Ultrasound ARFI Displacement Imaging Using an Adaptive Time Instance

Abstract

In ARFI imaging, a cost function is used to identify a time of displacement that best or sufficiently indicates the desired information. For example, the displacements associated with a combination of contrast and signal-to-noise ratio are identified. The time at which the desired displacements occur may be other than the time of the maximum. Since the time is common to displacements for one or more scan lines, the displacement image may be assembled line-by-line or by groups of lines.

1 . A method for acoustic radiation force impulse (ARFI) imaging, the method comprising:
 measuring, with an ultrasound system, displacements over different times at a plurality of locations within a patient in response to an impulse excitation;   determining contrasts for the displacements at each of the times;   determining signal-to-noise ratios for the displacements at each of the times;   selecting a first one of the times as a function of the contrasts and the signal-to-noise ratios; and   generating an ARFI image with the displacements of the selected first time.   
     
     
         2 . The method of  claim 1  further comprising:
 transmitting an acoustic excitation into a patient, the impulse excitation comprising the acoustic excitation; 
 wherein measuring the displacements over the different times comprises repetitively scanning with ultrasound. 
 
     
     
         3 . The method of  claim 1  wherein measuring the displacement comprises transmitting ultrasound to the tissue and receiving reflections from the transmitting, the transmitting the ultrasound and receiving being repeated for the different times, and detecting the displacements from the reflections of the multiple receiving from multiple locations. 
     
     
         4 . The method of  claim 1  wherein measuring comprises measuring the displacements along a scan line. 
     
     
         5 . The method of  claim 4  further comprising repeating the measuring, determining contrasts, determining signal-to-noise ratios and selecting for additional scan lines, where generating the ARFI image comprises generating from the displacements of the scan line and the additional scan lines of the respective selected times including the first time. 
     
     
         6 . The method of  claim 1  wherein determining contrasts for the displacements at each of the times comprises subtracting a minimum of the displacements for each time from a respective maximum of the displacements for the respective time. 
     
     
         7 . The method of  claim 1  wherein determining the signal-to-noise ratios comprises:
 filtering the displacements over the locations for each time; 
 subtracting the filtered displacements from the displacements for each time; 
 dividing the displacements by a result of the subtracting. 
 
     
     
         8 . The method of  claim 1  wherein selecting comprises selecting the first time as the time with a maximum of the contrast multiplied by the signal-to-noise ratio. 
     
     
         9 . The method of  claim 1  wherein selecting comprises selecting with a cost function including the contrasts and signal-to-noise ratios as input variables. 
     
     
         10 . The method of  claim 1  wherein generating comprises generating the ARFI image with the displacements being other than maximum displacements over the different times. 
     
     
         11 . The method of  claim 1  wherein generating comprises generating the ARFI image with the displacements of the first time. 
     
     
         12 . The method of  claim 1  wherein generating comprises generating the ARFI image as a blend of a maximum displacement and the displacements of the first time. 
     
     
         13 . In a non-transitory computer readable storage medium having stored therein data representing instructions executable by a programmed processor for acoustic radiation force impulse (ARFI) imaging, the storage medium comprising instructions for:
 determining displacements at multiple times;   calculating quality levels of the displacements for the times with a cost function;   identifying one of the times based on the quality levels; and   outputting an image with display values responsive to the displacements of the one time.   
     
     
         14 . The non-transitory computer readable storage medium of  claim 13  wherein determining the displacements at multiple times comprises repetitively determining displacements along a scan line, each repetition corresponding to different instances of the multiple times, wherein the determining, calculating, and identifying are performed repetitively for additional scan lines, and wherein outputting the image comprises outputting the image representing a planar region with different image lines corresponding to the displacements of the identified times in each repletion of the determining, calculating, and identifying. 
     
     
         15 . The non-transitory computer readable storage medium of  claim 13  wherein determining the displacements for each of the multiple times comprises determining a magnitude of displacement for each of different locations after an impulse causing displacement of tissue in the patient. 
     
     
         16 . The non-transitory computer readable storage medium of  claim 13  wherein calculating the quality levels comprises calculating as a function of a contrast and signal-to-noise ratio of the displacements for each of the times. 
     
     
         17 . The non-transitory computer readable storage medium of  claim 13  wherein identifying comprises identifying the one time corresponding to the displacements with a highest quality level of the quality levels. 
     
     
         18 . The non-transitory computer readable storage medium of  claim 13  wherein outputting comprises displaying the image as a combination of maximum displacements and the displacements of the one time. 
     
     
         19 . A system for acoustic radiation force impulse (ARFI) imaging, the system comprising:
 a transducer configured to transmit a first acoustic impulse excitation into a patient, to scan with ultrasound a first line of the patient, to transmit a second acoustic impulse excitation into the patient, and to scan with ultrasound a second line of the patient;   a receive beamformer configured to generate data representing the first and second lines at different times relative to the first and second acoustic impulse excitations, respectively, the data generated from the scans with ultrasound;
 a processor configured to estimate tissue displacement in the first and second lines induced by the first and second acoustic impulse excitations at each of the different times and configured to select a first of the different times for the tissue displacements in the first line and to select a second of the different times for the tissue displacements in the second line, the first time a different amount of time after the first acoustic impulse excitation than the second time after the second acoustic impulse excitation; and 
 a display configured to display an image representing the displacements of the first time for the first line and of the second time for the second line. 
   
     
     
         20 . The system of  claim 19  wherein the processor is configured to select as a function of contrast-to-noise ratio, entropy, texture, statistical moment, signal-to-noise ratio, or combinations thereof of the tissue displacements for the different times.