技术领域technical field
本发明整体上涉及超声成像系统，例如用于医学成像的超声成像系统，并特别涉及用于在超声成像系统中抑制杂波效应的方法与系统。The present invention relates generally to ultrasound imaging systems, such as those used in medical imaging, and more particularly to methods and systems for suppressing clutter effects in ultrasound imaging systems.
背景技术Background technique
超声医学成像在现代医学中发挥重要作用，随着新的开发产品进入市场其逐渐变得越来越重要。其中一种最常见的超声成像应用是超声心动图或心脏系统的超声成像。其它广泛的应用有产科学和妇科医学以及腹部成像，这里仅举几例。超声成像也在各种其它产业中使用，例如，用于硬件制造过程中的探伤检验。Ultrasound medical imaging plays an important role in modern medicine, which is gradually becoming more important as new developments enter the market. One of the most common ultrasound imaging applications is echocardiography, or ultrasound imaging of the heart system. Other widespread applications are obstetrics and gynecology and abdominal imaging, just to name a few. Ultrasound imaging is also used in various other industries, for example, for flaw detection inspection during hardware manufacturing.
超声成像系统一般产生相对地有噪声的图像，使得这些图像的分析和/或诊断成为受过高度训练的专家的任务。其中一种最有问题的成像副产物是妨碍感兴趣的数据的杂波，即，出现在成像平面中的不想要的信息。Ultrasound imaging systems generally produce relatively noisy images, making analysis and/or diagnosis of these images a task for highly trained specialists. One of the most problematic imaging by-products is clutter, ie, unwanted information that appears in the imaging plane, that interferes with the data of interest.
超声成像中的杂波的一个主要来源是探头主瓣外面的物体的有效成像(也被称为旁瓣杂波)。例如，在超声心动图中，探头主瓣外的主反射体一般是胸腔和肺。A major source of clutter in ultrasound imaging is the effective imaging of objects outside the probe's main lobe (also known as sidelobe clutter). For example, in echocardiography, the main reflectors outside the main lobe of the transducer are typically the chest cavity and lungs.
杂波的另一来源是多路径反射，也称为混响。在一些例子中，被扫描的组织相对于探头的几何关系以及组织的局部反射特性导致所传输的能量的很大份额在到达探头之前在组织中来回反射。因此，所测量的相对于探头的特定范围的信号可以包括来自想要的范围之外的其它范围的贡献。如果从其它范围发出的信号是高反射元件导致的，则它可以对图像质量产生很大影响。Another source of clutter is multipath reflections, also known as reverberation. In some instances, the geometry of the tissue being scanned relative to the probe and the local reflective properties of the tissue cause a significant fraction of the transmitted energy to reflect back and forth in the tissue before reaching the probe. Thus, the measured signal relative to a particular range of the probe may include contributions from other ranges than the desired range. Signals from other ranges can have a big impact on image quality if they are caused by highly reflective components.
用于加强想要的超声图像相对于杂波的可见性的常见方法(尤其在低回波反射性的病人中(肥胖病人中的一种常见现象))是采用造影剂。这种造影剂加强来自血液的超声反向散射并有助于它与周围组织的区别。例如，Krishna等人于1999年在Physics inMedicine and Biology的44卷、第681-694页发表的名称为“Sub-harmonic Generationfrom Ultrasonic Contrast Agents”的论文中描述了这种方法，其通过引用结合到本文。A common method for enhancing the visibility of the desired ultrasound image from clutter, especially in hypoechogenic patients (a common phenomenon in obese patients), is the use of contrast agents. This contrast agent enhances the backscatter of ultrasound from blood and helps it to be distinguished from surrounding tissue. Such an approach is described, for example, in a paper entitled "Sub-harmonic Generation from Ultrasonic Contrast Agents" by Krishna et al., Physics in Medicine and Biology, Vol. 44, pp. 681-694, 1999, which is hereby incorporated by reference .
采用谐波成像代替基波成像，即，以某个频率传输超声信号并以传输频率的两倍频率接收，也减少杂波效应。Spencer等人于1998年在American Journal of Cardiology的第82卷、第794-799页发表的名称为“Use of Harmonic Imaging withoutEchocardiographic Contrast to Improve Two-Dimensional Image Quality”的论文中描述了这种方法，其通过引用结合于本文。Using harmonic imaging instead of fundamental imaging, ie, transmitting ultrasound signals at a certain frequency and receiving at twice the transmitted frequency, also reduces clutter effects. Spencer et al. described this method in a paper entitled "Use of Harmonic Imaging without Echocardiographic Contrast to Improve Two-Dimensional Image Quality" published in American Journal of Cardiology, Vol. 82, pp. 794-799, 1998, which Incorporated herein by reference.
在2001年6月26日公告的Averkiou等人的名称为“Ultrasonic Tissue HarmonicImaging”的美国专利6,251,074描述了超声诊断成像系统和方法，其根据发射的基频的谐波回波分量产生组织谐波超声图像。基频波由阵列换能器发射以在焦点深度聚焦。随着发射的波穿透身体，谐波效应由于波分量开始聚焦而发展。来自组织的谐波响应被检测和显示，同时通过排除基频而减少来自基频响应的杂波。U.S. Patent 6,251,074 to Averkiou et al., entitled "Ultrasonic Tissue Harmonic Imaging," issued June 26, 2001, describes an ultrasonic diagnostic imaging system and method that generates tissue harmonic ultrasound from harmonic echo components of the transmitted fundamental frequency image. The fundamental wave is emitted by the array transducer to focus at the depth of focus. As the emitted waves penetrate the body, harmonic effects develop as the wave components become focused. Harmonic responses from the tissue are detected and displayed, while clutter from the fundamental frequency response is reduced by excluding the fundamental frequency.
此外，图像处理方法通过后处理已经发展用于检测在超声心动图图像中的受杂波影响的像素。Zwirn和Akselrod在2006年于Ultrasound in Medicine and Biology的32卷、第43-52页的名称为“Stationary Clutter Rejection in Echocardiography”的论文中提出了这种方法，其通过引用结合到本文。Furthermore, image processing methods have been developed for detecting clutter-affected pixels in echocardiographic images through post-processing. This method is proposed by Zwirn and Akselrod in a paper entitled "Stationary Clutter Rejection in Echocardiography" Ultrasound in Medicine and Biology, Vol. 32, pp. 43-52, 2006, which is hereby incorporated by reference.
其它方法使用辅助接收超声波束。在2011年10月25日公告的名称为“ClutterSuppression in Ultrasonic Imaging Systems”的美国专利8,045,777中，Zwirn描述了用于超声成像的方法，包括：朝目标发射超声辐射；接收来自目标区域的主要反射信号和一个或多个辅助反射信号形式的超声辐射的反射，其中每个反射信号与不同且明显的波束方向图相关联，其中所有反射信号都具有相同的频率；确定下述各项中的至少一个的解相关时间：主反射信号和一个或多个辅助反射信号；将线性组合应用到主反射信号和一个或多个辅助反射信号，以产生具有减少的杂波的输出信号，其中线性组合包括被确定用于每个角度和用于目标组织内的每个范围的多个复数权重，其中每个复数权重被选择为使得每一个由于杂波而被估算的反射无效，其中如果被确定的解相关时间超过指定阈值则反射会被确定为与杂波相关。Other methods use auxiliary reception of ultrasound beams. In U.S. Patent 8,045,777, issued October 25, 2011, entitled "ClutterSuppression in Ultrasonic Imaging Systems," Zwirn describes a method for ultrasound imaging comprising: transmitting ultrasound radiation toward a target; receiving primary reflected signals from the target area reflections of ultrasound radiation in the form of one or more secondary reflections, each of which is associated with a distinct and distinct beam pattern, wherein all reflections have the same frequency; determine at least one of The decorrelation time of : the main reflection signal and one or more auxiliary reflection signals; a linear combination is applied to the main reflection signal and one or more auxiliary reflection signals to produce an output signal with reduced clutter, where the linear combination includes being determining a plurality of complex weights for each angle and for each range within the target tissue, wherein each complex weight is selected such that each estimated reflection due to clutter is invalidated, wherein if the determined decorrelation Reflections are determined to be clutter-related for times longer than the specified threshold.
Yen和Seo在2009年6月4发表的名称为“Sidelobe Suppression in UltrasoundImaging using Dual Apodization with Cross-Correlation”的美国专利申请2009/0141957描述了在超声图像中抑制旁瓣的方法，该方法包括：发射聚焦的超声波束穿过子孔径进入目标并收集产生的回波；在接收中，采用第一变迹函数(apodization function)来创建第一数据集；在接收中，采用第二变迹函数来创建第二数据集；组合这两个数据集来创建组合的RF数据；计算每个像素的归一化互相关；对每个相关值执行阈值操作；以及将产生的互相关矩阵与组合的RF数据相乘。US Patent Application 2009/0141957 entitled "Sidelobe Suppression in Ultrasound Imaging using Dual Apodization with Cross-Correlation" published June 4, 2009 by Yen and Seo describes a method of suppressing side lobes in ultrasound images comprising: transmitting A focused ultrasound beam passes through the subaperture into the target and collects the resulting echoes; in reception, a first apodization function is used to create a first data set; in reception, a second apodization function is used to create second data set; combine the two data sets to create combined RF data; compute a normalized cross-correlation for each pixel; perform a thresholding operation on each correlation value; and compare the resulting cross-correlation matrix with the combined RF data multiplied.
另外一类当前可用的处理杂波的方法是在彩色多普勒流动成像中采用的一类杂波抑制算法。这些方法估算心腔或其它血管内的流动速度并抑制缓慢移动物体的影响；假设血液流动速度比周围组织的运动速度要快很多。例如，Herment等人在1996年于IEEETransactions on Biomedical Engineering的43卷、第919-927页的名称为“ImprovedEstimation of Low Velocities in Color Doppler Imaging by Adapting the MeanFrequency Estimator to the Clutter Rejection Filter”的论文中描述了这些方法，其通过引用结合到本文。Another class of currently available methods for dealing with clutter is a class of clutter suppression algorithms used in color Doppler flow imaging. These methods estimate the velocity of flow within a chamber of the heart or other blood vessel and suppress the effects of slow-moving objects; the assumption is that blood is flowing much faster than surrounding tissue. For example, Herment et al. describe in a paper entitled "Improved Estimation of Low Velocities in Color Doppler Imaging by Adapting the Mean Frequency Estimator to the Clutter Rejection Filter", IEEE Transactions on Biomedical Engineering, Vol. 43, pp. 919-927, 1996 These methods, which are incorporated herein by reference.
发明内容Contents of the invention
本发明的实施方式提供了用于在超声成像系统中减少杂波效应的方法与设备。Embodiments of the present invention provide methods and apparatus for reducing clutter effects in ultrasound imaging systems.
本发明提供一种超声成像的方法，所述方法包括：朝目标发射超声辐射并接收来自目标区域的主要反射信号和一个或多个辅反射信号形式的超声辐射的反射，其中每个反射信号都包括输入数据组并与不同且明显的波束方向图相关联；通过复合函数的使用，复合来自主反射信号和一个或多个辅反射信号的输入数据组，所述复合函数使用由输入数据组的空间分析产生的参数，所述复合函数参数源于以下项中的至少一项：The present invention provides a method of ultrasound imaging, the method comprising: transmitting ultrasound radiation toward a target and receiving reflections of the ultrasound radiation from the target region in the form of a primary reflection signal and one or more secondary reflection signals, wherein each reflection signal is Comprising input data sets and associated with distinct and distinct beam patterns; compounding the input data sets from the main reflection signal and one or more auxiliary reflection signals through the use of a compounding function using a combination of the input data sets Parameters resulting from spatial analysis, the composite function parameters are derived from at least one of the following:
(a)不同接收波束之间的局部相位相位差和/或局部幅度差和/或局部幅度比和/或局部复信号比，和/或一个或多个前述的参数的函数；(a) local phase phase differences and/or local amplitude differences and/or local amplitude ratios and/or local complex signal ratios between different receive beams, and/or functions of one or more of the aforementioned parameters;
(b)不同波束之间的局部相位差和/或局部幅度差和/或局部幅度比和/或局部复信号比的空间函数；(b) a spatial function of the local phase difference and/or local amplitude difference and/or local amplitude ratio and/or local complex signal ratio between different beams;
(c)不同接收波束中的局部幅度和/或局部相位和/或局部复信号的空间函数之间的局部差和/或局部比；(c) local differences and/or local ratios between local magnitudes and/or local phases and/or local complex signal spatial functions in different receive beams;
(d)应用多个时间带通滤波器到不同接收波束中的局部幅度和/或局部相位和/或局部复信号，应用空间分析到多个时间带通滤波器的输出并组合结果；(d) applying multiple temporal bandpass filters to local magnitudes and/or local phases and/or local complex signals in different receive beams, applying spatial analysis to the outputs of the multiple temporal bandpass filters and combining the results;
(e)应用多个时间带通滤波器到不同接收波束之间的局部相位差和/或局部幅度差和/或局部幅度比和/或局部复信号比，应用空间分析到多个时间带通滤波器的输出并组合结果；或(e) applying multiple temporal bandpass filters to local phase differences and/or local amplitude differences and/or local amplitude ratios and/or local complex signal ratios between different receive beams, applying spatial analysis to multiple temporal bandpasses the output of the filter and combine the results; or
(f)不同波束之间的局部相位差和/或局部幅度差和/或局部幅度比的空时函数，其中不同波束之间的局部相位差和/或局部幅度差和/或局部幅度比的空间导数，在局部时间过滤之后应用；或其中不同波束中的幅度和/或相位和/或复信号的空间函数之间的局部差和/或局部比在局部时间过滤之后应用。(f) a space-time function of the local phase difference and/or local amplitude difference and/or local amplitude ratio between different beams, where the local phase difference and/or local amplitude difference and/or local amplitude ratio between different beams Spatial derivatives, applied after local temporal filtering; or wherein local differences and/or local ratios between amplitudes and/or phases in different beams and/or spatial functions of the complex signal are applied after local temporal filtering.
本发明的其它方面在权利要求书中被详述。Other aspects of the invention are specified in the claims.
附图说明Description of drawings
本发明用于在超声成像系统中的杂波抑制，其参考附图、仅通过实例的方式在本文中进行描述。The present invention for clutter suppression in ultrasound imaging systems is described herein by way of example only with reference to the accompanying drawings.
现在详细地具体参考附图，需要强调的是，所示的详细说明是通过实例的方式并仅用于本发明的优选实施方式的说明性讨论的目的，并且为了提供被认为是本发明原理和概念方面的最有用且容易理解的描述而被示出。出于这个考虑，并不试图显示比用于本发明的基本理解所必须的更详细的本发明的结构细节，结合附图做出的描述使本领域的技术人员清楚本发明的各种形式可如何在实际中应用。With specific reference now to the drawings in detail, it is stressed that the detailed description shown is by way of example and for purposes of illustrative discussion of the preferred embodiments of the invention only and to provide what are believed to be the principles and principles of the invention. The most useful and easy-to-understand descriptions of the conceptual aspects are shown. In this regard, no attempt is made to show structural details of the invention in greater detail than is necessary for a fundamental understanding of the invention, the description taken in conjunction with the accompanying drawings will make apparent to those skilled in the art that various forms of the invention may be possible. How to apply it in practice.
图1A是根据本发明的实施方式的超声成像系统的示意性的、形象化的图示；Figure 1A is a schematic, pictorial illustration of an ultrasound imaging system according to an embodiment of the present invention;
图1B是根据本发明的实施方式的在超声成像系统中所使用的探头的示意性的、形象化的图示；Figure 1B is a schematic, pictorial illustration of a probe used in an ultrasound imaging system according to an embodiment of the present invention;
图2是根据本发明的实施方式的，根据作为方位角的函数的增益所限定的两个示例性接收波束的波束方向图的示意图；FIG. 2 is a schematic diagram of beam patterns of two exemplary receive beams defined in terms of gain as a function of azimuth angle, in accordance with an embodiment of the present invention;
图3A是根据本发明的实施方式的，对于作为方位角的函数的点状反射器所限定的图2的两个接收波束之间的预期幅度比的示意图，其中方位刻度与图2中的不同，提供了在接近0°的角度上的放大；3A is a schematic diagram of the expected amplitude ratio between the two receive beams of FIG. 2 defined for a point reflector as a function of azimuth, where the azimuth scale is different from that in FIG. 2, in accordance with an embodiment of the present invention , providing magnification at angles close to 0°;
图3B是根据本发明的实施方式的，对于作为方位角的函数的点状反射器所限定的图2的两个接收波束之间的预期相位差的示意图，其中方位刻度与图3A中的匹配。3B is a schematic diagram of the expected phase difference between the two receive beams of FIG. 2 defined for a point reflector as a function of azimuth, where the azimuth scale matches that of FIG. 3A, in accordance with an embodiment of the invention .
