Ultrafast compound imaging for 2-D motion vector estimation: application to transient elastography

• Published in: IEEE transactions on ultrasonics, ferroelectrics, and frequency control ferroelectrics, and frequency control, 2002-10, Vol.49 (10), p.1363-1374
• Main Authors: Tanter, M., Bercoff, J., Sandrin, L., Fink, M.
• Format: Article
• Language: English
• Subjects: Acoustic signal processing; Acoustical measurements and instrumentation; Acoustics; Algorithms; Array signal processing; Beamforming; Biological and medical sciences; Displacement measurement; Elasticity; Equipment Design; Exact sciences and technology; Frames; Fundamental areas of phenomenology (including applications); Humans; Image Enhancement - instrumentation; Image Enhancement - methods; Imaging; Investigative techniques, diagnostic techniques (general aspects); Mathematical analysis; Medical sciences; Miscellaneous. Technology; Models, Statistical; Motion; Motion estimation; Phantoms, Imaging; Physics; Plane waves; Quality Control; Reflectivity; Sensitivity and Specificity; Speckle; Stress, Mechanical; Tracking; Two dimensional displays; Ultrasonic imaging; Ultrasonic investigative techniques; Ultrasonic variables measurement; Ultrasonography - instrumentation; Ultrasonography - methods; Vectors (mathematics); Vibration measurement; Video Recording - instrumentation; Video Recording - methods
• ISSN: 0885-3010; 1525-8955
• DOI: 10.1109/TUFFC.2002.1041078

This paper describes a new technique for two-dimensional (2-D) imaging of the motion vector at a very high frame rate with ultrasound. Its potential is experimentally demonstrated for transient elastography. But, beyond this application, it also could be promising for color flow and reflectivity imaging. To date, only axial displacements induced in human tissues by low-frequency vibrators were measured during transient elastography. The proposed technique allows us to follow both axial and lateral displacements during the shear wave propagation and thus should improve Young's modulus image reconstruction. The process is a combination of several ideas well-known in ultrasonic imaging: ultra-fast imaging, multisynthetic aperture beamforming, 1-D speckle tracking, and compound imaging. Classical beamforming in the transmit mode is replaced here by a single plane wave insonification increasing the frame rate by at least a factor of 128. The beamforming is achieved only in the receive mode on two independent subapertures. Comparison of successive frames by a classical 1-D speckle tracking algorithm allows estimation of displacements along two different directions linked to the subapertures beams. The variance of the estimates is finally improved by tilting the emitting plane wave at each insonification, thus allowing reception of successive decorrelated speckle patterns.