3D Color Doppler for Ultrasonic Volume Flow Measurement

Abstract

An ultrasound imaging system is used to measure volume flow. An ultrasound probe operating in biplanar mode is used to simultaneously acquire vessels in a longitudinal view in a first Doppler image and in a transverse view in a second Doppler image. Volume flow is calculated from the transverse view of the vessels. The plane of the second Doppler image is aligned with the Doppler angle of the first Doppler image so that the angle correction determined for the first Doppler image can be used for angle correction in the volume flow calculation.

Description

Technical Field

[0001] The present invention relates to a medical diagnostic ultrasound system, and more particularly to an ultrasound system that generates a quantified measurement of the volume flow of blood through the heart or blood vessels.

Background Art

[0002] Ultrasound has long been used to evaluate various parameters of blood flow in the heart and vasculature using the Doppler principle. The basic Doppler response is flow velocity, which can in turn be used to determine additional characteristics of blood flow. One characteristic that is important to a cardiologist is the volume flow of blood through a blood vessel. Early attempts to estimate volume flow consisted of multiplying a measurement of the average velocity of blood flow by the nominal cross-sectional area of the blood vessel. However, these early attempts had drawbacks due to the need to make several estimates. One estimate is that the vessel lumen is circular. Another estimate is the estimation of the average velocity from a single Doppler measurement or from a qualitative evaluation of spectral Doppler data. Also, the velocity measurement must be corrected for the angle between the ultrasound beam direction and the direction of flow. Yet another consideration is the laminar flow profile in the presence of stenosis.

Summary of the Invention

Problems to be Solved by the Invention

[0003] The pulsatility of arterial flow causes further troublesome problems. While venous flow is substantially constant, arterial flow is constantly changing over the cardiac cycle. Thus, standard techniques often lack user independence and reproducibility. Some of these requirements have been alleviated by the advent of 3D ultrasound for evaluating flow states, particularly the ability of 3D ultrasound to collect volumetric blood flow information. Using 3D imaging, it is possible to image the complete vascular lumen and collect a series of 3D image datasets for later playback and diagnosis. When data on the complete volumetric flow in a blood vessel is collected in the dataset, the image data can be examined during post-collection diagnosis to evaluate the flow profile. Different 2D image planes can be extracted from the 3D data in multi-planar reconstruction (MPR), thereby allowing examination of the image plane in the desired orientation through the blood vessel. 3D imaging thus addresses many of the static imaging challenges that are problematic for 2D flow estimation. However, a large amount of time is required to collect Doppler data in 3D, which can reduce the temporal accuracy when analyzing volumetric flow. Therefore, it is desirable to develop more robust techniques for accurately evaluating volumetric flow in the presence of flow pulsatility and an unstable heartbeat. Additionally, it is desirable to improve the accuracy and reliability of Doppler angle measurements required to increase the accuracy of Doppler flow velocity values.

Means for Solving the Problem

[0004] A diagnostic ultrasound system that uses a 3D imaging probe to perform volume flow measurements in accordance with the principles of the present invention will be described. The probe is preferably a two-dimensional matrix array probe that operates in a biplane mode. One of the imaging planes is operated to collect a long-axis view of the blood vessel where the volume flow is to be measured. The plane of the other biplane image is aligned with the beam direction of the first image and obliquely images the target blood vessel in the transverse view. The beam direction of the longitudinal cross-sectional image and the flow direction seen in the long-axis view thus determine the Doppler angle for Doppler angle correction of the velocity values obtained from the transverse image. Since only two planar images need to be collected instead of a complete 3D volume collection, the Doppler data collection rate is relatively high. The Doppler angle correction directly results from the Doppler angle found for the longitudinal image. Therefore, known methods of volume flow measurement, such as the Gaussian area integration method, can be used with high accuracy and reproducibility.

[0005] In the method of the present invention, an ultrasonic diagnostic system is used to perform an ultrasonic examination to measure volume flow. The scan is performed using an ultrasonic probe operating in a biplane mode to collect a first Doppler image of the target blood vessel in the long-axis view. The scan is performed using the ultrasonic probe in a biplane mode to simultaneously collect a second Doppler image of the target blood vessel in the transverse view within an image plane aligned with the Doppler angle of the first image. The two images are displayed simultaneously. Angle correction is performed according to the Doppler beam direction and the flow direction of the first Doppler image. The volume flow is calculated from the data of the second Doppler image using the angle correction determined from the first Doppler image.

