Ultrasound method and ultrasound system for real time automatic setting of parameters for doppler imaging modes

To lessen the examination time in an Ultrasound system in a vascular Exam routine, it is desirable to: automatically position in the best way Color Doppler ROI and/or Sample Gate; select the best Color Doppler/Beamline Steering angle; and set the Doppler Correction angle. An algorithm is provided that is able to process in real time the Doppler Signal to identify the Doppler Area where the most significant flow is present, and then it analyzes the ‘Shape’ of such Color Doppler Area identifying the Position and direction of the “main” Flow. The vascular Examination routine can therefore be made easier and faster.

BACKGROUND OF THE INVENTION

The present disclosure relates to an ultrasound method and to an ultrasound system both for real time automatic setting of parameters for color Doppler imaging mode.

Ultrasound imaging systems are operable alternatively or in combination in several imaging modes which furnishes different views and thus different features of the imaged object. Among the different modes, the most common modes are:

B mode for tissue imaging,

Doppler modes for flow analysis and imaging.

Typical Doppler modes include Power Doppler mode used for both tissue motion and flow imaging, Color Flow Doppler mode for qualitative flow imaging, and Spectral Doppler mode for flow quantification.

Doppler image data can be related to mono-dimensional images, bi-dimensional images (2D) and three-dimensional images (3D). Also the method and the system described herein can be used for acquiring mono-dimensional, bi-dimensional and three-dimensional images.

During vascular examinations by means of an ultrasound imaging system, ColorFlow Doppler imaging mode is frequently used for examining the anatomical conditions of the blood vessels and provide a diagnosis about the presence of a vascular diseases.

The vascular examination routine includes to carry out operations for positioning in the best way the Color Doppler region of interest (ROI) and/or the Doppler Sample Gate and/or to select the best Color Doppler-Beamline Steering angle and/or to set the Doppler Correction angle. Carrying out these operations manually is time consuming and increases the examination time and the costs. Currently different techniques are available for carrying out the above operations in real time and in an automatic way.

The state of the art comprises different methods for automatic settings of the best positioning of the Color Doppler ROI and/or the Doppler Sample Gate and/or of the best Color Doppler-Beamline Steering angle and/or of the Doppler Correction angle but these known methods does not operate in a fully automatic way and in true real time, particularly when following the change of the scanned target (e.g. moving the probe).

US 2014/0221838 describes an ultrasound system which automates the color box placement, Doppler sample volume placement, angle correction, and beam steering angle using vessel segmentation and flow image analysis.

U.S. Pat. No. 6,322,509 describes a method for automatically adjusting the Doppler sample gate position and size settings based on the vessel image data. Using an object search technique based solely on geometric and morphological information in a binarized vessel image obtained from either B-mode or color flow image data a vessel segment is searched. The morphologically best or nearest vessel segment within a target search region in a two-dimensional image is found. The sample gate is placed at or near the center of the targeted vessel segment and the size of the sample gate is adjusted in relation to the vessel size. The best available steering angle minimizing the Doppler angle is selected.

In U.S. Pat. No. 8,047,991 a direction and/or an orientation are automatically identified in ultrasound image by using region shrinking process or by using locations associated with flow or tissue structure.

In U.S. Pat. No. 5,690,116 an histogram based method is discloses. According to this document, an automatic measurement is made of the angle enclosed by the direction of ultrasonic echographic beam and the axis of a vessel, defined as Doppler angle, in an echographic image on the basis of prior designation of an initial point Pi in the vessel. A first isotropic tracing of rays starting from the initial point Pi is used to produce a histogram of the grey levels of the points of the rays. An algorithm is then applied to the histogram in order to classify the grey levels of selected points. A second tracing of rays is made which is restricted to the walls of the vessel and provides information for determining the slope of a regression line is and the calculation of the Doppler angle.

There is a need for a method and system for real time automatic setting of parameters for color Doppler imaging mode and particularly automatic positioning in the best way the Color Doppler ROI and/or the Sample Gate and/or automatically selecting the best Color Doppler/Beamline Steering angle and/or automatically setting the Doppler Correction angle, not only in response of a user action but also in adapting to a change of the scanned target (e.g. moving the probe) which method and which system provides for a faster and easier vascular examination routine.

SUMMARY

It is an object to provide a method for automatic measurement of the Doppler angle of a blood vessel in an echographic image, starting from a designated point.

It is another object to provide a method for automatic measurement of the Doppler angle which is exact and fast.

A further object consists in providing an ultrasound system configured for carrying out the above measuring method.

According to a first aspect a method for real time automatic setting of parameters for color Doppler imaging mode is provided comprising the following steps:transmitting ultrasound beams in a target body and receiving the reflected beam from the said target body;extracting Color Doppler signals from the said reflected beams;processing the Color Doppler signals to identify an area where the Color Doppler signals indicate that a flow is present and processing the Color Doppler signals relating to the said area for automatically determining one or more of the following parameter settings:

best positioning of the Color Doppler ROI and/or of the Doppler sample Gate, determining and applying the best Color Doppler beam steering angle, setting the Doppler correction angle,processing the said Color Doppler Signals comprises:analysing the shape of the identified Color Doppler area by processing the corresponding Color Doppler signals for determining:

a) the position of a flow having the most significant intensity;

b) the direction of the flow at the position as determined in a);determining the best position of the Color Doppler ROI and/or of the Doppler sample gate as a function of the said position of the flow and positioning the said Color Doppler ROI and/or sample gate on that position;determining the steering angle of the transmit beams and/or the Doppler correction angle as a function of the direction of the flow.

According to an embodiment, the operation of analysing the shape of the identified Color Doppler area is based on morphological features of the flow determined from the Color Doppler flow signals.

In a further embodiment, analysing the shape of the identified Color Doppler area comprises creating a virtual Doppler image of the flow from the Color Flow signals.

