Patent Description:
One approach to beamforming performs so called Retrospective Transmit Beamformation (RTBF). This is a transmit focusing technology that achieves dynamic focusing by performing the transmit focusing operation retrospectively.

In Retrospective Transmit Beamforming (RTB), following a transmission event of an ultrasound transmit beam, multiple receive beams are generated. Ultrasound images are composed of a set of lines along each one of which the image system acquires image data until a full frame has been scanned.

Retrospective Transmit Beamforming uses a high parallel line acquisition scheme in which following each transmit event of a transmit beam multiple receive beams are simultaneously acquired in parallel along different lines.

According to this technique, the transmit beam is generated with a width that encompasses multiple receive lines. Generally, this can be achieved by transmitting from a small transmit aperture, for example by transmitting using a lesser number of elements of an array of transducers that the total number of transducer provided in the array. Following transmission, echoes are received which are focused along each line of the lines encompassed by the width of the transmitted beam. Focusing is obtained by delaying and summing the echoes received by the transducer elements of the receive aperture so that for generating the image of each line of the multiple lines encompassed by the width of the transmit beam, only the contribution of coherent signals along each different line location are used.

For scanning the entire image frame and acquiring all the image lines needed for generating the image, further transmit beams are transmitted by shifting the transmit aperture laterally in one direction relatively to the transmit aperture of the previous transmit event.

Lateral shift is carried out in such a way that the two adjacent transmit apertures overlap so that at least some of the receive lines encompassed by the width of a first transmit beams are also encompassed by the width of at least one or more of the following transmit beams which aperture has been progressively laterally shifted in relation to the transmit aperture of the first transmit beam.

As a result, depending on the transmit aperture of the transmission, i.e. of the number of lines encompassed by the width of the transmit beam and on the lateral shift step of the transmit aperture for each following transmit event, lines of image data along each receive line is formed by co-aligned beams along the said receive line which are combined together.

Transmission and reception continues across the image field in this manner until the full image field has been scanned. Each time the maximum number of receive lines for a given line location has been acquired, the receive lines are processed together to produce a line of image data at that location.

Due to the fact that each receive signal contributing to the same image line data at a certain receive line location derives from a transmit beam whose transmit aperture has been shifted with respect to the other transmit beams, the said receive signals contributing to the same line data are not coherent and there is the need of equalizing the phase shift variance that exists from line to line for the multilines with differing transmit-receive beam location combinations, so that signal cancellation will not be caused by phase differences of the combined signals.

In <CIT> a method and an ultrasound apparatus are disclosed which operates according to the above RTB technique.

<CIT> suggests a method for producing an ultrasound image with an extended focal range, comprising the steps of:.

According to this solution the array transducer elements are connected to a multiline receive beamformer which produces a plurality of receive lines at a plurality of corresponding line positions in response to one transmit beam at each one of a certain number of different beam locations. The multiline receive beamformer operates by using the traditional beamforming technique, namely the so called delay and sum in which the delays are determined by the relative position of the focal point of the transmit beam, the points on the receive line and the transducer position in the array. These delays are determined for all the multiline beamformers along each receiving line according to the same fixed rules which only depend on the time of arrival of the echoes from a reflecting point at a certain transducer element of an array of transducer elements.

So the traditional beamforming delays are based merely on the relative position of the reflecting point and of each of the transducer elements.

The step of equalizing the phase shift variance among receive lines at a common line position resulting from transmit beams of different transmit beam positions is carried out separately from beamforming at a later step. Equalizing further comprises relatively delaying the signals of receive lines along a common line position obtained from different transmit beams prior to combining these receive line signals together in order to receive a beamformed receive data along a certain line position.

According to this method the receive echoes relating to the same line position are firstly selected and summed by the delay and sum process of the multiline beamformer, irrespectively of the possible phase shifts introduced by the shift of the transmit aperture between the beams of the sequence of transmit events.

In a following step the phase shift of the receive signals for the same line location is equalized by a further delay which is determined as a function of the step of lateral shift of the transmit aperture between the transmit events, since the multiple receive signals along the same line position which has to be combined are obtained each one by a transmit beam which has been laterally shifted relatively to the receive line position.

Also a further weighting step of the signals of the receive lines from different transmit beams prior to combining is carried out in a separate step after multiline beamforming.

<FIG> shows a system according to the prior art <CIT> and <FIG> shows the effect of the equalizing step of the phase shift variance among receive lines at a common line position resulting from transmit beams of different transmit beam positions according to <CIT> and the method and system disclosed therein.

A transducer array comprising a number N of transducer elements of an ultrasound probe is driven by a transmit beamformer in such a way that selected groups of the transducer elements are actuated at respectively delayed times to transmit beams focused at different focal regions along the array. The echoes received by each transducer element of the array in response to each transmit beam are applied to the inputs of a multiline beamformer comprising multiline processors 210a-<NUM>. Each multiline processor 210a-<NUM> processes the each of the k parallel receive lines encompassed by every transmit beam. Each multiline processor comprises a receive beamformer which applies delays <NUM> and, if desired, apodization weights. The outputs of the multiline processors 210a-<NUM> are coupled to a line memory <NUM> which stores the received multilines until all of the R multilines needed to form a line of display data have been acquired. The group of multilines used to form a particular line of display data are applied to respective ones of multipliers 216a-216R to produce the display data for the corresponding line location. The echo data from each line may, if desired be weighted by apodization weights 214a-214R. The echoes from each line are weighted by the multipliers 216a-216R and delayed by delay lines 218a-218R. The delays are used to equalize the phase shift variance that exists from line to line for the multilines with differing transmit-receive beam location combinations, so that signal cancellation will not be caused by phase differences of the combined signals. Due to the fixed geometry of the Rx and TX paths and of the lateral shift steps of the transmit aperture in relation to the geometry of the transducer array the delays can be calculated in real time or even calculated in advance and stored in a memory, for example in the former of a table <NUM>.

The delay <NUM> and a summer <NUM> effect a refocusing of the signals received from the several receive multilines which are co-aligned in a given direction. The refocusing adjusts for the phase differences resulting from the use of different transmit beam locations for each multiline, preventing undesired phase cancellation in the combined signals.

In <FIG> the wavefront of two following transmission events TX1 and TX2 are shown. The transmit aperture of TX2 has been shifted laterally to the right in respect to TX1 by a step corresponding to the dimension of four transducer elements <NUM> of a transducer array <NUM>. The situation is illustrated in relation to the n-th transducer element as receiving element.

The two wavefronts WF1 and WF2 are in general not planar and a focus P on a receiving line coincident with the center line of the transmission beam the path TX is considered.

According to an embodiment herein the wavefronts are spherical or nearly spherical.

