Quality Assurance Device Research Articles

Comparison of Patient-Specific Quality Assurance Devices in Radiation Therapy

This study aimed to compare the results of patient-specific quality assurance (PSQA) between MapCHECK and Octavius for radiation therapy. A total of 50 patients with passing PSQA results were included. The point dose difference (DD) and gamma passing rate (GPR) were analyzed to evaluate the agreement between the measured and planned data, and the PSQA results from the two quality assurance (QA) devices were compared for all cases. The DDs and GPRs were within the tolerance ranges in all of the cases. The average GPR difference between the two detectors was statistically significant for the brain and the H&N values for the gamma criteria were 3%/3 mm, 2%/2 mm, and 1%/1 mm. These PSQA systems can be used interchangeably for routine PSQA during the delivery of radiation therapy.

Evaluation of a prototype array for daily quality assurance in spot scanning proton therapy.

Quality assurance (QA) on a daily basis is an essential task in radiotherapy. In pencil beam scanning proton therapy (PBS), there is a lack of available practical QA devices for routine daily QA in comparison to conventional radiotherapy. The aim was to characterize and evaluate a prototype for the task of daily QA routine for PBS with parameters recommended by the AAPM TG 224, that is, the dose output constancy, the spot position and the distal range verification. Furthermore, a time efficient calibration method for fast and reliable daily QA routine was established for theprototype. First, a calibration routine was designed and evaluated, which characterizes the array response and allows for a conversion of the measured signal to clinically needed QA parameters. Finally, a time and resource efficient daily QA routine was developed andtested. The prototype array can distinguish spot position deviations with sub-millimeter accuracy, as well as changes in the spot size in terms of FWHM with a 2 sensitivity. The range and thus the energy can be evaluated at different depths also with sub-millimeter precision. After some training, the setup of the prototype device took roughly two minutes and the total beamtime was about one minuteon cyclotron site and five minutesfor synchrotrons. A prototype for daily QA in spot scanning proton therapy was evaluated, which features a fast and easy setup and allows for measuring relevant beam parameters, typically within less than a minute of beam time. All QA parameters as recommended by the AAPM TG 224 report can be analyzed with sufficientaccuracy.

Characterisation of 3D-printable thermoplastics to be used as tissue-equivalent materials in photon and proton beam radiotherapy end-to-end quality assurance devices

Objective. To investigate the potential of 3D-printable thermoplastics as tissue-equivalent materials to be used in multimodal radiotherapy end-to-end quality assurance (QA) devices. Approach. Six thermoplastics were investigated: Polylactic Acid (PLA), Acrylonitrile Butadiene Styrene (ABS), Polyethylene Terephthalate Glycol (PETG), Polymethyl Methacrylate (PMMA), High Impact Polystyrene (HIPS) and StoneFil. Measurements of mass density ( ρ ), Relative Electron Density (RED), in a nominal 6 MV photon beam, and Relative Stopping Power (RSP), in a 210 MeV proton pencil-beam, were performed. Average Hounsfield Units (HU) were derived from CTs acquired with two independent scanners. The calibration curves of both scanners were used to predict average ρ, RED and RSP values and compared against the experimental data. Finally, measured data of ρ, RED and RSP was compared against theoretical values estimated for the thermoplastic materials and biological tissues. Main results. Overall, good ρ and RSP CT predictions were made; only PMMA and PETG showed differences >5%. The differences between experimental and CT predicted RED values were also <5% for PLA, ABS, PETG and PMMA; for HIPS and StoneFil higher differences were found (6.94% and 9.42/15.34%, respectively). Small HU variations were obtained in the CTs for all materials indicating good uniform density distribution in the samples production. ABS, PLA, PETG and PMMA showed potential equivalency for a variety of soft tissues (adipose tissue, skeletal muscle, brain and lung tissues, differences within 0.19%–8.35% for all properties). StoneFil was the closest substitute to bone, but differences were >10%. Theoretical calculations of all properties agreed with experimental values within 5% difference for most thermoplastics. Significance. Several 3D-printed thermoplastics were promising tissue-equivalent materials to be used in devices for end-to-end multimodal radiotherapy QA and may not require corrections in treatment planning systems’ dose calculations. Theoretical calculations showed promise in identifying thermoplastics matching target biological tissues before experiments are performed.