According to an embodiment, determining the position of a flow having the most significant intensity comprises:optionally sampling and/or filtering the virtual Doppler image;calculating the maximum value of the pixels or voxels of the virtual Doppler image and selecting the position of the said pixel or voxel as the position of the flow.

In combination of one or more of the previously described embodiments in a further improvement determining the direction of the flow comprises:applying four directional filters on the virtual Doppler image at the position of the pixels having the maximum value, the said directional filters being oriented respectively along one of four directions each being rotated of 45° with respect to an adjacent directioncombining the output of the said four directional filters to obtain a vector;determining the flow direction as a function of the direction of said vector.

According to embodiments herein, determining the direction of the flow comprises:applying four directional filters on the virtual image at the position of the pixels having the maximum value, the said directional filters being oriented respectively along the following directions defined by the axis passing through the directions of a goniometer centred on the centre position of the flow according to the following notation 0°-180°, 45°-215°, 90°-270° and 135°-315° the goniometer being aligned with the axis of a Cartesian system defining the two dimensions of the image with the 0°-180° axis and the 90°-270° axis;combining the output of the said four directional filters forming a vector with orthogonal components x and y having the following values X=(output of the filter having direction 0°-180°)−(output of the filter having direction 90°-270°) and Y=(output of the filter having direction 45°-215°)−(output of the filter having direction 135°-315°);determining the phase of the vector and calculating the flow direction angle as a function of the said phase.

According to an embodiment, the virtual Doppler images from which the directions are calculated are subsampled, particularly by a factor 2.

According to a further variant embodiment the virtual Doppler images are filtered by a smoothing filter.

According to an embodiment, the function for determining the flow direction is calculated as:

According to a further improvement, the normalized module Q of the vector can be calculated and used as factor of merit, or quality factor, of the estimation of the direction.

An embodiment provides the following function for calculating the normalized module Q of the vector:

Q=(F⁢⁢0-F⁢⁢90)2+(F⁢⁢45-F⁢⁢135)2(F⁢⁢0+F⁢⁢90)2+(F⁢⁢45+F⁢⁢135)2
In which:
F0 is the output of the filter having direction θ°-180°;
F45 is the output of the filter having direction 45°-215°;
F90 is the output of the filter having direction 90°-270° and
F135 is the output of the filter having direction 135°-315°

According to an embodiment the method provides for the additional steps of:Defining a threshold for the value of the said normalized module of the vector determined according to one or more of the embodiments described above;calculating the said normalized module Q;comparing the said calculated value for the normalized module with the threshold;setting the best Color Doppler Beam-axis steering angle and the Doppler correction angle according to the flow directions calculated as the function of the phase of the same vector of which the normalized module is calculated if this calculated value of the said normalized module is above the threshold.

According to a further aspect an ultrasound imaging system is provided comprising:an ultrasonic probe including a transducer array which probe transmits ultrasound beams in a target region where a flow is present and which receives the echo signals reflected by the said target region;a beamformer which controls the directions in which the ultrasound beams are transmitted by the probe;a Doppler processor producing Doppler signals from the echo signals;an image processor producing Doppler images of the flows in target region;a Color Doppler ROI and/or Doppler sample gate positioning processor for automatically positioning the ROI and/or a sample gate in the best position relatively to the imaged flow;a Steering angle and/or Doppler correction angle processor for automatically determining the best steering angle and setting the corresponding best correction angle of the ultrasound beams propagation directions;the said Color Doppler ROI and/or Doppler sample gate positioning processor and the steering angle and/or Doppler correction angle processor are configured to processing the color Doppler flow signals and determining data relating to morphological features of the flow and calculating the best position for the Color Doppler ROI and/or the Doppler sample gate and the Steering angle and/or the Doppler correction angle as a function of the said data on morphological features.

According to an embodiment, the positioning processor is provided in combination with a color Doppler image processing unit generating an image from the color Doppler signals and is configured to determine the maximum pixel value and the position of the corresponding pixel, the said color Doppler image processing unit comprises a ROI and or sample gate manager unit automatically positioning or centering the ROI and/or the sample gate at the position of said pixel having the maximum value.

According to still a further embodiment, the Steering angle and/or Doppler correction angle processor is provided in combination with a color Doppler image processing unit generating an image from the color Doppler signals and comprises a filter unit provided with four direction filters each oriented along one of four directions each being rotated of 45° with respect to an adjacent direction,

The outputs of the four directional filters being connected to the Steering angle and/or Doppler correction angle processor being configured to calculate the flow direction and a factor of merit of the calculated direction.

According to an embodiment, the positioning processor comprises a sampling unit for subsampling the Color Doppler image and optionally a smoothing filter of the subsampled image.

According to an embodiment, the Steering angle and/or Doppler correction angle processor comprises a sampling unit for subsampling the Color Doppler image.

In a further embodiment the Steering angle and/or Doppler correction angle processor comprises a memory for saving a threshold value for the factor of merit and a comparator for comparing the calculated factor of merit with the threshold, the comparator output being read by the Steering angle and/or Doppler correction angle processor for determining whether the flow direction calculated can be used for determining the steering angle of the transmit beam and/or the Doppler correction angle.

According to an embodiment a program is loaded and executed by the Steering angle and/or Doppler correction angle processor the said program configuring the said processor for calculating the flow direction and the factor of merit as a function of the outputs of the four directional filters according to the following functions:

DIRECTION=12⁢a⁢tan⁡(YX)⁢180π
Where X and Y are the components of a vector determined by combining the output values of the four direction filters according to the following:
X=F0-F90 and Y=F45-F135
In which
F0 is the output of the filter having direction θ°-180°;
F45 is the output of the filter having direction 45°-215°;
F90 is the output of the filter having direction 90°-270° and
F135 is the output of the filter having direction 135°-315°
And the quality factor corresponding to the normalized modulus of the said vector having the components X and Y defined above, where:

Q=(F⁢⁢0-F⁢⁢90)2+(F⁢⁢45-F⁢⁢135)2(F⁢⁢0+F⁢⁢90)2+(F⁢⁢45+F⁢⁢135)2
And in which F0, F45, F90, F135 are according to the above definition.

