| The heavy ion medical machine is researched and developed by the Institute of Modern Physics of the Chinese Academy of Sciences is China’s first heavy ion accelerator for tumor treatment.The heavy ion medical machine has broken the market monopoly of the developed countries on the large,sophisticated and cutting-edge medical devices,and it turned from the research stage to the market industrialization.The synchronous ring circumference of domestic heavy ion medical machine is only more than 50 meters,but the height difference of its high-energy transport line is up to nearly 20 meters,so it is the most compact device with the largest height difference span among similar devices.Its installation elements have a complex structure,and the installation space is narrow.At the same time,it requires to carry out a sub-millimeter level installation of all the key components in a short time.As a large-scale medical device,the heavy ion cancer therapy device after industrialization will meet a higher requirement for the efficiency and accuracy of the alignment installation due to the particularity of its use nature as well as the compactedness of its design structure,so the alignment will face a great challenge.Taking the heavy ion medical machine under construction as research basis,this paper improves the installation efficiency of the components and shortens the installation period of the heavy ion medical machine through the innovation of alignment technology.The alignment accuracy of the heavy ion medical machine is improved by studying the factors influencing the alignment accuracy and improving and optimizing the alignment method.At present,the main research achievements and innovations include the following several aspects:1.By means of advanced digital 3D measuring instruments with a high precision,such as laser tracker and measuring arm,based on the study and analysis on the structure design,measurement principle and alignment precision requirements of the magnetic field measuring system,a set of magnetic field measurement positioning alignment methods based on magnet calibration data were proposed.Then the experimental results of the devices which have been established indicated that the alignment accuracy of all components in the magnetic measurement system was better than 0.1 mm,which not only met the requirements for the high-accuracy positioningof the magnetic measurement system,but also improved the efficiency of magnetic positioning.2.Through studying the space design structure of heavy ion therapy device and the relationship between the alignment precision of components in accelerator physics and beam dynamics as well as the factors influencing the precision,and based on the high-precision 3D measurement control network,The measurement error of laser tracker is controlled by many ways.Through the control network adjustment with constraint conditions,the measurement precision of the three-dimensional control network was improved.In the alignment installation of the synchronization loop,the key element of the “one-station full-coverage measurement” alignment synchronization loop was proposed,which made the relative alignment accuracy RMS of all magnets in the synchronization loop reach 0.05 mm,effectively reduced the closed orbit of the synchronization loop,and improved the beam quality of the synchronization loop.In the installation alignment of vertical treatment terminal with a high elevation and large span,a calibration data transformation model of magnetic heteromorphic installation was built to carry out coordinate transformation of heteromorphic installation magnet calibration data on the treatment terminal according to on-site installation angle,which overcame the difficulties brought by different calibration coordinate and installation coordinate when installing vertical terminal components,and effectively improved the work efficiency of alignment installation.3.In the installation and alignment of beam diagnostic elements of heavy ion therapy device,an alignment method for accurate alignment and on-line installation of beam diagnostic elements in vacuum pump room was studied.The alignment of the beam diagnostic elements installed in the vacuum pump room was adjusted through the optical alignment telescope.Then the joint measuring arm was used to measure the external benchmark targets in the vacuum pump room,successfully convert the center of the beam diagnostic elements in the vacuum pump room into the external calibration of the vacuum pump room,which overcame the problem that internally installed components of traditional vacuum pipe cannot carry out a high-precision digital alignment.Therefore,during the installation process,by means of three-dimensional control network and laser tracker,the center target position of the beam diagnostic components was accurately localized in the designed theoretical position.Based on the coordinated measurement of optical instrument andhigh-precision digital instrument,the accurate calibration and precise installation of beam diagnostic elements in the vacuum pump room were achieved,which effectively improved the beam measurement accuracy of beam diagnostic elements to the accelerator.4.It was suggested to apply the close-range digital photogrammetric equipment to the patients’ position verification before heavy ion treatment and real-time position monitoring during the treatment.Then through establishing a mutual transformation model of laser tracker three-dimensional control network and digital photography measurement equipment,a systemic algorithm transforming data processing was provided,and then a complete set of online measuring system for patient treatment was formed.Digital photogrammetric equipment is used to quickly calibrate the tumor treatment position relative to the beam center,and digital photogrammetric calibration equipment is adopted to monitor and calibrate data to guide the position and verify patients’ positioning,so as to improve patients’ position reliability and shorten position time,and further enhance the position efficiency in the treatment of patients.During the treatment process,photogrammetry equipment can be used to establish an out-of-tolerance warning mechanism through monitoring the measurement targets pasted in the patients’ external body,which can guarantee the accuracy of the patients’ irradiation position during the treatment and avoid normal tissues from being illuminated,thus improving the treatment effect of the patients.Based on the research on the above alignment key technology,the technical problems in the alignment installation of heavy ion medical machine were solved.The above research contents were mostly applied in the equipment of Wuwei Heavy Ion Treatment Center and Lanzhou Heavy Ion Hospital.Through the actual engineering verification,the above alignment technology has effectively improved the alignment installation efficiency of the heavy ion medical machine and shortened the installation period,and various installation errors of key components are better than the requirements for physical precision.The treatment device of Wuwei Heavy Ion Treatment Center has completed the patients’ clinical trial and has been put into use,and the device of Lanzhou Heavy Ion Hospital has also begun commissioning.All beam parameters are better than the design target,which is also the best verification of the key alignment technology of the heavy ion medical machine. |
PDF Full Text Request