The echoes generated at P has to travel a path RX to reach the n-th transducer element. The Second transmit event generates a wavefront WF2 which reaches the point with a different phase due to the lateral shift of the transmit beam of the transmit event TX2.

As it appears clearly, the receive multiline beamforming delays are defined by the geometry determined by the position of each focus points along each line at each line location relatively to the position of the transducer elements of the transducer array.

The equalization process would require to compensate for the delay of the transmit beam having the wavefront WF2 in reaching the focus points P on the corresponding line, which in <FIG> is indicated as RTB delay and is represented by the difference <NUM> in position of the focus point P of the transmit beam TX1 and the point Pl.

In <FIG> the effect of the equalization process obtained by the known technique is illustrated schematically.

Considering Bp the beam signal related to focal point p and Sln(t) the signal at the probe channel n, i.e. at the n-th transducer element of the transducer array <NUM>, which is related to a difference "l" in line position between the transmit center line of a second or following transmit beam TX2 and a receive line, then the beam signal can be described by the following equation: <MAT>.

Where c is the speed of sound and <MAT> is the time at which the beam signal is focalized at point p, for l=<NUM>, which means for coincident center line of the transmit beam TX1 and receive line of the echoes.

The term <MAT> defining the delay in reaching the point p of the wave front of the transmit beam according to the l-th shift of the transmit aperture relatively to the transmit beam focused at p in a transmit event in which the receive line is coincident with the transmit beam center line and which is defined above as RTB delay <NUM>.

Further expanding the above equation <MAT>.

By using the relation <MAT> it appears clearly that the term <MAT> is the transmission beam path and the term <MAT> is the RX path to the nth transducer element of the transducer array.

It has to be noted that in the example of <FIG> and <FIG> the easiest case has been illustrated in which the receive line RX coincides with the centreline of the first transmit beam of the plurality of laterally shifted transmit beams, so that the distance "l" or the lateral shift step of the centreline of the following or second transmit beam TX2 from the receive line is identical with the lateral shift step between the centre lines of the first and of the second transmit beams TX1, TX2.

As it is shown in <FIG>, the effect of the equalisation plus focalization in reception according to the prior art is equivalent, in terms of applied delays in reception, to a traditional focalization by means of the beamforming delays at a point p̂l which is half way between point p and point pl. In this case the phase shift introduced by the shifting of the transmit aperture is not exactly compensated. In particular, the focalization delays in reception are computed relatively to the point pi, while the physical propagation delays in reception are proportional to the distance between point P and each transducer n. Therefore, the propagation delays relative to signal backscattered from point P are not exactly compensated by focalization delays applied in reception.

<CIT> also discloses an ultrasound imaging system and method with dynamic transmit beamformation. Moreover, the Whitepaper "Retrospective Transmit Beamformation" by C. Bradley (Acuson SC2000 Volume Imaging Ultrasound System, Siemens) gives an overview of techniques related to retrospective transmit beamformation (RTB).

The invention is defined by a method and system for retrospective dynamic transmit focusing beamforming of ultrasound signals according to claims <NUM> and <NUM>. Optional features are given according to the dependent claims.

In accordance with an example, a method is provided for performing retrospective dynamic transmit focusing beamforming for ultrasound signals. The method comprises the steps of:.

and in which the step e) of equalizing the phase shift is carried out concurrently with in the processing step c) and d).

For each insonification, i.e. for each transmission of a transmit beam with a certain aperture, the received echoes are processed by a set of beamformers, each one related to a different line of sight;
each beamformer being characterized by a set of dynamic delays and optionally by a set of apodization weights, which are different for each beamformer.

The delays are given by the sum of focalization delays and RTB delays, which are the phase shifts between the wave fronts of the different transmit beams centered at different transmission lines at the focal points along one receive line having a certain line location.

After beamforming each line of sight might be stored in a buffer and along with subsequent insonifications, receive lines corresponding to the same line positions are coherently summed together to produce a final beamformed line with uniform spatial resolution.

For each receive signals along a receive line position the focalization delays and the phase shift equalization delays might be applied to the receive signal contributions of the transducer elements or channels before their summation.

Differently from the retrospective dynamic transmit focusing beamforming according to the prior art in which two stages of the process are provided and carried out one after the other, namely firstly applying standard dynamic focusing on a set of receive lines and subsequently realigning each beamformed line by a proper delay and combining together the delayed lines by a weighted sum, according to the present invention beamforming and realignment -i.e. equalization- are performed jointly, by using different delays for each receive beamforming process related to each line in the multiline acquisition. In this way exact focalizations are automatically obtained.

According to the present disclosure an ultrasound system is provided that comprises:.

An apodization module might be provided applying anodization weights to the receive signals.

The system might further comprise a pre-calculated table, stored in a memory. The pre-calculated table comprises real times of arrival of the receive signals relative to a predetermined reflection point. The system might further comprise a processor configured to calculate real times of arrival of the receive signals relative to a predetermined reflection point. The processor might be configured to calculate the focalization delay for each receive signal and the phase shift among receive lines at a common line position resulting from transmit beams of different transmit beam positions and to add the focalization delays of each of the receive signals relative to a predetermined reflection point with the corresponding phase shift and apply the result of the said summation as a combined delay parameter to the said received signals.

The memory might be configured to store program instructions and the circuit includes a processor that, when executing the program instructions, is configured to apply combined delay resulting from the sum of focalization delays and phase shifts to the receive signals. Optionally, the system further comprises a processor configured to provide parallel multi-line receive (PMR) beamforming in connection with individual view lines acquired in parallel contemporaneously with a focusing function.

The beamformer is a multiline beamformer comprising a multiline processor for each receive line encompassed by the aperture or the width of each transmit beam centered on a certain transmit line position.

Each multiline processor might comprise a number of channels corresponding to the number of probe channels or transducer elements.

The present disclosure relates to a retrospective dynamic transmit focusing beamforming method for ultrasound signals by means of an ultrasound machine acquiring diagnostic images which ultrasound machine comprises an array of electroacoustic transducers arranged according to a predetermined arrangement and with predetermined relative positions from each other and which transducers are used, alternatively, for generating an excitation ultrasound wave and for receiving the reflection echoes (target) from the tissues under examination. Said reflection echoes generate electric signals corresponding to the received acoustic wave which electric signals are processed by each processing channel and are combined with each other to reconstruct an electric signal that corresponds to the combination of the contributions of the reflection signal of each transducer deriving from a certain reflection target or point,
which method comprising the following steps:.

Examples herein provide improvements to the method allowing the process to be simplified, while keeping the focusing accuracy high and while reducing the computational burden without the need for a specific particular hardware structure.

A further aim of the present disclosure is to improve the method such to allow delays and phase correction coefficients to be put in table on the basis of general geometrical characteristics of the ultrasound system and particularly of the transducer array.

