Research On Magnetic Positioning Technique For Intraoperative Tumor Tracking

In today’s world,lung cancer accounts for the vast majority of human cancer deaths due to the growing number of smokers and environmental pollution,and radiation therapy(radiotherapy)is an important method to treat lung tumors.The goal of radiation therapy is to avoid normal organs around tumors in the lungs with the least amount of damage to the patient,thereby maximizing tumor cell apoptosis.However,in the process of radiation therapy for lung tumors,the patient’s natural life activities such as breathing and heartbeat can cause dynamic displacement of the lung tumor,making it impossible for radiation therapy rays to continuously irradiate the tumor,thus affecting the radiation therapy effect or causing damage to the normal tissues and organs surrounding the tumor.This requires real-time tracking of tumor movement during radiotherapy procedures to ensure the accuracy of radiotherapy.Traditional tracking methods have problems such as slow tracking speed,radiation to human body or tracking and radiation therapy cannot be performed simultaneously,so real-time and high-precision tracking of lung tumors during radiation therapy remains a great challenge.The purpose of this study is to explore the feasibility of using two or three simultaneously moving permanent magnets for tumor tracking in radiation therapy procedures.The position and posture of the permanent magnet are used to calculate and obtain the real-time position and posture of the lung tumor,and then adjust the acceleration posture of the radiotherapy equipment,which provides the precondition for the linear accelerator movement based on the radiotherapy robot,and can realize the precise radiotherapy of lung cancer.In this study,magnetic sensor arrays can be used instead of expensive and harmful CT or X-rays to track tumor movement based on permanent magnets.The permanent magnets do not require a power supply and are wirelessly connected for greater safety.In addition,using the permanent magnets as a localization source,they can be attached with a puncture knife and removed outside the body at the end of radiation treatment,which can eliminate late hidden problems.In this dissertation,we first apply a multi-target localization method when the tumor is large and a single-target localization method when the tumor is small,to obtain the simulation transition range between them by simulation experimental design.And because the distance between multiple permanent magnets is small,a multi-magnetic dipole model is used to simulate the magnetic field distribution.Then,a magnetic positioning system for tumor localization was built to perform the technology verification experiments,which showed that the tracking accuracy of the tumor center during radiotherapy was 1.38±0.83 mm based on the single and triple magnetic dipole tracking algorithms,and the tumor diameter tracking accuracy was 1.51±1.30 mm based on the triple magnetic dipole tracking algorithm.The tumor diameter tracking accuracy based on the triple magnetic dipole tracking algorithm was 2.15±0.78 mm.Therefore,this permanent magnet-based tumor tracking technique can effectively improve the performance of robotic radiation therapy tracking.In this dissertation,we present a tumor tracking and localization technique using multiple permanent magnets,to provide real-time feedback of tumor position attitude for controlling robotic arm movement during lung cancer radiation therapy.The positional attitude tracking technique based on multiple permanent magnets offers a novel potential for intra-operative localization in lung cancer radiation therapy.Moreover,this technology can also be applied to stereotactic radiosurgery for prostate,breast,or liver cancers.