Abstract:
The present disclosure is directed to systems and methods which avow for ultrasound parameter estimation to occur at specific advantageous sets of points in a two- or three-dimensional field of view within re-configurable, massively parallel, programmable architectures that can accommodate the input/output streaming, data movement or storage, and computation requirements. In one embodiment, a power efficient system is used for processing the data thereby increasing the ability of the system to be used for hand carried or mobile ultrasound applications. One aspect of the concepts discussed herein is the architectural aspects which provide the ability to simultaneously accept a large number of channels of data characterized by a continuous, simultaneous flow at high sample rates. The input data is routed at high rates to a distributed and large number of processing elements, memory, and connections for simultaneous parameter estimation at multiple points in the field of view. The ability to route the same data to multiple places enables high frame rates and allows for the streaming of data through the architecture.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
       [0001]    This Application is a continuation of U.S. patent application Ser. No. 11/768,678 filed Jun. 26, 2007, which is a Non-Provisional of U.S. Provisional (35 USC 119(e)) Application No. 60/917,792 filed May 14, 2007. 
     
    
     TECHNICAL FIELD 
       [0002]    In the field of sonography, ultrasound images are produced by an ultrasound imaging system (scanner) that includes a transducer to ensonify (transmit ultrasound energy into) an anatomical region of interest and to receive the energy response of the tissue. Typically, the system controls the signals transmitted by the transducer, processes the electronic signals received, and presents the resulting images on a display device. Depending on the application and the processing applied to the received signals, the images may represent the spatial variation of the reflected energy itself or other parameters of interest (e.g., the distribution of blood flow velocity, etc.). In medical applications, the image or a sequence of images allow a trained reader to diagnose possible abnormal conditions that otherwise would be unobservable. 
       BACKGROUND 
       [0003]    Many techniques have been developed to transmit and receive ultrasound energy, to process the received data, and to condition the images for display. Typically, the transducer is composed of several individual elements that independently transmit and receive ultrasound energy. To form diagnostically useful images, the received ultrasound energy is focused into beams by summing weighted contributions from the individual elements at carefully selected (and dynamically adjusted) sample times to compensate for the differences in propagation time from each element to points along the beam. Transmit beams are also formed by controlling the relative time of the transmissions from the individual elements. Conventional ultrasound scanners construct image data for a single frame by transmitting and receiving many such beams in succession. The image sequence presented to the human reader and used for diagnosis is constructed from a series of such frames. 
         [0004]    The quality of the image sequences produced by conventional ultrasound scanners has several limitations. For example, the frame rate, or temporal resolution, is limited by the propagation time of the ultrasound beams and the fact that constructing a frame of image data requires many sequential beam transmissions. To produce useful image data at acceptable frame rates, ultrasound scanners must process data received from many independent channels (transducer elements) at very high sample rates (e.g., 64 channels at 24 MHz sample rate). This imposes stringent data throughput and computational requirements that are difficult to satisfy. Conventional ultrasound scanners typically address these requirements by incorporating dedicated and highly specialized hardware (e.g., custom designed analog circuitry or digital ASICs) to beamform and to process the resulting data. Because the hardware is so specialized, the functions of these systems are fairly rigidly defined and not easily reconfigurable. Also, once combined by the hardware to form beam data, the original element data are lost (i.e., hardware beamforming is an irreversible process) and are not available for additional processing. For example, if it is desired to form more than one beam from a set of element data by applying different sets of weights and delays (e.g., to increase frame rates), multiple hardware beamformers are required, adding to system complexity, cost, and power consumption. 
         [0005]    Another drawback of typical hardware-based beamforming is that it is difficult to use the beamformed data for more than one image modality. The consequence of this is that frame-rates are often dramatically reduced when two or more parametric image sequences (e.g., reflectivity and color velocity) are simultaneously displayed. New parametric image techniques that would expand the diagnostic utility of ultrasound are difficult to achieve because of the rigidity of typical hardware-based beamforming systems, 
         [0006]    Spatial resolution is limited by the fact that each transmit beam is typically well focused at only one point (at most) because the relative timing of the respective clement transmissions is fixed for each transmission event. Image quality is also limited by the fact that the display coordinates typically do not match the locations where the beams are sampled (e.g., the data may be acquired in polar coordinates, but the image pixels on a display are typically arranged in a rectangular grid). Image formation then requires an interpolation process that is an approximation, resulting in a loss of information. 
