Research On Tumor Motion Compensation Technologies Of Lung Cancer Radiotherapy

Radiotherapy is one of the most effective methods for the treatment of lung cancer tumors in the world.Its main purpose is to radiate tumor cells to the maximum extent,while minimizing the radiation dose to normal tissues and reducing the damage to normal tissues.At present,the conventional radiotherapy method for tumor movement caused by respiration is to enlarge the planned target area.This kind of radiotherapy will cause many normal tissues around the tumor area to enter the field of radiation,which not only causes severe injury to radiotherapy patients,but also increases the risk of complications.The purpose of this paper is compensate the motion of lung tumor in patients effectively while reducing or eliminating the effects of lung tumor motion mainly caused by respiration on radiotherapy.The main works and contributions of this paper are as follows:A tumor motion compensation system for lung cancer radiotherapy is proposed and designed.In view of the problems existing in the motion compensation system of tumor,such as the selection of Two-Dimensional worktable,the shape and size setting of the X-ray baffle,the connection between baffle and worktable,and the design of auxiliary radiotherapy bed,etc.In this paper,the three-dimensional model of the whole tumor motion compensation system is drawn by three-dimensional design software Creo3.0,and the working platform of tumor motion compensation system is built according to the three-dimensional model.Aiming at the problems of compensation lag and system delay in tumor motion compensation system,the extended Kalman filter algorithm is used to predict the tumor displacement through the tumor displacement obtained directly or indirectly in this paper.In addition,the adaptive environment,advantages and disadvantages of the traditional prediction algorithm and the extended Kalman filtering algorithm are compared experimentally,so as to solve the effect of delay and hysteresis in tumor motion compensation system.The experimental results show that the extended Kalman filter can better estimate the state of target in nonlinear environment when compared to the traditional prediction algorithm.In order to realize the optimal control of the motion of the two-dimensionalworktable during radiotherapy to achieve better effect of tumor motion compensation,a pyramid LK optical flow method is used to real-time detect the actual motion of the two-dimensional worktable in this paper.Firstly,the motion of the marking paper placed on the two-dimensional worktable is tracked by a camera fixed on the auxiliary radiotherapy bed,and then the motion of the marking paper is converted to the actual motion distance of the two-dimensional worktable by the calibration parameters,and the detection condition is compared with the given motion control quantity of the two dimensional worktable.Finally,the control quantity is adjusted according to the deviation between the two parameters.The closed-loop control is realized,and the real-time detection of two-dimensional worktable motion is also achieved.In addition,since the motion of lung tumor caused by respiration is most obvious in the upper and lower directions,the tumor displacement in this direction is considered primarily,namely,the movement of the two-dimensional worktable in the upper and lower axis is mainly controlled.