Brief Description of the Drawings

[0006]

Figure 1

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Mode for Carrying Out the Invention

[0007] Referring initially to FIG. 1, an ultrasonic image is shown that depicts the collection of Doppler data for volume flow assessment using pulsed Doppler with uniform ultrasonic irradiation. This is available on most commercial ultrasonic systems and requires only a 1D array transducer, and is perhaps the most widely accepted method in clinical use. The probe operates to alternately collect B-mode echoes for generating structural images of tissue and vessels, and Doppler echoes for spatial flow velocity depiction within the color box. This method uses pulsed Doppler ultrasound, whereby a long Doppler sample is placed at an angle to the vessel of interest, and volume flow is calculated from the time-average velocity of blood flow. FIG. 1 shows an ultrasonic image of this method, depicting the target vessel 70 in which volume flow is to be measured. Doppler collection is performed within the color box 80, which appears to be inclined from top left to bottom right, which is the direction of Doppler beam transmission, and the Doppler gate line 82 is aligned with this beam direction. The color box is Doppler scanned at an angle indicated by parallel scan lines, a technique known as steered linear scanning. The break distance of the Doppler gate line 82 is such that the break spans the vessel 70, establishing a long Doppler sample across the lumen of the vessel. An adjustable flow cursor 84 is positioned over the vessel, with the upper and lower parts of the cursor located at the vessel walls, and the intermediate horizontal line aligned with the direction of flow. The angle between the Doppler gate line 82 and the horizontal line of the flow cursor 84 is the angle used for Doppler angle correction.

[0008] However, although still widely used clinically, this method is known to be inaccurate and imprecise due to several incorrect assumptions and measurement dependencies. See, for example, R.W. Gill, Measurement of blood flow by ultrasound: accuracy and sources of error, Ultrasound in Medicine and Biology, vol. 11(4), pages 625 - 641 (1985). One implicit assumption in that method is that the blood vessel is uniformly irradiated with ultrasound by the ultrasound beam. Since the ultrasound beam is generally smaller in height than the blood vessel, this assumption is generally not valid. If a uniform ultrasound irradiation cannot be assumed, a simplifying assumption that the blood vessel cross - section is circular must be made. This generally only applies to the aorta and usually does not apply to veins. Another implicit assumption is that the time sampling rate of the flow is fast enough to capture the variations in flow velocity (and thus volume) throughout the cardiac cycle. In the case of the pulsed Doppler method, the time sampling rate of a 1D array probe is generally sufficient even for highly pulsatile flow, so this assumption is usually valid.

[0009] Furthermore, the accuracy of the measurement depends greatly on accurately determining the Doppler angle and the blood vessel diameter. The blood vessel diameter is used to calculate the blood vessel cross - sectional area by the formula area = πr 2 and then the cross - sectional area is determined by multiplying that area by the flow velocity corrected by the Doppler angle to estimate the volume flow. Thus, the accuracy of the blood vessel diameter is important. Accurately determining the Doppler angle is relatively easy for straight superficial blood vessels but more difficult for curved or deeper blood vessels. Since the blood vessel diameter is used to determine the cross - sectional area by the above - mentioned squared law, the volume measurements are particularly sensitive to the blood vessel diameter measurements.

[0010] Other methods for evaluating volumetric flow that are less dependent on these assumptions and measured values have been proposed. One such method is the Gaussian surface integral method that uses 3D / 4D color Doppler and Gauss's law. Using this method, the volumetric flow is determined by integrating (summing) all color flow voxels over a coronary surface that intersects the target vessel and is perpendicular to the 3D (or 4D) color Doppler beam. See Measurement of volumetric flow by Kripfgans et al., J. Ultrasound Med. vol. 25, pages 1305 - 1311 (2006). See also U.S. Patent No. 6,780,155 (Li). Since the coronary plane intersects the entire vessel, there is no assumption of uniform ultrasound irradiation and no assumption that the vessel is circular. Also, since the transmitted ultrasound beam is perpendicular to each point on the surface, there is no need to measure either the Doppler angle or the vessel diameter. Figure 2a shows a vessel 70 intersecting a Gaussian surface 50. The thin plane 52 of the surface is scanned by transmitting a Doppler beam from a 2D array transducer 54 that electronically steers its Doppler beam on the surface 50 where it intersects the vessel 70. The flow image 76 is thereby rendered as the cross-sectional surface of the curved cross-section 58 through the vessel 70. As described in the above U.S. Patent No. 6,780,155, the flow image 76 can be projected onto the flat plane 72 as a B-mode image 56. The vessel lumen 62 in the B-mode image can be segmented by a circle 64 or other shape outside the vessel wall 60, and the color voxels within the segmented area are then summed to generate an estimate of the volumetric flow. Correction should be made for color voxels in the vessel wall that have only partial flow, and one way to do this is by normalizing the velocity estimate using the power (intensity) in the Doppler signal, often known as partial volume correction (see Kripfgans et al. above).

