Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
1998-11-09
2001-08-21
Winakur, Eric F. (Department: 3736)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S454000, C600S481000, C600S504000
Reexamination Certificate
active
06278890
ABSTRACT:
TABLE OF CONTENTS
FIELD OF THE INVENTION
BACKGROUND OF THE INVENTION
SUMMARY OF THE INVENTION
DEFINITIONS
DESCRIPTION OF THE FIGURES
DETAILED DESCRIPTION OF THE INVENTION
1. The Clinical Workstation
2. The Sensors and Sensor Arrays
3. The Acoustic Imaging System
4. Procedure for Use of The Clinical Workstation
5. Data Acquisition and Processing Beamformers
(a) Near Field Conventional Beamformer
1. Vector Formulation
2. Matrix Formulation
3. Summary Regarding Vector and Matrix Formulation
(b) Adjustable Gain/Resolution Null Space Beamformer
6. Compression Energy Suppression Beamformers
(a) Velocity Filtering
(i) Linear Arrays—Uniform Sensor Spacing
(ii) Non-Linear Arrays
(b) Steering a Null at the Compression Wave
(i) Option 1—See
FIG. 24
(ii) Option 2—See
FIG. 25
(c) Beamforming Methods When Wave Speed (c) as a Function of Frequency is Unknown
(i) Optimal Gridding
(ii) Non-Linear Unconstrained Optimization
(iii) Display of Source Location
7. Non-invasive Detection of Change in Coronary Artery Stenosis
8. Signal to Noise Ratio Enhancement
EXEMPLIFICATION OF THE INVENTION
Claims
ABSTRACT
FIELD OF THE INVENTION
The present invention relates generally to non-invasive blood flow imaging systems and more particularly to systems which are suitable for detecting turbulent blood flow.
BACKGROUND OF THE INVENTION
It is known that vibration of the surrounding structures caused by turbulent blood flow in a partially occluded vessel may produce sounds which are significantly attenuated at body surfaces.
Turbulent blood flow is evidenced by non-uniform spatial distribution of blood flow sound phase coherence. Absent turbulence, blood flow sound phase coherence is generally uniform.
Various techniques for acoustic detection of turbulent blood flow are known. See, e.g., Lees, et al., (1970)
Proceedings of the National Academy of Sciences
67(2):935-942; Semmlow, et al., (1982) “Non-Invasive Diagnosis of Coronary Artery Disease by Enhanced Coronary Phonocardiography”, Abstract, IEEE Frontiers of Engineering in Health Care, pp. 181-185; Semmlow, et al., (1983)
IEEE Transactions on Biomedical Engineering, BME-
30(2):136-139; Wang, et al., (1990)
IEEE Transactions on Biomedical Engineering
, 37(11):1087-1094; Semmlow, et al., (1990)
IEEE Engineering in Medicine and Biology Magazine
, pp. 33-36; Akay, et al., (1992(1))
IEEE Transactions on Biomedical Engineering
, 39(2):176-183; Akay, et al., (1992(2))
Medical
&
Biological Engineering
&
Computing
, 30:147-154; Akay, et al., (1993(1))
IEEE Transactions on Biomedical Engineering
, 40(6):571-578; Akay, et al., (1993(2))
Annals of Biomedical Engineering
, 21:9-17; Verburg, J. (1983)
Adv. Cardiovasc. Phys
. 5(
Part III
):84-103.
SUMMARY OF THE INVENTION
This invention provides reliable, non-invasive methodology and instrumentation for the in vivo detection and localization of abnormal blood flow in a patient.
Generic embodiments of the invention entail detection and imaging of non-uniform spatial distribution of phase coherence of blood flow sounds in a volume of a patient's body below a sensor array.
