METHOD FOR OPERATING AN ULTRASOUND SYSTEM AND SYSTEM FOR PERFORMING THE METHOD FOR OPERATING AN ULTR

专利摘要:
method for beam intensification and ultrasound imaging system. beam intensification through side lobe reduction and/or main lobe sharpening is shown. modalities utilize dynamic resolution techniques, enhanced dynamic resolution and/or enhanced dynamic resolution to synthesize beams, such as ultrasonic beams used in ultrasonic imaging, having desired attributes. modalities simultaneously form a first sample beam and a second, or auxiliary, sample beam for each sample to synthesize intensified scan beams. according to dynamic resolution techniques in this document a new beam can be formed from the sum of the two sample beams. a dynamically resolving beam synthesized from modalities reduced side lobes with relatively little or no main lobe scattering. an enhanced dynamic resolution beam sharpening function can be applied to provide a more intensified beam, such as to further narrow the main lobe.
公开号:BR112012010958B1
申请号:R112012010958-8
申请日:2010-11-09
公开日:2021-09-08
发明作者:Juin Jet Hwang
申请人:Sonosite, Inc；
IPC主号:

专利说明:

field of invention
[0001] This disclosure refers to beam formation and more particularly to systems and methods for beam enhancement, such as through side lobe reduction and/or main lobe formation. Background of the invention
[0002] In sonographic systems, acoustic signals are transmitted by a digitizing head to a body or other subject and reflected signals are received by the digitizing head for image processing. The reflected signals are used by the sonographic system to form images of the structure of matter in the body (eg, patient tissue) or other matter of interest. An ultrasonic probe used in such sonographic images is typically a handheld housing that contains one or more independent transducers and possibly other electronics.
[0003] The transducers of a sonographic system with an ultrasonic probe convert electrical energy into mechanical energy (acoustic) radiating away from its surface when transmitting and mechanical energy (acoustic) impinging on its surface into electrical energy when receiving electrical energy. An individual piece of transducing material is called an element, which is often fabricated as a specific geometric shape, such as a rectangle. Typically, these transducer elements are arranged in a regular pattern (an array), with their centers arranged as a line to form a linear array or in-phase array, along an arc to form a curved array, or in a grid to form a curved array. form a 2D matrix. Typically this regular pattern of transducer elements has a repeated spacing as measured from element center to element center, which is called a pitch. Transducer elements in sonographic image processing operations are often used in groups. The total span of a group of transducer elements in a dimension is the opening in that dimension. For example, for a linear array, one dimension is the height of the transducer element, while the other dimension is the number of transducer elements used times the step.
[0004] An ultrasound beam can be formed, either in transmit or receive operation, through proper use of the preceding groups of transducer elements. For example, a receive beam is formed by adjusting one or more attributes of the transducer element signals (e.g., delaying and/or weighting to provide transducer element beamforming signals corresponding to the selected aperture transducer elements) and summing these beamforming signals from the transducer element to provide a formed beam signal having a peak response signal corresponding to a given point (the specific point being a "focal point"). The foregoing transducer element signal attributes are referred to herein as beamforming parameters. Such beamforming parameters are typically used to form beams to reject clutter (eg unwanted reflected signals, etc.) from unwanted areas (eg directions other than a desired “direction of observation”).
[0005] In particular, delays are applied to signals from the transducer element of the transducer element group, such that if a narrow pulse were emitted from the focal point, the signals having been thus delayed would arrive at a summing device at the same time and , therefore, would not result in the higher value. This same narrow pulse coming from any point other than the focal point would not simultaneously arrive at the summing device and therefore would not sum to be such a large signal. A beam having a specific shape (eg width, length, direction, etc.) can be formed using appropriate beam forming parameters. For example, it can be formed into a main lobe that is “pointed” in a desired “observation” direction.
[0006] Regardless of the application of delays to create beams, an aperture can be apodized. Apodization is the process of applying potentially unique gain (weighting) values to transducer element signals before they are summed. Specific apodization functions can be applied to apertures to generate beams having desired attributes, such as reduced side lobes, and thus still reject clutter. There are many standard weighting functions that can be applied to an aperture, but there are three that are particularly exemplary. These are uniform weighting (also known as rectangular, box car, unapodized sync), Hanning weighting (also known as Hann) and cosine weighting. The Hanning weighting (l+cos(x)) and the cosine weighting (cos(x)) are related to each other where the Hanning weighting is a function of high cosine. Other math functions that can be used for aperture apodization in ultrasound imaging systems are Hanning, Blackman-Harris, or other application-specific window functions.
[0007] The beam formed by the uniformly weighted aperture is called a Sinc beam, the beam formed by the weighted Hanning aperture is called the Hanning beam and the beam formed by the aperture weighted by the cosine function is called apodized cosine beam. An object is examined by sequentially displacing an ultrasound beam (eg Sync beam, Hanning beam or apodized cosine beam to form an image. Depending on the implementation, an ultrasound image can be formed by Sync beam or Hanning beam or others types of bundles.
[0008] When beamforming parameters (eg delays) are continuously adjusted so that the focal point moves along a particular direction, a dynamically focused beam is created. In providing a scanning beam for sonographic imaging, these dynamic beams are typically formed so that the focal point follows a straight line in Cartesian space for linear arrays or along a single apex angle for phased or curved arrays . For example, by sequentially adjusting the beamforming parameters of the transducer element signals a series of beams can be formed to scan a volume of interest (e.g., a certain area or depth within a patient can be scanned). Information from a plurality of such digitized beams can be aggregated to generate an image of the digitized volume of interest (eg, an ultrasound image of the patient's subdermal portion). For example, in B-mode ultrasound operation, an image is generated from multiple lines of echo data received from a plurality of ultrasound beams from different observation directions (e.g., digitized beams in different observation directions). Such digitized beam imaging is referred to in this document as digitized volume imaging.
[0009] It is known that the monochromatic signal acquired by the Harming beam is mathematically equal to the sum of the acquired signal of the Sinc beam with the average of the acquired signals of two spatially displaced neighboring Sinc beams, provided that these beams are spaced according to the Nyquist's theorem. That is, the first null of the left Sync beam and the first null of the right Sync beam must be aligned with the peak of the center of the Sync beam. Based on these properties, by processing signals acquired from three adjacent Nyquist spaced Sync beams, a technique has been proposed to improve performance in radar applications. However, in ultrasound formation, the line density is selected according to various parameters of the optimal image quality system, thus adjusting the sampling spacing from beam to beam or scan line to scan line, from according to Nyquist's criterion generally cannot be satisfied. Furthermore, in ultrasound imaging dynamic beamforming, as can be used in providing the aforementioned digitized sample beams, is generally implemented in conjunction with a variable aperture. In other words, different aperture sizes are used to form beams at different depths. Thus, the Disorder Reduction technique based on Sync beam processing, such as can be implemented by radar, often cannot be adopted for use in digitized volume imaging ultrasound.
[0010] Figure 1A illustrates said digitized volume image. Specifically, transducer 11 having transducer elements E1 to EN shown in Figure 1A can be operated to provide such a digitized volume image. In operation, transducer element signals from transducer elements E1 to EN are processed to receive beams directed to specific areas within the volume being imaged 15. These beams can be formed to collect information about objects (also known as objects of interest) within imaged volume 15, such as object 12 (eg, fluid filled region) and object 13 (eg tissue structure) present below surface 16 (eg, the skin surface).
[0011] It should be appreciated that the higher the signal to signal disorder ratio (eg, beam-formed signals) used in processing digitized volume images, the greater the contrast resolution (eg, better tissue differentiation ) on the generated image. One source of disorder signal is the aforementioned side lobes which normally accompany the main lobes of the generated beams. The presence of unwanted side lobes in association with the desired major lobes can be seen in the illustration of Figure 1A. Specifically, the main lobes illustrated in Figure 1A each have side lobes associated with them (e.g. SL5 side lobes associated with the ML5 main lobe, the combination of which is shown in a dashed line portion to help distinguish these lobes of the composite representation). The number and level of side lobes and their structures define how much of their unwanted off-axis echoes are integrated into the resulting beam-formed signal, thus scrambling the desired echoes of the object of interest. The ability to reduce side lobes improves contrast resolution or differentiability of objects of interest, such as tissue in an image.
[0012] Another source of image degradation is the width of the main lobes used to collect image information. For example, the main lobe width defines how an object within a volume being imaged is propagated through the beam. Thus, the width of the main lobe is usually related to the detailed resolution of an image. Thus, it is often desirable that the beams formed for the aforementioned digitization have a narrow focus so that objects of interest in the images can be generated well defined.
[0013] From the above description it can be appreciated that the width of the main lobe, the level of the side lobes and the structure of the side lobes (for example, how fast the side lobes leave the main lobe) are of great importance for the quality of Image. For example, higher resolution images can be achieved with very sharp beams.
[0014] Signal processing for imaging using transducer 11 of Figure 1A may include beamforming using a selected aperture (for example, a selected group of transducer elements, such as transducer elements E11 to E15) implementing parameters of suitably beamforming (e.g., delays and/or weights) for the transducer element signals received by the transducer elements of the selected aperture. For example, beamforming delay parameters can be selected to provide ML11-ML15 main lobes having desired focal points (eg applying appropriate delays to provide beams to digitize a given volume depth being imaged/imaged 15). Furthermore, the beamforming process may involve applying proper weighting (apodization process) to the signals received from the transducer elements of the selected aperture, such as to reduce the side lobes associated with the main lobes. Thus, the beamforming parameters used in beam generation can include complex values such that the signal received from the transducer elements can be modified both in magnitude and in phase.
[0015] While generally reducing the side lobes of the beam, the use of the aperture apodization process spreads the main lobe. Undesirable results associated with the use of the foregoing typical beamforming using an apodization process are illustrated by Figures 1B - 1D. Figure 1B shows tissue mimic ghost 150 (generally representing the volume being imaged 15 shown in Figure 1A), which is composed of the fluid-filled region A on the left (such as may correspond to a portion of the volume being imaged in Figure 1A comprising object 12) and tissue region B on the right (such as may correspond to a portion of the volume being imaged of Figure 1A comprising object 13). The fabric region B is assumed to comprise a group of stitch spreaders (eg 14 stitch spreaders) of equal spread cross sections. An image is formed when a volume being imaged, represented here by the tissue mimic ghost 150, is insonified with a sequence of ultrasound beams formed by the linear array of El-EN elements. Since small scattering intensity will be received from fluid filled region A, the resulting image (in an ideal situation) would contain no gray scale displayed for fluid filled region A, while tissue region B would display a distribution of dots with intensity similar to those shown in the mimic ghost.
[0016] As discussed above, in conventional ultrasound imaging systems, the opening of an array is either apodized with a deterministic mathematical function to partially suppress the side lobes (thus enlarging the main lobe) for image contrast enhancement or non-apodized to maintain a narrower main lobe, thus producing a smaller image spot size with high clutter. Each results in a degradation of image quality and will display a distorted image.
[0017] Figure 1C shows the two different beam configurations discussed above to illustrate the problem. The Bu beam is a non-apodized beam (eg a Sync beam formed using a uniform weighting function to define the beamforming weight distribution) providing a narrower main lobe having relatively high level side lobes. The BH beam is an apodized beam (eg a Hanning beam formed using an increased cosine weighting function to define the beamforming weight distribution) providing a wider main (diffusion) lobe having side lobes with relatively levels low. The magnitude of the beams illustrated in Figure 1C is logarithmically compressed and the side lobes are cut and gradually rolled outward.
[0018] It is assumed that the Bu and BH beams are used for the same image area, specifically a part of the tissue B region of the tissue mimic ghost 150 of Figure 1B. The Bu beam generates the object representation of interest 101 (as can be used in an image aggregation generated by digitizing a plurality of Bu beams in different focal directions within the area represented by the tissue mimic ghost 150) resulting from reflected signals ( for example, reflected by dot spreaders 14) received by the main lobe. The Bu beam still generates artifacts 101-1 to 101-8 (also as they can be aggregated into an image generated as undesirable clutter) resulting from reflected signals received by the side lobes. Likewise, the BH beam generates object representation of interest 100 (as can be used in the aggregation of an image generated by digitizing a plurality of BH beams in different focal directions within the area represented by the mimic tissue ghost 150) resulting from reflected signals (eg reflected by 14 point spreaders) received by the main lobe. The BH beam still generates artifacts 100-1 to 100-4 (also as they can be aggregated into an image generated as undesirable clutter) resulting from reflected signals received by the side lobes. As can be seen in Figure 1C, although the same area of an object has been imaged, the object-of-interest representation 100 as provided by the BH beam is spread out compared to the object-of-interest representation 101 provided by the Bu beam. Also, as can be seen in Figure 1C, more (albeit smaller) artifacts are generated by the Bu beam (artifacts 101-1 to 101-8) than artifacts generated by the BH beam (artifacts 100-1 to 100-4).
[0019] A sonographic image A can be generated by mapping a plurality of both Bu beam and BH beam to insonify a volume being imaged. For example, the representations created by a respective mapping of one of the Bu and BH beams across the area represented by the tissue mimic ghost 150 can be aggregated to form an image of an object of interest. However, as can be appreciated from the illustration in Figure 1C, when using a Bu beam, the object of interest in the generated image can be relatively sharp, because the object of interest representations (eg, object of interest representation 101) they are relatively small, but the number of artifacts (eg, artifacts 101-1 to 101-8) is high as a result of the more prominent side lobes. The artifacts associated with the use of the Bu beam also extend a long distance from those corresponding to the representations of the object of interest, further degrading the generated image. Also, it can be appreciated from the illustration in Figure 1C, when using BH beam, the object of interest in the generated image is less accentuated, because the representations of the object of interest (eg representation of the object of interest 100) are relatively large , but the number of associated artifacts (eg, artifact 100-1 through 100-n) is low as a result of less prominent side lobes. Furthermore, the artifacts associated with the use of the BH beam extend a shorter distance from the representation of the object of interest. Each of the above beamforming techniques therefore results in generated images that are often of a lower quality than desired. As can be appreciated from the background, achieving a well-defined beam without significant side lobes to provide quality images has become elusive. Brief summary of the invention
[0020] The present invention is intended for systems and methods that provide side lobe beam reduction, such as through the use of dynamic resolution (DR) beam synthesizing techniques. Dynamic beamforming resolution techniques of embodiments of the invention provide enhanced main lobe beam attributes as well as provide side lobe beam reduction by synthesizing a DR beam from a plurality of beams (referred to as sample beams).
[0021] Modalities implement a DR beam synthesis technique by acquiring a plurality of beam signals formed from sample beams for each scanned area of a volume being imaged. For example, either a first sample beam (eg a non-apodized beam, such as can be formed using a cosine function to define the beamforming weight distribution) and a second sample beam (eg a beam apodized as can be formed using a cosine function to define the beamforming weight distribution) are formed for each scanned area (eg each observation direction) of a volume being imaged (eg tissue areas ). The resulting sample beam signals (for example, the beam signal formed using an apodized function and the beam signal formed using an apodized function) are used to synthesize a beam formed signal corresponding to that of a signal from a high resolution low side lobe by operating the DR beamforming techniques contained in this document. In accordance with preferred embodiments of the invention, sample beams can be weighted and combined in a DR beamforming technique to produce a minimized total power. The resulting DR beam preferably narrows the side lobes with relatively little or no main lobe propagation.
[0022] In techniques of synthesizing an enhanced dynamic resolution (IDR) beam of modalities, a DR beam is segmented to synthesize an IDR beam having desired attributes. For example, a DR beam can be segmented into its main lobe component and its side lobe component, such as using a sample beam (eg the second sample beam mentioned above). Such beam components are preferably independently manipulated or otherwise processed, such as to change one or more attributes of them (eg applying different weighting). The IDR beam synthesizer technique here operates to synthesize IDR beams from the manipulated segmented beam components (eg, a higher weighting for the main lobe component and lower weighting coefficient for the sidelobe component) by recombining these beam components to synthesize an IDR beam.
[0023] The sharpening function can be applied to DR/IDR beams, if desired, to provide an even more intensified beam. DR/IDR beams having a sharpening function applicable to them are referred to herein as enhanced dynamic resolution (XDR) beams. XDR beams, having had a sharpening function applied, provide a main lobe that is narrower than the corresponding DR/IDR beam. Furthermore, the side lobes of such XDR beams can be further suppressed by one level for better image quality.
[0024] Although IDR and XDR beam processing modalities can utilize beam synthesis of DR beam processing as discussed above, the use of DR beam synthesis is not a limitation on the application of the concepts in this document. For example, sharpening processing modalities of IDR and/or XDR beams can be applied in relation to the Sync beam and the apodized cosine beam without using the DR beam (eg minimum energy beam by processing Sync beams and apodized cosine ).
[0025] A feature of the embodiments of the invention is to optimize the focus performance of each beam sample formed in the sample space of a generated image. Another feature of embodiments of the invention is to reduce spectral leakage and improve spectral resolution in pulse wave ("PW"), continuous wave ("CW") and color flow processing with or without coded excitation and code patterns. A further feature of the invention is that embodiments can easily be adapted for use in many types of systems, such as multiple beamforming lines, synthetic aperture beamforming and high structure rate beamforming.
[0026] Modalities of the concepts in this document can be applied to ultrasonic imaging to provide a reduction of the sidelobe beam. However, the concepts in this document are not limited to applicability to ultrasound image processing. Modalities can be applied to visible light, infrared, radio frequency and other imaging techniques.
[0027] The foregoing part has outlined a little, in general lines, the technical characteristics and advantages of the present invention so that the detailed description of the invention that follows can be better understood. Additional features and advantages of the invention will be described below which are the subject of the claims of the invention. It should be appreciated by those skilled in the art that the design and specific embodiment disclosed can easily be used as a basis for modifying or creating other structures to accomplish the same purposes as the present invention. It should also be realized by persons skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention set out in the appended claims. The innovative features believed to be characteristic of the invention, as far as its organization and functioning, together with other objects and advantages will be better understood from the following description when considered in connection with the attached figures. It is expressly understood, however, that each of the figures is provided for purposes of illustration and description only and is not intended as a definition of the limits of the present invention. Brief description of the drawings
[0028] For a more complete understanding of the present invention, references are now made to the following descriptions taken in conjunction with the accompanying drawings, in which:
[0029] Figures 1A to 1C illustrate the need for side lobe reduction and the problems inherent in trying to reduce the side lobes in a conventional manner;
[0030] Figures 2A and 2B show a system adapted to provide dynamic resolution processing, increased dynamic resolution and/or improved dynamic resolution according to embodiments of the invention;
[0031] Figure 3A shows examples of a first sample beam and a second sample or auxiliary beam that can be used by a dynamic resolution beam synthesis technique, in accordance with embodiments of the invention;
[0032] Figure 3B shows an example of a dynamic resolution beam as can be synthesized from the sample beams of Figure 3A, in accordance with embodiments of the invention;
[0033] Figure 4 shows a representation of an image generated using a DR beam of an embodiment of the invention;
[0034] Figures 5A and 5B show details of embodiments of the system in Figure 2, adapted to synthesize a dynamic resolution beam, as in Figure 3B, according to embodiments of the invention;
[0035] Figure 6 illustrates an example of operation of the DR-XDR processor of figures 5A and 5B, according to embodiments of the invention;
[0036] Figures 6A to 6C illustrate combining the signals of a first sample beam signal and a second sample or auxiliary beam signal for dynamic resolution beam synthesis, according to the operation of a process of Figure 6, according to modalities;
[0037] Figures 6D to 6I(3) illustrate the isolation of a main lobe signal component from a first sample beam signal for higher dynamic resolution beam synthesis, according to the operation of a process of Figure 6 according to modalities;
[0038] Figures 6J-6L(4) illustrate the use of a beam shaping function in the operation of an improved dynamic resolution beam synthesis iteration, according to the operation of a process of Figure 6, according to modalities;
[0039] Figures 7A to 7C are graphs of examples of sample beams and an enhanced dynamic resolution beam synthesized therefrom, according to embodiments of the present invention;
[0040] Figure 8 shows an example of the concepts of this invention applied to a dimensional transformation;
[0041] Figure 9 shows several processed beams using different sets of parameters, according to embodiments of the invention;
[0042] Figure 10 shows the relationships between the various processed beams, according to embodiments of the invention;
[0043] Figure 11 illustrates the difference between the magnitude of the two main lobe beam signals when a large amplification factor is applied to an auxiliary sample beam of an embodiment of this document;
[0044] Figure 12 shows an example of a beam shaping function used, according to an embodiment of the invention;
[0045] Figures 13A and 13B show the division of the main lobe to reduce the residual from main lobe to side lobe of a dynamically resolving beam and the resulting beam;
[0046] Figure 14 shows an example of an enhanced dynamic resolution beam, after several iterations of an embodiment of the present invention;
[0047] Figures 15 to 15G show the generation of new signal components with different beam properties, according to an embodiment of the invention; and
[0048] Figures 16A to 16E show beams used in the decomposition and synthesis of beams, according to embodiments of the invention. Detailed description of the invention
[0049] Figure 2A shows an embodiment of an adapted ultrasound imaging system, according to an embodiment of the invention. It should be appreciated that the exemplary modality is described with reference to ultrasonic imaging in order to provide a more concrete example to help understand the concepts presented here. However, the concepts of the present invention are not limited to ultrasound image processing application. Thus, the concepts presented here can be applied with respect to a number of technologies, in which reflection of transmitted signals is used, such as visible light, infrared and radio frequency imaging techniques.
[0050] Ultrasound imaging system 200 is shown comprising a system unit 210 in communication with scan head 220. The modalities system unit 210 comprises a processor-based system operable to control a transducer (e.g., the transducer 11 shown in Figure 1A) of scan head 220 for transmitting and receiving ultrasound signals using digitized beams 221 to provide digitized volume images. In this regard, the modalities system unit 210 processor-based system processes the received ultrasound signals to generate the image 211, displayed on the display 212, representing a portion of the volume being imaged 201. to be adapted in accordance with the imaging concepts of the present invention is provided in commonly transferred, co-pending patent application US 12/467,899 entitled "Modular Apparatus for Diagnostic Ultrasound", the disclosure of which is incorporated herein by reference. .
[0051] Additional details regarding an ultrasound imaging system modality 200 are shown in the high-level functional block diagram of Figure 2B. As shown in Figure 2B, a scan head transducer 220 may include an array of ultrasonic elements (eg transducer 11 of Figure 1A with transducer elements E1 to EN) in communication with transmit/receive circuits 221 (such as may include amplifiers, stores, multiplexers, etc.) and controllably operable to transmit and receive ultrasound signals.
[0052] The system unit 210 of Figure 2B comprises a beamformer 213, DR/IDR/XDR beam synthesis processor 214, ultrasound image processing circuitry 215 and display display 212. The beamformer 213 operates to provide beamforming with respect to signals supplied to/from transducer 11. The DR/IDR/XDR 214 beam synthesis processor operates to provide dynamic resolution beam synthesis processing as described in this document. Ultrasound image processing circuits 215 operate to form ultrasound images (eg, B-mode, M-mode, Doppler-mode, 3D, 4-D, etc.) using dynamic resolution (eg, DR, IDR, and /or XDR) of beam signals synthesized by the DR/IDR/XDR 214 beam synthesis processor, such as for display on display display 212.
[0053] It should be appreciated that additional and/or alternative functional blocks to those illustrated in Figure 2B may be used, in accordance with embodiments of the invention. For example, one or more analog to digital converters (ADC) and/or digital to analog converters (DAC) may be used, such as where digital beamforming or digital signal processing is implemented by the ultrasound imaging system 200 Furthermore, the functional blocks can be distributed differently than shown in Figure 2A. For example, a beamformer 213 may be disposed on scan head 220, such as where a "fine wire" connection is desired between scan head 220 and system unit 210.
