Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2000-03-31
2003-01-07
Jaworski, Francis J. (Department: 3662)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C029S025350
Reexamination Certificate
active
06503204
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to ultrasonic transducer arrays for use in ultrasound imaging systems, and more particularly, to two-dimensional ultrasonic transducer arrays used for medical diagnostic ultrasonic imaging having transducer elements arranged in a non-rectangular or hexagonal grid, and ultrasound imaging systems employing same. Heretofore, ultrasonic transducer arrays have been manufactured having transducer elements fabricated and arranged in a rectangular grid. Such conventional transducer arrays are relatively costly because of a relatively high element count. Also, the elements of the conventional transducer arrays are not symmetrical such that they maximize the two-dimensional symmetry of the point spread function.
In the case of fully populated arrays, all of the transducer elements are connected to an ultrasound system. In the case of sparse (sparsely-populated) arrays, only some of the elements are connected to the ultrasound system. Sparse arrays include random arrays, vernier arrays and spiral arrays.
Conventional sparse arrays are described in the following references: R. E. Davidsen, J. A. Jensen, and S. W. Smith, “Two-dimensional random arrays for real time volumetric imaging”, Ultrasonic Imaging, vol. 16, pp. 143-163,1994, S. S. Brunke and G. R. Lockwood, entitled “Broad-Bandwidth Radiation Patterns of Sparse Two-Dimensional Vernier Arrays,” IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, vol. 44, no. 5, pp. 1101-1109,1997, U.S. Pat. No. 5,808,962, issued Sep. 15, 1998, entitled “Ultrasparse, ultrawideband arrays”, and U.S. Pat. No. 5,537,367 issued Jul. 16, 1996, entitled “Sparse Array Structures”.
U.S. Pat. No. 5,164,920 entitled “Composite ultrasound transducer and method for manufacturing a structured component therefore of piezoelectric ceramic” discloses a composite ultrasound transducer array containing piezoelectric ceramic transducer elements which radiate substantially in the longitudinal direction, and are embedded in a polymer matrix. The transducer elements have a geometrical structure, and are arranged relative to each other, so that development of oscillation modes perpendicular to the longitudinal direction of the transducer elements is suppressed. The transducer elements may have an arbitrary shape and arrangement, such as hexagonal or irregular square structures, having a trapezoidal cross-section in planes parallel to the longitudinal axis of the transducer elements.
However, there is no disclosure or suggestion in U.S. Pat. No. 5,164,920 regarding a transducer whose elements are arranged in a hexagonal grid, only hexagonal piezoelectric transducer elements are disclosed. U.S. Pat. No. 5,164,920 also discloses the use of structured electrodes that cover multiple ones of the hexagonal piezoelectric transducer elements, thus. defining transmission elements that are not necessarily hexagonal. In particular it is stated that the “structured electrode
24
may be annular or linear” and that “Using the structured electrode
24
, predetermined transducer elements
22
are combined into separately drivable groups”. None of the above-cited prior art references disclose a two-dimensional transducer having hexagonal elements with each hexagonal element having its own electrode.
Therefore, it would be desirable to distribute transducer elements of a two-dimensional transducer array so that the element count is minimized and thus minimize the cost of the circuitry. It would also be desirable to distribute the transducer elements so that the two-dimensional symmetry of the point spread function is maximized. This is important because in medical diagnostic ultrasonic imaging, the transducer array is coupled to an ultrasound imaging system that must produce symmetric speckle shapes. It would also be desirable to have a two-dimensional transducer array having hexagonally shaped elements that each has its own electrode. It would also be desirable to have improved ultrasound imaging systems that may used for medical diagnostic ultrasonic imaging that employ two-dimensional ultrasonic transducer arrays having transducer elements arranged in a non-rectangular or hexagonal grid.
BRIEF SUMMARY OF THE INVENTION
The present invention provides for two-dimensional transducer arrays used for one-, two- and three-dimensional medical diagnostic ultrasonic imaging. The present two-dimensional transducer arrays have transducer elements that are arranged in a non-rectangular, and preferably hexagonal grid. In a preferred embodiment, the transducer array has hexagonally shaped transducer elements. The transducer arrays may be fabricated as single or multiple layer structures. Selected transducer elements of the transducer array are coupled to an ultrasound imaging system that is used in medical diagnostic ultrasonic imaging applications.
Sparse transducer arrays may be fabricated in a hexagonal grid by connecting selected transducer elements to the imaging system. Also, the transducer array may comprise random, vernier and spiral arrays fabricated in a hexagonal grid.
The number of elements required to fully populate the hexagonal grid is 15% less then the number of elements required to fully populate a conventional rectangular grid. For example, a 110-element array in a hexagonal grid has the same grating lobe characteristics as a 128-element array in the conventional rectangular grid. As a result, the cost is reduced due to the fact that fewer processing channels are required.
Alternatively, the image quality is better in a hexagonal grid than in a conventional rectangular grid with the same number of processing channels. For example an aperture fully populated by using 128 elements in a hexagonal grid will have better grating lobe characteristics than an aperture fully populated by using 128 elements in a conventional rectangular grid.
Furthermore, a conventional rectangular grid has two axes of symmetry, compared to three in a hexagonal grid. As a result, grating lobes are distributed more symmetrically in the hexagonal grid than in the conventional rectangular grid, resulting in better grating lobe performance.
REFERENCES:
patent: 5164920 (1992-11-01), Bast et al.
patent: 5295487 (1994-03-01), Saitoh et al.
patent: 5537367 (1996-07-01), Lockwood et al.
patent: 5546946 (1996-08-01), Souquet
patent: 5579768 (1996-12-01), Klesenski
patent: 5793701 (1998-08-01), Wright et al.
patent: 5808962 (1998-09-01), Steinberg et al.
patent: 5893832 (1999-04-01), Song
patent: 5995453 (1999-11-01), Hirata
patent: 6014897 (2000-01-01), Mo
patent: 6102857 (2000-08-01), Kruger
patent: 6102860 (2000-08-01), Mooney
Shelby S. Brunke et al.,Broad-Bandwidth Radiation Patterns of Sparse Two-Dimensional Vernier Arrays;Sep. 1997; pp. 1101-1109.
Richard E. Davidsen et al;Two-Dimensional Random Arrays for Real Time Volumetric Imaging;1994; pp. 143-163.
Andrew Cittadine, Sensant Corp.;Mems Reshapes Ultrasonic Sensing;Feb. 2000; pp. 17-26.
Dreschel William
Sumanaweera Thilaka S.
Acuson Corporation
Jaworski Francis J.
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