Initial investigation using statistical process control for quality control of accelerator beam steering

<p>Abstract</p> <p>Background</p> <p>This study seeks to increase clinical operational efficiency and accelerator beam consistency by retrospectively investigating the application of statistical process control (SPC) to linear accelerator beam steering parameters to determine the utility of such a methodology in detecting changes prior to equipment failure (interlocks actuated).</p> <p>Methods</p> <p>Steering coil currents (SCC) for the transverse and radial planes are set such that a reproducibly useful photon or electron beam is available. SCC are sampled and stored in the control console computer each day during the morning warm-up. The transverse and radial - positioning and angle SCC for photon beam energies were evaluated using average and range (Xbar-R) process control charts (PCC). The weekly average and range values (subgroup n = 5) for each steering coil were used to develop the PCC. SCC from September 2009 (annual calibration) until two weeks following a beam steering failure in June 2010 were evaluated. PCC limits were calculated using the first twenty subgroups. Appropriate action limits were developed using conventional SPC guidelines.</p> <p>Results</p> <p>PCC high-alarm action limit was set at 6 standard deviations from the mean. A value exceeding this limit would require beam scanning and evaluation by the physicist and engineer. Two low alarms were used to indicate negative trends. Alarms received following establishment of limits (week 20) are indicative of a non-random cause for deviation (Xbar chart) and/or an uncontrolled process (R chart). Transverse angle SCC for 6 MV and 15 MV indicated a high-alarm 90 and 108 days prior to equipment failure respectively. A downward trend in this parameter continued, with high-alarm, until failure. Transverse position and radial angle SCC for 6 and 15 MV indicated low-alarms starting as early as 124 and 116 days prior to failure, respectively.</p> <p>Conclusion</p> <p>Radiotherapy clinical efficiency and accelerator beam consistency may be improved by instituting SPC methods to monitor the beam steering process and detect abnormal changes prior to equipment failure.</p> <p><b>PACS numbers: </b>87.55n, 87.55qr, 87.56bd</p

Phase 2 Technical Letter Report TS-00358: Portable Acoustic Contraband Detector

This report provides the results of all PNNL managed activities on this project, and contains a description of the data acquisition configuration and testing protocols, results and conclusions from this work. This report is part of the final deliverables package submitted to the client during Phase 2 of Project 52042

Cultural and leadership predictors of corporate social responsibility values of top management: A GLOBE study of 15 countries.

This paper examines cultural and leadership variables associated with corporate social responsibility values that managers apply to their decision-making. In this longitudinal study, we analyze data from 561 firms located in 15 countries on five continents to illustrate how the cultural dimensions of institutional collectivism and power distance predict social responsibility values on the part of top management team members. CEO visionary leadership and integrity were also uniquely predictive of such values. Journal of International Business Studies (2006) 37, 823–837. doi:10.1057/palgrave.jibs.8400230

Comparison of CT and PET-CT based planning of radiation therapy in locally advanced pancreatic carcinoma

Abstract Background To compare computed tomography (CT) with co-registered positron emission tomography-computed tomography (PET-CT) as the basis for delineating gross tumor volume (GTV) in unresectable, locally advanced pancreatic carcinoma (LAPC). Methods Fourteen patients with unresectable LAPC had both CT and PET images acquired. For each patient, two three-dimensional conformal plans were made using the CT and PET-CT fusion data sets. We analyzed differences in treatment plans and doses of radiation to primary tumors and critical organs. Results Changes in GTV delineation were necessary in 5 patients based on PET-CT information. In these patients, the average increase in GTV was 29.7%, due to the incorporation of additional lymph node metastases and extension of the primary tumor beyond that defined by CT. For all patients, the GTVCT versus GTVPET-CT was 92.5 ± 32.3 cm3 versus 104.5 ± 32.6 cm3 (p = 0.009). Toxicity analysis revealed no clinically significant differences between two plans with regard to doses to critical organs. Conclusion Co-registration of PET and CT information in unresectable LAPC may improve the delineation of GTV and theoretically reduce the likelihood of geographic misses.</p

Primary Schoolchildren’s Experiences of Participatory Theatre in a Heritage Site

There is a growing need for articulation of the theoretical framework underpinning performance as a learning medium in heritage sites and for an in-depth insight into the children's experiences therein. The aim of this paper is to explore some of the themes that emerged from researching participatory theatre in a historic house as experienced by two primary school groups. The methodology drawing upon the principles of participatory research with children and a constructivist theoretical framework employed interviews, observations and drawings as data generation methods to explore the children's individual and collective experiences. The research findings underline the interplay between the events' theatrical and interpretive format and advocate the significance of children's co-authorship of such events

A Reliability-Generalization Study of Journal Peer Reviews: A Multilevel Meta-Analysis of Inter-Rater Reliability and Its Determinants

Background: This paper presents the first meta-analysis for the inter-rater reliability (IRR) of journal peer reviews. IRR is defined as the extent to which two or more independent reviews of the same scientific document agree. Methodology/Principal Findings: Altogether, 70 reliability coefficients (Cohen’s Kappa, intra-class correlation [ICC], and Pearson product-moment correlation [r]) from 48 studies were taken into account in the meta-analysis. The studies were based on a total of 19,443 manuscripts; on average, each study had a sample size of 311 manuscripts (minimum: 28, maximum: 1983). The results of the meta-analysis confirmed the findings of the narrative literature reviews published to date: The level of IRR (mean ICC/r 2 =.34, mean Cohen’s Kappa =.17) was low. To explain the study-to-study variation of the IRR coefficients, meta-regression analyses were calculated using seven covariates. Two covariates that emerged in the metaregression analyses as statistically significant to gain an approximate homogeneity of the intra-class correlations indicated that, firstly, the more manuscripts that a study is based on, the smaller the reported IRR coefficients are. Secondly, if the information of the rating system for reviewers was reported in a study, then this was associated with a smaller IRR coefficient than if the information was not conveyed. Conclusions/Significance: Studies that report a high level of IRR are to be considered less credible than those with a low level o

Phase 2 Technical Letter Report TS-00358: Portable Acoustic Contraband Detector

This report provides the results of all PNNL managed activities on this project, and contains a description of the data acquisition configuration and testing protocols, results and conclusions from this work. This report is part of the final deliverables package submitted to the client during Phase 2 of Project 52042

Operational consistency of medical linear accelerators manufactured and commissioned in series

The purpose of this study was to determine if medical linear accelerators (linac) produced by the same manufacturer exhibit operational consistency within their subsystems and components. Two linacs that were commissioned together and installed at the same facility were monitored. Each machine delivered a daily robust quality assurance (QA) irradiation. Linacs and their components operate consistently, but have different operational parameter levels even when produced by the same manufacturer and commissioned in series. These findings have implications on the feasibility of true clinical beam matching. Keywords: Statistical process control, Medical linear accelerator, Performance, Quality assuranc