As it appears from the above describe embodiments, determining the best position of the Color Doppler flow and/or of the sample gate and the best steering angle of the transmit beam and the corresponding Doppler correction angle is a very simple operation which can be carried out quickly. Thus in using the method and the system according to the above embodiments, the determination of the best ROI position and/or best sample gate position and of the best steering angle and Doppler correction angle can be carried out very quickly and in real time without introducing any delay which slows down the vascular examination routine and rendering easier and faster this routine.

Furthermore, the simplicity of the calculations to be carried out and in general of the entire automatic process allows to automatically follow any change in relation to the scanned target such as for example when moving the probe.

From the point of view of the implementation of the method in an ultrasound system, since the process consists essentially in a specific processing of signals which are in any case received and produced by the existing and traditional units of an ultrasound scanner, the Steering angle and/or Doppler correction angle processor and the positioning processor can be generic processors already provided in an ultrasound system and in which a program is loaded and executed, in the said program the steps of the method according to one or more of the described embodiments being coded in the form of instructions which configures the generic processor and the peripheral connected to it for carrying out the functions of operative units needed for executing the steps of the method.

According to a further aspect a readable medium is provided in which the instructions are coded for configuring a generic processor and optionally the peripherals connected to it in such a way that the processor and one or more of the said peripherals carry out the functions of operating units needed for executing the method, the said medium being readable by a reader unit or being stably installed as a peripheral of the processor. Non-exhaustive examples of such mediums are CD-ROM, CD-RAM, DVD-ROM, DVD-RAM, memory cards, USB memory sticks, portable hard disks, internal hard disks and other similar devices.

DETAILED DESCRIPTION

While multiple embodiments are described, still other embodiments of the described subject matter will become apparent to those skilled in the art from the following detailed description and drawings, which show and describe illustrative embodiments of disclosed inventive subject matter. As will be realized, the inventive subject matter is capable of modifications in various aspects, all without departing from the spirit and scope of the described subject matter. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive.

FIG. 1illustrates a high-level block diagram of an ultrasound system implemented in accordance with embodiments herein. Portions of the system (as defined by various functional blocks) may be implemented with dedicated hardware, analog and/or digital circuitry, and/or one or more processors operating program instructions stored in memory. Additionally, or alternatively, all or portions of the system may be implemented utilizing digital components, digital signal processors (DSPs) and/or field programmable gate arrays (FPGAs) and the like. The blocks/modules illustrated inFIG. 1can be implemented with dedicated hardware (DPSs, FPGAs, memories) and/or in software with one or more processors.

The ultrasound system ofFIG. 1includes one or more ultrasound probes101. The probe101may include various transducer array configurations, such as a one-dimensional array, a two-dimensional array, a linear array, a convex array and the like. The transducers of the array may be managed to operate as a 1D array, 1.25D array, 1.5D array, 1.75D array, 2D array, 3D array, 4D array, etc.

The ultrasound probe101is coupled over a wired or wireless link to a beamformer103. The beamformer103includes a transmit (TX) beamformer and a receive (RX) beamformer that are jointly represented by TX/RX beamformer103. The TX and RX portions of the beamformer may be implemented together or separately. The beamformer103supplies transmit signals to the probe101and performs beamforming of “echo” receive signals that are received by the probe101.

A TX waveform generator102is coupled to the beamformer103and generates the transmit signals that are supplied from the beamformer103to the probe101. The transmit signals may represent various types of ultrasound TX signals such as used in connection with B-mode imaging, Doppler imaging, color Doppler imaging, pulse-inversion transmit techniques, contrast-based imaging, M-mode imaging and the like. Additionally, or alternatively, the transmit signals may include single or multi-line transmit, shear wave transmit signals and the like.

The beamformer103performs beamforming of the transmit beams in order to focalize the transmit beams progressively along different adjacent lines of sight covering the entire ROI. The beamformer performs also beamforming upon received echo signals to form beamformed echo signals in connection to pixel locations distributed across the region of interest. For example, in accordance with certain embodiments, the transducer elements generate raw analog receive signals that are supplied to the beamformer. The beamformer adjusts the delays to focus the receive signal along one or more select receive beams and at one or more select depths within the region of interest (ROI). The beamformer adjusts the weighting of the receive signals to obtain a desired apodization and profile. The beamformer applies weights and delays to the receive signals from individual corresponding transducers of the probe. The delayed, weighted receive signals are then summed to form a coherent receive signals.

The beamformer103includes (or is coupled to) an A/D converter124that digitizes the receive signals at a selected sampling rate. The digitization process may be performed before or after the summing operation that produces the coherent receive signals.

Optionally, a dedicated sequencer/timing controller110may be programmed to manage acquisition timing which can be generalized as a sequence of firings aimed at selected reflection points/targets in the ROI. The sequence controller110manages operation of the TX/RX beamformer103in connection with transmitting ultrasound beams and measuring image pixels at individual line of sight (LOS) locations along the lines of sight. The sequence controller110also manages collection of receive signals.

One or more processors106perform various processing operations as described herein.

In accordance with embodiments herein the beamformer103includes an output that is configured to be coupled to an ultrasound probe101and sends signals to the transducer elements of the probe101.

According to an embodiment herein the sequencer110controls the beamformer in order to generate and transmit a plurality of transmit beams which are focalized in such a way as to show an aperture or a beam width encompassing a certain number of line of sights or of receive lines. The transmit beams of the said plurality being progressively laterally shifted along the array of transducer elements of the probe and thus along the ROI for scanning the entire ROI. A certain line of sight or a certain receive line will be encompassed by a certain number of different transmit beams of the said plurality as long as the said line of sight position or the said receive line position falls within the aperture of the said transmit beams or within the width of the said transmit beams. Thus, for a reflecting point on a certain receive line or line of sight having a certain line position within the ROI and relatively to the transducer array of the probe a certain number of receive signals contributions are received each one deriving from a different transmit beam whose center transmit line having different lateral shifts relatively to the said reflecting point and to the corresponding receive line.

