Research On Key Technology Of Bone Density Measurement By Quantitative Ultrasound

Quantitative ultrasonic diagnosis for osteoporosis has become one of the most potential methods to measure bone density for its low-cost,no radiation and other advantages.At present, the domestic quantitative ultrasound measuring instruments mostly come from the import.In view of this situation,development of quantitative ultrasound measuring instruments that possess independent intellectual property is a universally concerned topic in domestic medical field.The design of high-powered ultrasonic transducer and the data acquisition and processing of ultrasonic signal are two key technologies that are of importance to the development of the whole instrument. In this paper,the two key technologies are emphatically studied.On the basis of analyzing the basic theory and the measuring principle of quantitative ultrasound,ultrasonic transducers of measuring BMD and the suited circuit are designed.The circuit is simulated by Pspice and the suited circuit which can meet the needs of emission and measurement is gained.Contrasting experiments have been carried on ultrasonic transducers with different design parameter.The relation between design parameter and performance of the transducer is obtained.The experiment indicates that when proportion of tungsten in damp block and number of matching layer are increased,the peak to peak value of response wave decreases gradually and the number of oscillations decreases too.Reasonable proportion of tungsten in damp block and number of matching layer are determined through a compromise between design parameters and sensitivity of transducers.Based on pulse transmission technology,the method of measuring quantitative ultrasound parameters is discussed in detail so as to obtain ultrasonic parameters accurately.An ultrasonic signal data acquisition and processing system based on TMS320F2812 is designed and developed by utilizing the existing conditions in the lab.12-bit ADC of the chip used in the data acquisition part.Both transmitting signal and receiving signal are controlled and collected synchronously. Measurements are made both with sample and without sample and the two received signal are obtained.The time lag cross-correlation is made to relate transmitting signal with receiving signal filtered by elliptic band-pass digital filter,and propagation time and speed of ultrasound are obtained.Fourier Transforms of the two received signal obtained by measurements which are made with and without sample are contrasted so as to obtain broadband ultrasound attenuation of samples.Propagation speed and broadband ultrasound attenuation of several samples are estimated and the values of two parameters can characterize the feature of samples.The anticipated effect of parameter measurement is achieved.