         [0007]    In addition to the foregoing problems, the information contained in the image data from many conventional scanners is limited to a single two-dimensional plane that has a fixed orientation with respect to the transducer. Methods and apparatuses, typically referred to as 3D/4D systems, have been introduced to address this limitation. These systems interrogate an anatomical volume of interest with ultrasound and reconstruct the received data for the entire volume. A variety of methods may then be used to construct images and image sequences for the entire volume or for desired two-dimensional slices through it. Frame rates and/or spatial resolution are sacrificed, however, because data for the entire volume must be acquired and processed. 
       SUMMARY 
       [0008]    The present disclosure is directed to systems and methods which allow for ultrasound parameter estimation to occur at specific advantageous sets of points in a two- or three-dimensional field of view within re-configurable, massively parallel, programmable architectures that can accommodate the input/output streaming, data movement or storage, and computation requirements. In one embodiment, a power efficient system is used for processing the data thereby increasing the ability of the system to be used for hand carried or mobile ultrasound applications. 
         [0009]    One aspect of the concepts discussed herein is the architectural aspects which provide the ability to simultaneously accept a large number of channels of data characterized by a continuous, simultaneous flow at high sample rates. The input data is routed at high rates to a distributed and large number of processing elements, memory, and connections for simultaneous parameter estimation at multiple points in the field of view. The ability to route the same data to multiple places enables high frame rates and allows for the streaming of data through the architecture. The ability to reconfigure the system allows for the estimation of various types of parameters at different times or even simultaneously. The architecture is extensible through interconnections between physical devices. 
         [0010]    Another aspect to the acquisition of parameter estimation is the use of filters (linear or non-linear) for correcting diffraction and/or propagation effects per channel. These filters also can delay channel data for localizing the estimation of a parameter to a particular locality such as done in beamforming, and controlling signal, clutter, noise, and various fowls of resolution. The filtered data may be combined in a number of ways. Acquisition of multiple sets of points for display is possible. For example, multiple planes (lines) through a two- or three-dimensional field of view may be formulated from the same acquired data, thereby avoiding the need for scan conversion and rendering when the sets of points correspond to displayed pixels. It is also possible within this system to localize the parameter estimation process by synthesizing the source signal. 
         [0011]    Another aspect to parameter estimation is the ability to re-configure and/or re-program the architecture to apply the proper operations for the estimation of a particular parameter or parameters such as reflectivity, elasticity, strain rate, and motion. 
         [0012]    The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in which: 
           [0014]      FIG. 1  illustrates one embodiment of a system for employing the techniques of the invention; 
           [0015]      FIG. 2  illustrates one embodiment of some of the architectural elements within the invention; 
           [0016]      FIG. 3  illustrates one embodiment of a physical device conforming to the architectural elements within the invention; 
           [0017]      FIG. 4  illustrates one embodiment of interconnected processors which extend the architectural elements of the invention; and 
           [0018]      FIG. 5  illustrates one embodiment of a system for employing the parameter acquisition techniques of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]      FIG. 1  illustrates one embodiment  10  of a system for employing the techniques of the invention. Transducer  101 , as is well-known in sonography, sends sound signals into a body, such as a human body, and receives the echoes therefrom. The returned echoes in the form of acoustic information are translated into electrical signals which then, as will be discussed, are used to estimate various parameters at advantageous sets of geometric locations. In one embodiment, this estimation is accomplished by Massively Parallel Processors (MPP)  30  for presentation to user  13 . Front end  19  receives the return electrical signals from the ensonified volume, compensates and filters this data and then presents this volume data to analog to digital converter (ADC)  18 . These digitized signals representing the return echoes (energy response) may be streamed through MPP subsystem  12 . 
         [0020]    One embodiment of MPP subsystem  12  is depicted in three parts. MPP  30  performs beam forming, signal processing, parameter estimation, and other operations to create images suitable for the user using signals from ADC  18 . MPP control interface  11  configures MPP  30  to perform the appropriate functions based on instructions that are received from controller  15  which, in turn, are based upon selections from the user  13 . 
         [0021]    Database  14  supplies pre-determined and default processing control variables required by MPP  30 . Data from MPP  30  is passed along to image and video processing  16  for further formatting and processing of data for presenting to the user through Display  17 . In one embodiment, elements  12 ,  14 ,  15 ,  16 , and  17  can be contained in a device weighing 10 lbs. or less. 
