Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
1999-08-09
2001-10-30
Lateef, Marvin M. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
Reexamination Certificate
active
06309357
ABSTRACT:
BACKGROUND
This invention relates to a medical diagnostic ultrasound system and method for imaging blood flow or tissue movement. In particular, clutter filtering for flow or movement imaging is provided.
Ultrasound systems image blood flow and tissue movement using correlation or Doppler techniques. The flow or movement is represented by one or more of various estimated parameters, such as energy, velocity and/or variance. Prior to estimation of these parameters, a clutter filter may suppress undesired signals, such as associated with reflections of ultrasonic energy from stationary or slowly moving tissue.
The clutter filter response is typically selected as a compromise between low flow or movement sensitivity, clutter suppression, and the number of taps for the clutter filter. A large number of taps allows filters with a sharper magnitude versus frequency rolloff, more efficiently isolating desired signals from undesired signals (i.e. better differentiation between flow or movement and clutter). The large number of taps allows for better sensitivity to low velocity flow or movement. The large number of taps also allows for filtering with a flat frequency passband, providing more desirable sensitivity over a larger range of velocities.
However, more line firings are required for more taps. A larger number of line may reduce the frame rate for imaging.
U.S. Pat. No. 5,249,578 to Karp et al. teaches processing data with different finite impulse response filters where the different filters are defined as having reversed coefficients. The magnitude versus frequency response of these two filters is the same. By using these two filters, a greater number of independent samples may reduce the variance of velocity estimation.
BRIEF SUMMARY
The present invention is defined by the following claims, and nothing in this section should be taken as a limitation on those claims. By way of introduction, the preferred embodiment described below includes a method and system for flow or movement detection. More than one clutter filter is used. Each clutter filter is optimized differently. Estimates of the flow or movement are generated from the data output by each of the clutter filters. Using selection or combination of the resulting estimates, the best attributes of each filter are used for imaging.
In one aspect, a medical diagnostic ultrasound system for estimating flow or movement is provided. The system includes first and second clutter filters. The first clutter filter is characterized by a magnitude versus frequency response different than the second clutter filter. A combiner is operatively connected to receive first and second estimates. The first and second estimates are responsive to the first and second clutter filters, respectively. The combiner is operable to combine the first and second estimates. In other aspects, the combiner is replaced with a selector. The selector is operable to select one of the first and second estimates.
In another aspect, a medical diagnostic ultrasound method for estimating flow or movement is provided. The method includes the steps of filtering with a first clutter filter and filtering with a second clutter filter where the first clutter filter is characterized by a magnitude versus frequency response different than the second clutter filter. First and second estimates are estimated from data from the first and second clutter filters, respectively. The first and second estimates are combined, or one of the first and second estimates is selected.
REFERENCES:
patent: 5152292 (1992-10-01), Karp
patent: 5249578 (1993-10-01), Karp et al.
patent: 5349524 (1994-09-01), Daft et al.
patent: 5544659 (1996-08-01), Banjanin
patent: 5609155 (1997-03-01), Guracar
patent: 5664575 (1997-09-01), Banjanin et al.
patent: 5709210 (1998-01-01), Green et al.
patent: 5846202 (1998-12-01), Ramamurthy et al.
patent: 5860930 (1999-01-01), Guracar
Guracar Ismayil M.
Phillips Patrick J.
Acuson Corporation
Brinks Hofer Gilson & Lione
Lateef Marvin M.
Patel Maulin
Summerfield Craig A.
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