自制术中放疗限光筒装置的物理学特点

A studies on the charicteristics of applicators for IORT made in our hospital

目的：分析自制术中放疗限光筒剂量特点。材料与方法：不规则电子线限光筒是用5 mm 厚有机玻璃制作而成。剂量仪使用法码2570型,电离室用NE2571, 0．6 CC。水模中测量射野因子，三维扫描仪在水模中实测射束中心轴百分深度量、OAR、均匀性等，水模为50 cm×50 cm×50 cm。结果：当高于12 MeV电子束时,表面剂量均超过90％，筒径从11～6 cm时表面剂量呈下降趋势,小于6 cm 时有升高迹象，导致剂量的建成区缩短,D max和d 85(15 MeV除外)均向表面移；输出因子在限光筒口径大于5 cm时,趋于稳定，6 MeV时,输出因子随筒径不同而变化较大。结论：我院自制的限光筒优点在于成本低和操作方便，故适合基层医院应用。

： Purpose： To analize the characteristics of IORT used applicators made in this hospital．Material and Method：irregular－shaped electron beam applicators were made with organicglass．The dosimeter used is farmer 2570 of type,0．6cc ionisation chamber was used to carry out the measurement of field factors in water phanton．The PDD ,OAR and homogeneity was calibrated with 3D scanner in water phanton ．The sizes of warter phanton are 50 cm×50 cm×50 cm． Results： The surface doses of target calibrated is in excess of 90％ as energies of electron is more than 12 MeV were used．The surface doses decrese gradully when the size of applicator decrease from 11 to 6 cm and with smaller applicator＇s diameter and higher energy, the depth of maximum dose gets closer to surface． The output factors become stable while the size of applicators get larger than 5 cm． Using 6 MeV of energy electron, the output factors will have bigger changer while using different size of applicators． Conclusion： These applicators made in this hospital are cost －effective and easy to operate． They are specially fit to be used in basic hospital．