the plurality of acquisition positions comprises:

[0042] a target acquisition position; and

[0043] one or more additional acquisition positions, wherein the one or more additional acquisition positions are adjacent to the target acquisition position; and

[0044] derive a 3D vector flow field from the obtained color Doppler ultrasound data.

[0045] In embodiments, the system further comprises an ultrasound probe, the ultrasound probe being adapted to obtain the color Doppler data.

[0046] In embodiments, the processor is further adapted to generate a visual representation of the 3D vector flow field, and wherein the system further comprises a display unit, the display unit being adapted to display the visual representation.

[0047] In embodiments, the visual representation is displayed in combination with a visualization of the target acquisition location.

[0048] These and other aspects of the application will be apparent from and elucidated with reference to the embodiments described hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0049] For a better understanding of the present application, and to show how it can be put into effect, reference will now be made, purely by way of example, to the accompanying drawings in which:

[0050] Figure 1 An ultrasound diagnostic imaging system is shown to explain the general operation;

[0051] Figure 2 A method of the application is shown;

[0052] Figures 3a to 3c A schematic representation of an exemplary acquisition scheme is shown; and

[0053] Figure 4 A schematic representation of the derivation of a 3D vector flow field using a running window is shown. DETAILED DESCRIPTION

[0054] The present application will be described with reference to the accompanying drawings.

[0055] It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of apparatuses, systems and methods, are intended for purposes of illustration only and are not intended to limit the scope of the application. These and other features, aspects, and advantages of the apparatuses, systems and methods of the present application will become better understood from the following description, appended claims, and accompanying drawings. It should be understood that the drawings are only schematic and are not drawn to scale. It should further be understood that the use of identical reference numerals in different figures serves to identify identical, or in some instances, similar or equivalent parts.

[0056] The present application provides a method for obtaining a 3D vector flow field from color Doppler ultrasound data. The method comprises obtaining color Doppler ultrasound data from a plurality of acquisition locations, wherein the plurality of acquisition locations comprises a target acquisition location and one or more additional acquisition locations, wherein the one or more additional acquisition locations are adjacent to the target acquisition location. A 3D vector flow field is then derived from the obtained color Doppler ultrasound data

[0057] The overall operation of an exemplary ultrasound system will first be described with reference to Figure 1 and with emphasis on the signal processing functions of the system, as the present application relates to the processing of signals measured by a transducer array.

[0058] The system includes an array transducer probe 4 having a transducer array 6 for transmitting ultrasound waves and receiving return information. The transducer array 6 can include CMUT transducers; piezoelectric transducers formed from materials such as PZT or PVDF; or any other suitable transducer technology. In this example, the transducer array 6 is a two-dimensional array of transducers 8 capable of scanning a 2D plane or a three-dimensional volume of interest. In another example, the transducer array can be a ID array.

[0059] The transducer array 6 is coupled to a microbeamformer 12, which controls the reception of signals by the transducer elements. The microbeamformer is capable of at least partially beamforming signals received by sub-arrays (commonly referred to as "groups" or "tiles") of the transducers, as described in U.S. Patents US 5997479 (Savord et al.), US 6013032 (Savord), and US 6623432 (Powers et al.).

[0060] It should be noted that the microbeamformer is entirely optional. In addition, the system includes a transmit / receive (T / R) switch 16 to which the microbeamformer 12 can be coupled, and which switches the array between transmit and receive modes, and protects the main beamformer 20 from high-energy transmit signals in the case where the microbeamformer is not used and the transducer array is operated directly by the main system beamformer. Transmission of ultrasound beams from the transducer array 6 is directed by a transducer controller 18 coupled through the T / R switch 16 to the microbeamformer and to a main transmit beamformer (not shown), which can receive input from user operation of a user interface or control panel 38. The controller 18 can include transmit circuitry arranged to drive the transducer elements of the array 6 (directly or via the microbeamformer) during transmit mode.

[0061] In a typical line-by-line imaging sequence, the beamforming system within the probe can operate as follows. During transmission, the beamformer (which can be either the microbeamformer or the main system beamformer, depending on the implementation) activates a transducer array or a sub-aperture of the transducer array. The sub-aperture can be a one-dimensional line of transducers or a two-dimensional tile of transducers within a larger array. In transmit mode, the focusing and steering of the ultrasound beam generated by the array or sub-aperture of the array is controlled, as described below.

