Research On Key Technologies Of Medical Ultrasonic Image Guided Surgery

The technology of image guided surgery is an important part in the field of medicine, which provides the image of lesion area for the doctor to discuss surgery planning according to the image details in preoperative, and provides the surgical instrument's three dimensional coordinate information in the lesion area for the doctor to implement surgery operation through locate the real-time information of surgical instrument's spatial location in intraoperative. The images in image guided surgery are mainly divided into two categories on the basis of images capture time. A kind of image guided surgery is combined with preoperative and intraoperative images, another kind of image is combined intraoperative with intraoperative images in order to real-time guide it. At present in domestic, the first kind of research has been widely used in clinic, and is far more than the second type of research relatively. The second type has advantages of solving the shift of tissues and organs and the deformation caused by breathing, heart rate, pneumoperitoneum et al. So study on this field is very necessary, which can provide theoretical and experimental basis for the following real-time surgical navigation system's establishment. In this paper, the special research on key technologies of medical ultrasonic image guided surgery will have been implemented. The theoretical parts of medical imaging, spatial orientation, surgical instrument calibration, image registration and image display will been introduced, then discussion and experiment will been carried out based on the actual equipment and experiment environment, the works will been done including the following aspects.First of all, the data communication between optical positioning equipment and computer is implemented according to learning and understanding the theory of NDI optical positioning equipment, which mainly contains the collection, send, receive, preserve of three dimensional space information in optical positioning and can quickly provide accurate data information for using optical positioning equipment to carry out the following experiment works.Second, the calibration of surgical instrument is realized, which is an indispensable part of the image guided surgery, aiming at the unity of the space coordinate system. We use ultrasonic apparatus and endoscopic equipment and calibrate the ultrasound probe and endoscopic probe respectively. A surface calibration model and a novel calibration approach for ultrasound images based on optional positioning are designed aiming at ultrasonic probe calibration in this thesis. It can make the best of calibration template. Experimental results show that the calibration error is up to 2.72 mm when calibration images are more than 20. This novel calibration approach works with high precision, operational simplicity, strong flexibility, making it a better choice for the ultrasound image guided surgery. For the endoscopic image calibration, a method is proposed based on Zhangzhengyou's camera calibration. The results show the calibration error is up to 1.81 mm.Finally, ultrasonic images and endoscopic images are matched and displayed. A registration method that based on feature points is proposed combining with the characteristics of two images. This method uses SURF algorithm to selecting and matching feature points. Experimental results show that the method of registration precision and time meet the requirement of image guided surgery navigation's accuracy and real-time display.