Yang Jianxi

Calibrating method and systemic error analysis on binocular 3D position system

This paper focuses on the problems appeared during the camera calibration of the binocular vision system. Through the analysis on the data of the various points and the large quantities of the tests with the binocular position-setting system (BPS), it is noted that the biggest error appears on the z direction when the 3-D coordinate is re-built. The larger in the distributing area of the selected calibration points on the depth and the larger in the application of the camera model, according the less in errors. It is shown that the 3-D coordinate error will be small with more selected calibration points. In the system, the errors are caused by two major factors which are considered to be the uncertain centre of the image and the incorrect virtual world coordinates. The distortion of the camera lens is not considered in this study while the results can be used under the condition of distortion.

Design of a Computer Aided Surgical Navigation system based on C-arm

Though the conventional C-arm fluoroscope is used in bone surgeries for decades, two outstanding disadvantages remain. One is that it is not well adapted to the image-guided orthopaedic surgery procedures. Another is exposure of patients and surgeons in the radiation environment are harmful. At present, computer aided surgical navigation system is more and more used in surgery, but it is only connected to MRI ( magnetic resonance imaging ) or CT (computerised tomography ). This research addresses these issues. Using the C-arm and binocular spatial position system to navigate, with the help of the computer, is studied in our laboratory. The new system is called CASNC (Computer Aided Surgical Navigation system based on C-arm). As a special example, the position of determining distal interlocking of tibia or femoral intramedullary nail using the CASNC system is also a main point in this research. The position of the C-arm and patient are detected at the same time when a preoperative patient X-ray fluoroscope was taken, and transfer them to the computer. Then the system has to establish a correlation between preoperative image data and intraoperative patientpsilas position and surgical tools. At last, the deviation of the spatial position of the hole on the nail and surgical tools are shown on the monitor, and it illustrates correct position and orientation. This system not only can maximise the advantages of the conventional C-arm and accuracy of drilling, but also reduce surgeon and stuff in the operating theatre, especially patients suffering the X-ray radiation exposure.