A tool to include gamma analysis software into a quality assurance program

PURPOSE: To provide a tool to enable gamma analysis software algorithms to be included in a quality assurance (QA) program.

METHODS: Four image sets were created comprising two geometric images to independently test the distance to agreement (DTA) and dose difference (DD) elements of the gamma algorithm, a clinical step and shoot IMRT field and a clinical VMAT arc. The images were analysed using global and local gamma analysis with 2 in-house and 8 commercially available software encompassing 15 software versions. The effect of image resolution on gamma pass rates was also investigated.

RESULTS: All but one software accurately calculated the gamma passing rate for the geometric images. Variation in global gamma passing rates of 1% at 3%/3mm and over 2% at 1%/1mm was measured between software and software versions with analysis of appropriately sampled images.

CONCLUSION: This study provides a suite of test images and the gamma pass rates achieved for a selection of commercially available software. This image suite will enable validation of gamma analysis software within a QA program and provide a frame of reference by which to compare results reported in the literature from various manufacturers and software versions.

Quality Assurance for GCxGC-FID, Accreditation for TPH CWG Protocol

A new technological approach in the analysis and forensic interpretation of Total Hydrocarbons in soils and waters using 2D Gas Chromatography method (GC-GC) was developed alongside environmental forensic and the assessment models to provide better customer products for the environmental industry.
The objective was to develop an analytical methodology for TPH CWG. Raw data from this method is then to be evaluated for forensic interpretation and risk assessment modelling. Access will be made available to the expertise in methods of forensic tracing contaminant sources, transport modelling, human health risk modelling and detailed quantitative risk assessment.
The quantification of internal standards was key to the development of this method. As the laboratory does not test for TPH in 1D, it was requested during INAB ISO 17025 audit to individually map out where each compound falls chromatographically in the 2D. This was done through comparing carbon equivalent numbers to the n-alkane carbons. This proved e.g. 2-methylnaphthalene has 11 carbons in its structure; its carbon equivalent is 12.84 , the result of which falls within the band of Aromatic eC12-eC16 as opposed to expected eC10-eC12. This was carried out for all 16 PAH (polyaromatic hydrocarbons) and BTEX (benzene, toluene, ethylbenzene and o, m and p-xylenes). The n-alkanes were also assigned to their corresponding aliphatic bands e.g. nC8 would be expected to be in nC8-nC10.
The method was validated through a designated systematic experimental protocol and was challenged with spikes of known concentration of hydrocarbon parameters such as recoveries, precision, bias and linearity. The method was verified by testing a certified reference material which was used as a proficiency round of testing for numerous laboratories.
It is hoped that the method will be used in conjunction with the analysis through Bonn Agreement with their OSINet group. This is a panel of experts and laboratories (including CLS) who forensically identify oil spill contamination from a water source.
This method can prove itself to be a robust method and benefit the industry for contaminated land and water but the method needs to be seen as separate from the regular 1D chromatography. It will help identify contaminants and assist consultants, regulators, clients and scientists valuable information not seen in 1D

Octavius 4D characterization for flattened and flattening filter free rotational deliveries

Purpose: In this study the Octavius detector 729 ionization chamber (IC) array with the Octavius 4D phantom was characterized for flattening filter (FF) and flattening filter free (FFF) static and rotational beams. The device was assessed for verification with FF and FFF RapidArc treatment plans.

Methods: The response of the detectors to field size, dose linearity, and dose rate were assessed for 6 MV FF beams and also 6 and 10 MV FFF beams. Dosimetric and mechanical accuracy of the detector array within the Octavius 4D rotational phantom was evaluated against measurements made using semiflex and pinpoint ionization chambers, and radiochromic film. Verification FF and FFF RapidArc plans were assessed using a gamma function with 3%/3 mm tolerances and 2%/2 mm tolerances and further analysis of these plans was undertaken using film and a second detector array with higher spatial resolution.