具体实施方式detailed description
系统描述System specification
广义上讲，本发明涉及用于在超声成像系统中抑制杂波效应的方法和系统。在一些实施方式中，这些方法与系统也导致超声图像的横向分辨率(即，沿着垂直于超声波束的中心线方向的分辨率)的加强。Broadly, the present invention relates to methods and systems for suppressing clutter effects in ultrasound imaging systems. In some embodiments, the methods and systems also result in enhanced lateral resolution (ie, resolution along a direction perpendicular to the centerline of the ultrasound beam) of the ultrasound image.
在详细解释本发明的至少一个实施方式之前，应理解的是，本发明没有将其应用限制到在下面描述中阐述或在附图中示出的组件的结构和布置的细节。本发明能够是其它实施方式或能够以各种方式应用或实施。还应理解的是，本文采用的措辞和术语是以描述为目的的而不应该被当作限制。Before at least one embodiment of the invention is explained in detail, it is to be understood that the invention is not limited in application to the details of construction and arrangement of components set forth in the following description or shown in the drawings. The invention is capable of other embodiments or of being applied or carried out in various ways. It is also to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.
图1A是根据本发明的实施方式的超声成像系统20的示意性的、形象化的图示。FIG. 1A is a schematic, pictorial illustration of an ultrasound imaging system 20 in accordance with an embodiment of the present invention.
系统20包括采用超声辐射来扫描病人的器官的超声扫描器22。显示单元24显示扫描的图像。探头26通过线缆28连接到扫描器22，其通常靠在病人身体上以便于成像出具体身体结构，例如心脏(称作“目标”)。可选择地，探头可以调整用于插入身体，例如，经食道或经阴道的配置。探头发射和接收成像所需的超声波束。扫描器22包括用于控制探头26和处理由探头接收的信号的控制和处理电路。System 20 includes an ultrasound scanner 22 that scans an organ of a patient using ultrasound radiation. The display unit 24 displays the scanned image. Probe 26 is connected by cable 28 to scanner 22, which is typically held against the patient's body in order to image a specific body structure, such as the heart (referred to as a "target"). Alternatively, the probe can be adapted for insertion into the body, for example, in a transesophageal or transvaginal configuration. The probe emits and receives the ultrasound beams required for imaging. Scanner 22 includes control and processing circuitry for controlling probe 26 and processing signals received by the probe.
图1B是根据本发明的实施方式的在成像系统20中使用的探头26的示意性、形象化的图示。探头包括换能器30的阵列，例如压电换能器，其配置成作为相控阵来运行。在发射时，换能器将由扫描器22产生的电信号转换成发射到病人身体中的超声辐射的波束。在接收时，换能器接收从不同身体组织反射的超声辐射，并将它转换成发送到扫描器22以用于处理的电信号。Figure IB is a schematic, pictorial illustration of probe 26 used in imaging system 20, in accordance with an embodiment of the present invention. The probe includes an array of transducers 30, such as piezoelectric transducers, configured to operate as a phased array. On transmission, the transducer converts the electrical signals generated by scanner 22 into beams of ultrasound radiation that are transmitted into the patient's body. On reception, the transducer receives ultrasound radiation reflected from various body tissues and converts it into electrical signals which are sent to the scanner 22 for processing.
探头26一般包括几十个甚至多达几百个以水平线性阵列布置的换能器30。阵列的水平孔径(一般是几厘米数量级的)影响探头的最小水平波束宽度和产生的水平角分辨率。垂直的波束宽度可以通过声透镜调整。一些探头(称作“11/2维探头”)包括在垂直维度上的几行换能器，提供垂直扇形的波束方向图。其它探头包括完整的二维(或多维)换能器阵列，能够控制水平和垂直方向的波束方向图。词语“水平的”和“垂直的”在本文仅为使用方便，因为阵列在成像过程中可以放置成相对于病人身体的任何合适的方位上。Probe 26 typically includes tens or even up to hundreds of transducers 30 arranged in a horizontal linear array. The horizontal aperture of the array (typically on the order of a few centimeters) affects the minimum horizontal beamwidth of the probe and the resulting horizontal angular resolution. The vertical beam width can be adjusted by the acoustic lens. Some probes (referred to as "11 /2 -dimensional probes") include several rows of transducers in the vertical dimension, providing a vertical fan-shaped beam pattern. Other probes include complete two-dimensional (or multi-dimensional) transducer arrays capable of steering beam patterns in both horizontal and vertical directions. The words "horizontal" and "vertical" are used herein for convenience only, as the array may be placed in any suitable orientation relative to the patient's body during imaging.
单个换能器阵列可以产生不同波束方向图，其主瓣可以指向不同方向。在发射时，主瓣的方向的设定一般通过调整提供给不同换能器的信号的相对相位和/或相对时延。在接收时，主瓣的方向的设定一般通过调整引入到由每个换能器接收的信号的相移和/或时延。A single transducer array can produce different beam patterns, with its main lobe pointing in different directions. During transmission, the direction of the main lobe is generally set by adjusting the relative phases and/or relative time delays of signals provided to different transducers. On reception, the direction of the main lobe is typically set by adjusting the phase shift and/or time delay introduced to the signal received by each transducer.
在发射和接收时的波束方向图都可以通过应用不同的变迹法来调整。在接收时，变迹法是在结合所有换能器的输出以生成整个阵列的输出信号之前，将乘性系数(“变迹法系数”)乘以每个换能器的输出信号的过程。对等的过程在发射时执行(在很多例子中，在发射时采用恒定的变迹法)。The beam pattern at both transmit and receive can be adjusted by applying different apodization methods. On reception, apodization is the process of multiplying the output signal of each transducer by a multiplicative coefficient ("apodization coefficient") before combining the outputs of all transducers to generate the output signal of the entire array. The peer-to-peer process is performed at launch (in many instances, with constant apodization at launch).
令k为换能器索引(k应该覆盖所有换能器，即使换能器阵列包括多于一个维度)，sk是由换能器k测得的信号，ak是换能器k在接收时的变迹法系数，是换能器k在接收时的相移。用于获得在时间t的信号S，在接收时波束形成可以采用等式(1)执行：Let k be the transducer index (k should cover all transducers, even if the transducer array includes more than one dimension), sk is the signal measured by transducer k, and ak is the signal received by transducer k The apodization coefficient when is the phase shift of transducer k when receiving. For obtaining the signal S at time t, beamforming at reception can be performed using equation (1):
可替代地，当采用时延代替相移时，其中τk是对于换能器k的时延，对于在接收时的波束形成可以采用等式(2)：Alternatively, when time delay is used instead of phase shift, where τk is the time delay for transducerk , equation (2) can be used for beamforming at receive:
(2) S(t)＝Σkak(t)sk(t-τk)(2) S(t)＝Σk ak (t)sk (t-τk )
相似的等式可以用于组合的时延与相移设计。可比的等式也可以在发射时使用。Similar equations can be used for combined delay and phase shift designs. Comparable equations can also be used at launch.
基于系统设计，到达不同换能器的信号可以在不同的波束形成阶段采样(通过在扫描器22中的一个或多个模数转换器)，例如，分别对于每个换能器，对于不同的换能器组，或对于所有组合的换能器。等式(1)和等式(2)以及它们的组合或变形可应用于所有这些例子。Based on the system design, the signals arriving at the different transducers may be sampled (via one or more analog-to-digital converters in the scanner 22) at different beamforming stages, e.g., separately for each transducer, for different group of transducers, or for all combined transducers. Equation (1) and equation (2) and their combinations or variations are applicable to all these examples.
此外，一些系统对于所有组合的换能器(即，在波束级别)执行采样，但是采用多于一组变迹法系数ak和/或多于一组相移和/或多于一组时延τk，设置通常被称作多线采集或MLA。在MLA配置中，在发射时采用的波束方向图一般比在接收时采用的波束方向图宽，以便给由不同接收波束覆盖的体积的大部分或全部提供超声能量。Furthermore, some systems perform sampling for all combined transducers (i.e., at the beam level), but employ more than one set of apodization coefficients ak and/or more than one set of phase shifts and/or more than one set of time delays τk , the setup is often referred to as multi-line acquisition or MLA. In an MLA configuration, the beam pattern employed in transmit is generally wider than the beam pattern employed in receive in order to provide ultrasound energy to most or all of the volume covered by the different receive beams.
在采样之前，某些扫描器22应用与发射波形匹配的模拟滤波和/或模拟下变频，然而其它的扫描器应用数字匹配滤波和/或数字下变频。匹配滤波和/或下变频可以在任何波束形成阶段应用。Before sampling, some scanners 22 apply analog filtering and/or analog downconversion to match the transmitted waveform, while others apply digital matched filtering and/or digital downconversion. Matched filtering and/or downconversion can be applied at any beamforming stage.
某些扫描器22在一个或多个波束形成阶段采样实数数据，然而其它的扫描器采用正交接收器，提供复数采样，包括实数同相分量和虚数正交分量。Certain scanners 22 sample real data in one or more beamforming stages, while others employ quadrature receivers, providing complex samples, including real in-phase components and imaginary quadrature components.
其他类型的扫描器22在接收时采用多个并行波束，其中的每一个具有不同的波形(例如，不同的中心发射频率、不同的脉冲编码配置)。在这些例子中，对应于其中一个发射波形，每个接收波束一般采用特定的匹配滤波器生成。Other types of scanners 22 employ multiple parallel beams in receive, each of which has a different waveform (eg, different center transmit frequency, different pulse code configuration). In these examples, each receive beam is typically generated using a specific matched filter corresponding to one of the transmit waveforms.
应当注意的是，在一些探头设计中，采用平面阵列代替相控阵。在这些例子中，仅有一小组预定时延和/或相移被换能器阵列支持，其中由这样的每个组形成的波束一般单独采样。其他探头设计不采用换能器阵列，而是代之以把单个换能器分配给每个发射波束和/或接收波束。It should be noted that in some probe designs, planar arrays are used instead of phased arrays. In these examples, only a small set of predetermined time delays and/or phase shifts are supported by the transducer array, where the beams formed by each such group are typically sampled individually. Other probe designs do not use transducer arrays, but instead assign a single transducer to each transmit and/or receive beam.
探头26一般扫描感兴趣的区域，其可以是一维的(1D)、二维的(2D)或三维的(3D)，通过以下的一个或多个：Probe 26 generally scans a region of interest, which may be one-dimensional (1D), two-dimensional (2D), or three-dimensional (3D), by one or more of the following:
(a)电子束控制，即，通过调整提供给不同换能器的信号的相对相位和/或相对时延来改变主瓣的方向。(a) Beam steering, ie changing the direction of the main lobe by adjusting the relative phase and/or relative time delay of the signals supplied to different transducers.
(b)换能器阵列的相位中心的电子变化，通过调整变迹法模式来执行，例如，通过设定变迹法模式的某些部分为0。因此，波束相位中心和其主瓣的峰值(“波束方向”)之间的向量可以在空间上移位，产生与之前向量平行的另一个向量。(b) Electronic variation of the phase center of the transducer array, performed by adjusting the apodization pattern, eg by setting certain parts of the apodization pattern to zero. Thus, the vector between the phase center of a beam and the peak of its main lobe ("beam direction") can be shifted spatially, producing another vector parallel to the previous vector.
(c)机械波束控制，即，机械地移动换能器阵列的部分或全部，由此影响其主瓣的方向。(c) Mechanical beam steering, ie mechanically moving part or all of the transducer array, thereby affecting the direction of its main lobe.
用于杂波抑制的系统配置System configuration for clutter suppression
在本发明的一些实施方式中，一个或多个辅助接收波束用来抑制杂波效应。辅助接收波束可以采用本领域中已知的任何配置来生成，包括但不局限于以上描述的那些。In some embodiments of the invention, one or more auxiliary receive beams are used to suppress clutter effects. The auxiliary receive beams may be generated using any configuration known in the art, including but not limited to those described above.
辅助接收波束可以单独分配给每个通常用于成像的波束(“主波束”)，或主波束组。后一种配置可能是有用的，例如在MLA配置中，其中一般在接收时并行采用多个主波束，对应于单个发射波束，并且可以定义一个或多个辅助波束。Auxiliary receive beams can be assigned individually to each beam normally used for imaging ("main beam"), or to groups of main beams. The latter configuration may be useful, for example, in an MLA configuration, where typically multiple main beams are employed in parallel at receive, corresponding to a single transmit beam, and one or more auxiliary beams may be defined.
辅助接收波束可以与相应的主接收波束(或多个主接收波束)同时产生、或不同时产生。也能够考虑组合，即，一些辅助接收波束可以与相应的主接收波束(或多个主接收波束)同时产生，而其它的可以不同时产生。可以定义在不同波束之间的不同的相对定时顺序，例如，改变主接收波束与辅助接收波束的产生。如果一些或所有辅助接收波束与相应的主接收波束(或多个主接收波束)在不同的时间产生，那么分开的发射波束可以采用相同或不同的波束方向图而用于主接收波束和辅助接收波束或其组。The auxiliary receive beam may be generated simultaneously with the corresponding main receive beam (or multiple main receive beams), or not. Combinations can also be considered, ie some auxiliary receive beams may be generated simultaneously with the corresponding main receive beam (or multiple main receive beams), while others may not be generated simultaneously. Different relative timing sequences between the different beams can be defined, for example, changing the generation of the main and auxiliary receive beams. If some or all of the auxiliary receive beams are generated at different times than the corresponding main receive beam (or multiple main receive beams), then separate transmit beams may employ the same or different beam patterns for the main receive beam and the auxiliary receive beams. Beams or groups thereof.
在示例性实施方式中，使用一个主接收波束和一个辅助接收波束，与单个发射波束或两个独立的发射波束相对应。在这个例子中，辅助接收波束可以具有与主接收波束不同的波束方向图，例如，它可以指向同一方向但它的波束宽度可能会更宽(或更窄)。In an exemplary embodiment, one main receive beam and one auxiliary receive beam are used, corresponding to a single transmit beam or two separate transmit beams. In this example, the auxiliary receive beam may have a different beam pattern than the main receive beam, for example, it may point in the same direction but its beamwidth may be wider (or narrower).
在其他的示例性实施方式中，与MLA配置相对应，多个并行的主接收波束(例如，16或32个)可以和单个传输波束一起使用，并且一个辅助接收波束被添加以用于所有并行的接收波束。在大多数MLA例子中，用于所有主接收波束的波束方向图是相似的，但每个主接收波束指向稍微不同的方向。为了提供用于所有主接收波束的参考信息，辅助接收波束可以比它们中的一些更宽，例如，它的宽度可能与发射波束的宽度相匹配。In other exemplary embodiments, multiple parallel main receive beams (e.g., 16 or 32) may be used with a single transmit beam, corresponding to an MLA configuration, and one auxiliary receive beam is added for all parallel receive beams. the receiving beam. In most MLA examples, the beam patterns for all main receive beams are similar, but each main receive beam points in a slightly different direction. In order to provide reference information for all main receive beams, the auxiliary receive beam may be wider than some of them, eg its width may match that of the transmit beam.
在另外的其他示例性实施方式中，多个主接收波束可以和单个发射波束一起使用，其中一个或多个辅助接收波束可以被添加用于每个主接收波束或主接收波束的每个组。In still other exemplary embodiments, multiple main receive beams may be used with a single transmit beam, where one or more auxiliary receive beams may be added for each main receive beam or each group of main receive beams.
在某些实施方式中，在不同的计算背景中，一个或多个接收波束可以被同时当作主接收波束和辅助接收波束。In certain embodiments, one or more receive beams may be considered both primary receive beams and auxiliary receive beams in different computing contexts.
杂波抑制方法Clutter suppression method
在本发明的实施方式中，复合信息由一个或多个主接收波束以及一个或多个辅助接收波束提供，以便于提供杂波抑制的输出。在匹配滤波和/或下采样之前或之后，该过程可以在扫描器22的各个处理阶段中应用并且可以应用到不同的数据类型上(例如，模拟的或数字的)，也可应用到实数或复数样本上。In an embodiment of the invention, composite information is provided by one or more main receive beams and one or more auxiliary receive beams in order to provide a clutter suppressed output. This process can be applied in various processing stages of the scanner 22 and can be applied to different data types (e.g., analog or digital), before or after matched filtering and/or downsampling, and can be applied to real or on complex samples.