The receive data relative to the echoes from the said reflecting point is a combination of the contributions of the receive signals from the said reflecting point deriving from the said certain number of transmit beams.

In accordance with embodiments herein, the beamformer103includes an input that is configured to be coupled to an ultrasound probe101and receive signals from transducers of the ultrasound probe101. The memory105stores time delays to align contributions of reflection signals received by the transducers of the array of the probe101from the reflectors in the ROI. The memory105also stores phase corrections to correct phase differences of the receive signals contributions for each transducer element and deriving from each of the said certain number of differently laterally shifted transmit beams relatively to the receive line or line of sight on which the said reflector point is located.

A delay/phase correction (DPC) module104is coupled to the memory105and provides various delays and corrections to the beamformer103. For example, the DPC module104directs the beamformer103to apply time delay and phase correction to the receive signals to form delayed receive signals. The beamformer103then sums, in a coherent manner, the delayed receive signals to obtain a coherent receive signal in connection with a reflection point or a reflection target.

Optionally, the memory105may store a common phase shift correction in connection with multiple channels. Different phase shift corrections may be stored in connection with various corresponding channels in the case of multiple receive signals that are received along a common receive line position but, due to a certain number of different transmit beams, each one having a laterally shifted transmit center line and an aperture or width encompassing the receive line position. The memory105may also store weights such as apodization weights and/or Retrospective Transmit Beamforming (RTB) weights.

As explained herein, the beamformer103(circuitry) is configured to apply contemporaneously to each receive signal contribution of each transducer element from a reflection point a beamforming focalization delay and a phase shift equalization delay so called RTB delay. The said beamforming focalization delay being calculated basing on the time of arrival of the said signal contribution to a transducer element when traveling from the reflection point to the said transducer element and the said phase shift equalization delay being determined according to the difference in phase of the wave front reaching the reflecting point relatively to the phase of the wave fronts reaching the same reflecting point and being of further transmitted beams which are laterally shifted each other.

Optionally, the memory105may store a pre-calculated table, where the pre-calculated table comprises real times of arrival of the receive signals relative to a predetermined reflection point. Optionally, the processor106may be configured to calculate real times of arrival of the receive signals relative to a predetermined reflection point. Optionally the memory105may store a pre-calculated table, where the pre-calculated table comprises pre-calculated phase shift equalization delays to be applied contemporaneously to the beamforming focalization delays to the receive signals of a receive line along a certain line of sight or a certain receive line position deriving from a certain number of transmit beams being differently laterally shifted relatively to the said receive line position, the number of the said transmit beams being set by setting a certain aperture or lateral width of the said transmit beams. Optionally the memory105may store a pre-calculated table of the said phase shift equalization delays which are pre-calculated for one or more of different transmit beams apertures or widths.

Optionally, the processor106may be configured to calculate the said phase shift equalization delays for one or more of different transmit beams apertures or widths.

Optionally, the beamformer103circuitry may further comprise an adder unit for adding the beamforming delays and the phase shift equalization delays (RTB delays) for the receive signal contributions deriving from each reflecting point.

In accordance with certain embodiments, at least a portion of the beamforming process may be implemented by the processor106(e.g., in connection with software RTB beamforming). For example, the memory105may store beamforming related program instructions that are implemented by the processor106to contemporaneously apply beamforming delays and phase shift equalization delays to the receive signals.

The processor106and/or CPU112also performs conventional ultrasound operations. For example, the processor106executes a B/W module to generate B-mode images. The processor106and/or CPU112executes a Doppler module to generate Doppler images. The processor executes a Color flow module (CFM) to generate color flow images. The processor106and/or CPU112may implement additional ultrasound imaging and measurement operations. Optionally, the processor106and/or CPU112may filter the first and second displacements to eliminate movement-related artifacts.

An image scan converter107performs scan conversion on the image pixels to convert the format of the image pixels from the coordinate system of the ultrasound acquisition signal path (e.g., the beamformer, etc.) and the coordinate system of the display. For example, the scan converter107may convert the image pixels from polar coordinates to Cartesian coordinates for image frames.

A cine memory108stores a collection of image frames over time. The image frames may be stored formatted in polar coordinates, Cartesian coordinates or another coordinate system.

An image display109displays various ultrasound information, such as the image frames and information measured in accordance with embodiments herein. The display109displays the ultrasound image with the region of interest shown.

A control CPU module112is configured to perform various tasks such as implementing the user input data interface114and overall system configuration/control. In case of fully software implementation of the ultrasound signal path, the processing node usually hosts also the functions of the control CPU.

A power supply circuit111is provided to supply power to the various circuitry, modules, processors, memory components, and the like. The power supply111may be an A.C. power source and/or a battery power source (e.g., in connection with portable operation).

According to an embodiment the ultrasound system ofFIG. 1is provided with a Positioning, steering angle and correction angle processor indicated with161. This processor is configured to determine in an automatic way the best position relative to a vessel or a flux in the target region of the region of interest (ROI) of the color Doppler flow or the best position of the Doppler sample gate. Furthermore the processor161calculates the best steering angle of the transmit beams for acquiring Doppler signals and data and the best Doppler correction angle.

FIG. 3shows a schematic representation of a target region in which a vessel300is present containing a flow. With310the beam direction is indicated which is at an angle of the unsteered beam propagation direction of a transmit beam generated by a probe and which in general is essentially perpendicular to the surface of the transducer array in the case of a plane array or perpendicular to a tangent surface to the curved surface of a curved array. The steering angle β is indicated in the representation ofFIG. 3as well as the correction angle α, which is the angle between the direction of the flow indicated by320and the steered transmit beam direction or propagation axis310.