A virtual phantom for patient-specific QA On A 1.5T MR-linac.

Create a virtual ArcCHECK-MR phantom, customized for a 1.5TMR-linac, with consideration of the different density regions within the quality assurance (QA) phantom, aiming to streamline the utilization of this specialized QA device. A virtual phantom was constructed in the treatment planning system (TPS) to replicate the ArcCHECK-MR's composition, consisting of five distinct layers: "Outer" (representing the outer PMMA ring), "Complex" (simulating the printed circuit boards), "Detectors" (encompassing the detector area), "Inner" (signifying the inner PMMA ring) and "Insert" (representing the PMMA insert). These layers were defined based on geometric data and represented as contour points on a set of dummy CT images. Additionally, a setup platform was integrated as contoured structures. To determine the relative electron density (RED) values of the external and internal PMMA components, measurements were taken at 25 points in the insert using an ion chamber. A novel method for establishing the exit/entrance dose ratio (EEDR) for ArcCHECK-MR was introduced. The RED of higher density region was derived by evaluating the local gamma index passing rate results with criteria of 2% dose difference and 2mm distance-to-agreement. The performance of the virtual phantom was assessed for Unity 7 FFF beams with a 1.5T magnetic field. The radii of the five ring structures within the virtual phantom measured 133.0mm, 110.0mm, 103.4mm, 100.0mm, and 75.0mm for the "Outer," "Complex," "Detectors," "Inner" and "Insert" regions, respectively. The RED values were as follows: ArcCHECK-MR PMMA had a RED of 1.130, "Detectors" were assumed to have a RED of 1.000, "Complex" had a RED of 1.200, and the setup QA phantom justified a RED of 1.350. Early validation results demonstrate that the 5-layer virtual phantom, when compared to the commonly used bulk overridden phantom, offers improved capability in MR-linac environments. This enhancement led to an increase in passing rates for the local gamma index by approximately 5 ∼ 6%, when applying the criteria of 2%, 2mm. We have successfully generated a virtual representation of the distinct regions within the ArcCHECK-MR using a TPS, addressing the challenges associated with its use in conjunction with a 1.5T MR-linac. We consistently observed favorable local gamma index passing rates across two 1.5T MR-linac and ArcCHECK-MR unit combinations. This approach has the potential to minimize uncertainties in the creation of the QA phantom for ArcCHECK-MR across various institutions.

Comprehensive characterisation of the IBA myQA SRS for SRS and SBRT patient specific quality assurance.

The myQA SRS (IBA) is a new to market 2D complementary metal oxide semiconductor detector array with an active area 140 × 120mm2 and 0.4mm resolution, making it a potential real-time dosimetry alternative to radiochromic film for stereotactic plan verification. Characterisation of the device was completed to assess performance. The dosimetric properties of the device were assessed for 6FF and 6FFF beams from a Varian TrueBeam STx with high definition multileaf collimator. Clinical suitability of the device for Patient Specific Quality Assurance was verified using ten SRS/SBRT plans, compared against other detectors, as well as multi leaf collimator (MLC) tests including picket fence and chair. Gamma analysis was performed using myQA software with criteria of 4%/1mm. The device demonstrated compliance with recommended specifications for basic tests. After the required warm-up period, the maximum deviation in detector signal from initial readings was 0.2%. Short-term and long-term reproducibility was 0.1% (6FF) and 1.0% (6FFF), respectively. Dose linearity was within 0.3% (6FF) and 0.7% (6FFF) and dose-rate dependence within 1.7% (6FF) and 2.9% (6FFF) and were verified with a Farmer type ionization chamber (PTW 30013). Angular dependence was quantified for coplanar and non-coplanar situations. Output factors and beam profiles measured on the device showed agreement within 1% of baseline RAZOR diode (IBA) and CC04 ionisation chamber (IBA) measurements for field sizes 1 × 1 to 10 × 10cm2. The minimum gamma (4%/1mm) pass rates for MLC-pattern tests were 96.5% and 98.1% for the myQA SRS and film, respectively. The average gamma (4%/1mm) pass rates for SBRT and SRS plans were 98.8% and 99.8% respectively. This work represents one of the first studies performed on the commissioning and performance characterisation of this novel device, demonstrating its accuracy and reliability, making it highly useful as a film alternative in stereotactic treatment plan verification.

