Research On Techniques Of Ultrasonic Assessment Of BMD And Ultrasound Imaging

The development in medical ultrasonic engineering can be presented in the following two aspects:1. Application extension, such as quantitative ultrasound in the assessment of bone mineral density and osteoporosis; 2. Improvement in traditional techniques, such as enhancement of imaging quality owing to improved ultrasound imaging techniques. Quantitative ultrasound takes advantage of through-transmission techniques to assess bone density as well as the micro-structure of bones. Ultrasound imaging serves as the most fundamental in the field of medical ultrasound, and images of human's soft tissue can provide further assistance to doctors for making clinical diagnosis.This paper explores researches in quantitative ultrasound assessment of bone mineral density and ultrasound imaging in a combined way, from theoretical analysis, simulations to experimental validation. Firstly, we introduce limitation existing in current studies and propose some new measurement techniques and imaging algorithms for further improvement. Moreover, corresponding simulations and experiments are conducted and the results show that precision and high quality are improved to a great extent, which can indicate the availability of those methods. Detailed research findings are as follow:1. Designing the first nation-wide random-wave-emitting-based ultrasound bone mineral density measurement system, which is used to carry out experiments.2. Proposing a new coding scheme for measuring bone mineral density, which uses Chirp signal to modulate Golay signal,so that Golay_Chirp signal is generated. This resulted signal is equipped with advantages of both Golay and Chirp. Simulations and experiments show that this coding scheme can further strengthen the anti-noise ability and transmission depth of ultrasound signals.3. Introducing the principle of M series in communication to the measurement of broadband ultrasonic attenuation. Compared to other coding signals, M series can be easily generated, simply emitted and with longer code length, therefore it is more suitable in bone mineral density measurement, also improvement in precision can be displayed from experiments.4. Incorporating AR model in broadband ultrasonic attenuation measurement to overcome the problem of noise influence, acute ups-and-downs in the attenuation curve. Proposing the method for determining order in the application of AR model. Simulations and experiments show that. adopting high order in AR model can smooth . attenuation curve and improve measuring precision. Applying broad-band ultrasound traducer in measuring broadband ultrasonic attenuation and a linear relationship of broadband ultrasonic attenuation and frequency is found in the frequency range of 0.4-1.8MHZ. This result is instructive in its ability of further widening band width.5. In the speed-of-sound measurement, the inherent delay of the system is removed by linear fitting method, which improves the speed-of-sound measurement accuracy effectively.6.Analyzing the principles of ultrasound imaging and making in-depth exploration in the code-emitting and adaptive beamforming technique, novel imaging method with a combination of the above two is proposed and Field II is used to make simulations. An obvious improvement in contrast and resolution is observed in the results.As major techniques of medical ultrasound, quantitative ultrasonic assessment of BMD and ultrasonic imaging have always been the research focus in related fields. This paper explored the improvement in measuring precision and imaging quality, which can lower the rate of erroneous diagnosis. The research results introduced here is not only unique in theory innovation but also of high practical value.The author acknowledges the support of the National Natural Science Foundation of China (Grant Nos.60471057,60871087) and 2008 Innovation Foundation for Graduates, USTC.