Ultrasonic curved linear array operable in continuous wave mode

Abstract

Continuous wave (CW) Doppler analysis is performed using an ultrasound system with a linear array transducer probe. The linear array may be curved or flat. The array transducer has more transducer elements than the number of channels of a beamformer of the ultrasound system. To accommodate this difference, some of the elements of the array are multiplexed to the beamformer such that only one of a pair of elements is coupled to the beamformer at any one time. The plurality of elements of the array transducer are not multiplexed and are directly coupled to the beamformer. During imaging, both multiplexed and unmultiplexed transducer elements may be used to generate a signal for an image, and during CW Doppler analysis, only unmultiplexed transducer elements are used for CW Doppler transmit and receive apertures.

Description

Technical Field

[0001] This invention relates to ultrasound imaging systems, and more particularly to ultrasound systems having a curved linear array probe that can operate in continuous wave Doppler mode and other imaging modes. Background Technology

[0002] Diagnostic ultrasound can be used to image the body's anatomical structures by generating two-dimensional and three-dimensional anatomical images. It can also be used to measure and display the characteristics of blood flow using Doppler techniques. Flow velocity is a function of the phase shift between emitted and received ultrasound waves. Doppler information can be displayed anatomically (e.g., using color flow) and displayed spectrally using a rolling spectrum of flow velocities. A common technique used for color flow imaging is pulse-wave Doppler, which periodically and repeatedly samples blood flow at the locations where it occurs. The samples acquired from each location in the image field over time (called an ensemble) are processed by Fourier transform to estimate the flow characteristics occurring at each location over time. These flow measurements are then converted into color values ​​to be displayed anatomically in conjunction with the anatomical images; for example, different shades of color depict different blood flow velocities. Pulse-wave Doppler flow measurements from selected anatomical locations (called sample volumes) can also be displayed as a continuous rolling spectrum of flow as a function of time, which, for example, depicts the peak and minimum flow velocities during each cardiac cycle.

[0003] Another Doppler technique used to measure blood flow is continuous wave (CW) Doppler. Unlike pulsed Doppler, CW Doppler signals are transmitted and received continuously. Transmission occurs from one aperture of the transducer, and reception occurs from the other. A disadvantage of CW Doppler is that while pulsed Doppler provides distance information from the time of flight of ultrasound pulses to and from the target area, such ranging is impossible when Doppler waves are transmitted and received continuously. The advantage of CW Doppler is its ability to measure high flow velocities and velocity variations without ambiguity, as it does not suffer from aliasing like pulsed wave Doppler when the pulse rate does not meet the Nyquist sampling criterion for high flow velocities present at the target. Therefore, CW Doppler is highly practical for situations involving narrow and reflux flows, characterized by high flow velocities in the meter-per-second range.

[0004] Different types of ultrasound probes (e.g., linear arrays, phased arrays, etc.) are used for imaging and diagnosis of conditions in different regions of the body. Widely used in abdominal and obstetric imaging is the curved linear array probe, where the array elements are arranged in outwardly convex arcs rather than straight (flat) lines. The curvature of the array physically, rather than entirely through the phasing of the elements, provides some of the beam manipulation, thus reducing the electronic delay requirements of the ultrasound system and providing a larger field of view, including a larger field of view at the skin line. Because abdominal and obstetric imaging are typically performed at greater depths within the body than in more peripheral examinations, it is desirable to reduce the image noise factor as much as possible, resulting in clearer images from the ultrasound signal attenuated by the greater depth of travel. One way to reduce image noise, or clutter, is to reduce ultrasound beam sidelobe clutter by decreasing the magnitude of the transducer sidelobes. This can be done by using a larger number of smaller elements in the array, where the smaller pitch of the elements provides the desired sidelobe reduction. This presents a problem when it is desired to increase the number of transducer elements beyond the number of channels in the ultrasound system's beamformer. This dichotomy is achieved by multiplexing the transducer elements, such that at any given time only a selectable subset of all the transducer elements is connected to the system beamformer. This presents a challenge for ultrasound system designers in configuring the multiplexing to achieve efficient CW Doppler diagnostics and other scanning modes in ultrasound systems where the number of beamformer channels is less than the number of array transducer elements. Summary of the Invention