[0011] This is an excellent method for measuring volume flow, but the volume rates possible using 3D / 4D color Doppler are generally limited, thereby causing undersampling of temporal information and errors in flow volume calculations, presenting challenges in measuring pulsatile flow. In order to accurately estimate the Doppler velocity at each point on the Gaussian surface, each point on the Gaussian surface must be sampled multiple times by multiple transmissions with individual Doppler beams. To mitigate this limitation, related methods have been developed that collect information over multiple cardiac cycles and then average to obtain an average volume flow, or, when the cardiac cycle is accurately known, reconstruct a single cardiac cycle from multiple cycles. However, these techniques increase the acquisition time and make the method less robust due to the required time sampling time.

[0012] Another method that has similarities to the Gaussian area integral method has been proposed by Picot et al. See Picot et al., Rapid volume flow rate estimation using transverse colour Doppler imaging, Ultrasound in Medicine and Biology, vol. 21(9), pp. 1199 - 1209 (1995). In this method, instead of extracting a coronal plane from a 3D colour Doppler volume, the conventional 1D array transducer is angled towards the blood vessel such that the scanning plane of the conventional 1D array transducer and the 2D colour image intersect the blood vessel at an oblique but transverse angle. Figure 4 shows an ultrasonic image of a blood vessel 70 scanned in this way within a colour box 80. Similar to the Gaussian area integral method, all the colour Doppler pixels within the colour box 80 are summed and a correction is applied to the partially filled pixels at the edge of the blood vessel. Again, there are no assumptions about the flow profile or blood vessel geometry. One major advantage compared to the Gaussian area integral method is that the two - dimensional colour frame rate is generally much higher than the 3D / 4D colour volume rate, and thus the appropriate temporal sampling for pulsatile flow is significantly improved. However, one drawback compared to the Gaussian area integral method is that the Doppler angle, which is extremely difficult to obtain from a transverse image, must be known. Picot et al. describe a sophisticated probe holder that allows the same blood vessel to be interrogated from two angles, thereby making it possible to eliminate Doppler angle dependence, but such a probe holder is cumbersome and not practical for clinical use.

[0013] According to the principles of the present invention, to measure volume flow, an ultrasonic probe with a two-dimensional matrix array transducer is operated in a biplane mode. In the biplane mode, two image planes are scanned simultaneously in an interleaved pattern. The biplane mode can be performed by a mechanical probe that moves a 1D transducer array to scan two image planes of a volumetric region, as described in U.S. Patent No. 6,443,896 (Detmer), but it is preferred to use a 2D matrix array probe in which the planes are scanned electronically rather than mechanically, as described in U.S. Patent No. 6,709,394 (Frisa et al.). Further, as described in U.S. Patent No. 7,645,237 (Frisa et al.), it is possible to perform color flow imaging in the biplane mode, whereby a color box is scanned to collect color Doppler data within each of the biplane image planes. Ultrasonic systems and probes capable of performing color flow scanning of biplane images are commercially available, such as the xMATRIX family of probes available on Philips Healthcare ultrasonic systems. In one implementation of the present invention, a scan in biplane mode is performed to generate two real-time images that are perpendicular to each other and include color Doppler data. This enables the simultaneous generation of a longitudinal axis view and a transverse view of a blood vessel. As will be explained below, the longitudinal axis image can be used to accurately measure the Doppler angle. The transverse color image intersects the blood vessel obliquely in the same manner as in Picot's method, and thus the same algorithm can be used to sum all the color pixels, but using the accurately known Doppler angle correction obtained from the longitudinal axis image, to estimate the volume flow.

[0014] One implementation of the present invention overcomes many of the limitations and drawbacks of previous methods for measuring volume flow. Compared to the pulsed Doppler method, one implementation of the present invention does not require a uniform ultrasound irradiation or an assumption of vascular geometry, and does not require measuring the blood vessel diameter, which is the biggest cause of inaccuracy in common pulse Doppler-based methods. Compared to the Gaussian area integration method, the technique of the present invention only needs to scan two image planes, and thus is more suitable for the very pulsatile flow found in many arteries, giving much better time sampling. Furthermore, since there is no need to attempt to improve the 3D volume frame rate, the spatial sampling is not impaired. With better spatial sampling, the representation of the flow profile is improved and the dependence on partial volume correction is reduced. Compared to the method of Picot et al., one implementation of the present invention makes it extremely easy to accurately measure the Doppler angle required for velocity correction.

