| Heavy ion radiotherapy is one of the effective methods for accurate and noninvasive treatment of tumors at present.In the process of radiotherapy,due to the influence of various factors,the location of the tumor will shift in the normal position,resulting in the damage of normal tissue in the treatment,and the radiotherapy of cancer cells is not thorough.Radiotherapy placement is an important part of treatment.The accuracy and retention mechanism of tumor location after placement have a great impact on the effect of radiotherapy.In this paper,the influence of physiological and biomechanical behavior on soft tissue deformation is analyzed,and the deformation law of lung tumor position error is obtained by three-dimensional modeling and finite element simulation.using the Medical robotic arm independently developed by the research group as the compensation carrier.A correlation model of lung tumor positioning error compensation is proposed,and the compensation method and precision maintenance mechanism based on this error are verified,and the average error correction rate was67%.The main contents and results of this paper are as follows:(1)For respiratory exercise,this paper selects an open database of respiratory movement data from the University of Lubeck in Germany,analyzes the data and obtains the respiratory motion curves in vivo and body surface.It is found that due to the existence of respiratory movement,the soft tissue and tumor have a large amount of deformation in the head and foot direction;The correlation model of respiratory movement in vivo and in vitro is established,and the target deformation error can be calculated by body surface deformation.the correlation degree of model fitting increases with the increase of the number of polynomials,and the root mean square error decreases in turn.(2)The complete biological soft tissue model is an important carrier to study the deformation before and after positioning.In this paper,based on the image data of a middle-aged male patient with lung tumor from Cancer Imaging Archive website,firstly,using the relevant knowledge of anatomy and biomechanics,the finite element model of lung tissue including tumor was established by Mimics and 3-Matic software;And its biomechanical parameters were given.The positioning deformation error of lung and tumor was simulated and analyzed in ANSYS,and the deformation law of lung tissue was obtained.(3)The deformation error law of soft tissue and tumor center is obtained by finite element analysis,and the deviation model of tumor center changing with the positioning angle is fitted;on the basis of uniaxial rotation deviation model,the deviation model of tumor center during multi-degree-of-freedom positioning is established;Using the self-developed medical robotic arm as a carrier,a correlation model for compensation of the deformation error of the tumor's secondary positioning was established.(4)Aiming at the specific treatment flow of radiotherapy,the verification method of tumor deformation error in vivo is given,and the compensation experimental platform is built by using the existing equipment in the laboratory.In this paper,a method of feedforward compensation for tumor position accuracy by controlling the attitude of the robotic arm is verified,and the theoretical support for the accuracy maintenance mechanism is found.The results of this study are of positive significance to improve the accuracy and efficiency of secondary positioning in carbon particle radiotherapy and to achieve the expected effect of accurate treatment.At the same time,this study also has a certain reference value for the development and application of medical robots in other medical fields. |
PDF Full Text Request