Since Doppler data is based on phase shifts between the transmit beam and the reflected beam due to motion, the motion has to have at least a component parallel to the transmit beam otherwise there will be no Doppler contribution in the reflected beam. As it appears clearly the correct positioning of the ROI or sample gate G and the determination of the best steering angle and correction angle will be essential to the quality of the Doppler data and thus to obtain best possible color Doppler information of the flow.

In the embodiment ofFIG. 1the processor161receives color Doppler signals from the Color Doppler processor CFM and determines a morphological feature of the flows and the corresponding vessels in the target region. Based on this feature the processor calculates automatically the best positioning of the ROI and/or of the sample gate and the best steering angle of the ultrasound beam and the correction angle. The best positioning of the ROI is determined by finding the pixels in an image corresponding to the color Doppler signals a maximum value of image pixels. The position of this pixel or of these pixels is set as the position of the ROI or sample gate. This information is sent to the CFM processor or to the CPU112for operating the ROI positioning in the displayed image according to the structure of the system as described above.

For determining the best steering angle of the ultrasound beam and/or the best correction angle the processor applies, at the position of the pixel or pixels having a maximum value as determined in the previous step and in the image reproducing the color Doppler signals or data, four directional filters set according to four different directions. The output of the filters is then combined for generating components of a vector whose direction is the direction of the flow. The processor161also determines as a function of the output signals of the four direction filters a quality factor which corresponds to a normalized modulus of the vector and which is a measure for evaluating the quality of the flow direction determined by the vector.

This situation is shown inFIG. 4and will be described later with greater detail.

The steering angle and the correction angle are determined by the processor as a function of the determined direction of flow if the quality factor is above a certain threshold which can be set by the user and or by the producer and installer of the system and which can be based on empirical data acquired in a setting and tuning process.

FIG. 2shows a block diagram of an embodiment of the Positioning, Steering Angle and Correction Angle Processor161. According to the principles of this embodiment, the calculation of the best position of the color Doppler ROI and or of the sample gate G are carried out on image data. This image data may consist in a virtual Doppler image constructed by a dedicated processor or can be obtained from the power output of the CFM processor for example according the system architecture ofFIG. 1. This virtual image generator200ofFIG. 2is to be interpreted as comprising both variants. The positioning processor comprises a subsampling unit201which is configured to subsample the virtual image, as for example by a factor 2. The subsampled image is further processed by a smoothing filter202and the filtered image is processed by a maximum value identifier203and by a pixel position detector204which registers the position of the pixels having the maximum value. This positional data is saved and is used by a ROI and sample gate locator205producing data of the ROI and sample gate position to be provided to the image generating chain such as for example to a CFM processor interface206which provides communication to a CFM processor as for example the one shown inFIG. 1. The information of the position in the virtual image of the pixel having a maximum value are furnished to the Steering angle and correction angle processor shown inFIG. 2. This processor operates also on the virtual image provided by the virtual image generator200and after having submitted the image to a subsampling at a factor 2 or higher or different than 2 by the subsampling unit211, applies to the subsampled image data four different directional filters212, each one set on a different direction. The directions are set according to a sequence of different directions in which each direction is changed by an angular displacement of 45° relatively to the preceding one. The directional filters212are centered at the position in the image corresponding to the position of the pixel having the maximum value as determined by the positioning processor. The output of the directional filters indicated in common by the filters212is processed by a processing unit213which is configured in order to execute an algorithm for determining the directional data of the flow and a quality factor of the said directional data based on which the steering angle and the correction angle are set.

A steering angle calculator214calculates the best steering angle and the best correction angle out of the flow direction and is controlled by the output of a merit factor comparator215which compares the said quality factor with a threshold and triggers the calculation of the steering angle and of the correction angle as a function of the flow direction only if the merit factor is above the threshold. If this is not the case the process is repeated. This new cycle can be started from the very beginning i.e. by calculating again the position of the maximum pixel value in the image or by restarting the process of subsampling, directional filtering and calculating the flow direction within the steering angle and correction angle processor.

When repeating the cycle by starting from any of the two starting steps indicated above the new cycle can be carried out by changing at least one of the parameters of the process, for example by changing the subsampling factor or the settings of the smoothing filter.

According to a variant embodiment, if after a certain pre-set numbers of repetitions of the cycle the merit factor remains still below the defined threshold value, the process is stopped and the flow direction related to one of the computed merit factors is used as the flow direction based on which the steering angle and the correction angle are determined.

Different variants are possible for choosing the flow direction in the above condition. According to a first variant the flow direction is chosen which corresponds to the merit factor coming closer to the threshold value. In a further variant the flow direction is calculated as a mean value of the different flow directions resulting from each repetition cycle. In this case a weighted mean can calculated using the merit factor for each of the flow directions for determining a corresponding weight. In an embodiment, the weight associated to each flow direction is calculated as a function of the difference of the merit factor corresponding to the flow direction and the threshold value. This function can be linear or non-linear in order to penalize more the flow directions for which the difference between the corresponding merit factor and the threshold value is higher in respect to the flow directions for which the difference between the corresponding merit factor and the threshold value is lower.

The steering angle and the correction angle data are provided to the beamformer103for being applied to the transmitted beam.

As already indicated above in relation to the embodiment ofFIG. 1, the positioning processor and the steering angle and correction angle processor can be at least in part (as defined by various functional blocks) implemented with dedicated hardware, analog and/or digital circuitry, and/or one or more processors operating program instructions stored in memory. Additionally, or alternatively, all or portions of the processors may be implemented utilizing digital components, digital signal processors (DSPs) and/or field programmable gate arrays (FPGAs) and the like. The blocks/modules illustrated inFIG. 2can be implemented with dedicated hardware (DPSs, FPGAs, memories) and/or in software with one or more processors.