The wave signals detected by the sensor array comprise a shear wave component and other components including a compression wave component. In the preferred practice of the invention, the shear wave component is isolated from the compression wave component. The isolated shear wave component is processed to provide a display of the spatial distribution of phase coherence of the blood flow sounds in the volume of the patient's body below the sensor array. An essentially uniform display indicates the absence of an abnormal blood flow. A non-uniform display may indicate the presence of an occlusion and the extent of the turbulent flow in the patient's vessel.
The invention may include sensor signal conditioning circuitry and software to implement one or more algorithms. The signal processing circuitry may be combined with a volumetric imager in a mobile clinical workstation operable by a medical technician or a doctor. The invention may include means for enhancement of the signal to noise ratio of the sensor signals.
An important aspect of the invention is a novel non-invasive method for detecting and tracking coronary artery stenosis change following percutaneous intervention.
DEFINITIONS
In this specification, the following words or expressions have the meanings set forth.
Field
An area or volume of space where certain physical laws govern. Typically, those laws are concerned with action at a distance. Examples: a gravitational field, an electromagnetic field or an acoustical field. In this specification, unless otherwise indicated, field refers to a volume of space where the laws governing wave propagation in a visco-elastic media are true.
Near Field
In an isotropic media when a wave front propagates out from a point source, the wave front is spherical in shape. In this specification, “Near Field” means a field near the source, where the wave front has high curvature. When an array of equally spaced sensors detects this curved wave front the delays, or phase shifts between the sensors will be different. If the wave velocity in the media is known, the location of the source in relation to the array can be determined. The location would have 3 dimensions either in Cartesian, Polar, or Spherical coordinates. If a volume a plane is considered then the location will have two dimensions.
Far Field
In this specification “Far Field” means a field far from the source, where the wave front has low curvature. A wave front very far from the source appears planar with no curvature. When an array of equally spaced sensors detects this plane wave front the delays, or phase shifts between the sensors may be different. By a coordinate transformation, directions can be found where the delay is constant per distance across the array and in the orthogonal direction the delay is zero per distance across the array. Determination of the direction of the source in relation to the array is possible of the wave velocity in the medium is known. The direction would have two angular dimensions in spherical coordinates. If a plane as exists with a linear array is considered, then the direction will have one dimension, an angle and the delay or phase shifts between sensors will be constant.
Advance and Sum Beamformer or Bartlett Beamformer or Conventional Beamformer
An algorithm which combines data acquired from a multichannel array of sensors by time shifting the time histories and then summing the signal. If the time histories are shifted negatively with respect to time (advanced) then the algorithm is typically called an advance and sum beamformer. If the time histories are shifted positively with respect to time (delayed) then the algorithm is typically called a delay and sum beamformer.
Path Model
A mathematical representation of the net transformation undergone by a signal as it propagates through a medium or through a circuit. A signal typically originates at a source and ends at a receiver.
Steering Vector
A vector derived from a path model used to steer the response lobe (beam) for an array of sensors.
Vessel
Any part of the human circulatory system through which blood flows. Includes arteries, veins, and the heart.
Abnormal Blood Flow
Any non-laminar, e.g., turbulent blood flow in a vessel.
Stenosis
Any artifact which reduces the effective cross-section of a vessel with consequent blood flow abnormality.
Abnormal Blood Flow Signal
A propagating wave generated by abnormal blood flow usually comprising a compression wave component and a shear wave component.
Sensor or Accelerometer
Any current or voltage mode device which generates an electric signal from displacement or a derivative thereof upon detection of a sound wave.
Sensor Array
The pattern or spaced arrangement of a plurality of sensors on or to be placed on the body surface of a patient. The array of sensors may be fixed in a device or pod positionable on the body surface of a patient.
Phonocardiography
The graphic representation of the sounds that originate in the heart and great vessels.
Chassaing Charles E.
Ryden Carl Ashley
Stearns Scott Donaldson
Van Horn Mark Harold
Carter Ryan
MedAcoustics, Inc.
Myers Bigel Sibley & Sajovec P.A.
Winakur Eric F.
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