Results: A warm-up dose of >6 Gy was required for detector stability. Dose-rate measurements were stable across a range from 0.26 to 15 Gy/min and dose response was linear, although the device overestimated small doses compared with pinpoint ionization chamber measurements. Output factors agreed with ionization chamber measurements to within 0.6% for square fields of side between 3 and 25 cm and within 1.2% for 2 x 2 cm(2) fields. The Octavius 4D phantom was found to be consistent with measurements made with radiochromic film, where the gantry angle was found to be within 0.4. of that expected during rotational deliveries. RapidArc FF and FFF beams were found to have an accuracy of >97.9% and >90% of pixels passing 3%/3 mm and 2%/2 mm, respectively. Detector spatial resolution was observed to be a factor in determining the accurate delivery of each plan, particularly at steep dose gradients. This was confirmed using data from a second detector array with higher spatial resolution and with radiochromic film.

Conclusions: The Octavius 4D phantom with associated Octavius detector 729 ionization chamber array is a dosimetrically and mechanically stable device for pretreatment verification of FF and FFF RapidArc treatments. Further improvements may be possible through use of a detector array with higher spatial resolution (detector size and/or detector spacing). (C) 2013 American Association of Physicists in Medicine.

Implementation of phantom-less IMRT delivery verification using Varian DynaLog files and R/V output

This study aims to evaluate the use of Varian radiotherapy dynamic treatment log (DynaLog) files to verify IMRT plan delivery as part of a routine quality assurance procedure. Delivery accuracy in terms of machine performance was quantified by multileaf collimator (MLC) position errors and fluence delivery accuracy for patients receiving intensity modulated radiation therapy (IMRT) treatment. The relationship between machine performance and plan complexity, quantified by the modulation complexity score (MCS) was also investigated. Actual MLC positions and delivered fraction of monitor units (MU), recorded every 50 ms during IMRT delivery, were extracted from the DynaLog files. The planned MLC positions and fractional MU were taken from the record and verify system MLC control file. Planned and delivered beam data were compared to determine leaf position errors with and without the overshoot effect. Analysis was also performed on planned and actual fluence maps reconstructed from the MLC control file and delivered treatment log files respectively. This analysis was performed for all treatment fractions for 5 prostate, 5 prostate and pelvic node (PPN) and 5 head and neck (H&N) IMRT plans, totalling 82 IMRT fields in ∼5500 DynaLog files. The root mean square (RMS) leaf position errors without the overshoot effect were 0.09, 0.26, 0.19 mm for the prostate, PPN and H&N plans respectively, which increased to 0.30, 0.39 and 0.30 mm when the overshoot effect was considered. Average errors were not affected by the overshoot effect and were 0.05, 0.13 and 0.17 mm for prostate, PPN and H&N plans respectively. The percentage of pixels passing fluence map gamma analysis at 3%/3 mm was 99.94 ± 0.25%, which reduced to 91.62 ± 11.39% at 1%/1 mm criterion. Leaf position errors, but not gamma passing rate, were directly related to plan complexity as determined by the MCS. Site specific confidence intervals for average leaf position errors were set at -0.03-0.12 mm for prostate and -0.02-0.28 mm for more complex PPN and H&N plans. For all treatment sites confidence intervals for RMS errors with the overshoot was set at 0-0.50 mm and for the percentage of pixels passing a gamma analysis at 1%/1 mm a confidence interval of 68.83% was set also for all treatment sites. This work demonstrates the successful implementation of treatment log files to validate IMRT deliveries and how dynamic log files can diagnose delivery errors not possible with phantom based QC. Machine performance was found to be directly related to plan complexity but this is not the dominant determinant of delivery accuracy.