Directional filters can be designed for any direction within a given space. For images, x- and y-directional filters are commonly used to compute derivatives in their respective directions. The following array is an example of a 3 by 3 kernel for an x-directional filter (the kernel for the y-direction is the transpose of this kernel):

The above array is an example of one possible kernel for a x-directional filter. Other filters may include more weighting in the centre of the nonzero columns. Directional filters as well as an example code is described at northstar-www.dartmouth.edu/doc/idl/html_6.2/Filtering_an_Imagehvr.html

FIG. 5shows examples of the placing of the directional filters at the maximum value position on the subsampled color Doppler image500and the directions at which the four filters are set. A goniometer505shows the direction definition notation utilized in the description and in the claims. The directions briefly indicated by 0°, 45°, 90°, 135° in the image representation500, are defined by goniometer with axis connecting two angular positions so the notation 0° corresponds to the direction of the axis 0°-180°, 45° corresponds to the axis and direction 45°-225°, 90° to the axis 90°-270° and 135° to the axis 135°-315°. The goniometer being aligned with the direction of a reference coordinate system with orthogonal axis.

TheFIGS. 501 to 504inFIG. 5show the graphical representation of the effect of each of the four directional filters.

FIG. 6shows a flow diagram of the method for determining automatically the best positioning of the color Doppler ROI and/or of the sample gate G and for selecting the best color Doppler beam direction steering angle and setting the Doppler correction angle.

At step600a color Doppler flow image is generated from the color Doppler flow signals. These image data is subsampled at step610.

According to a preferred embodiment subsampling is carried out by a factor 2. At step630, the subsampled image620is subjected to a filtering by a smoothing filter. The filtered image640is then submitted to a searching algorithm at step650for finding the maximum pixel or pixels value and identifying its position as indicated by the image660by the arrow.

This position is the position to be used for positioning the ROI and/or the sample gate. Furthermore, this position is the position at which the directional filters has to be positioned, as will be described.

Starting from the sampled image620, at step670the four directional filters are applied to the image being positioned at the pixel position corresponding to the max value. At step680the outputs of the directional filters are combined for calculating the direction and a merit factor of the calculated direction in order to determine if the calculated direction is reliable or not and if it can be used as a reference direction for setting the steering angle of the beam direction and the Doppler correction angle. At step690the direction of the flow resulting from the combination of the filter outputs at step680is shown and indicated by the arrow.

Defining the output of the four directional filters with F0 for the direction 0°-180°, F45 for the direction 45°-225°, F90 for the direction 90°-270° and F135 for the direction 135°-315°, the direction of flow is computed from the phase of a vector having components x and y as indicated inFIG. 4and in which the component x is computed as the difference of the outputs of the filters aligned along the directions 0°-180° and 90°-270°:
X=F0−F90;
Similarly, the component y is computed as the difference of the outputs of the filters aligned along the directions 45°-215° and 135°-315°:
Y=F45−F135.

The phase is computer according to the following function:

The merit factor is computed according to the following function which corresponds to the definition of a normalized modulus of the vector with the component X,Y:

This value is used in combination with a threshold for determining the reliability of the estimation. If comparing the computed merit factor Q this value is above the threshold, the estimated flow direction is considered reliable and is used for determining the steering angle and the correction angle. If the merit factor is below the threshold, the direction estimation is not reliable and the process is repeated for computing a new flow direction.

The repetitions can be carried out according to one or more of the different variants and embodiments described above in relation toFIG. 2.

FIG. 7illustrates a block diagram of an ultrasound system formed in accordance with an alternative embodiment. The system ofFIG. 7implements the operations described herein in connection with various embodiments. By way of example, one or more circuits/processors within the system implement the operations of any processes illustrated in connection with the figures and/or described herein. The system includes a probe interconnect board702that includes one or more probe connection ports704. The connection ports704may support various numbers of signal channels (e.g.,128,192,256, etc.). The connector ports704may be configured to be used with different types of probe arrays (e.g., phased array, linear array, curved array, 1D, 1.25D, 1.5D, 1.75D, 2D array, etc.). The probes may be configured for different types of applications, such as abdominal, cardiac, maternity, gynecological, urological and cerebrovascular examination, breast examination and the like.

One or more of the connection ports704may support acquisition of 2D image data and/or one or more of the connection ports704may support 3D image data. By way of example only, the 3D image data may be acquired through physical movement (e.g., mechanically sweeping or physician movement) of the probe and/or by a probe that electrically or mechanically steers the transducer array.

The probe interconnect board (PIB)702includes a switching circuit706to select between the connection ports704. The switching circuit706may be manually managed based on user inputs. For example, a user may designate a connection port704by selecting a button, switch or other input on the system. Optionally, the user may select a connection port704by entering a selection through a user interface on the system.

Optionally, the switching circuit706may automatically switch to one of the connection ports704in response to detecting a presence of a mating connection of a probe. For example, the switching circuit706may receive a “connect” signal indicating that a probe has been connected to a selected one of the connection ports704. The connect signal may be generated by the probe when power is initially supplied to the probe when coupled to the connection port704. Additionally, or alternatively, each connection port704may include a sensor705that detects when a mating connection on a cable of a probe has been interconnected with the corresponding connection port704. The sensor705provides signal to the switching circuit706, and in response thereto, the switching circuit706couples the corresponding connection port704to PIB outputs708. Optionally, the sensor705may be constructed as a circuit with contacts provided at the connection ports704. The circuit remains open when no mating connected is joined to the corresponding connection port704. The circuit is closed when the mating connector of a probe is joined to the connection port704.

