Beamforming Scheme for 2D Displacement Estimation in Ultrasound Imaging
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Beamforming Scheme for 2D Displacement Estimation in Ultrasound Imaging Herve´ Liebgott CREATIS, CNRS UMR 5515, Inserm U630, 69000 Lyon, France Email: [email protected]
´ emie ´ Jer Fromageau CREATIS, CNRS UMR 5515, Inserm U630, 69000 Lyon, France Email: [email protected]
Jens E. Wilhjelm Center for Arteriosclerosis Detection with UltraSound, Ørsted-DTU, 2800 Lyngby, Denmark Email: [email protected]
Didier Vray CREATIS, CNRS UMR 5515, Inserm U630, 69000 Lyon, France Email: [email protected]
Philippe Delachartre CREATIS, CNRS UMR 5515, Inserm U630, 69000 Lyon, France Email: [email protected] Received 26 May 2004; Revised 15 December 2004; Recommended for Publication by William Sandham We propose a beamforming scheme for ultrasound imaging leading to the generation of two sets of images, one with oscillations only in the axial direction and one with oscillations only in the lateral direction. Applied to tissue elasticity imaging, this leads to the development of a specific displacement estimation technique that is capable of accurate estimation of two components of the displacement. The mean standard deviation for the axial displacement estimates is 0.0219 times the wavelength of the axial oscillations λz , and for the lateral estimates, it is equal to 0.0164 times the wavelength of the lateral oscillations λx . The method is presented and its feasibility is clearly established by a simulation work. Keywords and phrases: beamforming for ultrasound imaging, axial and lateral displacement estimation, tissue elasticity imaging, laterally oscillating point spread function.
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INTRODUCTION
In medical ultrasound imaging, beamforming can have different aims. In systems generating 3D volumes, sparse synthetic aperture beamforming can be used to maintain a frame rate comparable with existing 2D scanners [1]. Other beamforming techniques can be aimed at estimation of new parameters, like those associated with tissue elasticity imaging [2]. More generally beamforming enables to control many aspects of the image formation like the depth of field or the diffraction of the transmitted beam, and so forth [3, 4]. In this paper, beamforming is introduced in the field of tissue elasticity imaging with ultrasound.
Estimation of elasticity of biological soft tissue with ultrasound deals with the mapping of any parameter characterising the elastic properties of the medium. Examples are Poisson’s ratio [5] or Young’s modulus. The latter has been shown to be highly affected by various pathological conditions [6] and consequently, elasticity imaging carries potential for diagnosing these diseases. The basic principle involved in tissue elasticity imaging with ultrasound or “elastography” is to acquire ultrasound images of a medium in two different states. The first image is used as a reference. Then the investigated medium is compressed, and a second image is acquired. As the medium typically exhibits variations in stiffness, not all of it will have
Beamforming for 2D Displacement
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