Key Technologies Of Ultrasound Image Guided Navigation For Intervention Surgery

Navigation for intervention surgery is aimed to help surgeon employ tracked surgical instruments in conjunction with preoperative or intraoperative images in order to indirectly guide the operation. It is a cross discipline combining positioning technology, medical imaging, image processing and so on. There are many positioning techniques such as optical tracking technique, electromagnetic positioning, mechanical positioning and other position techniques. By comparison, optical tracking technique has been used because it is anti-electromagnetic interference and flexible in operation. In addition, common used CT and X-ray lead to radiation damage to patients, and MRI has a kind of grayscale distortion and geometric distortion, adding error to some extent. In contrast, ultrasound has an advantage in low price and real-time imaging. So, this thesis studies on key technologies of ultrasound image guided navigation for intervention surgery based on optical positioning. The research results are as follows:Firstly, a surgical instrument tip calibration method based on the maximum correntropy criterion (MCC) is proposed to deal with the mark coordinate flutter caused by background conditions under optical positioning. Experiments show the proposed method is more accurate and need less images to reach the same accuracy than LMS.Secondly, a rapid and automatic ultrasound calibration method is presented, which is using optical positioning calculate tip coordinate instead of complicated calibration model. Besides, the tip in images is selected by image processing to overcome the random error elicited by manual selecting and to save much calibration time.Moreover, the medical image segmentation based on Local Gaussian Distribution Fitting (LGDF) model is sensitive to initial contour and parameter selection. If its initial contour chosen manually is not suitable, the segmentation is even unsuccessful because of being lost in local minima. In addition, the algorithm speed is slow. To solve these problems, an automated image segmentation based on improved LGDF Model is proposed.Finally, some simple instruments are designed by using balls as the mark and recognized using balls'colour information. After instrument calibration, ultrasound probe calibration, instrument recognition, accuracy test and track test, the thesis establishes navigation for intervention surgery demo system. The simulation experiments show that the navigation demo system satisfies accuracy and real-time requirements of navigation for intervention surgery.