Ultrasound imaging beam-former apparatus and method

Abstract

In some illustrative embodiments, an incoming signal from a transducer in an ultrasound imaging beam-former apparatus is applied to an in-phase sample-and-hold and a quadrature sample-and-hold. The quadrature sample-and-hold may be clocked a quarter period behind the in-phase sample-and-hold. The output of the sample-and-holds are applied to in-phase and quadrature analog-to-digital converters. A magnitude calculator receives the in-phase and quadrature digital values, and outputs a magnitude. A phase calculator receives the in-phase and quadrature digital values, and outputs a phase. An apodizer applies a difference between an amplitude of the outgoing signal and the magnitude and applies a first illumination to a image point in substantial proportion to the difference, and a phase rotator applies a second illumination to the image point in substantial proportion to the phase.

1 . An ultrasound imaging beam-former apparatus, comprising: 
 a signal generator for producing an outgoing signal;    a transducer for converting said outgoing signal to outgoing ultrasound and for converting at least a portion of said outgoing ultrasound that is reflected to an incoming signal, said incoming signal having a period; and    a signal receiver for processing said incoming signal, said signal receiver comprising:    an in-phase sample-and-hold connected receivably to said transducer for sampling said incoming signal at an incoming time and outputting an in-phase amplitude of said incoming signal at substantially said incoming time;    a quadrature sample-and-hold connected receivably to said transducer for sampling said incoming signal at substantially one-quarter of said period after said incoming time, said quadrature sample-and-hold outputting a quadrature amplitude of said incoming signal at substantially one-quarter of said period after said incoming time;    a phase calculator connected receivably to said in-phase sample-and-hold and said quadrature sample-and-hold for receiving said incoming time, said in-phase amplitude, and said quadrature amplitude and outputting a phase; and    a phase rotator for applying an illumination to said image point in substantial proportion to said phase.    
     
     
         2 . The ultrasound imaging beam-former apparatus of  claim 1 , comprising further: 
 an in-phase analog-to-digital converter connected receivably to said in-phase sample-and-hold for assigning an in-phase digital value to said in-phase amplitude and outputting said in-phase digital value.    
     
     
         3 . The ultrasound imaging beam-former apparatus of  claim 1 , comprising further: 
 a quadrature analog-to-digital converter connected receivably to said quadrature sample-and-hold for assigning a quadrature digital value to said quadrature amplitude and outputting said quadrature digital value.    
     
     
         4 . The ultrasound imaging beam-former apparatus of  claim 1 , wherein signal has an outgoing amplitude; 
 a magnitude calculator connected receivably to said in-phase analog-to-digital converter and said quadrature analog-to-digital converter for receiving said incoming time, said in-phase digital value, and said quadrature digital value and outputting a magnitude; and    an apodizer for applying a difference between an outgoing amplitude of said outgoing signal at an outgoing time and said magnitude and applying a second illumination to a image point in substantial proportion to said difference.    
     
     
         5 . The ultrasound imaging beam-former apparatus of  claim 1 , comprising further: 
 a second transducer for converting said outgoing signal to second outgoing ultrasound and for converting at least a portion of said outgoing ultrasound and said second outgoing ultrasound that is reflected to a second incoming signal, said second incoming signal having a second period; and    a second signal receiver for processing said second incoming signal, said second signal receiver comprising:    a second in-phase sample-and-hold connected receivably to said second transducer for sampling said second incoming signal at a second incoming time and outputting a second in-phase amplitude of said second incoming signal at substantially said second incoming time;    a second quadrature sample-and-hold connected receivably to said second transducer for sampling said second incoming signal at substantially one-quarter of said second period after said second incoming time,    said second quadrature sample-and-hold outputting a second quadrature amplitude of said second incoming signal at substantially one-quarter of said second period after said second incoming time;    a second phase calculator connected receivably to said second in-phase sample-and-hold and said second quadrature sample-and-hold for receiving said second incoming time, said second in-phase amplitude, and said second quadrature amplitude and outputting a second phase; and    a second phase rotator for applying a second illumination to said second image point in substantial proportion to said second phase; and    a summer for combining said difference, said second difference, said phase, and said second phase before said illumination and said second illumination are applied to said image point.    
     
