EPID-based verification of the MLC performance for dynamic IMRT and VMAT
EPID-based verification of the MLC performance for dynamic IMRT and VMAT
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DOI：
10.1118/1.4752207
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发表时间：
2012-10-01
期刊：
影响因子：
3.8
通讯作者：
Greer, Peter B.
中科院分区：
文献类型：
--
作者：
Rowshanfarzad, Pejman;Sabet, Mahsheed;Greer, Peter B.
目的：在强度调制放射治疗（IMRT）和体积调制弧形治疗（VMAT）等先进放射治疗中，多叶准直器（MLC）性能的验证是直线加速器质量保证计划的重要组成部分。本研究的目的是使用现有的测量方法对MLC进行几何质量保证，并将其扩展到更全面的评估技术，并开发专用的鲁棒算法，以快速，准确和有效的方式定量研究MLC的性能。利用集成式电子射野成像仪（EPID），在步进拍摄模式下研究了叶片的行为在固定台架角度和弧形输送的栅栏测试期间采集的图像。MLC还通过分析在各种条件下输送的滑动间隙模式的电影EPID图像在动态模式下进行了研究，这些条件包括不同的叶片速度、在固定机架角度或弧形模式下输送以及改变叶片运动方向。该方法的准确性进行了测试，通过检测故意插入的错误中的delivery patterns.Results：该算法开发的栅栏分析是能够找到每个人的叶片位置，间隙宽度，和叶银行偏斜除了从预期的叶片位置相对于光束中心轴与亚像素精度的偏差。在5个月的时间内，对于三个被测试的直线加速器，差距宽度的最大变化为0.5 mm，与预期的叶片位置的最大偏差为0.1 mm，MLC偏斜度高达0.2度。为滑动间隙分析开发的算法可以确定每个单独叶片的速度和加速度/减速度以及差距宽度。随着叶片速度的增加，叶片性能的准确性略有下降。分析结果通过几个图表呈现。该方法的准确性进行了评估为0.01毫米的差距的大小和峰值位置determination.Conclusions：这项研究提供了快速，简便，准确的测试方法，为常规的MLC性能的QA，并有助于更快地解决MLC的问题，在IMRT和VMAT治疗。(C)2012年美国医学物理学家协会。[http：//dx.doi.org/10.1118/1.4752207]
Purpose: In advanced radiotherapy treatments such as intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT), verification of the performance of the multileaf collimator (MLC) is an essential part of the linac QA program. The purpose of this study is to use the existing measurement methods for geometric QA of the MLCs and extend them to more comprehensive evaluation techniques, and to develop dedicated robust algorithms to quantitatively investigate the MLC performance in a fast, accurate, and efficient manner.Methods: The behavior of leaves was investigated in the step-and-shoot mode by the analysis of integrated electronic portal imaging device (EPID) images acquired during picket fence tests at fixed gantry angles and arc delivery. The MLC was also studied in dynamic mode by the analysis of cine EPID images of a sliding gap pattern delivered in a variety of conditions including different leaf speeds, deliveries at fixed gantry angles or in arc mode, and changing the direction of leaf motion. The accuracy of the method was tested by detection of the intentionally inserted errors in the delivery patterns.Results: The algorithm developed for the picket fence analysis was able to find each individual leaf position, gap width, and leaf bank skewness in addition to the deviations from expected leaf positions with respect to the beam central axis with sub-pixel accuracy. For the three tested linacs over a period of 5 months, the maximum change in the gap width was 0.5 mm, the maximum deviation from the expected leaf positions was 0.1 mm and the MLC skewness was up to 0.2 degrees. The algorithm developed for the sliding gap analysis could determine the velocity and acceleration/deceleration of each individual leaf as well as the gap width. There was a slight decrease in the accuracy of leaf performance with increasing leaf speeds. The analysis results were presented through several graphs. The accuracy of the method was assessed as 0.01 mm for both the gap size and peak position determination.Conclusions: This study provides fast, easy, and accurate test methods for routine QA of the MLC performance and helps in faster troubleshooting of MLC problems in both IMRT and VMAT treatments. (C) 2012 American Association of Physicists in Medicine. [http://dx.doi.org/10.1118/1.4752207]