Research on brachytherapy dose distributionverificationusing two-dimensional ionization chamber arra

来源 :2015北京首届国际近距离治疗肿瘤学术大会暨2015北京首届国际放射肿瘤学术论坛 | 被引量 : 0次 | 上传用户:LJC21102309
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  Objective: To investigate the two-dimensional ionization chamber array Matrixxs feasibility of brachytherapy plan verification, seeking to establish a set of feasible brachytherapy dose distribution verification method.Methods: using well-type chamber to verify the source activity of Ir192;using the radioactive source to complete the calibration of GafChromic film model EBT3 through the Valencia skin applicator and SP34 water equivalent solid phantom, gets dose gray curve, find the percentage depth dose (PDD) curves under Valencia skin applicator and use it to help calibrating the Germany IBA companys two-dimensional ionization chamber array Matrixx, get a calibration factor Kuser.Using Freiburg Flap applicator and inserting the needle combine with solid water to build a phantom, after CT scans,complete the catheter reconstruction and dose distribution calibration in the oncentra treatment planning system, using the measurement and analysis software of OmniProlmRT, the planned dose distribution and measurement dose distributions were compared.Results: the Ir192 dose distribution under Valencia skin applicator is of similar to accelerator beam, transverse and longitudinal symmetry is 0.17% and 0.16% respectively, the PDD of maximum dose is at 3mm under the applicator surface, PDD46.5% is at 11.6mm under the applicator surface.The measured dose distribution and TPS calculated dose plane is compared using gamma analysis method (3mm/3%), the ratio of pixels withinγ ≤ 1 is 97.67%, absolute dose measurement and calculation of dose deviation remains in 5%.Conclusion: the use of radiation field with a flattening filter Valencia applicator can be a source of radiation for trimming, trimmed uniform radiation field for dose calculation and measurement, can be directly used for calibration verification tool, to avoid the high dose gradient near the source due to dose error caused by position error, greatly reduced the energy response of the verification tool.Matrixxenvlution as brachytherapy dose distribution verification tool has good repeatability, avoiding the cost loss using film validation, is more rapid, convenient one of brachytherapy dosimetry QA verification tool.
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