Surgery – Diagnostic testing – Cardiovascular
Reexamination Certificate
1998-08-20
2001-07-17
Evanisko, George R. (Department: 3762)
Surgery
Diagnostic testing
Cardiovascular
C600S528000
Reexamination Certificate
active
06261237
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a flexible, thin-film sensor for the passive acoustic detection of heart and blood-flow sounds.
BACKGROUND OF THE INVENTION
Certain polymers, copolymers and blends demonstrate piezoelectric behavior due to dipolar ferroelectricity residing in specific crystal phases. The most common of the semicrystalline ferroelectric polymers are poly(vinylidene fluoride) (PVDF) and its copolymer with trifluoroethylene, P(VDF-TrFE). As with any piezoelectrically active material, if electrodes are deposited on both of the major surfaces of a sample of piezoelectric film, the element functions as an electromechanical transducer and thus can be used as a sensor or actuator. If the film, operating as a sensor, is subjected to stress either in the direction corresponding to the film thickness, or in either of the transverse directions, an electric potential proportional to the applied stress is developed across the thickness of the film. The electrodes enable connection to external electronic circuitry, making it possible to process the information provided by the sensor.
Sensors having piezoelectric film transducers for passive detection of body sounds are known. See, e.g., U.S. Pat. Nos. 5,365,937 and 5,595,188 and published applications WO/92-08407 and WO/90-08506. However, known sensors may be characterized by undesirable performance constraints, including low signal to noise ratio, cross-talk, and signal contamination from power line harmonics or ambient room noise. These constraints may in part be attributable to transducer non-conformity to human body surfaces.
An improved thin-film sensor for the efficient passive detection of heart and blood-flow sounds is needed.
SUMMARY OF THE INVENTION
Integral components of the flexible thin-film sensor of this invention may comprise a piezoelectric film which may have a rectangular active area, a housing including film support means onto which the film is mounted, and a foot. The foot is the only sensor component intended to contact the skin. Hereafter these components are referred to as the “film”, “housing”, and “foot”.
The invention may include sensors in which an initially slack piezoelectric film having fixed opposite edges is tented by the sensor mass to produce a stress upon vertical displacement of the acoustic medium, e.g., human flesh, upon which the sensor may be positioned.
The invention may also include sensors wherein the piezoelectric film is tensioned initially.
An important feature of the invention comprises sensors wherein the sensor spring constant is of the same order of magnitude and preferably matched to the spring constant of human flesh. It is preferred that the sensor be configured such that the film segment operates with a spring constant of from about 2 kN/m to about 4 kN/m.
The invention may comprise a single sensor or a plurality of individual sensors. A plurality of individual sensors may be assembled in a linear array or snake. A linear array may also comprise a plurality of links, each comprised of two or more individual sensors. Linear arrays of sensors may be positioned within a patient intercostal space (ICS). Undesired movement of a positioned array may be avoided by a laterally adjacent strip or laterally adjacent strips of adhesive tape.
A plurality of linear sensor arrays or of individual sensors may be positioned to accommodate a patient acoustic window.
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Chassaing Charles E.
Lewandowski Simon J.
Sleva Michael Z.
Swanson Cal T.
Evanisko George R.
MedAcoustics, Inc.
Myers Bigel Sibley & Sajovec P.A.
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