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In recent years, with the improving of the living standards and the extending of the life expentancy, the aging of the population becomes obvious, more and more Osteoporosis (OP) patient raises the concern of the whole society. The diagnosis and treatment of Osteoporosis have become the hot research issue in the international academic community and medicine. The diagnosis of OP is mainly based on the measure of Bone Mineral Density(BMD). Currently, the methods of measuring BMD mainly include Single-photon Absorptiometry (SPA), Dual-photon Absorptiometry (DPA), Single-energy X-ray Absorptiometry (SXA), Dual-energy X-ray Absorptiometry (DXA), Quantitative CT (QCT) etc. Because the X-ray applied in these methods has harmful radiation to human bodies, so in this thesis, the measurement of BMD using nonradiative ultrasound has been designed, the innovative achievements we have gained are shown below:Firstly, the calcaneus which contains a lot of cancellous bone has been selected as the measuring part, thus overcomes the problem of using ultrasound to measure the bone. Previously, because of the attenuation characteristics of ultrasound, the attenuation is not obviously when ultrasound through the normal bone. In our design, the cancellous bone which is a high-attenuation material to utrasound causes the signal before and after passing through the calcaneus changing greatly, so it is easy to measure and meets the purpose of diagnosis.Secondly, circuit of measuring system has been designed, including ultrasound transmitting circuit, ultrasound receiving circuit, sample circuit, FPGA and USB circuit. In the design of transmitting circuit, a unique dual-pulse control is applied. Compared to the previous methods which control the enlarged signals, our method is much more faster to control the ultrasound. In addition, the receiving circuit and transmitting circuit are designed altogether and only a isolating-limited circuit between them, ultrasound can be sent and received in different time, voiding to switch the probe from time to time in the traditional design and making the generated amplitude of ultrasound to be more stable.Thirdly, a software of measuring BMD using QUS has been designed and improvement has been made on the transmitting mode of single pulse, fixed frequency in traditional ultrasound measurement. Frequency, pulse-number and the repeated time of transmitting pulses can be changed conveniently, providing the conditions to further advance the measuring accuracy of the system.Based on the theory of QUS and combined with the hardware and software design, the prototype machine has been successfully produced. The test results show that the performance of the system meet the expected requirements.
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