Research On Ultrasonic Backscattering Measurement In Bones

Osteoporosis is a disease caused by lack of calcium, phosphorus and otherminerals. Since it is very difficult to treat with current medical devices, preventionis important. In China, the situation is even more serious due to the large populationand aging, results into the requirement of simple and effective diagnostic methods.Quantitative ultrasound (QUS), which is economic and radiation free, have beenwidely used in many medical fields. The commonly methodsin measuring bonemineraldensity is to characterize the changes in bone density with ultrasonicpropagation. This technique is easy to operate, but it cannot reveal the bonemicro-structure information. Ultrasonic backscattering, a new methodtaking accountof lots of micro-structural information has shown a brighter future.This paper studies how to effectively extract the mean trabecular spacing fromthe backscattered signals, the main work includes:1. Established two simplemodel,based on ultrasound propagation in cancellousbone. Then the relationship between the backscattered signal and the micro-structureof the bone were analyzed, which is as the foundation of singular spectrum analysis(SSA) in extracting mean trabecular spacing. Finally,coded excitation technologywas applied to improve the accuracy in measurements.2. Built an ultrasonic system with front-end and back-end. Front-end includestransmitting and receiving circuit based on FPGA. Back-end includes acquisitioncard, PC, and the LABVIEW-based program with interface and signal processing.This system can be used in the ultrasonic echo signal collection.3.Built a model to simulate bone tissue and ultrasound probe. TestedtherobustnessofSSAmethodbychangingtheboneandsignal.Then, in a noise-containingsystem, sent coded ultrasound signals to the bone. The result demonstrated that thecoded excitation technique can effectively improve the accuracy of the SSA method.4. After setting up a experimental system and producing calibratedsamples, SSA method was used to analyze the collected backscattered signals.Comparing the results before and after encoding, SSA methods and coded excitationtechnology is feasible in the measurement of MSS.