[0054] It is possible to optimize the signal ratio to signal disorder associated with interrogated tissue sites based on an adaptive beamforming process, as can be implemented by beamformer 213. In an adaptive beamforming process , a series of amplitude and phase matrix operations of the signals of all transducer elements (or some selected subset of transducer elements) are used for each sample location. Normally, the dimension of the array is proportional to the dimension of the opening of the array. When the aperture is large as in a conventional ultrasound imaging system, eg 32, 64 or 128, the processing power required for implementation is very high and can be prohibitive for some system applications.
[0055] Sample beamformers 213a and 213b of beamformer 213 use a delay and sum beamforming process to generate formed beam signals for interrogated tissue locations within a digitized volume, according to modalities . Delay and sum beam formation is done by integrating the signal received from the transducer elements (all or some of the selected subsets of the transducer elements) after the arrival time differences between transducer elements are compensated for. The original beam output is a formed beam signal that changes its magnitude and phase depending on the distribution of the tissue scattering cross sections.
[0056] In operation, according to an embodiment, a first set of beamforming parameters (e.g., a first set of delay and/or weighting) provides the first sample beam simultaneously with a second set of beamforming parameters (eg, a second delay and/or weighting set) providing the second sample beam. For example, the sample beam of beamformer 213a may implement a first set of beamforming parameters to form a first sample beam (e.g., a non-apodized beam), the sample beam of beamformer 213b may implement a second set of beamforming parameters to form a second sample or auxiliary beam (eg, an apodized beam). Therefore, beamformer sample beams 213b and 213a simultaneously provide two different formed beam signals for dynamic resolution processing, in accordance with embodiments of the invention.
[0057] From the foregoing, it should be appreciated that, in a beam formed signal, signals from a plurality of transducer elements (all or some selected subsets of transducer elements) are integrated into a single beam formed signal . Thus, the phase and amplitude of the signal (eg echo signal) received at the individual transducer elements are lost. It is, therefore, a technical challenge to improve the beam signal formed post beamforming. However, using the DR, IDR and/or XDR beam synthesis concepts in this document, it is possible to improve the beam performance post beamforming.
[0058] Modalities of the ultrasound imaging system 200 implement enhanced dynamic resolution (DR) beam synthesis and/or extended dynamic resolution (XDR) synthesis techniques described in this document. For example, a DR beam synthesis technique can be applied by the DR/IDR/XDR beam synthesis processor 214 of the ultrasound imaging system 200 by acquiring a plurality of beam formed signals provided by, for example, beamformers of sample 213a and 213b of beamformer 213 for each examined area of an object (eg tissue) being imaged to synthesize a DR beam. The signal from a synthesized DR beam may be further processed by the DR/IDR/XDR 214 beam synthesis processor of the ultrasound imaging system 200, such as using segmentation techniques described in this document, to provide IDR and/or IDR beam synthesis XDR.
[0059] A DR beam synthesis technique, in accordance with embodiments of the invention simultaneously acquires two formed beam signals from an interrogated tissue site. For example, a first sample beam (eg Bu beam of Figure 3A) and a second sample or auxiliary beam (eg A beam of Figure 3A) are formed using beamformer 213 for each sample point in each examined area (eg each focal direction) of volume being imaged 201. One way to minimize the side lobes in a synthesized DR beam (eg the Bo beam of Figure 3B) is by forming such sample beams having phase, shape, and magnitude that minimize side lobes when sample beams are combined to synthesize the DR beam. Thus, as can be appreciated from the illustration in Figure 3, the modalities sample beams are adapted to provide peaks and nulls that cooperate to synthesize a DR beam having desired attributes when these sample beams are combined. That is, the side lobes associated with a first sample beam Bu(θ) can be reduced using a second or auxiliary sample beam A(θ) to result in a better quality DR beam Bo(θ).
[0060] Modalities of a DR beam synthesis technique of the present invention to minimize side lobes can be implemented with a first sample beam formed without any apodization and a second sample beam or auxiliary sample beam formed by aperture apodization using a cosine function (for example, cos (θ)). For example, a non-apodized pattern beam (Bu beam in Figure 3A) of an array can be described by a sinc sinc(θ) function. The sinc(θ) function is oscillating with zero crossing at θ = ± nπ or sinc(± π) = 0, whereas the sinc(θ) = 1. If a pattern beam of a matrix is apodized using the cosine function ( for example, a beam A in Figure 3A), the apodized cosine beam is symmetrically divided into two Sync beams of geometrically displaced components, whose two peaks are aligned with the first side lobe of the non-apodized beam, with a null placed at the origin A(0) = 0; A is the second sample beam or the apodized cosine beam. Thus, the cosine apodized beam can be used as an auxiliary sample beam for side lobe reduction when applied to a non-apodized sample beam formed using a Sync function. It should be appreciated that although a Sync beam and a non-apodized cosine beam are mentioned to demonstrate the DR beam synthesis process, other combinations of sample beams can be used to process image reconstruction signals with improved image quality, according to the concepts of the present invention.
[0061] The sample formed beam signals resulting from sample beams are used by the DR/IDR/XDR 214 beam synthesis processor of Figure 2B to synthesize a signal corresponding to a DR beam (for example, Bo of Figure 3B) of the present invention. For example, using the geometric and/or morphological properties of the sample beams, signals from the sample beams are combined to synthesize a DR beam having desired characteristics. When sample beams have geometric and/or morphological properties that combine to cancel out undesirable attributes (eg, side lobes), modalities DR beam synthesis can operate to sum the sample beams (eg Bo = Bu + A) . However, where sample beams provide geometric and/or morphological properties that combine to increase undesirable attributes (eg side lobes), modalities DR beam synthesis may work to subtract the sample beams (eg Bo = Bu - A). Therefore, it should be appreciated that the mathematical relationships provided herein with respect to the use of sample beams in DR beam synthesis can implement a change in signal depending on the combining/cancellation characteristics of the particular sample beams used.
[0062] As will be better understood from the discussion that follows, α in the examples above defines a fractional amount of the signal received from the second sample beam that is used to cancel out the unwanted parts of the first sample beam. The α parameter is used, according to modalities to provide a balance between side lobe and main lobe reduction spreading in DR beam synthesis. Accordingly, DR beams synthesized by operating the dynamic resolution beamforming techniques of this document preferably have reduced side lobes with relatively little or no main lobe scattering.
[0063] The following discussion is offered to help better understand the DR beam in the process of synthesizing embodiments of the invention. When the first beam sample Bu(θ) is used to scan a volume being imaged, the resulting beam formed signal is Iu(θ) received by scanning the first sample beam Bu(θ) on object O(θ) and can be described as Iu {θ} =jO(Φ - θ)* Bu (Φ - θ)dΦ. It is assumed that this first sample beam Bu(θ) can be decomposed into two components BuM(θ) and BuS(θ), where the beam component BuM(θ) is the desired beam component (eg the lobe main) and the beam component BuS(θ) is the unwanted beam (eg side lobes) and where Bu(θ)=BuM(θ)+BuS(θ). Thus, Iu(θ)=jO(Φ-θ)*Bu(Φ-θ)dΦ=IuM(θ)+IuS(θ) .
[0064] The second sample beam A(θ) may be an auxiliary beam that “looks” or points in the same direction (θ) as the first sample beam Bu(θ). It is assumed that this second sample beam A(θ) can also be decomposed into two components AM(θ) and AS(θ), where A(θ) = AM(θ)+ AS(θ). Thus; IA(θ) =jO(Φ- θ)* A(Φ- θ)dΦ= IAM(θ)+ IAS(θ)From the above, the DR beam BO(θ) can be formed, according to Bo (θ) = Bu(θ) + αA(θ) = BuM(θ) + αAM(θ) + BuS(θ) + αAS(θ). Thus, the side lobe signal BuS(θ) can be reduced by determining
[0065] In order not to degrade the main lobe of the DR beam, according to embodiments of the invention, it is desirable that the resulting beam signal component of the main lobe of the second or auxiliary sample beam αIM(θ) be as non-zero αIAM (θ) usually results in at least some main lobe diffusion BuM(θ) in synthesized DR beam BO(θ) . In order not to change the gaze or the pointing direction of the sample beam Bu(θ), when combined with the second sample beam A(θ), the second sample beam A(θ) of modalities comprises a null placed in correspondence with the main lobe BuM(θ) of the first sample beam. In other words, if A(0) = 0 and B0(0) = BuM(0), then when the side-lobe clutter energy is minimized as a result of the Bu(θ) +αA(θ) cancellation process, the gaze and pointing direction of BuM(θ) will not change, except the main lobe may diffuse a little due to the BuM(θ)+αAM(θ) process.
[0066] The alpha parameter, α, can be delimited by the predetermined minimum and maximum values. For example, the modalities alpha parameter is preferably limited between 0 and 1 to avoid errors resulting from data acquisition or other numerical processes. It should be appreciated that there may be situations where canceling the clutter signal from one sample beam (eg, the preceding Sync beam) using the signal from a second sample beam (eg, apodized cosine beam) is not practical. For example, when the clutter level is unusually high or the signal from an undesirable direction is so high that greater than the best sidelobe beam cancellation performance than readily achieved from the second sample beam may be desired. In such a situation, the parameter value can be set to a predetermined maximum acceptable value (eg 1), in accordance with embodiments of the invention.
[0067] Alpha being zero represents a situation, where the side lobe is weak in the first sample beam (eg Sync beam) and no signal is needed from the second sample or auxiliary beam (eg apodized cosine beam) for side lobe cancellation in DR beam synthesis. In contrast, when alpha equals 1, signals received in the second or auxiliary sample beam (eg, apodized cosine beam) assigned to the side lobes are required for sidelobe cancellation of the first sample beam (eg, beam Sync) for DR beam synthesis. Thus, in the Sync beam/modal apodized cosine beam DR beam synthesis example, where α = 0, the synthesized DR beam is the Sync beam (Bo = Bu + αA = Bu + 0A = Bu), whereas where α = l, the synthesized DR beam is a high cosine beam or Harming beam (Bo = Bu + αA = Bu + 1A). α values between 0 and 1 give a synthesized DR beam main lobe varying in width between the main lobe of the Sinc beam and the main lobe of the high apodized cosine beam, with reduced side lobes, according to a fractional amount of the signal received from the apodized cosine bundle of the side lobes.
[0068] Optimization processes can be implemented to calculate the amount of signals needed from the second sample or auxiliary beam (eg, apodized cosine beam) for the cancellation of unwanted parts of the first sample beam (eg, Sync beam) . Although different function objective choices can be used in an optimization process, in the process of synthesizing DR beam of modalities of the present invention. A criterion based on minimizing the strength of disorder signals in the beam can be chosen to calculate the parameter α described above. That is, the parameter of the embodiments of the present invention effectively defines the fractional amount of the second sample or auxiliary beam signal to be combined with the first sample beam signal to synthesize a DR beam and thus an objective function to select the α parameter, such that when the sample beams are combined, the strength of the clutter signals is minimized and can be chosen according to modalities.
[0069] In the process of synthesizing DR beam of modalities of the present invention, the α parameter can be dynamically changed from sample to sample (for example, focal direction to focal direction). Since the modalities parameter α is chosen, minimizing total beam disorder forces based on measurement of sample beams (eg Sync beam and apodized cosine beam) in the sidelobe cancellation process, a good balance of resolution Contrast and detail can be obtained for each sample in a DR-processed image. For example, at a sample site where the side lobe is high, the α parameter can be set to a high or higher binding threshold (eg 1 in the example above), and the second sample beam is used to synthesize a DR beam having a low side lobe whose attenuation rate is fast. However, the main lobe width of the synthesized DR beam may propagate by the influence of the second sample beam, and thus the image resolution may be poorer. In a sample location where little clutter is received from its neighbor, the α parameter can be set to a low limit or lower limit (eg 0 in the example above), and the second sample beam remains essentially unused in synthesizing a beam DR. Since no apodization is used in such a modality, the main lobe of the synthesized DR beam is narrow. Thus, the sidelobe cancellation parameter in an image ranges from zero to one in the previous example. As a result, the DR beam synth process effectively produces the best possible balance of detail and contrast resolution in an image.
[0070] To illustrate the above concepts, the Bo beam of Figure 3B shows a representation of a DR beam B0(θ) synthesized from the sample beam signals of the sample beams Bu and A (for example, B0(θ) = Bu(θ) + αA(θ), where a = 1). The lateral lobe of the Bo bundle has been greatly reduced. However, the main lobe has been relatively enlarged compared to the main lobe of the Sinc beam, as shown by W1 of Figure 3A and W2 of Figure 3B. Although, such main lobe diffusion generally reduces the resolution of the resulting image, improved image quality is provided by the DR beam of such a modality by balancing the main lobe against slight diffusion and significantly reducing side lobes.
[0071] Figure 4 shows a representation of an image generated using synthesized DR beams, according to an embodiment of the invention. In particular, Figure 4 illustrates image 460, showing an object of interest (eg, object of interest from representations 400 aggregating to represent an object of interest) within a volume being imaged, as generated by beam sweep (eg Bu and A sample beams of Figure 3A) to synthesize a DR sample beam (eg DR Bo beam of Figure 3B). As shown in Figure 3B, the dynamic range of the image display 460 corresponds to the information in the beam signal DR between the lower cut-off point, GL and the upper cut-off point, GH. Side lobe artifacts are not visible in the 460 image because the side lobes of the synthesized DR beams drop rapidly and the images that the side lobes create are below the GL lower cutoff point. The generated images corresponding to spot spreaders 14 are slightly distributed only in image 460 because of the reduction in the main lobe width of the DR beam. Thus, the image texture is well preserved and few or no artifacts are present in the A or B regions of the 460 image.
[0072] Figures 5A and 5B show additional details of modalities of the ultrasound imaging system 200 adapted to synthesize a DR beam (for example, the DR Bo beam of Figure 3B) using a plurality of sample beams (for example, beams of sample Bu and A from Figure 3A). The exemplary systems of Figures 5A and 5B use beamformer 213 to form two sample beam signals for DR beam synthesis. The beamformer 213 of illustrated embodiments comprises various signal processing, weighting and circuit combinations as may be operated under control of a control processor, such as a DR/IDR/XDR 214 beam synthesis processor, to form the sample beam signals as described in this document.
[0073] In the illustrated embodiments, the signals provided from the transducer element (for example, transducer element E1 - EN as shown in Figure 1A) are processed by amplifiers 51-1 to 51-N, as may include low noise amplifiers providing amplification signal transducer for subsequent beamforming processing. Elements 52-1 through 52-N provide signal phase adjustment (delay) for each transducer element signal and elements 53-1 through 53-N provide signal amplitude adjustment (weighting) for each transducer element signal. Thus, elements 52-1 to 52-N and 53-1 to 53-N both apply beamforming parameters to the signals from the transducer element. Combiners 54 and 55 provide combining (e.g., summing) the signals from the transducer element to form a resultant beam signal. Therefore, elements 52-1 through 52-N and combiner 55 cooperate to provide sample beam from beamformer 213a of embodiments of the present invention and elements 52-1 through 52-N, elements 53-1 through 53-N and the combiner 54 cooperate to provide beam sample from beamformer 213b of modalities.
[0074] In the embodiment of Figure 5A, suitably, the delayed signals from the transducer element are combined in combiner 55 to provide a Sync beam signal as the aforementioned first sample beam signal. Suitably the weighted and delayed transducer element signals are combined in combiner 54 to provide an apodized cosine beam signal as the second sample or auxiliary beam signal as mentioned above. In operation, according to an embodiment of the invention, the Sync beam and the apodized cosine beam are formed simultaneously (for example, using the same set of transducer element signals).
[0075] The conditioning and/or processing of the beam signal can be provided, according to previous embodiments, to, in combination with or after processing the DR beam synthesis, if desired. For example, the apodized cosine beam signal of the illustrated embodiment is provided for quadrature bandpass filter 56-1, while beam signal Sync is provided for quadrature bandpass filter 56-2 to facilitate processing of beam synthesis. DR in vector space. Additional or alternative sample beam signal conditioning may include analog to digital conversion (eg where a digital signal processor (DSP) is used in DR beam synthesis here), amplification, noise cancellation, etc.
[0076] The Sync beam signal and apodized cosine beam signal are provided to the DR/IDR/XDR 214 beam synthesis processor of the illustrated embodiment for DR beam signal synthesis. The embodiment of the DR/IDR/XDR 214 beam synthesis processor illustrated in Figure 5A includes a plurality of beam processing circuits, shown here as DR 511 processing, IDR 512 processing, and XDR 513 processing to provide dynamic transformation resolution as described. in this document. However, it should be appreciated that embodiments of the invention cannot implement the entire beam processing circuitry of the illustrated embodiment. For example, modalities may implement only DR processing (eg, DR 511) processing as described herein, or a combination of DR processing and IDR processing (eg, DR 511 processing and IDR 512 processing), if desired. The DR/IDR/XDR 214 beam synthesis processor may include a general purpose processor operable under the control of a defined instruction to provide operation as described in this document, a DSP, an application-specific integrated circuit (ASIC), an array of programmable port (PGA), etc. configured to provide the beam processing circuitry as described in this document. The operation of such a DR IDR/XDR beam synthesis processor is described more fully below with reference to the process in Figure 6.
[0077] It should be appreciated that synthesized beam signals according to embodiments of the invention are used in imaging, such as said ultrasound imaging. Therefore, the DR/IDR/XDR 214 beam synthesis processor output 214 of modalities is provided to the circuit for such imaging. For example, the synthesized dynamic resolution beam signals of the illustrated embodiment are provided for detecting and compressing circuit 59, such as removing the phase from the signal, and for providing mapping to the signal amplitude for sweep conversion. Modal Scan Converter 501 transforms the signal amplitude from the acquisition space to the display space for presentation to the user through the display 212.
[0078] One of the problems of implementing an apodized cosine beam is the combination of the signals from the transducer element (for example, in combiner 54 of Figure 5A). The cosine function oscillates between -1 and +1. Thus, when performing a weighting and a sum, a transducer element signal (channel) can be -1, while in another transducer element signal (channel) it can be +1, where there is a probability that one channel will cancel the other channel. The positive and negative values in each channel associated with the use of the cosine function can cause cancellation in the delay and sum process in beamforming, resulting in limiting the dynamic range. Also, since the cosine function goes from -1 to +1 and therefore crosses zero, certain transducer elements will receive a very small signal. To overcome this problem, front end circuits of an image processing system (for example, a front end circuit A to D converter) may need to have a very wide dynamic range.
[0079] The above problems will be associated with the use of a cosine apodization are avoided in the embodiment of Figure 5B, in which a high apodized cosine beam (eg Hanning beam) is formed by beamformer 213. So instead From using the original beam to directly form an image processing apodized beam, the mode of Figure 5B operates to form a high cosine apodized beam (eg, a Hanning beam) in addition to a Sync beam for use in the synthesis of beam DR. Thereafter, a second sample or auxiliary beam signal used in the DR beam synthesis described above can be calculated by taking the difference between the signals of the first sample beam (here a Sync beam) and the high cosine apodized beam. Accordingly, in the embodiment of Figure 5B, the signals from the delayed transducer element are appropriately combined in combiner 55 to provide a Sync beam signal as per the above-mentioned first sample beam signal. Transducer element signals weighted in an increased cosine function are combined in combiner 54 to provide an increased cosine apodized beam signal. An advantage of forming such a high cosine apodized beam at the front end is that the combiner 54 only needs to handle positive signals, thus further suppressing noise.
[0080] In ultrasound image processing, dynamic focus is usually implemented in conjunction with a variable aperture. In other words, different aperture sizes are used to form beams at different depths. In general, it is preferable to increase the aperture size as the depth increases to maintain resolution at various depths in an image. The Sync beam and the apodized cosine beam can be formed using different sized apertures that vary with depth. Since the number of channels implemented in an original beam is generally limited, the beamforming aperture size stops growing at certain depths when all available beamforming channels are used. From this right depth, all received channels are used to form the beam with a constant aperture.
[0081] In generating an increased cosine beam signal, for example, the inputs to amplifiers 51-1 to 51-N of the mode illustrated in Figure 5B represent signals from transducer-specific transducer elements. For an original N-channel beam, the largest aperture comprises N transducer elements to form N-channel beams. When aperture varies with depth, certain calculations may only need to use a subset of the transducer elements (for example, an increased cosine function for various depths can be calculated for selected transducer elements or selected aperture). In a preferred embodiment, for each calculation of the augmented cosine function, the modality system looks for the best set of weights (eg, adjustments to one of the appropriate elements 51-1 to N 52 and 53-1 to 53-N) for the best reach the DR beam using two sample beams.
[0082] After the signals are combined by combiners 54 and 55 of Figure 5B, the resulting beam signals are combined together by combiner 57, providing the subtractive combination in the illustrated embodiment, to provide a second sample or auxiliary beam (here a cosine apodized beam) for use in DR beam synthesis, according to modalities. It should be appreciated from the above discussion that the Harming or augmented cosine beam, as initially generated by combiner 54, may be the beam resulting from DR beam synthesis processing in particular situations (eg if parameter α = 1 in modalities ). Thus, rather than regenerating an augmented cosine apodized beam of the first sample beam and second sample or auxiliary beam, embodiments can utilize the augmented cosine apodized beam originally generated by combiner 54. The output of combiner 54, therefore, is shown coupled to the DR/IDR/XDR 214 beam synthesis processor to provide the increased cosine apodized beam signal to complement the first (Sync beam) and second (Cosine apodized beam) sample beams.
[0083] The Sync beam signal and apodized cosine beam signal are provided to the DR/IDR/XDR 214 beam synthesis processor of the illustrated embodiment for dynamic resolution beam signal synthesis as described in this document. In this regard, the DR/IDR/XDR 214 beam synthesis processor of the embodiment of Fig. 5B can be configured as discussed with respect to Fig. 5A above.
[0084] As per the embodiment of Figure 5A discussed above, beam signal conditioning and/or processing may be provided in accordance with embodiments of the present invention before, in combination with or after DR beam synthesis processing, if wanted. For example, in the embodiment of Figure 5B, the DR/IDRXDR 214 beam synthesis processor operates in the RF domain (i.e., signals are combined as RF signals) and the synthesized dynamic resolution beam signal illustrated in the embodiment is provided to the quadrature band pass filter 56 for signal conditioning. Additional or alternative conditioned signal beam may include analog to digital conversion (eg where a digital signal processor (DSP) is used here in DR beam synthesis), amplification, noise cancellation, etc.
[0085] According to the embodiment of Fig. 5A, the DR beam signal synthesized by the DR-XDR processor 214 of the embodiment of Fig. 5B is provided to the imaging circuit. Specifically, the synthesized DR beam signal of the illustrated embodiment is provided for detecting and compressing circuit 59, such as removing the phase from the signal, and for providing mapping to the signal amplitude for sweep conversion. The scan converter 501 of the illustrated embodiment transforms the signal amplitude from the acquisition space to the display space for presentation to the user through the display 212.
[0086] Figure 6 shows detail of a dynamic resolution beam synthesis process modality, as can be provided by the DR/IDR/XDR 214 beam synthesis processor of Figures 5A and 5B, to achieve side lobe reduction of a scanning beam in accordance with the concepts in this document. In particular, in the embodiment illustrated in Figure 6, the processes shown above the upper dotted line provide DR beam synthesis corresponding to the DR 511 processing operation of Figure 5A, the processes shown between the upper and lower dotted lines provide corresponding IDR beam synthesis to the IDR 512 processing operation of Figure 5A and the processes shown below the lower dotted line provide XDR beam synthesis corresponding to the XDR 513 processing operation of Figure 5A.
[0087] In DR 511 processing operation of the DR/IDR/XDR 214 modal beam synthesis processor, the first sample beam signal and the second sample or auxiliary beam signal, preferably weighted using the α parameter, are combined to synthesize a DR beam signal. Therefore, in process 601, a first sample beam (e.g., a Sync beam) having main lobe 601-1 and side lobes 601-4 formed for each sample point in a digitized area (e.g., each focal direction) of an object to be searched (eg area of tissue) acquired. In addition, a second sample or auxiliary beam (eg, an apodized cosine beam) having main lobe 601-2 and side lobes 601-3 formed by each sample point in a digitized area of a volume being imaged is acquired. . In operation according to method 601 of an embodiment, the first Iu sample beam signal (including main lobe I uM signal component / side lobe I uS signal component) and second or auxiliary beam signal Ic are acquired using the aforementioned apodized Cosine and Sync beams for each sample.
[0088] The first sample beam signal Iu and the second or auxiliary beam signal Ic of the illustrated embodiment are input into process 62, which computes the parameter α for use in weighted combination of the sample beams. As discussed above, the α parameter is a sidelobe cancellation parameter in the modal DR beam synthesis process and is used in the synthesis of a DR beam of sample beams (eg, Sync and apodized cosine beams). In an alternative embodiment, the calculation of the α parameter can be omitted and thus the process flow can proceed directly to process 602 as shown by dashed line 610.
[0089] The following vector analysis is useful in understanding the calculation of the process parameter α 62 as may be used in accordance with embodiments of the invention. Said first sample beam signal ^Iu (eg Sync beam) can be decomposed into two components such that
The vector unit u uM → defines the focal direction of the main lobe, where
and the vector unit → uuS defines the focal direction of the side lobe, where
The above-mentioned second signal I c → of sample or auxiliary beam (eg apodized cosine beam) can be represented by
When the second or auxiliary sample beam (eg apodized cosine beam) is aligned with the side lobe of the first sample beam (eg Sinc beam), the vector unit of the second or auxiliary beam (eg cosine) apodized), → uc , will be aligned with the unit vector of the sidelobe component of the first opposite-phase sample beam (eg, Sinc beam). That is, → −= → uc uuS , where
Thus, the side lobe components of the first signal → u I together → uc signal sample beam is
Where