         [0022]      FIG. 2  illustrates one embodiment  20  of some of the elements within MPP Subsystem  12 . Digital signals from ADC  18  are received by input interface  24  and formatted to be presented to digital signal conditioning process  25  which performs signal processing operations, typically filtering, that are advantageous to apply prior to beam formation. 
         [0023]    The conditioned data is then presented to coherent spatial/temporal filtering and combining process  26 . This function seeks to enhance and localize, typically with some form of filtering, whether it be linear or non-linear, the accurate estimation of parameters at advantageous sets of geometrical locations. Some functions performed here, that are well known by those experienced in the art, are demodulation, beam forming including multi-line beam aiming, cross correlation, normalization, multi-rate quadrature band pass (QBP) filtering, Doppler wall filtering, and fast Fourier transforms (FFT) which among other advantages improve signal to noise and clutter. These functions may be also used to improve various forms of resolution metrics, including axial resolution, lateral resolution, contrast resolution, and detail resolution. The generation of parameters to support these functions is also a function suitable to process  26 . 
         [0024]    Image data that are localized and enhanced at geometrically advantageous geometric locations are then presented to parameter estimation process  27  which generates the particular estimates of the type of parameters to be used for display. Some functions performed here, that are well known by those experienced in the art, are detection of signal intensity, compression, Doppler wall filter filtering for flow imaging, segmentation, velocity estimation, strain estimation, strain rate estimation, classification, spatial compounding, scan conversion, rendering, and spatial-temporal image processing. 
         [0025]    One embodiment of MPP control interface  11  performs three functions. As will be described hereinafter, data router  21  configures the connectivity of the distributed bus architecture of MPP  30  to effectively route data among the distributed processing elements and memory devices. Static and dynamic control variable generator  22  distributes and/or creates control variables required for the various data processing functions. Some of these control variables may be pre-computed and retrieved from database  14  ( FIG. 1 ) while others may be newly generated using, for example, processors within MPP  30 . Finally, code distribution and reconfiguration process  23  governs what processing algorithms are to be accomplished on which processors and in which order. 
         [0026]      FIG. 3  shows one embodiment of massively parallel processor (MPP)  30 . The actual form which the hardware (ASIC, FPGA, etc.) takes is not critical to the operation of the concepts discussed herein. These concepts rely, instead, on a massively parallel, re-configurable, and distributed network of processing elements, memory, and communication or equivalent thereto. These features enable the high aggregate rates of data movement required by ultrasound and reduce high bandwidth demands on memory devices by enabling streaming of data, multiple and simultaneous use of data, and re-routing of data. Moreover, these features enable the functionality to be changed or multiple functions corresponding to different ultrasound modalities to be configured for simultaneous operation even using the same echo returns. 
         [0027]    The internal processors are interconnected by a distributed network of connections which allow for efficient transfer and replication of data. Ultrasound applications have high bus bandwidth requirements which are more easily satisfied with a distributed network of buses. Port  306  allows this particular processor to extend communicating to other processors on other MPP devices. Ports  305  are similar types of ports which allow wide bandwidth data input and output to the MPP. Fabric  307  allows connectivity to occur among and between individual processors such that, if necessary, data produced by one processor can be used simultaneously by several other processors. This then allows for efficient replication of data. Moreover, this allows beam forming to be simultaneously processed at multiple sets of geometrical locations. 
         [0028]    It is envisioned that the individual processors making up the MPP will carry out their designated operations independently of each other except for the flow of data. They will also be able to be configured or rapidly re-configured to perform individual operations which when appropriately connected performs useful ultrasound applications. These processors need not be homogeneous. In the embodiment shown, there are several different types of processors,  301 ,  302 ,  303 ,  304 , etc. Some types of processors are optimized for specific functions while others handle more general purpose processing needs. The optimized processors may be functional acceleration units (specialized processors) to carry out dedicated functions with greater efficiency than the general purpose processors for ultrasound applications. For example, one type of processor may be particularly suited for geometric transformations while another may be suited for accelerating fast Fourier transforms or cross correlations. 
         [0029]    It is envisioned that the memory is also distributed in order to accommodate the high memory bandwidth needs of ultrasound applications. To accomplish this, data is stored, for example on distributed memories  308 , in association to where that data is required to be used and not according to a centralized memory architecture typical of the microprocessor architectures of personal computers. 
