Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2001-06-28
2004-02-03
Imam, Ali M. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
Reexamination Certificate
active
06685647
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to acoustic imaging. More specifically, the invention relates to systems and methods utilizing transducers that are adapted to operate with low drive voltages.
2. Description of the Related Art
A prior art two-dimensional (“2-D”) ultrasound transducer typically includes a linear array of transducer elements that are capable of acquiring two-dimensional image data. For example, a 2-D transducer can include a linear array of one hundred and twenty eight (128) elements. In contrast, a three-dimensional (“3D”) transducer is capable of acquiring three-dimensional image data. This is accomplished by providing the elements of such a 3-D transducer in a two-dimensional array. Such an array may include over 1,000 elements, for example.
A representative example of a portion of a conventional transducer is depicted schematically in FIG.
1
. Transducer
100
of
FIG. 1
includes an array of transducer elements
110
that are mounted to a backing
112
. Each element
110
incorporates a piezoelectric element
114
, such as a lead zirconate titanate piezoelectric element (“PZT”), that is adapted to generate an acoustic wave in response to an applied electric field. Such an electric field is applied to the PZT by selectively applying a voltage to electrode layers (not shown) that are formed on opposing sides of the PZT. Each element
110
also includes one or more acoustic matching layers, e.g., layers
116
and
118
. Each of the acoustic matching layers exhibits an acoustic impedance that is less than the acoustic impedance of the PZT, but greater than the acoustic impedance of the body into which acoustic waves are to be propagated. This arrangement couples acoustic energy more efficiently between the element and the body.
Prior art transducers, such as transducer
100
of
FIG. 1
, typically operate at one-half wave resonance. That is, the PZT of each element exhibits a thickness that corresponds to one-half of a wavelength to be generated by the PZT. This thickness typically necessitates the use of high drive voltages, e.g., 170V, for achieving the desired acoustic pressures. More specifically, the PZT changes shape in response to the applied electric field, therefore, the thicker the PZT, the higher the applied voltage required to achieve the same electric field across the PZT.
Referring now to
FIG. 2
, operation of transducer element
110
will be described in greater detail. As shown in
FIG. 2
, PZT
114
produces three forward-directed waves. More specifically, PZT
114
generates a first pair of waves, i.e., a forward-directed wave
210
A and a corresponding backward-directed wave
210
B, at the front surface
212
of the PZT. A second pair of waves, i.e., a forward-directed wave
214
A and a corresponding backward-directed wave
214
B, is generated at the back surface
216
of the PZT. Waves
210
A,
210
B and
214
A,
214
B are generated when an electric field is applied to the PZT via electrodes
218
and
220
. Thereafter, wave
210
B yields a reflected (forward-directed) wave
222
and an absorbed wave
224
. Wave
224
is absorbed by backing
112
, which exhibits an acoustic impedance less than that of the PZT. Forward-directed waves
210
A,
214
A and
222
then interfere with each other to produce a resultant wave
226
.
One of the difficulties in providing an acoustic imaging system that utilizes a 3-D transducer is associated with integrating electronic components of the transducer within the housing of the transducer. In particular, the housing of a 2-D transducer may only include 128 elements, whereas the housing of a 3-D transducer may include over 1000 elements. Thus, the increased number of elements can hinder component integration.
Operational characteristics of conventional transducer elements also can render these elements less than desirable for use in a 3-D transducer. For instance, conventional transducer elements typically operate with high drive voltages (described hereinbefore), which tend to be incompatible for use with integrated circuitry. Therefore, when using conventional transducer elements in a 3-D transducer, a desired level of component integration may not be achievable through the use of integrated circuitry. Thus, it can be appreciated that there is a need for improved systems and methods that address the aforementioned and/or other shortcomings of the prior art.
SUMMARY OF THE INVENTION
Briefly described, the present invention relates to acoustic imaging. In this regard, embodiments of the invention may be construed as acoustic imaging systems. A representative acoustic imaging system includes a transducer that incorporates a backing and an acoustic element extending from the backing. The acoustic element includes a piezoelectric element and a de-matching layer. The de-matching layer is arranged between the backing and the piezoelectric element and exhibits an acoustic impedance greater than that of the piezoelectric element. Additionally, the piezoelectric element exhibits a thickness that is less than one-half of a wavelength to be generated by the piezoelectric element.
Other embodiments of the invention can be construed as methods for acoustically imaging a body. In this regard, a representative method includes: providing a transducer having a backing and an acoustic element extending from the backing; generating acoustic waves with the acoustic element; and substantially preventing acoustic energy generated by the acoustic element from propagating into the backing of the transducer.
Other systems, methods, features, and advantages of the present invention will be or become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the present invention, and be protected by the accompanying claims.
REFERENCES:
patent: 4296349 (1981-10-01), Nakanishi et al.
patent: 4915115 (1990-04-01), Sasaki et al.
patent: 5311095 (1994-05-01), Smith et al.
patent: 5608692 (1997-03-01), Toda
patent: 6045506 (2000-04-01), Hossack
patent: 6049159 (2000-04-01), Barthe et al.
patent: 6497665 (2002-12-01), Hunt et al.
patent: 6508775 (2003-01-01), McKenzie et al.
Ossmann William J.
Savord Bernard J.
Imam Ali M.
Koninklijke Philips Electronics , N.V.
Vodopia John
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