[0005] According to the principles of the present invention, an ultrasound diagnostic imaging system is described having a linear array probe with multiple transducer elements, the number of transducer elements exceeding the number of channels in the system beamformer, and the ultrasound diagnostic imaging system capable of performing CW Doppler analysis. The linear array probe (which may be curved or flat) includes multiple multiplexers that selectively couple specific elements from the array to the ultrasound system, and thus to channels of the system beamformer. While some elements of the array transducers are multiplexed, others are not. When the array probe is operated to perform CW Doppler analysis, the unmultiplexed transducer elements are used for both the transmit and receive apertures. In other probe modes, both multiplexed and unmultiplexed elements can be used for imaging.

[0006] A preferred ultrasound system for performing CW Doppler analysis includes a linear array transducer probe having a given number of transducer elements arranged in a curved arc. Some of the transducer elements are multiplexed to a single multiplexer terminal, while other transducer elements are not multiplexed. A system beamformer has multiple beamformer channels, fewer than the given number of transducer elements in the curved arc of the curved array probe. A B-mode image processor is coupled to the system beamformer, and a Doppler processor is coupled to the system beamformer. A display processor is coupled to the B-mode image processor and the Doppler processor and is adapted to generate B-mode images and / or CW spectral Doppler images for display. A display is coupled to the display processor. The B-mode image is generated based on signals generated by the curved array probe using at least some of the multiplexed transducer elements, and the CW spectral Doppler image is generated based on signals generated by the curved array probe using unmultiplexed elements.

[0007] The method of the present invention for performing CW Doppler analysis includes: scanning a target anatomical structure using a linear array transducer probe to acquire a B-mode image, the array transducer comprising multiple multiplexed transducer elements and multiple unmultiplexed transducer elements, the multiplexed and unmultiplexed elements being coupled to a beamformer having fewer channels than the number of transducer elements in the transducer array; adjusting a Doppler line over the image to intersect the target in the B-mode image; adjusting a sample volume cursor over the target in the B-mode image; and initiating CW Doppler signal acquisition using elements of the unmultiplexed array transducer. Attached Figure Description

[0008] In the attached diagram:

[0009] Figure 1 The illustration shows a curved array ultrasonic probe constructed according to the principles of the present invention.

[0010] Figure 1 a schematic diagram Figure 1 The operation of the probe multiplexer.

[0011] Figure 2 The illustration shows the elements of the curved array transducer of the present invention and its aperture for use with CW Doppler.

[0012] Figure 3 The illustration shows the display of the ultrasound system of the present invention, including B-mode image and rolling Doppler display.

[0013] Figure 4 The illustration shows beams transmitted and received from the curved array transducer of the present invention, as well as Doppler lines shown on an ultrasound system display for CW Doppler procedures.

[0014] Figure 5 An ultrasound system configured according to the principles of the present invention is illustrated in block diagram form.

[0015] Figure 6 The illustration depicts a method for performing image-guided CW Doppler measurements according to the principles of the present invention. Detailed Implementation

