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BACKGROUND: Electromagnetic transponders bronchoscopically implanted near the tumor can be used to monitor deep inspiration breath hold (DIBH) for thoracic radiation therapy (RT). The feasibility and safety of this approach require further study. METHODS: We enrolled patients with primary lung cancer or lung metastases. Three transponders were implanted near the tumor, followed by simulation with DIBH, free breathing, and 4D-CT as backup. The initial gating window for treatment was ±5 mm; in a second cohort, the window was incrementally reduced to determine the smallest feasible gating window. The primary endpoint was feasibility, defined as completion of RT using transponder-guided DIBH. Patients were followed for assessment of transponder- and RT-related toxicity. RESULTS: We enrolled 48 patients (35 with primary lung cancer and 13 with lung metastases). The median distance of transponders to tumor was 1.6 cm (IQR 0.6-2.8 cm). RT delivery ranged from 3 to 35 fractions. Transponder-guided DIBH was feasible in all but two patients (96% feasible), where it failed because the distance between the transponders and the antenna was >19 cm. Among the remaining 46 patients, 6 were treated prone to keep the transponders within 19 cm of the antenna, and 40 were treated supine. The smallest feasible gating window was identified as ±3 mm. Thirty-nine (85%) patients completed one year of follow-up. Toxicities at least possibly related to transponders or the implantation procedure were grade 2 in six patients (six incidences, cough and hemoptysis), grade 3 in three patients (five incidences, cough, dyspnea, pneumonia, and supraventricular tachycardia), and grade 4 pneumonia in one patient (occurring a few days after implantation but recovered fully and completed RT). Toxicities at least possibly related to RT were grade 2 in 18 patients (41 incidences, most commonly cough, fatigue, and pneumonitis) and grade 3 in four patients (seven incidences, most commonly pneumonia), and no patients had grade 4 or higher toxicity. CONCLUSIONS: Bronchoscopically implanted electromagnetic transponder-guided DIBH lung RT is feasible and safe, allowing for precise tumor targeting and reduced normal tissue exposure. Transponder-antenna distance was the most common challenge due to a limited antenna range, which could sometimes be circumvented by prone positioning.
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PURPOSE: To predict the necessity of enteral nutrition at 28 days after surgery in patients undergoing major head and neck oncologic procedures for oral and oropharyngeal cancers. MATERIAL AND METHODS: Data from 193 patients with oral cavity and oropharyngeal squamous cell carcinoma were retrospectively collected at two tertiary referral centers to train (n = 135) and validate (n = 58) six supervised machine learning (ML) models for binary prediction employing 29 clinical variables available pre-operatively. RESULTS: The accuracy of the six ML models ranged between 0.74 and 0.88, while the measured area under the curve (AUC) between 0.75 and 0.87. The ML algorithms showed high specificity (range 0.87-0.96) and moderate sensitivity (range: 0.31-0.77) in detecting patients with ≥28 days feeding tube dependence. Negative predictive value was higher (range: 0.81-0.93) compared to positive predictive value (range: 0.40-0.71). Finally, the F1 score ranged between 0.35 and 0.74. CONCLUSIONS: Classification performance of the ML algorithms showed optimistic accuracy in the prediction of enteral nutrition at 28 days after surgery. Prospective studies are mandatory to define the clinical benefit of a ML-based pre-operative prediction of a personalized nutrition protocol.
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Neoplasias de Cabeza y Cuello , Neoplasias Orofaríngeas , Humanos , Estudios Retrospectivos , Estudios Prospectivos , Neoplasias Orofaríngeas/cirugía , Aprendizaje AutomáticoRESUMEN
BACKGROUND: To elaborate a preoperative score to predict the necessity of enteral nutrition at 28 days postoperatively in patients undergoing head and neck surgery. METHODS: A total of 424 patients with oral cavity, oropharyngeal, laryngeal, and hypopharyngeal carcinoma were retrospectively enrolled and analyzed to identify preoperative predictors of prolonged postsurgical enteral feeding which were used to create a prediction model with an easy-to-use nomogram. RESULTS: Five preoperative variables (body mass index, previous radiotherapy, preoperative dysphagia, type of surgery, flap reconstruction) were found to be independent predictive factors and were used to create a prediction model named PEG score together with the related nomogram. Accuracy, F1, and the area under the curve (AUC) were 0.74, 0.83, and 0.74. Different decision thresholds can be used to vary the sensitivity and specificity. CONCLUSIONS: The PEG score showed high prediction performances for modeling the need for enteral nutrition at 28 days postoperatively. Prospective studies are needed to define a personalized nutrition protocol.