[0090] It should be appreciated that DR beam synthesizing processes in this document can be applied to all samples of an image to compute the parameter
for each sample located at different depths of each beam sweep. For example, ( ) un I ,zn → and ( ) cn I ,zn → are the signals acquired at depth nza from the first unprocessed No. sample beam (for example, a non-apodized Sync beam in the previous example) and the second sample or auxiliary beam (for example, an apodized cosine apodized beam in the previous example). Thus, ( ) ( ) ( ) DR nunncn I ,( zn ) I ,zn ,zn I ,zn → → → = +α . As discussed above, it is desirable that, according to embodiments of the invention, the value of the parameter α(n, zn) is delimited between 0 and 1 or 0 < α(n, zn) ≤ 1. For example, in one case when the unwanted direction clutter is very large at the sample site (n, zn), then α(n, zn) is defined as one of the DR beam synthesis process to maximize the amount of sidelobe suppression. In this example, 100% of the acquired signal from the second sample or auxiliary beam (eg apodized cosine beam) is summarized to the first signal of the sample beam (eg Sync beam) at this time. However, in doing so the main lobe ( ) un I ,zn → is diffused as a result of the summation process. That is, some main lobe diffusion occurs in (n, zn) samples when α(n, zn) ≠ 0. Thus, in the modal DR synthesis process, α(n, zn) dynamically changes from sample to sample depending on the clutter force near the sample location (n, zn) .
[0091] The case where α = 0 represents a situation that the disorder received from a Sync beam is relatively small that no cosine apodized beam signal is needed to suppress the side lobe from rejecting the disorder. In this case, the object being imaged is delineated by the main lobe of the Sync beam, whose width is distributed, according to the limited diffraction resolution.
[0092] In the case, where α = 1 represents another situation, where the disorder received from the Sync beam is so great that 100 percent of the signals received from the apodized cosSync beam are used to suppress the side lobes. This results in a Harming beam with a main lobe that is much more diffused than the limited resolution diffraction for object delimitation. Outlining an object being created with an image with different resolution can cause perceptual distortion of the object for image interpretation. Furthermore, in an extreme situation where the clutter is so strong that the side lobe of the Harming beam (when α = 1) is not sufficient to suppress (or roll out) the clutter, the sample is contaminated with the degrading clutter. the quality of the image.
[0093] Signal components assigned to the main lobe or side lobes of a beam can be segmented in the IDR and XDR process of embodiments of the invention. By manipulating the acquired signals from the DR beam and the cosine apodized beam, a corresponding category of signal components for beams of different shapes with different geometric properties can be produced. Desired signal components with very clear main lobe and few side lobes can be synthesized to match main lobe resolution and side lobe levels to improve image quality.
[0094] The α(n, zn) parameter indicates the amount of clutter, its strength and how it is distributed near a sample point and can be used to control the other beamforming parameters to sharpen the main lobe and attenuate the side lobe in the IDR and XDR process of embodiments of the invention. Parameter tables 63 of the illustrated embodiment include lookup tables for mapping the desired beamforming parameters using α. These processing parameters can be predetermined for a variety of depths and conditions, can be dynamically calculated based on various operating conditions and parameters, etc. In one embodiment, the processing parameters of parameter table 63 are set to match the depth and focal direction on an aperture-by-aperture basis for each scan beam signal.
[0095] From the above description, modalities DR beams are formed by combining the Sync beam signal with a percentage of the cosine apodized beam signal to reduce the sidelobe, where α can be determined according to the criterion of minimum force that results in
according to modalities. In other words, the modal beam DR → I DR signal is synthesized according to
In this regard, the method 602 of embodiments of the invention operates to form the DR beam → DR beam signal from a weighted sum of the Sync beam and apodized cosine beam signals. For example, a DR beam signal, I DR → , corresponding to a synthesized DR beam, Bo (θ), can be constituted by a sum of Sinc beam, Bu(θ), signal → u I and the weighted cosine beam. apodized, Α(θ), sign I c → (eg, Bo(θ) = Bu(θ) + αΑ(θ)) in process 602.
The synthesized DR beam, B0(θ), corresponding to the DR beam signal, IDR, formed in process 602 has main lobe 602-1 with reduced or minimized side lobes 602-3. Figures 6A to 6C illustrate the synthesis of a DR beam signal, IDR, corresponding to a synthesized DR radius, B0(θ), a sum of the Sync beam, Bu(θ), Iu signal and ^ the weighted beam of apodized cosine, A(θ), signal Ic (eg B0(θ) = Bu(θ) + αA(θ)), according to the above mentioned operation of process 602 using sample beams as provided by the beamformer 213. Specifically, Figure 6A shows the Sync beam signal Iu received from the Sync beam (first sample beam) and Figure 6B shows the cosine apodized beam signal Ic received from the cosine apodized beam (second sample or auxiliary beam) . Figure 6C shows a synthesized DR beam resulting from the sidelobe component being ^ removed from the Iu beam Sinc signal, in the case where α = 1.
[0097] As described above, one technique for synthesizing a ^ DR beam signal is to combine the Iu Sync beam signals and the ^ apodized cosine beam Ic signals (eg, I DR = lu + αIc, 0^ α ^ 1) . However, instead of forming an apodized cosine beam to synthesize the DR beam, modalities like the one in Figure 5B discussed above form an augmented cosine beam (eg, Harming beam) for use in synthesizing a DR beam. For example, operation of process 602 using sample beams as the original beam condition 214 of Figure 5B provides DR beam signal synthesis comprising the difference between the signals of an increased cosine beam and a beam Sinc I DR = Iu + α( 1 - Ic) 0 ^ a < 1. Such a modality can operate to form an apodized cosine beam and increased cosine beam and the sine beam thereby aligning the apodized cosine beam with side lobes of the Sync beam. The use of such a cosine apodized beam in DR beam synthesis substantially suppresses the side lobes of the Iu-beam Sync signal, preventing scattering of the main lobe of the Iu-beam Sync signal.
[0098] The DR beam signal synthesized in the 602 process, providing suppressed side lobes and minimized main lobe propagation, can be used by the ultrasound imaging system 200 for high quality imaging. However, embodiments of the invention provide additional dynamic resolution beam synthesis processing to further improve the characteristics of the synthesized beam. Therefore, processing in accordance with the illustrated embodiment proceeds to process 603 for further dynamic resolution beam synthesis.
[0099] In the IDR 512 processing operation of the DR/IDR/XDR 214 beam synthesis processor of modalities, certain geometric and morphological properties of different beams (for example, one or more of the sample beams and/or synthesized DR beam ) processing are used in the processing of dynamic resolution beams. In particular, the signals of a beam are decomposed into two components: one component corresponding to the main lobe and the other component corresponding to the side lobes. These component signals are then recombined (weighted sum) to create a new signal corresponding to a new sample beam (an IDR beam of embodiments of the present invention) with very narrow main lobe and very few side lobes.
[0100] Process 603 of the embodiment illustrated in Figure 6 provides processing of a synthesized DR beam signal and one or more sample beam signals (e.g., the second sample or auxiliary beam signal) to segment beam component . Signals from these beam components are then used to compose a new signal, as if it were received from a high-performance beam (an IDR beam). The signal decomposition and reconstruction process is operated at each sample point in each focal direction to optimize the execution and contrast resolution of the entire image, in accordance with embodiments of the invention.
[0101] Beam segmentation, manipulation and recombination by operating the 603 process to provide the synthesis of IDR beams, according to modalities is illustrated in Figure 6D to 6I. As discussed above, where parameter α > 0 the DR beam synthesis, according to modalities will result in main lobe diffusion in addition to side lobe suppression. IDR beam processing, as provided by process 603 and as illustrated in Figures 6D to 6I (for α = 1) operates to prevent such main lobe propagation by segmenting the main lobe of the first sample beam (not diffused from combination with second beam sample or auxiliary) using the synthesized DR beam. To segment the main lobe of the first sample beam, the modalities process 603 calculates the minimum between the DR beam (IIII DR uhu = + − α ( ) rrrr ) and the second I c → or auxiliary beam, ( ) ( ) DR DR c MIII rrrr = ϕ MIN , , where φ provides phase alignment, to give a main lobe diffusion component, as shown in Figure 6D. This main lobe diffusion component ( → M ) essentially comprises the part of the synthesized DR beam that is not the main beam of the first sample beam ( I u → ). In this regard, the main lobe diffusion component can be subtracted from the DR beam to provide a first sample beam of the main lobe component, IuM IDR M r r r = − , as shown in Figure 6E. It should be appreciated that the first sample beam of the main lobe component ( I uM → ) of Figure 6E provides a narrower main lobe than that of a DR beam ( I DR → ) synthesized through the above described combination of beams. sample and therefore can be used in providing high quality imaging.
[0102] The exemplary embodiment depicted in Figures 6D and 6E efficiently split the signal of the first sample beam (eg, Sync Iu beam) into two disorder received by the side lobe of the first sample beam in a neighborhood close to the magnitude point of the component main lobe signal received in an insonified area by the main lobe of the first sample beam at the sample point that is propagated, according to the main lobe width. The signal to the clutter ratio varies from point to point depending on the object being insonified. An image is often thus stained at different levels by disorders. While it seems plausible that a clear and pure image can be reconstructed by retaining only the main lobe signal component of the first sample beam and eliminating its side lobe component, this is not necessarily so. An area of the image where the amplitude of the signal from the side lobe is small relative to the amplitude of the main lobe signal has been found, removing the signal from the side lobe component can result in improved image quality; but for other areas, where side lobe signal amplitudes are large relative to main lobe signal amplitude, eliminating all side lobe signals in an image can generate a series of irregular “dark” areas that can cause problems of image interpretation. This is because the side lobe of a beam integrates echo signal received from an extended area close to the sample point. At a sample point, where the signal received from the main lobe is much lower than that from its side lobe, the signal from the disorder component will functionally interpolate the object shape which is useful for image interpretation.
[0103] In this regard, a signal derived from a new beam which is formed by the weighted sum of the main lobe component signal and a small amount of side lobe component signal are accordingly preferred for embodiments of the present invention. In the process 603 embodiments of the invention, the weighting for the main lobe signal and the side lobe signal are programmed and selected depending on the amplitude of the main lobe signal, the amplitude of the side lobe disorder signal, the side lobe signal for the main lobe signal ratio and/or the α DR parameter at each sample point to optimize image quality.
[0104] Additional Dynamic Resolution Processing in accordance with process 603 of modalities is represented by Figures 6F and 6I, in which a main lobe and a side lobe attenuation such as may be provided as a properly weighted side lobe component is added to the first segmented sample beam of the main lobe component to synthesize an IDR beam. The sidelobe component signal shown in Figure 6F is segmented from the signal of the first sample beam, e.g., the Sync beam. It is known that the side lobe level of the Sync beam is attenuated with angle (or distance) at a rate ~ 6 db/octave which is relatively slow compared to the DR beam when α > 0. Specifically, for the beam of Harming, (a DR beam when α = 1), the side lobe is rolling out of rotation at a rate ~18 db/octave, which is much faster than the Sync beam (DR beam when α = R 0). An IαS signal component can be extracted by taking the RR difference between the DR I beam signal and the I signal of the DR uM RRR main lobe segmented Sync beam or I = IDR -I M αS DR uM . R
[0105] Figure 6G shows signal IαS corresponding to a beam whose side lobes are geometrically distributed following the DR beam (for example, the Harming beam when α = 1) with small residual main lobe of the DR beam as a result of the subtraction process . As shown in Figure R 6H and 6I, the signal IαS can be attenuated by a parameter YR where Y - 1, then integrated with the signal from IuM to RR RR to create a new signal IαN= IuM + YlaS • The representation of an IαN signal corresponding to a beam (an IDR beam) whose lobe is geometrically distributed with angle (or distance) as shown in Figure 6I• The center of the main lobe of the IDR beam is as narrow as or narrower than the main R lobe of the Sync beam IuM • The low amplitude of the main lobe is then gradually propagated and mixed with the side lobe that is rolling out at a rate of the DR beam. Since y is chosen to be smaller than according to embodiments of the invention, the side lobe will be attenuated by 20 log Y db. For example, when r = 0.125, the side lobe is attenuated by 18 db. The Y parameter can be selected at each sample point adaptable to its α parameter beamforming, the amplitude of the component signal of different types or its aspect ratio for optimal image quality.
[0106] It should be appreciated that the previous example shows the main lobe R of a Sinc IuM beam that can be segmented from DR beam (when α = 1) in the IDR process. A main lobe narrower than the main lobe of the R Sinc IαM bundle can also be segmented from other DR RR bundles when 0 < α 1 <. For example, when α = 0 IDR = Iu . As in the IDR process, the signal corresponding to a narrow main lobe component beam can be segmented by computer IMIIIIIIIIII αM DR DR DR DR cuuuc = − = − = − φ φ ( ) MIN , MIN , ( ) ( ) ( ) A Figure 6I(1) shows the segmented component beam M Iα r which is narrower than the main lobe of the beam Sinc uM I r . Furthermore, a signal component S Iα r can be segmented by computing S DR MIII α α = − rrr that S Iα r is a signal component corresponding to the side lobe of the DR beam when α = 0, as shown in Figure 6I(2 ). A new IDR beam can be formed by computing N uM S I I I α α = + γ r r r . N Iα r is a signal corresponding to a new beam whose side lobe is attenuated by 18 db; however, the attenuation rate of the side lobe is the same as that of the DR beam (for α = 0) at 6db per octave. Figure 6I(3) shows the main lobe, the side lobe, the attenuation rate of the side lobe of the DR beam and of the IDR beam when α = 0 and α = 1 in logarithmic scale, respectively.
[0107] It should be appreciated that the signal corresponding to R the main lobe of the other DR beam, IαMwhen 0 <α < 1, can be similarly segmented, according to embodiments of the invention. The width of the main segmented lobe of the DR beam RR increases with α and IαM<IuM for 0 <a < 1 . The side lobe R of the segmented IRD beam IαN for 0 <α<1 is attenuated by 20 log Y db and the side lobe attenuation rate increases from 6 db per octave to 18 db per octave with α to 0 < α ^1.
[0108] It should be appreciated that the side lobe component of the synthesized DR beam is substantially suppressed, although some main lobe propagation is present. The main lobe of the DR beam is de-propagated and its side lobe attenuation rate is further enhanced, using a segmented component signal that is properly sized in the IDR process. The IDR processing parameter y is selected to compose a signal corresponding to a synthesized beam whose main lobe width is narrower or as narrow as the diffraction-limited beam. The magnitude of an IDR main lobe is gradually attenuated and mixed with the side lobe, whose level is determined by parameter y. The peak of the side lobe of the IDR beam is attenuated for the first time then continuously rolling-off at a rate after the side lobe of the DR beam, according to modalities. An IDR beam can be used to form an image with improved perceived image contrast and detailed image resolution.
[0109] The IDR beam signal synthesized in the 603 process, providing suppressed side lobes without main lobe propagation, can be used by the ultrasound imaging system 200 for high quality imaging. However, preferred embodiments of the invention provide additional dynamic resolution beam synthesis processing to further improve the characteristics of the synthesized beam. Therefore, processing in accordance with the illustrated embodiment proceeds to process 604 for further dynamic resolution beam synthesis.
[0110] In the XDR 513 processing operation of the modal DR/IDR/XDR 214 beam synthesis processor, the main lobe width of a synthesized beam (for example, the preceding IDR beam) is even more penetrating by a process beam DR (XDR) synthesis method of preferred embodiments of the present invention. The beam is progressively or iteratively formed through an XDR process for better beam control, in accordance with embodiments of the invention. A beam pointing function of an XDR beam synthesis process can shape the main lobe and side lobe of the processed beam to obtain a signal that is similar to a signal having been received from a beam with an extremely narrow main lobe and very little side lobes. For example, the main lobe resulting from the XDR beam synthesis of modalities has a width corresponding to the aperture of a transducer substantially larger than actually used in the example beamforming from which the XDR beam is synthesized.
[0111] Process 604 of the XDR beam synthesis process, illustrated in Figure 6 creates a 604-1 sharpening function for use in synthesizing an XDR beam signal having a sharp main lobe. Such a sharpening function is applied in process 605, preferably iteratively, a major lobe component (e.g., major lobe 605 - 1) to constrain the beam. As the IDR beam synthesis discussed above, a properly weighted side lobe component (eg, side lobe 605-3), is added to the main lobe component to synthesize an XDR beam (eg, XDR beam 605') having desired attenuation. The illustrated modality iterative control 606 works in collaboration with the 604 process sharpening function generation and the application of the 605 process sharpening function to iteratively sharpen the main lobe of a synthesized XDR beam. For example, in the illustrated embodiment, n is the number of iterations desired for XDR processing to achieve the resulting synthesized XDR beam signal, which is output in process 607. Each iteration of XDR beam processing shown in Figure 6 provides a new reinforced synthesized beam, represented by the XDR 605' beam of this iteration.
[0112] In the sharpness (narrowing) attributes of the main lobe of a beam provided for an XDR beam synthesis process of modalities (for example, the main lobe component of the first, non-apodized, sample beam, which also corresponds to the lobe modalities of a synthesized IDR beam) are manipulated to provide a beam shaping function. In understanding a modalities beam shaping function, it should be appreciated that the main lobe propagates in the example above, where a DR beam is synthesized by combining a first and second or auxiliary sample beam (eg, B0(θ ) = Bu(θ) + αA(θ)) results from the situation that the magnitude of the second or auxiliary sample beam in the angular range defined by the main lobe of the first sample beam is not nullified. As the percentage α of the second sample beam signal is added to the first sample beam for a signal reduction of the side lobe component of the first sample beam, the main lobe signal component of the first sample beam will also be summed. with the signal component of the second sample beam at the same percentage. For example, as depicted in Figure 3A, the double peak of the cosine apodized beam main lobe (the second or auxiliary beam in the illustrated modality) is composed of two geometrically displaced Sync beams, one is located to the left of the main lobe of the Sync beam. and the other is located to the right of the main lobe of the Sync bundle. The main lobe of a DR beam will intersect with the double peak of the main lobe of the cosine apodized beam in a focal direction ±θ-,where |θ| <θα. Where ±θα is the zero crossing the main lobe that defines the beam resolution, which amounts to 2θα, when the cancel factor side lobe DR beam is α. Since α is delimited between 0 and 1 in the DR beam of modalities, when α = 0, |θ0| = πe when α = 1, |θj = 2π . Thus, by summing the signal acquired from the apodized cosine beam with which the Sync beam will reduce the —— received clutter from the Sync beam Iu(n,zn) in the region of θ>θα. The main lobe of the Sync beam is also being propagated as a result of summing the beam signals in the region of -θα<θ<θα.
[0113] However, if the received signal from the cosine apodized beam is amplified by a factor of K, then the location of the intersection between the main cosine apodized beam DR. When K approaches zero, |θ| = θα. Whether the amplitude of the segmented main lobe signal of the DR beam is to compare with the amplified signal of the apodized beam of ± θDmé the origin. Note that 2| θD^is the main lobe diffusion and the smallest value of |θDm| the better the resolution. For example, the augmented cosine or Harming beam (for example, a synthesized DR beam where the first sample beam is a Sync beam, the second sample or auxiliary beam is an apodized cosine beam, and the parameter α = l) is the Sync beam combined with the cosine apodized beam. Therefore, by subtracting a component signal from the Harming beam, which is calculated by taking the minimum, the gain generated (eg K > 1) the apodized cosine beam and the Harming beam produce a sharp main lobe beam. The process is effectively creating a beam definition function to sharpen the main lobe of the Harming beam. As the main lobe of the Hanning beam is sharpened the structure of the Hanning beam side lobe is modified resulting in a new beam with a very narrow main lobe and very little side lobe, improving the detailed resolution and contrast resolution of the image.