[0062] Upon receiving the backscattered echo signals from the object, the received signals undergo receive beamforming (described below) in order to align the received signals, and in the case where sub-apertures are being used, the sub-aperture is then shifted, for example, by one transducer element. The shifted sub-aperture is then activated and the process repeats until all transducer elements of the transducer array have been activated.

[0063] For each line (or sub-aperture), the total received signal for the associated line used to form the final ultrasound image will be the sum of the voltage signals measured by the transducer elements of the given sub-aperture during the receive period. The resulting line signal, after the beamforming process below, is commonly referred to as radio frequency (RF) data. Each line signal (RF data set) generated by the various sub-apertures then undergoes additional processing to generate the lines of the final ultrasound image. The amplitude of the line signal as a function of time will contribute to the brightness of the ultrasound image as a function of depth, where high amplitude peaks will correspond to bright pixels (or collections of pixels) in the final image. Peaks occurring near the beginning of the line signal will represent echoes from shallow structures, while peaks occurring later in the line signal will represent echoes from structures at increasing depths within the object.

[0064] One of the functions controlled by the transducer controller 18 is the direction of beam steering and focusing. The beam can be steered straight ahead (normal to it), or at different angles for a wider field of view. The steering and focusing of the transmitted beam can be controlled in terms of transducer element actuation times.

[0065] Two methods can be distinguished in general ultrasound data acquisition: plane wave imaging and "beam steering" imaging. The two methods are distinguished by the presence of beamforming in the transmit mode ("beam steering" imaging) and / or the receive mode (plane wave imaging and "beam steering" imaging).

[0066] Looking first at the focusing function, the transducer array generates a plane wave by activating all the transducer elements simultaneously, which diverges as it travels through the object. In this case, the beam of ultrasound waves remains unfocused. By introducing a position-dependent time delay to the activation of the transducers, it is possible to make the wavefront of the beam converge at a desired point, which is called the focal zone. The focal zone is defined as the point where the lateral beam width is less than half the transmitted beam width. In this way, the lateral resolution of the final ultrasound image is improved.

[0067] For example, if the time delay activates the transducer elements in a series starting from the outermost elements and ending at the center element(s) of the transducer array, a focal zone will be formed at a given distance from the probe, coinciding with the center element(s). The distance of the focal zone from the probe will vary according to the time delay between each subsequent round of transducer element activation. After the beam passes the focal zone, it will start to diverge, thus forming a far field imaging region. It should be noted that for a focal zone positioned close to the transducer array, the ultrasound beam will diverge rapidly in the far field, resulting in beam width artifacts in the final image. Typically, due to large overlap in the ultrasound beam, the near field, positioned between the transducer array and the focal zone, shows little detail. Thus, changing the position of the focal zone results in a significant change in the quality of the final image.

[0068] It should be noted that in transmit mode, only one focal point can be defined unless the ultrasound image is divided into multiple focal zones, each of which can have a different transmit focal point.

[0069] Furthermore, upon receiving echo signals from within the object, the inverse of the above process can be performed in order to perform receive focusing. In other words, the incoming signals can be received by the transducer elements and undergo electronic time delays before being passed into the system for signal processing. The simplest example of this is called delay-and-sum beamforming. The receive focusing of the transducer array can be dynamically adjusted according to time.

[0070] Now turning to the function of beam steering, by applying the correct time delays to the transducer elements, it is possible to impart a desired angle on the ultrasound beam as it leaves the transducer array. For example, by activating the transducers on the first side of the array in a sequence that ends on the opposite side of the array, followed by the remaining transducers, the wavefront of the beam will be angled towards the second side. The size of the steering angle relative to the normal of the transducer array depends on the size of the time delay between the activation of the subsequent transducer elements.

[0071] Additionally, it is possible to focus and steer the beam, where the total time delay applied to each transducer element is the sum of both the focusing and steering time delays. In this case, the transducer array is called a phased array.