     
         6 . The ultrasound imaging beam-former apparatus of  claim 1 , wherein said signal generator comprises further a generator amplifier for amplifying said outgoing signal.  
     
     
         7 . The ultrasound imaging beam-former apparatus of  claim 1 , wherein said signal receiver comprises further a receiver amplifier for amplifying said incoming signal.  
     
     
         8 . The ultrasound imaging beam-former apparatus of  claim 1 , wherein said signal receiver comprises further a receiver pre-amplifier for amplifying said incoming signal.  
     
     
         9 . The ultrasound imaging beam-former apparatus of  claim 1 , wherein said signal receiver comprises further a band-pass filter for filtering said incoming signal.  
     
     
         10 . The ultrasonic imaging beam-former apparatus of  claim 1 , wherein said signal receiver comprises a digital signal processor.  
     
     
         11 . The ultrasonic imaging beam-former apparatus of  claim 1 , wherein said outgoing signal is selected from the group consisting of: 
 an electro-magnetic signal,    an electrical signal, and    an optical signal.    
     
     
         12 . The ultrasonic imaging beam-former apparatus of  claim 1 , wherein said incoming signal is selected from the group consisting of: 
 an electro-magnetic signal,    an electrical signal, and    an optical signal.    
     
     
         13 . The ultrasonic imaging beam-former apparatus of  claim 1 , wherein said transducer is selected from the group consisting of: 
 a piezoelectric element,    a voice coil,    a MEMS device,    a capacitive micro-machined transducer,    a crystal oscillator, and    a Hall effect transducer.    
     
     
         14 . The ultrasonic imaging beam-former apparatus of  claim 1 , wherein said signal receiver is implemented as an integrated circuit.  
     
     
         15 . The ultrasonic imaging beam-former apparatus of  claim 1 , wherein the transducer comprises further a plurality of transducers.  
     
     
         16 . The ultrasonic imaging beam-former apparatus of  claim 12 , wherein said plurality of transducers forms an array selected from the group consisting of: 
 a linear array,    a phased array a curvilinear array,    an unequally sampled 2-D array,    a 1.5-D array,    a catheter based array,    an intra-cavity array,    an equally sampled 2D,    a sparse 2D array, and    fully sampled 2D array.    
     
     
         17 . The ultrasonic imaging beam-former apparatus of  claim 1 , comprising further a protection circuit to allow both transmit and receive operations.  
     
     
         18 . A method of beam-forming for ultrasound imaging, comprising: 
 generating an outgoing signal;    transducing said outgoing signal to outgoing ultrasound;    receiving at least a portion of reflected outgoing ultrasound;    transducing said reflected ultrasound to an incoming signal having a period;    sampling said incoming signal at an incoming time to produce an in-phase amplitude of said incoming signal;    sampling said incoming signal at substantially one-quarter of said period after said incoming time to produce a quadrature amplitude of said incoming signal;    calculating a phase at said incoming time based on said in-phase amplitude and said quadrature amplitude; and    applying a illumination to an image point in substantial proportion to said phase.    
     
     
         19 . The method of beam-forming for ultrasound imaging of  claim 18 , comprising further: 
 assigning an in-phase digital value to said in-phase amplitude.    
     
     
         20 . The method of beam-forming for ultrasound imaging of  claim 18 , comprising further: 
 assigning a quadrature digital value to said quadrature amplitude.    
     
     
         21 . The method of beam-forming for ultrasound imaging of  claim 18 , comprising further: 
 calculating a magnitude at said incoming time, based on said in-phase amplitude and said quadrature amplitude;    measuring a difference between an outgoing amplitude of said outgoing signal and said magnitude; and    applying a second illumination to said image point in substantial proportion to said difference.    
     
