| WHO reported that cancer is one of the most serious diseases and an important reason of human death. At present the number of cancerous person is increasing.Radiotherapy has always been a main treatment method. As the development of radiotherapy technology, particularly the wide use of 3D-CRT, IMRT and IGRT, the age of precision radiotherapy is coming. The theraputic effect of radiotherapy is not only determined by lethal dose but also determined by accurate implement of radiotherapy treatment. Designing and implementation of radiotherapy is very complicated and involved by equipments and people. Each step might be a source for radiotherapy,for example plan error, position error, instrumental error and so on. Little error might lead insufficient tumor lethal dose or excessive normal tissue dose. Tumor control rate will be lower and normal tissue complication probability rise, research shows that radiotherapy accuracy increase 1% will lead to 2% increase of cancer cure rate. Treatment precision is the accuracy of treatment implement compare with treatment plan design. So the radiotherapy precision is very important for radiotherapy QA. The radiotherapy precision determines technology of precision radiotherapy. we must do effect dosimetric verification for patients.Three-dimensional conformal radiation therapy and Intensity modulation radiation therapy are widely used as an conventional method. there are two dosimetric verification methods:absolute dose verification and relative dose verification. absolute dose verification:compare and evaluate the deviation of a certain point dose calculated by TPS and measured by ionization chamber. Absolute dose verification usually use ionization chamber. Relative dose verification include analysis of dose map and isodose curves. Relative dose verification tools are film, thermoluminescent dosimeter, electronic portal imaging device and MatriⅩⅩ.In this paper, dose verification of accelerator is detailed summarized. Measure the accelerator with ionization chamber and film respectively and analyze the results. Making an solid phantom to make easier for daily measurement. We can measure the dose at different depth by changing arrange of this phantom,as it is easily used and less complicated to operate and has a good repeatability. The main work finished is as follows:1. Measuring and analysis the result of radiation field measured by film. Measuring four radiation field 5cm×5cm,8cm×8cm,10cm×10cm,12cm×12cm. The film is developed and scanned into a computer. Analyze the film and get the data results.2. Measuring and analysis the result of radiation field measured by MatriⅩⅩ. Measuring four radiation field 5cm×5cm,8cm×8cm,10cm×10cm,12cm×12cm under same measurement condition of film. Measurement data of MatriⅩⅩis analysis by software of its own in isodose curves and boundaries. Analyze the film and compare the results of MatriⅩⅩdata processed by bilinear interpolation and cubic spline interpolation.To analyse which interpolation method is better for MatriⅩⅩdata processing.3. Design and product a ABS resnic solid phantom. The solid phantom includes a frame,a phantom layer for ionization chamber,some ordinary solid layers and a film case cassette.4. Use dosimeter to measure absorbed dose of high energy X-ray and electron beam for medical linear accelerator from standard water phantom and home-made solid phantom. To analysis the measurement result. the correction factor of absorbed dose measured by home-made solid phantom to water is f.ABS resinic home-made solid phantom can be used for absorbed dose measurement and dose verification, if we use f to correct the measurement result. |
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