A control line724conveys control signals between the probe interconnection board702and a digital processing board726. A power supply line736provides power from a power supply740to the various components of the system, including but not limited to, the probe interconnection board (PIB)702, digital front end boards (DFB)710, digital processing board (DPB)726, the master processing board (M PB)744, and a user interface control board (UI CB)746. A temporary control bus738interconnects, and provides temporary control signals between, the power supply740and the boards702,710,726,744and746. The power supply740includes a cable to be coupled to an external AC power supply. Optionally, the power supply740may include one or more power storage devices (e.g. batteries) that provide power when the AC power supply is interrupted or disconnected. The power supply740includes a controller742that manages operation of the power supply740including operation of the storage devices.

Additionally, or alternatively, the power supply740may include alternative power sources, such as solar panels and the like. One or more fans743are coupled to the power supply740and are managed by the controller742to be turned on and off based on operating parameters (e.g. temperature) of the various circuit boards and electronic components within the overall system (e.g. to prevent overheating of the various electronics).

The digital front-end boards710providing analog interface to and from probes connected to the probe interconnection board702. The DFB710also provides pulse or control and drive signals, manages analog gains, includes analog to digital converters in connection with each receive channel, provides transmit beamforming management and receive beamforming management and vector composition (associated with focusing during receive operations).

The digital front end boards710include transmit driver circuits712that generate transmit signals that are passed over corresponding channels to the corresponding transducers in connection with ultrasound transmit firing operations. The transmit driver circuits712provide pulse or control for each drive signal and transmit beamforming management to steer firing operations to points of interest within the region of interest. By way of example, a separate transmit driver circuits712may be provided in connection with each individual channel, or a common transmit driver circuits712may be utilized to drive multiple channels. The transmit driver circuits712cooperate to focus transmit beams to one or more select points within the region of interest. The transmit driver circuits712may implement single line transmit, encoded firing sequences, multiline transmitter operations, generation of shear wave inducing ultrasound beams as well as other forms of ultrasound transmission techniques.

The digital front end boards710include receive beamformer circuits714that received echo/receive signals and perform various analog and digital processing thereon, as well as phase shifting, time delaying and other operations in connection with beamforming. The beam former circuits714may implement various types of beamforming, such as single-line acquisition, multiline acquisition as well as other ultrasound beamforming techniques.

The digital front end boards716include continuous wave Doppler processing circuits716configured to perform continuous wave Doppler processing upon received echo signals. Optionally, the continuous wave Doppler circuits716may also generate continuous wave Doppler transmit signals.

The digital front-end boards710are coupled to the digital processing board726through various buses and control lines, such as control lines722, synchronization lines720and one or more data bus718. The control lines722and synchronization lines720provide control information and data, as well as synchronization signals, to the transmit drive circuits712, receive beamforming circuits714and continuous wave Doppler circuits716. The data bus718conveys RF ultrasound data from the digital front-end boards710to the digital processing board726. Optionally, the digital front end boards710may convert the RF ultrasound data to I,Q data pairs which are then passed to the digital processing board726.

The digital processing board726includes an RF and imaging module728, a color flow processing module730, an RF processing and Doppler module732and a Peripheral Component Interconnect (PCI) link module734. The digital processing board726performs RF filtering and processing, processing of black and white image information, processing in connection with color flow, Doppler mode processing (e.g. in connection with polls wise and continuous wave Doppler). The digital processing board726also provides image filtering (e.g. speckle reduction) and scanner timing control. The digital processing board726may include other modules based upon the ultrasound image processing functionality afforded by the system.

The modules728-734comprise one or more processors, DSPs, and/or FPGAs, and memory storing program instructions to direct the processors, DSPs, and/or FPGAs to perform various ultrasound image processing operations. The RF and imaging module728performs various ultrasound related imaging, such as B mode related image processing of the RF data. The RF processing and Doppler module732convert incoming RF data to I,Q data pairs, and performs Doppler related processing on the I, Q data pairs. Optionally, the imaging module728may perform B mode related image processing upon I, Q data pairs. The CFM processing module730performs color flow related image processing upon the ultrasound RF data and/or the I, Q data pairs. The PCI link734manages transfer of ultrasound data, control data and other information, over a PCI express bus748, between the digital processing board726and the master processing board744.

The master processing board744includes memory750(e.g. serial Advanced Technology Attachment (ATA) solid-state devices, serial ATA hard disk drives, etc.), a visual graphics array (VGA) board752that includes one or more graphic processing unit (GPUs), one or more transceivers760one or more CPUs752and memory754. The master processing board (also referred to as a PC board) provides user interface management, scan conversion and cine loop management. The master processing board744may be connected to one or more external devices, such as a DVD player756, and one or more displays758. The master processing board includes communications interfaces, such as one or more USB ports762and one or more ports764configured to be coupled to peripheral devices. The master processing board744is configured to maintain communication with various types of network devices766and various network servers768, such as over wireless links through the transceiver760and/or through a network connection (e.g. via USB connector762and/or peripheral connector764).

The network devices766may represent portable or desktop devices, such as smart phones, personal digital assistants, tablet devices, laptop computers, desktop computers, smart watches, ECG monitors, patient monitors, and the like. The master processing board744conveys ultrasound images, ultrasound data, patient data and other information and content to the network devices for presentation to the user. The master processing board744receives, from the network devices766, inputs, requests, data entry and the like.

The network server768may represent part of a medical network, such as a hospital, a healthcare network, a third-party healthcare service provider, a medical equipment maintenance service, a medical equipment manufacturer, a government healthcare service and the like. The communications link to the network server768may be over the Internet, a private intranet, a local area network, a wide-area network, and the like.

The master processing board744is connected, via a communications link770with a user interface control board746. The communications link770conveys data and information between the user interface and the master processing board744. The user interface control board746includes one or more processors772, one or more audio/video components774(e.g. speakers, a display, etc.). The user interface control board746is coupled to one or more user interface input/output devices, such as an LCD touch panel776, a trackball778, a keyboard780and the like. The processor772manages operation of the liquid crystal display (LCD) touch panel776, as well as collecting user inputs via the touch panel776, trackball778and keyboard780, where such user inputs are conveyed to the master processing board744in connection with implementing embodiments herein.

