| Radiation therapy is currently the most popular and effective treatment of cancer,because IMRT has a steep dose drop gradient,precise dose regulation,better endanger organ protection,so widely used in head and neck cancer radiotherapy.Clinically,the treatment cycle of cancer patients is generally 6-7 weeks,during which the changes in weight of cancer patients,as well as changes in tumor volume and other factors are likely to lead to endangering the anatomical structure of the organ changes and the target area.If you continue to using the original plan to do radiation therapy,it will reduce the target dose,rise the organ dose,and thus promote the normal tissue damage by ray,greatly reducing the quality of life of patients.Based on the above,the current clinical measures taken in each patient before radiotherapy are that CT or CBCT are scanned to guide the placement and the plan is modified in 3-4 weeks of treatment cycle.However,simply modifying a plan can not be a good way to make up for the defects of reducing the accuracy of treatment result from changing of the anatomical structure of the cancer patient target and the organ.Therefore,aiming at the difficult problems in clinical practice,this paper designs four adaptive IMRT adjustment strategies,and uses the gradient-based deformation registration method to propose the strategy to solve the above problems.The main contents are summarized as the following two aspects:(1)Research on Gradient-based Deformation Registration MethodIn this paper,a gradient registration method based on gradient is proposed for the problem that the density of CBCT image is low and the density of CBCT image and CT image is inconsistent.In this part,the imaging principle and imaging characteristics of CT and CBCT are discussed.Based on the characteristics of the above two images,the spatial deformation model is constructed,and the method of deformation registration is designed.The method is experimentally based on clinical data.In order to further prove the validity and feasibility of the deformation registration method,this paper uses the patient data to carry out the experimental study,and the gradient-based registration algorithm and the gold standard Demons deformation registration in the registration field The algorithm is compared and analyzed.(2)A comparative study on adaptive IMRT adjustment strategies for four kinds of head and neck cancerIn this paper,28 patients with head and neck cancer were selected for experimental study.All patients underwent conventional treatment of segmentation.In the radiotherapy cycle,the CBCT images(6 weeks)were scanned on the first day of each radiotherapy week as the reference image,the CT images were planned as the target images,and the images after the deformation registration were defined as pseudo CT image.Second,the design of four different frequency adjustment programs,no planned adjustment as a reference program,the actual dose of each program and the planned adjustment of the dose,in the resulting 6 sets of pseudo CT images to recalculate the dose,and the use of density And the cumulative dose of each planned adjustment scheme and the planned adjustment dose were calculated.Finally,the tumor target was evaluated quantitatively in the course of radiotherapy,and the changes of organ volume and dose were analyzed.The changes of the two groups were analyzed statistically and the correlation between them was analyzed.It is concluded that the planned dose is sufficient to ensure that the target dose is controlled within the safe range,and the higher the frequency of the program,the closer the actual dose is to the planned dose,and the second is the highest efficiency. |
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