Research On Key Technologies Of Ultrasound Image Guided Prostate Brachytherapy Surgery System

Surgical navigation system is a comprehensive research project which integrates computer graphics,medical image processing,spatial positioning technology and clinical surgery.The doctor can take the surgery on patients' organ lesions more intuitively and accurately by using the surgical navigation system.It is conducive to improve the effect of surgical treatment and the success rate of the operation.The navigation system also has great significance to reduce the labor intensity of doctors and trauma to patients.In this paper,the key technologies of the brachytherapy system for prostate brachytherapy are deeply studied.The main contents and results are as follows:(1)An improved "N" calibration template calibration method based on the electromagnetic tracking system is proposed to calibrate the 2D ultrasound probe together with the Square-Distance-Weighted parallel interpolation reconstruction algorithm.And then the 2D ultrasound images captured after the probe calibration were reconstructed in 3D space.The main usage of this method is to add 3D positon informantion into ordinary 2D ultrasound image.The experimental results show that the whole reconstruction process costs 5-10 minutes and the calibration method and the reconstruction algorithm have high precision and wide practicability.(2)In this paper,a rigid registration algorithm based on mutual information is proposed,which is mainly aimed at the image registration when the deformation area of ultrasound image is small.After the preprocessing of ultrasound images,this method is used to register processed ultrasound images to MRI images,which almost achieves a real-time registration speed.It is important to improve the accuracy of seeds inserting in the brachytherapy surgery by using the registered ultrasound images.(3)Another deformable registration algorithm based on the principal axes algorithm and Renyi similarity metric is proposed.The algorithm is used to improve the registration accuracy when the ultrasound image has large deformation field compared with MRI(or CT)image during the registration of the ultrasound images to MRI(or CT)images.With the help of rapid initial registration used in the principal axes algorithm,the registration speed of Renyi deformable registration algorithm is improved.The experiment results show that compared to the rigid registration algorithm,the registration accuracy has been significantly improved.(4)An improved registration algorithm based on ICP is proposed,which solves the problem of the mapping between the patient actual space and the image virtual space in the navigation system.The algorithm can achieve high spatial registration accuracy with a small number of registration points.It can simplify the process when using the navigation system and improve the practicability of the navigation system.The registration accuracy of the algorithm can meet the requirement of clinical accuracy through the dummy model experiment.(5)The surgery navigation system for the prostate brachytherapy is designed and built which contains the operation auxiliary robot,ultrasound machine,electromagnetic tracking system and the TPS software.The surgical navigation system was tested by using the male pelvic organs of group model to simulate an implantation surgery.In the simulated surgery,the improved quaternion spatial registration algorithm was used to locate the template,and the ultrasound images were registered to CT images by using the mutual information based rigid registration method and deformable registration algorithm to navigate the seeds insertion.The results of experimrnt show that the surgical navigation system achieves high navigation accuracy.The navigation system was also validated by prostate biopsy clinical operation.The results show that the target puncture is basically realized with the assistance of navigation system,and the effectiveness of the navigation system is illustrated.