[0072] In the case of CMUT transducers, which require a DC bias voltage for their activation, the transducer controller 18 can be coupled to control a DC bias control 45 for the transducer array. The DC bias control 45 sets the DC bias voltage(s) applied to the CMUT transducer elements.

[0073] The analog ultrasound signals, often referred to as channel data, for each transducer element of the transducer array enter the system through a receive channel. In the receive channel, a partial beamformed signal is produced by the microbeamformer 12 from the channel data and then passed to the main receive beamformer 20, where the partial beamformed signals from individual tiles of transducers are combined into a full beamformed signal, referred to as radio frequency (RF) data. The beamforming performed at each stage can be performed as described above, or can include additional functionality. For example, the main beamformer 20 can have 128 channels, with each receiving a partial beamformed signal from a tile of tens or hundreds of transducer elements. In this way, the signals received by thousands of transducers of the transducer array can effectively contribute to a single beamformed signal.

[0074] The beamformed receive signal is coupled to a signal processor 22. The signal processor 22 is capable of processing the received echo signals in various ways, for example: bandpass filtering; decimation; I and Q component separation; and harmonic signal separation, which is used to separate linear signals from nonlinear signals, enabling the identification of nonlinear (higher harmonics of the fundamental frequency) echo signals returned from tissue and microbubbles. The signal processor can also perform additional signal enhancements, for example, speckle reduction, signal compounding, and noise cancellation. The bandpass filter in the signal processor can be a tracking filter, whose passband slides from a higher frequency band to a lower frequency band as the echo signals are received from increasing depths, rejecting noise at higher frequencies from greater depths, which typically lack anatomical information.

[0075] The beamformers for transmission and for reception are implemented in different hardware and can have different functionality. Of course, the receiver beamformers are designed to take into account the characteristics of the transmit beamformers. For simplicity, in Figure 1 only the receiver beamformers 12, 20 are shown in

[0076] The function of the microbeamformer 12 is to provide an initial combination of signals in order to reduce the number of analog signal paths. This is typically performed in the analog domain.

[0077] The final beamforming is done in the main beamformer 20 and is typically done after digitization.

[0078] The transmit and receive channels use the same transducer array 6 with a fixed frequency band. However, the bandwidth occupied by the transmit pulses can vary depending on the transmit beamforming used. The receive channel can capture the entire transducer bandwidth (which is the classical approach), or by using bandpass processing, it can only extract the bandwidth containing the desired information (e.g. the harmonics of the main harmonic).

[0079] The RF signals can then be coupled to a B-mode (i.e., brightness mode or 2D imaging mode) processor 26 and a Doppler processor 28. The B-mode processor 26 performs amplitude detection on the received ultrasound signals to image structures in the body, such as organ tissue and blood vessels. In the case of line-by-line imaging, each line (beam) is represented by an associated RF signal whose amplitudes are used to generate brightness values to be assigned to pixels in a B-mode image. The exact location of an image within a pixel is determined by the location of the associated amplitude measurement along the RF signal and the line (beam) number of the RF signal. The B-mode image of such structures can be formed in a harmonic or fundamental image mode or a combination of both, as described in U.S. Patent 6,283,919 (Roundhill et al.) and U.S. Patent 6,458,083 (Jago et al.). The Doppler processor 28 processes temporally distinct signals produced by tissue motion and blood flow to detect moving substances, such as the flow of blood cells in the image field. The Doppler processor 28 typically includes a wall filter with parameters set to pass or reject echoes returned from selected types of materials in the body.

[0080] The structure and motion signals produced by the B-mode and Doppler processors are coupled to a scan converter 32 and a multiplanar reformatter 44. The scan converter 32 spatially arranges the echo signals according to the spatial relationship in which they were received in the desired image format. In other words, the scan converter functions to convert the RF data from a cylindrical coordinate system to a Cartesian coordinate system suitable for displaying the ultrasound image on an image display 40. In the case of B-mode imaging, the brightness of a pixel at a given coordinate is proportional to the amplitude of the RF signal received from that location. For example, the scan converter can arrange the echo signals into a two-dimensional (2D) sector format or a cone three-dimensional (3D) image. The scan converter can superimpose a color corresponding to motion at a point in the image field on the B-mode structure image, where a Doppler estimated velocity produces a given color. The combined B-mode structure image and color Doppler image depict the motion of tissue and blood flow within the structure image field. The multiplanar reformatter converts echoes received from points in a common plane in a volumetric region of the body into an ultrasound image of that plane, as described in U.S. Patent 6,443,896 (Detmer). The volume Tenderer 42 converts the echo signals of a 3D data set into a projected 3D image, as viewed from a given reference point, as described in U.S. Patent 6,530,885 (Entrekin et al.).