[0015] The operation and application of one implementation of the present invention will be understood by referring to FIGS. 5 and 6. FIG. 5 shows a 2D matrix array transducer 54 that scans two bi-planes in front of the transducer, indicated by L and T. When all scan lines transmitted and received for one plane are perpendicular to the plane of the 2D array transducer, that plane extends perpendicular to the transducer as shown in this figure. When the scan lines are transmitted and received at an oblique angle with respect to the plane of the array transducer, the scan plane is tilted in the shape of a parallelogram due to the steered linear operation. In the example of FIG. 5, since the scan lines are transmitted and received at the front face of the array, the two bi-planes extend perpendicular to the transducer. The L plane and the T plane appear to intersect at a common intermediate scan line.

[0016] FIG. 6 shows two bi-planes of L and T that intersect the blood vessel 70 and are steered to scan the blood vessel 70. The L plane is inclined from the upper left to the lower right and is directed by probe operation toward the longitudinal center of the blood vessel 70, thereby generating a long-axis view of the blood vessel. As is well known, when the angle between the Doppler beam and the flow direction is 90°, since the cosine of 90° is 0, a measurable Doppler signal cannot be obtained. Therefore, the L scanning plane is tilted in a parallelogram orientation such that the scanning lines of the plane intersect the direction of blood flow in the blood vessel at a non-orthogonal angle. The T plane is aligned with one of the parallel scanning lines of the L plane and intersects the blood vessel 70 obliquely, thereby generating a transverse view of the blood vessel where the T image plane transects the blood vessel there. The Doppler angle of the T plane required for angle correction of Doppler velocity measurement is thus the angle at which the L plane is tilted, which can be easily known from the Doppler angle of the L plane and the easily observable flow direction in the long-axis view of the blood vessel.

[0017] As shown in FIG. 6, when scanning a blood vessel using a bi-plane probe, as shown in FIG. 7, a long-axis view and a transverse view of the blood vessel can be generated and displayed simultaneously. In this example, the bi-plane images are shown in parallel in a duplex display. The left image 90 is the long-axis view of the L scanning plane of FIG. 6, and the blood vessel 70 in the long-axis view bisecting the blood vessel 70 is shown. Inside the gray-scale (B-mode) image of the blood vessel and the surrounding tissue, there is a color box 80 scanned by the Doppler beam for the Doppler display of the material inside the box. Similar to the color box in FIG. 1, the color box 80 is tilted at an angle established by setting the tilt angle of the Doppler gate line 82. Similar to the previous drawings, the Doppler line has a flow cursor 84, and the user aligns the flow cursor 84 with the direction of flow in the blood vessel 70. The angle between the Doppler gate line 82 and the flow cursor 84 establishes the Doppler angle, which is the angle between the Doppler beams used to scan the color box 80 and the direction of blood flow. The Doppler angle is generally automatically recognized and recorded in a standard ultrasound system.

[0018] In one implementation of the present invention, an image 92 of a lateral view of a blood vessel 90 is scanned within a plane that is aligned with the angle of the color box 80. Generally, the image plane 90 and the image plane 92 are spatially perpendicular to each other. In this example, the plane of the image 92 is aligned with the Doppler gate line 82 of the image 90, and the two images spatially share the common location of their Doppler lines 82. As a result, the Doppler angle correction required for the flow velocity values in the lateral image 92 is the Doppler angle of the longitudinal cross-sectional view 90, which is the angle between the Doppler gate line 82 and the flow cursor 84, easily recognized in a typical commercial ultrasound system. The ultrasound system can then measure the volume flow by any of several known algorithms, such as the algorithm of Picot et al., in which the color pixel values of the blood vessel in the lateral view are angle-corrected and then summed to calculate the volume flow. Mathematically, this can be represented by Gauss's theorem, calculated as [Number] where Q is, for example, the volume flow in milliliters per second, v is the angle-corrected flow velocity, and the surface S is the Doppler portion of the cross-section passing through the blood vessel lumen in the lateral view 92. Further, with a typical commercial ultrasound system, the user can segment (outline) the portion of the image over which the Doppler velocity pixels are to be integrated. FIG. 7a presents an example of such a tool, namely, a circular template 78 that the user can move over the ultrasound image to appropriately size the ultrasound image and then specify the image region in which the Doppler value integration is to be performed. Such segmentation of the blood vessel lumen prevents the volume flow algorithm from, for example, erroneously including pixel values of adjacent blood vessels.

