真空定位袋在放疗临床应用中的剂量学研究

目的探讨真空定位袋在放疗中的质量保证与质量控制。方法把真空定位袋抽成真空,并使其厚度分别为1cm,3cm,5cm,10cm不等,将其置放于加速器治疗床的固体水模上,固体水模内放置剂量测量仪探头,分别用6MV和15MV高能X线进行照射,得到一组剂量仪读数,然后拿掉真空定位袋,其它条件不变,再去照射。用两组数据进行比较可求出真空定位袋的穿透因子。结果对于不同型号,不同厚度的真空定位袋,穿透因子不同。结论相同能量X线照射下,穿透因子随着真空定位袋厚度的增加而减小;相同型号和厚度的真空定位袋,穿透因子随着X射线能量的增加而增加,因此有必要对真空定位袋进行质量保证和质量控制,确保放射治疗定位和剂量计算的精度。

Study of Vacuum Bag for Radiotherapy Dosimetry in Clinical Application

Objective:To explore the methods of quality assurance(QA)and quality control(QC) for vacuum bag.Methods:The air in vacuum bag was exhausted by air pump and made the bag with the thickness as 1 cm,3 cm,5 cm,10 cm,then put it on the solid water phantom in which there was a chamber dosimeter,and which was on the accelerator therapy table.Irradiated with 6 MV and 15 MV X-ray,got a group of dosimeter data,then took off the vacuum bag and irradiated with the same parameter.Comparing the two groups of dosimeter data and calculated the penetrated factor of the vacuum bag.Result:The penetrated factors of vacuum bag were different when the thickness of the bag and the model number changed.Conclusion:The penetrated factors of vacuum bag reduced when the thickness of the bag increased,and irradiating X-ray of the same energy.To the same model number and thickness of the vacuum bag,the penetrated factors increased when the X-ray energy increased.It's important to test the vacuum bag to ensure the accuracy of radiotherapy.