Computed Ultrasound Tomography in Echo Mode for Imaging Speed of Sound Using Pulse-Echo Sonography: Proof of Principle

Angular coherence in ultrasound imaging: Theory and applications

“…In this approach, a maximum angular spacing of 30 was used in the cross-correlation calculations for phase-shift estimation. Although the receive F-number and the receive aperture function were not specified by Jaeger et al, 9 we estimated a minimum (i.e., best scenario) receive F-number of 0.5388 from the 20 mm deep object and the 37.12 mm wide transducer for this example. This setting would result in relatively low cross-correlation coefficients between signals acquired with plane wave transmits at any two widely separated angles.…”

“…49 Therefore, the angular coherence theory may provide a method to improve techniques that involves the computation of phase shifts of signals acquired with plane wave transmits. For example, the speed-of-sound estimation technique proposed by Jaeger et al 9 uses phase-shift estimation on beamformed signals acquired with angled plane waves. One of the transmit angular ranges utilized in Jaeger et al 9 is À30 to 30…”

“…For example, the speed-of-sound estimation technique proposed by Jaeger et al 9 uses phase-shift estimation on beamformed signals acquired with angled plane waves. One of the transmit angular ranges utilized in Jaeger et al 9 is À30 to 30…”

“…For example, the cross-correlation coefficient of signals acquired with transmits at 0 and 30 is no greater than 0.65. In the study by Jaeger et al, 9 although a coherent summation of signals within 5 around nominal transmit angles was utilized to improve the estimation, the cross-correlation coefficients of the two aforementioned signals would not exceed 0.71, which is considered to be relatively low for phase-shift estimation standard of above 0.95. 49 Low crosscorrelation coefficient values may increase phase shift estimation jitter and negatively impact the accuracy of speed of sound measurement.…”

“…For example, it has been used in "ultrafast" imaging 4 applications and transient elastography, 1 in color-encoded speckle imaging, 5 to characterize blood flow, 4 to analyze speckle coherence in anisotropic media using backscatter tensor imaging, 6 to obtain functional brain imaging on rodents, 7,8 and more recently in speed-of-sound estimation. 9 Through these applications, PWT-SA has been popularized as a method to achieve high frame rate synthetic transmit aperture imaging 1,10 to improve image resolution everywhere, and to improve sensitivity in Doppler imaging. 4 Despite of the large number of applications, the angular coherence property of signals backscattered from spatially incoherent targets insonified by the plane waves at different transmit angles has not been elucidated.…”