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Objective To investigate the effect of the correction of the position error of the abdominal tumor by cone beam scanning. Methods Six patients with abdominal tumor were selected with double-blind method, and electronical portal imaing device was used to collect the information of the patient dosimetry during radiotherapy.EDOSE tool was applied to 3D dose reconstruction so as to execute real-time 3D dose verification of the treatment plan. Each patient had 5 sets of data acquired when image guidance existed and another 5 sets when image guidance was absent. The treatment effects with or without image guidance were compared.Results The overall γ passing rate with cone beam CT image guidance gained no advantages over that without image guidance, though the setup error was corrected to some extent. Image guidance contributed nothing to increasing target area coverage while decreasing exposure dose to normal tissue. Conclusion Setup error correction by the image guidance based on bone marker has no significant effect on improving 3D dose verification and dose accuracy during the radiotherapy of the abdominal tumor patient.
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Objective To design a new method to verify the position of multileaf collimator(MLC)leaf using a two-dimensional ion chamber array(2D-array).Methods 2D-array of PTW T10018 Seven29~(TM) was used to calibrate the accuracy of MLC leaf position of Elekta Precise accelerator.The edge function of the leaf position of MLC was measured and used as the reference value.The precision of MLC leaf was then evaluated through comparing the measured and reference values.Results The accuracy of MLC leaf position was found within?0.1 mm.Conclusion This method of verifying the accuracy of multileaf collimator leaf position is easy,simple and reliable