FIG. 8illustrates a block diagram of a portion of the digital front-end boards710formed in accordance with embodiments herein. A group of diplexers802receive the ultrasound signals for the individual channels over the PIB output808. The ultrasound signals are passed along a standard processing circuit805or to a continuous wave processing circuit812, based upon the type of probing utilized. When processed by the standard processing circuit805, a preamplifier and variable gain amplifier804process the incoming ultrasound receive signals that are then provided to an anti-aliasing filter806which performs anti-aliasing filtering.

According to an embodiment, the retrospective transmit beam focusing may be applied to the RF data directly acquired by the system or to transformed data according to different transformations as for example as a phase/quadrature (I/Q) transformation, or similar.

In the embodiment ofFIG. 8an example of the said transformation of the RF data is disclosed According to this example, the output of the filter806is provided to an A/D converter808that digitizes the incoming analog ultrasound receive signals. When a continuous wave (CW) probe is utilized, the signals therefrom are provided to a continuous wave phase shifter, demodulator and summer810which converts the analog RF receive signals to I,Q data pairs. The CW I,Q data pairs are summed, filtered and digitized by a continuous wave processing circuit812. Outputs from the standard or continuous wave processing circuits805,812are then passed to beam forming circuits820which utilize one or more FPGAs to perform filtering, delaying and summing the incoming digitized receive signals before passing the RF data to the digital processing board726(FIG. 7). The FPGAs receive focalization data from memories828. The focalization data is utilized to manage the filters, delays and summing operations performed by the FPGAs in connection with beamforming. The beamformed RF or I/Q data is passed between the beamforming circuits820and ultimately to the digital processing board726.

The digital front-end boards710also include transmit modules822that provide transmit drive signals to corresponding transducers of the ultrasound probe. The beamforming circuits820include memory that stores transmit waveforms. The transmit modules822receive transmit waveforms over line824from the beamforming circuits820.

FIG. 9illustrates a block diagram of the digital processing board726implemented in accordance with embodiments herein. The digital processing board726includes various processors952-959to perform different operations under the control of program instructions saved within corresponding memories see962-969. A master controller744manages operation of the digital processing board726and the processors952-959. By way of example, one or more processors as the952may perform filtering, the modulation, compression and other operations, while another processor953performs color flow processing. The master controller provides probe control signals, timing control signals, communications control and the like. The master controller744provides real-time configuration information and synchronization signals in connection with each channel to the digital front-end board710.

It should be clearly understood that the various arrangements and processes broadly described and illustrated with respect to theFIGS. 1-9, and/or one or more individual components or elements of such arrangements and/or one or more process operations associated of such processes, can be employed independently from or together with one or more other components, elements and/or process operations described and illustrated herein. Accordingly, while various arrangements and processes are broadly contemplated, described and illustrated herein, it should be understood that they are provided merely in illustrative and non-restrictive fashion, and furthermore can be regarded as but mere examples of possible working environments in which one or more arrangements or processes may function or operate.

Aspects are described herein with reference to theFIGS. 1-9, which illustrate example methods, devices and program products according to various example embodiments. These program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing device or information handling device to produce a machine, such that the instructions, which execute via a processor of the device implement the functions/acts specified. The program instructions may also be stored in a device readable medium that can direct a device to function in a particular manner, such that the instructions stored in the device readable medium produce an article of manufacture including instructions which implement the function/act specified. The program instructions may also be loaded onto a device to cause a series of operational steps to be performed on the device to produce a device implemented process such that the instructions which execute on the device provide processes for implementing the functions/acts specified.

One or more of the operations described above in connection with the methods may be performed using one or more processors. The different devices in the systems described herein may represent one or more processors, and two or more of these devices may include at least one of the same processors. In one embodiment, the operations described herein may represent actions performed when one or more processors (e.g., of the devices described herein) execute program instructions stored in memory (for example, software stored on a tangible and non-transitory computer readable storage medium, such as a computer hard drive, ROM, RAM, or the like).

The processor(s) may execute a set of instructions that are stored in one or more storage elements, in order to process data. The storage elements may also store data or other information as desired or needed. The storage element may be in the form of an information source or a physical memory element within the controllers and the controller device. The set of instructions may include various commands that instruct the controllers and the controller device to perform specific operations such as the methods and processes of the various embodiments of the subject matter described herein. The set of instructions may be in the form of a software program. The software may be in various forms such as system software or application software. Further, the software may be in the form of a collection of separate programs or modules, a program module within a larger program or a portion of a program module. The software also may include modular programming in the form of object-oriented programming. The processing of input data by the processing machine may be in response to user commands, or in response to results of previous processing, or in response to a request made by another processing machine.

The controller may include any processor-based or microprocessor-based system including systems using microcontrollers, reduced instruction set computers (RISC), application specific integrated circuitry (ASICs), field-programmable gate arrays (FPGAs), logic circuitry, and any other circuit or processor capable of executing the functions described herein. When processor-based, the controller executes program instructions stored in memory to perform the corresponding operations. Additionally or alternatively, the controllers and the controller device may represent circuitry that may be implemented as hardware. The above examples are exemplary only, and are thus not intended to limit in any way the definition and/or meaning of the term “controller.”

Optionally, aspects of the processes described herein may be performed over one or more networks one a network server. The network may support communications using any of a variety of commercially-available protocols, such as Transmission Control Protocol/Internet Protocol (“TCP/IP”), User Datagram Protocol (“UDP”), protocols operating in various layers of the Open System Interconnection (“OSI”) model, File Transfer Protocol (“FTP”), Universal Plug and Play (“UpnP”), Network File System (“NFS”), Common Internet File System (“CIFS”) and AppleTalk. The network can be, for example, a local area network, a wide-area network, a virtual private network, the Internet, an intranet, an extranet, a public switched telephone network, an infrared network, a wireless network, a satellite network and any combination thereof.