The Key Technical Analysis For Proton Therapy Gantry

Proton therapy is the technology frontier in the field of medical physics which has unparalleled advantages over other radiation therapies.Foreign scientists have been working on this for decades and there's been a lot of progress.However,our country started quite late,only began to focus on this twenty years ago and still stay at an exploration stage.Chinese scientists and engineers are redoubling efforts to catch up with Western countries and preparing to design and manufacture proton therapy facilities of our own.Gantry is one of the most important parts in the whole system which has the following characteristics: large dimension,heavy weight,long span,also it requires high positional accuracy and reliability.First of all,a brief introduction of gantries designed by world famous facility providers is made.Nowadays,gantries mainly fall into two categories: ‘truss style' and ‘barrel style',also,the layout of transmission line and bending magnets makes differences.In consideration of difficulties in design and manufacturing,this paper proposes a solution which divides the body of rotating barrel into three parts and each part can be connected to others by welding.The driving mode of the gantry and the installation way of transmission line as well as the counter weight are determined.The contact stress of rollers is checked based on Hertz contact theory.Some theoretical analysis and motion simulation are made to calculate the driving moment so as to select the suitable electric motor and reduction gearbox.According to the chosen material and size of gears,this paper checked the contact stress and bending stress to make it safe in the entire operational life.The bearing type and layout are determined and after that,calculation of service life is done.Based on Ansys Workbench,the contact stress of rollers and gears are recalculated using FEM simulation method and the results are compared with the theoretical analysis to verify accuracy.The FEM analysis of gantry is made using Solidworks Simulation to analyze the deformation so as to make necessary structure optimizations.Size optimization is done to determine the dimension and layout of stiffened plates to make the deformation least within the limit of weight.Finally,total errors are analyzed to confirm this design solution meet the precision requirement.