Monitoring linear accelerator beam with daily quality assurance phantom

This paper aims to analyze the output constancy of a medical linear accelerator using PTW, and to study the suitability as a daily quality assurance device. It is assumed that the device is sensitive enough to detect minor variations in central axis beam, flatness, symmetry, and beam quality factor. PTW, QUICKCHECKwebline is the most efficient wireless device used in daily quality assurance. The measurements of output doses of photons ( 6MV and 15 MV) and electrons (6,9,12, and 15MeV) from a medical linear accelerator before the daily treatment have been graphically analyzed. This study assures the output stability of Varian Clinac iX 2100 CD linear accelerator at Bhaktapur Cancer Hospital, Bhaktapur, Nepal. The beam flatness, symmetry, beam quality factor, and central axis of photon and electron beam have been analyzed for 10x10cm2 and 20x20cm2 field size in separate ways. Among the measurements, observed parameters lie under the tolerance limit as recommended by American Association of Physicists in Medicine viz. ±3%. The outcomes of the measurements are in the acceptable range for the treatment procedure of patients.

A Comparison of Patient-specific Delivery Quality Assurance (DQA) Devices in Radiation Therapy

A Comparison of Patient-specific Delivery Quality Assurance (DQA) Devices in Radiation Therapy

Investigation of the degree of cross-linking of polyethylene and thermosets using absolute optical spectroscopy and Raman microscopy

Abstract. In the research work presented here, an integrating sphere demonstrator which is suitable for the non-destructive determination of the degree of cross-linking or curing and has the potential for use as an at-line device for in-process quality assurance was assembled and explored. The measurement system allows the analysis of absorption and scattering coefficients of materials independently by means of absolute optical spectroscopy. The two optical parameters showed a good correlation with the degree of cross-linking of cross-linked polyethylene (PE-X) and the degree of curing of different thermosets and adhesives, each of which was determined using different reference methods (wet chemical analysis, differential scanning calorimetry (DSC), and dielectric analysis (DEA)). The results show that different PE-X materials can be distinguished well by their absorption and scattering in the visual (VIS) and near-infrared (NIR) wavelength range, respectively, and conclusions on their degree of cross-linking are possible. Also, the curing of resins can be monitored based on the absorption. In addition, Raman spectroscopy was used to achieve a better understanding of the material changes during the cross-linking of the materials. It also showed a good suitability for monitoring the curing processes in thermosets. In summary, the new method can be used to determine the crucial parameters of these industrial important material types and fulfils the great demand for fast, non-destructive testing, which can be carried out during the process or on the finished product.

Compaction Quality Assurance Specifications of Unbound Materials

Compaction quality control/assurance of unbound geomaterials is one of the crucial components in pavement and embankment construction to ensure their performance, stability, and sustainability. Conventional density-based methods such as nuclear density gauge to determine the compaction quality have been widely used due to the straightforward relationship between the readings and targeted material property. Recent modifications in construction standards and the introduction of the Mechanistic-Empirical Pavement Design Guide have inspired a growing interest in developing and implementing strength/stiffness-based compaction control quality assurance (QA) specifications. Numerous studies have been dedicated to investigating the efficiency and effectiveness of the stiffness-based compaction QA tools. This paper presents a comprehensive review of the recent compaction QA relevant literature and surveys. Findings of different approaches for studying QA devices, and the main results of the existing models, experiments, and engineering practices were summarized. Several in situ spot QA technologies, including the latest compaction QA technologies [e.g., the lightweight deflectometer (LWD)], were highlighted, and their efficiency and effectiveness were compared. The review also summarized the intercorrelations between different devices, the correlations between in situ QA device readings and mechanical properties of unbound material, findings of the numerical simulations, and case studies and current practices using different QA tools. The recommendations for future research needs and practical implementations were identified and discussed.