[0114] Figures 6J to 6L illustrate XDR beam synthesis using a modalities beam shaping function. In providing a modalities beam shaping function, the main lobe component of a beam for which XDR beam synthesis processing is to be provided (eg a first sample beam, a synthesized DR beam, an IDR beam or a synthesized XDR beam from previous iteration) in splitting into two components (e.g., a narrow main lobe component and a residual main lobe component) by operating process 604 as illustrated in Figure 6J. For example, IuM is divided into I uM_n ^ (narrow main lobe component) and I uM _S (residual main lobe component) components using a beam shaping function such as beam shaping function ψ(θ) of Figure 6 K, where IuM n IDR (IDR ) {IDR Ic } rrrrr _ = −ϕ MIN ,κ and III uM S n uM uM n _ _ _ → → → = − . An XDR beam can be synthesized in process 605 by weighted summing the component signals as illustrated in Figure 6L. For example, an XDR beam, I XDR → , can be formed by combining a weighted narrow main lobe component (μ) ( I uM _ n → ), a weighted residual main lobe component (ρ) ( I uM _ S → ) and a sidelobe component ( IS → ) weighted (γ), where the weighting factors (μ, ρ and γ) can be selected on the basis of which.
[0115] As the DR beam peak is aligned with the cosine apodized beam null, the beam peak will not be changed by the process of IuM n IDR (IDR ) {IDR Ic } r r r r _ = −ϕ MIN ,κ .
[0116] Therefore, let the peak of the signal uM n _ I r be theoretically equal to the peak of the signal DR I r ; or max max ( I I uM n DR _ ) = ( ) r r . In the implementation, numerical error in the apodization process can cause minute misalignment of the first sample beam and the second sample beam which can result in a reduction in amplitude in the uM n _ I r beam process. A scaling factor μ is introduced for gain equalization such that, μ max max ( I I uM n DR _ ) = ( ) r r . In the first iteration, the signal uM I r corresponding to the main lobe of the first sample beam (the Sinc beam) is decomposed into two components uM _1 I r and I uM S _ _1 → . Since uM _1 I r , is a signal of a narrower beam than uM I r is aligned with uM I re I uM S _ _1 → , it is a signal component located outside the center of the beam for uM _1 I r , a new main lobe N uM _ _1 I r can be formed by combining the signals uM _1 I re I uM S _ _1 → ; or _ _1 _ _1 _1 uM S N uM uM I I I ρ → = + r r , where ρ ≤ 1. When ρ = 1, N uM uM _ _1 I I = r r , the main lobe of the DR beam is unchanged. When ρ < 1 new main lobe N uM _ _1 I r is formed that the center of the lobe is narrow, in which as the output of the lobe is formed by the attenuated component signal of ρ I uM S _ _1 → . Since the new main lobe N uM _ _1 I r is created from components uM _1 I re ρ I uM S _ _1 → which is decomposed from I uM → , the lobes N uM _ _1 I re I uM → , propagate in the same angular range. The signal beam N uM _ _1 I r contiguously connected to the side lobe of the beam I αS → DR.
[0117] From the above discussed it can be appreciated that one way to form XDR beam by calculating R R ^ ^ IXDR_1 = µ1IuM_1 +p 1 I uM _ S _i +Y11 a _ S . The XDR process can be iterated by feeding the XDR beam formed in the processor for n times until a main lobe is satisfactorily generated in the RR ^ ^ n-reiterate XDR beam IXDR _ n = μnIuM_ n +PnIuM _ S _ n + Y>I a _ S The scale parameters μn's in each iteration can be defined as one by normalizing the parameters pn without loss of generality. Yn's parameters can be defined differently in each iteration; however, Yn's can also be defined equally to simplify the calculation in all iterations. When the main lobe of the XDR beam is split at each iteration, the signal amplitude at the output of the new main lobe is attenuated, according to the parameter pi to set the output level at 20 logpi db below the new main lobe.
[0118] Figures 6L(1) to 6L(4) demonstrate how an XDR beam is formed in an iteration of the XDR process provided by processes 604 and 605, according to an embodiment of the invention. Parameters used for the processing example are defined as follows: R a = 1;K = 2;μ = 1;p = ±0.125; and Y = 0.015625 The signal IuM corresponding to the main lobe of the first Sync) is segmented in the IDR process as shown in Figure 6L(1). By increasing the gain of the second sample beam R (an apodized cosine beam) by setting K = 2, the signal IuM RR is decomposed into two components: IuM _1 and IuM_S_1 where RR R IuM = IuM _1 +IuM_S_1 . These two signal components are then R combined into IN_uM_1 , a signal corresponding to a new main lobe, which is composed with the narrow main lobe R constructed by the IuM beam _1 and an attenuated output of the corresponding R lobes IM S1. The lobe attenuation coefficient p is set to 0.125 which implies the new main lobe transiently attenuated by 18 db downwards where the output is getting mixed with the side lobe. p can also be set to the negative value to force the main lobe across zero, as shown in Figure 6L(2). It was found that the first negative side lobe enlarges the edge of the object resulting in improved tissue differentiation for some imaging application. The R side lobe of the IXDR_1 beam is mixed with the segmented R side lobe of the IαS DR beam which is attenuated by the factor Y = 0.015625, or by 36 db. The XDR beam, the first sample R beam (either a Sinc beam or a DR beam for α = 0, IDR,α=0) and the R beam DR I DR,α=1 for α = 1 are superimposed in Figure 6L(3 ). Figure 6L(4) plots the XDR beam in logarithmic scale. As shown the main lobe of the XDR beam is much narrower than the Sync beam and the side lobe level is substantially smaller than the DR beam which is attenuated by 18 db/octave in the example. In the operation of processes 604 and 605 it can be repeated to progressively constrain the main lobe of the synthesized XDR beam.
[0119] As with the IDR beam synthesized above, the segmented main lobe component by operating the above XDR process provides a narrow beam. However, embodiments of the invention operate to combine main lobe and residual and weighted side lobe components (e.g., 0 < p < 1 and 0 < y < 1) provide the desired level of attenuation and side lobe with the synthesized XDR beam.
[0120] It should be appreciated that new component signals with different beam properties can also be generated by arithmetically combining signals from different components that are segmented based on the principles described here. For example, the segmented component signal M as shown in Figure 6D can be combined with a signal component p that is created according to P = y(IDR,a=0) min (|IDR,α=0|,| IDR,a=J) = to obtain a new component of the RR RR R signal IuMM where IuMM =M +P . IuMM is a corresponding signal component for a main lobe to propagate less than Hanning's main lobe, but more than those of RR other segmented main lobes like IuM , IαM for all α's and those main lobe signals of any RR beam IXDR , IXDR_M . This process is graphically depicted in Figures 15A-15C. Three R RR signal components IuMM , IuM ,IXDR_M acquired from a segmented main lobe of R RR different beam widths, where IuMM>IuM>IXDR_M , are superimposed in Figure 15D. Taking the difference between the RR R signals from IuMM and IuM to obtain an IS_MM signal, which represents the signal acquired from a sidelobe component beam as shown in Figure 15E. Likewise, R an IS_M signal can be segmented by taking the difference between RR the signals IuM and IXDR_M , which represents a signal acquired from a sidelobe beam component as shown in R Fig. 15E. The side lobe component signals IS_M , RR IS_MM can be scaled and combined with IXDR_M to obtain a new signal which is equivalent to what is acquired from a formed main lobe. For example, the beam corresponding RR R R to the signal ICM = IXDR_M +0.25IS_M + 0.125IS _ Me shown in Figure 15G. R The main lobe formed ICM can be combined with other side lobe component signals with desired attenuation to obtain a desired beam signal.
[0121] DR, IDR and XDR signal segmentation techniques of embodiments of the present invention are based on synthesis and decomposition of the beam components according to the narrowband geometric and morphological properties between the Sinc beam, the apodized cosine beam , the Harming beam and other beams. However, it can be shown that the concepts here are similarly effective when a wideband beam signal is formed and processed accordingly for general imaging application. Figures 7A to 7C show exemplary plots of location-temporal profiles of sample beams and a synthesized XDR beam, in accordance with the concepts described above to illustrate the results of beam synthesis of the present invention. An array of 32 transducer elements are excited by Gaussian pulses centered at 3.5 MHz with 2 MHz bandwidth. Applying the proper time delay and different weights to the signals received by each element to concentrate a spot at 60mm, the spot is spread out differently depending on the beam properties. Sample beam 71 of Figure 7A comprises a first non-apodized sample beam (eg a Sync beam), a second sample or auxiliary beam 72 of Figure 7B comprises an apodized beam (eg Hanning beam or apodized beam cosine) and XDR beam 73 is synthesized using the first sample beam and the second sample or auxiliary beam, in accordance with the concepts of this invention. Figure 7C shows that the resulting main lobe of the XDR beam 73 is narrower than the main lobe of the sample beam 71 of Figure 7A with little or no side lobes. Likewise, the main lobe of the XDR beam 73 of Figure 7C is narrower than the main lobe of the sample beam 72 of Figure 7B (apodized beam).
[0122] Figure 8 also illustrates an example of the concepts of the invention applied to a three-dimensional processing. The 800 graph shows 801 Sinc beam, 802 Harming beam, and 803 synthesized beam produced by the concepts taught here. Specifically, graph 800 is a Fourier spectrum showing the spectral components of a signal consisting of ten sinusoids a0 to a9 to propagate from normalized frequencies from -0.35 to 0.25. The dynamic range of these signals is 140dB with the a3 signal at 0dB and the a7 signal at minus 140dB. Evenly distributed noise of at least 133 dB is added to the test signal and below this noise level. As can be seen, if the Fourier transform is taken over the test signal without using a window function, only the strong spectral components al, a2, a3, a4 and a5 are resolved. The other signals a6, a7, a8, a9 and aO are corrupted by side lobes made up of these strong components. The spectral peak of each spectral component represents the main lobe of a Sync function whose side lobe is attenuating at a rate of 6dB per octave. The side lobes of the strong components overload the frequency and do not allow detection of aO, a9, a8, a6 and a7. When the signal is apodized by Hanning, the overall sidelobe level is lower than the attenuation at a faster rate or 18 dB per octave. As a result, the additional sign of a6 is resolved. However, as shown by the Hanning 802 beam, the main beam is scattered and the spectral components a7, a8, a9 and a0 are still unresolved.
[0123] The Fourier apodized cosine spectrum can be obtained by replacing each spectral component by the average of its two nearest adjacent spectral components. Using a non-apodized component and an apodized cosine component, the DR/IDR/XDR spectrum can be calculated. The disorder cancellation parameter α is calculated for each spectral component of the Fourier spectrum. The side lobe of each spectral component is then suppressed from the DR process, followed by setting μ = 1, Y = 1, p = 1, and K = 2 in the modalities XDR process. As shown by the synthesized beam 803, all spectral components are resolved, including the components whose levels are incorporated into noise: a7, a8, and a0.
[0124] Figure 9 shows Sinc beam 905, Harming beam 906, DR beam 901, XDRl beam 902, XDR2 beam 903 and XDR3 beam 904 processed using different sets of parameters. The Sinc 905 beam is not apodized, and the Harming 906 beam is apodized. The DR 901 beam results by using only DR processing, as discussed above. Using the XDR process discussed here, the XDR1 bundle 902, the XDR2 bundle 903 and the XDR3 bundle 904 can be produced.
[0125] Figure 10 shows the Sinc beam 1001, Hanning beam 1002 and the cosine apodized beam 1003. Note that the cosine apodized beam is used as a steering beam to control the power level. The apodized cosine beam is used to move the gain up and down in order to detect where the system should cut the Sync beam. The minimum of the Sync beam and the cosine apodized beam will determine where the main beam crosses the zero axes.
[0126] From the above it can be appreciated that the XDR beam synthesis process operation narrows the main lobe of an ultrasound beam and/or the side lobes are further reduced, such as by applying linear and non-linear signal processing, in which the DR signal beam is decomposed into different component signals. These component signals then can be used to synthesize a new beam signal (an XDR beam signal) that corresponds to a virtual beam, of which the main lobe is narrow and the side lobe is shortened. Alternatively, modalities XDR beams can be synthesized by essentially not forming the aforementioned DR beam, but rather directly processing the XDR process of Figure 6, such as holding α at a constant (eg 1 or 0, 5).
[0127] It should be appreciated that the above DR/IDR/XDR beam synthesis techniques can be applied in a number of different imaging techniques. For example, DR/IDR/XDR beam synthesis techniques with respect to linear scan conversion, spatial composition, etc. can be applied. For multi-beam spatial composition, the detected signals from spatially shifted beams can be integrated to reduce coherent interference. To improve resolution, a non-apodized beam and a Hanning beam can be formed simultaneously to obtain a DR/IDR/XDR signal from each gaze direction before the compositing process takes place.
[0128] Although modalities have been described above with reference to arrays of a dimensional transducer, it should be appreciated that the concepts of the present invention are applicable to multidimensional transducer arrays. For example, the DR/IDR/XDR beam synth concept can be applied directly to two-dimensional (2D) beamforming.
[0129] Having described providing DR, IDR, and XDR beam synthesis according to embodiments of the invention above, details of various DR, IDR, and XDR beam synthesis functions and implementations will be provided below. It should be appreciated that the functions and implementations defined below can be used in the systems and methods described above to provide DR, IDR and/or XDR beam synthesis, in accordance with embodiments of the invention.
[0130] Bundle Decomposition and DR/IDR/XDR Bundle Synthesis
[0131] In operation, according to embodiments of the invention, the signal acquired from a DR beam at a specific location can be computed, minimizing the strength of the beam formed in each focal direction. Since the strength of a beam changes at each beam position, the main lobe width and side lobe level of a DR beam is optimized according to energy minimization criteria in accordance with embodiments of the invention. Based on the morphological and geometric properties of the DR beam, the first and second sample beam, signals corresponding to different main lobe and side lobe beam components can be segmented. These component bundles are further decomposed and new bundles with desired properties are then synthesized by arithmetically manipulating these bundle components. The signal corresponding to each new beam is calculated, according to the decomposition of DR, IDR and XDR and synthesis of the method of the invention. Processes of constructing the signal corresponding to a synthesized beam with desired properties using the split beam components are implemented, according to embodiments of the invention in process 601, 602, 603, 604 and 605 of Figure 6. These processes are graphically depicted in great detail using signals in combination of the first sample beam, the second sample beam, the non-apodized beam (α = 0), the Hanning apodized beam (α = 1), the DR beam of other α (0 < α < l) as shown in figures 3A, 6A-6L(4) and 15A-15G.
[0132] The beam decomposition and synthesis processes of modalities of the invention can be implemented in software and/or hardware configurations. Such beam decomposition and synthesis processes can be implemented either before QBP (past quadrature band) filtering or post QBP filtering as shown in Figures 5A and 5B. Methods based on Figure 5B are preferred, since the process is more robust in the presence of noise, after the signals acquired from the first and second beam are filtered by the QBP filter.
[0133] The beam decomposition, as described in this document, can be used in dynamic resolution beam synthesis, according to embodiments of the invention. A further, more detailed example of sample beam decomposition and synthesis in embodiments of the invention, let Iu and Ic be two acquired sample signals (eg, echo from the O(Φ) scatterer distribution) received using Sinc Bu beam and apodized cosine beam Bc which are angularly propagated in Φ- Since the amplitude of the signals received from an integration of all unsound propagation echoes are weighted by the amplitude of each beam in all angular directions, these sample signals can be represented as Iu(z,θ) = jO(z,θ-p)Bu (z,p)dp and Ic (z,θ) = jO(z,θ-p)Bc (z,p)dtp; thus, the signal of a new beam Bα can be calculated by the sum of the signals Iu and Ic according to the following equation: ; whereI z O z B z B zd I z I z α ( , , , , , , θ θ ϕ ϕ α ϕ ϕ θ α θ ) = − + = + ( )( ucuc ( ) ( )) ( ) ( ) BBB α = +uc α .
[0134] As discussed above, the signals received from the apodized cosine beam can be combined with the signal received from the Sync beam and obtain a new signal. This new signal is effectively received from a new reduced side lobe level beam by enlarging its main lobe. For example, let Iα = Iu +αIc . With respect to signal Iα , the geometric and morphological properties of its corresponding beam Bα vary according to the parameter α. Generally, the main lobe is monotonically widened with the parameter when the side lobe level is monotonically reduced and the monotonic side lobe attenuation rate is increased when it is greater than or equal to zero and less than or equal to one, 0 <a <1 .
[0135] The beam properties for values other than α (0, 0.25, 0.5, 1) are depicted using Figures 16A and 16B. When → → → → = = = u + c I I I I 1 α ,1 α ; where → 1 I , is the Hanning beam (apodized beam of increased cosine). When 0 0, u I I I α α → → → = = = ; where 0 I → is the Sync beam. In Hanning's bundle, the first side lobe is at -18 db lesser attenuation than the first side lobe of the Sync bundle. Hanning's side lobe attenuates at a faster rate at 18 db/octave versus Sync's side lobe which is attenuating at a rate of 6 db/octave. However, the main lobe of the Hanning beam would be 50% wider than the Sync beam.
[0136] It should be appreciated that the Sync beam and the apodized cosine beam oscillate in opposite phases when θ > ± π as shown in Figure 16C. Thus, in the process of Bα = Bu +αBc at angular locations greater than ± π, the magnitude cancellation of the side lobes of the Sinc beam occurs at all angular positions at > ± π. However, at angular locations ±π <θ< ±2π where the first side lobe of the Sinc beam is located, the side lobe cancellation process results in the displacement of the zero crossing point and propagating the main lobe of the Bα beam.
[0137] Also shown in Figure 16C, the first zero crossing of the Sinc beam that is located at ±π, thus ( ) ± = 0 → Iu π . When a beam Bα is formed according to BBB α = +uc α to obtain the signal Iα v , since there is no contribution of the beam Sinc at the ± π location to the formation of the beam Bα, the magnitude of the beam Iα r in ± π will be equal to the amplitude of the cosine apodized beam that is scaled by α, or α ( ) ( ) ±π =α ± π → → c II . In the beam pointing direction, the gain of the Bα beam is maximized assuming that the cosine apodized beam gain is minimized, or ( ) max BB 0 α α = , Bc (0 0 ) = for any α. The gain of the beam Bα is always greater than the gain of αBc at the angular location θ < ± π for any α. When 0
where Mn_α is the received signal of the minimum beam that is formed, having the absolute minimum gain at all angles θ between two beams Bα and Bc ; θα is the angle where beams Bc and Bα are intercepted and θα 2 π.
[0138] C0, C0.25, C0.5, C1, shown in Figure 16C are points of intersection between beams Bc and Bα ; Z0, Z0.25, Z0.5, Z1, are zero crossing points of beams Bα‘s for α = 0, a = 0.25, α = 0.5 and α= 1, respectively. Note that as α increases from zero to one, the zero crossing progressively moves from ±π to ±2π. The main lobe of the Bα bundle is propagating as the α parameter increases, while the side lobe level decreases.
[0139] Defining the phase p(Mn α) of the signal MRn α to the same — ^ (— ^ according to the phase of the signal received from the beam Bα or^| Mn α I = ^| Iα I , then,
where      → ϕ α I is the phase of the signal → α I .
[0140] Since beams Bα and Bc are intersection at θα, then BB α α α (θ θ ) = c ( ) • Also, in the beam pointing direction, ( ) max BB 0 α α = and Bc (0 0 ) = . When M n _α → is subtracted from → a I to obtain a new signal mn _ _ Iα α r or
to 0 1
[0141] m n _ _ Iα α r one is a signal whose amplitude is maximized at θ = 0; the magnitude of m n _ _ Iα α r spreads from its peak symmetrically towards zero at ± θα. The operation of _ _ _ n m n I I M α α α → → = + r implies that signal Iα → is decomposed into two components: m n _ _ Iα α r and M n _α → . The component signal m n _ _ Iα α r represents a signal corresponding to a component beam Ψα α m n _ _ , which is bound in a region of − ≤ ≤ θ θ θ α α . The signal peak m n _ _ Iα α r is aligned with the peak Iα → . The signal component M n _α → is a signal residue of Iα → , which corresponds to a bundle of component Ψα α sn _ _ that maintains the side lobe structure of the bundle Bα of the regions of θ θ < − α and θ θ > α .
[0142] The main lobe of the Sync beam is angularly delimited in the region of − ≤ ≤ π θ π . Since, θ π α ≤ , the beamwidth of the beam component Ψα α m n _ _ (signal m n _ _ Iα α r ) is narrower than the beam Sync. Furthermore, Ψ = αm n u _ _ 0 (0 0 ) B ( ) , the maximum gain of the beam Ψαm n _ _ 0 and its pointing direction are also unchanged
[0143] The main lobe of the Sinc BuM beam and the beam Ψ = α α α m n m n _ _ 0 _ _0 = are superimposed in Figure 16D. A new beam component Ψαs n _ _ 0 can be decomposed from the main beam lobe Sync beam Bum according to Ψ = − Ψ α α sn um _ _ 0 _ _ 0 B • Ψαs n _ _ 0 is a residue of main lobe beam consisting of two lobes whose peak is aligned with the null values of the beam component Ψαm n _ _ 0 . By minimizing the amplitude or power of the signal received by the component beam Ψαm n _ _ 0 , the resolution would be asymptotically approximated to the beam .
[0144] It should be appreciated that the main lobe of the Sync beam can be segmented, according to the following process. Figure 16E shows that the Bu and Bc beams are added to form the Bα =1 beam, the Harming beam. Since ( ) 0 Bu π = and 1 ( ) ( ) 0 B B α= π π = = c . Thus, a beam M n _1 B can be created, taking the minimum between the amplitudes of the beams Bα =1 and bc . By assigning the phase of the beam M n _1 B to the same as the phase of the beam Bα =1 , the magnitude of the beam M n _1 B will be the same as that of the bc when θ ≤ π. In the region of θ > π, the magnitude of M n _1 B will be the same as that of the beam Bα =1 . Thus, the main lobe of the Sinc Bum bundle can then be segmented by _1 1 _ _1 n BBB a M mn = − Ψ α α = and the side lobe of the Sinc Bum bundle can be segmented by removing the main Bum lobe from the bundle Sinc Bu by BBBB us u umn = − = − Ψα _ _1.
[0145] The signals from these beams are actually calculated according to the following process. Setting the α parameter to one: α = 1, then 1 . uc III → → → = + Since, ( ) 0 u I π → ± = , cuc III → → → = + for θ π = . Thus,

