A Portable Ultrasonic Testing System For Soft Tissue Properties

The aim of the thesis is to design a portable ultrasonic testing system for soft tissue properties. The system extracts the thickness and elasticity of soft tissue with the sensor which combines an ultrasonic probe and a pressure sensor. The difficulty of the system is the testing of elasticity, of which the general method is to obtain elastic parameter by estimating the deformation of soft tissue under different pressure.The deformation information is obtained from ultrasonic echo time delay. As there are many algorithms for time delay estimation, we designed an ultrasonic deformation testing and calibrating system and did considerable experiments to compare the accuracy and speed of several algorithms, two of which - Direct Correlation and SSD were selected. Direct Correlation algorithm was adopted in our system eventually.The design of the system's hardware is based on the work of a former graduate. I improved the ultrasound emitting and receiving circuits, designed the circuit for pressure sensor, and improved the DSP circuit and A/D unit for ultrasound and pressure signals. The system's power, the circuits and the combined sensor were integrated into a portable box.The system's software implemented in DSP has good user interface, obtains the thickness and elastic parameter by processing the ultrasound and pressure signal.Finally, the system was calibrated using pig's muscle as specimen, which showed the maximal deviation of measuring deformation is 132μm, and the maximal deviation of measuring thickness is 144μm. And the elastic parameter of several soft tissues were tested with the system.