Implementation of Sphinx/Lynx as daily QA equipment for scanned proton and carbon ion beams.

Reporting on the first implementation of a proton dedicated commercial device (IBA Sphinx/Lynx) for daily Quality Assurance (QA) of scanned proton and carbon ion beams. Daily QA trendlines over more than 3 years for protons and more than 2 years for carbon ions have been acquired. Key daily QA parameters were reviewed, namely the spot size and position, beam range, Bragg peak width, coincidence (between beam and imaging system isocenters), homogeneity and dose. The performance of the QA equipment for protons and carbon ions was evaluated. Daily QA trendlines allowed us to detect machine performance drifts and changes. The definition of tolerances and action levels is provided and compared with levels used in the literature. The device has been successfully implemented for routine daily QA activities in a dual particle therapy facility for more than 2 years. It improved the efficiency of daily QA and provides a comprehensive QA process.

Bioenergy Treatment for Improving Well-Being: A Meta-Analysis

Background: Bioenergy treatment devices for self-treatment with the aim to improve well-being are widely available, have become popular, and are used by a rather large number of persons. Yet, a systematic analysis of the assumed effect of these devices has not yet been conducted. We meta-analyzed eight very similar studies of the Healy device to assess the joint effect size. Method: Eight studies with similar designs, some active controlled and some wait-list controlled, testing the Healy bioenergy device, were meta-analyzed. They were conducted by the producer of the device for quality assurance and further development of the application. An additional literature search revealed no additional, independent studies. Result: The overall effect size across studies, combining all active arms and averaging outcome measures, is Hedge’s g = 0.757 (random effects model, I² = 85.8; z = 6.57; p < 0.0001). The stronger active intervention against control yields a heterogeneous g = 0.825 (random effects, I² = 82.5; z = 7.77; p < 0.0001). Active treatments against each other result in a significant g = 0.29 (fixed effects, I² = 0.0; z = 8.34; p < 0.0001). Discussion: The highest effect sizes are produced by a measure of coherence, followed by the WHO5 well-being questionnaire, the Perceived Stress Scale, with the Measure Your Own Medical Outcome Profile, resulting in the smallest effect size. Heterogeneity can be partially explained by the type of control, with active control producing smaller and wait-list control producing larger outcomes. Another source of heterogeneity is the sequencing of studies. Effect sizes grew for three studies, which were similar, and then fell and remained very similar for the rest of the studies. A limitation of this analysis is the fact that all studies were conducted by the R and D Department of the producer of the device. Conclusion: In this meta-analysis, the Healy device showed considerable effects, improving general well-being in healthy individuals. Nonetheless, an independent confirmation of these findings would be desirable. Moreover, the potential mechanisms of effect of the bioenergy device remain unclear, and further studies addressing this research question are warranted.