Another aim is to provide a beamforming processor that allows the method according to the embodiments herein to be carried out.

A further aim is to provide an ultrasound system for acquiring diagnostic images that comprises said beamforming processor.

The above aims are achieved by methods according to what is described above wherein the phase shift correction between received echo signals from a reflecting point on a common receive line position generated by a plurality or a certain number of transmit beams having an aperture or width containing the said receive line position in order to carry out the equalization of the said receive signals is added to the focalization delays to be applied to the receive signal contribution of each transducer of the transducer array and applied to the said contribution as a combined delay correction.

Advantageously for the signal contribution of each channel a further weight is applied, the said weight is applied to the combined or summed equalized contributions of each channel for each reflection point on a common receive line position.

In order to determine the image data along a certain line position the receive line signals for a common receive line position are obtained from the multiline beamformer for each or for some of the receive line position encompassed by at least a number of transmit beams of the said plurality of transmit beams. After having beamformed the receive signals for each of the said receive lines by applying contemporaneously the focalization delays and the phase equalization delays to the receive signal contributions of each or of some selected transducer elements of the transducer array, the said receive lines are stored and combined together coherently.

The present disclosure also relates to a beamforming processor for carrying out the method described above which beamforming processor comprises:.

Each multiline processor might be provided with a unit applying an apodization weight to the receive signals of each channel of the multiline processor after applying said combined delay and phase shift correction to the said channels and before adding together the corrected contributions of each channel.

A unit might be provided for applying a RTB weight to the receive signals resulting from summation of the contributions of the channels of a multiline processor before storing the said signal in the memory for the image data lines.

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.

Further improvements and characteristics of the disclosure will be clear from the following description of some non-limiting examples schematically shown in the annexed figures wherein:.

<FIG> illustrates 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 in <FIG> can be implemented with dedicated hardware (DPSs, FPGAs, memories) and/or in software with one or more processors.

The ultrasound system of <FIG> includes one or more ultrasound probes <NUM>. The probe <NUM> may 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, <NUM>. 25D array, <NUM>. 5D array, <NUM>. 75D array, 2D array, 3D array, 4D array, etc..

The ultrasound probe <NUM> is coupled over a wired or wireless link to a beamformer <NUM>. The beamformer <NUM> includes a transmit (TX) beamformer and a receive (RX) beamformer that are jointly represented by TX/RX beamformer <NUM>. The TX and RX portions of the beamformer may be implemented together or separately. The beamformer <NUM> supplies transmit signals to the probe <NUM> and performs beamforming of "echo" receive signals that are received by the probe <NUM>.

A TX waveform generator <NUM> is coupled to the beamformer <NUM> and generates the transmit signals that are supplied from the beamformer <NUM> to the probe <NUM>. 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 beamformer <NUM> performs 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 beamformer <NUM> includes (or is coupled to) an A/D converter <NUM> that 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 controller <NUM> may be programmed to manage acquisition timing which can be generalized as a sequence of firings aimed at select reflection points/targets in the ROI. The sequence controller <NUM> manages operation of the TX/RX beamformer <NUM> in connection with transmitting ultrasound beams and measuring image pixels at individual LOS locations along the lines of sight. The sequence controller <NUM> also manages collection of receive signals.

One or more processors <NUM> perform various processing operations as described herein.

In accordance with embodiments herein the beamformer <NUM> includes an output that is configured to be coupled to an ultrasound probe <NUM> and sends signals to the transducer elements of the probe <NUM>.

According to an embodiment herein the sequencer <NUM> controls 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 ore 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 beam 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 relatively 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 beamformer <NUM> includes an input that is configured to be coupled to an ultrasound probe <NUM> and receive signals from transducers of the ultrasound probe <NUM>. The memory <NUM> stores time delays to align contributions of reflection signals received by the transducers of the array of the probe <NUM> from the reflectors in the ROI. The memory <NUM> also 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) module <NUM> is coupled to the memory <NUM> and provides various delays and corrections to the beamformer <NUM>. For example, the DPC module <NUM> directs the beamformer <NUM> to apply time delay and phase correction to the receive signals to form delayed receive signals. The beamformer <NUM> then 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 memory <NUM> may 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 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 memory <NUM> may also store weights such as apodization weights and/or RTB weights.

As explained herein, the beamformer <NUM> (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 memory <NUM> may 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 processor <NUM> may be configured to calculate real times of arrival of the receive signals relative to a predetermined reflection point. Optionally the memory <NUM> may 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 memory <NUM> may 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 processor <NUM> may be configured to calculate the said phase shift equalization delays for one or more of different transmit beams apertures or widths.

Optionally, the beamformer <NUM> circuitry 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 processor <NUM> (e.g., in connection with software RTB beamforming). For example, the memory <NUM> may store beamforming related program instructions that are implemented by the processor <NUM> to contemporaneously apply beamforming delays and phase shift equalization delays to the receive signals.

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

An image scan converter <NUM> performs 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 converter <NUM> may convert the image pixels from polar coordinates to Cartesian coordinates for image frames.

A cine memory <NUM> stores 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 display <NUM> displays various ultrasound information, such as the image frames and information measured in accordance with embodiments herein. The display <NUM> displays the ultrasound image with the region of interest shown.

A control CPU module <NUM> is configured to perform various tasks such as implementing the user/interface and 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 circuit <NUM> is provided to supply power to the various circuitry, modules, processors, memory components, and the like. The power supply <NUM> may be an A. power source and/or a battery power source (e.g., in connection with portable operation).

<FIG> illustrates a high-level block diagram of an ultrasound system implemented in accordance with embodiments herein. The ultrasound machine for acquiring diagnostic images comprises a probe <NUM> provided with an array of electroacoustic transducers intended to transform excitation electric signals sent thereto into ultrasound acoustic signals and vice versa the received acoustic signals into corresponding electric signals.

A transmit section and a receive section <NUM>, <NUM> are connected alternatively one another with the probe to provide to each individual transducer an excitation signal of the corresponding ultrasound pulse and to receive the electric signal corresponding to an acoustic pulse that has hit the transducer.

The receive signals of the transducers are each one sent in an independent manner through a dedicated channel or by a multiplexer to an analog digital converter <NUM> that samples said signals with a predetermined sampling rate and it provides output digitized receive signals of each transducer/channel.

Therefore, digitized signals are subjected to a processing by a so called beamforming processor <NUM> that carries out the time alignment of the contributions of the receive signal of each channel correspondingly to the travel time of the signal reflected by a predetermined reflection point from said reflection point to the corresponding transducer.

Since the individual transducers of the array provided on the probe have positions different from each other, they necessarily have different distances from the reflection point and therefore the echo signal deriving from such point reaches each individual reflector in a different moment.