[0016] First refer to Figure 1 The image shows a curved array ultrasound probe 10. In use, the probe is held by a handle (bottom) portion, and a curved array transducer 12, covered by a polymer lens material, presses against the body of the subject during scanning. The curved array transducer is typically coupled to a mating backing in the form of a printed circuit board (PCB) 14, to which the array elements are electrically connected. Alternatively, flexible circuitry behind the array can be electrically connected. Multiple multiplexer integrated circuits 52 are located on the PCB or flexible circuitry. The number of multiplexer IC modules required depends on the module's package density and the number of elements in the multiplexed curved array. Figure 1 Figure a shows a schematic diagram of a multiplexer. It should be noted that the switching arms of the multiplexer (as indicated by the arrows) can be configured to couple transducer elements coupled to terminal A or transducer elements coupled to terminal B to a common terminal Q. The common Q terminal of multiplexer 52 is coupled to a channel of the system beamformer via probe cable 60, and terminals A and B of the multiplexer are coupled to elements of the curved array transducer. Elements of the curved array that are not multiplexed are coupled to a channel of the beamformer via conductive traces on the PCB or flexible circuitry and the conductors of cable 60. The probe cable is connected to PCB 14 via a connector at the near end 54 of the PCB.

[0017] Figure 2The illustration shows how the elements of a curved array transducer are used for scanning in a preferred embodiment of the invention. The illustrated curved array transducer has 160 elements, numbered sequentially from right to left along the curved array, starting with element 0 and ending with element 159. A vertical dashed line defines the center of the array. When operating in CW Doppler mode, two apertures of the array are used, one for transmission and the other for reception. One aperture is formed by elements 32 to 75, and the other aperture is formed by elements 84 to 127. The allocation of the CW apertures for transmission or reception depends on which side of the array the target for CW analysis is located on (to the left or right of the dashed center line). If the target is to the left of the center, the aperture formed by elements 84-127 is used for transmission as indicated by arrow 72a, and the aperture formed by elements 32-75 is used for reception as indicated by arrow 72b. When the target is to the right of the center, the aperture allocation for transmission and reception is reversed, as indicated by transmission arrow 74a and reception arrow 74b. Therefore, transmission occurs from the aperture on the side of the array where the target is located.

[0018] Elements 76-83 at the center of the array are inactive during CW scanning. They are used to provide isolation between the CW apertures on either side of these center elements. Elements 0-31 and 128-159 are not used during CW scanning.

[0019] According to the principle of the present invention, for use Figure 2 In the example, the array elements of CW apertures 32-75 and 84-127 are directly coupled to the conductor of probe cable 60, and thus to the channels of the system beamformer; they are not coupled to the beamformer via a multiplexer. Since the total number of elements used for the CW transmit and receive apertures (88 in this example) is less than the number of channels of the system beamformer (128 channels), a multiplexer is not required when performing CW Doppler scans.

[0020] During other scanning modes, when the entire array of 160 elements is available, multiplexer 52 is used to couple the necessary elements to the 128-channel system beamformer. For example, when scanning a mode B image, 100 elements can be used to scan each line of the mode B image. Elements 0-99 are used to generate the first line on the right, then elements 1-100 are used to form the next adjacent line, then elements 2-101 are used to form the third line, and so on across the array. A suitable multiplexer configuration for a linear array probe operating in this manner would be to multiplex only elements 0-31 and 120-159, while the other elements are directly coupled to the beamformer channels. The multiplexer and elements are arranged such that two elements that are not operating simultaneously in an aperture are coupled to the same multiplexer. The appropriate coupling for the CW and B-mode scans described above would be to couple elements 0 and 128 to the first multiplexer, elements 1 and 129 to the second multiplexer, elements 2 and 130 to the third multiplexer, and so on. A scan sequence of 100 adjacent array elements for each B-mode line can then be executed without conflict during multiplexer operation.

[0021] Figure 3 The illustration shows a curved array ultrasound system performing both B-mode imaging and Doppler flow analysis. The B-mode sector display 100 shows the anatomical structure with a vessel 108 passing through it. The image is generated by a curved array transducer 12' positioned at the top of the image during scanning. The sonographer positions a Doppler line 102 above the image, which intersects the vessel at the desired target location. The Doppler line can be moved left and right, extending from the curved array position 12'. The sonographer then moves the sample volume cursor 104 until it is positioned above the point in the anatomy where blood flow is to be evaluated. The blood flow cursor 106 is then typically positioned in a straight line with the direction of blood flow by tilting the blood flow cursor 106 until it is parallel to the wall of the vessel at the sample volume. The illustrated set of image cursors can be used for both CW Doppler and pulsed Doppler spectral scanning.