Optimization of image quality and dose for Varian aS500 electronic portal imaging devices (EPIDs)

This study was carried out to investigate whether the electronic portal imaging (EPI) acquisition process could be optimized, and as a result tolerance and action levels be set for the PIPSPro QC-3V phantom image quality assessment. The aim of the optimization process was to reduce the dose delivered to the patient while maintaining a clinically acceptable image quality. This is of interest when images are acquired in addition to the planned patient treatment, rather than images being acquired using the treatment field during a patient's treatment. A series of phantoms were used to assess image quality for different acquisition settings relative to the baseline values obtained following acceptance testing. Eight Varian aS500 EPID systems on four matched Varian 600C/D linacs and four matched Varian 2100C/D linacs were compared for consistency of performance and images were acquired at the four main orthogonal gantry angles. Images were acquired using a 6 MV beam operating at 100 MU min(-1) and the low-dose acquisition mode. Doses used in the comparison were measured using a Farmer ionization chamber placed at d(max) in solid water. The results demonstrated that the number of reset frames did not have any influence on the image contrast, but the number of frame averages did. The expected increase in noise with corresponding decrease in contrast was also observed when reducing the number of frame averages. The optimal settings for the low-dose acquisition mode with respect to image quality and dose were found to be one reset frame and three frame averages. All patients at the Northern Ireland Cancer Centre are now imaged using one reset frame and three frame averages in the 6 MV 100 MU min(-1) low-dose acquisition mode. Routine EPID QC contrast tolerance (+/-10) and action (+/-20) levels using the PIPSPro phantom based around expected values of 190 (Varian 600C/D) and 225 (Varian 2100C/D) have been introduced. The dose at dmax from electronic portal imaging has been reduced by approximately 28%, and while the image quality has been reduced, the images produced are still clinically acceptable.

External quality assessment of BRAF molecular analysis in melanoma

The availability of BRAF inhibitors has given metastatic melanoma patients an effective new treatment choice and molecular testing to determine the presence or absence of a BRAF codon 600 mutation is pivotal in the clinical management of these patients. This molecular test must be performed accurately and appropriately to ensure that the patient receives the most suitable treatment in a timely manner. Laboratories have introduced such testing; however, some experience low sample throughput making it critical that an external quality assurance programme is available to help promote a high standard of testing, reporting and provide an educational aspect for BRAF molecular testing. Laboratories took part in three rounds of external quality assessment (EQA) during a 12-month period giving participants a measure of the accuracy of genotyping, clinical interpretation of the result and experience in testing a range of different samples. Formalin fixed paraffin embedded tissue sections from malignant melanoma patients were distributed to participants for BRAF molecular testing. The standard of testing was generally high but distribution of a mutation other than the most common, p.(Val600Glu), highlighted concerns with detection or reporting of the presence of rarer mutations. The main issues raised in the interpretation of the results were the importance of clear unambiguous interpretation of the result tailored to the patient and the understanding that the treatment is different from that given to other stratified medicine programmes. The variability in reporting and wide range of methodologies used indicate a continuing need for EQA in this field.

Two Birds, One Stone: Combining Student Assessment and Socio-Legal Research

We describe here a method of assessment for students. A number of short-comings of traditional assessment methods, especially essays and examinations, are discussed and an alternative assessment method, the student project, is suggested. The method aims not just to overcome the short-comings of more traditional methods, but also to provide over-worked and under-resourced academics with viable primary data for socio-legal research work. Limitations to the method are discussed, with proposals for minimising the impact of these limitations. The whole �student project� approach is also discussed with reference to the Quality Assurance Agency benchmark standards for law degrees, standards which are expected of all institutions in the UK.

