Echo-mode aberration tomography: Sound speed imaging with a single linear array

Abstract

Tomographic sound speed imaging has previously demonstrated the capability of producing images of comparable quality to that of X-ray CT and MRI. Traditionally, such reconstructions have only been achievable in transmission mode, either using diametrically opposed linear arrays or ring arrays. This is due to the conventional wisdom that forward scatter data are necessary for reconstruction in the general case, and consequentially, such setups are typically limited to easily externalized, soft tissues such as the female breast and thus are impractical for clinical usage. Recently, it has been demonstrated that in the presence of diffuse scatterers (Jaeger, 2015), pulse-echo reconstructions of slowness (inverse sound speed, proportional to refractive index) is feasible with a conventional single conventional linear array. By correlating data acquired with steered plane wave transmissions, depth dependent maps of phase lags can be generated and subsequently used to solve a multilinear inverse problem. The resulting images allow for baseband, speckle-free characterization of the underlying medium, which is complementary to the data acquired in traditional B-mode ultrasound. In this presentation, the fundamentals of echo-mode aberration tomography will be reviewed, completely with algorithmic formulation, beamformation considerations, and current challenges in practical reconstruction.