The focusing process performs the time re-alignment of the contributions of the receive signal of each transducer deriving from the same reflection point and therefore to sum together such contributions in a coherent manner.

The process is repeated for each datum along each line forming a two-dimensional or three-dimensional image.

In the beamforming process, the receive signals are subjected to time re-alignment and phase shift equalization.

The signals obtained by the coherent sum of the time re-aligned contributions of the individual transducers and by the coherent combination of the receive signal contributions along a receive line position or line of sight due to differently laterally shifted transmit beams encompassing the said receive line position or line of sight are provided to a processing section <NUM> for generating images according to different modes such as B mode, Doppler, color Doppler, etc. that then are transmitted to a scan converter <NUM> in order to be displayed, printed, stored or subjected to other image processing.

With reference to <FIG> and <FIG> they show the block diagrams of an embodiment of a multiline beamforming processor according to the embodiments herein.

A transducer array comprising a number N of transducer elements of an ultrasound probe is driven by a transmit beamformer in such a way that selected groups of the transducer elements are actuated at respectively delayed times to transmit beams focused at different focal regions along the array. The number of the selected transducer elements may be equal or optionally and preferably smaller than the total number of transducer elements of the array of transducer elements. Different number of transducer elements may be selected for the transmit beam generation and for the receipt of the echoes signals generated by the said transmit beam.

The echoes received by each transducer element of the array in response to each transmit beam are applied to the inputs of a multiline beamformer comprising a number K of multiline processors 410a-<NUM>. The said number K corresponding to the number of receive lines falling within the aperture or width of each transmit beam.

Each multiline processor 410a-<NUM> processes the k parallel receive lines RX encompassed by every transmit beam TX. Each multiline processor applies contemporaneously focalization beamforming delays <NUM> and phase shift equalization delays <NUM> to the receive signal and if desired, apodization weights to weight the received echoes from the array elements.

The focalization beamforming delays are applied to the receive signal contributions of each transducer element of the array in order to re-align the said receive signal contribution in relation to the relative position of each transducer element and each reflection point on a certain receive line or a certain line of sight.

In a RTB beamforming system the phase shift equalization delays are applied to the received signals of each reflecting point on a certain receive line of on a certain line of sight in order to coherently re-align the phases of the receive signals along a certain receive line position deriving each from a transmit beam having different lateral shifts relating to the said receive line position of the said line of sight.

As it appears clearly for each of the k-receive lines encompassed by a transmit beam width the phase shift equalization data are different and thus each of the multiline processors 410a-<NUM> are differentiate one from the other by the said RTB delays (i.e. the said phase shift equalization delays) which apply for the receiving line K processed by the corresponding multiline processor.

The RTB delays are used to equalize the phase shift variance that exists from line to line for the multilines with differing transmit-receive beam location combinations, so that signal cancellation will not be caused by phase differences of the combined signals. Due to the fixed geometry of the Rx and TX paths and of the lateral shift steps of the transmit aperture in relation to the geometry of the transducer array the delays can be calculated in real time or even calculated in advance and stored in a memory, for example in the form of a table.

The outputs of the multiline processors 410a-<NUM> are coupled to a line memory <NUM> which stores the received multilines until all of the R multilines needed to form a line of display data have been acquired. The group of receive lines R along a common receive line position are used to form a particular line of display data and the number R of the receive lines is equal or less than the number of receive lines K falling within the width of a transmit beam TX.

The R receive lines are combined in a summer <NUM>.

The combined signal by the summer <NUM> is fed to an image processor <NUM>, which converts the coherently summed receive signals in image data along a corresponding line of sight and in a displayable image according to one or more of the previously described processing units and methods.

<FIG> shows the architecture of a multiline processor of the multiline beamformer according to an embodiment of the present invention, identical functional blocks or having identical functions as in <FIG> have the same reference numbers.

The receive signals of the N transducer elements are fed to N-dedicated processing channels <NUM> of a multiline processor <NUM>. A multiplier <NUM> applies to the receive signals of each channel a BMF weight which considers for example apodization and/or the position of the corresponding transducer element relatively to the receive line. The said BMF-weight being stored in a memory <NUM> as a pre-calculated value or as a value calculated by a processor unit.

Each channel of the multiline processors <NUM> is provided with a circuitry <NUM> for applying a beamforming delay and a RTB delay i.e. a phase shift equalization delay.

According to an embodiment herein the beamforming or focalization delays are calculated considering the different time of arrival of the echoes from a reflection point. The delays applied to such signal contribution of each transducer element and thus of each channel carry out the time alignment of the contributions of the receive signal of each channel correspondingly to the travel time of the signal reflected by a predetermined reflection point from said reflection point to the corresponding transducer element. Since the individual transducers of the array provided on the probe have positions different from each other, they necessarily have different distances from the reflection point and therefore the echo signal deriving from such point reaches each individual reflector in a different moment.

According to a more general embodiment, the focalization data may be computed separately for each transducer array and for each focus point of each of the receive line positions. Similarly, the phase shift equalization delays has to be determined separately for each focus point on each receive line position encompassed by the transmit beam aperture.

This more general case applies also to the focalization weights <NUM> of <FIG>.

This more general case finds application in combination with phased array or virtual convex probes which do not allow to define a common rule for determining the focusing delays the phase shift equalization delays and the apodization weights.

The above is clearly expressed in the <FIG>, <FIG> and <FIG> where the weights and the focusing delays (Focalization Data) are indicated as a function of the parameters N: number of probe channels; K = number of parallel RX lines per TX line and P = number of pixels per line.

The phase shift equalization delays (RTB Data) and the phase shift equalization weights (RTB weights) are expressed as a function of K = number of parallel RX lines per TX line and P = number of pixels per line.

Considering other kind of probes, a fixed rule may be defined allowing to more easily generate the pre-calculated tables of delay or weight values and even direct and real time calculation of the delay values.

In this particular case the focalization delays (BMF delay) and the focalization weights (BMF weight) are calculated as a function of the channel N and of the pixel per line P, whereas RTB delays and RTB weights are calculated, as in the general case, as a function of receive line K and pixel per line P. It has to be noted that since the pitch between adjacent transducer elements along the one dimensional or bi-dimensional array of transducer is identical for every transducer element of the said array, the beamforming or focalization delays realigning the signal contribution processed by each one of the channels are identical for every multiline processor, while the RTB delay for equalizing the phase shift between the receive signals along the same line position or line of sight which are due to differently laterally shifted transmit beams are different for every one of the multichannel processors <NUM> each one dedicated to processing the multiline signals along a certain receive line position or line of sight.

