Study of the Impact of Probe Steering Capability on the Performance of Off-Axis Measurements of Backscattered Signals

In the field of quantitative ultrasound (QUS), several studies have been conducted to parameterize tissue anisotropy by measuring the angular dependence of the backscatter coefficient (BSC). Early foundational studies utilized a single-element transducer, and more recent ones using ultrasound linear array probes. However, probe features such as directivity and crosstalk can strongly affect both, the transmission of an ultrasound beam and the measurements of the backscattered signals, independently of the imaging strategy used, either the focused beam steering or the plane wave imaging. In this work, we present a comparative analysis between a Capacitive Micromachined Ultrasonic Transducer (CMUT) probe and a commercial piezoelectric probe, in which the BSC is measured using the focused beam steering imaging strategy on isotropic and anisotropic tissue-mimicking phantoms along different insonification angles. The results show how the limited steering capabilities of linear probes can affect the measurement of BSC, and in general, the anisotropic QUS parameters, bringing into discussion their consideration in the development of experimental strategies for the assessment of tissue anisotropy.