Dual-energy CT evaluation of 3D printed materials for radiotherapy applications

Objective. There is a continuous increase in 3D printing applications in several fields including medical imaging and radiotherapy. Although there are numerous advantages of using 3D printing for the development of customized phantoms, bolus, quality assurance devices and other clinical applications, material properties are not well known and printer settings can affect considerably the properties (e.g. density, isotropy and homogeneity) of the printed parts. This study aims to evaluate several materials and printer properties to identify a range of tissue-mimicking materials. Approach. Dual-energy CT was used to obtain the effective atomic number (Z eff) and relative electron density (RED) for thirty-one different materials including different colours of the same filament from the same manufacturer and the same type of filament from different manufacturers. In addition, a custom bone equivalent filament was developed and evaluated since a high-density filament with a composition similar to bone is not commercially available. Printing settings such as infill density, infill pattern, layer height and nozzle size were also evaluated. Main results. Large differences were observed for HU (288), RED (>10%) and Z eff (>50%) for different colours of the same filament due to the colour pigment. Results show a wide HU variation (−714 to 1104), RED (0.277 to 1.480) and Z eff (5.22 to 12.39) between the printed samples with some materials being comparable to commercial tissue-mimicking materials and good substitutes to a range of materials from lung to bone. Printer settings can result in directional dependency and significantly affect the homogeneity of the samples. Significance. The use of DECT to extract RED, and Z eff allows for quantitative imaging and dosimetry using 3D printed materials equivalent to certified tissue-mimicking tissues.

A novel Monte Carlo (MC) dose model for small MLC fields of the cyberknife® M6TM radiosurgery system using the EGSnrc.

The multi-leaf collimator (MLC)-equipped CyberKnife® M6 radiosurgery system (CKM6) (Accuray Inc., Sunnyvale, CA) has been increasingly employed for stereotactic radiosurgery (SRS) to treat relatively small lesions. However, achieving an accurate dose distribution in such cases is usually challenging due to the combination of numerous small fields≤(30×30)mm2 . In this study, we developed a new Monte Carlo (MC) dose model for the CKM6 system using the EGSnrc to investigate dose variations in the small fields. The dose model was verified for the static MLC fields ranging from (53.8×53.9) to (7.6×7.7) mm2 at 800mm source to axis distance in a water phantom, based on the computed doses of Accuray Precision® (Accuray Inc.) treatment planning system (TPS). We achieved a statistical uncertainty of ≤4% by simulating 30-50 million incident particles/histories. Then, the treatment plans were created for the same fields in the TPS, and the corresponding measurements were performed with MapCHECK2 (Sun Nuclear Corporation), a standard device for patient-specific quality assurance (PSQA). Results of the MC simulations, TPS, and MapCHECK2 measurements were inter-compared. An overall difference in dosimetric parameters such as profiles, tissue maximum ratio (TMR), and output factors (OF) between the MC simulations and the TPS results was found ≤3% for (53.8×53.9-15.4×15.4) mm2 MLC fields, and it rose to 4.5% for the smallest (7.6mm×7.7mm) MLC field. The MapCHECK2 results showed a deviation ranging from -1.5% to + 4.5% compared to the TPS results, whereas the deviation was within±2.5% compared with the MC results. Overall, our MC dose model for the CKM6 system showed better agreement with measurements and it could serve as a secondary dose verification tool for the patient-specific QA in small fields.

PHSOR11 Presentation Time: 1:20 PM: Verify the Transit Time Correction Accuracy of the Bravos Afterloader System Using a Novel Scintillation-Based Brachytherapy Quality Assurance Device

