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Publication Number
US-8852110-B2
Publication Date
2014-10-07
Expiration Date
Abstract
The velocity of fluids containing particles that scatter ultrasound can be measured by determining the Doppler shift of the ultrasound scattered by the particles in the fluid. Measuring fluid flow in cylindrical vessels such as blood vessels is an important use of Doppler ultrasound. This invention teaches using various configurations of cylindrical diffraction-grating transducers and cylindrical non-diffraction-grating transducers that suppress the Doppler shift from non-axial components of fluid velocity while being sensitive to the Doppler shift produced by axial velocity components. These configurations thus provide accurate measurement of the net flow down the vessel, even when the fluid flow is curved or not parallel to the vessel wall.
Core Innovation
The invention relates to measuring a velocity of a fluid containing ultrasound scatterers flowing through a lumen using a Doppler technique. A cylindrical diffraction-grating transducer and a cylindrical non-diffraction-grating transducer are coupled adjacent to each other and adapted to be wrapped around the circumference of the lumen. The cylindrical diffraction-grating transducer excites an ultrasound beam at a predetermined angle with respect to the axis, and scattered signals are received at the cylindrical non-diffraction-grating transducer.
The cylindrical diffraction-grating transducer and the cylindrical non-diffraction-grating transducer are configured such that wavefronts from opposite walls of the cylindrical non-diffraction-grating transducer form multiple equiphase planes perpendicular to the axis of the cylindrical diffraction-grating transducer. The determining of the velocity is based on the changing phases of the received scattered signal corresponding to the scatterers in the fluid crossing at least one of the equiphase planes, with a Doppler shift associated with scatterers crossing the equiphase planes.
Embodiments include a single diffraction-grating transducer with a single non-diffraction-grating transducer, a double-beam arrangement, and an arrangement using two diffraction-grating transducers with a central non-diffraction-grating transducer. The apparatus includes circuits that determine first and second changing phases of the scattered signals with respect to the double ultrasound beam, where in the two-diffraction-grating embodiment the first and second frequencies are different frequencies.
The document further addresses measuring Doppler flow for curved blood vessel flow vectors that are not parallel to the vessel wall, arguing accurate net flow measurement by suppressing Doppler from non-axial velocity components. Transducer construction embodiments describe electroded flexible plastic film, a piezoplastic transducer layer, and a conductor layer.
Claims Coverage
The independent claims cover a Doppler-based velocity measurement method and corresponding ultrasonic transducer apparatuses. Across the independent claims, the inventive features focus on coupled cylindrical diffraction-grating and non-diffraction-grating transducers wrapped around a lumen, forming multiple equiphase planes perpendicular to the transducer axis, and determining velocity based on changing phase of received scattered signals corresponding to scatterers crossing equiphase planes, including single-beam, double-beam, and multi-transducer configurations with different frequencies in one apparatus claim.
Coupled cylindrical diffraction-grating and non-diffraction-grating transducers for Doppler phase velocity determination
Coupling a cylindrical diffraction-grating transducer and a cylindrical non-diffraction-grating transducer adjacent to each other; exciting from the cylindrical diffraction-grating transducer an ultrasound beam at a predetermined angle with respect to the axis; receiving a scattered signal at the cylindrical non-diffraction-grating transducer; and determining the velocity based on the changing phases of the received scattered signal corresponding to scatterers crossing at least one of multiple equiphase planes perpendicular to the axis, wherein the transducers are adapted to be wrapped around the circumference of the lumen.
Double ultrasound beam with equiphase planes and adjacent first and second non-diffraction-grating transducers
Providing a cylindrical diffraction-grating transducer adapted to be wrapped around the circumference of the lumen to form multiple equiphase planes perpendicular to the axis, exciting a double ultrasound beam at a predetermined angle; providing a first and a second cylindrical non-diffraction-grating transducer each placed adjacent to and on opposite sides of the cylindrical diffraction-grating transducer and wrapped around the circumference of the lumen; determining first and second changing phases of scattered signals received at the first and second non-diffraction-grating transducers with respect to the double ultrasound beam; and determining the velocity based on the first and second changing phases corresponding to scatterers crossing at least one equiphase plane.
Two wrapped cylindrical diffraction-grating transducers at different frequencies with a central non-diffraction-grating transducer
Exciting a first double ultrasound beam using a first cylindrical diffraction-grating transducer and forming a first set of multiple equiphase planes perpendicular to the axis; exciting a second double ultrasound beam using a second cylindrical diffraction-grating transducer and forming a second set of multiple equiphase planes perpendicular to the axis; providing a cylindrical non-diffraction-grating transducer placed adjacent to and between the first and second cylindrical diffraction-grating transducers and wrapped around the circumference of the lumen; determining first and second changing phases of scattered signals corresponding to scatterers crossing at least one of the first and second sets of equiphase planes; and determining the velocity based on the first changing phase and the second changing phase, wherein the first and second frequencies are different frequencies.
Across the independent claims, the core claim coverage centers on wrapping cylindrical diffraction-grating and non-diffraction-grating transducers around a lumen to form multiple equiphase planes perpendicular to the transducer axis, and using phase changes of scattered signals received from non-diffraction-grating transducers to determine fluid velocity, including single-coupled, opposite-side double-beam, and two-diffraction-grating different-frequency configurations.
Stated Advantages
Accurate net flow measurement even for curved blood vessel flow not parallel to the vessel wall, by suppressing Doppler from non-axial velocity components.
Insonating most of the lumen cross-section.
Accounting for attenuation by equalizing beam amplitudes and using voltage compensation.
Documented Applications
Ultrasound Doppler-based measurement of fluid velocity within a lumen/vessel/pipe using ultrasound scatterers (e.g., red blood cells) for blood flow measurement.
Measuring Doppler flow in a curved blood vessel where flow vectors are not parallel to the vessel wall.
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