According to one embodiment the RTB delays may be pre-calculated for a certain transmit beam aperture or width and thus for a certain number of receive line positions which fall within the said certain width or aperture of the transmit beams. Optionally RTB delays can be pre-calculated for a set of different transmit beams width or apertures so that image data acquisition can be carried out by selecting a certain transmit beam aperture or width. Optionally RTB delays may be pre-calculated also in combination with different measures of the lateral shift step. The said circuitry <NUM> for applying the Beamforming delays and the RTB delays to each signal processed by each channel may comprise a memory configured to store the RTB delays according to one or more of the above variants. Optionally the said RTB delays may be pre-calculated by an external processor unit or by a processor unit associated or comprised in the said circuitry <NUM>.

The signal contributions of each channel <NUM> to which the apodization weights has been applied and to witch the beamforming delay related to the corresponding channel and the RTB delay related to the receive line position to which a corresponding multiline processor <NUM> is associated are fed to a summer <NUM> which adds together the signal contributions of the channels <NUM> having bean realigned in relation of their time of arrival by the beamforming delays and being subjected to a phase shift equalization which provides for compensating the phase shift between the receive signals along a common receive line position or line of sight which are due to the fact that the said receive signals are generated by the echoes from reflectors on the common receive line position but deriving from different transmit beams each one being shifted in a different measure from the said receive line position i.e. having a different lateral distance from the said receive line position.

In one embodiment shown in <FIG> the summed, realigned and phase equalized receive signal contribution of each channel may be subjected by a further weighting by a RTB weight.

The said RTB weight modulates the relevance of the receive signals processed by each of the multiline processors <NUM> in relation to the position of the receive line position associated to the multiline processor <NUM> relatively to the transmit beam or to the position of the reflecting point.

In embodiment herein the RTB weight which is different for every multiline processor <NUM> may be stored in memory <NUM> and may be applied to the receive signal provided by the adder <NUM>.

According to an embodiment the multiline processors comprise each a multiplier <NUM> for applying the said RTB weights to the said signal processed by the adder <NUM>.

According to the embodiment of <FIG>, the beamformed data along a receive line position processed by each multiline processor 410a to <NUM> are stored in a memory <NUM>. The receive signals along a certain receive line are then coherently summed. The number of coherently summed receive lines can be chosen and can be maximally equal to the number of receive lines encompassed by each transmit beam.

The coherently summed multiline contributions along a certain line of sight or a certain receive line position are fed to an image processing unit which converts the beamformed data in displayable image data and which can be configured according to one or more of the embodiments described herein according to known image processing techniques applied in ultrasound imaging.

<FIG> illustrates the principle of the method according to which the embodiments described above operates.

<FIG> shows the wavefront WF1 and WF2 of two following transmission events TX1 and TX2 are shown.

The example of <FIG> has been simplified by being limited to a special case in which the receive line RX considered is coincident with transmit center line TX1. The transmit aperture of the transmit beam TX2 has been shifted laterally to the right in respect to TX1 by a step corresponding to the dimension of four transducer elements <NUM> of a transducer array <NUM>. It is presumed that the aperture of the transmit beam TX2 or the width of the transmit beam TX2 is such as to encompass the receive line RX and the reflecting point P.

The situation is illustrated in relation to the n-th transducer element as receiving element.

The two wavefronts WF1 and WF2 are in general not planar and a focus P on a receiving line coincident with the center line of the transmission beam the path TX1 is considered.

The line TX2 is the center line of the laterally shifted second transmit beam.

The echoes generated at P have to travel a path RX to reach the n-th transducer element. The Second transmit event generates a wavefront WF2 which reaches the point with a different phase due to the lateral shift of the transmit beam of the transmit event TX2.

The equalization process would require to compensate for the delay of the transmit beam having the wavefront WF2 in reaching the focus points P on the corresponding line. In <FIG> and <FIG> this phase shift is defined as RTB delay and is represented by the difference <NUM> in position of the focus point P of the transmit beam TX1 and the point Pl. This situation apply here identically.

Considering Bp the beam signal related to focal point p and Sln(t) the signal at the probe channel n, i.e. at the n-th transducer element of the transducer array <NUM>, which is related to a difference "l" in line position between the transmit center line of a second or following transmit beam TX2 and a receive line RX on which the focus point P lies, then the beam signal can be described by the following equation: <MAT>.

In which:
the term <MAT> is the path of the receive signal contribution to the n-th transducer element <NUM> of the transducer array <NUM>.

The term <MAT> is the path of the transmit beam TX2 along the centerline of the said transmit beam when the wavefront WF2 reaches the focus point P.

Expanding the above equation the following equation is obtained: <MAT>.

In which
The term <MAT> corresponds to the beamforming or focalization delay to be applied to each of the n transducer elements <NUM> of the transducer array;.

The term <MAT> defining the delay in reaching the point p of the wave front WF2 of the transmit beam TX2 according to the l-th shift of the transmit aperture relatively to the transmit beam focused at p in the transmit event TX1: Thus the above term is the RTB delay to be applied for equalizing the phase shift between the receive signals from the focus point P on the receive line RX when combining the receive signals along said common line position RX originated by the two transmit events TX1 and TX2 the corresponding transmit beams being differently laterally shifted in relation to the said receive line position RX (in the example <NUM>=<NUM> for TX1 and l=<NUM> for TX2).

It has to be noted that in the present example of the method according to the invention the Phase shift of the wave fronts of differently laterally shifted transmit beams reaching a focus point P along a common receive line position RX are exactly compensated so that no signal attenuation or cancellation is caused when combining the receive signals along the common line opposition together because the phases of the transmit beams are exactly synchronised.

A comparison with the prior art methods, the result of which is illustrated in <FIG>, shows that while the effect of the equalisation according to the prior art is equivalent to focalize at a point p̂l half way between point p and point pi, the phase shift equalisation according to the present invention which is carried out contemporaneously with the realigned signal contributions by means of the beamforming delays provides for an exact focussing on the focus target point P.

<FIG> shows a simplified diagram of the method according to the present invention.

Four different main phases are provided in the embodiment of <FIG>.

A first phase <NUM> relates to receipt of the receive signals following a multiline transmission mode, a processing of the receive signals in order to generate beamformed receive line data which contemporaneously have been subjected to a phase shift equalization related to the difference between receive line position relatively to the transmit beam aperture. During this phase also apodization weights are applied to the receive signals and the single channel contribution for each receive line position are summed for generating the said receive line signals.

In a following phase <NUM>, according to the embodiment described in <FIG> weights are applied to each of the k receive lines corresponding to a transmit beam line TX, i.e. falling within the aperture or width of the transmit beam TX. All the said selected receive line signals are stored in a memory.

The following phase <NUM> provides for generating image line data by summing together a number R of co-aligned receive line signals in order to generate for every receive line position a Beamformed data.