<h3>Purpose</h3> Compared to the older generations, the new Bravos high dose rate (HDR) afterloader offers the function to automatically correct dwell time to compensate the transit dose effect. To our best knowledge, there is no QA attempt to verify the accuracy of this correction. To address this issue, a new transit time measurement module has been developed and included in the OriQA HDR QA device, an autonomous phantom for HDR brachytherapy quality assurance. In this work, we employ the OriQA system to verify the transit time correction accuracy of the Bravos afterloader system. <h3>Method</h3> The OriQA device utilizes radioluminescence imaging technique to accurately measure HDR source strength, dwell time, and dwell position. It consists of a 20 cm needle applicator insert, a radioluminescence phosphor sheet placed directly atop the applicator, a digital camera, and software for signal processing and displaying results. Radiation-induced luminescence photons are emitted from the phosphor sheet and captured by the camera. The signal intensity and location are processed to yield relative source strength and dwell information. For the verification test, one of the Bravos channels was connected to the OriQA applicator using a one-meter transfer tube. After specific plan delivery, the raw data of OriQA measurement including source position and time was exported to Matlab for further analysis. The real dwell time at each dwell position and the transit time between dwells during cable extension and retraction were extracted. The transit time correction method provided by the vendor was applied to the measurement, yielding the delivered dwell time. The percentage difference between the delivered and planned dwell time was calculated and used as an indicator of the transit time correction accuracy. Several verification plans were created including seven with fixed dwell steps, one with variable dwell steps, and one with variable dwell time. Plans with fixed dwell steps were delivered three times. The rest were delivered once. Plan details are listed in table 1. For each plan, the mean and standard deviation of the difference between planned and delivered dwell time were calculated from all dwell positions and deliveries. <h3>Results</h3> The deviations between the planned and delivered dwell time are listed in table 1. For plans with less than 4 cm dwell step, the accuracy of transit time correction is, on average, less than 1.2% of the dwell time. For plans with 4 cm and 9 cm dwell step, the accuracy is 1.5% and 2.85%, on average, respectively. Dwell time variation does not affect the correction accuracy, as shown in plan 9. Standard deviations of plan 3, 4, and 9 are greater than 1% due to the relatively large difference at the proximal dwell. <h3>Conclusion</h3> This is the first study that successfully verifies the transit time correction accuracy of the Bravos system. Less than 2% accuracy is observed for clinically relevant dwell steps (0.3 cm to 4 cm). Variations in dwell step, dwell position, and dwell time do not worsen the accuracy.

Gamma Passing Rate – Correlation with Patient Specific Quality Assurance Devices using Two Photon energies in Pelvic IMRT

The effect on Gamma Passing Rate is studied by changing the Photon Energy in the Patient Specific Quality Assurancein Pelvic IMRT using EPID and MatriXX keeping PSQA device at Isocenter. Dose verification of 62 patients, sufferingfrom pelvic malignancies and treated with Intensity modulated radiation therapy (IMRT), with EPID and MatriXX usinggamma criteria of 3%/3 mm, 3%/2 mm, 2%/3 mm, 2%/2 mm and investigated the effect on Gamma Passing Rate (%GP) bychanging beam energy from 6 MV to 10 MV. The results demonstrated that the behavior of gamma passing rate decreases ascriteria is changed from 3%/3 mm to strict criteria. The mean gamma passing rate for 6 MV beam were (%GP±StandardDeviation σ) 99.64±0.81, 99.45±1.08, 97.57±2.12, 96.17±2.63 using the criteria 3%/3 mm, 3%/2 mm, 2%/3 mm, 2%/2 mmrespectively in EPID. For MatriXX, the mean %GP were 96.69±4.11, 93.85±5.31, 88.17±10.63, 82.2±12.28 respectively.For 10 MV, the mean (%GP±Std. Dev) were 99.64±0.81, 99.45±1.08, 97.57±2.12, 96.17±2.63 for in EPID, 96.69±4.11,93.85±5.31, 88.17±10.63, 82.2±12.28 for MatriXX respectively. Difference between %GP for 6 MV and 10 MV beam were-0.01, -0.11, 1.08, 1.61 with gamma criteria of 3%/3 mm, 3%/2 mm, 2%/3 mm, 2%/2 in EPID. For MatriXX, differencebetween %GP for 6 MV and 10 MV beam were -0.40, -0.24, 0.96, 1.62 respectively. It can be concluded that applying morestrict gamma criteria results in low gamma passing rate. There is marked difference in Gamma Passing Rate (%GP) withchange in photon energy.

