【作者】 冯威；

【导师】 陈大伟；

【作者基本信息】 吉林大学 ， 公共卫生（专业学位）， 2019， 硕士

【摘要】 目的本研究通过利用二维剂量扫描水箱、电离室和剂量探测器等测量移动式低能X射线术中放疗机(INTRABEAM治疗系统,德国蔡司公司)在常规术中放疗条件下,水中、空气中和空腔结构的吸收剂量。并利用热释光剂量计和胶片剂量计测得的空气中不同平面的吸收剂量、剂量重复性以及剂量相对偏差进行比较,得出相应的剂量分布结果,为实际术中放疗过程中的医务人员和患者,在减少自身辐射剂量方面提供一些参考意见。通过对移动式低能X射线术中放疗机质量保证指标的检测,得出相应数据,为低能X射线术中放疗机能够准确治疗提供数据基础,同时也为低能X射线术中放疗机制定相关检测标准提供数据支持。方法采用二维剂量扫描水箱、电离室、热释光剂量计和胶片剂量计等测量仪器,对移动式低能X射线术中放疗机不同型号球形施源器深度剂量率、吸收剂量、重复性,不同平面吸收剂量以及剂量相对偏差等进行测量,同时测量移动式低能X射线术中放疗机质量保证相关指标,与厂家参数要求进行比较。应用SPSS24.0、Excel 2013、Graph Pad Prism 5.0对实验所得数据进行统计学分析和作图。结果(1)该移动式低能X射线术中放疗机SQA中的PDA和PAICH等检测指标结果均符合厂家要求数值。(2)水中测量结果:在常规术中放疗条件下给予20Gy照射,距球形施源器表面相同位置处,直径1.5cm施源器剂量率最大,0mm处剂量率为3.13Gy/min,2mm处吸收剂量为12.81Gy(64.5%);直径5.0cm施源器最小,0mm处剂量率为0.43Gy/min,2mm处吸收剂量为15.66Gy(78.3%),5mm处为11.25Gy(56.3%);直径5.0cm施源器总体重复性均小于1.00%,各向同性相对偏差范围为-0.89%~1.19%。(3)空气中测量结果:采用5.0cm球形施源器,常规术中放疗条件下给予20Gy照射,在距施源器表面距离与剂量结果中,距施源器表面5mm处最大平均吸收剂量为12.08Gy(60.4%);距施源器表面300mm处吸收剂量降至0.10Gy以下。不同平面距施源器表面距离与重复性结果中,热释光剂量计测得Z轴与X轴平面重复性波动最小,范围在0.13%~0.64%。胶片剂量计测得X轴与Y轴平面重复性波动最大,范围在0.38%~2.12%。不同平面剂量相对偏差与角度关系结果中,在X轴与Y轴平面上,距离施源器表面5mm时,各角度剂量相对偏差波动范围-0.083%~0.167%;在Z轴与X轴平面上,距离施源器表面25mm时,各角度剂量相对偏差范围在-1.278%~0.639%。在Z轴与Y轴平面上,角度为90°时,剂量相对偏差最大值为-1.935%。(4)空腔下吸收剂量实验结果:3mm、4mm和5mm空腔下深度5mm水层平均吸收剂量分别为6.356Gy(31.78%)、4.123Gy(20.62%)和3.779Gy(18.90%)。结论(1)直径5.0cm球形施源器水中剂量率、吸收剂量、重复性和各向同性相对偏差优于其他型号施源器;(2)三个平面(X-Y平面,Z-X平面,Z-Y平面)内,距离施源器表面相同距离处的吸收剂量没有明显差异;(3)三个平面(X-Y平面,Z-X平面,Z-Y平面)内,各角度剂量相对偏差均满足厂家治疗参数(±2%)要求;(4)空腔下吸收剂量结果可为临床医生制定治疗计划提供剂量参考;(5)移动式低能X射线术中放疗机SQA中PDA和PAICH等检测指标结果均符合厂家要求数值。更多还原

