System and method for ultrasound color doppler imaging

Abstract

Systems and methods for color Doppler imaging in an ultrasound imaging system are disclosed herein. An ultrasound imaging system includes color Doppler imaging circuitry. The color Doppler imaging circuitry is configured to estimate flow parameters. The imaging circuitry includes a radio frequency (“RF”) demodulator configured to produce in-phase and quadrature components of an ultra-sound data vector. The RF demodulator includes a table in memory that stores interleaved sine and cosine values. The RF demodulator maintains an index value for the table having higher precision than is used to index the table. The RF demodulator rounds the index value for each access of the table. Each table access retrieves a sine value and a cosine value.

1 . An ultrasound imaging system, comprising:
 color Doppler imaging circuitry configured to estimate flow parameters, the imaging circuitry comprising:
 a radio frequency (“RF”) demodulator configured to produce in-phase and quadrature components of an ultra-sound data vector;
 wherein the radio frequency demodulator includes a table in memory storing interleaved sine and cosine values, and the radio frequency demodulator maintains an index value for the table having higher precision than is used to index the table, and rounds the index value for each access of the table, each table access retrieving a sine value and a cosine value. 
 
   
   
   
       2 . The ultrasound imaging system of  claim 1 , wherein the radio frequency demodulator comprises a decimator configured to decimate the ultra-sound data vector, and an outer loop and an inner loop of the decimator are unrolled. 
   
   
       3 . The ultrasound imaging system of  claim 2 , wherein the decimator consumes at least four filter coefficients and processes at least two depth points in parallel with each iteration of the inner loop. 
   
   
       4 . The ultrasound imaging system of  claim 1 , wherein the color Doppler imaging circuitry further comprises a Wall filter configured to reduce vessel wall echoes, the Wall filter comprises a matrix of filter coefficients stored in memory, wherein the Wall filter retrieves a plurality of filter coefficients per access and applies the retrieved filter coefficients to a plurality of data values stored memory, wherein one of the filter coefficients and data values is stored column-wise and the other of the filter coefficients and data values is stored row-wise. 
   
   
       5 . The ultrasound imaging system of  claim 1 , wherein the color Doppler imaging circuitry comprises a flow estimator that computes a partial flow value and uses the partial flow value to compute a plurality of flow parameter values. 
   
   
       6 . The ultrasound imaging system of  claim 5 , wherein the flow parameter values comprise at least one of a flow parameter selected from a group consisting of flow power, flow velocity, and flow turbulence. 
   
   
       7 . The ultrasound imaging system of  claim 1 , wherein the RF demodulator mixes at least four RF points in parallel and outputs a complex output point per cycle. 
   
   
       8 . The ultrasound imaging system of  claim 1 , wherein the color Doppler imaging circuitry comprises a flow parameter estimator that computes flow power and correlation between adjacent ensemble points, wherein the flow parameter estimator comprises an inner loop and an outer loop and the outer loop is unrolled twice. 
   
   
       9 . The ultrasound imaging system of  claim 1 , wherein the imaging circuitry comprises:
 a processor; and   a memory coupled to the processor;   wherein the processor is configured to execute a color Doppler software system stored in the memory, and the color Doppler software system comprises instructions for performing RF demodulation, instructions for performing Wall filtering, and instructions for performing flow estimation.   
   
   
       10 . The ultrasound imaging system of  claim 1 , wherein the color Doppler imaging circuitry further comprises a Wall filter configured to reduce vessel wall echoes and including nesting processing loops wherein the innermost loop is completely unrolled. 
   
   
       11 . A method, comprising:
 fetching from ultrasound imaging system memory, in a single memory access cycle, a plurality of Wall filter coefficients;   applying the plurality Wall filter coefficients to a plurality of complex ultrasound data values in a single execution cycle; and   providing Wall filtered ultrasound data to a flow estimator.   
   
