Improved Spectral Method to Obtain Strains of an Ex-Vivo Membrane Tissue and Its Performance Under Elevated SNRs

In the recent years, ultrasound has become an inspection tool under investigation to explore laminated biological structures to found mechanical or structural changes related to early stages of diseases. The resolution capability of ultrasound to explore these micro-changes not only depends on the frequency, but also in the processing methods applied to extract information from ultrasonic (US) signals. In this paper an analysis is presented to obtain strain values of the wall of a carotid artery segment (from an ex vivo porcine model) during a cyclic variation of the internal liquid pressure. Two methods were used to estimate the wall strain: the cross-correlation, which was considered as the gold-standard option up to 2018, and the SERHH spectral method which has previously demonstrated to obtain ultra-high resolution (0.1%) results on estimating temperature (2009) and wall thickness (2018) variations into biological tissues. Distinct results for the strain variations during the circulatory pressure cycle were detected with both methods (between 0 and 3.5 10⁻² ± 0.6741 for the cross correlation and from 0 up to 3.0 10⁻² ± 0.0488 for our SERHH method). This represents a considerable error of 17% if the cross-correlation options were used Moreover, a precise analysis for evaluating robustness of the SERHH method performance was performed under noised conditions. The original measured signals were added with different noise levels, and then new noise influenced strain values were predicted, for filtered and non-filtered noised signals. Results show that strains obtained for filtered signals almost maintain their original value, presenting small errors for the worst case.