在一些例子中，可能需要将被本领域的专业人员轻易理解的转换。例如，一些实施方式要求用于每个接收波束的输入数据是复数。在这些例子中，如果用于一个或多个接收波束的输入数据是实数，则对于每个接收波束Hilbert变换可被用于实数数据，如果必要的话，Hilbert反变换可以应用到杂波抑制输出。In some instances, transformations that would be readily understood by those skilled in the art may be required. For example, some implementations require that the input data for each receive beam be complex. In these examples, if the input data for one or more receive beams is real, then for each receive beam a Hilbert transform can be applied to the real data and, if necessary, an inverse Hilbert transform can be applied to the clutter suppressed output.
在扫描器22分别为每个换能器或换能器的不同组执行采样的配置中，杂波抑制处理可以分别应用于换能器的不同组。在这种例子中，“合成的”主接收波束和辅助接收波束可以仅用于计算目的而分别对于换能器的每个组定义，并且用于不同换能器组的杂波抑制的输出可以用于波束形成的其他阶段。In configurations where the scanner 22 performs sampling separately for each transducer or different groups of transducers, the clutter suppression process may be applied separately to the different groups of transducers. In such an example, the "synthetic" main and auxiliary receive beams can be defined separately for each group of transducers for computational purposes only, and the output for the clutter suppression of the different transducer groups can be Used in other stages of beamforming.
在某些实施方式中，用于每个主接收波束和/或辅助接收波束的信息可以描述为实数或复数测量数组，其中的每一个对应于被可应用波束的主瓣(和旁瓣)覆盖的特定体积，其在介质(相对于探头26)中的超声波的连续相同时间表面之间，一般但不一定匹配恒定的时间间隔。每个这样的体积一般被称为体积像素或体元。样本通常被称作距离门限，因为当穿过软组织时声速没有很大改变，使得相同时间表面能近似被称作等距(iso-range)表面。In some embodiments, the information for each main receive beam and/or auxiliary receive beam may be described as an array of real or complex measurements, each of which corresponds to the main lobe (and side lobe) coverage of the applicable beam A specific volume of , which typically but not necessarily matches a constant time interval between successive identical time surfaces of ultrasound in the medium (relative to the probe 26 ). Each such volume is generally referred to as a volume pixel or voxel. The samples are often referred to as distance-gated because the speed of sound does not change much when passing through soft tissue, so that the same time surface can be approximately referred to as an iso-range surface.
在一些实施方式中，感兴趣的一维、二维或三维区域由扫描器22扫描。扫描可以通过本领域已知的任何方法实施，包括但不局限于以上所提到的技术。例如，不同的波束可以具有相同的相位中心但不同的波束方向。在这种例子中，在2D扫描中一般采用极坐标系，而在3D扫描中一般采用球坐标系。当采用极坐标系时，每个体元的位置可以通过相应的距离门限索引和相对于探头26的宽面(broadside)的波束的角方向限定，其中探头的宽面由在其相位中心垂直于探头26的表面的线来限定，并且其中所述角方向在欧氏空间中可由方位角来限定，或由正弦空间中的u坐标限定。相似地，当采用球坐标系时，每个体元的位置可以由相应的距离门限索引和相对于探头26的宽面的波束的角方向来限定，其中角方向可以由方位角和仰角来限定和/或由正弦空间中的(u，v)坐标来限定。In some embodiments, a one-, two-, or three-dimensional region of interest is scanned by scanner 22 . Scanning may be performed by any method known in the art, including but not limited to the techniques mentioned above. For example, different beams may have the same phase center but different beam directions. In this example, a polar coordinate system is generally used in 2D scanning, and a spherical coordinate system is generally used in 3D scanning. When using a polar coordinate system, the position of each voxel can be defined by the corresponding distance threshold index and the angular orientation of the beam relative to the broadside of the probe 26, where the broadside of the probe is defined by the angle at its phase center perpendicular to the probe 26. 26, and wherein the angular direction may be defined by the azimuth angle in Euclidean space, or by the u-coordinate in sinusoidal space. Similarly, when using a spherical coordinate system, the position of each voxel can be defined by the corresponding range threshold index and the angular direction of the beam relative to the broadside of the probe 26, where the angular direction can be defined by the azimuth and elevation angles and / or defined by (u,v) coordinates in sinusoidal space.
另外地或选择性地，不同波束可以具有不同的相位中心，其中波束可以或可以不相互平行。在平行波束的例子中，可以采用2D或3D笛卡尔坐标系，其中每个体元的位置通过其对应的距离门限索引和相位中心的位置来限定。Additionally or alternatively, different beams may have different phase centers, where the beams may or may not be parallel to each other. In the case of parallel beams, a 2D or 3D Cartesian coordinate system can be used, where the position of each voxel is defined by its corresponding range-gate index and the position of the phase center.
不管使用的扫描方法和坐标系，由一个或多个接收波束(其可以是或可以不是并行的)收集的在每个时间带(“帧”)中的数据集可以采用本领域中已知的任何体元布置而组织在1D、2D或3D数组(“扫描的数据数组”)中，其中进入到阵列中的每个索引相关于不同的轴(例如，在极坐标系中，可以使用距离门限索引和方向索引)，使得在坐标系的一个或多个轴中的相互临近的体元在相应的轴中也具有相似的索引。在某些例子中，扫描的数据数组可以采用与扫描方法不对应的坐标系，例如，所有接收波束可以具有相同的相位中心但不同的波束方向，但扫描的数据数组可以使用笛卡尔坐标系而不是极坐标系或球坐标系。这可以采用本领域中已知的任何方法通过空间内插和/或外插获得，例如，最近邻插值法、线性内插法、样条函数或平滑样条内插法、等等。Regardless of the scanning method and coordinate system used, the data sets in each time slot ("frame") collected by one or more receive beams (which may or may not be in parallel) may employ Any voxel arrangement organized in a 1D, 2D or 3D array ("scanned data array"), where each index into the array is related to a different axis (e.g. in polar coordinates, distance gating can be used index and direction index), so that voxels adjacent to each other in one or more axes of the coordinate system also have similar indices in the corresponding axes. In some examples, the scanned data array may use a coordinate system that does not correspond to the scanning method, for example, all receive beams may have the same phase center but different beam directions, but the scanned data array may use a Cartesian coordinate system instead of Not polar or spherical coordinates. This may be obtained by spatial interpolation and/or extrapolation using any method known in the art, eg nearest neighbor interpolation, linear interpolation, spline or smoothing spline interpolation, and the like.
在一些实施方式中，扫描的数据数组遵守下面的要求，在该例子中扫描的数据数组被称作“通用配置扫描数据数组”：In some embodiments, the scanned data array complies with the following requirements, in this example the scanned data array is referred to as a "generic configuration scanned data array":
(a)在扫描数据数组中的所有数据对应于有着相同波束方向图的接收波束，也许，除了平移和/或旋转。(a) All data in the scan data array correspond to receive beams with the same beam pattern, except, perhaps, translation and/or rotation.
(b)在扫描数据数组中的所有数据都对应于在接收时采用相同中心频率的接收波束。(b) All the data in the scan data array correspond to receive beams using the same center frequency at the time of reception.
(c)在扫描数据数组中的所有数据对应于与采用相同波形和相同发射波束方向图的发射波束一起使用的接收波束，也许，除了平移和/或旋转。(c) All data in the scan data array corresponds to a receive beam used with a transmit beam employing the same waveform and same transmit beam pattern, except perhaps translation and/or rotation.
(d)扫描数据数组中的数据来源于接收波束，其可能是并行的，被分成多个组，其每个是并行的(这是当使用MLA配置时的最常见情况)，或非并行的。在其它实施方式中，可能不满足要求(a)-(d)中的一个或多个。(d) The data in the scan data array originates from the receive beams, which may be parallel, divided into multiple groups, each of which is parallel (this is the most common case when using the MLA configuration), or non-parallel . In other embodiments, one or more of requirements (a)-(d) may not be met.
复合函数Composite function
在示例性实施方式中，由主接收波束与一个或多个相关联的辅助接收波束提供的信息的整合，通过计算两个或多个接收波束中局部信号的函数(“复合函数”)来执行，其中词语“局部信号”指的是某体积区域，其被多于一个的接收波束部分或完全地覆盖，例如，在多个接收波束具有相同采样频率的情况中的不同接收波束的特定距离门限索引。在每个这种接收波束中的局部信号可以通过为基波成像设置匹配滤波器而生成(即，利用中心位于相应的发射波束的中心频率的接收频带)，或为谐波成像设置匹配滤波器而生成(即，利用中心位于一个频率的接收频带，该频率为相应的发射波束的中心频率乘以自然数得到的频率(发射频率的谐波)。在一些实施方式中，不同接收波束可以使用发射频率的不同谐波，包括但不局限于第一谐波(即，基波成像)。对于进入扫描数据数组的每个记录和/或每一帧可以使用复合函数的输出，而非在由超声成像系统进行的任何进一步处理中对于主接收波束的测量信号，例如：In an exemplary embodiment, the integration of the information provided by the main receive beam and one or more associated auxiliary receive beams is performed by computing a function ("composite function") of the local signals in the two or more receive beams , where the term "local signal" refers to a volumetric area that is partially or completely covered by more than one receive beam, e.g. a specific distance threshold for different receive beams in the case of multiple receive beams with the same sampling frequency index. The localized signal in each such receive beam can be generated by setting a matched filter for fundamental imaging (i.e., using a receive frequency band centered at the center frequency of the corresponding transmit beam), or by setting a matched filter for harmonic imaging Instead, generate (i.e., utilize a receive band centered at a frequency that is the frequency (harmonic of the transmit frequency) obtained by multiplying the center frequency of the corresponding transmit beam by a natural number. In some embodiments, different receive beams may use transmit different harmonics of frequency, including but not limited to the first harmonic (i.e., fundamental imaging.) The output of the composite function can be used for each record and/or each frame entering the scan data array, rather than the Measurement signal for the main receive beam in any further processing by the imaging system, e.g.:
(a)对数压缩，即，计算局部信号幅度的对数。(a) Logarithmic compression, ie computing the logarithm of the local signal magnitude.
(b)时间增益控制，即，将距离相关的校正应用于介质中的信号衰减。(b) Temporal gain control, ie, applying a distance-dependent correction to signal attenuation in the medium.
(c)全局增益控制。(c) Global gain control.
(d)多普勒处理，例如，用于彩色多普勒流动成像、组织多普勒成像和/或脉冲多普勒研究。注意，多普勒处理一般需要分析来自用于每个可应用体元的两个或多个脉冲的数据。(d) Doppler processing, eg, for color Doppler flow imaging, tissue Doppler imaging and/or pulsed Doppler studies. Note that Doppler processing generally requires analysis of data from two or more pulses for each applicable voxel.
在一些实施方式中，复合函数可以采用从以下至少一个中得到的参数(“复合函数参数”)：In some embodiments, a composite function may take parameters derived from at least one of the following ("composite function parameters"):
(a)在不同接收波束之间的局部相位差和/或幅度差和/或幅度比，和/或前述参数的一个或多个的函数，例如，转换成分贝单位的幅度比；(a) local phase differences and/or amplitude differences and/or amplitude ratios between different receive beams, and/or functions of one or more of the foregoing parameters, for example, amplitude ratios converted to decibel units;
(b)在不同波束间的局部相位差和/或幅度差和/或幅度比的空间函数，例如，所述参数的的空间导数，使用的是本领域已知的任何算子，比如和(b) a spatial function of the local phase difference and/or amplitude difference and/or amplitude ratio between different beams, e.g. the spatial derivative of said parameter, using any operator known in the art, such as with
(c)在不同接收波束中的局部幅度和/或相位和/或复信号的空间函数间的局部差和/或局部比，例如，沿特定空间轴的局部幅度的导数比；沿特定空间轴的局部归一化的幅度的导数比，其中局部归一化的导数被定义为由局部信号导数除以局部信号；局部幅度的空间导数比，其中空间导数用“拉普拉斯滤波器”来计算；局部幅度归一化的空间导数的比，其中的空间导数用“拉普拉斯滤波器”来计算；归一化的幅度范围的比，其中归一化的信号范围被定义为最大值与最小值间的差，除以均值，其中异常排除(outlierrejection)方案可在最小、最大和/或平均统计函数之前应用；如此等等。(c) Local differences and/or local ratios between local amplitudes and/or phases and/or spatial functions of complex signals in different receive beams, for example, ratios of derivatives of local amplitudes along a particular spatial axis; along a particular spatial axis The derivative ratio of the locally normalized magnitude, where the locally normalized derivative is defined as the local signal derivative divided by the local signal; the spatial derivative ratio of the local magnitude, where the spatial derivative is defined by a "Laplace filter" to calculate; the ratio of the spatial derivatives of the local amplitude normalization, where the spatial derivative is calculated using a "Laplace filter"; the ratio of the normalized amplitude range, where the normalized signal range is defined as the maximum The difference between the value and the minimum, divided by the mean, where outlier rejection schemes can be applied before the min, max and/or mean statistical functions; and so on.
(d)不同波束之间的局部相位差和/或幅度差和/或幅度比的时间函数，例如，不同的时间上的低通、带通或高通滤波器。(d) Time function of the local phase difference and/or amplitude difference and/or amplitude ratio between different beams, eg low-pass, band-pass or high-pass filters at different times.
(e)不同波束之间的局部相位差和/或幅度差和/或幅度比的空时函数，例如，在局部的时间滤波之后应用的，不同波束之间的局部相位差和/或幅度差和/或幅度比的空间导数；在局部时间滤波之后应用的，不同波束中的幅度和/或相位和/或复信号的空间导数之间的局部差和/或比；如此等等。(e) Space-time functions of the local phase and/or amplitude differences and/or amplitude ratios between different beams, e.g., after local temporal filtering applied and/or spatial derivatives of amplitude ratios; local differences and/or ratios between amplitudes and/or phases in different beams and/or spatial derivatives of complex signals, applied after local temporal filtering; and so on.
在那种情形下，空间滤波可被用于对于特定帧的扫描数据数组，然而时间滤波可被用于在多个连续帧上的特定体元或相邻体元的组。In that case, spatial filtering may be applied to the array of scan data for a particular frame, whereas temporal filtering may be applied to a particular voxel or group of adjacent voxels over multiple consecutive frames.
在一些实施方式中，当选择和/或使用复合函数参数时，可以使用以下假设中的一个或多个：In some embodiments, one or more of the following assumptions may be used when selecting and/or using composite function parameters:
(a)局部相位差和/或幅度差和/或幅度比说明了信号源的角方向。根据定义，无杂波信号源于靠近主接收波束的主瓣的角方向。例如，当采用其主瓣指向同样的空间角度的主接收波束和辅助接收波束时，人们将会期望它用于在主瓣中心的反射器，其根据定义产生无杂波信号：(a) The local phase difference and/or amplitude difference and/or amplitude ratio describe the angular direction of the signal source. By definition, the clutter-free signal originates from the angular orientation of the main lobe close to the main receive beam. For example, when using the main and auxiliary receive beams with their main lobes pointing at the same spatial angle, one would expect it for a reflector at the center of the main lobe, which by definition produces a clutter-free signal:
(i)主接收波束和辅助接收波束之间的局部相位差将接近0；(i) The local phase difference between the main receiving beam and the auxiliary receiving beam will be close to 0;
(ii)主接收波束和辅助接收波束之间的局部幅度比，其中辅助接收波束的信号被归一化使得它的最大增益匹配主接收波束的最大增益，将接近1.0；以及(ii) the local amplitude ratio between the main receive beam and the auxiliary receive beam, where the signal of the auxiliary receive beam is normalized such that its maximum gain matches that of the main receive beam, will be close to 1.0; and
(iii)主接收波束和辅助接收波束之间的局部幅度差，其中辅助接收波束的信号被归一化使得它的最大增益匹配主接收波束的最大增益，将接近0。(iii) The local amplitude difference between the main receive beam and the auxiliary receive beam, where the signal of the auxiliary receive beam is normalized so that its maximum gain matches that of the main receive beam, will approach zero.
这些假设可以源于波束形成等式，例如等式(1)和等式(2)。图2中示出根据作为方位角的函数的增益而定义的两个示例性波束方向图51和52的示意图示。在图3A中的曲线图55中能看到，为作为方位角的函数的点状反射器定义的主接收波束和辅助接收波束之间产生的幅度比。在图3B中的曲线图56中能看到，为作为方位角的函数的点状反射器定义的主接收波束和辅助接收波束之间产生的相位差。注意，图3B中的方位角刻度匹配图3A的刻度，但不匹配图2的刻度。These assumptions can be derived from beamforming equations such as equation (1) and equation (2). A schematic illustration of two exemplary beam patterns 51 and 52 defined in terms of gain as a function of azimuth angle is shown in FIG. 2 . The resulting amplitude ratio between the main receive beam and the auxiliary receive beam defined for a point reflector as a function of azimuth angle can be seen in graph 55 in FIG. 3A. The resulting phase difference between the main receive beam and the auxiliary receive beam defined for a point reflector as a function of azimuth angle can be seen in graph 56 in FIG. 3B. Note that the azimuth scale in Figure 3B matches that of Figure 3A, but not that of Figure 2.