The immediate Life support course: implementation into an undergraduate nursing programme

This paper outlines how the immediate life support (ILS) course was incorporated into an undergraduate-nursing curriculum in a university in Northern Ireland. It also reports on how the students perceived the impact of this course on their clinical practice. The aim was to develop the student’s ability to recognise the acutely ill patient and to determine the relevance of this to clinical practice. Prior to this the ILS course was only available to qualified nurses and this paper reports on the first time students were provided with an ILS course in an undergraduate setting. The ILS course was delivered to 89 third year nursing students (Adult Branch) and comprised one full teaching day per week over two weeks. Recognised Advanced Life Support (ALS) instructors, in keeping with the United Kingdom Resuscitation Council guidelines, taught the students. Participants completed a 17 item questionnaire which comprised an open-ended section for student comment. Questionnaire data was analysed descriptively using SSPSS version 15.0. Open-ended responses from the questionnaire data was analysed by content and thematic analysis. Results Student feedback reported that the ILS course helped them understand what constituted the acutely ill patient and the role of the nurse in managing a deteriorating situation. Students also reported that they valued the experience as highlighting gaps in their knowledge Conclusion. The inclusion of the ILS course provides students with necessary skills to assess and manage the deteriorating patient. In addition the data from this study suggest the ILS course should be delivered in an inter-professional setting – i.e taught jointly with medical students. References: Department of Health & Quality Assurance Agency (2006). Department of Health Phase 2 benchmarking project – final report. Gloucester: Department of Health, London and Quality Assurance Agency for Higher Education

Current methods of analysis for the determination of trichothecene mycotoxins in food

This article describes the trends in analytical techniques for the determination of trichothecene mycotoxins, namely deoxynivalenol, and T-2 and HT-2 toxins in cereals and cereal products with particular emphasis on screening and rapid approaches. The driving force behind the changing methodologies is mainly attributed to legislative demands. However, for commercial and governmental testing laboratories, the need to use validated official methods is ever increasing to ensure quality assurance of results.

Nanocrystalline SnO2-based, UVB-activated, colourimetric oxygen indicator

Nanocrystalline SnO2, ncSnO(2), is used as a photosensitiser in a colourimetric O-2 indicator that comprises a sacrificial electron donor, glycerol, a redox dye, methylene blue (MB), and an encapsulating polymer, hydroxyethyl cellulose (HEC). Upon exposure to a burst of UVB light the indicator is activated (photo-bleached) as the MB is photoreduced by the ncSnO(2) particles. In the absence of oxygen, the film stays bleached, but recovers its original colour upon exposure to oxygen. Unlike its TiO2-based predecessor, the HEC/glycerol/MB/ncSnO(2) O-2 indicator is not activated by UVA light from white fluorescent lamps, but is by UVB light. This feature provides much greater control in the activation of the indicator. Other work shows the rate of activation depends upon I-0.75, where I is the UVB irradiance, indicating a partial dependence upon the electron-hole recombination process. The half-life of the recovery of the original colour of a UV-activated film, t(50), is directly proportional to the ambient level of oxygen. The advantages of using this indicator in modified atmosphere packaging as a possible quality assurance indicator are discussed briefly. (c) 2008 Elsevier B.V. All rights reserved.

Production of a monoclonal antibody and its application in an optical biosensor based assay for the quantitative measurement of Pantothenic Acid (Vitamin B5) in foodstuffs

Pantothenicacid (PA), vitamin B5, is an essential B vitamin that may be fortified in food and as such requires robust and accurate methods of detection to meet compliance legislation. This study reports the production and characterisation of the first monoclonalantibody (MAb) specific for PA and the subsequent development of a surface plasmon resonance (SPR) biosensorassay for the quantification of PA. The developed assay was compared with an SPR based commercial kit which utilised a polyclonal antibody (PAb). Foodstuffs, including cereals (n = 43), infant formulas and baby food (n = 10) and fruit juices (n = 48) were analysed by both the MAb and PAb biosensorassays and comparison plots showed good correlation (R2 0.77–0.99). The results indicate that the MAb basedbiosensorassay is suitable for the measurement of PA in foodstuffs and has the added advantage of facilitating a constant, long term supply of identical antibody. Preliminary matrix studies suggest the MAb basedassay is an excellent candidate for further validation studies and routine quality assurance based analysis.