[0081] 2D or 3D images are coupled from the scan converter 32, the multiplanar reformatter 44 and the volume renderer 42 to the image processor 30 for further enhancement, buffering and temporary storage for display on the image display 40. The imaging processor can be adapted to remove certain imaging artifacts from the final ultrasound image, such as: acoustic shadows caused, for example, by strong attenuators or refractions; post- enhancement caused, for example, by weak attenuators; reverberation artifacts, for example, where highly reflective tissue interfaces are located in close proximity; and the like. In addition, the image processor can be adapted to process certain speckle reduction functions in order to improve the contrast of the final ultrasound image.

[0082] In addition to being used for imaging, the blood flow values produced by the Doppler processor 28 and the tissue structure information produced by the B-mode processor 26 are coupled to a quantification processor 34. The quantification processor produces measures of different flow conditions, such as volume rates of blood flow in addition to structural measurements such as size of an organ and gestational age. The quantification processor can receive input from the user control panel 38, such as points in the anatomy of the image where measurements are to be made.

[0083] Output data from the quantification processor is coupled to a graphics processor 36 for rendering measurement graphics and values on the display 40 along with the images, and for audio output from the display device 40. The graphics processor 36 can also generate graphics overlays for display with the ultrasound images. These graphics overlays can contain standard identifying information, such as patient name, date and time of the image, imaging parameters, and the like. The graphics processor receives input from the user interface 38 for these purposes, such as the patient name. The user interface is also coupled to the transmit controller 18 to control the generation of ultrasound signals from the transducer array 6, and thus the images produced by the transducer array and ultrasound system. The transmit control functions of the controller 18 are only one of the functions performed. The controller 18 also takes into account the mode of operation (given by the user) and the corresponding required transmitter configuration and bandpass configuration in the receiver analog-to-digital converters. The controller 18 can be a state machine with fixed states.

[0084] The user interface is also coupled to the multiplanar reformatter 44 for selecting and controlling the planes of the multiplane multiplanar reformatted (MPR) images, which can be used to perform the measures of quantification in the image field of the MPR images.

[0085] Figure 2 A method 100 for obtaining a 3D vector flow field from color Doppler ultrasound data is shown.

[0086] The method starts in step 110 by obtaining color Doppler ultrasound data from a plurality of acquisition positions. The plurality of acquisition positions comprises a target acquisition position 112 and one or more additional acquisition positions 114, wherein the one or more additional acquisition positions are adjacent to the target acquisition position.

[0087] By taking into account additional color Doppler information near the target acquisition location, the 3D vector flow field can be more accurately derived. In other words, by using additional acquisition locations, the full 3D flow orientation can be taken into account, rather than falsely assuming flow information based on only a single acquisition location.

[0088] In step 120, a 3D vector flow field is derived from the obtained color Doppler ultrasound data.

[0089] For example, the 3D vector flow field can be derived from the color Doppler ultrasound data by obtaining a flow divergence equation. The flow divergence equation can then be solved in step 122 to match the obtained color Doppler ultrasound data, and in step 124, a 3D flow vector field can be derived based on the solved flow divergence equation.

[0090] Looking in more detail at step 122, the flow divergence equation can be as follows:

[0091] where,

[0092] where: u is the 3D flow vector field to be solved; and s is the Doppler acquisition orientation.

[0093] In the above equation, the term loss specifies a loss function that measures the similarity between the predicted Doppler values and the observed color Doppler data. For example, the loss function can be a quadratic loss function. The equation seeks to minimize the loss function in order to maximize the similarity between the predicted Doppler values and the observed color Doppler data (Doppler data).