     
         22 . The method of beam-forming for ultrasound imaging of  claim 18 , comprising further: 
 transducing said outgoing signal to second outgoing ultrasound;    receiving at least a portion of reflected outgoing ultrasound and second outgoing ultrasound;    transducing said reflected outgoing ultrasound and second outgoing ultrasound to a second incoming signal having a second period;    sampling said second incoming signal at said incoming time to produce a second in-phase amplitude of said second incoming signal;    sampling said second incoming signal at substantially one-quarter of said second period after said incoming time to produce a second quadrature amplitude of said second incoming signal;    calculating a second phase at said incoming time based on said second in-phase amplitude and said second quadrature amplitude;    summing said phase and said second phase; and    applying a second illumination to said image point in substantial proportion to said second phase.    
     
     
         23 . The method of beam-forming for ultrasound imaging of  claim 18 , comprising further amplifying said outgoing signal.  
     
     
         24 . The method of beam-forming for ultrasound imaging of  claim 18 , comprising further an operation selected from the group consisting of: 
 amplifying said incoming signal,    pre-amplifying said incoming signal, and    storing said incoming signal.    
     
     
         25 . The method of beam-forming for ultrasound imaging of  claim 18 , comprising further repeating the method of beam-forming to produce a plurality of image points forming an image.  
     
     
         26 . The method of beam-forming for ultrasound imaging of  claim 25 , comprising further an operation selected from the group consisting of: 
 viewing said image,    guiding insertion of a needle based on said image,    guiding insertion of a catheter based on said image,    guiding insertion of an endoscope based on said image,    estimating blood flow based on said image, and    estimating tissue motion based on said image.    
     
     
         27 . The method of beam-forming for ultrasound imaging of  claim 25 , further comprising focusing said plurality of image points.  
     
     
         28 . The method of beam-forming for ultrasound imaging of  claim 25 , wherein said focusing is repeated on said reflected outgoing ultrasound at said plurality of image points.  
     
     
         29 . The method of beam-forming for ultrasound imaging of  claim 25 , wherein the plurality of image points are along a line at a range of interest.  
     
     
         30 . The method of beam-forming for ultrasound imaging of  claim 29 , wherein the line is formed at a plurality of ranges to form a planar image.  
     
     
         31 . The method of beam-forming for ultrasound imaging of  claim 30 , wherein the planar image is a B-mode image.  
     
     
         32 . The method of beam-forming for ultrasound imaging of  claim 25 , wherein the plurality of image points lie within a plane at a range of interest.  
     
     
         33 . The method of beam-forming for ultrasound imaging of  claim 32 , wherein the plurality of image points form a C-scan.  
     
     
         34 . The method of beam-forming for ultrasound imaging of  claim 32 , wherein the plane is formed at multiple ranges.  
     
     
         35 . The method of beam-forming for ultrasound imaging of  claim 32 , wherein the planes form a complex 3D image.  
     
     
         36 . The method of beam-forming for ultrasound imaging of  claim 18 , wherein an envelope of the magnitude is displayed.  
     
     
         37 . The method of beam-forming for ultrasound imaging of  claim 18 , further comprising compensating for a path difference based on the phase.  
     
     
         38 . The method of beam-forming for ultrasound imaging of  claim 18 , wherein a main lobe resolution and a side lobe level is balanced based on the magnitude.  
     
     
         39 . The method of beam-forming for ultrasound imaging of  claim 18 , wherein a sum squared error between a desired system response and a true system response is minimized.  
     
