Ultrasonic tissue imaging method and apparatus with doppler velocity and acceleraton processing

Abstract

An ultrasound tissue imaging system having an acoustic transducer, B-mode imaging means to produce with said transducer an electronically scanned B-mode image of tissue under examination. Doppler imaging means that accepts and processes large amplitude, low frequency signals to produce with said transducer an electronically scanned acoustic image of moving tissue, and color display means for displaying the B-mode image as a two-dimensional image with echo intensities encoded using a first mapping function and for simultaneously displaying Doppler information from moving tissue as a two-dimensional image using a second and distinct mapping function that is spatially coordinated with and superimposed upon said B-mode image to augment the B-mode image.

We claim: 
     
       1. An ultrasound tissue imaging system having an acoustic transducer and comprising B-mode imaging means to produce with said transducer an electronically scanned B-mode image of tissue under examination, said B-mode image substantially representing the intensity of echoes returned from said tissue along multiple B-mode scan lines;   Doppler imagine means that accepts and processes large amplitude, low frequency signals to produce with said transducer an electronically scanned Doppler image of said moving tissue, the Doppler image representing estimates of velocity including means, standard deviation or energy derived from Doppler-shifted echoes reflected from said moving tissue at multiple sample volumes along multiple Doppler scan lines;   color display means for displaying the B-mode image as a two-dimensional image with echo intensities encoded using a first mapping function and for augmenting the B-mode image by simultaneously displaying said estimates of velocity, as a two-dimensional Doppler image using a second and distinct mapping function that is spatially coordinated with and superimposed upon said b-mode image.   
     
     
       2. The system of claim 1 further comprising means for estimating acceleration from said estimates of velocity and means for displaying estimates of that acceleration as the two-dimensional Doppler image using said second mapping function. 
     
     
       3. The system of claim 1 wherein the B-mode image is gated to the display by gate means only upon detection of said acquired and processed Doppler information so as to remove stationary noise and clutter. 
     
     
       4. The system of claim 1 wherein the second mapping function color maps the magnitude of forward and reverse motion without distinguishing direction of the motion. 
     
     
       5. The system of claim 1 wherein the second mapping function grey-scale maps the Doppler information. 
     
     
       6. A method of forming a composite B-mode and color Doppler acoustic image of moving tissue by transmitting acoustic pressure waves and receiving returned echoes on acoustic lines scanned by a transducer, said method comprising the steps of deriving a B-mode image from echoes received along a first set of image scan lines,   acquiring and processing color Doppler information at large amplitude and low frequencies from said moving tissue at multiple volumes along scan lines that are the same as or propagated independently from the B-mode scan lines and   displaying said color Doppler information as a two-dimensional color coded image of moving tissue that is spatially coordinated with and superimposed upon said B-mode image.   
     
     
       7. The method of claim 6 wherein the step of acquiring and processing color Doppler information further includes deriving estimates of acceleration for Doppler shifted echoes and displaying those estimates as the two-dimensional color coded image of said moving tissue. 
     
     
       8. The method of claim 6 wherein the display of said B-mode image is gated by said color Doppler information. 
     
     
       9. An ultrasound tissue imaging system having an acoustic transducer and comprising B-mode imaging means to produce with said transducer an electronically scanned B-mode image of tissue under examination, said B-mode image substantially representing the intensity of echoes returned from said tissue along multiple B-mode scan lines;   imaging means that accepts and processes large amplitude, low frequency signals to produce with said transducer an electronically scanned Doppler image of said moving tissue, the image representing estimates of velocity derived from echoes reflected from said moving tissue at multiple sample volumes along multiple scan lines;   color display means for displaying the B-mode image as a two-dimensional image with echo intensities encoded using a first mapping function and for augmenting the B-mode image by simultaneously displaying said estimates of velocity as a two-dimensional Doppler image using a second and distinct mapping function that is spatially coordinated with and superimposed upon said B-mode image.   
     
     
       10. The system of claim 9 further comprising means for estimating acceleration from said estimates of velocity and means for displaying estimates of that acceleration as the two-dimensional image using said second mapping function. 
     
     
       11. The system of claim 10 wherein the second mapping function color maps at a low non-zero value estimates of acceleration derived from estimates of velocity when those velocities are the same but also are non-zero. 
     
     
       12. The system of claim 9 wherein the blood pool/myocardium borders are enhanced by gating the B-mode image to the display means only in the presence of acquired and processed Doppler information. 
     
     
       13. A method of forming a color Doppler acoustic image of moving tissue by transmitting acoustic pressure waves and receiving returned echoes on acoustic lines scanned by a transducer, said method comprising the steps of acquiring and processing color Doppler information at large amplitude and low frequencies from said moving tissue at multiple volumes along a plurality of scan lines and   displaying said color Doppler information as a two-dimensional color coded image of said moving tissue. .Iadd.   
     