[0146] The phase of Mn _1 is defined to be the same as the vector 1 I → , leaving _1 1 ( ) _1 n M I M = ϕ n uur r . A null value will be set to θ = ± π when the signal amount of the beam M n _1 uur is removed from the signal of 1 I → , in the process of subtraction of _1 1 I M n . → − uur . Since the width of the main lobe of the Sync beam is defined by the angular region between -π and + π, the main lobe of the Sync beam is then segmented: I I M uM n = −1 _1 r r uur .
[0147] The side lobes of the Sinc beam, therefore, can be obtained by IuS = Iu-IuM ; and the side lobes of Iα can be obtained by IαS = Iα-IuM . Since the DR1 signal of the signal is the signal received from different beams at different sample locations with minimal clutter strength using different α, or I DR_i = Iα. Given IαS and IuM, a DR beam of embodiments of the invention can be synthesized by summing the main lobe IuM with different amounts of I as such that IDR = IuM + Yα; where Y<1 .
[0148] The result shows that the beamwidth of the synthesized DR beam associated with the DR beam signal IDR is the same as the diffraction limited beam Sinc whereas the sidelobe of the synthesized DR beam associated with the DR beam signal YIαSé smaller than the Sync beam and the side lobe of the minimum strength of the Iα beam for all signals in an image.
[0149] The DR beam I DR signal comprises two signal components, a side lobe signal component IαS or reduced side lobe YlαS and a signal component into component signals that include at least one component corresponding to a new main lobe whose beamwidth is much narrower than other components decomposed of residue signals into new side lobes which are split from the main lobe by ^ IuM. Desired direction beams from a main lobe where ^ the IuM signal is received. In the same direction, virtually no signal can be received from Ic due to the null location in the cosine apodized beam. In other words, ^ essentially, no sign is present at I c in the desired direction (eg, gaze direction). ^
[0150] When an amplification factor K is applied to Ic, only the signal from the unwanted location is amplified, with the signal from a beam whose main lobe is actually narrower when k is high. This property is shown in Figure 11.
[0151] Letting the main segmented lobe be BuM (θ) and the signal received by BUM (θ) be IUM = jBUM (θ)O{θ)dθ = j BUM (θ)θ(θ)dθ . IuM represents the signal received when the object is summed weighted, according to the weight distribution of BuM (θ) from θ = -π to θ = π ; where BUM (θ <-π) = 0, BUM (θ >-π) = 0 . In the beam focal direction corresponding to the IuM signal, bm is the maximum gain of the beam BuM(θ) considering that, in the same focal direction, the —> apodized beam signal of cosine Ic(0)= 0 A
[0152] Amplification of the acquired signal from the cosine apodized beam with an amplification factor κ, effectively is equivalent to applying a gain of κ to the cosine apodized beam. If the received signal from the apodized cosine beam is subtracted from that of the Sync beam it results in a new beam having the main lobe in the form of a beam shaping function. This beam shaping function is a κ gain function. A beam shaping function not only shapes the main lobe, but it also modifies the side lobe structure, simultaneously reducing its level. Since the cosine apodized beam will intersect with the Sinc beam at θ ±= θ m , at the point of intersection ( ) ( ) BuM θ m = Bc θ m . From the above, a signal component M _ mn → , extracted by calculating the minimum value between the magnitude of I DR → and I c → κ has the following properties:
where      → ϕ I αS is the phase of the signal I αS → .
[0153] Thus, the component signals M _ mn → and M _ Sn → vary their property depending on how the apodized cosine beam is interacted with the main lobe and the side lobe of the DR beam and the morphology of these component beams , the K-beam amplification factor.
[0154] Assume the case that κ is chosen large enough such that M Sn ϕ I αS I αS → → →       _ = . If the signal M n → is subtracted from I DR → , all signals received from the side lobes I αS → will be removed. Furthermore, as a result of the subtraction process, a new null is created ±θ m where the beams I uM → and I c → κ are intersected ( ( ) ( ) BuM θ m = Bc θ m , as shown in Figure 11) . This is effectively equivalent to splitting the main lobe beam signal DR I uM → (in the region - π≥ θ ≥π, where the main beam lobe is limited) into two new signal components; one is from a newly formed narrowed main lobe, I uM _ m → , which is delimited by θ −m < θ < θ m e ; the other I uM _ s → is from a newly formed two side lobes that are in the region of π ≥ θ >θ m and −π ≤ θ −< θ m .
[0155] Constructing an image using signals acquired from a narrower main lobe beam improves image quality. However, completely eliminating the segmented side lobe component signal in a subtraction process can introduce a hole in an image that degrades the image quality. For better control, the amount of component signal being subtracted from the DR beam is introduced parameter n<1, according to the modalities, where nMn represents a fraction of the signal that |MB| removed from the DR beam to synthesize a desired high quality beam.
[0156] As an amount of signal nMn is subtracted from the signal received from the DR beam IuM , the new signal is effectively equivalent to being received from a beam having the main lobe in the form of a beam shaping function. The main lobe of this processed bundle is shaped to result in a narrower main lobe and the side lobe is reduced by this function. For example,