[0022] Once the pre-alignment is complete, the sonographer presses the “CW” button on the ultrasound system’s control panel to initiate CW Doppler operation. The Mode B image 100 is then frozen on the monitor, and the CW Doppler display 110 begins to scroll across the screen. Although the Doppler line can give the impression that the Doppler beam is emitted downwards along Doppler line 102 into the sample volume, with reflected waves returning to the transducer along that line, this is not what actually happens when using separate transmit and receive apertures. Figure 4A more precise representation of what happens during the scan is illustrated. In this example, sample volume 104 is to the right of the center of the curved array 12, so the right-hand CW aperture 70a is used for transmission. The CW Doppler waves are continuously transmitted and phase-manipulated, such that the beam center is guided as indicated by the dashed arrow 80t. Some of the reflected Doppler waves return toward the left-hand receiving aperture 70b of the curved array 12 and are received along the beam center 80r. During CW Doppler operation, Doppler waves are continuously transmitted from CW aperture 70a and continuously received by CW aperture 70b.

[0023] Now for reference Figure 5 The diagram illustrates an ultrasound diagnostic imaging system constructed according to the principles of the present invention. A linear array transducer 12 (illustrated here as a curved linear array) is provided in the ultrasound probe 10 for emitting ultrasound waves and receiving echo information. The transducer array 12 can be a one-dimensional or two-dimensional array of transducer elements capable of scanning in two or three dimensions (e.g., both elevation (in 3D) and azimuth). The probe 10 comprises, as shown in the diagram... Figure 1The multiplexer 52 shown multiplexes the couplings of some of the array elements to the system beamformer, while other elements (including those with CW Doppler apertures) are not multiplexed. The transducer array 12 and the elements of the multiplexer are coupled to the system beamformer 20 via probe cable 60 and probe connector 22 at the cable end, and can be used in the probe prior to an optional beamformer that controls the transmission and reception of signals by the array elements. The microwave beamformer is capable of at least partially beamforming signals received by groups or “patches” of transducer elements, as described in U.S. Patents 5,997,479 (Savord et al.), 6,013,032 (Savord), and 6,623,432 (Powers et al.). The main system beamformer 20 is coupled to the probe cable via a transmit / receive (T / R) switch 16 that switches between transmit and receive. The transmission of the ultrasonic beam from transducer array 12, the reception of the echo signal by system beamformer 20, and the operation of multiplexer 52 are all controlled by controller 18, which receives input from the user-to-user interface or control panel 38. Transmission characteristics controlled by the transmission controller include the number, spacing, amplitude, phase, frequency, polarity, and diversity of the transmitted waveform. The beam formed in the pulse transmission direction can be manipulated directly forward from the transducer array, or manipulated at different angles on either side of the non-manipulated beam direction to obtain a wider sector field of view. For some applications, unfocused plane waves can be used for transmission, and in this case, the received beam can simultaneously interrogate the entire field of view. Most relatively small array length 1D array probes (e.g., 128-element arrays) do not use microwave beamformers but are driven from and directly responsive to the main beamformer.

[0024] Beamforming is performed on the echoes received by the transducer elements of the array during imaging and CW Doppler operation by appropriately delaying them and then combining them in the system beamformer 20 under the guidance of controller 18. The coherent echo signals undergo signal processing performed by signal processor 26, which includes filtering by digital filters and noise reduction such as by spatial or frequency recombination. The filtered echo signals are coupled to a quadrature bandpass filter (QBP) 28. The QBP performs three functions: band-limiting the RF echo signal data, generating in-phase and quadrature pairs (I and Q) of the echo signal data, and decimating the digital sampling rate. The QBP comprises two separate filters, one generating in-phase samples and the other generating quadrature samples, each filter being formed by multiple multiplier-accumulators (MACs) implementing FIR filters. The signal processor can also shift the frequency band to a lower or baseband frequency range, and the QBP can also do so. For example, the digital filters of signal processor 26 can be filters of the type disclosed in U.S. Patent 5833613 (Averkiu et al.).

