Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
1999-02-17
2001-05-08
Jaworski, Francis J. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
Reexamination Certificate
active
06228031
ABSTRACT:
This invention relates to ultrasonic diagnostic imaging systems and, in particular, to ultrasonic diagnostic imaging systems capable of producing high frame rate ultrasonic images with reduced motion artifacts.
U.S. Pat. No. 5,706,819 describes a signal processing technique which separates fundamental and harmonic signal components in received ultrasonic echo signals. This technique, known in ultrasound as “pulse inversion,” is a two pulse technique in which two pulses of opposing polarity (phase) are successively transmitted to the same location in the body. Echoes are received following each transmission in which fundamental signal components are out of phase due to the opposing polarity of the transmit pulses, but the higher order harmonic signal components, being quadratic in nature, are not. Summing the two echoes will cancel the opposing fundamental components and reinforce the harmonic components, leaving a cleanly separated harmonic signal without the need for conventional filters. Subtracting the two echoes will have the opposite result, canceling the harmonic signal components and reinforcing the fundamental (linear) signal components. In a similar manner, subtraction leaves a cleanly separated fundamental echo signal.
Pulse inversion is a two pulse technique, however, meaning it is necessary to scan each acoustic line twice in order to form a single image. This means that the time required to acquire all of the scanlines of an image is approximately doubled as compared to conventional single pulse imaging. The time to acquire all of the scanlines of an image frame determines the frame rate of display, which will approximately halve with a two pulse technique. It is desirable to have as high a frame rate as possible so that realtime imaging is produced which shows tissue motion smoothly and with little interframe discontinuity as a scanhead is moved when surveying a patient's anatomy.
In a concurrently filed application it is shown how pulse inversion harmonic imaging can be carried out at a high frame rate of display and a high line density. In one embodiment of that inventive technique transmit pulses of opposing polarity (phase) are transmitted along transmit scanlines at adjacent positions in the image field and multiple scanlines are received in response to each transmitted beam. Received scanlines from opposite polarity pulses are combined to produce harmonic images at a high frame rate of display. By combining received scanlines in a temporally consistent manner, motion artifacts are reduced. In the present invention, this principle is applied to reduce motion artifacts when performing r.f. interpolation of multiline scanlines. The inventive system employs a multiline beamformer which receives and forms multiple received scanlines in response to a single beam transmission. Interpolated scanline image data is produced by interpolating temporally different scanline data for each image line. The image data is then used to form an ultrasonic image. The scintillation effect of motion is eliminated by the use of temporally different scanline data to form each image line.
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Hwang Juin-Jet
Robinson Brent Stephen
ATL Ultrasound
Jaworski Francis J.
Yorks, Jr. W. Brinton
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