     
         40 . A system for beam-forming for ultrasound imaging, comprising: 
 means for generating an outgoing signal having an outgoing amplitude at an outgoing time;    means for transducing said outgoing signal to outgoing ultrasound;    means for transducing at least a portion of reflected outgoing ultrasound to an incoming signal having a period;    means for sampling said incoming signal at an incoming time and outputting an in-phase amplitude of said incoming signal;    means for sampling said incoming signal at substantially one-quarter of said period after said incoming time and outputting a quadrature amplitude of said incoming signal;    means for calculating a phase at said incoming time, based on said in-phase amplitude and said quadrature amplitude and outputting said phase; and    means for applying a second illumination to said image point in substantial proportion to said phase;    means for calculating a magnitude at said incoming time, based on said in-phase amplitude and said quadrature amplitude and outputting said magnitude;    means for measuring a difference between an outgoing amplitude of said outgoing signal and said magnitude; and    means for applying a first illumination to a image point in substantial proportion to said difference.    
     
     
         41 . The system for beam-forming for ultrasound imaging of  claim 40 , comprising further: 
 second means for transducing said outgoing signal to second outgoing ultrasound;    second means for transducing said reflected outgoing ultrasound and second outgoing ultrasound to a second incoming signal having a second period;    second means for sampling said second incoming signal at said incoming time and outputting a second in-phase amplitude of said second incoming signal;    second means for sampling said second incoming signal at substantially one-quarter of said second period after said incoming time and outputting a second quadrature amplitude of said second incoming signal;    second means for calculating a second phase at said incoming time based on said second in-phase amplitude and said second quadrature amplitude and outputting said second phase;    second means for summing said difference, said second difference, said phase, and said second phase; and    second means for applying a fourth illumination to said image point in substantial proportion to said second phase.    
     
     
         42 . The system for beam-forming for ultrasound imaging of  claim 40 , comprising further means for amplifying said outgoing signal.  
     
     
         43 . The system for beam-forming for ultrasound imaging of  claim 40 , comprising further means for amplifying said incoming signal.  
     
     
         44 . The system for beam-forming for ultrasound imaging of  claim 40 , comprising further means for pre-amplifying said incoming signal.  
     
     
         45 . The system for beam-forming for ultrasound imaging of  claim 40 , comprising further means for storing said incoming signal.  
     
     
         46 . The system for beam-forming for ultrasound imaging of  claim 40 , comprising further means for viewing an image comprising said image point.  
     
     
         47 . The system for beam-forming for ultrasound imaging of  claim 40 , comprising further means for guiding insertion of a needle, a catheter, or an endoscope based on an image comprising said image point.  
     
     
         48 . An ultrasound beamformer apparatus, comprising: 
 a signal generator for producing an outgoing signal having an outgoing amplitude at an outgoing time;    a transducer for converting said outgoing signal to outgoing ultrasound;    a plurality of transducers for converting at least a portion of said outgoing ultrasound that is reflected to incoming signals, said incoming signals having oscillations in time;    a plurality of signal receivers for converting each of said incoming signals to a pair, or time series of pairs of in phase and quadrature samples; and    a focusing apparatus for combining said in phase and quadrature samples to yield a focused in phase/quadrature sample.    
     
     
         49 . The ultrasound beamformer apparatus of  claim 48 , wherein: 
 complex demodulated echo data obtained from a single range from each transducer array element are sampled;    complex echo signals are multiplied by complex weightings; and    the results are summed to focus at a specific point at the range of interest.    
     
     
         50 . The ultrasound beamformer apparatus of  claim 48 , wherein: 
 the complex demodulation is performed using an analog demodulation circuit on each element.    
     
     
         51 . The ultrasound beamformer apparatus of  claim 48 , wherein: 
 the complex demodulation is performed by sampling the incoming signal at two points separated in time by approximately ¼ of a period.    
     
     
         52 . The ultrasound beamformer apparatus of  claim 48 , wherein: 
 the complex demodulation is performed via digital means.    
     
     
         53 . The ultrasound beamformer apparatus of  claim 48 , wherein: 
 the focusing operation is repeated on the same set of echo data at a plurality of points to form complex image data at that range.    
     
