| There are three main methods of cancer treatment nowadays including surgery,chemotherapy and radiation.Radiotherapy was accepted by 70% of cancer patients.The goal of radiotherapy is to deposit energy in the interior of the tumor with no deposition of energy outside the tumor.However,the scattering of radiation decides that the goal cannot be achieved.In fact,radiotherapy requires high dose focused in the target area and low dose outside to protect the normal tissue.Based on the actual situation,we propose the concept of precise radiotherapy which contains precise positioning,precise planning,and accurate beam.With the development of radiotherapy,precise radiotherapy changes from the conformal radiotherapy to intensity modulated radiotherapy and then to the volume of rotation intensity modulated radiotherapy.Due to the different radio-sensitivity of different locations of the tumor,studies found that the sensitivity of the tumor will increase with the same total dose after the high-dose irradiation treatment.Meanwhile,reasonable high-dose irradiation can also stimulate the anti-tumor immune mechanism.Thus,stereotaxic radiotherapy with precise positioning,single high-dose irradiation on the target area is introduced to protect the normal tissue and sensitive organs.The paper introduces the concept of adaptive stereotactic radiotherapy using the linear accelerator which has been widely accepted in hospitals.By optimizing the software and hardware of the accelerator,the stereotactic radiotherapy can be precisely implemented.In this paper,we focus on the radiotherapy localization,dose calculation,plan optimization and beam emission.First of all,we survey the radiographic image guidance method and find they have the defect of non-negligible imaging time,no real-time monitoring,image blurring and extra dose introducing.Based on this,we design the binocular positioning system which uses sub-pixel-level edge extraction and direct linear transformation calibration with the non-uniform lattice correction algorithm.We realize the 3D positioning function with 1mm precision.Also,we use multiple characteristic balls and CT images on the membrane to comply real-time treatment center positioning function.Finally,we use support vector machine to get the validity of the fixed positioning results,which provided the doctors with the means to eliminate the treatment center deviation caused by the breathing.Secondly,we summarize the commonly used dose calculation model and method,introducing the pencil nucleus convolution calculation method.The accelerometer measurements were used as the pencil beam nucleus to correct the inhomogeneity of the tissue and the contour no uniformity by deriving the pencil beam convolution algorithm pencil beam stack.This paper summarizes the commonly used intensity modulation techniques,based on the target area of convex and concave proposed an optimization algorithm based on target segmentation.Through the curvature traversing of the contour of the target area,we find the concave area which needs to be divided,and the original target area is divided into several target areas.Finally the intensity of flux field is obtained.At last,we divided the stereotactic radiosurgery into static intensity modulation,dynamic intensity modulation and rotation intensity modulation.We segmented the field intensity flux map or generated leaf trajectory.After introducing the basic sub-field segmentation algorithm,this paper optimizes and realizes the optimal algorithm of sub-field number.For dynamic intensity modulation,this paper realizes the shortest irradiation time trajectory generation algorithm after introducing the basic blade trajectory algorithm.For the rotation intensity modulation,this paper implements the arc-divided sub-segmentation algorithm.This paper researches and implements the adaptive stereotactic radiotherapy system to ensure accurate positioning,accurate planning,accurate beam,and accurate radiotherapy based on the basis of linear accelerator radiotherapy. |
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