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, nonionizing 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(T_1) and duration(T_2) of the backscatter signal of interest(SOI) 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 SOI 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 T_1 was short(< 8 μs), while negative correlations(|R| up to 0.56, P < 0.001) were commonly observed for T_1 > 10 μs. Moderate positive correlations(|R| up to 0.45, P < 0.001) were observed for FSAB and SCS with gestational age when T_1 was long(> 10 μs). The T_2 mainly introduced fluctuations in the observed correlation coefflcients. 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 SOI selection and neonatal cancellous bone assessment.
Chengcheng LiuRong ZhangYing LiFeng XuDean TaWeiqi Wang
Single pulse excited ultrasonic guided wave surfers high attenuation during the propagation in long bones.This results in small amplitude and low signal-to-noise ratio(SNR)of measured signals.Thus,the Barker code excitation is introduced into long bone detection to improve the quality of received signals,due to its efficiency in increasing amplitude and SNR.Both simulation and in vitro experiment were performed,and the results were decoded by the weighted match filter(WMF) and the finite impulse response- least squares inverse filter(FIRLSIF),respectively.The comparison between the results of Barker code excitation and sine pulse excitation was presented.For 13-bit Barker code excitation,WMF produced 13 times larger amplitude than sine pulse excitation,while FIR-LSIF achieved higher peak-sidelobe-level(PSL) of —63.59 dB and better performance in noise suppression.The results show that the Barker code excited guided waves have the potential to be applied to the long bone detection.
In the application of cancellous bone ultrasound diagnosis based on backscattering method,it is of great importance to estimate fast and accurately whether the valid backscattering signal exists in the received signal.We propose a fast estimation method based on spectrum entropy method.With 984 records of adult calcaneus clinical data,we estimate the validity of the backscatter signal using this method.The results of the proposed method and the results of experience-base judgement were compared and analyzed.And two key parameters,the signal range length and the segment number of the spectrum entropy,were analyzed.The results show when the signal range length is 13 us and the segment number is 15-20,this method can get the best result(accuracy>95%,sensitivity>99%,specificity>87%),while taking little calculation time(1.5 ms).Therefore,this spectrum entropy method can satisfy the accuracy and real-time requirements in the ultrasonic estimation for cancellous bone.