[0094] No divergence constraint The 3D divergence can be computed near the target acquisition location. Additional boundary conditions can also be included in the divergence equation. The divergence equation can be numerically solved using a gradient method.

[0095] In other words, the predicted Doppler values u from the 3D field can be matched to the observed color Doppler measurements while at the same time constraining the equation to a no divergence condition: The 3D divergence is available due to the acquisition of color Doppler data at one or more additional acquisition locations in addition to the target acquisition location.

[0096] The divergence equation can be constrained based on any physical parameter in order to accurately model flow constraints in a given application. In the above example, the equation is constrained based on the assumption that the divergence in the 3D vector flow field is zero, which is based on the known incompressibility of the fluid.

[0097] The proposed method can be easily implemented in current systems capable of performing color Doppler imaging without any need to redesign the system front-end.

[0098] Figures 3a to 3c A schematic representation of an exemplary acquisition scheme that can be employed in the above method is shown.

[0099] Figure 3a An example is shown in which the ultrasound probe 200 is adapted to acquire a plurality of 3D sub-volumes. In this example, the target acquisition location is a target 3D sub-volume 210, and the one or more additional acquisition locations include a first additional 3D sub-volume 220 and a second additional 3D sub-volume 230. In this example, the first additional 3D sub-volume and the second additional 3D sub-volume are positioned such that they are adjacent to the target 3D sub-volume in the elevation direction, and wherein the target 3D sub-volume is located between the first additional 3D sub-volume and the second additional 3D sub-volume. Figure 3a An example is shown in which the ultrasound probe 200 is adapted to acquire a plurality of 3D sub-volumes. In this example, the target acquisition location is a target 3D sub-volume 210, and the one or more additional acquisition locations include a first additional 3D sub-volume 220 and a second additional 3D sub-volume 230. In this example, the first additional 3D sub-volume and the second additional 3D sub-volume are positioned such that they are adjacent to the target 3D sub-volume in the elevation direction, and wherein the target 3D sub-volume is located between the first additional 3D sub-volume and the second additional 3D sub-volume.

[0100] Figure 3b An example is shown in which the ultrasound probe 200 is adapted to acquire a plurality of 2D acquisition planes. In this example, the target acquisition location is a target 2D plane 240, and the one or more additional acquisition locations include a first additional 2D plane 250 and a second additional 2D plane 260. In this example, the first additional 2D plane and the second additional 2D plane are positioned such that they are adjacent to the target 2D plane in the elevation direction, and wherein the target 2D plane is located between the first additional 2D plane and the second additional 2D plane. Figure 3b An example is shown in which the ultrasound probe 200 is adapted to acquire a plurality of 3D sub-volumes. In this example, the target acquisition location is a target 3D sub-volume 210, and the one or more additional acquisition locations include a first additional 3D sub-volume 220 and a second additional 3D sub-volume 230. In this example, the first additional 3D sub-volume and the second additional 3D sub-volume are positioned such that they are adjacent to the target 3D sub-volume in the elevation direction, and wherein the target 3D sub-volume is located between the first additional 3D sub-volume and the second additional 3D sub-volume.

[0101] In other words, the method described above with reference to Figure 2 The method described above can be implemented in a 3D or 2D color Doppler imaging scheme by additionally including color Doppler information from in the vicinity of the target acquisition location. In this way, 3D flow information can be derived from 2D color Doppler data. The 3D flow information can then be displayed on the target 2D frame.

[0102] Figure 3c An example is shown in which the ultrasound probe 200 is adapted to acquire a plurality of 1D scan lines. In this example, the target acquisition location is a target 1D scan line 270, and the one or more additional acquisition locations include a first additional 1D scan line 280 and a second additional 1D scan line 285. In this example, the first additional 1D scan line and the second additional 1D scan line are positioned such that they are adjacent to the target 1D scan line in the elevation direction, and wherein the target 1D scan line is located between the first additional 1D scan line and the second additional 1D scan line. Figure 3c An example is shown in which the ultrasound probe 200 is adapted to acquire a plurality of 3D sub-volumes. In this example, the target acquisition location is a target 3D sub-volume 210, and the one or more additional acquisition locations include a first additional 3D sub-volume 220 and a second additional 3D sub-volume 230. In this example, the first additional 3D sub-volume and the second additional 3D sub-volume are positioned such that they are adjacent to the target 3D sub-volume in the elevation direction, and wherein the target 3D sub-volume is located between the first additional 3D sub-volume and the second additional 3D sub-volume.