   
       12 . The method of  claim 11 , further comprising:
 fetching from a table stored in ultrasound imaging system memory, in a single memory access cycle, a sine value and a cosine value;   rounding an index value maintained at higher precision than is used to access the table to a precision used to access the table;   updating the index value at the higher precision; and   generating a complex ultrasound radio frequency (“RF”) data value by applying the sine and cosine value to an RF ultrasound data sample.   
   
   
       13 . The method of  claim 11 , further comprising demodulating ultrasound RF data using a nested processing loop wherein both inner and outer loops of the nested processing loop are unrolled. 
   
   
       14 . The method of  claim 11 , further comprising decimating complex ultrasound RF data wherein the decimation uses at least four anti-alias filter coefficients during each iteration of an inner filter loop. 
   
   
       15 . The method of  claim 11 , further comprising computing two-dimensional flow parameter estimates by storing a set of partial sum of powers values and computing a flow parameter value based on a stored partial sum of powers value. 
   
   
       16 . An ultrasound color Doppler imaging system, comprising:
 a processor; and   a software system for color Doppler imaging executed by the processor;   wherein the software system comprises instructions that when executed cause the processor to convert real radio frequency (“RF”) ultrasound samples to complex RF ultrasound samples using sine and cosine values stored in adjacent memory locations.   
   
   
       17 . The system of  claim 16 , wherein the processor is a very long instruction word (“VLIW”) processor. 
   
   
       18 . The system of  claim 17 , wherein the VLIW processor comprises a plurality of parallel data execution paths, each execution path comprising a plurality of execution units, each instruction of the software system being mapped to an execution unit. 
   
   
       19 . The system of  claim 16 , wherein the software system comprises instructions that when executed cause the processor to decimate the complex RF ultrasound samples. 
   
   
       20 . The system of  claim 19 , wherein the software system comprises instructions that when executed cause the processor to compute flow parameters from the decimated complex ultrasound samples, the computed flow parameters comprising at least one of flow power, flow turbulence, and flow velocity. 
   
   
       21 . The system of  claim 19 , wherein the software system comprises instructions that when executed cause the processor to filter vessel wall motion from the decimated complex ultrasound samples. 
   
   
       22 . The system of  claim 21 , wherein the ultrasound Doppler imaging system comprises a transpose Wall filter coefficient matrix stored in memory, and the software system causes the processor to fetch a plurality of Wall filter coefficients in a single access. 
   
   
       23 . The system of  claim 16 , wherein the software system comprises a plurality of nested processing loops and both an outer loop and an inner loop of at least one of the plurality of nested processing loops are unrolled. 
   
   
       24 . A color Doppler imaging system, comprising:
 circuitry that computes a sum of powers of a first ensemble and a sum of power of a second ensemble;   circuitry that stores the sum of powers of the first ensemble and the sum of powers of the second ensemble in memory;   circuitry that retrieves the sum of powers of the first ensemble and the sum of powers of the second ensemble from memory and computes a flow power parameter using the retrieved sums of powers.   
   
   
       25 . The color Doppler imaging system of  claim 24 , further comprising:
 circuitry that computes a correlation sum of a first ensemble and a correlation sum of a second ensemble;   circuitry that stores the correlation sum of the first ensemble and the correlation sum of the second ensemble in memory;   circuitry that retrieves the correlation sum of the first ensemble and the correlation sum of the second ensemble from memory and computes at least one of a flow velocity and a flow turbulence using the retrieved correlation sums.   
   
   
       26 . The color Doppler imaging system of  claim 24 , further comprising:
 circuitry that computes an correlation sum of depth points of a first set two different ensembles (CorrSum1) and a correlation sum of depth points of a second set of two different ensembles (CorrSum2);   circuitry that stores the CorrSum1 and the CorrSum2 in memory;   circuitry that retrieves the CorrSum1 and the CorrSum2 from memory and computes at least one of a flow velocity and a flow turbulence using the retrieved correlation sums.