Experimental comparison of acoustic backscattered field from a single fiber and media with pseudo-aligned fibers in longitudinal and transverse planes

Acoustic backscatter spectrum analyses of soft tissues are being developed to provide quantitative information beyond that offered by B-mode images. Common assumptions used in some approaches are that the medium is homogeneous, isotropic, and produces diffuse scattering conditions. However, in some soft tissues, the presence of fiber-like structures causes the acoustic backscatter to be anisotropic. In this work, we compare the backscattered fields produced by a single fiber, a phantom containing many pseudo-aligned fibers, and biceps muscle. Measurements were performed with single-element immersion transducers using a laboratory benchtop pulse-echo setup, and different linear array transducers on a Siemens Acuson S3000 scanner. The phantom and muscle were imaged in longitudinal and transverse planes to study the effect of fiber orientation on the backscattered field. The results showed that the normalized backscattered power is different in longitudinal and transverse planes. This can result from differences in the sonicated portion of the fibers when varying their orientation with respect to the 3D diffraction pattern. Future work will further study this phenomenon with single fibers and transducers with different focal configurations, and investigate the use of the point-wise signal-to-noise ratio and the generalized spectrum to detect the presence of coherent scattering conditions.