Experimental validation of a novel technique for ultrasound imaging of cardiac fiber orientation

The arrangement of cardiac fibers determines mechanical and electrical properties of the heart and can be altered due to pathology. Hence, the non-invasive assessment of fiber characteristics is of interest from both a pathophysiologic and a diagnostic point of view. Recently, we proposed and validated, by computer simulations, a theoretical framework to have more insight on 3D ultrasound Backscatter Tensor Imaging. The theory showed that spatial coherence (SC) maps of echo signals, across the probe aperture, not only carry information on fiber direction, but also on fiber size and pitch. The aim of this study was to experimentally validate these findings and conduct preliminary in vivo tests. Experiments were conducted on a purposely designed and built phantom consisting of several sets of parallel nylon wires, having different diameter (S) and pitch (P). Finally, preliminary tests were conducted on the biceps of healthy volunteers. Experiments confirmed the simulation results: averaged over all acquisitions, the main-to-secondary lobe distance linearly correlated with P (R 2 =94%), while the value of the SC at lag 1 (an estimate of the main lobe width) linearly correlated with S (R 2 =48.6%). In vivo results demonstrated the feasibility of extracting microstructural information of the tissue by the analysis of SC maps.