[0025] The coherent echo signal, after beamforming and processing, is coupled to a B-mode processor 30, which generates a B-mode image of structures (such as tissues) in the body. The B-mode processor calculates in the form of (I 2 +Q 2 ) ½ The amplitude of the echo signal is used to perform amplitude (envelope) detection of the I and Q signal components of the quadrature demodulation. The quadrature echo signal components are also coupled to the Doppler processor 34. The Doppler processor 34 uses a phase comparator or a Fast Fourier Transform (FFT) processor for pulsed Doppler to estimate the phase shift between the transmitted and received Doppler signals at and near the sample volume. The Doppler frequency shift is proportional to the flow velocity at the sample volume (including fast jets from stenotic or regurgitated valves). For color Doppler images, the estimated Doppler flow value at each point in the blood vessel is wall-filtered and converted to a color value using a lookup table. The wall filter has an adjustable cutoff frequency, above or below which motion is rejected, such as low-frequency motion of the vessel wall when imaging flowing blood. The B-mode image signal and pulsed Doppler flow values ​​are coupled to a scan converter 32, which converts the B-mode and Doppler samples from their acquired R-θ coordinates to Cartesian (x, y) coordinates for display in a desired format, such as a linear or sector display format for anatomical images, or a scrolling display of continuously received and processed Doppler values ​​for spectral display. For anatomical images, either the B-mode image or the Doppler image can be displayed separately, or both can be shown together in anatomical registration, where color Doppler overlays illustrate blood flow in tissues and vessels in the image, such as... Figure 3As shown. Another display possibility is to show side-by-side images of the same anatomical structures that have been processed differently. This display format is useful when comparing images. Spectral Doppler displays can also be shown alone or in combination with anatomical images.

[0026] Spectral and image data generated by the B-mode processor 30 and the Doppler processor 34 are coupled to an image data memory 36, which is stored in a memory location addressable according to the spatial location from which image values ​​are acquired. The spectral Doppler data is stored according to the time of acquisition of the spectral Doppler data. Image data from the 3D scan can be accessed by a volumetric renderer 42, which converts the echo signals of the 3D dataset into a projected 3D image, as described in U.S. Patent 6,530,885 (Entrekin et al.). The 3D image generated by the volumetric renderer 42, the 2D image generated by the scan converter 32, and data for lines used in spectral display are coupled to a display processor 48 for further enhancement, buffering, and temporary storage for display on an image display 40. The display processor also includes a graphics generator for generating lines and graphics, such as... Figure 3 The cursor shown is used for display in conjunction with ultrasound images.

[0027] exist Figure 6The diagram illustrates a method for performing CW Doppler analysis on an object. At initiation step 90, the object's anatomy is scanned using a linear array transducer probe to image the target region. Preferably, the linear array transducer is a curved array with a large number of finely pitched elements, such as 160 or 192 elements. The probe may contain a single curved row of transducer elements or multiple adjacent rows for operation in the height dimension. Coherent image values ​​are generated by a system beamformer for display. When the elements of the curved array are multiplexed, the system beamformer may have fewer channels than the number of transducer elements in the array, such as a standard 128-channel beamformer. Both multiplexed and unmultiplexed elements can be used for imaging. When the target is in view in step 92, the sonographer adjusts the Doppler line on the image so that it intersects the anatomical target, such as a blood vessel or heart valve. Then, in step 94, the sonographer adjusts the sample volume cursor to be positioned above the target by sliding it along the Doppler line. In step 96, the sonographer adjusts the angle correction cursor to align it with the flow direction, allowing Doppler values ​​to be corrected while taking into account the angle between the flow direction and the beam direction. Once the target is clearly in the view and has been targeted as described above, the “CW” button on the ultrasound system is pressed in step 98 to initiate CW Doppler acquisition and the generation of a scrolling spectrum display. Because the anatomical image is frozen on the ultrasound monitor during CW Doppler acquisition, it is important for the sonographer to keep the array probe stable so that the beam remains on the target. If probe or patient movement causes the target acquisition to be lost, the sonographer can press the “Image” button on the ultrasound system to return to imaging mode, allowing the probe to be re-aimed to acquire the target again and reset the pattern on the image.

