Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
1999-10-08
2001-11-13
Lateef, Marvin M. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
68, C600S448000, C600S449000, C600S455000, C600S458000, C600S443000
Reexamination Certificate
active
06315723
ABSTRACT:
This invention relates to ultrasonic diagnostic imaging systems and, in particular, to ultrasonic diagnostic imaging systems which synthesize transmit focal zones.
Conventional ultrasonic diagnostic imaging systems utilize dynamic focus during beam formation to dynamically vary the focal range of received ultrasonic echoes as the echoes are received. This capability is made possible by the ability to continually change the delays applied to echoes received from different elements of a transducer array as the echoes are received, thereby continually changing the focal range of the transducer array's receive aperture. The effective curvature of the receive aperture is constantly made more gradual to progressively focus the transducer array at increasing ranges as echoes are received from ever-increasing depths following a transmit wave.
Such a dynamic focus capability is not possible during transmit, however. A transmitted beam can be focused at only one range by selectively delaying the application of transmit pulses across the aperture, with elements at the center of the array transducer experiencing delayed excitation in relation to elements located toward the lateral extremes of the transmit aperture. Once the transmit wave has been launched, it is not possible for the ultrasound system to modify or adjust its focus. Various techniques have been tried to effect a focal region at different or more extended depths such as focusing different elements of the array at different depths, combining multiple transmit pulses in a single transmission, encoding different frequency components to focus at different depths, and lateral deconvolution. All of these techniques have met with mixed success, complexity and/or compromise.
A conventional technique for dealing with the single focal characteristic of the transmit beam is what is known as multi-zone focus. In multi-zone focus each beam location is interrogated multiple times, with each transmission focused at a different transmit depth. During reception echoes are received around the focal range of each unique transmit beam, thereby acquiring segments of a complete receive scanline from different depth ranges. The segments are then spliced together to form a complete scanline is for an image. A problem which always presents itself in multi-zone focusing is how to smoothly fit one segment into another. One solution has been to “butt-fit” segments together by truncating the beginning and ending of adjoining segments at a predetermined depth, as shown in U.S. Pat. No. 4,505,296. Another solution has been to overlap the ends of adjoining segments and cross-fade from one segment to another as described in U.S. Pat. Nos. 5,568,813 and 5,579,770. These solutions all require an extensive degree of care to prevent visible seams in the image where the segments from different depths are joined or blended together. It would be desirable to be able to improve the transmit focal characteristics of an ultrasound system so that the system can focus a transmit beam over a greater range of depths without seam artifacts during multi-zone operation, and desirably without the need for a large number of focal zones which reduces the frame rate of display.
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Cooley Clifford R.
Robinson Brent Stephen
Sabourin Thomas J
ATL Ultrasound
Lateef Marvin M.
Patel Maulin
Yorks, Jr. W. Brinton
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