Application of TG‐100 risk analysis methods to the acceptance testing and commissioning process of a Halcyon linear accelerator

Abstract

Purpose A new type of linear accelerator (linac) was recently introduced into the market by a major manufacturer. Our institution is one of the early users of this preassembled and preconfigured dual‐layer multileaf collimator (MLC), ring‐gantry linac — Halcyon™ (1st version). We performed a set of full acceptance testing and commissioning (ATC) measurements for three Halcyon machines and compared the measured data with the standard beam model provided by the manufacturer. The ATC measurements were performed following the guidelines given in different AAPM protocols as well as guidelines provided by the manufacturer. The purpose of the present work was to perform a risk assessment of the ATC process for this new type of linac and investigate whether the results obtained from this analysis could potentially be used as a guideline for improving the design features of this type of linac. Methods AAPM's TG100 risk assessment methodology was applied to the ATC process. The acceptance testing process relied heavily on the use of a manufacturer‐supplied phantom and the automated analysis of electronic portal imaging device (EPID) images. For the commissioning process, a conventional measurement setup and process (e.g., use of water tank for scanning) was largely used. ATC was performed using guidelines recommended in various AAPM protocols (e.g., TG‐106, TG‐51) as well as guidelines provided by the manufacturer. Six medical physicists were involved in this study. Process maps, process steps, and failure modes (FMs) were generated for the ATC procedures. Failure modes and effects analysis (FMEA) were performed following the guidelines given in AAPM TG‐100 protocol. The top 5 and top 10 highest‐ranked FMs were identified for the acceptance and commissioning procedures, respectively. Quality control measures were suggested to mitigate these FMs. Results A total of 38 steps and 88 FMs were identified for the entire ATC process. Fourteen steps and 34 FMs arose from acceptance testing. The top 5 FMs that were identified could potentially be mitigated by the manufacturer. For commissioning, a total of 24 steps and 54 potential FMs were identified. The use of separate measurement tools that are not machine‐integrated has been identified as a cause for the higher number of steps and FMs generated from the conventional ATC approach. More than half of the quality control measures recommended for both acceptance and commissioning could potentially be incorporated by the manufacturer in the design of the Halcyon machine. Conclusion This paper presents the results of FMEA and quality control measures to mitigate the FMs for the ATC process for Halcyon machine. Unique FMs that result from the differences in the ATC guidelines provided by the vendor and current conventional protocols, and the challenges of performing the ATC due to the new linac features and ring‐gantry design were highlighted for the first time. The FMs identified in the present work along with the suggested quality control measures, could potentially be used to impro...

Technical Note: Dosimetric characterization of the dynamic beam flattening MLC sequence on a ring shaped, Jawless Linear Accelerator with double stacked MLC

“…To overcome this problem, a beam flattening sequence was designed for a 6XFFF field which utilized a fixed‐MLC sequence to sweep the field and was made available on the Halcyon 2.0. Teo et al described the application of TG‐100 to the commissioning process for the Halcyon however because they were working off a version 1.0 model, did not discuss dynamic beam flattening (DBF) . The use of the DBF feature enables the potential for 3D‐style forward planning to be carried out on the Halcyon platform with a minimal level of complexity.…”

“…Teo et al described the application of TG-100 to the commissioning process for the Halcyon however because they were working off a version 1.0 model, did not discuss dynamic beam flattening (DBF). 4 The use of the DBF feature enables the potential for 3D-style forward planning to be carried out on the Halcyon platform with a minimal level of complexity. This is particularly applicable for busy radiotherapy centers with large patient loads.…”

Clinical safety assessment of the Halcyon system

“…Previous risk assessment of the Halcyon focused on acceptance and commissioning using TG‐100 risk assessment methodology . In that work, the vendor‐defined acceptance test procedures were analyzed as well as the traditional commissioning process that included, for example, setting up a large three‐dimensional water tank for beam scanning, measuring output factors, etc.…”

“…There are a number of publications that either evaluate the operation of the Halcyon or provide recommendations on its clinical use . A recent publication provided a risk assessment of Halcyon acceptance testing and commissioning processes using the TG‐100 methodology . In that work, 142 failure modes were identified with the top risk priority number (RPN) values ranging from 85.5 to 95.0 for the acceptance testing and commissioning, respectively.…”

“…[1][2][3][4][5][6][7][8][9][10][11] A recent publication provided a risk assessment of Halcyon acceptance testing and commissioning processes using the TG-100 methodology. 12 In that work, 142 failure modes were identified with the top risk priority number (RPN) values ranging from 85.5 to 95.0 for the acceptance testing and commissioning, respectively. Mitigation strategies for some of the failure modes were proposed both for the clinical physicist and for the vendor.…”