相似地，当采用其主瓣不指向相同的空间角的主接收波束和辅助接收波束时，人们将期望它用于在主瓣中心的反射器，其根据定义产生无杂波信号：Similarly, when using the main and auxiliary receive beams whose main lobes are not pointing at the same spatial angle, one would expect it for a reflector at the center of the main lobe, which by definition produces a clutter-free signal:
(i)主接收波束和辅助接收波束之间的局部相位差将接近常数，其可以基于主接收波束和辅助接收波束的主瓣的空间角来计算；以及(i) the local phase difference between the main receive beam and the auxiliary receive beam will be close to a constant, which can be calculated based on the spatial angle of the main lobes of the main receive beam and the auxiliary receive beam; and
(ii)主接收波束和辅助接收波束之间的局部幅度比，其中辅助接收波束的信号被归一化使得其最大增益匹配主接收波束的最大增益，将接近常数，其可以基于主接收波束和辅助接收波束的主瓣的空间角来计算。(ii) The local amplitude ratio between the main receive beam and the auxiliary receive beam, where the signal of the auxiliary receive beam is normalized such that its maximum gain matches that of the main receive beam, will approach a constant, which can be based on the main receive beam and The spatial angle of the main lobe of the auxiliary receive beam is calculated.
应注意的是，任何局部相位差和/或幅度差和/或幅度比都可以对应于信号源的多于一个的角方向。例如，当采用其主瓣指向相同的空间角的主接收波束和辅助接收波束时，其中主接收波束和辅助接收波束都具有关于在它们主瓣的中心对称的波束方向图(例如，圆锥形的波束方向图)，在相对于换能器阵列的相位中心的任意给定范围中，人们将期望局部相位差和幅度差和幅度比沿着同心圆曲线相等，其中心落在主瓣的中心线上，其中曲线位于相对于换能器阵列的相位中心的相对应的范围内。源于此规则的一些偏差可能由介质中的物理效应导致，例如，影响扫描区域内的实际波束方向图的衍射。It should be noted that any local phase difference and/or amplitude difference and/or amplitude ratio may correspond to more than one angular direction of the signal source. For example, when using a main receive beam and an auxiliary receive beam with their main lobes pointing at the same spatial angle, wherein both the main receive beam and the auxiliary receive beam have beam patterns that are symmetrical about the centers of their main lobes (e.g., conical beam pattern), in any given range relative to the phase center of the transducer array, one would expect the local phase and magnitude differences and magnitude ratios to be equal along concentric circular curves whose centers fall on the centerline of the main lobe where the curves lie in the corresponding range relative to the phase center of the transducer array. Some deviations from this rule may be caused by physical effects in the medium, eg diffraction affecting the actual beam pattern within the scanned area.
通过采用多于一个的以下参数：局部相位差、局部幅度差和局部幅度比，人们可降低关于信号源的角方向的信息的模糊度。通过使用来自多个用于给定主接收波束的辅助接收波束的信息，所述模糊度将进一步被降低。By employing more than one of the following parameters: local phase difference, local amplitude difference and local amplitude ratio, one can reduce the ambiguity of the information about the angular direction of the signal source. By using information from multiple auxiliary receive beams for a given main receive beam, the ambiguity will be further reduced.
(b)对于无杂波信号，其源于根据定义与主接收波束的主瓣的中心近似相对应的角方向，人们将期望信号水平和/或它的幅度作为空间位置的函数，以便在主和辅助接收波束中以类似的方式改变，假设主和辅助接收波束的主瓣充分重叠，并且假设用于辅助波束的数据被归一化使得辅助波束的最大增益将匹配相对应的主波束的最大增益。在这种情况下，作为空间位置函数的信号水平可以被定义，例如，通过局部信号水平、局部空间导数和/或局部归一化空间导数定义，其中局部归一化的空间导数定义为局部空间导数除以局部信号。(b) For a clutter-free signal originating from an angular direction which by definition corresponds approximately to the center of the main lobe of the main receive beam, one takes the desired signal level and/or its amplitude as a function of spatial position such that in the main is changed in a similar manner as in the auxiliary receive beam, assuming that the main lobes of the main and auxiliary receive beams overlap sufficiently, and assuming that the data for the auxiliary beams are normalized so that the maximum gain of the auxiliary beam will match the corresponding maximum gain of the main beam gain. In this case, signal levels as a function of spatial position can be defined, for example, by local signal levels, local spatial derivatives and/or locally normalized spatial derivatives, where the locally normalized spatial derivatives are defined as the local spatial Derivative divided by local signal.
应注意的是，各种接收波束的横向分辨率由于相应的波束方向图中的差异可能是不同的，并且各种接收波束的纵向分辨率由于在发射和/或接收时不相似的波形也可能是不同的。因而，在一些实施方式中，在比较不同接收波束之间作为空间位置函数的信号水平和/或它的幅度之前，空间滤波可以应用到一个或多个数据集，其每个对应于波束方向图和/或波形的特定类型，以便确保在比较的波束中的局部信号的横向和/或纵向分辨率将匹配。当采用多个常用配置扫描数据数组时，其每个对应于具有特定横向和/或轴向分辨率的接收波束，在比较不同接收波束之间作为空间位置函数的信号水平和/或它的幅度之前，空间滤波可以应用到一个或多个常用配置扫描数据数组。例如，当采用窄的主接收波束和宽的辅助接收波束时，其中对于每个主接收波束存在其主瓣指向相同方向的相对应的辅助波束，人们可以将空间低通滤波器应用到使用主接收波束获得的常用配置扫描数据数组。It should be noted that the lateral resolution of the various receive beams may be different due to differences in the corresponding beam patterns, and the longitudinal resolution of the various receive beams may also be due to dissimilar waveforms when transmitting and/or receiving is different. Thus, in some embodiments, spatial filtering may be applied to one or more data sets, each corresponding to a beam pattern, prior to comparing the signal level and/or its magnitude as a function of spatial position between different receive beams and/or specific types of waveforms in order to ensure that the lateral and/or vertical resolutions of the local signals in the compared beams will match. When scanning an array of data with multiple common configurations, each corresponding to a receive beam with a particular lateral and/or axial resolution, comparing the signal level and/or its magnitude as a function of spatial position between the different receive beams Previously, spatial filtering could be applied to one or more commonly configured scan data arrays. For example, when using a narrow main receive beam and a wide auxiliary receive beam, where for each main receive beam there is a corresponding auxiliary beam with its main lobe pointing in the same direction, one can apply a spatial low-pass filter to the An array of commonly configured scan data acquired by the receive beam.
(c)不同目标区域可以具有不同动态模型。例如，在超声心动图中，常常导致杂波反射的胸腔以比感兴趣区域内的心肌慢得多的速率运动。各种时间滤波器可以应用以便估计对于具有预定动态特性的组织的信号水平。在本文中描述的杂波抑制处理可以应用到特定频带。附加地或可选择地，人们可以将本文描述的杂波抑制处理分别应用到若干时间滤波器的输出，然后复合结果以便获得最终数据集。(c) Different target regions may have different dynamic models. For example, in echocardiography, the chest cavity, often causing clutter reflections, moves at a much slower rate than the myocardium in the region of interest. Various temporal filters can be applied in order to estimate the signal level for tissue with predetermined dynamic properties. The clutter suppression processing described herein can be applied to specific frequency bands. Additionally or alternatively, one can apply the clutter suppression process described herein to the outputs of several temporal filters separately, and then compound the results in order to obtain the final data set.
复合函数参数可以通过以下方式中的一种或多种(“复合函数实现方式”)来导出和/或使用：Composite function parameters may be exported and/or used in one or more of the following ways ("composite function implementations"):
(a)分别计算进入扫描数据数组的每个记录和每一帧并相应地应用。(a) Calculate each record and each frame into the array of scan data separately and apply accordingly.
(b)针对帧的预定子集进行计算，并且在每一帧中，针对进入扫描数据数组的每个记录或相邻记录的组进行计算，且应用到所有帧，其中应用到特定帧中的参数可以是针对最近的帧索引进行计算的那些参数，或可替代地，是针对等于或低于当前帧索引的最近帧索引进行计算的那些参数。空间内插和/或时间内插也可以被采用以便导出在给定帧中应用的参数。(b) Computed for a predetermined subset of frames, and within each frame, for each record or group of contiguous records entering the scan data array, and applied to all frames, where applied to the The parameters may be those calculated for the most recent frame index, or alternatively, those calculated for the most recent frame index equal to or lower than the current frame index. Spatial and/or temporal interpolation may also be employed in order to derive the parameters applied in a given frame.
(c)针对特定帧进行计算，但是针对进入扫描数据数组的每个记录或相邻记录的组进行计算，且应用到所有帧。(c) Computed for a specific frame, but computed for each record or group of contiguous records entering the scan data array, and applied to all frames.
(d)针对所有帧进行计算，但是针对进入扫描数据数组的记录的特定集合进行计算，且应用到进入扫描数据数组的所有记录，其中在每一帧中，用于每个体元的参数值由内插和/或外插导出，例如，采用最近邻内插。(d) Computed for all frames, but for a specific set of records entering the scan data array, and applied to all records entering the scan data array, where in each frame the parameter value for each voxel is given by Interpolation and/or extrapolation are derived, for example, using nearest neighbor interpolation.
(e)针对帧的预定子集进行计算，其长度也可以等于1，并且针对进入扫描数据数组的记录的特定集合进行计算，其中在每一帧中，参数值是取决于针对最近帧索引进行计算的那些参数值，取决于针对等于或低于当前帧索引的最近帧索引进行计算的那些参数值，或者取决于时间上的内插和外插，并且其中空间内插和/或外插被用于进入扫描数据数组的每个记录。内插和/或外插可使用本领域已知的任何方法。(e) Computed for a predetermined subset of frames, whose length may also be equal to 1, and for a specific set of records entering the scandata array, where in each frame the parameter value is determined by The values of those parameters computed depend on those computed for the nearest frame index equal to or lower than the current frame index, or on interpolation and extrapolation in time, and where spatial interpolation and/or extrapolation are for each record that goes into the scanned data array. Interpolation and/or extrapolation can use any method known in the art.
方法(b)-(e)被设计为减少计算的时间和/或存储复杂度。Methods (b)-(e) are designed to reduce computational time and/or storage complexity.
广义度量generalized measure
在某些实施方式中，复合函数参数的一个或多个可以定义为遵守以下选项中的至少一项：In some implementations, one or more of the composite function parameters may be defined to obey at least one of the following options:
(a)表明对应体元基本上仅被杂波效应影响(即，几乎它所有的接收能量都源于杂波效应)的概率，如使用某种物理假设和/或生理上的假设而得到。(a) Indicates the probability that the corresponding voxel is substantially only affected by clutter effects (ie, nearly all of its received energy is due to clutter effects), as obtained using certain physical and/or physiological assumptions.
(b)表明对应体元基本上不被杂波效应影响的概率，如使用某种物理上和/或生理上的假设而得到。注意，对于每个特定体元，在(a)和(b)中的概率的和总是1.0。(b) Indicates the probability that the corresponding voxel is substantially unaffected by clutter effects, eg using certain physical and/or physiological assumptions. Note that the sum of the probabilities in (a) and (b) is always 1.0 for each particular voxel.
(c)表明对应体元内的源于杂波效应的接收能量的百分比。(c) Indicates the percentage of received energy due to clutter effects within the corresponding voxel.
(d)如果对应体元不被杂波效应显著影响，则设置为某个常数，例如，0.0，否则设定为不同的常数，例如1.0。(d) If the corresponding voxel is not significantly affected by the clutter effect, set it to a certain constant, such as 0.0, otherwise set it to a different constant, such as 1.0.
这种复合函数参数在本文被称为“广义度量”。它们可以采用本领域已知的任何方法来计算。在一些实施方式中，例如，在选项(d)中，分割技术可以应用到以下至少一个(一般被称作“分割技术参数”)：(a)在接收波束的一个或多个中的局部接收信号；以及(b)复合函数参数的一个或多个的局部值。Such composite function parameters are referred to herein as "generalized metrics". They can be calculated using any method known in the art. In some embodiments, for example, in option (d), the segmentation technique may be applied to at least one of the following (generally referred to as "segmentation technique parameters"): (a) localized reception in one or more of the receive beams signals; and (b) local values of one or more of the composite function parameters.
例如，经典边缘检测(例如，参见于2004年4月6日公告的Geiser和Wilson的名为“Autonomous boundary detection system for echocardiographic image”的美国专利6,716,175)，或者径向搜索技术(例如，参见Han等人的在1995年10月10日公告的名为“Method for automatic contour extraction of a cardiac image”的美国专利5,457,754)，可被用于分割的目的。这些技术可能会结合旨在针对性能增强的基于认知的算法，其可在后处理阶段引入或者作为与初始边界估计结合的代价函数。对于可行的分割方法的另一个实例是解决限制优化问题，其基于主动轮廓线模型(例如，参见Mishra等人在2003年的Image and Vision Computing的第21卷的第967—976页的论文“A GA based approachfor boundary detection of left ventricle with echocardiographic imagesequence”，其通过引用结合于此)。附加地或选择性地，人们可将预定阀值应用于一个或多个分割技术参数，以便得到在受杂波效应影响严重的体元与不受杂波效应影响的体元之间的初始划分。在一些实施方式中，迭代区域增长技术可随后被运用，其中用于一个或多个分割技术参数的预定阀值可以在连续迭代中改变。For example, classical edge detection (see, for example, U.S. Patent 6,716,175 to Geiser and Wilson, entitled "Autonomous boundary detection system for echocardiographic image," issued April 6, 2004), or radial search techniques (see, for example, Han et al. U.S. Patent 5,457,754 issued October 10, 1995, entitled "Method for automatic contour extraction of a cardiac image", can be used for segmentation purposes. These techniques may incorporate cognitive-based algorithms aimed at performance enhancement, which can be introduced in the post-processing stage or as a cost function combined with the initial boundary estimation. Another example for a feasible segmentation method is the solution of constrained optimization problems, which are based on active contour models (see, for example, the paper "A GA based approach for boundary detection of left ventricle with echocardiographic image sequence", which is hereby incorporated by reference). Additionally or alternatively, one can apply predetermined thresholds to one or more segmentation technique parameters in order to obtain an initial division between voxels heavily affected by clutter effects and voxels not affected by clutter effects . In some embodiments, an iterative region growing technique may then be employed, wherein predetermined thresholds for one or more segmentation technique parameters may be changed in successive iterations.
在其他实施方式中，广义度量可被定义为值为从0.0至1.0范围的实数，其中值0.0被分配给基本上不受杂波效应影响的体元，而值1.0被分配给其中基本上所有测量信号都源于杂波效应的体元(“归一化的广义度量”)。在紧接的上文中的选项(a)-(b)中，归一化的广义度量可视为对应体元基本上只受杂波效应影响的估计概率；在紧接的上文中的选项(c)中，归一化的广义度量可视为所估计的对应体元内接收的源自杂波效应的能量的百分比。这样的定义简化了信号校准，尤其当复合函数是线性的时候。在那种情况下，词语“信号校准”指的是确保由于杂波抑制处理使得完全不受杂波效应影响的体元中的信号能量尽可能小地变化，然而在其唯一的能量源为杂波的体元中的信号能量将因杂波抑制处理而尽可能多地被抑制。In other embodiments, the generalized metric can be defined as a real number with values ranging from 0.0 to 1.0, where a value of 0.0 is assigned to voxels that are substantially unaffected by clutter effects, and a value of 1.0 is assigned to substantially all voxels within them. The measurement signals are all derived from the voxels of the clutter effect ("normalized generalized measure"). In the options (a)-(b) immediately above, the normalized generalized measure can be regarded as the estimated probability that the corresponding voxel is basically only affected by the clutter effect; in the option ( In c), the normalized generalized measure can be considered as the estimated percentage of energy received within the corresponding voxel originating from clutter effects. Such a definition simplifies signal calibration, especially when the composite function is linear. In that case, the term "signal calibration" refers to ensuring that the signal energy in a voxel that is completely immune to clutter effects changes as little as possible due to the clutter suppression process, while its only source of energy is the clutter The signal energy in the voxel of the wave will be suppressed as much as possible due to the clutter suppression process.
