Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2001-12-05
2003-09-02
Jaworski, Francis J. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
Reexamination Certificate
active
06612987
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to ultrasound imaging systems that use ultrasonic transducers to provide diagnostic information concerning the interior of the body, and more particularly, to an apparatus and method for selectively optimizing an acoustic transducer.
BACKGROUND OF THE INVENTION
Ultrasonic diagnostic imaging systems are in widespread use for performing ultrasonic imaging and measurements. For example, cardiologists, radiologists, and obstetricians use ultrasonic imaging systems to examine the heart, various abdominal organs, or a developing fetus, respectively. Diagnostic images are obtained from these systems by placing a scanhead against the skin of a patient, and actuating an ultrasonic transducer located within the scanhead to transmit ultrasonic energy through the skin and into the body of the patient. In response, ultrasonic echoes are reflected from the interior structure of the body, and the returning acoustic echoes are converted into electrical signals by the transducer in the scanhead.
FIG. 1
is a functional block diagram of an ultrasound imaging system
10
according to the prior art. The system
10
includes an ultrasound processor
11
that is coupled to a scanhead assembly
12
by a connecting cable
26
. The ultrasonic processor
11
further includes a transmitter
22
that generates signals at ultrasonic frequencies for emission by the scanhead assembly
12
, and a receiver
16
to process signals received by the scanhead assembly
12
. In order to isolate the transmitter
22
from the scanhead assembly
12
while the receiver
16
is in operation, a transmitter isolation unit
18
decouples the transmitter
22
from the cable
26
. Correspondingly, when the transmitter
22
is in operation, a receiver protection unit
19
decouples the receiver
16
from the cable
26
. A controller
14
interacts with the transmitter
22
, the receiver
16
, the transmitter isolation unit
18
and the receiver protection unit
19
to coordinate the operation of these components. The controller
14
similarly interacts with a display system
15
to coordinate the reception of signals received by the processor
11
so that a visual image may be generated.
The scanhead assembly
12
includes a transducer assembly
28
that is comprised of one or more piezoelectric elements
30
that are capable of emitting ultrasonic pulses when excited by signals generated by the transmitter
22
, and converting the reflected portions of the pulses into electrical signals that may be processed by the receiver
16
. The transducer assembly
28
is coupled to the processor
11
through a tuning network
20
that tunes the assembly
28
to optimize the characteristics of the scanhead and the processor
11
. The tuning network
20
may be attached to assembly
28
to form the integral scanhead assembly
12
, or alternatively, the network
20
may be interposed between the assembly
28
and the processor
11
at a position along the connecting cable
26
, as also shown in FIG.
1
. Still further, the tuning network
20
may be positioned within the processor
11
(not shown) or within a connecting element in the connecting cable
26
(also not shown).
FIG. 2
is a partial schematic diagram of the ultrasound imaging system
10
according to the prior art. The transducer assembly
28
is serially coupled to the processor
11
through the connecting cable
26
and a tuning inductor
36
. For clarity of illustration,
FIG. 2
shows only a single element
30
(as shown in
FIG. 1
) coupled to a single connecting cable
26
by a single inductor
36
. It is understood, however, that the transducer assembly
28
generally includes more than a single element
30
, each of which may be coupled to the processor
11
through a separate, dedicated tuning inductor
36
and cable
26
.
In general, the inductor
36
does not have an inductance value that permits the element
30
to be operated at only a single resonant condition. Instead, the inductor
36
is selected to allow the element
30
to be operated over a range of frequencies that define an acceptable operating bandwidth for the element
30
in a prescribed imaging mode. One trade-off of this approach is that a broad bandwidth for the element
30
generally results in a reduced sensitivity of the element
30
to the reflected pulses at a particular individual frequency. While somewhat reduced sensitivity of the element
30
may be acceptable when the imaging system
10
is operated, for instance, in a gray scale mode, it may have disadvantages in certain other ultrasound operating modes. For example, the system
10
may be operated in a Doppler ultrasound mode to provide an image of blood flow in an interior portion of a patient. In this imaging mode, the return signal is scattered from minute corpuscular components in the blood flow, which produces return signals that are generally greatly reduced in magnitude as compared to return signals typically encountered in the gray scale imaging mode. Increasing the magnitude of the emitted signal to produce stronger return signals cannot, in general, mitigate this disadvantage, since the magnitude of ultrasound signals cannot exceed prescribed levels that may produce cavitation effects in the interior portions of the patient's body, or produce damaging levels of tissue heating. Alternatively, dynamically changing the inductance of the inductor
36
is difficult since the inductor
36
is generally a fixed component that is positioned within a scanhead assembly, or in other portions of an ultrasound imaging system.
Accordingly, there exists a need in the art for an ultrasound system that permits optimization of a transducer assembly to achieve wide bandwidth operation for certain ultrasound operating modes and narrower bandwidth operation to be selected for other modes of operation that require higher transducer sensitivity, as well other characteristics for different modes.
SUMMARY OF THE INVENTION
The invention is directed towards an apparatus and method for selectively optimizing an ultrasound transducer assembly to provide enhanced performance in specific ultrasound modes of operation. In one aspect, a variable impedance network is positioned between an ultrasound processor and a transducer assembly and may be coupled to the transducer assembly to form either a series or a parallel connection with the transducer assembly. The variable impedance network may be controlled by the processor to selectively alter the characteristics of the network to optimize the transducer assembly for a selected operating mode. In another aspect, the variable impedance network includes a pair of serially coupled inductors and a switch that permits one of the inductors to be controllably bypassed. In still another aspect, the variable impedance network includes a tapped inductor and a switch that permits the inductor tap to be controllably selected. In still another aspect, the inductor includes a tapped inductor having more than a single tap, each tap being selected by a switch to alter the impedance of the network.
REFERENCES:
patent: 3934577 (1976-01-01), Romani
patent: 5198713 (1993-03-01), Suzuta
patent: 5313947 (1994-05-01), Micco
patent: 5603324 (1997-02-01), Oppelt et al.
patent: 6104670 (2000-08-01), Hossack et al.
Morsy Ahmed
Robinson Andrew
Dorsey & Whitney LLP
Jaworski Francis J.
Koninklijke Philips Electronics , N.V.
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