[0028] Although the above method describes steps that can be performed by a sonographer or other user, the scope of the method also anticipates that one or more of steps 90-98 can be performed automatically under the control of the system's computer processor and software, such as image recognition software enabled by a pre-trained model. Target locations for CW Doppler analysis can be continuously tracked and targeted via speckle tracking.

[0029] Depending on the ultrasound designer's objectives, the concepts of this invention can be applied in various ways. As mentioned above, the linear array transducer can be a curved linear array or a flat linear array. Curved linear arrays offer the benefits of a larger field of view and reduced manipulation delay. Although... Figure 1 The example illustration shows a multiplexer 52 located within the transducer housing of the probe, but alternatively, the multiplexer can be positioned within the sheath of connector 22 at the other end of the cable. Other variations will be readily apparent to those skilled in the art of ultrasonic design.

[0030] It should be noted that the ultrasonic system applicable to embodiments of the present invention (especially) Figure 5 The component structure of an ultrasound system can be implemented in hardware, software, or a combination thereof. Various embodiments and / or components of the ultrasound system, such as beamformers, signal processors, mode-B processors, and Doppler processors, or components, processors, and controllers thereof, can also be implemented as part of one or more computers or microprocessors. The computer or processor may include computing devices, input devices, display units, and interfaces, such as for accessing the Internet. The computer or processor may include a microprocessor. The microprocessor may be connected to a communication bus, for example, to access a PACS system or data network to import images. The computer or processor may also include memory. The computer or processor may also include storage devices, which may be hard disk drives or removable storage drives, such as floppy disk drives, optical disk drives, solid-state thumb drives, etc. Storage devices may also be other similar modules for loading computer programs or other instructions into the computer or processor.

[0031] As used herein, the terms “computer” or “module” or “processor” or “workstation” can include any processor-based or microprocessor-based system, including systems using microcontrollers, reduced instruction set computers (RISC), ASICs, logic circuits, and any other circuitry or processor capable of performing the functions described herein. The examples above are merely illustrative and are therefore not intended to limit the definition and / or meaning of these terms in any way.

[0032] A computer or processor executes a set of instructions stored in one or more storage elements to process input data. Storage elements can also store data or other information as desired or required. Storage elements can take the form of information sources within the machine or physical memory elements.

[0033] The instruction set of an ultrasound system, including those described above that control the acquisition, processing, and transmission of ultrasound images, can include various commands that instruct a computer or processor, acting as a processing machine, to perform specific operations, such as the methods and processes of various embodiments of the present invention. The instruction set can take the form of a software program. The software can take various forms (such as system software or application software) and can be embodied in a tangible, non-transient computer-readable medium. Furthermore, the software can take the form of a collection of individual programs or modules, program modules within a larger program, or portions of program modules. The software can also include modular programming in the form of object-oriented programming. The processing of input data by the processing machine can be in response to operator commands, the results of previous processing, or a request made by another processing machine.

[0034] Furthermore, the limitations of the following claims are not drafted in a module plus function format and are not intended to be interpreted based on paragraph 6 of 35 U.SC112 unless and until such a claim limitation expressly uses the phrase “module for…” followed by a statement of function without further structure.