在某些实施方式中，对于帧的集合中的体元的集合的广义度量可以采用以下四步过程来获得：In some embodiments, a generalized metric for a collection of voxels in a collection of frames can be obtained using the following four-step process:
(a)选择采用一个或多个复合函数参数(“复合函数参数设置”)。用于复合函数参数设置的一些实例：(a) Option to take one or more composite function parameters ("composite function parameter settings"). Some examples of parameter settings for composite functions:
(i)参数#1：两个不同接收波束(主和辅助波束)之间的局部幅度比；(i) Parameter #1: local amplitude ratio between two different receive beams (main and auxiliary beams);
参数#2：两个不同接收波束之间的局部相位差；Parameter #2: Local phase difference between two different receive beams;
(ii)参数#1：两个不同接收波束之间沿着第一空间轴(例如，X轴)的空间幅度导数的局部比；(ii) Parameter #1: the local ratio of the spatial amplitude derivative along the first spatial axis (e.g., X-axis) between two different receive beams;
参数#2：两个不同接收波束之间沿着第二空间轴(例如，Y轴)的空间幅度导数的局部比；Parameter #2: The local ratio of the spatial amplitude derivative along the second spatial axis (eg, the Y axis) between two different receive beams;
(iii)参数#1：两个不同接收波束之间沿着第一空间轴(例如，X轴)的归一化空间幅度导数的局部比；(iii) Parameter #1: the local ratio of the normalized spatial amplitude derivative along the first spatial axis (e.g., X-axis) between two different receive beams;
参数#2：两个不同接收波束之间沿着第二空间轴(例如，Y轴)的归一化空间幅度导数的局部比；Parameter #2: The local ratio of the normalized spatial amplitude derivative along a second spatial axis (eg, Y axis) between two different receive beams;
其中归一化的局部信号导数定义为局部信号导数除以局部信号；where the normalized local signal derivative is defined as the local signal derivative divided by the local signal;
(ⅳ)参数#1：两个不同接收波束之间的局部幅度空间导数的比，其中空间导数采用“拉普拉斯滤波器”来计算；(iv) Parameter #1: the ratio of the spatial derivative of the local amplitude between two different receive beams, where the spatial derivative is computed using a "Laplace filter";
参数#2：两个不同波束之间的局部幅度比；Parameter #2: local amplitude ratio between two different beams;
(v)参数#1：两个不同接收波束之间局部归一化的幅度空间导数的比，其中归一化的空间导数通过“拉普拉斯滤波器”(适用于局部信号幅度)的局部输出除以局部信号幅度来计算；(v) Parameter #1: The ratio of the locally normalized spatial derivatives of amplitudes between two different receive beams, where the normalized spatial derivatives pass through the local The output is calculated by dividing by the local signal amplitude;
参数#2：两个不同接收波束之间的局部幅度比；以及Parameter #2: the local amplitude ratio between two different receive beams; and
(vi)参数#1：两个不同接收波束之间的归一化的幅度范围的比，其中归一化的幅度范围被定义为在局部区域里最大与最小幅度之间的差(有或没有异常排除)除以在所述区域内的平均幅度，其中局部区域被定义使得其宽度大于其高度；(vi) Parameter #1: The ratio of the normalized amplitude range between two different receive beams, where the normalized amplitude range is defined as the difference between the maximum and minimum amplitude in a local area (with or without anomaly exclusion) divided by the average magnitude in the region, where a local region is defined such that its width is greater than its height;
参数#2：两个不同波束之间的归一化的幅度范围的比，其中局部区域被定义使得其高度大于其宽度。Parameter #2: Ratio of normalized amplitude range between two different beams, where the local area is defined such that its height is greater than its width.
(b)定义用于以下至少一个的模型：(b) Define a model for at least one of the following:
(i)体元基本上仅被杂波效应影响的概率(或其简单函数，例如，概率密度函数)；(i) the probability (or a simple function thereof, e.g., a probability density function) that a voxel is substantially only affected by clutter effects;
(ii)体元基本上不被杂波效应影响的概率(或其简单函数，例如，概率密度函数)；以及(ii) the probability (or a simple function thereof, e.g., a probability density function) that the voxel is substantially unaffected by clutter effects; and
(iii)对应体元内的源于杂波效应的能量的百分比(或其简单函数)；作为复合函数参数集合值或用于复合函数参数集合的子集的值的函数(“复合模型”)。在一些例子中，使用复合函数参数集合的一个或多个子集(“复合函数参数子集”)，可以运用多于一个的复合模型。在这种情况下中，词语“子集”也包括全部集合的选项。(iii) Percentage (or a simple function thereof) of energy within the corresponding voxel originating from clutter effects; as a function of the value of the set of composite function parameters or values for a subset of the set of composite function parameters ("composite model") . In some examples, more than one composite model may be employed using one or more subsets of the set of composite function parameters ("composite function parameter subsets"). In this case, the term "subset" also includes options for the entire set.
(c)对于每个相关体元和/或其紧邻计算复合函数参数。在这种情况中，紧邻可以定义为在空间上和/或时间上横跨扫描数据数组。(c) Computation of composite function parameters for each relevant voxel and/or its immediate neighbors. In this case, immediate contiguity may be defined as spatially and/or temporally spanning the scan data array.
(d)对于每个相关体元，采用一个或多个复合模型来估计以下至少一个(或其简单函数)：(d) For each relevant voxel, employ one or more composite models to estimate at least one of the following (or a simple function thereof):
(i)对于其基本上仅被杂波效应影响的概率；(i) for the probability that it is substantially only affected by clutter effects;
(ii)对于其基本上没有被杂波效应影响的概率；以及(ii) the probability for it to be substantially unaffected by clutter effects; and
(iii)对应体元内源于杂波效应的能量的百分比。(iii) Percentage of energy in the corresponding voxel due to clutter effects.
对于每个复合模型，每个相关体元的结果可以被用作对于该体元的广义度量或归一化广义度量。因此可以为每个体元定义多个广义度量。For each composite model, the result for each associated voxel can be used as a generalized metric or a normalized generalized metric for that voxel. Thus multiple generalized metrics can be defined for each voxel.
复合模型可以采用本领域中已知的任何方法来定义。附加地或选择性地，它可以通过以下方法中的一个或多个来定义：Composite models can be defined using any method known in the art. Additionally or alternatively, it can be defined by one or more of the following methods:
(a)预定的模型(“预定的复合模型”)，其可以从理论上确定或从实验中得出。这种模型可以取决于可应用的发射和/或接收波束的波束方向图。例如，可以考虑每个这种波束的一个或多个轴上的波束宽度。它可以独立于空间位置和时间，但其可能也取决于空间位置和/或时间。例如，人们可以利用如下事实，在远场中，标称发射波束宽度根据与探头的距离而变化，在焦距处达到最小值。另一个实例将采用用于不同波束方向图的不同模型，如果多个波束方向图类型可利用的话。(a) A predetermined model ("predetermined composite model"), which may be determined theoretically or derived from experiments. Such a model may depend on the beam pattern of the applicable transmit and/or receive beams. For example, the beamwidth in one or more axes of each such beam may be considered. It may be independent of spatial location and time, but it may also depend on spatial location and/or time. For example, one can take advantage of the fact that, in the far field, the nominal transmit beamwidth varies with distance from the probe, reaching a minimum at the focal length. Another example would be to use different models for different beam patterns, if multiple beam pattern types are available.
(b)简化自适应模型(“简化自适应复合模型”)，取决于关于作为可应用的复合函数参数子集的函数(“复合模型PDF”)的体元基本上被(或基本上没被)杂波效应影响的概率密度函数(PDF)形状的假设。例如，可以采用一维或多维高斯函数，其中函数的维数应该对应于在复合函数参数子集中的参数的个数。(b) Reduced Adaptive Model ("Reduced Adaptive Composite Model"), depending on the voxel being substantially (or not substantially) ) assumptions about the shape of the probability density function (PDF) influenced by clutter effects. For example, one-dimensional or multi-dimensional Gaussian functions can be used, where the dimensionality of the function should correspond to the number of parameters in the composite function parameter subset.
自由参数(在高斯函数的实例中，是期望值和协方差矩阵的矢量)可以通过在合适的接收波束中的一些或所有的相关体元上的复合函数参数集合的值的统计分析来确定。在一些实施方式中，可以同时采用所有帧中的所有相关体元。在其它的实施方式中，可以分别为每一帧和/或每组体元实施计算。在这种情况中，体元组可以在一个或多个扫描数据数组轴中被分开(例如，相对于探头的宽侧的不同距离和/或不同角区域)。在其他的实施方式中，可以对帧的子集和/或体元的子集执行计算，其中空间和/或时间内插和/或外插可以用来估计对于任何体元的复合模型PDF。内插和/或外插可以使用本领域中已知的任何方法。The free parameters (in the example of a Gaussian function, the expected value and the vector of the covariance matrix) can be determined by statistical analysis of the values of the composite function parameter set at some or all of the relevant voxels in the appropriate receive beam. In some embodiments, all relevant voxels in all frames may be employed simultaneously. In other embodiments, calculations may be performed separately for each frame and/or each group of voxels. In this case, groups of voxels may be separated in one or more scan data array axes (eg, different distances and/or different angular regions relative to the broadside of the probe). In other embodiments, computations may be performed on a subset of frames and/or a subset of voxels, where spatial and/or temporal interpolation and/or extrapolation may be used to estimate the composite model PDF for any voxels. Interpolation and/or extrapolation may use any method known in the art.
(c)自适应模型(“自适应复合模型”)，其中的复合模型PDF，即，作为可应用的复合函数参数子集的函数的体元基本上被(或基本上没被)杂波效应影响的PDF被直接计算，而不需关于PDF形状的任何先验假设。复合模型PDF可以采用本领域中已知的任何方法来计算。例如，可以计算所有相关体元的可应用的复合函数参数子集的值的一维或多维柱状图，其中柱状图的维数应该对应于复合函数参数子集中的参数个数。为了遵循PDF的定义，柱状图应该被归一化使得其所有元素的和等于1.0。如果人们假设：(c) Adaptive models ("adaptive composite models") in which the composite model PDF, i.e., voxels as a function of a subset of applicable composite function parameters is substantially (or substantially free) of clutter effects The PDF of the influence is directly computed without any a priori assumptions about the shape of the PDF. The composite model PDF can be calculated using any method known in the art. For example, a one-dimensional or multi-dimensional histogram of the values of the applicable composite function parameter subset for all relevant voxels can be calculated, wherein the dimension of the histogram should correspond to the number of parameters in the composite function parameter subset. To follow the definition of PDF, a histogram should be normalized such that the sum of all its elements equals 1.0. If one assumes:
(i)在大多数的体元中，测量信号的主要来源位于接近双向波束方向图的主瓣中心的空间角(这是因为波束方向图提供更高增益给这个角区域，而大多数软组织近似具有相同的反射特性)，并且因而几乎没有杂波的体元比被杂波强烈影响的体元更普遍；以及(i) In most voxels, the main source of the measured signal is located at a spatial angle close to the center of the main lobe of the bidirectional beam pattern (this is because the beam pattern provides higher gain to this angular region, whereas most soft tissue approximations have the same reflection properties), and thus voxels with little clutter are more prevalent than voxels strongly affected by clutter; and
(ii)复合函数参数子集提供关于局部杂波水平和/或测量信号主要来源的角方向的信息。(ii) A subset of composite function parameters provide information about the local clutter level and/or the angular direction of the main source of the measurement signal.
结果可以用作对于基本上不被杂波效应影响的体元的PDF的估计。如果细看每个柱状图元素，并且用1减去原始值来代替它的值，结果可以用作对于基本上被杂波效应影响的体元的PDF的估计。在计算柱状图之前，人们可以在它的一个或多个轴中采用异常排除，即，对于在复合函数参数子集中的一个或多个参数采用异常排除，因而限制柱状图的动态范围。在一些实施方式中，在每个柱状图轴中使用的柱形可以是同一宽度。在其它实施方式中，在一个或多个柱状图轴中使用的柱形可以是自适应的宽度，其中更窄的柱形宽度被分配给具有更高PDF值的区域。在另外的其他实施方式中，可以使用Vornoni图表代替柱状图。The result can be used as an estimate of the PDF for voxels not substantially affected by clutter effects. If one looks at each histogram element and replaces its value by 1 minus the original value, the result can be used as an estimate of the PDF for voxels substantially affected by clutter effects. Before computing the histogram, one can employ outlier exclusion in one or more of its axes, ie for one or more parameters in a subset of the composite function parameters, thus limiting the dynamic range of the histogram. In some implementations, the bars used in each histogram axis may be of the same width. In other embodiments, the bars used in one or more of the histogram axes may be of adaptive width, where narrower bar widths are assigned to regions with higher PDF values. In yet other embodiments, Vornoni charts may be used instead of histograms.
在某些实施方式中，可以同时采用所有帧中的所有相关体元来计算复合模型PDF。在其它实施方式中，可以为每一帧和/或每组体元分别计算复合模型PDF。在这种情况下，体元组可以在一个或多个扫描数据数组轴中被分开(例如，相对于探头宽侧的不同地带和/或不同角区域)。在其他的实施方式中，可以为帧的子集和/或体元的子集计算复合模型PDF，其中空间和/或时间的内插和/或外插可以用来估计对于任何体元的复合模型PDF。内插和/或外插可以使用本领域中已知的任何方法。例如，人们可以计算对于Nf个连续帧的每个集合中的第一帧的复合模型PDF，并且对于所有Nf个连续帧采用该复合模型PDF。In some embodiments, the composite model PDF can be calculated using all relevant voxels in all frames simultaneously. In other embodiments, the composite model PDF may be calculated separately for each frame and/or each group of voxels. In this case, groups of voxels may be separated in one or more scan data array axes (eg, different zones and/or different angular regions relative to the broadside of the probe). In other embodiments, a composite model PDF can be computed for a subset of frames and/or a subset of voxels, where spatial and/or temporal interpolation and/or extrapolation can be used to estimate the composite Model PDF. Interpolation and/or extrapolation may use any method known in the art. For example, one can compute the composite model PDF for the first frame in each set of Nf consecutive frames, and employ this composite model PDF for all Nf consecutive frames.
在三个模型中，预定的复合模型预期是计算效率最高的，但它不能考虑介质特有的副产物(artifact)，例如，局部衰减、散射、折射和衍射效应，其可以沿着波束产生，改变它的有效波束方向图。自适应复合模型是最准确的，然而它可以是更密集计算的。为了减少时间复杂度，人们可以采用上面定义的复合函数实现方式。Among the three models, the predetermined composite model is expected to be the most computationally efficient, but it cannot account for medium-specific artifacts, such as local attenuation, scattering, refraction, and diffraction effects, which can occur along the beam, changing Its effective beam pattern. The adaptive composite model is the most accurate, however it can be more computationally intensive. In order to reduce the time complexity, one can adopt the composite function implementation defined above.
在其他的实施方式中，以上描述的复合模型的稍微变化可以允许其产生归一化的广义度量值。如以上所定义，归一化的广义度量是被定义为其值范围在0.0到1.0之间的实数的广义度量，其中值0.0被分配给基本上不被杂波效应影响的体元，值1.0被分配给其中基本上所有测量信号都源于杂波效应的体元。因此，对于预定的复合模型，通过正确地校准预定模型，人们能够获得归一化的广义度量而不是非归一化的广义度量。对于简化的多个自适应复合模型或一个自适应复合模型，归一化的广义度量可以通过使用对于基本上仅被杂波效应影响的体元的概率(作为可应用的复合函数参数子集的函数)获得(其取代了复合模型PDF)，而不是获得非归一化的广义度量。In other embodiments, slight variations of the composite model described above may allow it to produce normalized generalized metrics. As defined above, a normalized generalized metric is a generalized metric defined as a real number whose value ranges between 0.0 and 1.0, where a value of 0.0 is assigned to voxels substantially unaffected by clutter effects and a value of 1.0 are assigned to voxels in which substantially all of the measured signal originates from clutter effects. Thus, for a predetermined composite model, by properly calibrating the predetermined model, one is able to obtain normalized generalized measures rather than unnormalized generalized measures. For simplified multiple adaptive composite models or an adaptive composite model, a generalized measure of normalization can be obtained by using the probability for voxels that are substantially only affected by clutter effects (as the subset of applicable composite function parameters function) (which replaces the composite model PDF) instead of obtaining an unnormalized generalized metric.
对于基本上仅被杂波效应影响的体元的概率(“复合模型概率函数”)可以源于如下的复合模型PDF：The probability for voxels that are substantially only affected by clutter effects ("composite model probability function") can be derived from the composite model PDF as follows:
令{pn}为复合函数参数子集，fPDF({pn})为复合模型PDF，P({pn})为复合模型概率函数。Let {pn } be the composite function parameter subset, fPDF ({pn }) be the composite model PDF, and P({pn }) be the composite model probability function.
