| Radiotherapy, surgery and chemotherapy are three main techniques of tumor treatment. It is estimated that about 60%-70% of cancer patients require radiotherapy. Intensity Modulated Radiotherapy (IMRT) is a three-dimensional conformal radiotherapy (3D CRT) based on the recent development of the more advanced physical basis of radiotherapy, which enable high-dose in the three-dimensional shape of the tumor shape with the same direction, and it can adjust output of dosage in every point according to the manner required within the scope of the radiotherapy field, optimizing the allocation of beam weights, which can greatly increase the tumor dose and reduce the volume of normal tissue by greatly improve tumor control and reduce the incidence of normal tissue complications. This is of important significance in radiobiology, radiotherapy has become the mainstream of the 21st century.However, as a new precise radiotherapy techniques, the actual complexity of the issue, the advantage of IMRT is far from being played out, in terms of hardware and software are still many issues that need to be addressed and improved. Therefore, research and development for new IMRT system in the majority of hospitals at home and abroad has become a hot topic. This paper summarizes the status of IMRT. Clinical application of the 1MRT system in two main ways (static and dynamic modulation) the characteristics and shortcomings; Based on a deep understanding of conformal radiotherapy and various optimization algorithm of computer technology, considering the actual conditions of China's material and technical resources and economic level, We already know that the use of target (disease) and the three-dimensional reconstruction of around vital organs and technology of repeatable precise positioning, developed suited to China's national conditions, with independent intellectual property, for the majority of small and medium-sized hospitals and application better functional 3D static intensity modulated radiotherapy system, which was done mainly as follows:1. Study on precise positioning technology of Static Intensity Modulated RadiotherapyAs we all know, the question of the precise location of tumor focus is the premise and key in radiotherapy. It includes information on the use of various accurate imaging method, three-dimensional reconstruction, sketches, calculation of the tumor focus and mechanical positioning system coordinates accurate positioning and other processes. Mechanical positioning device which is the benchmark and bridges throughout the entire course of treatment. We turn first to this body precise positioning technology and equipment, Innovational proposed separate and accurate positioning system ("body accurate positioning system for radiotherapy," utility model patent applications No: 200620054436.5), improve the original JX-200 positioning system in conformal radiotherapy as a whole system, and further improve the positioning accuracy of the system, and successfully resolved the deficiencies and shortcomings of the original positioning system. On this basis we are designing a new head and neck precise positioning system, and achieved good clinical results. CT simulation system in radiotherapy is a method of positioning has grown rapidly in recent years, In this issue we focus on the laser positioning system and mastered the use of laser walking motor and the way of SCM controlling accuracy positioning, to lay the foundation for future expansion in CT simulation function in precise radiotherapy system. Finally keep up with the latest developments in the current hot Intensity Modulated Radiation Therapy. We went on a different plane on the research of the external characteristics of CT/PET image fusion and based on image guided dynamic tracking precise positioning technology. 2. Study on Intensity Modulated Radiotherapy planning system and static optimization technologyIMRT, as a new accurate radiotherapy technology, is so complicated that the advantages of it have not yet been fully utilized until recently. There are many difficult problems, including how to select models of dose calculation and how to select the optimization methods of inverse planning to produce highly accurate dose, need to be dealt with. With the development of IMRT and inverse planning, the automatic selection of suitable beam parameters in external beam radiotherapy has gained wide interests, and is being studied by more and more researchers. There are many beam parameters need to be optimized, including beam energy, beam weights, and beam directions. Linear programming, quadratic programming, gradient programming, constrained simulated annealing and genetic algorithms are the typical optimization methods. In this thesis, the dose calculation model based on pencil beams was constructed, two-dimensional convolution and Fast Fourier Transform (FFT) methods were used to do dose calculation. GA was used to optimize beam weights in IMRT inverse planning, during the evolution of GA, objective function based on dose constrain was used to calculate the fitness of individuals. Dose homogeneous constrain and important factors constrain in different tissues are constructed. Iso-dose curve and dose-volume histogram were used to evaluate the treatment plan. At the end of this work, the treatment planning system of IMRT has been successfully developed with Visual c#.net 2005. Finally, we used Visual c# successfully developed a "GA-IMRT/200 intensity modulated radiotherapy planning system based on genetic algorithm ", it received the national computer software registration (2006SR02586). Research and experimental results show that the genetic algorithm is an effective IMRT beam weight optimization method, can calculate on the higher conformal dose distribution in a clinically acceptable time, have broad application prospects in IMRT parameter optimization. 3. Study on implementation and equipment of static IMRTCurrently Scanditronix MM50 roundabout accelerator and multi-leaf collimator (static and dynamic IMRT) are the two main methods in clinic to achieve IMRT. To use cyclotron for the realization of IMRT is obviously inconsistent with the economic strength of our various hospitals. The NOMOS Company's Peacock (MIMIC) system requires so high-precision of the control and treatment bed that domestic current linear accelerator and import old accelerator cannot reach the requirement. And the application of various imports dynamic multi-leaf collimator (step-and-shot, SMLC) will be difficult for prices and the use of small hospitals to accept. There is an urgent need and inevitable trend for the use of IMRT in clinic. However, as the expensive price and hardware limitations it is difficult for the IMRT to enter China's clinical radiation therapy widely and thus tens of thousands of cancer patients cannot get the best treatment. Therefore, research and development for new IMRT system acceptable to the majority of hospitals have become the target and starting point of our study. In this paper, we first launched a research of manual multi-leaf collimator, then designed and developed a manual and semi-automatic multi-leaf collimator. However, they cannot use too cumbersome to meet the clinical application of IMRT. So we devise a new method to achieve static IMRT through using dose distribution of the three-dimensional conformal melting blocks. Under the China's current economic level, we believe that this method has an especially meaning in clinical application. Therefore, we propose innovative "use of 3D blocks biopsy method developed to achieve Intensity Modulated Radiation Therapy" (for its invention: 021520763), and also conduct experiments and research.4. Study on Static Intensity Modulated Radiotherapy System research experiments and test equipment3D water tank scanning system is a equipment that use linear accelerator quantitative measuring the dose distribution by simulating the distribution of rays in the model of the human body, it can measure radiation absorbed dose by automatic scanning. However, the 3D water tank scanning system mainly relied on imports and with expensive price. Currently a simple structured dose measuring water tank with low-cost are used to achieve the main function in major hospitals at home according to practical application needs in clinic, its name is standard water tank or water model. The standard water tank designed a penstock (tap), and buckets placed by controlling the taps, reduce the depth of the water. If the depth of water needs to increase, use a cup scoop a portion of water from buckets to water tank. In actual measurement, this working mode are of low efficiency measurement, large labor-intensive, water controlling inaccurate, insecurity to circuits and machinery. For this reason the project team developed a new type of stereotactic radiosurgery treatment system dose measuring water tank (utility model patent application number: 200620054436.X), it successfully resolved the above shortage of standard water tank, It has smooth automatic control of water pumps, rapid and secure features. Finally, we conducted an experiment in Static Intensity Modulated Radiotherapy system, including the system's accuracy test, experimental verification and evaluation based on combination of two measurements: physical modeling and self-made plexiglass equivalent quadrate physical modeling. The purpose are positioning accuracy and dose verification in Static Intensity Modulated Radiotherapy, the former are integrated test of treatment accuracy in mechanical positioning, planning systems and linear accelerator treatment systems; the latter include absolute and relative dose verification.
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