Amplitude-based echo-mode speed-of-sound tomography
arXiv:2607.26721
The paper introduces an amplitude‑based method for echo‑mode ultrasound tomography that reconstructs speed‑of‑sound maps with higher resolution and fewer artifacts than the traditional phase‑shift (dToF) approach.
Abstract
The tissue's speed of sound (SoS) is a promising marker for non-invasive and zero-dose diagnosis of diseases such as cancer or liver steatosis. Computed ultrasound tomography in echo mode (CUTE) retrieves spatially resolved SoS using pulse-echo ultrasound, by analysing the variation of echoes when probed with varying pairs of transmit- and receive-steering angles. This analysis conventionally focuses on the echo phase shift, which is interpreted as differential time-of-flight (dToF) and related to SoS. While promising results have been obtained, the trade-off between beamwidth and angular aperture not only limits spatial resolution but also leads to artefactual noise in media with short-scale SoS variations. To overcome this limitation, we propose an alternative approach: for each echo, instead of reducing the angle-dependent variations to a single parameter (the dToF), we retrieve aberration profiles with sub-beamwidth resolution by inverting a model that relates these profiles to the echo amplitudes detected for all angle pairs. We demonstrate in simulations that this amplitude-based (a-CUTE) approach results in substantially improved spatial resolution and reduced artifacts compared to dToF-CUTE. Physical phantom and preliminary in vivo results confirm the feasibility of this novel method in physical data.