对于关于体元基本上仅被杂波效应影响的PDF的复合模型PDF，对于给定{pn}的P({pn})可以通过模型中fPDF({pn})的所有值的总和来估计，其低于或等于对于特定{pn}的fPDF的值。在fPDF({pn})是非离散的例子中，应该采用积分而不是总和。注意，根据定义PDF被归一化使得它在整个模型上的总和(或积分)是1.0，使得复合模型概率函数的范围如所期望的从0.0到1.0。For a compound model PDF with respect to PDFs whose voxels are substantially only affected by clutter effects, P({pn }) for a given {pn } can be passed for all values of fPDF ({pn }) in the model is estimated as a sum that is lower than or equal to the value of fPDF for a particular {pn }. In cases where fPDF ({pn }) is non-discrete, integrals should be used instead of sums. Note that the PDF is by definition normalized such that it sums (or integrates) over the entire model to 1.0, so that the composite model probability function ranges from 0.0 to 1.0 as desired.
对于关于体元基本上不被杂波效应影响的PDF的复合模型PDF，对于给定{pn}的P({pn})可以通过模型中fPDF({pn})的所有值的总和来估计，其高于或等于对于特定{pn}的fPDF的值。在fPDF({pn})是非离散的例子中，应该采用积分而不是总和。For a composite model PDF about PDFs whose voxels are substantially unaffected by clutter effects, P({pn }) for a given {pn } can be passed for all values of fPDF ({pn }) in the model is estimated to be higher than or equal to the value of fPDF for a particular {pn }. In cases where fPDF ({pn }) is non-discrete, integrals should be used instead of sums.
波束方向图测量Beam pattern measurements
在一些实施方式中，复合模型PDF和/或复合模型概率函数可以用于估计在给定介质内的局部波束方向图，和/或该波束方向图的特征，例如一个或多个轴上的主瓣的宽度。例如，如果发射波束方向图对于主接收波束和它关联的辅助接收波束是共同的，则可以估计接收波束方向图和/或接收波束方向图的特征。对于该目的应该定义合适的模型，其可以从理论上确定和/或从实验中获得(“波束方向图测量模型”)。In some embodiments, a composite model PDF and/or a composite model probability function can be used to estimate a local beam pattern within a given medium, and/or characteristics of the beam pattern, such as principal The width of the flap. For example, the receive beam pattern and/or the characteristics of the receive beam pattern may be estimated if the transmit beam pattern is common to the main receive beam and its associated auxiliary receive beam. A suitable model should be defined for this purpose, which can be determined theoretically and/or obtained from experiments (“beam pattern measurement model”).
例如，当采用单个发射波束、单个主接收波束和单个辅助接收波束时，其中所有波束的方位角波束宽度是相同的，但主接收波束的仰角波束宽度低于发射波束和辅助接收波束的仰角波束宽度，复合模型PDF和/或复合模型概率函数被期望在接收时包含关于仰角波束宽度的信息。相似的，当采用单个发射波束、单个主接收波束和两个辅助接收波束(一个仅在方位角上比主接收波束宽，而另一个仅在仰角上)时，人们可以分别采用每个辅助接收波束以便推断出关于在接收时沿着可应用轴的波束宽度的信息。For example, when using a single transmit beam, a single main receive beam, and a single auxiliary receive beam, where the azimuth beamwidth of all beams is the same, but the elevation beamwidth of the main receive beam is lower than that of the transmit and auxiliary receive beams Width, Composite Model PDF and/or Composite Model Probability Function are expected to contain information about the elevation beamwidth when received. Similarly, when using a single transmit beam, a single main receive beam, and two auxiliary receive beams (one wider than the main receive beam only in azimuth and the other only in elevation), one can use each auxiliary receive beam separately. beam in order to infer information about the beamwidth along the applicable axis at reception.
在其他的实施方式中，利用波束方向图测量模型，广义度量和/或归一化的广义度量可以用来估计在接收时测量的对于一个或多个帧中的一个或多个体元的信号的主能量源的角方向。例如，当采用单个发射波束、单个主接收波束和单个辅助接收波束时，其中所有波束的方位角波束宽度都是相同的，但主接收波束的仰角波束宽度比发射波束和辅助接收波束的窄，广义度量和/或归一化的广义度量被期望是表明其每个体元或每一帧的大多数接收能量所来源于的仰角角度。发射波束、主接收波束和/或辅助接收波束的各种配置可以用于估计在接收时对于每个体元的主能量源的空间角度。In other embodiments, using the beam pattern measurement model, the generalized metric and/or the normalized generalized metric can be used to estimate the The angular direction of the primary energy source. For example, when using a single transmit beam, a single main receive beam, and a single auxiliary receive beam, where all beams have the same azimuth beamwidth, but the main receive beam has a narrower elevation beamwidth than the transmit and auxiliary receive beams, The generalized metric and/or the normalized generalized metric is expected to indicate the elevation angle from which most of the received energy per voxel or per frame originates. Various configurations of transmit beams, main receive beams, and/or auxiliary receive beams may be used to estimate the spatial angle of the main energy source for each voxel upon reception.
线性复合函数linear composite function
在一些实施方式中，复合函数可以定义为关于主接收波束和一个或多个关联的辅助接收波束的局部信息的线性函数。例如，如果使用单辅助接收波束，且对于进入扫描数据数组的记录和/或每一帧n(或对于进入扫描数据数组记录的子集和/或对于帧的子集)分别计算单独的归一化的广义度量m，则复合函数可以定义如下：In some embodiments, a composite function may be defined as a linear function of local information about the main receive beam and one or more associated auxiliary receive beams. For example, if a single auxiliary receive beam is used, and for a record into the scan data array and/or each frame n (or for a subset of incoming scan data array records and/or for a subset of frames) separately compute a separate normalized generalized metric m, then the composite function can be defined as follows:
其中S主是主接收波束的局部测量信号，S输出是杂波抑制局部信号。该等式衰减杂波影响的体元的信号，使得对于其中基本上所有的测量信号都源于杂波效应的体元的信号被抵消，然而被确定为没有杂波的体元没有被影响。Among them, Smain is the local measurement signal of the main receiving beam, and Soutput is the local signal of clutter suppression. This equation attenuates the signals of voxels affected by clutter such that the signals for voxels in which substantially all of the measured signal originates from clutter effects are cancelled, whereas voxels determined to be free of clutter are not affected.
在其它的实施方式中，如果使用单辅助接收波束，且对于进入扫描数据数组的每个记录和每一帧(或其子集)计算单独的归一化的广义度量，则复合函数可以是主接收波束的局部信号和辅助接收波束的局部信号的S辅助的线性组合：In other implementations, the composite function may be the main S-aided linear combination of the local signal of the receive beam and the local signal of the auxiliary receive beam:
其中是局部复权重(“杂波抑制权重”)，其可以针对进入扫描数据数组的每个记录和每一帧(或其子集)进行计算。杂波抑制权重被计算以便最小化杂波贡献对S输出的影响，然而相关信号的贡献被尽可能的保留。in are local complex weights ("clutter suppression weights") that can be computed for each record and each frame (or a subset thereof) entering the scan data array. The clutter suppression weights are calculated so as to minimize the influence of clutter contributions on the Soutput , while the contributions of related signals are preserved as much as possible.
如果人们归一化关于不同辅助接受波束的信号其中i是辅助波束索引，使得与主接受波束中心相对应的角方向上的所有辅助接收波束的增益将与主接收波束的增益匹配，从而得到归一化的辅助接收波束则人们能把来自主接收波束中心的信号视作“无杂波”信号S无杂波，并且对于每个接收波束的其他信号可看作是杂波信号，对于主接收波束标记为对于第i个归一化的辅助接收波束标记为If one normalizes the signal about the different auxiliary receiving beams where i is the auxiliary beam index such that the gain of all auxiliary receive beams in the angular direction corresponding to the center of the main receive beam will match the gain of the main receive beam, resulting in the normalized auxiliary receive beam Then one can regard the signal from the center of the main receive beam as a "clutter-free" signal Swithout clutter , and the other signals for each receive beam can be seen as clutter signals, denoted for the main receive beam as For the i-th normalized auxiliary receive beam labeled as
因此，杂波抑制权重应以S输出尽可能趋于S无杂波的方式计算。与在等式(3)中的方法不同，其极大地衰减了其中大多数测量信号源于杂波的体元中的信号，这种方法可以从在其中杂波是测量信号的主要来源的体元中提取出相关信息。Therefore, the clutter suppression weight should be calculated in such a way that the Soutput tends to Sclutter-free as much as possible. Unlike the method in equation (3), which greatly attenuates the signal in voxels where most of the measurement signal originates from clutter, this method can extract Extract relevant information from the element.
为了简化下面的描述，让我们用归一化的辅助接收波束信号重写等式(4)：To simplify the description below, let us rewrite Equation (4) with the normalized auxiliary receive beam signal:
其中，W是用归一化的辅助接收波束信号计算的局部复权重。where W is the local complex weight computed with the normalized auxiliary receive beam signal.
当使用等式(6)时，S输出的幅度和/或相位在局部和/或整体上可能会偏斜。这是因为杂波抑制权重旨在抵消杂波贡献，但是作为负面效应它也能影响到无杂波信号。例如，在无杂波体元中，S输出＝(1-W)S无杂波。为了避免这些影响，归一化因子应被引入到等式(6)中：When using equation (6), the magnitude and/or phase of the Soutput may be skewed locally and/or globally. This is because the clutter suppression weight is designed to counteract the clutter contribution, but as a side effect it can also affect the clutter-free signal. For example, in a clutter-free voxel, Soutput = (1-W)Sclutter-free . To avoid these effects, a normalization factor should be introduced into equation (6):
特别应注意对于W近似等于1.0的体元，使得等式(7)由于“除以零”的效果而产生非常高的信号幅度。例如，对于该体元的S输出可定义为等于S主，使得在该体元中的信号保持不变。选择性地，对于该体元的S输出可设置为在当前体元的紧邻区域中的S输出的平均或中值信号水平，其中紧邻区域可以在空间上和/或在时间上被定义，且其中对于其由等式(7)提供的值已经被替换的体元在计算时被排除在外。这种技术在其它“除以零”的效果发生的地方也可被用到。Note in particular that for voxels where W is approximately equal to 1.0, such that equation (7) produces very high signal amplitudes due to the "divide by zero" effect. For example, the Soutput for this voxel can be defined to be equal to Smain , so that the signal in this voxel remains unchanged. Optionally, the Soutput for this voxel may be set to the mean or median signal level of the Soutput in the immediate vicinity of the current voxel, where the immediate area may be spatially and/or temporally defined, and Voxels for which values given by equation (7) have been substituted are excluded from the calculation. This technique can also be used where other "divide by zero" effects occur.
在实施方式中，对于进入扫描数据数组的可用记录和/或每个可用帧n的杂波抑制权重可由如下进行估计:In an implementation, for the available records that go into the scan data array and/or the clutter suppression weights for each available frame n can be estimated by:
(a)定义在周围的区域，其中，该区域可能是空间上的(即，包含进入扫描数据数组的记录附近的集合)和/或时间上的(即，包含其索引接近n的连续帧的集合)(“空时区域”)。(a) defined in The surrounding region, where the region may be spatial (i.e., contain the collection near the records that go into the scan data array) and/or temporal (i.e., contain the collection of consecutive frames whose indices are close to n) (“null time zone").
(b)设置对于的杂波抑制权重为以下至少一个的函数：(b) set for The clutter suppression weight of is a function of at least one of the following:
(i)在该空时区域内的一个或多个广义度量和/或归一化的广义度量的值；以及(i) the value of one or more generalized measures and/or normalized generalized measures within the space-time region; and
(ii)在该空时区域内，对于主接收波束的信号S主和归一化的辅助接收波束的一个中的信号的局部复数比(“局部复数主辅比”)。(ii) In this space-time region, for the signal S of the main receive beam S themain and the normalized signal in one of the auxiliary receive beams The local complex ratio ("local complex major-auxiliary ratio").
例如，对于的杂波抑制权重可能被设定为对于在空时区域内的体元的局部复数主辅比，该空时区域的广义度量和/或归一化的广义度量的值最能表明显著杂波效应。这种示例性函数取决于以下假设：For example, for The clutter suppression weights for may be set as the local complex principal-auxiliary ratio for voxels in the space-time region for which the value of the generalized metric and/or the normalized generalized metric best indicates significant clutter effect. This exemplary function depends on the following assumptions:
(i)杂波信号贡献在空间和/或时间上变化得足够缓慢，使得人们可认为它在小的空时区域里近似于常数。(i) The clutter contribution varies slowly enough in space and/or time that one can consider it approximately constant over a small space-time region.
(ii)超声成像中的散斑效应在无杂波信号水平上(甚至在近似同质的组织区域内)常造成局部变化，使得人们期望在空时区域中的至少一个体元包括低自由度的信号水平。(ii) Speckle effects in ultrasound imaging often cause local variations at the clutter-free signal level (even within approximately homogeneous tissue regions), such that one would expect at least one voxel in the space-time region to include low degrees of freedom signal level.
在空时区域内被发现具有最实质的杂波效应的体元可被视为几乎纯的杂波，因此对于该体元的局部复数主辅比被期望于大幅减少局部杂波水平。为了更明确，如果我们把代入等式(7)里，我们可得到The voxels found to have the most substantial clutter effects in the space-time region can be regarded as almost pure clutter, so a local complex major-auxiliary ratio for this voxel is expected to substantially reduce the local clutter level. To be more explicit, if we put Substituting into equation (7), we can get
(c)特别应注意的是这样的情况，即，局部复数主辅比由于“除以零”的效果而很高。例如，在其中计算出的杂波抑制权重很高的体元中，人们可用预定值(例如，1.0或0.0)来替换它。在后一种情形中，杂波抑制将不会应用于这些体元。(c) Particular attention should be paid to the case where the local complex primary-subordinate ratio is high due to the "division by zero" effect. For example, in a voxel where the calculated clutter suppression weight is high, one can replace it with a predetermined value (eg, 1.0 or 0.0). In the latter case, clutter suppression will not be applied to these voxels.
在进一步的实施方式中，人们可以计算复合函数的输出和主接收波束信号的线性组合，其中的权重取决于归一化的广义度量。这种技术的潜在好处是降低复合函数对于无杂波体元的影响。例如，如果我们把我们的方法建立在等式(7)的基础上，我们会得到：In a further embodiment, one can compute a linear combination of the output of the composite function and the main receive beam signal, where the weights depend on a normalized generalized metric. A potential benefit of this technique is to reduce the impact of the composite function on clutter-free voxels. For example, if we base our method on equation (7), we get:
在另外的其他实施方式中，两个或多于两个的归一化广义度量能通过复合函数被定义并被使用。例如，当使用两个归一化广义度量m1和m2时,我们能使用如下等式，其中对于进入扫描数据数组的每个可用记录和/或对于每个可用帧，根据定义全部系数的和是1.0：In yet other embodiments, two or more normalized generalized metrics can be defined and used via a composite function. For example, when using two normalized generalized metrics m1 and m2, we can use the following equation, where for each available record entering the scan data array and/or for each available frame, the sum of all coefficients by definition is 1.0:
其中，S1和S2是分别基于m1和m2的杂波抑制处理的输出，其使用本文前面的任何方法应用；而S1,2是基于m1和m2两者的杂波抑制处理的输出。例如，这可通过以下方式实现，将基于m1的以上处理的一种同时应用于主接收波束和辅助接收波束(即，每次把不同波束视为主接收波束)，然后使用基于m2的上述处理的一种，在合适等式里用基于m1的杂波抑制处理的相应输出替代主接收波束信号。选择性地，S1,2可被计算作为S1和S2的简单局部统计函数，例如，局部最小值(在S1和S2之间)、局部平均值(在S1和S2之间)、等等。where S1 and S2 are the outputs of the clutter suppression processing based on m1 and m2 respectively, applied using any of the methods earlier in this paper; and S1,2 are the outputs of the clutter suppression processing based on both m1 and m2. This can be achieved, for example, by applying one of the above processes based on m1 to both the main receive beam and the auxiliary receive beam (i.e. treating a different beam as the main receive beam each time), and then using the above process based on m2 One of , substituting the corresponding output of the m1-based clutter suppression process for the main receive beam signal in the appropriate equation. Alternatively,S1,2 can be computed asa simple local statistical function of S1 and S2, e.g.,a local minimum( between S1 and S2) ,a local mean( between S1 and S2 room), etc.