[0103] Additionally, Figure 3cThe example illustrates a case where multiple acquisition locations also include a third additional 1D scan line 290 and a fourth additional 1D scan line 295 located adjacent to the target acquisition location in the azimuth direction, and wherein the target 1D scan line is located between the third additional 1D scan line and the fourth additional 1D scan line.

[0104] In another example, when the acquisition location includes multiple 1D scan lines, one or more additional acquisition locations may include a single additional 1D scan line adjacent to the target 1D scan line in the elevation direction and a single additional 1D scan line adjacent to the target 1D scan line in the azimuth direction.

[0105] In other words, the above about Figure 2 The described method can be implemented for 1D scan lines, as well as 3D sub-volumes and 2D planes. Based on each 1D scan line, 3D flow information about points along each line can be calculated.

[0106] 1D scan lines are typically used to acquire M-mode ultrasound data. It is possible to derive the 3D vector flow field by acquiring several additional 1D scan lines near the target 1D scan line in both the azimuth and elevation directions.

[0107] Furthermore, the multi-line flow estimation scheme used in the 1D scanline example can also be applied to 2D and 3D color Doppler acquisitions. In these cases, the 3D vector flow field can be derived from each arrival line of a given acquisition, rather than from each plane, thereby further reducing the delay between color data acquisition and the arrival of the 3D vector flow field results.

[0108] Figure 4 A schematic representation of 3D vector flow field is shown using a travel window.

[0109] In relation to Figure 4 In the described example, a 3-frame travel window is provided to derive a 3D vector flow field based on the acquired color Doppler data. It should be noted that any number of frames can be selected for the travel window based on a given application. Increasing the number of frames increases the accuracy of the resulting 3D vector flow field, but also increases the time spent computing the 3D vector flow field. Conversely, reducing the number of frames for the travel window achieves faster computation time, but lower accuracy. It has been found that using 3 frames for the travel window achieves a good balance between accuracy and computation time.

[0110] The use of a travel window allows for the reconstruction of the 3D vector flow field at each acquisition location (e.g., a 2D elevation plane) immediately after each acquisition has been performed. In other words, by using a travel window, it is not necessary to acquire the entire volume of interest in order to calculate the 3D vector flow field.

[0111] CheckFigure 4 At step 300, elevation planes in the 3D volume are denoted as E t For example, E0, E1 and E2 are first, second and third elevation planes, respectively, which correspond to the order of acquisition over time. As the elevation planes are acquired, as soon as 3 successive acquisition planes are available, a 3-plane volume can be formed in which a 3D vector flow field estimation is performed and the 3D vector field can be preserved on the intermediate plane.

[0112] By way of example, at step 300, E0, E1 and E2 are available, which means that a 3D vector flow field V1 can be computed on E1. At step 310, E3 is acquired and E1, E2 and E3 can be used to compute the vector flow V2 on E2. At step 320, E4 is acquired and E2, E3 and E4 can be used to compute the vector flow V3 on E3. The process can then continue until the end of the acquisition sequence.

[0113] In this way, a 3D vector flow field is computed at each acquisition. In other words, a 3D vector flow field is produced at each arriving frame without waiting until the end of the complete volume acquisition before computing the 3D vector flow field.

[0114] Each 3D vector flow field computed via a travelling window can be replaced by a subsequent 3D vector flow field. Alternatively, the 3D vector flow fields can be added together across all acquisition locations. In addition, the 3D vector flow field can be iteratively improved based on each subsequently computed 3D vector flow field.

[0115] The 3D vector flow field can include vectors of any density suitable for the given application of the method described herein. For example, the 3D vector flow field can include at least one vector measurement per 2 mm or per 1 mm. In addition, any ultrasound probe capable of performing color Doppler imaging can be used to acquire the color Doppler ultrasound data used in the method above. For example, a probe having a linear array of transducers or a phased array of transducers can be used.