【Abstract】 ObjectiveIn this study,two-dimensional dose scanning water tank,ionization chamber and dose detector were used to measure the absorbed dose of mobile low-energy X-ray intraoperative radiotherapy machine(INTRABEAM treatment system,Zeiss Company,Germany)in water,air and cavity structure under the condition of conventional intraoperative radiotherapy.By comparing the absorbed dose,dose repeatability and relative deviation of dose measured by thermoluminescence dosimeter and film dosimeter at different levels in the air,the corresponding dose distribution results are obtained,which can provide some references for medical staff and patients in reducing their own radiation dose during actual intraoperative radiotherapy.Through the detection of quality assurance index of mobile low-energy X-ray intraoperative radiotherapy machine,the corresponding data are obtained,which can provide data basis for accurate treatment of low-energy X-ray intraoperative radiotherapy machine,and also provide data support for establishing relevant detection standards of low-energy X-ray intraoperative radiotherapy machine.MethodUsing two-dimensional dose scanning water tank,ionization chamber,thermoluminescence dosimeter and film dosimeter,the depth dose rate,absorbed dose,repeatability,absorbed dose in different planes and relative deviation of dose for different types of spherical emitters of mobile low-energy X-ray intraoperative radiotherapy machine were measured,and the related quality assurance indexes of mobile low-energy X-ray intraoperative radiotherapy machine were also measured.Comparing with the requirement of manufacturer’s parameters.SPSS24.0,Excel 2013 and Graph Pad Prism 5.0 were used to analyze and map the experimental data.Results:(1)The results of PDA and PAICH in SQA of the mobile low-energy X-ray intraoperative radiotherapy machine meet the requirements of manufacturers.(2)Measurement results in water: Under the condition of routine intraoperative radiotherapy(20Gy),the dosage rate of the spherical emitter with diameter of 1.5 cm was the highest,the dosage rate at 0 mm was 3.13 Gy/min,and the absorbed dose at 2 mm was 12.81 Gy(64.5%);the diameter of the 5.0 cm emitter was the smallest,the dose rate at 0 mm was 0.43 Gy/min,the absorbed dose at 2 mm was 15.66 Gy(78.3%)and at 5 mm was 11.25 Gy(56.The overall repeatability of the 5.0 cm diameter donor is less than 1.00%,and the isotropic relative deviation ranges from-0.89% to 1.19%.(3)Measurement results in air: Under routine intraoperative radiotherapy(20Gy),the spherical 5.0 cm donor was used to irradiate.Among the results of distance and dose from the surface of the emitter,the maximum absorbed dose is 12.08 Gy(60.4%)at 5 mm from the surface of the emitter,and the absorbed dose is less than 0.10 Gy at 300 mm from the surface of the emitter.Among the results of the reproducibility and distance between different planes and the surface of the donor,the reproducibility of Z-axis and X-axis measured by thermoluminescence dosimeter was the smallest,ranging from 0.13% to 0.64%.The X-axis and Y-axis plane reproducibility fluctuated the most,ranging from 0.38% to 2.12%.Among the results of the relationship between relative deviation of dose and angle in different plane,the fluctuation range of relative deviation of dose in different angle is-0.083%-0.167% when 5 m away from the surface of the source on the X-axis and Y-axis plane,and-1.278%-0.639% when 25 mm away from the surface of the source on the Z-axis and X-axis plane.On the plane of Z axis and Y axis,when the angle is 90 degrees,the maximum relative deviation of dose is-1.935%.(4)The experimental results of the absorbed dose under the cavity: the average absorbed dose of the water layer with the depth of 5 mm under the cavity of 3 mm,4 mm and 5 mm is 6.356 Gy(31.78%),4.123 Gy(20.62%)and 3.779 Gy(18.90%)respectively.Conclusions:(1)The relative deviation of dose rate,absorbed dose,repeatability and isotropy in the direction of beam axis of spherical emitter with diameter of 5.0 cm is better than that of other types of emitter.(2)In three planes(X-Y plane,Z-X plane,Z-Y plane),there is no significant difference in the absorbed dose at the same distance from the donor surface.(3)The relative deviations of doses in three planes(X-Y plane,Z-X plane and Z-Y plane)meet the requirements of manufacturers for treatment parameters(+2%).(4)The subcavity absorbed dose in this experiment can provide dose reference for clinicians to make treatment plans.(5)The PDA and PAICH in SQA of the mobile low-energy X-ray intraoperative radiotherapy machine meet the requirements of manufacturers.更多还原