Effects of Tissue Anisotropy on the Spectral Characteristics of Ultrasonic Backscatter Measured with a Clinical Imaging System

Abstract

In this paper, we report the effects of inherent tissue anisotropy on the spectral properties of backscattered ultrasound when measured with a commercially-available imaging system. We insonified five specimens of bovine tendon immersed in a water tank and rotated in 10 degrees increments while being imaged with a Hewlett-Packard Sonos 1500 system. The backscattered RF signals corresponding to each angle of insonification were digitized and the spectral characteristics of the backscattered ultrasound were determined. The mean anisotropy, defined as the average difference between values at perpendicular and parallel insonification, for band-limited estimates of backscattered power, centroid frequency, upper-band to lower-band power ratio, and upper-band to total-band power ratio were found to be 24.6 +/- 1.1 dB, 142 +/- 27 kHz, 32 +/- 13%, and 22 +/- 5%, respectively (mean +/- SE). The magnitude of each of these backscatter spectral parameters was larger at perpendicular insonification compared with the corresponding values at parallel insonification, consistent with previous measurements of the inherent anisotropy of ultrasonic attenuation and backscatter in tissue.

Elasticity standard values of the Achilles tendon assessed with acoustic radiation force impulse elastography on healthy volunteers: a cross section study

“…The Achilles tendon is an anisotropic organ. As such, the physical parameters change depending on the angle in which the ultrasound waves meet the tendon fibres [ 14 – 17 ]. Accordingly, shear waves spread faster along the fibres than transversely to them [ 8 , 18 ].…”

Echocardiographic-Based Assessment of Myocardial Fiber Structure in Individual, Excised Hearts

“…18,22,26,39,40 This relationship was established using an approach previously described by our laboratory. 41,42 Five cylindrical myocardial specimens (approximately 15 mm in diameter) were cored from a separate set of fixed sheep hearts. The relationship between the level of apparent backscatter with the angle of insonification relative to the myofibers was obtained by rotating the cylindrical myocardial specimens in the imaging plane, in 5-degree increments, as depicted in Figure 2, with the echocardiographic imaging system configured (in the manner described above for imaging intact hearts) to provide grayscale images that were subsequently analyzed to provide quantitative estimates of the level of backscattered energy.…”

Effects of tissue mechanical and acoustic anisotropies on the performance of a cross-correlation-based ultrasound strain imaging method

“…In addition to the anisotropic mechanical properties, the fiber structures of striated muscle also lead to view-dependent ultrasonic backscatter, which was found to vary with the angle between the incident ultrasound beam and the local tissue fiber orientation (Wild and Reid 1953, Mottley and Miller 1988, Dekroon et al 1991, Hoffmeister et al 1995, Holland et al 1998a. The backscattered ultrasonic signal intensity from muscles is higher when incident ultrasonic waves are perpendicular to the muscle fibers than when ultrasonic wave propagation is parallel to those fibers; this is termed acoustic anisotropy in our study.…”