| 3D ultrasound imaging system has potential application in clinical evaluation of diseases. And 3D ultrasound imaging system based on magnetic orientation system is a research focus of 3D ultrasound imaging in recent years. In this dissertation, several key problems including calibration and images capturing are in-depth discussed and investigated. A key requirement of 3D ultrasound imaging system based on magnetic orientation system is calibration: determining the position and orientation of the scan-head with respect to the receiver mounted on it. In this dissertation, coordinate systems in the magnetic orientation system and phantom are discussed and methods of coordinate systems conversion among them are presented, which provides the basis in theory for calibration accurately. For calibration problem, a N-shape phantom and a least-squares based on singular value decomposition (SVD) algorithm are presented in this dissertation. The method not only reduces the effect of the thickness and divergence of ultrasound beam, but also improves the test efficiency greatly. The experiment results show that the new method has good performances in precision and accuracy. In design of calibration program, a programming method using mixed programming with Visual C++ and Matlab is presented, which makes full use of the advances of Matlab's strong computing ability and flexible interfere with Visual C++. In the design of images capturing program, the author realizes images capturing continually, play-backing and picking up single frame of BMP image from AVI file via investigating VFW SDK deeply. And the author also sets up a user information database for storing user's materials and the capturing information, which is convenient to browser and pick up information. Meanwhile, the problem of ultrasound images capturing and position information of Bird collecting synchronously are solved by the technique of callback mechanism in VFW SDK, which establishes good foundation for the 3D reconstruction. |
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