[0019] In FIG. 8, an ultrasonic system constructed in accordance with the principles of the present invention is shown in block diagram form. A transducer array 12 is provided in an ultrasonic probe 10 to transmit ultrasonic waves and receive echo information. The transducer array 12 is a two-dimensional array of transducer elements capable of scanning in three dimensions in both the elevation and azimuth angles. The transducer array 12 is thus capable of simultaneously scanning two bi-planes in a time-interleaved fashion. The transducer array 12 is coupled to a microbeamformer 14 in the probe that controls the transmission and reception of signals by the array elements. The microbeamformer is capable of at least partially beamforming the signals received by groups or “patches” of transducer elements, as described in U.S. Pat. No. 5,997,479 (Savord et al.), U.S. Pat. No. 6,013,032 (Savord), and U.S. Pat. No. 6,623,432 (Powers et al.). The microbeamformer is coupled by a probe cable to a transmit / receive (T / R) switch 16 that switches between transmission and reception and protects the main beamformer 18 from high energy transmit signals. Transmission of an ultrasonic beam from the transducer array 12 under the control of the microbeamformer 14 is directed by a beamformer controller 17 coupled to the T / R switch and the main beamformer 18, and the beamformer controller 17 receives inputs from user operations of a user interface or control panel 38. Among the transmission characteristics controlled by the transmit controller are the direction, number, spacing, amplitude, phase, angle, frequency, polarity, and divergence of the transmit waveform. The beam formed in the direction of a pulse transmission is steered straight from the transducer array, or at different angles on both sides of a non-steered beam for a wider sector view or for transmission at a selected Doppler angle.

[0020] Echoes received by successive groups of transducer elements are beamformed by appropriately delaying them and then combining them. The partially beamformed signals generated by the microbeamformers 14 from each patch are combined in the main beamformer 18, where the partially beamformed signals from the individual patches of transducer elements are combined to form a fully beamformed coherent echo signal. For example, the main beamformer 18 has 128 channels, each of which receives a partially beamformed signal from a patch of 12 transducer elements. In this way, signals received by more than 1500 transducer elements of a two-dimensional matrix array transducer can efficiently contribute to a single beamformed signal.

[0021] The coherent echo signal undergoes signal processing by the signal processor 20, which includes filtering by digital filters and noise and speckle reduction by spatial or frequency compounding, etc. The digital filter of the signal processor 20 can be, for example, a filter of the type disclosed in U.S. Patent No. 5,833,613 (Averkiou et al.). The echo signal is then coupled to the quadrature bandpass filter (QBP) 22. The QBP performs three functions: bandlimiting the r.f. echo signal data, generating in-phase and quadrature pairs (I and Q) of the echo signal data, and decimating the digital sample rate. The QBP comprises two separate filters, one generating in-phase samples and the other generating quadrature samples, each filter being formed by a plurality of multiplier-accumulators (MACs) implementing FIR filters.

[0022] The beamformed and processed coherent echo signals are combined into pairs for the image data processor. The B-mode processor 26 generates signal data for the B-mode images of structures in the body, such as tissue walls and blood vessel walls. The B-mode processor is (I 2 +Q 2 ) 1 / 2By calculating the echo signal amplitude in the form of, amplitude (envelope) detection of the quadrature demodulated I signal component and Q signal component is performed. The quadrature echo signal components are also coupled to the Doppler processor 24. The Doppler processor 24 stores an ensemble of echo signals from discrete points in the image field, and the ensemble of echo signals is then used to estimate the Doppler shift at points in the image using a fast Fourier transform (FFT) processor. The Doppler processor can also perform angular correction of the Doppler velocity values, and in one implementation of the present invention, the angular correction measured on the first (long axis) Doppler image is used to determine the volume flow. Angular correction of the Doppler data of the second (lateral) Doppler image used for this purpose is performed. The rate at which the ensemble is collected determines the range of velocities of movement that the system can accurately measure and display in the image. The Doppler shift is proportional to the movement at points in the image field, for example, blood flow and tissue movement. In the case of color Doppler image data, the estimated Doppler flow values at each point in the blood vessel are wall filtered, angle corrected, and converted to color values using a look-up table. The wall filter has an adjustable cut-off frequency, and movements such as the low-frequency movement of the blood vessel wall when imaging flowing blood are excluded when the cut-off frequency is exceeded or fallen below. The B-mode image data and the Doppler flow values are coupled to the scan converter 28, and the scan converter 28 converts the B-mode samples and the Doppler samples from their collected R-θ coordinates to Cartesian (x, y) coordinates for display in a desired display format, for example, the linear display format or the sector display format shown in FIGS. 7 and 7a. Either the B-mode image or the Doppler image may be displayed alone, or the color Doppler overlay may show the blood flow in the B-mode processed tissue and blood vessels in the image as shown in FIGS. 7 and 7a, and in anatomical registration, the B-mode image and the Doppler image may be shown together. Another possibility for display is to display images of the same anatomy processed differently in parallel, as shown in these drawings.This parallel display format is useful when comparing images, and is particularly useful for displaying both images of a biplane probe. The scan-converted image data, i.e., both B-mode data and Doppler data, are combined in the image data memory 30, stored in the image data memory 30, where the image data is stored in memory locations addressable according to the spatial location from which the image data values were collected. The biplane image from the data generated by the scan converter 28 and stored in the image data memory is combined with the display processor 34 for further enhancement, buffering, and temporary storage for display on the image display 36.