In the phase <NUM> at step <NUM> receive data is received by the transducer elements of the transducer array of a probe for a number of focus points or pixels (numpoint) distributed over a target region or ROI. The target region or ROI may be mono-dimensional, bi-dimensional, three-dimensional or four-dimensional.

The receive signals are related to echoes generated by a multiline technique consisting in a plurality of transmit events each one comprising at least a transmit beam. Each transmit beam having a certain aperture or width encompassing a plurality of receive lines having different line positions each receive line comprising a number of focus points or pixels. The transmit beam of each transmission event covering a certain width of the ROI and the transmit beams of each following transmit event of the said plurality of transmit events being laterally shifted for a certain lateral displacement relatively to the previous transmit event. The lateral displacement being such that each receive line position falls within the width of the transmit beams of two or more following transmit events.

Thus each transmit event provides receive line signals along a common receive line position which receive line signals have to be coherently summed in order to obtain image data along the said receive line position or line of sight.

At step <NUM> RTB delays (phase shift equalization delays) related to each receive line position of the number of receive line positions encompassed by the transmit beam width are summed and the delay resulting from this sum is applied al step <NUM> to the receive signal contribution of each channel (transducer element) for each of the receive line positions falling within the width of the transmit beams.

At step <NUM> apodization weights are applied by multiplication to the received signal contributions to which the summed RTB delays and beamforming delays has been applied at the previous step <NUM>.

For each of the receive line positions encompassed by the transmit beam width, the receive signal contributions from each channel to which the RTB delay and the beamforming delay has been applied at <NUM> and to which the apodization weights has been applied at <NUM> are summed together at <NUM>.

In the following phase <NUM> to the receive line signals related to each receive line position or viewline encompassed by the transmit beams at step <NUM> a RTB data weight is applied by multiplication of this weight.

At step <NUM> each receive line signal is stored in a memory.

At phase <NUM> a summation step <NUM> is carried out by which the receive line signals falling on a common receive line or viewline position and deriving from different transmission event are coherently summed together forming beamformed image line data along each of a different view line or line of sight. The said number of view lines covering at least a part of the entire target region or one or more particular ROI's in this target region.

According to a further embodiment illustrated in <FIG>, the present RTB beamforming method may provide steps of selecting the parameters for the transmit events for scanning the target region.

According to an embodiment a step <NUM> of choosing the number of transmit events is provided. Optionally a steps <NUM> is provided for defining the transmit beam aperture or width for each transmit event. Optionally <NUM> the said transmit beam aperture or width may be different <NUM> and <NUM> for at least a part of the said transmit beam events.

According to an embodiment the method further comprises the step <NUM> of defining the lateral shift between following transmit beam events. Optionally <NUM> said step of lateral shift may be different <NUM>, <NUM> for at least part of the transmit beam events.

According to still another embodiment of the method of the present invention following the selection of the transmit beams an activation scheme of the multiline processors of the multiline beamformer is defined according to which the number of multiline processor which is activated corresponds to the number of receive lines falling within the width of the transmit beam which is represented by the step <NUM> of configuring the TX/RX beamformer according to the selected parameters.

According to an embodiment an ultrasound system is provided comprising a user interface for inputting data, the said user interface sending input data to a processor which provides for configuring the transmit and the receive beamformer according to the input data.

According to an embodiment the said input data comprise the number of transmit events. Optionally the said input data comprises the transmit beam aperture or width for each transmit event.

According to an embodiment the said input data comprises the lateral shift between following transmit beam events.

According to an embodiment illustrated in <FIG> the input data interface <NUM> cooperates with the CPU <NUM> for inputting the various commands and setting parameters for controlling the ultrasound system.

CPU112 configures the different units according to the inputted parameters. Firing protocols are governed by the sequencer controller <NUM> by which applies the input data relating to the number of transmit events and/or the transmit beam aperture or width for each transmit event and/or the lateral shift between following transmit beam events.

<FIG> illustrates a block diagram of an ultrasound system formed in accordance with an alternative embodiment. The system of <FIG> implements 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 board <NUM> that includes one or more probe connection ports <NUM>. The connection ports <NUM> may support various numbers of signal channels (e.g., <NUM>, <NUM>, <NUM>, etc.). The connector ports <NUM> may be configured to be used with different types of probe arrays (e.g., phased array, linear array, curved array, 1D, <NUM>. 25D, <NUM>. 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 ports <NUM> may support acquisition of 2D image data and/or one or more of the connection ports <NUM> may 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) <NUM> includes a switching circuit <NUM> to select between the connection ports <NUM>. The switching circuit <NUM> may be manually managed based on user inputs. For example, a user may designate a connection port <NUM> by selecting a button, switch or other input on the system. Optionally, the user may select a connection port <NUM> by entering a selection through a user interface on the system.

Optionally, the switching circuit <NUM> may automatically switch to one of the connection ports <NUM> in response to detecting a presence of a mating connection of a probe. For example, the switching circuit <NUM> may receive a "connect" signal indicating that a probe has been connected to a selected one of the connection ports <NUM>. The connect signal may be generated by the probe when power is initially supplied to the probe when coupled to the connection port <NUM>. Additionally, or alternatively, each connection port <NUM> may include a sensor <NUM> that detects when a mating connection on a cable of a probe has been interconnected with the corresponding connection port <NUM>. The sensor <NUM> provides signal to the switching circuit <NUM>, and in response thereto, the switching circuit <NUM> couples the corresponding connection port <NUM> to PIB outputs <NUM>. Optionally, the sensor <NUM> may be constructed as a circuit with contacts provided at the connection ports <NUM>. The circuit remains open when no mating connected is joined to the corresponding connection port <NUM>. The circuit is closed when the mating connector of a probe is joined to the connection port <NUM>.

A control line <NUM> conveys control signals between the probe interconnection board <NUM> and a digital processing board <NUM>. A power supply line <NUM> provides power from a power supply <NUM> to the various components of the system, including but not limited to, the probe interconnection board (PIB) <NUM>, digital front end boards (DFB) <NUM>, digital processing board (DPB) <NUM>, the master processing board (M PB) <NUM>, and a user interface control board (UI CB) <NUM>. A temporary control bus <NUM> interconnects, and provides temporary control signals between, the power supply <NUM> and the boards <NUM>, <NUM>, <NUM>, <NUM> and <NUM>. The power supply <NUM> includes a cable to be coupled to an external AC power supply. Optionally, the power supply <NUM> may include one or more power storage devices (e.g. batteries) that provide power when the AC power supply is interrupted or disconnected. The power supply <NUM> includes a controller <NUM> that manages operation of the power supply <NUM> including operation of the storage devices.

