A Least-Squares Strain Estimator for Elastography

A least-squares strain estimator (LSQSE) for elastography is proposed. It is shown that with such an estimator, the signal-to-noise ratio in an elastogram (SNRe ) is significantly improved. This improvement is illustrated theoretically using a modified strain filter and experimentally using a homogeneous gel phantom. It is demonstrated that the LSQSE results in an increase of the elastographic sensitivity (smallest strain that could be detected), thereby increasing the strain dynamic range. Using simulated data, it is shown that a tradeoff exists between the improvement in SNRe and the reduction of strain contrast and spatial resolution.

[1]  C. Burckhardt.  Speckle in ultrasound B-mode scans , 1978, IEEE Transactions on Sonics and Ultrasonics.

[2]  A. Weiss,et al.  Fundamental limitations in passive time delay estimation--Part I: Narrow-band systems , 1983 .

[3]  G. Carter.  Coherence and time delay estimation , 1987, Proceedings of the IEEE.

[4]  J. Ophir,et al.  Elastography: A Quantitative Method for Imaging the Elasticity of Biological Tissues , 1991, Ultrasonic imaging.

[5]  M. O’Donnell,et al.  Internal displacement and strain imaging using ultrasonic speckle tracking , 1994, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[6]  W. Walker,et al.  A fundamental limit on delay estimation using partially correlated speckle signals , 1995, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[7]  J. Ophir,et al.  Theoretical bounds on strain estimation in elastography , 1995, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[8]  J. Ophir,et al.  Methods for estimation of subsample time delays of digitized echo signals. , 1995, Ultrasonic imaging.

[9]  B. Garra,et al.  Elastography: Ultrasonic imaging of tissue strain and elastic modulus in vivo , 1996 .

[10]  Faouzi Kallel,et al.  Tissue elasticity reconstruction using linear perturbation method , 1996, IEEE Trans. Medical Imaging.

[11]  J Ophir,et al.  Fundamental limitations on the contrast-transfer efficiency in elastography: an analytic study. , 1996, Ultrasound in medicine & biology.

[12]  I Céspedes,et al.  Noise reduction in elastograms using temporal stretching with multicompression averaging. , 1996, Ultrasound in medicine & biology.

[13]  J Ophir,et al.  The nonstationary strain filter in elastography: Part II. Lateral and elevational decorrelation. , 1997, Ultrasound in medicine & biology.

[14]  J. Ophir,et al.  Three-dimensional tissue motion and its effect on image noise in elastography , 1997, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[15]  T. Varghese,et al.  A theoretical framework for performance characterization of elastography: the strain filter , 1997, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[16]  J Ophir,et al.  Elastographic Dynamic Range Expansion Using Variable Applied Strains , 1997, Ultrasonic imaging.