     
         54 . The ultrasound beamformer apparatus of  claim 53 , wherein: 
 the plurality of image points are along a line at the range of interest.    
     
     
         55 . The ultrasound beamformer apparatus of  claim 53 , wherein: 
 the plurality of image points lie within a plane at the range of interest and thereby form a complex c-scan.    
     
     
         56 . The ultrasound beamformer apparatus of  claim 53 , wherein: 
 the process of forming image lines is repeated at numerous ranges to form a planar ultrasound image, possibly being a b-mode image.    
     
     
         57 . The ultrasound beamformer apparatus of  claim 53 , wherein: 
 the process of forming image planes is repeated at multiple ranges to form a complex 3D image.    
     
     
         58 . The ultrasound beamformer apparatus of  claim 48 , wherein: 
 the envelope of the magnitude of the complex image is taken for display to the user.    
     
     
         59 . The ultrasound beamformer apparatus of  claim 48 , wherein: 
 the phases of the complex weightings used for focusing are determined so as to compensate for path length differences between different transducer array elements and the focal point.    
     
     
         60 . The ultrasound beamformer apparatus of  claim 48 , wherein: 
 the magnitude of applied complex weightings are selected to maintain a reasonable balance between main-lobe resolution and side-lobe levels in the system response.    
     
     
         61 . The ultrasound beamformer apparatus of  claim 48 , wherein: 
 the complex weightings used for focusing are determined so as to minimize the sum squared error between some desired system response and the true system response following the method described by Ranganathan and Walker in “A Novel Beamformer Design Method for Medical Ultrasound: Part I: Theory” a paper in press for IEEE Trans. Ultrason. Ferroelec. Freq. Contr.    
     
     
         62 . The ultrasound beamformer apparatus of  claim 48 , wherein: 
 the transducer array employed for imaging consists of a plurality of array elements transducer elements placing in a linear configuration selected from the group consisting of:    a linear array,    a phased array, and    a curvilinear array.    
     
     
         63 . The ultrasound beamformer apparatus of  claim 48 , wherein: 
 the transducer array employed for imaging consists of a plurality of elements arranged in an unequally sampled 2D configuration or a 1.5-D array.    
     
     
         64 . The ultrasound beamformer apparatus of  claim 48 , wherein: 
 the transducer array employed for imaging consists of a plurality of elements that are placed in an equally sampled 2D configuration.    
     
     
         65 . The ultrasound beamformer apparatus of  claim 64 , wherein a fraction of the elements of the array are utilized such that the resulting array is a sparse 2D array.  
     
     
         66 . The ultrasound beamformer apparatus of  claim 64 , wherein: 
 all elements of the array are utilized such that the resulting array is a fully sampled 2D array.    
     
     
         67 . The ultrasound beamformer apparatus of  claim 48 , wherein: 
 connections are made to individual array elements such that individual elements may be used for either transmission or reception, but not both, thereby eliminating the need for receive protection circuitry.    
     
     
         68 . The ultrasound beamformer apparatus of  claim 48 , wherein: 
 only a fraction of elements are used to form any given image point.    
     
     
         69 . The ultrasound beamformer apparatus of  claim 48 , wherein: 
 the focusing operation is repeated for different fractions of the aperture thereby obtaining multiple redundant views of the same target location.    
     
     
         70 . The ultrasound beamformer apparatus of  claim 48 , wherein: 
 the multiple looks are averaged after taking their magnitudes so as to reduce the appearance of speckle in the resulting image.    
     
     
         71 . The ultrasound beamformer apparatus of  claim 48 , wherein: 
 the complex image points are used over successive acquisitions to estimate blood flow or tissue motion.    
     
     
         72 . The ultrasound beamformer apparatus of  claim 48 , wherein: 
 the sampling operation is performed at multiple ranges for a single transmit event, thereby increasing the image formation rate.