Department of Radiation Oncology, University of Colorado School of Medicine, Aurora, CO, USA.
Department of Radiation Oncology, University of Southern California and Radiation Oncology Program, Childrens Hospital of Los Angeles, Los Angeles, CA, USA.
Med Phys. 2018 Apr;45(4):e53-e83. doi: 10.1002/mp.12810. Epub 2018 Mar 23.
Patient-specific IMRT QA measurements are important components of processes designed to identify discrepancies between calculated and delivered radiation doses. Discrepancy tolerance limits are neither well defined nor consistently applied across centers. The AAPM TG-218 report provides a comprehensive review aimed at improving the understanding and consistency of these processes as well as recommendations for methodologies and tolerance limits in patient-specific IMRT QA.
The performance of the dose difference/distance-to-agreement (DTA) and γ dose distribution comparison metrics are investigated. Measurement methods are reviewed and followed by a discussion of the pros and cons of each. Methodologies for absolute dose verification are discussed and new IMRT QA verification tools are presented. Literature on the expected or achievable agreement between measurements and calculations for different types of planning and delivery systems are reviewed and analyzed. Tests of vendor implementations of the γ verification algorithm employing benchmark cases are presented.
Operational shortcomings that can reduce the γ tool accuracy and subsequent effectiveness for IMRT QA are described. Practical considerations including spatial resolution, normalization, dose threshold, and data interpretation are discussed. Published data on IMRT QA and the clinical experience of the group members are used to develop guidelines and recommendations on tolerance and action limits for IMRT QA. Steps to check failed IMRT QA plans are outlined.
Recommendations on delivery methods, data interpretation, dose normalization, the use of γ analysis routines and choice of tolerance limits for IMRT QA are made with focus on detecting differences between calculated and measured doses via the use of robust analysis methods and an in-depth understanding of IMRT verification metrics. The recommendations are intended to improve the IMRT QA process and establish consistent, and comparable IMRT QA criteria among institutions.
患者特异性调强放射治疗（IMRT）QA 测量是识别计算剂量与实际交付剂量之间差异的过程的重要组成部分。容差限制在各中心之间既没有得到很好的定义，也没有得到一致的应用。AAPM TG-218 报告提供了全面的审查，旨在提高对这些过程的理解和一致性，并为患者特异性 IMRT QA 中的方法和容差限制提供建议。
研究了剂量差异/协议距离（DTA）和γ剂量分布比较指标的性能。审查了测量方法，并讨论了每种方法的优缺点。讨论了绝对剂量验证的方法，并提出了新的 IMRT QA 验证工具。审查和分析了不同类型的计划和交付系统的测量值和计算值之间预期或可实现的一致性的文献。介绍了对采用基准案例的γ验证算法的供应商实现的测试。
描述了可能降低γ工具准确性以及随后对 IMRT QA 的有效性的操作缺陷。讨论了包括空间分辨率、归一化、剂量阈值和数据解释在内的实际考虑因素。利用 IMRT QA 发布的数据和小组成员的临床经验，制定了 IMRT QA 的容差和行动限制的指南和建议。概述了检查失败的 IMRT QA 计划的步骤。
对交付方法、数据解释、剂量归一化、γ分析程序的使用以及 IMRT QA 的容差限制的选择提出了建议，重点是通过使用稳健的分析方法和深入了解 IMRT 验证指标来检测计算剂量与测量剂量之间的差异。这些建议旨在改善 IMRT QA 过程，并在各机构之间建立一致和可比的 IMRT QA 标准。
