术中放疗加速器Mobetron的临床运用测量及质量保证方法

Measurment of the Clinical Use and Method of Quality Assurance for Mobetron Mobile Intra-Operative Radiotherapy Accelerator

目的:测量移动式术中放疗加速器Mobetron,获知它的电子线临床运用特性,并获得质量保证方法。方法:使用测量仪器包括三维水箱、剂量仪、0.6cc Farmer电离室,测量移动式术中放疗加速器Mobetron的临床运用数据。测量项目有各档能量电子线垂直于水模体表面的中心轴百分深度剂量和平行于水模体表面的射野离轴比、相对输出因子、每日质量保证(QA)数据。测量时使限光筒端面与水面相切,标称源皮距为50cm。结果:各档能量电子线最大剂量深度随限光筒倾斜角度增加而变浅,表面剂量随能量升高而增加,并且比常规加速器更高。对10cm直径、0°倾斜角的限光筒四档能量的最大剂量深度依次为6、12、16、20mm;有效治疗深度依次为0.9、1.9、2.7、3.6cm;输出因子随能量、限光筒直径的变化无明显规律;有倾斜角的筒对称性和平坦度都较差;四档能量质量保证每日QA数据输出量依次为2.098、2.196、2.201、2.260Gy,射线质依次为1.390、1.648、1.078、1.181Gy。结论:通过测量了解了Mobetron加速器的临床运用特性,获得了临床使用和每日QA的数据,为临床提供了质量保证的方法。

Objective：Measure the Mobetron mobile intra-operative radiotherapy accelerator in order to find out its clinical characteristics of electron beam and acquire method of quality assurance.Methods：Using measurement instruments including 3Dwater scanning tank,dosimeter,0.6cc Farmer ionization chamber to measure the clinical characteristics data for Mobetron mobile intra-operative radiotherapy accelerator.For every energy electron beam the measurement items were as followings：percentage depth dose perpendicular to the surface of the water phantom and beam profiles parallel to water phantom surface,relative output factors,daily QA data.During measurement the applicator end was placed to be tangent with water surface meanwhile the nominal source distance to water surface was 50 cm.Results：Every energy electron beam the maximum dose depth became shallow with applicator tilt angel increased,the skin dose became large when energy rised,as well as the skin dose for Mobetron was more higher than the regular accelerator.For a 10 cm 0°applicator the Dmax depth in water were 6,12,16 and 20mm for the 4energies,respectively.The valid treatment depth were 0.9,1.9,2.7and 3.6cm,respectively.Output factor along with the change of energy,the diameter of applicator had no obvious rule.For the beveled applicator the symmetry and flatness was all worse.For four energy of daily QA data the output were in turn 2.098,2.196,2.201,2.260 Gy,and the beam quality were 1.390,1.648,1.078,1.181 Gy.Conclusion：Through measuring of machine the clinical characteristics of Mobetron are understood,the data of clinical use and daily QA are acquired,and the quality assurance method for clinical use is also provided.