Using ultrasonic guided waves to assess long bone fractures and fracture healing has become a promising diagnostic issue. But the multimode overlap of the guided waves challenges the quantitative evaluation and clinical application. In the preformed study, in order to simplify the signal interpretation, the low-frequency sinusoidial signals were used to only excite SO and A0 modes in fractured long bones. The amplitudes of SO and A0 modes were numerically analyzed with variation in crack width and fracture angle. Numerical simulation, based on the two-dimension finite-difference time-domain （2D-FDTD） reveals that both SO and A0 amplitudes decrease with the fracture widening. However, the increase in fracture angle gradually enhances the A0 amplitude, while with respect to the SO mode, its amplitude shows a non-monotonic trend to the variation in fracture angle with a turning point around 45°. The amplitude ratio between S0 and A0 can reflect the variations in crack width and fracture angles. The simulation illustrates that ultrasonic guided SO and A0 modes are sensitive to the degree of both vertical and oblique fractures in the long cortical bone. These findings may be helpful for fractures diagnosis and healing evaluation of the long bone.
The quadratic transformation method is proposed to estimate the trabecular spac- ing （Tb.Sp）, an important index for osteoporosis diagnosis. The performance of this algorithm was investigated by scatter model, two-dimension finite difference time domain （2D-FDTD） simulation and in vitro experiments of bovine cancellous bone specimens. Comparing with the other four methods autoregressive cepstrum （AR）, adaptive filter- autoregressive cepstral （AFAR）, inverse filter-autoregressive eepstrum （InvAR）, and simplified inverse filter tracking （SIFT）, quadratic transformation is much more stable and accurate. The results demonstrated that quadratic transformation is a great algorithm for Tb.SD estimation.
用超声评价骨质状况是近年来骨质疏松诊断方面的研究热点之一。介绍了超声背散射法及其参量表观积分背散射系数(Apparent Integral Backscatter coefficient,AIB)的测量及与骨矿密度(Bone Mineral Density,BMD)的相关性研究。在体采集了1087位志愿者跟骨的超声背散射信号,并用双能X射线骨密度仪(Dual X-ray Absorptiometry,DXA)测得腰椎和髋骨的BMD值,然后对AIB与BMD进行相关性分析。实验结果表明,参数AIB与BMD显著相关(R=0.58～0.64,n=1087,p<0.05),可被应用于松质骨状况评价。
Ultrasonic backscatter technique has shown promise as a noninvasive cancellous bone assessment tool. A novel ultrasonic backscatter bone diagnostic （UBBD） instrument and an in vivo application for neonatal bone evaluation are introduced in this study. The UBBD provides several advantages, including noninvasiveness, non- ionizing radiation, portability, and simplicity. In this study, the backscatter signal could be measured within 5 s using the UBBD. Ultrasonic backscatter measurements were performed on 467 neonates （268 males and 199 females） at the left calcaneus. The backscatter signal was measured at a central frequency of 3.5 MHz. The delay （-/-1） and duration （7-2） of the backscatter signal of interest （SOl） were varied, and the apparent integrated backscatter （AIB）, frequency slope of apparent backscatter （FSAB）, zero frequency intercept of apparent backscatter （FIAB）, and spectral centroid shift （SCS） were calculated. The results showed that the SOl selection had a direct influence on cancellous bone evaluation. The AIB and FIAB were positively correlated with the gestational age （｜R｜ up to 0.45, P 〈 0.001） when -/-1 was short （〈 8 μS）, while negative correlations （｜R｜ up to 0.56, P 〈 0.001） were commonly observed for T1 〉 10 IJS. Moderate positive correlations （IRI up to 0.45, P 〈 0.001） were observed for FSAB and SCS with gestational age when 71 was long （〉 10 μs）. The 7-2 mainly introduced fluctuations in the observed correlation coefficients. The moderate correlations observed with UBBD demonstrate the feasibility of using the backscatter signal to evaluate neonatal bone status. This study also proposes an explicit standard for in vivo SOl selection and neonatal cancellous bone assessment.
Chengcheng LiuRong ZhangYing LiFeng XuDean TaWeiqi Wang
In this study, ultrasonic backscattering signals in cancellous bones were obtained by finite difference time domain （FDTD） simulations, and the effect of trabecular material properties on these signals was analyzed. The backscatter coefficient （BSC） and integrated backscatter coefficient （IBC） were numerically investigated for varying trabecular bone material properties, including density, Lame coefficients, viscosities, and resistance coefficients. The results show that the BSC is a complex function of trabecular bone density, and the IBC increases as density increases. The BSC and IBC increase with the first and second Lame coefficients. While not very sensitive to the second viscosity of the trabeculae, the BSC and IBC decrease as the first viscosity and resistance coefficients increase. The results demonstrate that, in addition to bone mineral density （BMD） and microarchitecture, trabecular material properties significantly influence ultrasonic backseattering signals in cancellous bones. This research furthers the understanding of ultrasonic backscattering in cancellous bones and the characterization of cancellous bone status.