在其它实施方式中，两个或多个的归一化广义度量在复合函数中可被定义和使用，其中至少一种归一化广义度量被直接使用，并且至少一种归一化广义度量被用来计算杂波抑制权重。例如，当使用两个归一化广义度量m1和m2时，其中杂波抑制权重W2使用m2来计算，如下等式可被用到：In other embodiments, two or more normalized generalized metrics may be defined and used in the composite function, where at least one normalized generalized metric is used directly and at least one normalized generalized metric is used by Used to calculate the clutter suppression weight. For example, when using two normalized generalized metrics m1 and m2, where the clutter suppression weight W2 is calculated using m2, the following equation can be used:
注意到，定义为主接收波束和辅助接收波束的局部信号的线性组合的复合函数可通过以下两种方法中的至少一种进行考虑：Note that the composite function defined as a linear combination of the local signals of the main and auxiliary receive beams can be considered by at least one of the following two methods:
(a)通过代数表达式，其设计用于抑制杂波效应。(a) By algebraic expression, it is designed to suppress the clutter effect.
(b)通过自适应波束形成方案，其设计用来把零值(null)引入到整个过程中的有效波束方向图的对应于杂波源的方向上。(b) By an adaptive beamforming scheme designed to introduce nulls into the effective beampattern throughout the process in directions corresponding to clutter sources.
应该认识到，数学等式只是作为具体实例而提供的。此外，虽然具体实例指的是线性等式，但非线性等式也可以被用到。It should be appreciated that the mathematical equations are provided as specific examples only. Furthermore, although the specific examples refer to linear equations, non-linear equations may also be used.
广义度量的滤波和/或杂波抑制权重Filtering and/or clutter suppression weights for generalized metrics
在使用广义度量和/或归一化的广义度量来计算杂波抑制权重和/或将其用于复合函数之前，可以进行时间和空间上的滤波。相似地，在复合函数中使用杂波抑制权重前，也可以进行空间滤波和/或时间滤波。这种滤波可使用扫描数据数组的坐标系来进行，其中时间轴可通过结合在多帧里收集的扫描数据数组而形成，其中连续帧是相互并排放置的。Temporal and spatial filtering may be performed before using the generalized metric and/or the normalized generalized metric to compute the clutter suppression weights and/or use them in the composite function. Similarly, spatial filtering and/or temporal filtering may also be performed before using the clutter suppression weights in the composite function. Such filtering may be performed using a coordinate system of scan data arrays, wherein a time axis may be formed by combining scan data arrays collected in multiple frames, with successive frames being placed next to each other.
本领域已知的任何滤波器都可用于该目的。例如，线性低通滤波器、带通滤波器或高通滤波器可适用于一个或多个空间轴和/或时间轴。附加地或选择性地，非线性滤波器(比如，中值滤波器)可用于一个或多个空间轴或时间轴。这种滤波器预期能降低广义度量、归一化的广义度量和/或杂波抑制权重中的局部不规则。Any filter known in the art can be used for this purpose. For example, a linear low-pass filter, band-pass filter or high-pass filter may be applied to one or more spatial and/or temporal axes. Additionally or alternatively, non-linear filters (eg, median filters) may be applied to one or more spatial or temporal axes. Such filters are expected to reduce local irregularities in generalized metrics, normalized generalized metrics, and/or clutter suppression weights.
可以考虑应用于空间轴和/或时间轴中的一个或多个中的其他非线性滤波器。例如，人们可以使用局部最小值、局部最大值、局部均值加上局部标准偏差、局部平均值减去局部标准偏差、局部信号的特定百分位数等等。当应用于归一化广义度量时，局部最小值预期来降低由杂波影响的体元的误检，由于存在使得归一化的广义度量值低的体元(即，确定为包含低的杂波水平，因此能包含几乎所有相关信息的体元)，因此也降低了在其紧邻区域中的归一化广义度量值。相似地，当应用于归一化广义度量时，局部最大值预期来提高杂波影响的体元的检测概率，由于存在使得归一化的广义度量值高的体元(即，确定为包含大部分杂波的体元)，因此也提高了在其紧邻区域中的归一化广义度量值。Other nonlinear filters applied in one or more of the spatial axis and/or the temporal axis may be considered. For example, one can use local minima, local maxima, local means plus local standard deviations, local means minus local standard deviations, specific percentiles of local signals, and so on. When applied to the normalized generalized metric, local minima are expected to reduce the false detection of voxels affected by clutter, since there are voxels that make the normalized generalized metric low (i.e., determined to contain low clutter wave level, and thus can contain almost all relevant information voxels), thus also reducing the normalized generalized measure in its immediate vicinity. Similarly, when applied to the normalized generalized metric, local maxima are expected to improve the detection probability of clutter-affected voxels, since there are voxels that make the normalized generalized metric high (i.e., determined to contain large Partially cluttered voxels), thus also improving the normalized generalized measure in its immediate vicinity.
此外，也可以考虑稍微复杂一些的非线性滤波器。例如，对于在空间和/或时间上的每个局部区域，非线性滤波器的输出可由以下过程产生：如果局部中值或局部均值或局部加权平均值比预定值高，则使用特定统计算符，否则使用另一种统计算符。这样的统计算符的实例为局部最小值、局部最大值、局部均值、局部均值加局部标准偏差、局部均值减局部标准偏差、局部信号的特定百分位数等。当应用于归一化的广义度量时，这种滤波器可能允许例如提高在杂波影响区域中的受杂波影响的体元的检测概率，与此同时，也可能会降低在无杂波区域中的误检概率，假设杂波水平在空间和时间上相对渐进地变化。In addition, slightly more complex nonlinear filters can also be considered. For example, for each local region in space and/or time, the output of the non-linear filter can be produced by the following process: if the local median or local mean or local weighted average is higher than a predetermined value, using a specific statistical operator , otherwise use another statistical operator. Examples of such statistical operators are a local minimum, a local maximum, a local mean, a local mean plus a local standard deviation, a local mean minus a local standard deviation, a particular percentile of a local signal, and the like. When applied to a normalized generalized metric, such a filter may allow, for example, to increase the detection probability of clutter-affected voxels in clutter-affected regions, while at the same time, may also decrease the probability of detection in clutter-free regions The false detection probability in , assuming that the clutter level varies relatively gradually in space and time.
附加地或选择性地，传递函数可应用于广义度量和/或归一化广义度量和/或在杂波抑制处理的不同阶段中的杂波抑制权重。在本领域中已知的任何传递函数都可以用于所设想的各种目的。应用于根据定义范围在0.0至1.0之间的归一化广义度量的传递函数应当优选地：(a)取得在0.0至1.0之间的值；以及(b)对于每一对值，其中第二个值比第一个值大，对于第二个值的传递函数的结果应该大于或等于对于第一个值的传递函数的结果。Additionally or alternatively, transfer functions may be applied to generalized metrics and/or normalized generalized metrics and/or clutter suppression weights in different stages of the clutter suppression process. Any transfer function known in the art may be used for the various purposes envisioned. A transfer function applied to a normalized generalized metric between 0.0 and 1.0 by definition should preferably: (a) take a value between 0.0 and 1.0; and (b) for each pair of values, where the second value is greater than the first value, the result of the transfer function for the second value should be greater than or equal to the result of the transfer function for the first value.
例如，在传递函数用于杂波抑制之前，其在等式(3)或/和等式(8)中应用于归一化的广义度量m。一些示例性传递函数如下所示：For example, it is applied to the normalized generalized metric m in equation (3) or/and equation (8) before the transfer function is used for clutter suppression. Some exemplary transfer functions are as follows:
(a)饱和线性函数，即，传递函数是线性的直到预定输入值，并且对于更大的输入值，输出值等于对于该预定输入值的输出值。(a) A saturated linear function, ie the transfer function is linear up to a predetermined input value and for larger input values the output value is equal to the output value for that predetermined input value.
(b)对数函数。(b) Logarithmic function.
(c)指数函数。(c) Exponential function.
(d)S形函数。(d) Sigmoid function.
后处理Post-processing
在将复合函数的输出用于任何其他的运算之前，可对该输出进行空间和/或时间处理。该处理可以采用扫描数据数组的坐标系来实施，其中时间轴可通过组合在多帧中收集的扫描数据数组而形成，其中连续帧是彼此并列放置的。The output of the composite function may be spatially and/or temporally processed before being used in any other computation. The process can be implemented using a coordinate system of scan data arrays, where a time axis can be formed by combining scan data arrays collected in multiple frames, where successive frames are placed next to each other.
在一些实施方式中，空间和/或时间处理可以包括本领域已知的各种空间和/或时间滤波器。In some implementations, spatial and/or temporal processing may include various spatial and/or temporal filters known in the art.
附加地或选择性地，对于进入扫描数据数组的每个可用记录和每个可用帧，如果满足一定的标准，可以把复合函数的输出替代成主接收波束的对应体元。选择性地，人们可以把复合函数的局部输出用在空间和/或时间上定义的复合函数输出的小的局部区域内的平均信号、加权平均信号或中值信号替代。Additionally or alternatively, for each available record and each available frame entering the scan data array, the output of the composite function may be substituted for the corresponding voxel of the main receive beam if certain criteria are met. Alternatively, one can replace the local output of the composite function with an average, weighted average or median signal over a small local region of the spatially and/or temporally defined composite function output.
例如，如果复合函数输出的局部信号幅度大于主接收波束的局部信号幅度，则复合函数的输出的局部值能被主接收波束中的对应体元的局部值所替代。可以考虑这种处理，因为杂波抑制处理理应减少杂波水平，而不会放大无杂波区域。例如，高信号幅度可以产生于诸如“除以零”的数值效果。For example, if the local signal amplitude of the composite function output is greater than the local signal magnitude of the main receive beam, the local value of the output of the composite function can be replaced by the local value of the corresponding voxel in the main receive beam. This processing can be considered because clutter suppression processing is supposed to reduce clutter levels without amplifying clutter-free regions. For example, high signal amplitudes can result from numerical effects such as "divide by zero".
另一种示例性后处理：Another exemplary postprocessing:
(a)在扫描数据数组里定义块(“数据块”)，其在当前体元的中心或近似中心。基于扫描数据数组的维数(其可能含有空间轴且也可能含有时间轴)，所述块可以是1D、2D、3D或四维(4D)的。(a) Define a block ("data block") in the scan data array that is at or near the center of the current voxel. Based on the dimensionality of the scan data array (which may contain a spatial axis and may also contain a time axis), the blocks may be ID, 2D, 3D or four-dimensional (4D).
(b)对于主接收波束的每一个和复合函数的输出，计算数据块内包含或不包含当前体元的平均幅度或加权平均幅度，然后将结果除以当前体元的幅度(可替代地，可以使用在扫描数据数组内的更小块的平均幅度)。(b) For each of the main receive beams and the output of the composite function, calculate the mean magnitude or weighted mean magnitude within the data block with or without the current voxel, and divide the result by the magnitude of the current voxel (alternatively, Average amplitudes of smaller blocks within the scan data array can be used).
(c)如果在上一步的主接收波束的输出与复合函数的输出之间的比高于(或低于)预定常数，那么在复合函数输出中的当前体元的值应被在主接收波束里的对应体元的值所替代。可替代地，如果前述标准被满足，则复合函数输出中的当前体元的值能被复合函数输出的数据块(包括或不包括当前体元)里的平均信号、加权平均信号或中值信号代替。(c) If the ratio between the output of the main receive beam in the previous step and the output of the compound function is higher (or lower) than a predetermined constant, then the value of the current voxel in the output of the compound function should be replaced by the output of the main receive beam is replaced by the value of the corresponding voxel in . Alternatively, if the aforementioned criteria are met, the value of the current voxel in the compound function output can be calculated by the average signal, weighted average signal or median signal in the data block (including or excluding the current voxel) output by the compound function replace.
例如，这种后处理可被使用以便处理在复合函数输出内的小的暗区域，其在图像的明亮连续(或较大)区域中出现。For example, such post-processing can be used in order to deal with small dark regions within the composite function output that occur in bright continuous (or larger) regions of the image.
使用多个主接收波束和/或多个辅助接收波束Using multiple primary receive beams and/or multiple secondary receive beams
在一些实施方式中，多个主接收波束可并行被使用，如在MLA配置中。在这种情况下，可定义一个或多个辅助接收波束，其中每个辅助接收波束与一个或多个主接收波束一起使用。In some embodiments, multiple main receive beams may be used in parallel, such as in an MLA configuration. In this case, one or more auxiliary receive beams may be defined, where each auxiliary receive beam is used together with one or more main receive beams.
在这种情况下，一种可能的杂波抑制方法是计算至少一个如下的“复合处理函数”：In this case, one possible approach to clutter suppression is to compute at least one "composite processing function" as follows:
(a)复合模型PDF。(a) Composite model PDF.
(b)广义度量或/和归一化的广义度量。(b) Generalized metrics or/and normalized generalized metrics.
(c)杂波抑制权重。(c) Clutter suppression weights.
(d)复合函数。(d) Composite functions.
对于进入扫描数据数组的每个可用记录和/或每个可用帧采用被分别使用的每对主接收波束以及与其相关的辅助接收波束(“主辅波束对”)。Each pair of main receive beams and their associated auxiliary receive beams ("main and auxiliary beam pairs") are employed separately for each available record and/or each available frame entering the scan data array.
附加地或选择性地，人们可定义复合模型PDF(或者其他复合处理函数)，其常见的是多于一个主辅波束对，例如，对于多个主接收波束和一个公共辅助接收波束。在这种情况下，对于在对的组内的每个主辅波束对，可对数据进行转换，其对应于不同主辅波束对间的估计差(“主辅波束对数据转换)。例如：Additionally or alternatively, one can define a composite model PDF (or other composite processing function) which is common for more than one main-auxiliary beam pair, eg for multiple main receive beams and one common auxiliary receive beam. In this case, for each main-auxiliary beam pair within the group of pairs, a transformation of the data can be performed, which corresponds to the estimated difference between different main-auxiliary beam pairs ("main-auxiliary beam pair data transformation). For example:
(a)当使用简化自适应复合模型和/或自适应复合模型时，其中单个复合模型PDF(“通用复合模型PDF”)用于多个主辅波束对，在利用主辅波束对以产生复合模型PDF(“主辅波束对数据转换”)之前，人们可以对来自每个主辅波束对的数据进行定制转换。(a) When using the reduced adaptive composite model and/or the adaptive composite model, where a single composite model PDF (“common composite model PDF”) is used for multiple primary and secondary beam pairs, the primary and secondary beam pairs are utilized to generate composite Before the model PDF ("Main and Auxiliary Beam Pair Data Transformation"), one could do a custom transformation of the data from each main and auxiliary beam pair.
(b)当计算广义度量和/或归一化的广义度量时，在将通用复合模型PDF用于广义度量和/或归一化的广义度量计算前，可以为了每个主辅波束对转换通用复合模型PDF。(b) When calculating the generalized metric and/or the normalized generalized metric, before using the general composite model PDF for the generalized metric and/or normalized generalized metric calculation, the generalized Composite Model PDF.
当添加信息到通用复合模型PDF时，可以使用对主辅波束对进行数据转换的实例中的一个或多个实例(当把通用复合模型PDF值用于广义度量和/或归一化的广义度量计算时，可使用类似但相反的转换)：When adding information to the Generic Composite Model PDF, one or more of the instances of data transformations for primary and secondary beam pairs may be used (when using the Generic Composite Model PDF values for generalized metrics and/or normalized generalized metrics When computing, a similar but reversed transformation can be used):
(a)在把基于给定的主辅波束对的信息添加到通用复合模型PDF之前，可添加常数到一个或多个信息分量中，其对应于被复合模型PDF引用的复合函数参数中的一个或几个。这种转换被称为复合模型PDF的平移。例如，如果两个或多于两个主接收波束和一个辅助接收波束被使用，其中主接收波束的波束方向图除了关于换能器阵列的相位中心的空间转动之外都是相同的，可预期的是对于两个或多于两个主辅波束对中的每对计算的复合模型PDF将是相似的，但在被复合模型PDF引用的复合函数参数的一个或多个发生了平移。(a) Before adding information based on a given main and auxiliary beam pair to the general composite model PDF, a constant may be added to one or more information components corresponding to one of the composite function parameters referenced by the composite model PDF or several. This transformation is called translation of the composite model PDF. For example, if two or more main receive beams and one auxiliary receive beam are used, where the beam patterns of the main receive beams are identical except for a spatial rotation about the phase center of the transducer array, it is expected that The composite model PDF calculated for each of the two or more main and auxiliary beam pairs will be similar, but shifted in one or more of the composite function parameters referenced by the composite model PDF.
