University of Texas System

Acoustic Standards Corporation

The United States of America, As Represented by the Secretary, Department of Health and Human Services

North American Philips Corporation

University of Houston System

National Institute of Health (nih)

Jonathan Ophir

Youseph Yazdi

Nabil F Maklad

Ignacio Cespedes

Raffaella Righetti

Elisa Konofagou

Hari Ponnekanti

Paul M Jaeger

David P Shattuck

Seshadri Srinivasan

The invention is directed toward a new method for estimating and imaging the spatial and temporal mechanical behavior of materials in responses to a mechanical stimulus. This method is designed to work in inherently noisy applications, such as the imaging of the time-dependent mechanical behavior of biological tissues in vivo and using a preferred hand-held configuration of scanning.

Method for imaging strain of a target body

Method for estimating strain, strain ratios and displacements in a target body

The present invention is directed toward an apparatus and method for determining localized strain in a target body by identifying sets of features in reflected echo sequences and by comparing sets of features to determine time shift values between features.

Method and apparatus for feature tracking strain estimation for elastography

Elastography can produce quality strain images in vitro and in vivo. Standard elastography uses a coherent cross-correlation technique to estimate tissue displacement and tissue strain using a subsequent gradient operator. While coherent estimation methods generally have the advantage of being highly accurate and precise, even relatively small undesired motions are likely to cause enough signal decorrelation to produce significant degradation of the elastogram. For elastography to become more universally practical in such applications as hand-held, intravascular and abdominal imaging, the limitations associated with coherent strain estimation methods that require tissue and system stability, must be overcome. In this paper, we propose the use of a spectral shift method that uses a centroid shift estimate to measure local strain directly. Furthermore, we also show theoretically that a spectral bandwidth method can also provide a direct strain estimation. We demonstrate that strain estimation using the spectral shift technique is moderately less precise but far more robust than the cross-correlation method. A theoretical analysis as well as simulations and experimental results are used to illustrate the properties associated with this method.

Power spectral strain estimators in elastography

The present invention is directed toward a new method that combines interpolation between neighboring A-lines with cross-correlation for high precision estimation of the transverse displacement. Due to this high precision lateral estimation, the method of the present invention can produce quality lateral-elastograms that display the lateral component of the strain tensor. These higher precision lateral displacement estimates also allow a finer correction for the lateral decorrelation that corrupts the axial estimation. The method of the present invention may be employed to divide the lateral-elastogram by the axial-elastogram on a pixel-by-pixel basis, in order to produce a new image that displays the distribution of Poisson's ratios in the tissue.

Method for estimating and imaging of transverse displacements, transverse strains and strain ratios

An improved ultrasonic pulse-echo method and apparatus that has particular application in making precision measurements of compressibility in any backscattering material, in particular organic tissue, is disclosed. The method employs a standard transducer or transducer containing device which is translated transaxially, thereby compressing or displacing a proximal region of a target body in small known increments. At each increment, a pulse is emitted and an echo sequence (A-line) is detected from regions within the target along the sonic travel path or beam of the transducer. Resulting time shifts in echo segments corresponding to features in the target, corrected for regions of varying sonic speed along the sonic path, provide relative and quantitative information concerning the strain caused by the compressions. The stress imparted by the transducer and containing device is also determined, corrected for depth along the sonic path. The appropriate values for stress are divided into the respective values for strain along each path to yield an elastogram, or array of compressibility values, of the target.

Method and apparatus for elastographic measurement and imaging

An improved ultrasonic pulse-echo method and apparatus that has particular application in estimating sound velocity in organic tissue is disclosed. The method employs a standard transducer or transducer containing device which is translated transaxially, thereby compressing or displacing a proximal region of a target body in small known increments. At each increment, a pulse is emitted and an echo sequence (A-line) is acquired from regions within the target along the sonic travel path or beam of the transducer. Segments of the echo sequence corresponding to a distal region within the target are selected as a reference to estimate the incremental change in echo arrival time. A plot of these arrival time estimates versus the target compression depth is then generated and a least squares linear fit is made. The slope of the linear fit is c.sup.-1, where c is an estimate of the speed of sound in the target.

Transaxial compression technique for sound velocity estimation

An improved ultrasonic pulse-echo method and apparatus that has particular application in making precision measurements of compressibility in any backscattering material, in particular organic tissue, is disclosed. The method employs a standard transducer or transducer containing device which is translated transaxially, thereby compressing or displacing a proximal region of a target body in small known increments. At each increment, a pulse is emitted and an echo sequence (A-line) is detected from regions within the target along the sonic travel path or beam of the transducer. Resulting time shifts in echo segments corresponding to features in the target provide relative and quantitative information concerning compressibility of the target.

Method and apparatus for measurement and imaging of tissue

The present invention provides a novel method and apparatus which allows concomitant imaging and rapid axial beam translation measurements used to calculate the attenuation characteristics of a target body. The present invention employs an ultrasonic scanner which contains a plurality of matched transducer elements. These elements are staggered on a mechanism which sequentially places each transducer opposite an acoustic window at axially spaced positions along a common axis. The present invention also enables axial beam translation techniques to be adapted to current ultrasonic imaging systems.

System for ultrasonic pan focal imaging and axial beam translation

This invention relates to a method for correcting angle error present in in vivo sound velocity estimations. More particularly, this invention relates to a method for estimating the angle of misdirection of a tracked ultrasound beam used in sound velocity measurements in conjunction with multi-tracking ultrasound beams.

Multi-beam tracking for angle error correction in speed of sound

A method and apparatus of enhancing the accuracy of in vivo sound velocity estimation by identifying segments of different sound velocity along a tracked ultrasound beam. The effects of refraction on the tracked beam at the interface between tissue regions are estimated. Also disclosed is a technique for estimating the refractive effects of naturally occurring and artificially introduced acoustical contrast fluids. The accuracy of the sound velocity measurements is increased by utilizing the centroid-to-centroid distance between the pulses produced by ultrasound sending and receiving transducers in calculating the ultrasound beam velocity.

Pulse centroid echo method and apparatus for enhanced sound velocity

A method of enhancing the accuracy of in vivo sound velocity estimation by identifying segments of different sound velocity along a tracked ultrasound beam. The effects of refraction on the tracked beam at the interface between tissue regions are estimated. Also disclosed is a technique for estimating the refractive effects of naturally occurring and artificially introduced acoustical contrast fluids.

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Houston, TX, United States of America

Jonathan Ophir