Axial Strain Imaging Using a Local Estimation of the Scaling Factor from RF Ultrasound Signals

Abstract

The main signal-processing techniques used in elastography compute strains as the displacement derivative. They perform well for very low deformations, but suffer rapidly from decorrelation noise. Aiming to increase the range of accurate strain measurements, we developed an adaptive method based on the estimation of strains as local scaling factors. Its adaptability makes this method appropriate for computing scaling factors resulting from larger strains or a wide spread of strain variations. First, segments corresponding to the same part of tissue are adaptively selected in the rest and stressed state echo signals. Then, local scaling factors are estimated by iteratively varying their values until reaching the zero of the phase of the complex cross-correlation function.

Results from simulation and from experimental data are presented. They show how this adaptive method can track various local deformations and its accuracy for strain up to 7%.

Keywords

Adaptive estimation complex cross-correlation elastography phase scaling factor strain ultrasound

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References

Ophir

Céspedes

Ponnekanti

Yazdi

, Elastography: a quantitative method for imaging the elasticity of biological tissues, Ultrasonic Imaging 13, 111–134 (1991).

Hearn

E.J.

, Mechanics of Materials: An Introduction to the Mechanics of Elastic and Plastic Deformation of Solids and Structural Materials. Third Edition (Heinemann, London. 1997).

Céspedes

, Elastography: Imaging Biological Tissue Elasticity, Ph.D Dissertation, (Department of Electrical Engineering, Faculty of Houston, 1993).

De Korte

C.L.

Van der Steen

A.F.W.

Dijkman

B.H.J.

Lancee

C.T.

, Performance of time delay estimation methods for small time shifts in ultrasonic signals. Ultrasonics 35, 263–274 (1997).

Cespedes

Ophir

, Reduction of image noise in elastography. Ultrasonic Imaging 15, 89–102 (1993).

Hein

O'Brien

W.J.

, Current time-domain methods for assessing tissue motion by analysis from reflected ultrasound echoes - a review. IEEE Trans. Ultrason. Ferroelec. Freq. Contr. 40, 84–102 (1993).

Konofagou

E.E.

Alam

S.K.

Ophir

Krouskop

, Methods for dynamic range expansion and enhancement of the signal-to-noise ratio in elastography, in IEEE Ultrasonics Symposium, 1157–1160 (Toronto, 1997).

Lubinski

M.A.

Emelianov

S.Y.

O'Donnell

, Speckle tracking methods for ultrasonic elasticity imaging using short-time correlation. IEEE Trans. Ultrason. Ferroelec. Freq. Contr. 46, 82–96 (1999).

O'Donnell

Skovoroda

A.R.

Shapo

B.M.

Emelianov

S.Y.

, Internal displacement and strain imaging using ultrasonic speckle tracking. IEEE Trans. Ultrason. Ferroelec. Freq. Contr. 41, 314–324 (1994).

10.

Konofagou

Ophir

, A new elastographic method for estimation and imaging of lateral displacements, lateral strains, corrected axial strains and Poisson's ratio in tissues. Ultrasound Med. Biol. 24, 1183–1199 (1998).

11.

Pesavento

, A time-efficient and accurate strain estimation concept for ultrasonic elastography using iterative phase zero estimation. IEEE Trans. Ultrason. Ferroelec. Freq. Contr. 46, 1057–1067 (1999).

12.

Alam

S. Kaisar

Ophir

, Reduction of signal decorrelation from mechanical compression of tissues by temporal stretching: applications to elastography. Ultrasound Med. Biol. 23, 95–105 (1997).

13.

Chaturvedi

Insana

M.F.

Hall

T.J.

, Testing the limitations of 2-D companding for strain imaging using phantoms. IEEE Trans. Ultrason. Ferroelec. Freq. Contr. 45, 1022–1031 (1998).

14.

Alam

S.K.

Ophir

Konofagou

, An adaptive strain estimator for elastography. IEEE Trans. Ultrason. Ferroelec. Freq. Contr. 45, 461–472 (1998).

15.

Bilgen

Insana

M.F.

, Deformation models and correlation analysis in elastography. J. Acoust. Soc. Am. 99, 3212–3224 (1996).

16.

Ponnekanti

Ophir

Cespedes

, Axial stress distributions between coaxial compressors in elastography: an analytical model. Ultrasound Med. Biol. 18, 667–673 (1992).

17.

Kurz

Mercier

J.P.

Zambelli

, Traité des Matériaux. (Presse Polytechnique, Lausanne, 1989).

18.

Jensen

J.A.

Svendsen

N.B.

, Calculation of pressure fields from arbitrarily shaped, apodized, and excited ultrasound transducers. IEEE Trans. Ultrason. Ferroelec. Freq. Contr. 39, 262–267 (1992).