[0157] Note that above reveals the main lobe IuM being modeled by a modeling function ys(θ), resulting in a new main lobe RM m in the region θ<θm. This new main lobe can be represented as

[0158] Since the main lobe gain of the beam Sinc BuM (θ ) bM is not zero, when θ θ
This shows that the main beam is shaped according to the relationship between the cosine apodized beam gain and that the beam Sinc of the beam in the region defining the beam intersection point θm and |θ| <θm. The morphology of the shaped beam will depend on parameters n and K.
[0159] The foregoing shows the main lobe of the DR beam is modified by a y(θ) beam shaping function (illustrated graphically in Figure 12) when θ<θm. The modalities y(θ) beam shaping function has the following properties: 1. y(0) = 1 since Bc (0) = 0 ; in other words, in the desired focal direction, the beam gain is maximized and not changed in signal processing. 2. When n and K are both zero, the bundle morphology is the same as the DR bundle and y(θ)=1 for all θ. 3. Since Bc(θ) is smaller than BuM(θ) in the main lobe region, then y(θ)< 1 when |θ| <θm. Thus, the beam BuM_m(θ) is always narrower than the beam BuM(θ) 4. Since both Bc(θ) and BuM(θ) are symmetrical in the focal direction of the beam, the beam shaping function is a function symmetrical.
[0160] The beam shaping function ys(θ') changes the beam gain in the regional < 0m|θ <θm. The quantity and morphology of the modeling beam will depend on the parameters n and k. When n and K are zeros. Since both B0{ θ) and BuM (θ) are symmetric under the focal direction of the beam, the beam shaping function ^(θ) is a symmetric function. Since |θm| <π, the beamwidth of BuM (θ) is always narrower than that of BuM (θ) . UUR UUR
[0161] The anterior component signals Mn_m and Mn_S vary depending on how the amplified cosine apodized beam interacts with the main lobe and the side lobe of the DR beam and the morphology of these component beams in K amplification factor. k amplification is small, the location of ±θme closer to ±π . Thus, the main lobe of the processed beam will be relatively less narrow than that of the processed beam with high amplification k. When the amplification factor k is small, the interaction between the apodized cosine beam and the side lobe of the DR beam is more complicated. The morphology of the processed beam side lobes will depend on the relative amplitude of the side lobes of the DR ZJ beam and the magnitude of the side lobe of the cosine apodized beam, after an amplification factor is applied r|Ic ., from the M component signal _ $ is preferably defined in phase with the DR beam and its magnitude represents the smallest RR UUR of the two signals l/al and r II. Therefore, when M __$ is subtracted from the DR beam, the sidelobe signal will always be smaller that results in lateral lobe suppression.
[0162] The subtraction process to segment the component signs suggests that the phase of both the minus and minus signs should be kept identical. For applications where only the signal amplitude is of image interest, it is equally effective in implementing single amplitude operations. In this case, it is desirable that the sign d ‘ >inal of both the minus sign and the minus sign is kept identical. In other words, substituting any implemented to process the beam signals formed after they are in quadrature-passband and decimated in this context, real(IRα) IRα and imag(IRα) is the image part of signal Iα. When doing so, the DR/XDR process operates on the real part and the image part of the passed band data separately. The processed signal components the real real part(IRX )and the Then the real part and the image part of the processed signal IX = real(Iα)+i*imag(Iα) . The IX-compressed signal is converted to scan into a resulting video image.
[0163] For 2D grayscale imaging applications only, however, the signal phase can be neglected in the DR/IDR/XDR process. In this case, only the magnitude of signals in the DR/IDR/XDR process is needed. Also, in the XDR process, instead of processing the magnitude of the signals, signal power can be used to reduce computation. Once a split and detection process is incorporated into the modalities DR process, the computational cost can be relatively high. For low-cost implementation, the DR process can be omitted, trading performance for cost or speed.
[0164] The algorithm can also be implemented before the signal is quadrature bandpass. Then the sign subtraction process, ϕ (IRF ) is replaced by the sign for effective component signal segmentation.
[0165] As described earlier, the signal received from the main lobe of the Sinc beam can be an I r segmented by processing signals c κ I re 1 I r when K = 1. Subsequently, an I r can be further divided by processing of the signals c κ I r and an I r by setting k > 1. When κ is set to a value less than 1, eg setting κ = 0.22225; one can also form a bundle with the main lobe size approximately equal to the Hanning bundle. This larger main lobe can be further divided using the process described above. A new beam can then be synthesized with different component signal.
[0166] Removing the preceding signals from the component signal obtained from the DR beam effectively creates a main lobe and reduces the side lobe of the processed beam. Figure 13A shows the main lobe being split using K = 2, setting p = 0.0625 to reduce the residual main lobe and setting y = 0.125 to reduce R the side lobe of the DR beam which is the side lobe of the I1 RR RR in this case. The resulting signal IX = μ In _ m +p In _ S + yIas and its corresponding beam are shown in Figure 13B. It is important to note that, because of the reduction in artifacts allowed by the narrowing of the main lobe and the attenuation of the side lobes, it would be advantageous over the object of interest, thus achieving a sharper display image than is currently possible for the sample.
[0167] It should be appreciated that the process of driving the minimum signal between the DR beam of the sample beam with an apodized cosine amplified beam amplifies different factors and sets the phase of the minimum signal to be in phase with the DR beam can be applied again to obtain a signal corresponding to a main lobe beam of desired narrow width and desired low side lobe level. That is, the XDR synthesis process of segmenting a signal into sample beam components and shaping the beam using different amplification factors k, sidelobe reduction parameter y and beam shaping parameter n can be repeatedly applied to processed beam to obtain a new processed beam with desired main lobe and side lobe properties. These properties can be defined, according to image parameters such as detailed resolution, contrast resolution and dynamic range in the imaging process. Beams after 10 iterations with different processing parameters are shown in Figure 14.
[0168] Side lobe level control can also be achieved by attenuating (eg multiplying by an attenuation factor less than one) the main lobe segmented residual side lobe if desired. For example, the gain and attenuation factor in the DR and XDR process can also be defined as a function of α to adapt to the sidelobe strength in each sample.
[0169] The analysis described above is based on geometric properties between the narrowband formulation of the Sinc beam, the apodized cosine beam, the Hanning beam and other beams. However, it can be proven and experimentally demonstrated that the concepts here are similarly effective when the broadband signal is a beam formed and processed accordingly for general imaging application. Furthermore, the concepts can be directly applied to spectral analysis, two-dimensional matrix beamforming, multiple-beam spatial composition, and parallel to multi-beam beamforming.
[0170] Note that it is possible to use variations of the application of DR/IDR/XDR techniques in this document to obtain different results. For example, vector format can be represented by real and image parts and DR, IDR and XDR can be processed into real and imaginary parts separately. To keep the phase unchanged, it is equivalent to keeping the real part signal or the image part signal unchanged. Single amplitude processing in the RF domain can be accomplished by keeping the signal signal unchanged, rather than keeping the phase unchanged.
[0171] Different sequences of applying gain and attenuation factors or representing gain or attenuation of math functions can be performed, if desired. Forming a beam to constant α (any α <1) followed by an XDR process to improve resolution and sidelobe suppression. Using two beams, a modality can apply min to segment the component beams or component signals and then combine component signals to synthesize new beams, using gain and attenuation factors to build a new beam.
[0172] Modalities can recursively form new beams with multiple gain and attenuation factors to arrive at a new high-performance beam. Thus, the concept applies to higher dimensional beam formation. For example: Let Kj be a fact ie amplification for the cosine apodized beam signal and 0<K — K ; j max Let μbe the processed main lobe enhancement factor; μj >1;; Let p be the processed side lobe attenuation factor; |pj - 1;;
Start Let I1 = I aDR; ; set the first processed signal of the processed beam to be I1 while j < n Calculate