Claims

1. An ultrasound diagnostic imaging system for performing CW Doppler analysis, comprising: A linear array transducer probe (10) having a given number of transducer elements arranged in a flat row or a curved arc, some of which are multiplexed to a single multiplexer terminal (Q), and the other transducer elements are not multiplexed. The system beamformer (20) has multiple beamformer channels, which are fewer than the given number of transducer elements of the linear array transducer; Mode B processor (30), which is coupled to the system beamformer; Doppler processor (34), which is coupled to the system beamformer; Display processor (48), coupled to the B-mode processor and the Doppler processor and adapted to generate B-mode images or CW spectral Doppler images for display; and The display (40) is coupled to the display processor. The B-mode image is generated by the linear array probe using signals generated by multiplexed transducer elements, and the CW spectral Doppler image is generated by the linear array probe using signals generated by unmultiplexed elements.

2. The ultrasonic diagnostic imaging system of Claim 1, wherein, The multiplexed transducer elements are multiplexed in pairs to one or more multiplexers, each of the one or more multiplexers having a common terminal (Q) coupled to a beamformer channel.

3. The ultrasound diagnostic imaging system according to claim 2, wherein, The system beamformer is coupled to receive signals from transducer elements that are multiplexed during the generation of the B-mode image.

4. The ultrasound diagnostic imaging system according to claim 3, wherein, The system beamformer is also coupled to receive signals from transducer elements that are not multiplexed during the generation of the B-mode image.

5. The ultrasound diagnostic imaging system according to claim 2, wherein, The system beamformer is coupled to transmit and receive signals using only transducer elements that are not multiplexed during CW Doppler analysis.

6. The ultrasound diagnostic imaging system according to claim 5, wherein, The system beamformer is coupled to a first set of transducer elements including a transmit aperture for transmitting during CW analysis, and is coupled to a second set of transducer elements including a receive aperture for receiving during CW analysis.

7. The ultrasound diagnostic imaging system according to claim 6, wherein, The transmitting aperture is located on one side of the linear array, and the receiving aperture is located on the other side of the linear array.

8. The ultrasound diagnostic imaging system according to claim 7, wherein, The transmitting aperture and the receiving aperture can be selectively changed depending on which side of the linear array the target is located on.

9. The ultrasound diagnostic imaging system according to claim 8, wherein, The emission aperture can be selectively located on one side of the linear array where the target is located.

10. The ultrasound diagnostic imaging system according to claim 2, wherein, The linear array transducer is a curved array comprising at least 160 transducer elements, and the system beamformer comprises 128 beamformer channels.

11. A method for performing CW Doppler analysis, comprising: A linear array transducer probe is used to scan a target anatomical structure to acquire B-mode images. The linear array is either curved or flat and includes multiple multiplexed and multiple unmultiplexed transducer elements. The multiplexed and unmultiplexed elements are coupled to a beamformer having fewer channels than the number of transducer elements in the array transducer. Adjust the Doppler lines to intersect with the target in the B-mode image; Adjust the sample volume cursor above the target in the B-mode image; and The CW Doppler signal acquisition is initiated using the unmultiplexed elements of the array transducer.

12. The method according to claim 11, wherein, Using the unmultiplexed elements of the linear array transducer to initiate CW Doppler signal acquisition also includes: using only the unmultiplexed elements of the linear array transducer to perform CW Doppler signal analysis.

13. The method according to claim 12, wherein, Initiating CW Doppler signal acquisition also includes: transmitting using the first set of transducer elements of the linear array transducer, and receiving using the second set of transducer elements of the linear array transducer.

14. The method according to claim 13, wherein, A set of transducer elements used for transmitting includes a transmitting aperture located on one side of the linear array, and a set of transducer elements used for receiving includes a receiving aperture located on the other side of the linear array.

15. The method of claim 14, further comprising adjusting an angle correction cursor on the B-mode image before initiating CW Doppler signal acquisition.

Images