[0023] Doppler values of an image, such as the color Doppler pixel values of the lateral view of the blood vessel shown in the image 92 of FIG. 7, are combined with the volume flow calculator 40. There, an algorithm for calculating the volume flow is executed, such as the integration of the pixel flow velocity values over the area of the blood vessel lumen, as exemplified by the equation

Equation

[0024] The details of the operation of the volume flow calculator 40 of FIG. 8 are shown in FIG. 8a. In this implementation, the angle correction of the lateral image 92 is performed by the volume flow calculator rather than the Doppler processor 24. The image segmentation processor 402 receives the data of the lateral image 92 from the image data memory 30. The Doppler data in the lateral view of the blood vessel 70 is identified (segmented) by the placement by the system operator of a template, such as the circular template 78 over the lumen of the blood vessel 70. The Doppler data thereby specified within the blood vessel 70 is coupled to the angle correction processor 404, which calculates the angle correction to be performed for the Doppler data of the long axis view 90 from the long axis Doppler gate line 82 and the long axis flow cursor 84, which is the angle between two graphics set by the user during the acquisition of the long axis view 90. The Doppler values of the flow in the lateral image are thereby angle-corrected according to the angles set by these graphics during the acquisition of the long axis view 90. The angle-corrected Doppler values are then integrated over the blood vessel region in the lateral image 92 to determine the volume flow. In the implementation of FIG. 8a, this operation is performed by summing the angle-corrected Doppler flow values of the lateral view image, as shown by the processor 406, to generate a measure Q of the volume flow. This value is coupled to the graphics generator 49 for display to the ultrasound system operator. In a general implementation, the calculations performed by the processors 402, 404, and 406 are performed by a software program configured to perform the functions shown.

[0025] The ultrasonic system of FIG. 8 can be operated to perform a general ultrasonic carotid artery examination as follows. The user first examines the carotid artery by ultrasonic imaging, including B-mode, color Doppler, and pulsed Doppler imaging according to standard clinical practice. When identifying significant stenosis, the user then takes the following steps to determine the volume flow. First, a scan is performed using the ultrasonic probe to find the section of the artery upstream of the stenosis to minimize turbulent flow in the blood stream. Next, the biplane mode is activated. The probe is manipulated until the blood vessel appears stretched in the long-axis view on the left image 90. The probe is tilted at an elevation angle until the blood vessel is approximately centered in the right image 92. The color scale (pulse repetition frequency, PRF) is adjusted so that the flow is not aliased. The angle correction is adjusted to align with the blood vessel 70 in the left image 90. Then, one or more cardiac cycles of the flow information are collected. The region of interest is specified (segmented) by placing a template 78 over the blood vessel 70 in the right image to define which color pixels in the image should be included in the volume flow calculation. Then, the volume flow is calculated and displayed using the Doppler data of the angle-corrected transverse image from the angle correction of the long-axis view, either as a time average (singular) or as a graph of the volume flow as a function of time.

[0026] A method for measuring volume flow according to the principles of the present invention is performed as shown in FIG. 9. At start 901, the ultrasonic system is set to operate in a biplane mode, whereby those images that intersect at a Doppler angle of one of the two images are collected. At 903, a first Doppler image is collected, such as the long axis view 90 of FIG. 7. At 904, the direction of Doppler collection of this first image is adjusted by adjusting the Doppler gate line 82. After setting the Doppler direction, at 905, a second Doppler image is collected in a plane in the Doppler line direction of the first image. At 907, both images are displayed simultaneously. At 909, a Doppler angle correction for the first image is determined from the Doppler line direction and the direction of the flow cursor set by the user over the flow of the first image. At 911, the flow of the second Doppler image is segmented, such as by placing a graphic circle template over the lumen of the second image. At 915, the volume flow is calculated from the Doppler values of the flow of the second image angle-corrected by the angle correction determined for the first image, as described above. At 920, the measured volume flow is displayed to the user or recorded during the ultrasonic examination recording.

