Acuson Corporation

Brian M Normand

Ismayil M Guracar

J Nelson Wright

David J Finger

Jay Sterling Plugge

Donald R Langdon

D Grant Fash, Iii

Stirling S Dodd

A patient is first injected with a contrast agent. A complete scan along a plurality of scan lines is then performed, resulting in the destruction of some contrast agent. While some of the contrast agent is destroyed, non-scanned portions of the target, and possibly the scan region, still include at least some contrast agent. A second scan is then sequentially performed sufficiently close in time to the first scan such that reflections from the anatomy remain unchanged. The second frame of data from the second scan will differ from the first frame of data from the first scan by only contrast agent effects. The second frame of data is subtracted from the first frame of data. The resulting data is used to image the contrast agent. By varying the time between each pair of scans, differences in the speed of the contrast agent motion within the body may be assessed. The collateral damage of contrast agents from ultrasound acoustic energy is minimized while the degradation due to various changes is also minimized.

Diagnostic medical ultrasonic system and method for image subtraction

The invention provides a method and system for adaptive persistence processing in an ultrasound imaging system. Acoustic signals are temporally filtered using an adaptive persistence filter, having a recursive stage followed by a nonrecursive stage. A set of filtering coefficients for each stage are supplied by a look-up table in a memory, addressed or indexed in response to a plurality of input or output pixel values. The look-up table may therefore embody any selected function of its input variables. The input variables for the look-up table function are a current input pixel value X.sub.n and a previous intermediate pixel value W.sub.n-1, and the function embodied by the look-up table includes a relative first difference function for selecting a filter coefficient. A recursive filtering coefficient .alpha. is held constant over time, while a nonrecursive filtering coefficient .gamma.is adjusted dynamically in response to the current input pixel value X.sub.n and the previous intermediate pixel value W.sub.n-1. The non-recursive stage filter has a frequency response that attenuates higher frequency components without attenuating a broad range of lower frequency components, relative to the recursive stage frequency response. The step response or settling time of the non-recursive stage filter always spans one frame interval, independent of the nonrecursive filtering coefficient, while the step response or settling time for the recursive stage filter is generally longer and is dependent on the recursive filtering coefficient.

Adaptive persistence processing

The invention provides a method and system for adaptive persistence processing in an ultrasound imaging system. Acoustic signals are temporally filtered using an adaptive persistence filter, having a recursive stage followed by a nonrecursive stage. A set of filtering coefficients for each stage are supplied by a look-up table in a memory, addressed or indexed in response to a plurality of input or output pixel values. The look-up table may therefore embody any selected function of its input variables. The input variables for the look-up table function are a current input pixel value X.sub.n and a previous intermediate pixel value W.sub.n-1, and the function embodied by the look-up table includes a relative first difference function for selecting a filter coefficient. A recursive filtering coefficient .alpha. is held constant over time, while a nonrecursive filtering coefficient .gamma. is adjusted dynamically in response to the current input pixel value X.sub.n and the previous intermediate pixel value W.sub.n-1. The nonrecursive stage filter has a frequency response that attenuates higher frequency components without attenuating a broad range of lower frequency components, relative to the recursive stage frequency response. The step response or settling time of the nonrecursive stage filter always spans one frame interval, independent of the nonrecursive filtering coefficient, while the step response or settling time for the recursive stage filter is generally longer and is dependent on the recursive filtering coefficient.

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San Ramon, CA, United States of America

Brian M Normand