电子射野影像装置的剂量学特性及其在容积调强弧形治疗中作为质量保证工具的应用研究。
A study on dosimetric properties of electronic portal imaging device and its use as a quality assurance tool in Volumetric Modulated Arc Therapy.
作者信息
Sukumar Prabakar, Padmanaban Sriram, Jeevanandam Prakash, Syam Kumar S A, Nagarajan Vivekanandan
机构信息
Medical Physics Department, Cancer Institute (WIA), India.
出版信息
Rep Pract Oncol Radiother. 2011 Aug 26;16(6):248-55. doi: 10.1016/j.rpor.2011.08.001. eCollection 2011.
AIM
In this study, the dosimetric properties of the electronic portal imaging device were examined and the quality assurance testing of Volumetric Modulated Arc Therapy was performed.
BACKGROUND
RapidArc involves the variable dose rate, leaf speed and the gantry rotation. The imager was studied for the effects like dose, dose rate, field size, leaf speed and sag during gantry rotation.
MATERIALS AND METHODS
A Varian RapidArc machine equipped with 120 multileaf collimator and amorphous silicon detector was used for the study. The characteristics that are variable in RapidArc treatment were studied for the portal imager. The accuracy of a dynamic multileaf collimator position at different gantry angles and during gantry rotation was examined using the picket fence test. The control of the dose rate and gantry speed was verified using a test field irradiating seven strips of the same dose with different dose rate and gantry speeds. The control over leaf speed during arc was verified by irradiating four strips of different leaf speeds with the same dose in each strip. To verify the results, the RapidArc test procedure was compared with the X-Omat film and verified for a period of 6 weeks using EPID.
RESULTS
The effect of gantry rotation on leaf accuracy was minimal. The dose in segments showed good agreement with mean deviation of 0.8% for dose rate control and 1.09% for leaf speed control over different gantry speeds.
CONCLUSION
The results provided a precise control of gantry speed, dose rate and leaf speeds during RapidArc delivery and were consistent over 6 weeks.
目的
在本研究中，对电子射野影像装置的剂量学特性进行了检测，并对容积调强弧形治疗进行了质量保证测试。
背景
快速弧形放疗涉及可变剂量率、叶片速度和机架旋转。对该成像器进行了剂量、剂量率、射野大小、叶片速度和机架旋转期间下垂等方面影响的研究。
材料与方法
使用一台配备120叶多叶准直器和非晶硅探测器的瓦里安快速弧形放疗机进行研究。针对快速弧形放疗中可变的特性对射野成像器进行了研究。使用栅栏测试检查了动态多叶准直器在不同机架角度和机架旋转期间位置的准确性。通过用不同剂量率和机架速度照射七条相同剂量的测试射野，验证了剂量率和机架速度的控制。通过在每条射野中用相同剂量照射四条不同叶片速度的射野，验证了弧形照射期间叶片速度的控制。为验证结果，将快速弧形放疗测试程序与X-Omat胶片进行了比较，并使用电子射野影像装置进行了为期6周的验证。
结果
机架旋转对叶片准确性的影响极小。在不同机架速度下，各段剂量与剂量率控制的平均偏差0.8%以及叶片速度控制的平均偏差1.09%显示出良好的一致性。
结论
结果表明在快速弧形放疗过程中对机架速度、剂量率和叶片速度实现了精确控制，并且在6周内保持一致。
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