Development and dosimetric evaluation of the IMRT prostate at outside-the-irradiated field in a heterogeneity male pelvis phantom

Abstract Background: Intensity-modulated radiation therapy (IMRT) treatment delivery requires pre-treatment patient-specific quality assurance (QA) for the dosimetry verification due to its complex multileaf-collimator movement. The prostate target close position between the bladder and rectum requires a tight margin during planning, and mistreatment would have a huge impact on the patient. A commercially available QA tool consists of a homogeneous medium and does not represent an exact photon interaction on the tumour and also on the nearby healthy organ. Objective: A heterogeneous male pelvis phantom was developed and investigated the efficiency of the treatment planning system (TPS) calculation on the off-axis region. Methods: Polymethyl methacrylate was used for the phantom housing, and the material closed to the bladder, rectum and prostate density was chosen to construct the organ models. The phantom was scanned and validated by the computed tomography number and density. An IMRT treatment was planned in the Monaco TPS, and a thermoluminescent dosimeter (TLD-100) was used to validate the point dosimetry. In addition, an EGSnrc Monte Carlo simulation was carried out to validate the phantom dosimetry. Results &amp; Discussion: The dose measurement between TLD-100, TPS, and EGSnrc was compared and validated in the pelvis phantom. In the prostate region, the dose difference was within ± 5%, and the maximum dose difference outside-the-irradiated field was up to 20·07 % and 47·31 % in TPS and TLD-100, respectively. Meanwhile, the measured dose was lower than the calculated dose, and it was apparent for the dose outside-the-irradiated field. Conclusion: The developed heterogeneity male pelvis phantom was validated and verified to be an important QA device for validating radiation dosimetry in the pelvis region. The dose outside-the-irradiated field was underestimated by both TPS and TLD, respectively.

Theoretical and experimental validation of the use of hydraulic load cells in fit-for-purpose assessment of structural bolt assemblies

ABSTRACT A hydraulic load cell is a simple onsite load measurement device for quality assurance of structural fasteners. While these load cells can be used to establish torque-tension relationship, due to their reduced stiffness compared to electronic load cells, prominent standards such as EN14399-2 prevents the use of hydraulic load cells in bolt assemblies testing where nut rotational angle is also of importance. Since the significant angular parameter used in EN14399-2 is a difference of two angles, it can be argued that when the difference of angle is considered, the reduced stiffness effect of hydraulic load cell could be negated. This paper provides both theoretical and experimental validation of using an electronic and a hydraulic load cell to carry out the fit-for-purpose assembly test as prescribed in EN14399-2. Results show that a hydraulic load cell can be used as a simple onsite screening test to improve quality assurance of structural bolt assemblies on construction sites. The Australian Standard for fastener assemblies AS/NZS 1252:2016 requires a test regime to ensure the supplied bolts are suitable for its intended application. The methodology developed in this paper maybe used to screen the quality of the supplied fasteners on-site before being used in the assembly.

Accountability and quality assurance for leadership and governance in Dubai-based educational marketplace

PurposeOver the past decades, there has been an intensifying movement to privatize education in Western nations, with equal concern about the quality of education for all. This article adds to a global understanding of school inspections as a governance mechanism to promote educational quality in an entirely open K-12 educational marketplace.Design/methodology/approachThe role of school inspections as a quality assurance device is examined from a market accountability perspective. The Emirate of Dubai is used as an illustrative example of market accountability, where the educational landscape constitutes primarily a private open market.FindingsDubai proves that market accountability can address the needs of all families, assuring the provision of a sufficient quality standard of education, while allowing for competition to drive improvement. There are two lessons that Dubai offers a global audience that has been debating the merits of privatizing education: a fully free unregulated market does not promote an education system that provides a minimum standard of education for all; and a private education system can address stakeholder concerns and operate successfully in parallel to a public sector.Originality/valueThe idiosyncratic United Arab Emirates (UAE) education sector calls for a balance between flexibility and quality assurance across semi-independent jurisdictions. Hosting a majority of non-Emirati resident families, Dubai has developed a public inspection system for a private education market for quality assurance across 17 curricula offered in 215 private schools with diverse profit models. That most Dubai school-aged children are in private schools demanded accommodating an atypical landscape for K-12 education that affords insights into how a free market can operate. The authors encourage future research that may build a more comprehensive framework for better understanding the public–private education debate.