         [0030]    In operation, MPP  30  can receive a multiplexed, encoded set of individual channels or individual elements from the array via ports  305 . This data is then processed, on a channel by channel basis, in a manner required for that channel at that moment in time. The processing depends, at least in part, on the user selected surfaces through the ensonified volume. Since the different or same channels can be processed differently and repeatedly, the system allows for the desired processing at the desired surfaces defined by the advantageous sets of geometrical locations. The use of streaming in such architecture reduces power requirements as it avoids massive usage of memory. 
         [0031]    Returning now to  FIG. 1 , MPP control interface  11  provides information to MPP  30  for controlling the individual MPP devices, thereby allowing for the selection of one or more different surfaces to be presented concurrently. The configuration of the MPP devices can be static, which means that control variables and configuration information are pre-computed and retrieved by the controller from the database. The configuration can be dynamic in that selections for the configurations by the user, or other source, are given to the MPP subsystem which computes new processing control variables and configuration settings. 
         [0032]      FIG. 4  shows one embodiment  40  of the interconnection of MPPs  30 . Ports  305  and  306  are used for collecting data from the transducer as well as for connecting with other similar MPP devices. This allows for the efficient transfer of data and for the overall compute power to be increased as needed to accommodate the required signal or image processing. This also allows for assigning more or less individual processing elements, such as arithmetic logic units, memory, storage, etc. into a data stream for processing. The control of the processors, as well as the functions performed by the different processors, can be controlled, as discussed, by programmable digital processing elements. This programming can be accomplished by a variety of techniques, including, for example, machine language code or binary images. The elements could contain, if desired, field programmable gate arrays (FPGA). 
         [0033]      FIG. 5  shows one embodiment  50  of the non-traditional ultrasound imaging capability that is afforded by the concepts discussed herein. In this embodiment, transducer  101  ( FIG. 1 ) is used to ensonify a volume  501 . Volume  501  is depicted as a two-dimensional array although analogous imaging can be performed by other transducer element arrangements to form, if desired, a three-dimensional array or one-dimensional array. As conditioned, digitized, return echoes are able to be replicated by the architecture, simultaneous beam forming can be accomplished along multiple surfaces  502 ,  503 ,  504 , and  505  using the same ensonified volume data  501 . This is of significant advantage to ultrasound imaging as only one ensonification sequence is required to form multiple images as with the case of 3D/4D modality where multiple and orthogonal planes are typically presented, This allows greatly improved frame rates to be displayed, for example, on display  17 . 
         [0034]    Although the surfaces in  FIG. 5  indicate planes, other surfaces can be more advantageous. Such surfaces might also include contours along anatomical features, such as along boundaries of the heart or other organs. Also, the system could be made to beam form to pre-determined surfaces rotated or translated in several degrees of freedom by the user. At any point in time the user can select separate surfaces and present the selected surfaces concurrently on different portions of the display screen, Some of the views could be from planes that are rotating or otherwise changing so as to present a changing image on the display. Thick surface or stacked parallel surfaces may also be acquired for rendering purposes. All of these views of the target image are anchored without necessarily moving transducer  101 . In one embodiment, the MPP system is used to assist in computing new control variables to quickly reconfigure the system for the user directed imaging selections. Flexibility is required since the system must be able to quickly reconfigure the computation based on the user input. 
         [0035]    It is easily seen that the time course of imaging parameters along an arbitrary contour through the field of view can be accurately and efficiently measured and displayed. 
         [0036]    Another advantage to the acquisition approach of this invention implicit in  FIG. 5 , is the ability to form beams at geometrical locations that directly correspond to pixels on the display. In this way, approximations and unwanted artifacts of scan conversion, rendering, and beam under-sampling can be avoided which greatly improves image quality. Zooming an image may be implemented by this invention as forming beams to a new, more dense set of geometrical locations corresponding to the desired locations of the new pixel centers. 
         [0037]    Furthermore, since beam formation occurs at pixel locations, the number of different planes to be displayed simultaneously on the display does not increase beamforming requirements and frame rates need only be limited by the deepest depth in the field of view. 
         [0038]    Note that in addition to displaying images that represent the intensity of the sound reflected along a selected plane, other parametric images can be formed to present different tissue properties, such as strain or other modalities that require additional processing. These different modalities may be performed simultaneously with the same received echoes, which greatly improves imaging rate. Also, it is desirable to provide multiple images of surfaces or volumes without moving the transducer. For example, as discussed, the imaging display is partitioned so as to present different images of the same target simultaneously without moving the transducer. Each window of the display may show a different projection of the volume acquisition signal or different parameters thereof. Also, size can be varied with respect to each window. 
         [0039]    Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.