Transducer apparatus and method for intravascular blood flow measurement
Inventors
Vilkomerson, David • Chilipka, Thomas A. • Bogan, John W.
Assignees
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Publication Number
US-8052608-B2
Publication Date
2011-11-08
Expiration Date
Abstract
Transducers to measure fluid flow using Doppler ultrasound that are suitable for integrating into or connecting to intravascular devices are disclosed. These transducers meet the requirement for long, thin, flexible transducers, and consist of one or more diffraction-grating transducers, with or without non-diffraction-grating transducers. An exemplary configuration of the transducers utilizes the diffraction caused by narrow transducers to produce beam overlap for Doppler detection of moving blood, and stripline transmission lines are used to bring energy to and receive energy from the transducers and may carry the disclosed transducer configurations as well as carry signals into and out of the blood vessels.
Core Innovation
The invention provides an apparatus for measuring blood flow that includes an elongated, narrow ribbon-like diffraction grating transducer (DGT). The DGT includes alternatively polarized sections of piezoelectric media, where each section is separated by separation media, and a signal is applied to cause the DGT to produce a propagating diffracted beam in one direction relatively parallel to the length of the DGT.
In the disclosed configuration for measuring flow in a vessel, the DGT is positioned at the periphery of the vessel and is substantially longer than the width of the vessel periphery region. The apparatus further includes a second transducer positioned at the periphery and spaced apart from the DGT, the second transducer having a ribbon-like appearance with non-polarized sections and being operative to receive Doppler-shifted ultrasound frequencies produced by blood flowing through the propagating beam.
The description emphasizes controlling Doppler measurement behavior and signal coupling by producing a propagating diffracted beam with a sensitive volume associated with beam spreading and overlap. The disclosed examples further address impedance matching through transducer dimensions and stripline transmission integration, and include configurations that avoid use of a transmit/receive switch for continuous-wave (CW) Doppler.
Claims Coverage
The independent claims cover two apparatus types for measuring blood flow and/or flow in a vessel, with four main inventive features across the independent claims.
Ribbon-like DGT with alternately polarized piezoelectric sections
A first elongated narrow ribbon-like diffraction grating transducer (DGT) having a given length, the DGT comprising alternatively polarized sections of piezoelectric media, each section being separated by separation media.
Propagating diffracted beam with perpendicular spreading
Means for applying a signal to the DGT to cause the DGT to produce a propagating diffracted beam therefrom in one direction relatively parallel to the length of the DGT and due to the narrow extent the beam spreads in a direction perpendicular to the length.
Periphery-positioned DGT producing a propagating beam
A diffraction grating transducer (DGT) positioned at the periphery of a vessel and being substantially longer than the width thereof, the DGT having a ribbon-like appearance and alternately polarized sections to enable the DGT to produce by diffraction a propagating beam in a given direction along a path.
Spaced non-polarized second transducer receiving Doppler-shifted frequencies
A second transducer positioned at the periphery of the vessel and spaced apart from the DGT, the second transducer being of a length and width relatively the same as the DGT and having a ribbon-like appearance and having non-polarized sections, and operative to receive Doppler-shifted ultrasound frequencies produced by the flow of blood through the propagating beam from the DGT.
Across the independent claims, the key coverage centers on a ribbon-like diffraction grating transducer with alternately polarized piezoelectric sections separated by separation media, driven to generate a propagating diffracted beam that spreads perpendicular to the DGT length, together with peripherally located transmission and reception structures that enable the apparatus to receive Doppler-shifted ultrasound frequencies produced by blood flowing through the propagating beam path.
Stated Advantages
Reduces cross-talk and eliminates zero-frequency Doppler.
Impedance matching is addressed through transducer dimensions and stripline transmission line integration.
Supports continuous-wave (CW) Doppler operation without a transmit/receive switch.
Allows directional Doppler by regaining flow direction through angular offset of beam overlap.
Documented Applications
Intravascular blood flow measurement using a diffraction-grating transducer architecture suitable for peripherally positioned deployment.
Flow measurement in a vessel using a periphery-mounted DGT and a spaced, periphery-mounted second transducer.
Deployment in a stent or vena-cava-filter-like arrangement.
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