Additionally, or alternatively, the power supply <NUM> may include alternative power sources, such as solar panels and the like. One or more fans <NUM> are coupled to the power supply <NUM> and are managed by the controller <NUM> to 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 boards <NUM> providing analog interface to and from probes connected to the probe interconnection board <NUM>. The DFB <NUM> also 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 boards <NUM> include transmit driver circuits <NUM> that generate transmit signals that are passed over corresponding channels to the corresponding transducers in connection with ultrasound transmit firing operations. The transmit driver circuits <NUM> provide 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 circuits <NUM> may be provided in connection with each individual channel, or a common transmit driver circuits <NUM> may be utilized to drive multiple channels. The transmit driver circuits <NUM> cooperate to focus transmit beams to one or more select points within the region of interest. The transmit driver circuits <NUM> may 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 boards <NUM> include receive beamformer circuits <NUM> that 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 circuits <NUM> may implement various types of beamforming, such as single-line acquisition, multiline acquisition as well as other ultrasound beamforming techniques.

The digital front end boards <NUM> include continuous wave Doppler processing circuits <NUM> configured to perform continuous wave Doppler processing upon received echo signals. Optionally, the continuous wave Doppler circuits <NUM> may also generate continuous wave Doppler transmit signals.

The digital front-end boards <NUM> are coupled to the digital processing board <NUM> through various buses and control lines, such as control lines <NUM>, synchronization lines <NUM> and one or more data bus <NUM>. The control lines <NUM> and synchronization lines <NUM> provide control information and data, as well as synchronization signals, to the transmit drive circuits <NUM>, receive beamforming circuits <NUM> and continuous wave Doppler circuits <NUM>. The data bus <NUM> conveys RF ultrasound data from the digital front-end boards <NUM> to the digital processing board <NUM>. Optionally, the digital front end boards <NUM> may convert the RF ultrasound data to I,Q data pairs which are then passed to the digital processing board <NUM>.

The digital processing board <NUM> includes an RF and imaging module <NUM>, a color flow processing module <NUM>, an RF processing and Doppler module <NUM> and a PCI link module <NUM>. The digital processing board <NUM> performs 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 board <NUM> also provides image filtering (e.g. speckle reduction) and scanner timing control. The digital processing board <NUM> may include other modules based upon the ultrasound image processing functionality afforded by the system.

The modules <NUM> - <NUM> comprise 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 module <NUM> performs various ultrasound related imaging, such as B mode related image processing of the RF data. The RF processing and Doppler module <NUM> convert incoming RF data to I,Q data pairs, and performs Doppler related processing on the I, Q data pairs. Optionally, the imaging module <NUM> may perform B mode related image processing upon I, Q data pairs. The CFM processing module <NUM> performs color flow related image processing upon the ultrasound RF data and/or the I, Q data pairs. The PCI link <NUM> manages transfer of ultrasound data, control data and other information, over a PCI express bus <NUM>, between the digital processing board <NUM> and the master processing board <NUM>.

The master processing board <NUM> includes memory <NUM> (e.g. serial ATA solid-state devices, serial ATA hard disk drives, etc.), a VGA board <NUM> that includes one or more graphic processing unit (GPUs), one or more transceivers <NUM> one or more CPUs <NUM> and memory <NUM>. The master processing board (also referred to as a PC board) provides user interface management, scan conversion and cine loop management. The master processing board <NUM> may be connected to one or more external devices, such as a DVD player <NUM>, and one or more displays <NUM>. The master processing board includes communications interfaces, such as one or more USB ports <NUM> and one or more ports <NUM> configured to be coupled to peripheral devices. The master processing board <NUM> is configured to maintain communication with various types of network devices <NUM> and various network servers <NUM>, such as over wireless links through the transceiver <NUM> and/or through a network connection (e.g. via USB connector <NUM> and/or peripheral connector <NUM>).

The network devices <NUM> may 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 board <NUM> conveys ultrasound images, ultrasound data, patient data and other information and content to the network devices for presentation to the user. The master processing board <NUM> receives, from the network devices <NUM>, inputs, requests, data entry and the like.

The network server <NUM> may 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 server <NUM> may be over the Internet, a private intranet, a local area network, a wide-area network, and the like.

The master processing board <NUM> is connected, via a communications link <NUM> with a user interface control board <NUM>. The communications link <NUM> conveys data and information between the user interface and the master processing board <NUM>. The user interface control board <NUM> includes one or more processors <NUM>, one or more audio/video components <NUM> (e.g. speakers, a display, etc.). The user interface control board <NUM> is coupled to one or more user interface input/output devices, such as an LCD touch panel <NUM>, a trackball <NUM>, a keyboard <NUM> and the like. The processor <NUM> manages operation of the LCD touch panel <NUM>, as well as collecting user inputs via the touch panel <NUM>, trackball <NUM> and keyboard <NUM>, where such user inputs are conveyed to the master processing board <NUM> in connection with implementing embodiments herein.

<FIG> illustrates a block diagram of a portion of the digital front-end boards <NUM> formed in accordance with embodiments herein. A group of diplexers <NUM> receive the ultrasound signals for the individual channels over the PIB output <NUM>. The ultrasound signals are passed along a standard processing circuit <NUM> or to a continuous wave processing circuit <NUM>, based upon the type of probing utilized. When processed by the standard processing circuit <NUM>, a preamplifier and variable gain amplifier <NUM> process the incoming ultrasound receive signals that are then provided to an anti-aliasing filter <NUM> which performs anti-aliasing filtering.

According to an embodiment the retrospective transmit beam focusing according to the present invention 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 of <FIG> an example of the said transformation of the RF data is disclosed According to this example, the output of the filter <NUM> is provided to an A/D converter <NUM> that 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 summer <NUM> which 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 circuit <NUM>. Outputs from the standard or continuous wave processing circuits <NUM>, <NUM> are then passed to beam forming circuits <NUM> which 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 board <NUM> (<FIG>). The FPGAs receive focalization data from memories <NUM>. 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 circuits <NUM> and ultimately to the digital processing board <NUM>.

The digital front-end boards <NUM> also include transmit modules <NUM> that provide transmit drive signals to corresponding transducers of the ultrasound probe. The beamforming circuits <NUM> include memory that stores transmit waveforms. The transmit modules <NUM> receive transmit waveforms over line <NUM> from the beamforming circuits <NUM>.

<FIG> illustrates a block diagram of the digital processing board <NUM> implemented in accordance with embodiments herein. The digital processing board <NUM> includes various processors <NUM>-<NUM> to perform different operations under the control of program instructions saved within corresponding memories see <NUM> - <NUM>. A master controller <NUM> manages operation of the digital processing board <NUM> and the processors <NUM> - <NUM>. By way of example, one or more processors as the <NUM> may perform filtering, the modulation, compression and other operations, while another processor <NUM> performs color flow processing. The master controller provides probe control signals, timing control signals, communications control and the like. The master controller <NUM> provides real-time configuration information and synchronization signals in connection with each channel to the digital front-end board <NUM>.

