Radiation Therapy Section, Department of Clinical Support, Hiroshima University Hospital, Hiroshima 734-8551, Japan; Department of Radiation Oncology, Graduate School of Biomedical & Health Sciences, Hiroshima University, Hiroshima 734-8551, Japan.
Department of Radiation Oncology, Hiroshima University Hospital, Hiroshima 734-8551, Japan.
Phys Med. 2019 Feb;58:59-65. doi: 10.1016/j.ejmp.2019.01.014. Epub 2019 Jan 29.
The output of a linear accelerator (linac) is one of the most important quality assurance (QA) factors in radiotherapy. However, there is no quantitative rationale for frequency and tolerance. The purpose of this study is to develop a novel risk analysis of clinical reference dosimetry based on failure modes and effects analysis (FMEA).
Clinical reference dosimetry data and the daily output data of two linacs (Clinac iX and Clinac 6EX) at Hiroshima University Hospital were analyzed. The analysis involved the number of patients per year for five types of fractionations. Risk priority number (RPN) is defined as the product of occurrence (O), severity (S), and detectability (D) in standard FMEA. In addition, we introduced "severity due to output drifting" (mean output change per day) (S') and the number of patients per year for five types of fractionations (W). We calculated the RPN = O × S × D × S' × W and quantitatively evaluated the risk for clinical reference dosimetry.
Fewer fractions and less output calibration frequency resulted in higher RPN. Since clinical reference dosimetry data has a drift effect, which is missing in human processes, it was essential to use S' in addition to standard FMEA. Moreover, the parameter W was important in evaluating interinstitutional QA for clinical reference dosimetry. The relative risk of Clinac 6EX to Clinac iX was different approximately by twofold.
We developed a novel index that can quantitatively evaluate risk for clinical reference dosimetry of each facility and machines in common on the basis of FMEA.
直线加速器（linac）的输出是放射治疗中最重要的质量保证（QA）因素之一。然而，其频率和容差没有定量依据。本研究旨在基于失效模式和影响分析（FMEA）开发一种新的临床参考剂量学的风险分析。
分析了广岛大学医院两台直线加速器（Clinac iX 和 Clinac 6EX）的临床参考剂量学数据和日常输出数据。分析涉及每年五种分割类型的患者数量。风险优先数（RPN）是标准 FMEA 中发生（O）、严重度（S）和可探测性（D）的乘积。此外，我们引入了“由于输出漂移导致的严重度”（每天的平均输出变化）（S'）和每年五种分割类型的患者数量（W）。我们计算了 RPN=O×S×D×S'×W，并对临床参考剂量学的风险进行了定量评估。
分割次数越少，输出校准频率越低，RPN 越高。由于临床参考剂量学数据存在漂移效应，这在人为过程中是缺失的，因此除了标准 FMEA 之外，使用 S'是必不可少的。此外，参数 W 在评估临床参考剂量学的机构间 QA 方面很重要。Clinac 6EX 相对于 Clinac iX 的相对风险大约相差两倍。
我们基于 FMEA 开发了一种新的指标，可以对每个机构和机器的临床参考剂量学风险进行定量评估。