Exemplary DR/IDR/XDR Beam Synthesis Algorithms
[0173] To help understand the concepts of the present invention described above, an exemplary DR/IDR/XDR beam synthesis algorithm as can be performed by the DR/IDR/XDR 214 beam synthesis processor of Figures 2A, 2B, 5 A and 5B is given below. It should be appreciated that the established algorithm is only one example of an algorithm that is operable to provide DR/IDR/XDR beam synthesis, in accordance with the concepts of the present invention. ^ Let Ic be the cosine apodized beam signal in the xth beam and the yth sample; ^ Let Iu be the Sync beam signal and the xth beam and the yth sample; ^ Extract signal Ia from the sample by computing the sample
if α > 1 adjust α = 1, α < 0, adjust α = 0, Then calculate lIα = lIu+αlIc; If IDR beam synthesis is desired, then it starts the IDR process as follows:
Segment into component signals lll ll IαM = Iα-Mn;IαS = Iα-IαM =Mn; ll Composing the signals IαM and IαS into a new signal (synthesized IDR beam signal); I aDR = I aM + YS I aS', If XDR beam synthesis is desired, then it starts the XDR process as follows:
A new side lobe component III is formed α α α ns MM _ _1; → → → = − , Form the beam XDR I XDR = I aM _1 + p I an _ s +YI as To form an XDR beam using an iterative method according to embodiments of the invention: Method 1 Let kj be a factor of amplification for the apodized beam signal of cosine Ic and 0 < K - K^ j max Let μ be the processed main lobe enhancement factor Let ρ j be the processed side lobe attenuation factor;
Start Set the first processed signal of the processed beam to — — be I1 and save the IαM component of the main lobe — component in the Ir buffer. — — — — Let I1 = IαDR and Ir = IαM Let the XDR beam comprise only the side lobe component; while j < n Calculate
Final I XDR = I XDR + μ* I αm_n ; Method 2 Let Kj be an amplification factor for the beam signal — apodized of cosine Ic 0<Kj ^ Kmax Let μj be the processed main lobe enhancement factor; µj>1; Let p be the processed side lobe attenuation factor;
Start Leave I 1 I αDR ; → → = ; set the first processed beam signal to be 1 J = 1 while j < n Calculate

