The Research On The Application Of Cone Beam CT In Precise Radiotherapy

Objective:To analyze the setup errors of head-neck,body or pelvic tumor in precise radiotherapy by on board imager of Varian linac,with 2D lateral film mode and three-dimensional cone beam CT pattern analysis when setup error,verify the positioning accuracy in different parts of the human body contrast these two kinds of models,to explore the different parts of the body,which mode to choose the greatest benefit of different parts of guidance in the clinical work of selection.Methods:Using Varian Clinac i X medical accelerator airborne image verification system,we compared 60 cases of accurate radiotherapy in our department,including 20 cases of head and neck,body and pelvis.All the patients were treated with thermal plastic body(face,neck shoulder)die is fixed,CT simulation,post metal marker,scanning the image to plan system,target delineation by doctors,physicists for individual plan design,each program contains OBI positive lateral radiograph positioning and CBCT positioning the wild wild.Before the first treatment to reset the center point,DR radiograph and CBCT images were collected,2D/2D match and 3Dmatch CT images and DRR images respectively and positioning planning system generated by the automatic matching,analysis and comparison of two groups of patients about the set-up errors to the displacement of X as head foot direction down for Y,front and rear direction denoted as Z,were recorded in three-dimensional direction linear displacement.Results:Average bit error with the error overall mean value recorded as described the system error,describe all graded setup errors of the standard deviation of the error with the overall standard deviation is the random error.The data is represented by system error± random error.the X axis is left and right,Y axis is head and foot and Z axis is before and after.Before the first treatment OBI model to validate the two-dimensional film of head and neck cancer positioning error is X:0.14 + 0.06 cm,Y:0.27 + 0.09 cm,Z:0.16 +0.05 cm,bit error body pendulum is X:0.31 + 0.09 cm,Y:0.59 + 0.19 cm,Z:0.27 + 0.08 cm,X:0.31 + 0.09 cm pelvic position error,Y:0.53 + 0.15 cm,Z: + 0.26 0.09cm;verification the 3D CBCT model the position errors of head and neck X:0.13 + 0.05 cm,Y:0.25 +0.09 cm,Z:0.15 + 0.06 cm,bit error body pendulum is X:0.240 + 0.05 cm,Y:0.44 + 0.16 cm,Z:0.21 + 0.06 cm,X:0.20 + pelvic patient positioning error 0.07 cm,Y:0.38 + 0.12 cm,Z:0.18 + 0.08cm;all data are used Microsoft Excel.And do a simple graphic analysis,using SPSS21.0 statistical software for statistical analysis,the two patterns of quantitative data independent t test in X,Y,Z axis,head and neck in three directions The difference was not statistically significant(p>0.05),and the difference between the body and pelvic patients in three directions was statistically significant(p<0.05).Conclusion:We can see the two kinds of model verification of position verification in the head and neck when the difference was not statistically significant,can meet the precise radiotherapy of position verification requirements,with the same trend,the maximum error occurred in the head foot direction of Y axis,a system which may cause error and CT scanning;and in the body of the pelvic cavity with two kinds of model validation were statistically significant difference,indicate that in the human body by respiratory movement,intestinal peristalsis and bladder size of parts CBCT to verify the great advantages Obviously,can change the displacement of real-time verification of the tumor target size and shape and surrounding organs,prevent leakage or normal tissue as the target area to accept the excess radiation,more significance in clinical practice.