Commissioning and routine quality assurance of the Radixact Synchrony system

The Radixact Synchrony system allows for target motion correction when tracking either fiducials in/around the target or a dense lesion in the lung. As such evaluation testing and quality assurance (QA) tests are required. To allow for QA procedures to be performed with a range of available phantoms evaluation of the dosimetric delivery accuracy was performed for a range of motions, phantoms, and motion platforms. A Computerized Imaging Reference Systems, Incorporated (CIRS) 1D motion platform and Accuray Tomotherapy "Cheese" phantom was utilized to perform absolute dose and GafChromic EBT3 film measurements. A HexaMotion platform and Delta4 phantom were utilized to quantify the effects of 1D and 3D motions. Inter-device comparison was performed with the ArcCHECK and Delta4 phantoms and GafChromic EBT3 film, five patient plans were delivered to each phantom when static and with two different motion types both with and without Synchrony motion correction. A range of QA tests are described. A phantom was designed to allow for daily verification of system functionality. This test allows for the detection of either fiducials or a dense silicone target with a stationary phantom. Monthly testing procedures are described that allow the user to verify the dosimetric improvement when utilizing synchrony delivery motion compensation versus uncorrected motions. These can be performed utilizing a 1D motion stage with an ion-chamber and GafChromic EBT3 film to allow for a 2D dosimetric validation. Alternatively, a 3D motion platform can be utilized where available. Monthly and annual imaging tests are described. Finally, annual test procedures designed to verify the coincidence of the imaging system and treatment isocenter are described. The evaluation of the Synchrony system using a range of QA devices shows consistently high dosimetric accuracy with similar trends in passing criteria found with GafChromic EBT3 film, ArcCHECK, and Delta4 phantoms for density-based respiratory model compensation. These results highlight the large improvements in the dose distribution when motion is accounted for with the Synchrony system as measured with a range of phantoms and motion platforms that the majority of users will have available. The testing methods and QA procedures described provide guidance for new users of the Radixact Synchrony system as they implement their own QA programs for this system, until such time as an AAPM task group report is made available. QA procedures including Kilovolts (kV) imaging quality metrics and imaging dose parameters, dose deposition accuracy, target detection coincidence, and target position detection accuracy are described.

Technical Note: Long-term monitoring of diode sensitivity degradation induced by proton irradiation.

To measure diode sensitivity degradation (DSD) induced by cumulative proton dose delivered to a commercial daily quality assurance (QA) device. At our institution, six Daily QA 3 (DQA3, Sun Nuclear Corporation, Melbourne, FL, USA) devices have been used for daily proton pencil beam scanning QA in four proton gantry rooms over a span of 4 years. DQA3 diode counts were cross-calibrated using a homogenous field with a known dose of 1Gy. The DSD rate (ΔR%/100Gy) was calculated using linear regression on time-series plots of diode counts and an estimate of cumulative dose per year based on the cross-calibration. The effect of DSD on daily QA spot position measurements was quantified by converting DSD to baseline spot position shift. The average dose delivered to the four inner DQA3 diodes was 104±5Gy/year, and the rate of DSD was -5.1%±1.0/100Gy with the exception of one DQA3 device that had a significantly higher rate of DSD (-12%/100Gy). The R2 s of the linear fit to time-series plots were between 0.92 and 0.98. The DSD rates were not constant but decreases with accumulated doses. The four center diodes, which received 40% of the cumulative dose received by inner diodes, had a DSD rate of -7.2%±0.9/100Gy. For our daily QA program, 1 year of DSD was equivalent to a 0.2mm shift in spot position. The DSD rate of DQA3 diodes determined by long-term proton daily QA data was about -5%/100Gy, which is more than 10 times greater than the reported DSD rate from photon irradiation. DQA3 diodes may be used for daily proton QA programs, provided that they are recalibrated at an appropriate frequency that should be determined specifically for different daily QA programs.