[0174] Referring again to Figure 6, in the implementation of exemplary preceding methods as signals Since nth beam and apodized cosine beam in depth Z: ( , ) u I nzre ( , ) c I nzr are acquired in 601, the parameter α of beamforming is then calculated at 62, according to a criterion that the force of 2 2 uc III α = +α rrr is minimized and the beam DR DR II α α = rr is formed at 603.
[0175] The parameter α is then passed through the look-up table 63 to obtain the parameters µi , ρi , κi , m γ , and S γ of beamforming and useful for the synthesis and decomposition of IDR and XDR beams that are appropriate for an imaging application. Since parameter α indicates the relative amount of desired signal and unwanted clutter at a sample location (nz, ) , clutter is small as α is small and large as α is large, parameters µi , ρi , κi , m γ , and S γ of beamforming useful for synthesis and decomposition of IDR and XDR beams can be a function of α.
[0176] The desired properties of a synthesized beam for better image quality vary depending on a series of system parameters such as: the scan head element density, the number of available channels in the original beam, the line density in an image, the number of parallel beams or beams being used, the frequency and bandwidth of the sonification signal, etc.; thus, different sets of parameters μiα( ) , pi(α) , Ki(α) , Ym(α) and YS(α) are preferred for different image processing applications. The specific functional relationship can be experimentally determined based on the desired image characteristics, the objects being imaged, the image system configuration, etc. IR μp K Y Y
[0177] The DR beam αDR and parameters i , i , i , m , S are used in processor 603 to form the desired IDR beam. The DR beam, IDR beam, and beamforming parameters can also be used to iteratively form the XDR beam on the 604 and 605 processors.
[0178] Figures 6L(1) - 6L(4) show an example of decomposing a DR beam of α = l using parameters K = 2, p = 0.125, y = 0.015625, n = 1 to synthesize an XDR beam by ^ ^ ^ ^ IXDR computation = IαM_K+pIαn_s+YIα using method 1, described above. The 3dB FWHM is 0.7122π; which is 21.6% narrower than the Sync beam. Since for α = 1, the DR beam is a Harming beam whose peak side lobe level is db-31. In the XDR beam synthesis process, the y parameter is used to attenuate the Hanning side lobe 20*log10(/) = -36.12 which results in -31 + 20*log10(/) = -67.12, as shown in Figure 6L (4). The side lobe attenuation of the synthesized XDR beam is the same as that of the Hanning beam at -18 db/octave.
[0179] In accordance with the preceding dynamic resolution beam synthesis techniques, the modalities DR/IDR/XDR beam synthesis performs the following operations on the XDR dynamic resolution beam signal synthesis, where the acquired signal from the nth beam Sync in depth Z: z : Iu (n, z) = Iur (n, z)+ jIui (n, z) and the signal acquired from the apodized nth beam of cosine in depth z: z:Ic(n,z) )=Icr(n,z)+ jIci(n,z): For I'.(n•z1* 0;
end sesignal (IDR _ i (n,z)) *signal (Ici (n,z))>0&mIi *IIDR _ i (n,z)l; IXDR i (n,Z) = IDRi (n,Z) + (P - 1) mIi (n,Z) . The end.
[0180] Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and modifications may be made in this document without departing from the spirit and scope of the invention as defined by the appended claims. Furthermore, the scope of this application is not intended to limit the particular modalities of the process, machine, fabrication, composition of matter, means, methods and steps described in the descriptive report. As those skilled in the art will readily appreciate through the disclosure of the present invention, processes, machines, fabrication, compositions of matter, means, methods or steps, currently existing or to be developed later, that substantially perform the same function or substantially achieve the same result which corresponding embodiments described herein may be used in accordance with the present invention. Accordingly, the attached claims are intended to include within its scope such processes, machines, fabrication, compositions of matter, means, methods or steps.

权利要求:
Claims (12)
[0001]
1. A method for operating an ultrasound system, comprising: - receiving signals from the transducer element from a plurality of ultrasound transducer elements (E1-EN); - producing a first beam and a second beam from the signals from the transducer element, the first beam being an apodized beam including a first main lobe component and a pair of first side lobes and the second beam being an apodized beam having a main lobe and side lobe component, the main lobe component of the second bundle being aligned with the pair of first side lobes of the first bundle; and - combining the first beam with a portion of the second beam to produce a dynamically resolving beam having a main lobe component and side lobes that are smaller in magnitude than the side lobe components of the first and second beams; characterized by the fact that a null at the center of the main lobe component of the second beam is aligned with a peak of the main lobe component of the first beam.
[0002]
2. Method according to claim 1, characterized in that it further comprises selecting a weighting factor α between zero and one inclusive, which represents the part of the second beam that is combined with the first beam to produce the dynamic resolution beam .
[0003]
3. Method according to claim 2, characterized in that the weighting factor α is selected by determining an amount of disorder in an unwanted direction, where α is smaller when the disorder is smaller and larger when the disorder is bigger.
[0004]
4. Method according to claim 2, characterized in that the first apodized beam signal is represented by a vector Iu and the second apodized beam signal is represented by a vector Ic, and the weighting factor α is determined according to the formula:
[0005]
5. Method according to claim 4, characterized in that Iu is a Sinc beam and Ic is an apodized cosine beam.
[0006]
6. Method according to claim 1, further comprising determining a main lobe component of the first apodized beam and a side lobe component of the dynamic resolution beam and creating a new beam having a main lobe component plus narrows that the main lobe component of the dynamic resolution beam by combining the determined main lobe component of the first apodized beam and a part of the side lobe component of the dynamic resolution beam.
[0007]
7. Method according to claim 6, characterized in that the main lobe component of the first apodized beam is determined by: - determining a dynamic resolution beam main lobe propagation; and - subtracting the main lobe propagation component from the dynamic resolution beam to produce the main lobe component from the first apodized beam.
[0008]
8. Method according to claim 7, characterized in that the propagation component of the main lobe of the dynamic resolution beam is determined by selecting the minimum of the dynamic resolution beam and the second apodized beam and the lobe component lateral dynamic resolution beam is determined by subtracting the main lobe component of the first apodized beam from the dynamic resolution beam.
[0009]
9. The method of claim 6, wherein the part of the side lobe component of the dynamic resolution beam combined with the main lobe component of the first apodized beam is represented by y and is selected to provide an outward scroll desired in the side lobes of the new bundle.
[0010]
10. Method according to claim 6, characterized in that it further comprises the sharpness of the main lobe component of the dynamic resolution beam by: - dividing the dynamic resolution beam into a narrow main lobe component and a lobe component main residual; and - adding the narrowed main lobe component with a part of the residual main lobe component and a part of a side lobe component of the dynamically resolving beam to produce a new bundle with another narrowed main lobe component and reduced side lobes.
[0011]
11. Method according to claim 10, further comprising: - iteratively producing a new beam with a portion of the main lobe intensified by: - dividing the new beam with the further narrowed main lobe component and the side lobes reduced to a narrow main lobe component and a residual main lobe component; and - adding the narrowed main lobe component with a residual main lobe component part and a side lobe component part of the dynamically resolving beam to produce an additional new beam with another narrowed main lobe component and reduced side lobes.
[0012]
12. System for performing the method for operating an ultrasound system as defined in any one of claims 1 to 11, characterized in that the system comprises a transducer (11) and a processor (214).

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同族专利:

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公开号 | 公开日

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JP5973349B2|2016-08-23|

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EP2498683A1|2012-09-19|

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US8876719B2|2014-11-04|

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CN102753104A|2012-10-24|

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EP2498683A4|2014-10-22|

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US20120289835A1|2012-11-15|

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US20160354062A1|2016-12-08|

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JP2016179313A|2016-10-13|

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EP2498683B1|2017-04-12|

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US20140363068A1|2014-12-11|

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JP2013509971A|2013-03-21|

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CN102753104B|2016-03-09|

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BR112012010958A2|2017-11-07|

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JP6227724B2|2017-11-08|

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法律状态:
2019-01-08| B06F| Objections, documents and/or translations needed after an examination request according [chapter 6.6 patent gazette]|

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2019-07-30| B06U| Preliminary requirement: requests with searches performed by other patent offices: procedure suspended [chapter 6.21 patent gazette]|

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2021-08-03| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|

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2021-09-08| B16A| Patent or certificate of addition of invention granted [chapter 16.1 patent gazette]|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 09/11/2010, OBSERVADAS AS CONDICOES LEGAIS. PATENTE CONCEDIDA CONFORME ADI 5.529/DF, QUE DETERMINA A ALTERACAO DO PRAZO DE CONCESSAO. |

优先权:

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