[0027] The scope of the present invention described above does not necessarily include an ultrasonic probe, but instead includes embodiments adapted to receive an input of Doppler image data collected from two image planes (90, 92) that intersect along the Doppler beam direction and generate two Doppler images of the flow. It should be noted that the present invention further includes a display (36) for simultaneously displaying two Doppler images, and a graphics generator (49) that, in response to user control, displays a Doppler line (82) and a flow cursor (84) over a first Doppler image (90) of the two Doppler images. The volume flow calculator (40) determines an angle-corrected measure of the volume flow in response to the Doppler image data of a second Doppler image (92) of the two Doppler images and the Doppler angle established by the Doppler line and the flow cursor.

[0028] Furthermore, it should be noted that the component structure of the ultrasonic system, particularly the ultrasonic system of FIG. 8, which is suitable for use in the implementation form of the present invention, is implemented in hardware, software, or a combination thereof. Various embodiments and / or components of the ultrasonic system and its controller, or components and controllers therein, are also implemented as part of one or more computers or microprocessors. The computer or processor includes a computing device, an input device, a display unit, and an interface for accessing, for example, the Internet. The computer or processor includes a microprocessor. The microprocessor is connected to a communication bus, for example, to import training images and access a PACS system or data network to store the results of clinical examinations. The computer or processor also includes a memory. Memory devices such as image data memories include random access memory (RAM) and read-only memory (ROM). The computer or processor further includes a storage device, which is a hard disk drive or a removable storage drive such as a floppy disk drive, an optical disk drive, a solid state drive, etc. The storage device can also be other similar means for loading a computer program or instructions for volume flow analysis into the computer or processor.

[0029] As used herein, the terms "computer", "module", "processor" or "workstation" include any processor-based or microprocessor-based system, including a microcontroller, a reduced instruction set computer (RISC), an ASIC, a logic circuit, and any other circuit or processor capable of performing the functions described herein. The above examples are merely illustrative and thus do not limit, in any way, the definition and / or meaning of these terms.

[0030] A computer or processor executes a set of instructions stored in one or more storage elements to process input data. The storage elements also store data or other information if desired or required. The storage elements can be in the form of information sources or physical memory elements within the processing machine. A set of instructions for an ultrasonic system that controls the collection, processing, and display of ultrasonic images and instructions for the Doppler angle measurement and volume flow calculation described above includes various commands that instruct a computer or processor as a processing machine to perform specific operations such as Doppler flow data collection, line and cursor adjustment, and methods and processes for volume flow measurement. The set of instructions can be in the form of a software program. The software can be in various forms implemented as tangible and non-transitory computer-readable media such as system software or application software. The equations given above for volume flow calculation, and the sum of the Doppler data values shown in FIG. 8a, and the calculation of the Doppler angle from the cursor placed on the image are generally calculated by or under the direction of software routines. Further, the software can be in the form of a collection of separate programs or modules within a larger program, or a part of a program module. The software also includes modular programming in the form of object-oriented programming. The processing of input data by the processing machine is performed in response to operator commands issued from the control panel 38, in response to the results of previous processing, or in response to requests made by another processing machine.

[0031] Further, the limitations in the following claims are not written in means-plus-function format and are not to be construed under 35 U.S.C. § 112, ¶ 6, unless such claim limitations expressly use the phrase "means for" and a statement of function without further structure following it.

Claims

1. An ultrasonic diagnostic imaging system for analyzing the blood volume flow, the ultrasonic diagnostic imaging system comprising: An ultrasonic probe that collects Doppler image data from two image planes that intersect along the Doppler beam direction; An image data processor that generates two Doppler images of the flow in response to the collected Doppler image data; A display that simultaneously displays the two Doppler images; A graphics generator that displays, on a first Doppler image of the two Doppler images, a Doppler line aligned with the Doppler beam direction and a flow cursor that is adjusted in position on the first Doppler image by user control and aligned with the blood flow direction; A volume flow calculator that determines an angle-corrected measurement of the volume flow in response to Doppler image data of a second Doppler image of the two Doppler images and a Doppler angle that is the angle between the Doppler line and the flow cursor; An ultrasonic diagnostic imaging system comprising.

