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Do the representative beam data for TrueBeam <sup>?</sup> linear accelerators represent average data?
摘要： If the vendor's representative beam data (RBD) for TrueBeam linear accelerators are to be valid for use in clinical practice, the variations in the beam data used for beam modeling must be small. Although a few studies have reported the variation of the beam data of the TrueBeam machines, the numbers of machines analyzed in those studies were small. In this study, we investigated the variation in the beam data for 21 TrueBeam machines collected from 17 institutions with their agreement. In the exponential regions, the percent depth dose (PDD) values showed very small variation, <1% for all the photon energies analyzed. Similarly, the off‐center ratio (OCR) values also showed small variation for all energies. In the ?eld regions, the standard deviations of the values of dose difference (DD) between the data for each machine and the study average were <1% for ?eld sizes ≥100 × 100 mm2. The maximum distance‐to‐agreement from the average data was <0.5 mm in the penumbra regions. The output factor (OPF) values also showed very small variation (<1%) for all energies and ?eld sizes. Both the PDD and OCR of the average study data showed good agreement with the vendor's RBD for ?eld sizes ≥100 × 100 mm2. The OPF of the average study data also showed good agreement with the vendor's RBD for all ?eld sizes. However, although all the institutions used ionization chambers with similar cavity volumes, the 30 × 30 mm2 ?eld size showed large DD variations (≥2%) in OCR in the ?eld regions. We conclude that the intermachine variability of TrueBeam linear accelerators was very small except for small ?eld dosimetry, supporting the validity of the use of the RBD for clinical applications. The use of the vendor's RBD might greatly facilitate the quick installation of a new linear accelerator.
关键词： commissioning,linear accelerator,representative beam data
更新于2025-09-23 15:23:52
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Application of TG-100 risk analysis methods to the acceptance testing and commissioning process of a Halcyon linear accelerator
摘要： 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 pre-assembled and pre-configured dual-layer MLC, ring-gantry linac – HalcyonTM (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 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. 14 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 Failure Modes and Effects Analysis and quality control measures to mitigate the failure modes for the acceptance testing and commissioning 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 improve the design features of future ring-gantry type of linacs that are likely to be pre-assembled, pre-configured, and heavily reliant on automation and image-guidance.
关键词： new ring-gantry linac,reference dosimetry,TG100,TG-51,Failure Modes and Effects Analysis (FMEA),Acceptance testing and Commissioning
更新于2025-09-23 15:23:52
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Spider beam source ready for operation
摘要： The SPIDER Beam Source (BS), the first prototype of a full scale ion source for the ITER Heating Neutral Beam injector, was delivered to the Neutral Beam Test Facility (NBTF) site in Padova (Italy) after about five years procurement phase. A huge effort was devoted during the procurement for quality controls and testing at the supplier's workshops. Several activities were also carried out on NBTF site for verification/adjustment of interfaces, solution of still open issues, as well as final tests before and after installation inside the vacuum vessel. The NBTF Team undertook the BS site acceptance tests including: pressure and leak tests of the hydraulic circuits; electrical tests; measurement of magnetic field profiles; functionality tests of diagnostics installed on the BS; checks of grids alignment by means of laser tracker. Accurate positioning of the BS inside the vacuum vessel was performed and various service lines were connected in a tight space. Several improvements were undertaken in order to guarantee reliability and reduce the risks during the commissioning and experimental campaign in 2018. After installation, the integrated commissioning phase was initiated, powering the RF and high voltage circuits, followed by the first operation in vacuum.
关键词： Installation,Test,Beam source,RF plasma,SPIDER,Commissioning
更新于2025-09-19 17:15:36