Characterization of XR-RV3 GafChromic® films in standard laboratory and in clinical conditions and means to evaluate uncertainties and reduce errors
Characterization of XR-RV3 GafChromic® films in standard laboratory and in clinical conditions and means to evaluate uncertainties and reduce errors
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DOI：
10.1118/1.4922132
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发表时间：
2015-07-01
期刊：
影响因子：
3.8
通讯作者：
Knezevic, Z.
中科院分区：
文献类型：
--
作者：
Farah, J.;Trianni, A.;Knezevic, Z.
目的：研究最佳使用XR-RV 3 GafChromic（R）胶片评估介入放射学中患者皮肤剂量，同时解决降低剂量评估不确定性的方法：XR-R型GafChromic胶片已被证明是最有效和最合适的解决方案，以确定介入手术中患者皮肤剂量。由于薄膜剂量测定可能具有很高的不确定性，本文提出了EURADOS WG 12倡议，以多地点方法对薄膜特性进行全面研究。考虑的不确定性来源包括扫描仪、胶片和装配相关误差。这项工作的重点是研究电影的行为与临床高剂量率脉冲光束（以前在文献中不可用）连同参考标准的实验室beams.Results：首先，性能分析六种不同的扫描仪型号已表明，扫描均匀性垂直于灯的运动轴，长期稳定性的扫描仪相关的不确定性的主要来源。除非定期检查和纠正，否则这些可能会导致胶片读数出现高达7%的误差。通常，应进行扫描均匀性校正矩阵和针对扫描仪特定和日常背景阅读的阅读标准化。此外，对多个胶片批次的分析表明，XR-RV 3胶片在一个批次内通常具有良好的均匀性（< 1.5%），在辐照后需要24小时才能稳定，并且它们的响应大致与剂量率无关（< 5%）。然而，XR-RV 3胶片在标准实验室和临床条件下的辐射质量差异很大（高达15%）。因此，在进行患者皮肤剂量测量之前，必须根据临床使用的X射线系统的特性选择适当的校准射束质量。此外，应优先使用黄色侧膜照射，因为与白色侧膜照射相比，它们显示出对光束参数的较低依赖性。最后，在这项工作中测试的六个不同的拟合方程中，通常使用的三阶多项式和更合理和简单的方程，剂量与像素值成反比的形式，都被发现提供令人满意的结果。拟合相关的不确定性被明确确定为一个主要贡献者的整体电影剂量测定的不确定性高达40%的错误上的剂量estimation.Conclusions：与使用的XR-RV 3电影，以确定皮肤剂量在介入环境中的整体不确定性可以现实地估计为20%左右（k = 1）。如果仔细监控扫描仪、胶片和装配相关的错误，这种不确定性可以降低到5%以内，如果不小心，这种不确定性很容易增加到40%以上。这项工作证明了适当的校准，阅读，拟合，和其他电影相关的和扫描相关的过程，这将有助于提高皮肤剂量测量介入手术的准确性的重要性。(C)2015年美国医学物理学家协会。
Purpose: To investigate the optimal use of XR-RV3 GafChromic (R) films to assess patient skin dose in interventional radiology while addressing the means to reduce uncertainties in dose assessment.Methods: XR-Type R GafChromic films have been shown to represent the most efficient and suitable solution to determine patient skin dose in interventional procedures. As film dosimetry can be associated with high uncertainty, this paper presents the EURADOS WG 12 initiative to carry out a comprehensive study of film characteristics with a multisite approach. The considered sources of uncertainties include scanner, film, and fitting-related errors. The work focused on studying film behavior with clinical high-dose-rate pulsed beams (previously unavailable in the literature) together with reference standard laboratory beams.Results: First, the performance analysis of six different scanner models has shown that scan uniformity perpendicular to the lamp motion axis and that long term stability are the main sources of scanner-related uncertainties. These could induce errors of up to 7% on the film readings unless regularly checked and corrected. Typically, scan uniformity correction matrices and reading normalization to the scanner-specific and daily background reading should be done. In addition, the analysis on multiple film batches has shown that XR-RV3 films have generally good uniformity within one batch (< 1.5%), require 24 h to stabilize after the irradiation and their response is roughly independent of dose rate (< 5%). However, XR-RV3 films showed large variations (up to 15%) with radiation quality both in standard laboratory and in clinical conditions. As such, and prior to conducting patient skin dose measurements, it is mandatory to choose the appropriate calibration beam quality depending on the characteristics of the x-ray systems that will be used clinically. In addition, yellow side film irradiations should be preferentially used since they showed a lower dependence on beam parameters compared to white side film irradiations. Finally, among the six different fit equations tested in this work, typically used third order polynomials and more rational and simplistic equations, of the form dose inversely proportional to pixel value, were both found to provide satisfactory results. Fitting-related uncertainty was clearly identified as a major contributor to the overall film dosimetry uncertainty with up to 40% error on the dose estimate.Conclusions: The overall uncertainty associated with the use of XR-RV3 films to determine skin dose in the interventional environment can realistically be estimated to be around 20% (k = 1). This uncertainty can be reduced to within 5% if carefully monitoring scanner, film, and fitting-related errors or it can easily increase to over 40% if minimal care is not taken. This work demonstrates the importance of appropriate calibration, reading, fitting, and other film-related and scan-related processes, which will help improve the accuracy of skin dose measurements in interventional procedures. (C) 2015 American Association of Physicists in Medicine.