Effects of Phase Cancellation and Receiver Aperture Size on Broadband Ultrasonic Attenuation for Trabecular Bone In Vitro

Abstract

Phase cancellation in ultrasound due to large receiver size has been proposed as a contributing factor to the inaccuracy of estimating broadband ultrasound attenuation (BUA), which is used to characterize bone quality. Transducers with aperture size ranging from 2 to 5 mm have been used in previous attempts to study the effect of phase cancellation. However, these receivers themselves are susceptible to phase cancellation because aperture size is close to one center wavelength (about 3 mm at 500 KHz in water). This study uses an ultra small receiver (aperture size: 0.2mm) in conjunction with a newly developed 2-D synthetic array system to investigate the effects of phase cancellation and receiver aperture size on BUA estimations of bone tissue. In vitro ultrasound measurements were conducted on 54 trabecular bone samples (harvested from sheep femurs) in a confocal configuration with a focused transmitter and synthesized focused receivers of different aperture sizes. Phase sensitive (PS) and phase insensitive (PI) detections were performed. The results show that phase cancellation does have a significant effect on BUA. The normalized BUA (nBUA) with PS is 8.1% higher than PI nBUA while PI BUA is well correlated with PS BUA. Receiver aperture size also influences the BUA reading for both PI and PS detection and smaller receiver aperture tends to result in higher BUA readings. The results also indicate that the receiver aperture size used in the confocal configuration with PI detection should at least equal the aperture of the transmitter to capture most of the energy redistributed by the interference and diffraction from the trabecular bone.

Estimation of fast and slow wave properties in cancellous bone using Prony's method and curve fitting

“…Experimental errors in measurements on cancellous bone arise from many factors, including phase cancellation (Wear, 2007(Wear, , 2008Cheng et al, 2011), refraction artifacts, multipath interference, and errors in diffraction correction in substitution experiments due to mismatch in velocity between sample and water. This last effect, which has been studied extensively (Xu and Kaufman, 1993;Kaufman et al, 1995;Droin et al, 1998) is especially problematic for the fast wave, for which the mismatch can be approximately 500 m/s.…”

Three-dimensional Simulation of Quantitative Ultrasound in Cancellous Bone Using the Echographic Response of a Metallic Pin

“…However, a slightly nonlinear relationship is obtained between BV/TV and SOS, with a peak around 30 or 35%, as shown in Fig. 7(a 45 may occur, which may be due to a nonlinear variation of the attenuation coefficient as a function of frequency 48 and therefore a modification of the BUA value. Note that in this case, BUA cannot be defined.…”

Conventional, Bayesian, and Modified Prony's methods for characterizing fast and slow waves in equine cancellous bone

“…However, the two-mode propagation models used both in this study and in Wear et al (2014) are quite similar, and it is possible that the models are not properly accounting for all the experimental factors. Possible contributions for the systematic dependences on sample length that are not explicitly taken into account in the model include diffraction effects (Xu and Kaufman, 1993;Kaufman et al, 1995), phase cancellation at the face of the finite aperture phase-sensitive receiving transducer (Langton and Subhan, 2001;Bauer et al, 2007;Wear, 2007;Wear, 2008;Cheng et al, 2011), refraction artifacts, and multipath interference.…”