It should be clearly understood that the various arrangements and processes broadly described and illustrated with respect to the FIGS. , 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 the FIGS. , 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.

In embodiments utilizing a web server, the web server can run any of a variety of server or mid-tier applications, including Hypertext Transfer Protocol ("HTTP") servers, FTP servers, Common Gateway Interface ("CGI") servers, data servers, Java servers, Apache servers and business application servers. The server(s) also may be capable of executing programs or scripts in response to requests from user devices, such as by executing one or more web applications that may be implemented as one or more scripts or programs written in any programming language, such as Java®, C, C# or C++, or any scripting language, such as Ruby, PHP, Perl, Python or TCL, as well as combinations thereof. The server(s) may also include database servers, including without limitation those commercially available from Oracle®, Microsoft®, Sybase® and IBM® as well as open-source servers such as MySQL, Postgres, SQLite, MongoDB, and any other server capable of storing, retrieving and accessing structured or unstructured data. Database servers may include table-based servers, document-based servers, unstructured servers, relational servers, non-relational servers or combinations of these and/or other database servers.

The embodiments described herein may include a variety of data stores and other memory and storage media as discussed above. These can reside in a variety of locations, such as on a storage medium local to (and/or resident in) one or more of the computers or remote from any or all of the computers across the network. In a particular set of embodiments, the information may reside in a storage-area network ("SAN") familiar to those skilled in the art. Similarly, any necessary files for performing the functions attributed to the computers, servers or other network devices may be stored locally and/or remotely, as appropriate. Where a system includes computerized devices, each such device can include hardware elements that may be electrically coupled via a bus, the elements including, for example, at least one central processing unit ("CPU" or "processor"), at least one input device (e.g., a mouse, keyboard, controller, touch screen or keypad) and at least one output device (e.g., a display device, printer or speaker). Such a system may also include one or more storage devices, such as disk drives, optical storage devices and solid-state storage devices such as random access memory ("RAM") or read-only memory ("ROM"), as well as removable media devices, memory cards, flash cards, etc..

Such devices also can include a computer-readable storage media reader, a communications device (e.g., a modem, a network card (wireless or wired), an infrared communication device, etc.) and working memory as described above. The computer-readable storage media reader can be connected with, or configured to receive, a computer-readable storage medium, representing remote, local, fixed and/or removable storage devices as well as storage media for temporarily and/or more permanently containing, storing, transmitting and retrieving computer-readable information. The system and various devices also typically will include a number of software applications, modules, services or other elements located within at least one working memory device, including an operating system and application programs, such as a client application or web browser. It should be appreciated that alternate embodiments may have numerous variations from that described above. For example, customized hardware might also be used and/or particular elements might be implemented in hardware, software (including portable software, such as applets) or both.

Various embodiments may further include receiving, sending, or storing instructions and/or data implemented in accordance with the foregoing description upon a computer-readable medium. Storage media and computer readable media for containing code, or portions of code, can include any appropriate media known or used in the art, including storage media and communication media, such as, but not limited to, volatile and non-volatile, removable and non-removable media implemented in any method or technology for storage and/or transmission of information such as computer readable instructions, data structures, program modules or other data, including RAM, ROM, Electrically Erasable Programmable Read-Only Memory ("EEPROM"), flash memory or other memory technology, Compact Disc Read-Only Memory ("CD-ROM"), digital versatile disk (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices or any other medium which can be used to store the desired information and which can be accessed by the system device. Based on the disclosure and teachings provided herein, a person of ordinary skill in the art will appreciate other ways and/or methods to implement the various embodiments.

The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.

While the disclosed techniques are susceptible to various modifications and alternative constructions, certain illustrated embodiments thereof are shown in the drawings and have been described above in detail. It should be understood, however, that there is no intention to limit the invention to the specific form or forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions falling within the scope of the invention, as defined in the appended claims.

The use of the terms "a" and "an" and "the" and similar referents in the context of describing the disclosed embodiments (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms "comprising," "having," "including" and "containing" are to be construed as open-ended terms (i.e., meaning "including, but not limited to,") unless otherwise noted. The term "connected," when unmodified and referring to physical connections, is to be construed as partly or wholly contained within, attached to or joined together, even if there is something intervening. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein and each separate value is incorporated into the specification as if it were individually recited herein. The use of the term "set" (e.g. , "a set of items") or "subset" unless otherwise noted or contradicted by context, is to be construed as a nonempty collection comprising one or more members. Further, unless otherwise noted or contradicted by context, the term "subset" of a corresponding set does not necessarily denote a proper subset of the corresponding set, but the subset and the corresponding set may be equal.

Operations of processes described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. Processes described herein (or variations and/or combinations thereof) may be performed under the control of one or more computer systems configured with executable instructions and may be implemented as code (e.g., executable instructions, one or more computer programs or one or more applications) executing collectively on one or more processors, by hardware or combinations thereof. The code may be stored on a computer-readable storage medium, for example, in the form of a computer program comprising a plurality of instructions executable by one or more processors. The computer-readable storage medium may be non-transitory.

Claim 1:
A method for performing retrospective dynamic transmit focusing beamforming for ultrasound signals,
the method comprising the steps of:
a) transmitting a plurality of transmit beams from an array transducer, each transmit beam being centered at a different position along the array and each transmit beam having a width or an aperture encompassing a plurality of laterally spaced line positions, each transmit beam width or aperture overlapping at least partially at least the width or the aperture of the immediately adjacent transmit beam or of more laterally spaced transmit beams;
b) receiving echo signals with the array transducer;
c) processing the echo signals received in response to one transmit beam to produce a plurality of receive lines of echo signals at the laterally spaced line positions within the width or the aperture of the transmit beam;
d) repeating the receiving step b) and the processing step c) for the additional transmit beams of the plurality of transmitted transmit beams of step a);
e) equalizing the phase shift variance among receive lines at a common line position resulting from transmit beams of different transmit beam positions;
f) combining echo signals of receive lines from different transmit beams which are spatially related to a common line position to produce image data; and
g) producing an image using the image data;
and in which the step e) of equalizing the phase <NUM> shift is carried out contemporaneously with the processing step c) and d);
wherein for each transmission of a transmit beam with a certain aperture, the received echoes are processed by a set of beamformer processors (410a - <NUM>), each one related to a different line of sight, with each beamformer having a set of dynamic delays and optionally having a set of apodization weights, which are different for each beamformer;
said delays are given by the sum of focalisation delays and retrospective transmit beamforming (RTB) delays, which are the phase shifts between the wave fronts of the different transmit beams centered at different transmission lines at the focal points along one receive line having a certain line location.