(b)在把基于已知主辅波束对的信息添加到通用复合模型PDF之前，线性或非线性转换可被用于一个或多个信息分量，其对应于被复合模型PDF引用的一个或多个复合函数参数。线性或非线性转换可分别用于一个或多个复合函数参数，但这种转换还可用于两个或多于两个结合的复合函数参数。例如，如果使用两个或多于两个主接收波束和一个辅助接收波束，其中所有主接收波束的主瓣的波束方向图指向相同方向，但是其波束宽度不同，则可预期的是对于两个或多于两个主辅接收波束对中的每一对计算的复合模型PDF将是相似的，但却随着由复合模型PDF所引用的复合函数参数的一个或多个而伸展/压缩。(b) Before adding information based on known primary and secondary beam pairs to the general composite model PDF, a linear or non-linear transformation may be applied to one or more information components corresponding to one or more information components referenced by the composite model PDF. Composite function parameters. Linear or non-linear transformations can be applied to one or more compound function parameters individually, but such transformations can also be applied to two or more compound function parameters combined. For example, if two or more main receive beams and one auxiliary receive beam are used, where the beam patterns of the main lobes of all the main receive beams point in the same direction, but their beamwidths are different, it is expected that for the two The composite model PDF calculated for each of the or more than two primary and auxiliary receive beam pairs will be similar but stretched/compressed with one or more of the composite function parameters referenced by the composite model PDF.
在其他实施方式中，多个辅助接收波束可与单个主接收波束或与多个主接收波束并行使用。可以利用以下技术中的一个或多个，诸如：In other embodiments, multiple auxiliary receive beams may be used in parallel with a single main receive beam or with multiple main receive beams. One or more of the following techniques may be utilized, such as:
(a)一个或多个前述杂波抑制方案可分别适用于每个主辅波束对。随后，对于每个可用的小的空间体积和/或对于每个可用帧，对于一个或多个关联的主辅波束对(“多对组合函数”)，函数可以应用于杂波抑制输出。在本领域内已知的任何函数可被使用，例如，平均值函数、最大值函数、最小值函数、中值函数、预定百分位数函数、加权求和函数等等。对于诸如中值的序数算子(ordinal operator)，算子计算应基于根据它们的幅度而排序相关值。多对组合函数也可以考虑一个或多个广义度量和/或归一化的广义度量，如用于一个或多个主辅波束对所计算的，例如，可以计算加权和，其中较高权重被分配给其中信号被考虑为包括较低杂波水平的主辅波束对的值。(a) One or more of the foregoing clutter suppression schemes may be applied to each primary and secondary beam pair respectively. Subsequently, for each available small spatial volume and/or for each available frame, the function may be applied to the clutter suppression output for one or more associated primary and secondary beam pairs ("multi-pair combining function"). Any function known in the art may be used, for example, an average function, a maximum function, a minimum function, a median function, a predetermined percentile function, a weighted sum function, and the like. For ordinal operators such as median, the operator computation should be based on ordering the related values according to their magnitude. The multi-pair combining function may also take into account one or more generalized metrics and/or normalized generalized metrics, as computed for one or more primary and secondary beam pairs, e.g., a weighted sum may be computed where higher weights are The value assigned to the primary and secondary beam pairs where the signal is considered to contain a lower clutter level.
(b)对于每个可用的小的空间体积和/或可用帧，一个或多个前述杂波抑制方案可用于特定主辅波束对。杂波抑制输出之后可被看作新的(合成的)主或辅助接收波束，其与另一个辅助和/或主接收波束一起使用，作为上述一个或多个杂波抑制方案的输入。这个过程可以迭代重复若干次。(b) For each available small spatial volume and/or available frame, one or more of the aforementioned clutter suppression schemes may be used for a specific primary and secondary beam pair. The clutter suppression output can then be viewed as a new (synthesized) main or auxiliary receive beam, which is used together with another auxiliary and/or main receive beam as input to one or more of the clutter suppression schemes described above. This process can be iteratively repeated several times.
(c)对于每个可用的小的空间体积和/或对于每个可用帧，复合函数可被用于主接收波束和多个辅助接收波束，从而产生杂波抑制输出，其中复合函数使用一个或多个杂波抑制权重。例如，如果将等式(6)进行拓展从而与多个辅助接收波束联系起来，可得到：(c) For each available small volume of space and/or for each available frame, a composite function may be applied to the main receive beam and multiple auxiliary receive beams to produce a clutter suppressed output, wherein the composite function uses one or Multiple clutter suppression weights. For example, if equation (6) is extended to relate multiple auxiliary receive beams, we get:
可写出用于本文描述的任何其他杂波抑制方法的相似的等式。Similar equations can be written for any of the other clutter suppression methods described herein.
在等式(11)中的权重向量Wm或者在其他涉及多个辅助接收波束的杂波抑制等式中的相似系数，可利用本领域内已知的任何技术给估计出来。例如，可使用均方误差优化，即，对于等式(11)，每个可用的小的空间和/或时间区域的权重向量Wm可被设定以便最小化输出信号功率的期望值，即，其中E是期望算子。The weight vectorWm in equation (11), or similar coefficients in other clutter suppression equations involving multiple auxiliary receive beams, can be estimated using any technique known in the art. For example, mean square error optimization can be used, i.e., for equation (11), the weight vector W for each available small spatial and/ or temporal region can be set so as to minimize the desired value of the output signal power, i.e., where E is the expectation operator.
另一个实例将对每个主辅波束对分别计算等式(11)中的权重向量Wm、或者在引用多个辅助接收波束的其他杂波抑制等式中的相似系数，而不用考虑其它的主辅波束对。这种方法可能有用，例如，当主接收波束与一个或多个辅助接收波束的主瓣指向同一空间方向，并且对于每对主辅接收波束对，主和辅助接收波束的波束宽度沿某一方向相同，而沿另一方向不同时，其中沿着在不同主辅波束对中具有不同宽度的波束方向可能垂直也可能不垂直。这种情况下，不同主辅波束对可能被用来抑制从不同空间角度产生的相对于主接收波束的主瓣的杂波。Another example would be to compute the weight vector Wm in equation (11) separately for each main-auxiliary beam pair, or the similarity coefficients in other clutter suppression equations that refer to multiple auxiliary receive beams, regardless of other Primary and secondary beam pairs. This approach may be useful, for example, when the main lobes of the main receive beam and one or more auxiliary receive beams point in the same spatial direction, and for each pair of main and auxiliary receive beams, the beamwidths of the main and auxiliary receive beams are the same along a certain direction , while not along the other direction, where the directions along beams with different widths in different primary and secondary beam pairs may or may not be vertical. In this case, different main and auxiliary beam pairs may be used to suppress clutter generated from different spatial angles relative to the main lobe of the main receive beam.
(d)对于每个可用的小的空间体积和/或每个可用帧，复合函数可适用于主接收波束和多个辅助接收波束，从而形成杂波抑制的输出，其中复合函数是线性的，但是没有使用例如在等式(3)中描述的杂波抑制权重。在这种情况下，广义度量和/或归一化的广义度量可能取决于复合函数参数，其涉及与一个或多个主接收波束关联的多于一个的辅助接收波束。例如，当使用与单个主接收波束关联的两个辅助接收波束时，可使用如下的复合函数参数：(d) for each available small spatial volume and/or each available frame, a composite function may be applied to the main receive beam and multiple auxiliary receive beams to form a clutter-suppressed output, where the composite function is linear, But no clutter suppression weights such as those described in equation (3) are used. In this case, the generalized metric and/or the normalized generalized metric may depend on composite function parameters involving more than one auxiliary receive beam associated with one or more main receive beams. For example, when using two auxiliary receive beams associated with a single main receive beam, the composite function parameters can be used as follows:
(i)在主接收波束和第一辅助接收波束之间的局部相对幅度；(i) the local relative magnitude between the main receive beam and the first auxiliary receive beam;
(ii)在主接收波束和第一辅助接收波束之间的局部相位差；(ii) the local phase difference between the main receive beam and the first auxiliary receive beam;
(iii)在主接收波束和第二辅助接收波束之间的局部相对幅度；(iii) the local relative amplitude between the main receive beam and the second auxiliary receive beam;
(iv)在主接收波束和第二辅助接收波束之间的局部相位差。(iv) The local phase difference between the main receive beam and the second auxiliary receive beam.
(e)对于每个可用的小的空间体积和/或每个可用帧，复合函数可适用于主接收波束和多个辅助接收波束，从而形成杂波抑制的输出，其中：(e) For each available small volume of space and/or each available frame, a composite function may be applied to the main receive beam and multiple auxiliary receive beams to form a clutter-suppressed output, where:
(i)复合函数使用一个或多个杂波抑制权重；以及(i) the composite function uses one or more clutter suppression weights; and
(ii)一个或多个广义度量和归一化的广义度量可能取决于复合函数参数，其涉及与一个或多个主接收波束关联的多于一个的辅助接收波束。(ii) One or more generalized metrics and the normalized generalized metrics may depend on composite function parameters involving more than one auxiliary receive beam associated with one or more main receive beams.
(f)对于每个可用的小的空间体积和/或每个可用帧，复合函数可适用于主接收波束和多个辅助接收波束，从而形成杂波抑制的输出，其中任何复合函数都可以使用。(f) For each available small volume of space and/or each available frame, a composite function can be applied to the main receive beam and multiple auxiliary receive beams to form a clutter-suppressed output, where any composite function can be used .
如上所述，一个或多个接收波束在不同主辅波束对的情况中，可既被用作主接收波束又被用作辅助接收波束。As mentioned above, one or more receive beams may be used as both primary and secondary receive beams in the case of different pairs of primary and secondary beams.
使用具有不同的相位中心的主接收波束和辅助接收波束Using main and auxiliary receive beams with different phase centers
在一些实施方式中，对于每个主接收波束，所有关联的辅助接收波束的相位中心与对应的主接收波束的相位中心相同。在另一些实施方式中，至少有一个主辅接收波束对的主接收波束和辅助接收波束有不同的相位中心(“非同心主辅波束对”)。In some embodiments, for each main receive beam, the phase center of all associated auxiliary receive beams is the same as the phase center of the corresponding main receive beam. In some other embodiments, at least one main and auxiliary receiving beam pair has a main receiving beam and an auxiliary receiving beam having different phase centers ("non-concentric main and auxiliary beam pair").
这种配置的示例性应用是对除了旁瓣杂波效应之外的混响效应的抑制。对不同接收相位中心测量的混响副产物预期是不同的，使得复合函数可以既会抑制旁瓣杂波又会抑制混响。An exemplary application of this configuration is the suppression of reverberation effects in addition to sidelobe clutter effects. The reverberation by-products are expected to be different for different receive phase center measurements, allowing the composite function to suppress both sidelobe clutter and reverberation.
在非同心主辅波束对中，与辅助接收波束相关联的扫描数据数组相对于与对应的主接收波束相关联的扫描数据数组可平移和/或旋转。在某些实施方式中，空间配准可被用于在非同心主辅波束对中与主接收波束和辅助接收波束相关联的扫描数据数组之间(“主辅波束对配准”)。这种配准可被执行，用于整个成像循环(cine-loop)、分别用于每一帧，用于每一帧中进入扫描数据数组的每个记录或邻近记录的组、或用于在整个成像循环中的进入扫描数据数组的每个记录或邻近记录的组。空间配准可用本领域内的任何已知技术进行。在一些例子中，空间配准可能是僵化的(rigid)，要考虑全局平移和/或全局旋转。附加地或选择性地，空间配准可能是不僵化的(non-rigid)，也应考虑到因介质里的物理效应而引起的局部变形。在一些例子中，一些平移参数(诸如全局平移和全局旋转)可能直接源于已知且可控的主和辅助接收波束的中心线的相对几何关系。附加地或可选择地，一些平移参数可根据主辅接收波束中心线的相对几何关系来进行初始估计，然后根据各自得到的扫描数据数组进行微调。In a non-concentric primary and secondary beam pair, the scan data array associated with the secondary receive beam may be translated and/or rotated relative to the scan data array associated with the corresponding primary receive beam. In some embodiments, spatial registration may be used between scan data arrays associated with the main and auxiliary receive beams in non-concentric main and auxiliary beam pairs ("main and auxiliary beam pair registration"). This registration can be performed for the entire cine-loop, for each frame individually, for each record or group of adjacent records entering the array of scan data in each frame, or for each Each record or group of contiguous records in the incoming scan data array throughout the imaging cycle. Spatial registration can be performed using any technique known in the art. In some instances, spatial registration may be rigid, taking global translation and/or global rotation into account. Additionally or alternatively, the spatial registration may be non-rigid, taking into account also local deformations due to physical effects in the medium. In some examples, some translation parameters (such as global translation and global rotation) may be derived directly from the known and controllable relative geometry of the centerlines of the main and auxiliary receive beams. Additionally or alternatively, some translation parameters can be initially estimated according to the relative geometric relationship between the centerlines of the main and auxiliary receiving beams, and then fine-tuned according to the respectively obtained scan data arrays.
在非同心主辅波束对中，体元的中心和主接收波束的中心线之间的空间角(“主空间角”)通常与所述体元的中心和各个辅助接收波束的中心线之间的空间角(“辅空间角”)不同。而且，主空间角和辅空间角之间的差别对于不同体元可能是不同的。因此，如对于沿主接收波束的中心线的反射器所计算的，局部相对幅度和/或主和辅助接收波束的局部相位差可能会根据范围而改变(“参数范围可变性”)。在某些实施方式中，可对复合函数进行调整以处理这种参数范围可变性。例如，可利用如上述的主辅波束对数据转换，其中对一些体元的转换可从每个体元或体元组的主空间角和辅空间角得到，其中主空间角和辅空间角可基于体元中心相对于主接收波束和辅助接收波束的相位中心的几何位置而进行计算，和/或如果适用的话根据主辅波束对配准过程的输出计算得到。In a non-concentric primary and secondary beam pair, the spatial angle between the center of the voxel and the centerline of the primary receive beam (the "primary spatial angle") is typically the same as that between the center of the voxel and the centerline of each auxiliary receive beam The space angle ("auxiliary space angle") is different. Also, the difference between the primary and secondary space angles may be different for different voxels. Consequently, the local relative magnitude and/or local phase difference of the main and auxiliary receive beams may vary according to range, as calculated for reflectors along the centerline of the main receive beam ("parameter range variability"). In some embodiments, the composite function can be tuned to handle this parameter range variability. For example, a primary and secondary beam pair data transformation as described above can be utilized, where the transformation for some voxels can be derived from the primary and secondary spatial angles for each voxel or group of voxels, where the primary and secondary spatial angles can be based on The voxel center is calculated relative to the geometrical position of the phase centers of the main and auxiliary receive beams, and/or if applicable, from the output of the main and auxiliary beam pair registration process.
基于杂波解相关时间和时空分析的杂波抑制Clutter suppression based on time and space-time analysis of clutter decorrelation
如上引用的，美国专利8,045,777描述了杂波抑制方法，其基于计算在主接收波束中以及在一个或多个辅助接收波束中的信号的线性组合，其中线性组合的相关系数(“时间杂波抑制权重”)被计算，从而抑制由于杂波导致的反射，其中反射被确定为在确定的解相关时间高于指定阈值时与杂波相关联(“时间杂波抑制处理”)。当单个辅助接收波束与每个主接收波束关联时，可用以下的等式：As cited above, U.S. Patent 8,045,777 describes a clutter suppression method based on computing a linear combination of the signals in the main receive beam and in one or more auxiliary receive beams, where the correlation coefficient of the linear combination ("temporal clutter suppression weight") are calculated to suppress reflections due to clutter that are determined to be associated with clutter when the determined decorrelation time is above a specified threshold ("temporal clutter suppression processing"). When a single auxiliary receive beam is associated with each main receive beam, the following equation can be used:
其中，对于进入扫描数据数组的每个可用记录和/或每个可用帧n的复权重Wt计算如下：where, for each available record that goes into the scanned data array and/or the complex weight Wt for each available frame n is computed as follows:
其中Ft是时间低通滤波器，应用于进入扫描数据数组的每个可用记录和/或每个可用帧。where Ft is a temporal low-pass filter applied to each available record and/or each available frame entering the scan data array.
这种技术可利用同样取决于时间杂波抑制权重的复合函数来与其杂波抑制技术结合起来。例如，除了一个或多个时间杂波抑制权重以外，一种或多种广义度量和归一化的广义度量可被使用，如可参考以下示例性等式：This technique can be combined with its clutter suppression technique using a composite function that also depends on temporal clutter suppression weights. For example, in addition to one or more temporal clutter suppression weights, one or more generalized metrics and normalized generalized metrics can be used, as can be seen with reference to the following exemplary equations:
其中m是归一化的广义度量，用来基于估计的局部杂波贡献来调整每个体元里的时间杂波抑制处理的效果。where m is a generalized metric of normalization used to adjust the effect of the temporal clutter suppression process in each voxel based on the estimated local clutter contribution.
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