Precise Isotropic Displacement Tracking with Coherent Multi-Transducer Ultrasound allows Full Normal/Shear Strain Estimation in 2D Elastography

In strain elastography, tissue strain maps are derived from the spatial derivatives of the displacement field, estimated before and after a small compression. However, precise ultrasound based displacement estimation in all directions remains challenging, especially in the lateral direction, due to lower resolution and lack of phase information.In this work, a coherent multi transducer ultrasound (CoMTUS) approach is used, where data from multiple probes are combined coherently to extend the effective aperture, which increases resolution, SNR, and field of view. The improvements in 2D displacement and strain estimation using a two probe CoMTUS system were experimentally evaluated against a single probe setup. CoMTUS greatly increases tracking precision in lateral direction, resulting in a more isotropic distribution of displacement estimates. CoMTUS normal strain maps outperform the single probe case in lesion detectability and contrast, where the generalized contrast-to-noise ratio (gCNR) increased from 0.58 to 0.96. CoMTUS shear strain maps show reduced background noise and improved definition of shear strain around the lesion.Overall, CoMTUS enables more isotropic displacement tracking, leading to robust estimation of both normal and shear strain components. This may allow accurate estimation of the full strain tensor, expanding the capabilities of ultrasound elastography.