     
       14.  The method of claim 13 wherein said displaying step displays said color Doppler information by assigning no color to color Doppler information associated with a lowest velocity..Iaddend..Iadd.15. The method of claim 14 further comprising the step of varying a sampling rate of the color Doppler information in the acquiring and processing step..Iaddend..Iadd.16. The method of claim 13 wherein said acquiring and processing step comprises the step of supplying an output signal of a Doppler detector to a Doppler signal analyzer without filtering between the Doppler detector and the Doppler signal analyzer..Iaddend..Iadd.17. The method of claim 6 or 13 wherein the Doppler information comprises Doppler energy information..Iaddend..Iadd.18. The method of claim 6 or 13 wherein the Doppler information comprises Doppler acceleration information..Iaddend..Iadd.19. The system of claim 1 or 9 wherein the second mapping function assigns no color to a lowest estimate of velocity..Iaddend..Iadd.20. The method of claim 6 wherein said acquiring and processing step processes color Doppler information indicative of velocity of said moving tissue, and wherein said displaying step comprises the step of assigning no color to portions of the image associated with moving tissue having a lowest velocity..Iaddend..Iadd.21. The method of claim 20 further comprising the step of varying a sampling rate of the color Doppler information in the acquiring and processing step..Iaddend..Iadd.22. An ultrasound tissue imaging system having an acoustic transducer and comprising: a receiver/beamformer coupled to the transducer;   a Doppler detector coupled to the receiver/beamformer;   a Doppler signal analyzer coupled to the Doppler detector without filtering between the Doppler detector and the Doppler signal analyzer, said Doppler signal analyzer processing color Doppler information at large amplitude and low frequencies from moving tissue at multiple volumes along a plurality of scan lines; and   a display system coupled to the Doppler signal analyzer, said display system operative to display said color Doppler information as a two-dimensional color coded image of said moving tissue..Iaddend..Iadd.23. The system of claim 22 wherein the display system comprises a color mapping function that assigns no color to the volumes characterized by a lowest velocity..Iaddend..Iadd.24. An ultrasound tissue imaging system having an acoustic transducer and comprising:   means for acquiring and processing color Doppler information at large amplitude and low frequencies from moving tissue at multiple volumes along a plurality of scan lines; and   means for displaying said color Doppler information as a two-dimensional color coded image of said moving tissue..Iaddend..Iadd.25. The system of claim 24 wherein said means for acquiring and processing comprises:   a receiver/beamformer coupled to the transducer;   a Doppler detector coupled to the receiver/beamformer; and   a Doppler signal analyzer coupled to the Doppler detector without filtering between the Doppler detector and the Doppler signal analyzer..Iaddend..Iadd.26. The system of claim 24 wherein the display means comprises means for assigning no color to the volumes characterized   
     
     
        by a lowest velocity..Iaddend..Iadd.27.  A method for displaying a B-mode image of moving tissue by transmitting acoustic pressure waves and receiving returned echos on acoustic lines scanned by a transducer, said method comprising the following steps: deriving a B-mode image from echoes received along a first set of image scan lines;   acquiring Doppler information from said moving tissue at multiple volumes along scan lines that are the same as or propagated independently from the B-mode scan lines; and   gating the B-mode image with the Doppler information..Iaddend..Iadd.28. The method of claim 27 comprising the further step of displaying the gated B-mode image..Iaddend..Iadd.29. The method of claim 27 wherein the acquiring step comprises the step of acquiring and processing Doppler information at large amplitude and low frequencies from said moving tissue..Iaddend..Iadd.30. An ultrasound tissue imaging system having an acoustic transducer and comprising:   a receiver/beamformer coupled to the transducer;   a B-mode imaging system operative with the transducer to produce electronically scanned B-mode image information of tissue under examination;   a Doppler information acquiring system operative with the transducer to acquire Doppler information from said tissue;   a B-mode gate responsive to the B-mode imaging system and to the Doppler information acquiring system to produce a gated output signal, wherein the gated output signal corresponds to the B-mode image information gated by the Doppler information..Iaddend..Iadd.31. The system of claim 30 further comprising a display coupled to the B-mode gate to display the gated   
     
     
        output signal..Iaddend..Iadd.32.  The system of claim 30 wherein the Doppler information acquiring system comprises a Doppler detector and a Doppler signal analyzer coupled to the Doppler detector without any substantial filtering therebetween, said Doppler signal analyzer being responsive to large amplitude, low frequencies signals from said 
     
     
        tissue..Iaddend..Iadd.33.  The system of claim 22, 24 or 30 wherein the Doppler information comprises Doppler energy 
     
     
        information..Iaddend..Iadd.     The system of claim 22, 24 or 30 wherein the Doppler information comprises Doppler acceleration information..Iaddend.