2. The Doppler line is aligned with the Doppler beam direction that scans the first Doppler image, The ultrasonic diagnostic imaging system according to claim 1, wherein the image plane of the second Doppler image is aligned with the Doppler beam direction of the first Doppler image.

3. The ultrasonic diagnostic imaging system according to claim 1, wherein the ultrasonic probe further simultaneously collects a long-axis view of a blood vessel in the first Doppler image and a transverse view of the blood vessel in the second Doppler image.

4. The first Doppler image is collected by scanning an image plane using a plurality of parallel Doppler beams transmitted in a given direction, The ultrasonic diagnostic imaging system according to claim 1, wherein the Doppler line is aligned with the given direction of the plurality of parallel Doppler beams.

5. The ultrasonic diagnostic imaging system according to claim 4, wherein the image plane of the second Doppler image is aligned with the given direction of the plurality of parallel Doppler beams of the first Doppler image.

6. The ultrasonic diagnostic imaging system according to claim 1, wherein the ultrasonic probe further comprises a two-dimensional matrix array transducer.

7. The ultrasonic diagnostic imaging system according to claim 6, wherein the ultrasonic probe further operates in a biplane mode to scan two image planes in a time-interleaved manner.

8. The ultrasonic diagnostic imaging system according to claim 7, wherein the ultrasonic probe further scans two image planes at a selected non-orthogonal angle with respect to the plane of the two-dimensional matrix array transducer.

9. The ultrasonic diagnostic imaging system according to claim 7, wherein the ultrasonic probe further scans an image plane at a selected non-orthogonal angle with respect to the direction of flow.

10. The volume flow calculator further 【Equation 3】 calculates an algorithm of the form: where Q is the volume flow, v is the flow velocity corrected for angle, and surface S is a cross-section passing through a blood vessel containing Doppler data. The ultrasonic diagnostic imaging system according to claim 1.

11. The ultrasonic diagnostic imaging system according to claim 10, wherein the volume flow calculator further sums the values of the angle-corrected Doppler data within the blood vessel lumen.

12. A method of using an ultrasonic diagnostic imaging system for performing an ultrasonic examination to measure volume flow, the method comprising: Scanning using an ultrasonic probe operating in a biplane mode to collect a first Doppler image of a target blood vessel in a long-axis view, Scanning using the ultrasonic probe in the biplane mode to simultaneously collect a second Doppler image in a transverse view of the target blood vessel in an image plane aligned with a Doppler angle, which is the angle between the Doppler beam direction scanning the first Doppler image and the flow direction of blood flow on the first Doppler image, Simultaneously displaying the two images, Determining an angle correction according to the Doppler beam direction scanning the first Doppler image and the flow direction on the first Doppler image, Calculating the volume flow from the data of the second Doppler image using the angle correction determined from the first Doppler image A method comprising.

13. The method according to claim 12, further comprising adjusting the Doppler beam direction to scan the first Doppler image so as to intersect the flow direction at a non-orthogonal angle.

14. The method according to claim 13, further comprising segmenting the volume flow in the second Doppler image using a template.

15. The method according to claim 12, wherein the step of calculating the volume flow further comprises integrating flow value pixels of the target blood vessel in the second Doppler image.

16. An ultrasonic diagnostic imaging system for analyzing blood volume flow, the ultrasonic diagnostic imaging system comprising: An image data processor that generates two Doppler images of flow in response to input of Doppler image data collected from two intersecting image planes along a Doppler beam direction, A display for simultaneously displaying the two Doppler images, A graphics generator that displays, on top of the first Doppler image of the two Doppler images, a Doppler line aligned with the Doppler beam direction and a flow cursor that is adjusted in position on the first Doppler image by user control to be aligned with the blood flow direction, A volume flow calculator that determines a measurement value of the volume flow corrected for the angle in response to the Doppler image data of the second Doppler image of the two Doppler images and the Doppler angle that is the angle between the Doppler line and the flow cursor An ultrasonic diagnostic imaging system comprising the same.

17. The Doppler line is aligned with the Doppler beam direction for scanning the first Doppler image, The ultrasonic diagnostic imaging system according to claim 16, wherein the image plane of the second Doppler image is aligned with the Doppler beam direction of the first Doppler image.

18. The volume flow calculator further, 【Equation 4】 Calculates an algorithm of the form where Q is the volume flow, v is the flow velocity corrected for the angle, and surface S is a cross-section passing through a blood vessel containing Doppler data. The ultrasonic diagnostic imaging system according to claim 16.

19. The ultrasonic diagnostic imaging system according to claim 18, wherein the volume flow calculator further sums the values of the Doppler data corrected for the angle within the blood vessel lumen.

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