[0116] Variations to the disclosed embodiments can become apparent to those of ordinary skill in the art upon reading the foregoing disclosure and it is intended that such variations be considered within the scope of the present application. In the claims, the word "comprising" does not exclude other elements or steps, and the words "a" or "an" do not exclude a plurality.

[0117] A single processor or other unit can fulfill the functions of several items recited in the claims.

[0118] The fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0119] A computer program can be stored / distributed on a suitable medium, such as an optical storage medium or a solid-state storage medium supplied together with or as part of other hardware, but can also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.

[0120] If the term "adapted to" is used in the claims or specification it should be noted that the term "adapted to" is intended to be equivalent to the term "configured to".

[0121] The use of any of the following terms in the claims or specification should not be interpreted as limiting the scope:

Claims

1. A method (100) for obtaining a 3D vector flow field from color Doppler ultrasound data, the method comprising: obtaining (110) color Doppler ultrasound data from a plurality of acquisition locations, wherein the plurality of acquisition locations comprises: a target acquisition location (112); and one or more additional acquisition locations (114), wherein the one or more additional acquisition locations are adjacent to the target acquisition location; and deriving (120) a 3D vector flow field from the obtained color Doppler ultrasound data.

2. The method (100) of claim 1, wherein Deriving the 3D vector flow field comprises: obtaining a flow divergence equation; solving (122) the flow divergence equation to match the obtained color Doppler ultrasound data; and deriving (124) a 3D flow vector field based on the solved flow divergence equation.

3. The method (100) of claim 2, wherein The flow divergence equation comprises a divergence, and wherein the divergence is zero.

4. The method (100) according to any one of claims 1 to 3, wherein The plurality of acquisition locations comprises a first additional acquisition location and a second additional acquisition location, wherein the first additional acquisition location and the second additional acquisition location are adjacent to the target acquisition location such that the target acquisition location is positioned between the first additional acquisition location and the second additional acquisition location.

5. The method (100) of claim 4, wherein The first additional acquisition location and the second additional acquisition location are positioned adjacent to the target acquisition location in an elevation direction.

6. The method (100) according to any one of claims 1 to 3, wherein Deriving the 3D vector flow field is performed using a travel window across the plurality of acquisition locations.

7. The method (100) of claim 6, wherein The plurality of acquisition locations comprises more than three acquisition locations, and wherein the travel window comprises the target acquisition location and two additional acquisition locations.

8. The method (100) of claim 6, wherein The derived 3D vector flow field is iteratively refined using an output of the travel window.

9. The method (100) according to any one of claims 1 to 3, wherein The plurality of acquisition locations comprises: a 3D acquisition sub-volume; and / or a 2D acquisition plane; and / or a ID scan line.

10. The method (100) of claim 9, wherein The plurality of acquisition locations comprises a ID scan line, and wherein the plurality of acquisition locations further comprises one or more additional acquisition locations positioned adjacent to the target acquisition location in an azimuth direction.

11. A system (2) for obtaining a 3D vector flow field from color Doppler ultrasound data, the system comprising a processor adapted to: Color Doppler ultrasound data is obtained from a plurality of acquisition positions, wherein, The plurality of acquisition locations comprises: a target acquisition location; and one or more additional acquisition locations, wherein the one or more additional acquisition locations are adjacent to the target acquisition location; and deriving a 3D vector flow field from the obtained color Doppler ultrasound data.

12. The system (2) according to claim 11, wherein The system further comprises an ultrasound probe (4) adapted to obtain the color Doppler ultrasound data.

13. The system (2) according to claim 11 or 12, wherein The processor is further adapted to generate a visual representation of the 3D vector flow field, and wherein the system further comprises a display unit adapted to display the visual representation.

14. The system (2) according to claim 13, wherein The visual representation is displayed in combination with a visualization of the target acquisition location.

15. A computer program product comprising a computer program, the computer program comprising computer program code means adapted to perform the method of any one of claims 1 to 10 when the computer program is run on a processor of a system according to any one of claims 11 to 14.

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