Preliminary Development Of Cancellous Bone Trabecular Spacing Estimation Algorithm And Ultrasound Diagnostic System

As the aged population grows, osteoporosis has caused tremendous damage to the society. How to diagnose osteoporosis effectively and accurately is a very important issue for researchers. Applying ultrasonic methods for osteoporosis diagnosis offers advantages including lack of ionizing radiation, portable and low cost. Among all the ultrasonic signals, backscatter signal from cancellous bone has been receiving more attentions due to its unique advantages. This thesis mainly focuses on two aspects. Firstly, this thesis studies the algorithms which estimate mean trabecular bone spacing (MTBS) from ultrasonic backscatter signals in cancellous bone. Secondly, the work of preliminary development of a medical device which diagnoses osteoporosis by analyzing ultrasonic signals in cancellous bone has been proposed.Trabecular bone spacing is one of the important parameters for characterization of bone microstructure. Two novel MTBS estimation methods were presented in this thesis. (1) The simplified inverse filter-fundamental frequency estimation (SFE) was proposed. The SFE algorithm first utilizes simplified inverse filter to remove the high frequency multiplicative interference of system response, and then the combination of event-based instantaneous fundamental frequency estimation method and improved auto-correlation algorithm are applied. Finally, the estimated MTBS can be obtained from the estimated fundamental frequency. Through simulation and in vitro experiments, it can be concluded that the SFE algorithm is more robust to interference with accurate estimates compared with simplified inverse filter tracking (SIFT) algorithm and autoregressive (AR) cepstrum method. (2) Basing on SFE algorithm, this thesis proposed the second MTBS estimation method named as Hilbert transform-fundamental frequency estimation (HFE), which was proved to be a more robust algorithm than SFE method, especially for varying SNR and MTBS. The robustness for other two kinds of interference has also been improved,In the work of preliminary development of the medical device, this thesis first gives the design requirements for the front-end circuit, which transmit/receive ultrasonic signals to/from cancellous bone. Then the interface which processes the ultrasonic signals from front-end circuit and displays the diagnosing results has been designed in ARM development board. And the driver programs to control front-end circuit and transmit ultrasonic signals have been developed. Finally, the acquired in vivo ultrasonic backscatter signals were processed by the two proposed methods (SFE and HFE) and SIFT, from which the MTBS were obtained. The significant correlations were found between MTBS (which were estimated from SFE, HFE and SIFT) and stiffness index (SI) (obtained by GE Lunar Achilles Express), whose results were R2=0.63, R2=0.71, R2=0.78 (p<0.01) respectively. The research indicated that the preliminary developed device can be used to estimate MTBS of cancellous bone and assess the cancellous bone conditions.