Expanding-Aperture Annular Array 1

Abstract

A dynamically-focused annular array system for contact B-scanning has been developed. The design is based on a constant F-number approach, whereby, at short focal lengths, the aperture is increased in proportion to the focal length. This approach allows the use of larger area array elements, thus increasing the sensitivity of the system. Other major advantages include a substantial reduction in the time delays and refocusing rates required for the lens synthesis with a corresponding reduction in the electronic complexity of the system. The initial design employs an array operating at 2.25 MHz, with four annuli active at the near focal length of 1.5 cm. As the focal length increases, the array expands to a maximum of twelve rings, with 4.0 cm outer diameter, for focal lengths greater than 12 cm. A single, tapped delay line with 1 μs total duration provides the time delays for focusing on receive. A variable point or line focus is provided on transmit. Experimental measurements of the focusing properties of the system include beam profiles showing mainlobe width and sidelobe levels and B-scans of a standard test object.

Keywords

Annular array dynamic focusing ultrasonics

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References

Von Ramm

O. T.

Thurstone

F. L.

, Cardiovascular Diagnosis with Real Time Ultrasound Imaging, in Acoustical Holography, Vol. 6, Newell

Booth

, ed., pp. 91–102 (Plenum Press, New York, 1975).

Thurstone

F. L.

Von Ramm

O. T.

, New Ultrasound Imaging Technique Employing Two-Dimensional Electronic Beam Steering, in Acoustical Holography, Vol. 5, Philip

Green

, ed., pp. 249–259 (Plenum Press, New York, 1974).

Kossoff

Carpenter

D. A.

Radovanovich

Robinson

D. E.

Garrett

W. J.

, Octoson: A New Rapid Multitransducer General Purpose Water-Coupling Echoscope, in Ultrasonics in Medicine, Kazer

De Vlieger

Muller

H. R.

McCready

V. R.

, eds., pp. 90–102 (American Elsevier, New York, 1975).

Garret

W. J.

Kossoff

Fisher

, Ultrasonic Diagnosis of Congenital Abnormalities in the Fetal Chest and Abdomen, in Ultrasonics in Medicine, Kazner

De Vlieger

Muller

H. R.

McCready

V. R.

, eds., pp. 311–315 (American Elsevier, New York, 1975).

This approach has been taken in several commercial units.

Vilkomerson

, Acoustic Imaging with Thin Annular Apertures, in Acoustical Holography, Vol. 5, Philip

Green

, ed., pp. 283–316 (Plenum Press, New York, 1974).

Burckhardt

C. B.

Grandchamp

P. A.

Hoffman

, Focusing ultrasound over a large depth with an annular array transducer–an alternative method, IEEE Trans. Sonics and Ultrasonics, SU-22, 11–15 (1975).

Macovski

Norton

S. J.

, High Resolution B-Scan Systems Using a Circular Array, in Acoustical Holography, Vol. 6, Newell

Booth

, ed., pp. 121–143 (Plenum Press, New York, 1975).

Melton

H. E.

Thurstone

F. L.

, Annular array design and logarithmic processing for ultrasonic imaging, Ultrasound Med. Biol., 4, 1–12 (1979); Melton, H., Electronic Focal Scanning for Improved Resolution in Ultrasound Imaging, Ph. D. Thesis, Duke University, 1972, (University Microfilms Cat. No. 72-23, 243).

10.

Bernardi

R. B.

Peluso

P. J.

O'Connell

R. J.

Kellog

Shih

, A Dynamically Focused Annular Array, 1976 IEEE Ultrasonics Symposium Proceedings, pp. 157–159 (IEEE Cat. No. 76 CH1120-5SU).

11.

Goodman

J. W.

, Introduction to Fourier Optics, (McGraw-Hill, New York, 1968).

12.

Norton

S. N.

, Theory of Acoustic Imaging, Ph. D. Thesis, Stanford University, 1976.

13.

Foster

F. S.

Hunt

J. W.

, The Focusing of Ultrasound Beams Through Human Tissue, in Acoustical Holography, Vol. 8 (Plenum Press, New York) (In Press).

14.

Steinberg

B. D.

, Principles of Aperture and Array System Design (John Wiley and Sons, New York, 1976).

15.

Welsby

V. G.

, Multiplicative receiving array–the angular resolution of targets in a sonar system with electronic scanning, J. Brit. I. R. E., 22, 5–12 (1961).

16.

Walker

J. T.

Meindl

J. D.

, A Digitally Controlled C. C. D. Dynamically Focused Phase Array, 1975 IEEE Ultrasonics Symposium Proceedings, pp. 80–83 (IEEE Cat. No. 75, CHO 994-4SU).

17.

Dapco Industries, Inc., Georgetown, CT, 06829. (Certain commercial equipment, instruments, or materials are identified in this paper in order to adequately specify the experimental procedure. In no case does such identification imply recommendation or endorsement by the National Bureau of Standards, nor does it imply that the material or equipment identified is necessarily the best available for the purpose.).

18.

Burckhardt

C. B.

Hoffman

Grandchamp

P. A.

, Ultrasound axicon: a device for focusing over a large depth, J. Acoust. Soc. Amer., 54, 1628–1630 (1973).

19.

Erickson

K. R.

Carson

P. L.

(Primary Authors), The AIUM standard 100 mm test object and recommended procedures for its use, Reflections, 1, 74–91 (1975).

20.

Auld

B. A.

Drake

M. E.

Roberts

C. G.

, Monolithic acoustic imaging transducers with high spatial resolution, Appl. Phys. Letters, 25, 478–479 (1974).

21.

DeSilets

C. S.

Fraser

J. D.

Kino

G. S.

, The design of efficient broadband piezoelectric transducers, IEEE Trans. Sonics and Ultrasonics, SU-25, 115–125 (1978).

22.

Green

P. S.

Havilice

J. F.

Holzemer

S. D.

Ramsey

J. R.

Taenzer

J. C.

Moessner

H. Z.

, Design and construction of a dynamically focused annular array, IEEE Trans. Sonics and Ultrasonics, SU-25, 259 (1978) (Abstract Only).

23.

Ueda

Sato

Maeda

, Dynamic focusing ultrasonic transducer by using analog gate delay circuits, Bull. Tokyo Inst. Tech., 119, 55–63, (1973).