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Gastrostomía , Neoplasias de Cabeza y Cuello , Humanos , Gastrostomía/métodos , Estudios Retrospectivos , Nutrición Enteral/métodos , Estado Nutricional , Neoplasias de Cabeza y Cuello/cirugíaRESUMEN
Human group size seemingly has no limit, with many individuals living alongside thousands - even millions - of others. Non-human primate groups, on the other hand, cannot be sustained past a certain, relatively small size. I propose that Pascal Boyer's model of ownership psychology may offer an explanation for such a significant divergence.
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Propiedad , HumanosRESUMEN
Life cycle assessment (LCA) is a modelling technique used to determine the cradle-to-grave environmental and human health impacts from the production of a good or the provision of a service. Radiological protection may benefit from employing tools like LCA to obtain a broader perspective and enable comparison with analyses of non-radiological systems. Despite structural similarities to other well-established decision-aiding techniques (DATs), the impact assessment within LCA (i.e. LCIA) is not commonly used in the optimisation of radiological protection process. This paper provides a brief review of LCA, including LCIA, along with more traditional DATs (such as multi-attribute utility analysis) used in the optimisation process for comparison. Basic concrete shielding was considered as a simple, illustrative example; concrete attenuates emissions from a radiation source but is also associated with a financial cost as well as costs with respect to energy, material, and water use. LCA offers quantification of these and other key resources (termed 'impact categories'). Ultimately, we offer that, depending on the circumstance, LCA can be a useful tool in radiological protection decision-making, complementing existing techniques.
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Protección Radiológica , Humanos , Animales , Agua , Estadios del Ciclo de VidaRESUMEN
BACKGROUND: Residents in residential aged care facilities (RACFs) have a high number of medication-related problems. Integrating on-site pharmacists (OSPs) into this setting is a possible solution and is currently gaining traction in Australia and internationally. The Pharmacists in Residential Aged Care Facilities (PiRACF) cluster-randomised controlled trial integrated pharmacists into the RACF care team to improve medication management. The aim of this descriptive observational study is to explore the activities of OSPs when they are integrated into multidisciplinary care team in RACFs. METHOD: An online survey tool was developed to record the activities of OSPs in RACFs using the Qualtrics© software. OSPs were asked questions about their activities in RACFs under categories that included description, time spent, outcomes where applicable and who the pharmacists communicated with to undertake the activity. RESULTS: Six pharmacists were integrated into 7 RACFs. Overall, they recorded 4252 activities over 12 months. OSPs conducted 1022 (24.0%) clinical medication reviews; 48.8% of medication reviews identified and discussed potentially inappropriate medications with prescribers and 1025 other recommendations were made to prescribers. Overall, the prescriber accepted 51.5% of all recommendations made by OSPs. The most frequently accepted outcome was deprescribing of medications (47.5% for potentially inappropriate medications and 55.5% for other recommendations). OSPs performed facility-level activities including staff education (13.4%), clinical audits (5.8%), and quality improvement activities (9.4%). OSPs spent a large proportion of their time communicating (23.4%) extensively with prescribers, RACF's healthcare team, and residents. CONCLUSION: OSPs successfully performed a wide range of clinical activities aimed both at improving residents' medication regimens, and organisational-level quality improvement. The OSP model presents an opportunity for pharmacists to enhance medication management in the residential aged care setting. Trial registration The trial was registered with the Australian New Zealand Clinical Trials Registry (ANZCTR) (ACTRN: ACTRN12620000430932) on April 1, 2020.
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Geologic carbon storage currently implies that CO2 is injected into reservoirs more than 1 km deep, but this concept of geologic storage can be expanded to include the injection of solid, carbon-bearing particles into geologic formations that are one to two orders of magnitude shallower than conventional storage reservoirs. Wood is half carbon, available in large quantities at a modest cost, and can be milled into particles and injected as a slurry. We demonstrate the feasibility of shallow geologic storage of carbon by a field experiment, and the injection process also raises the ground surface. The resulting CO2 storage and ground uplift rates upscale to a technique that could contribute to the mitigation of climate change by storing carbon as well as helping to adapt to flooding risks by elevating the ground surface above flood levels. A life-cycle assessment indicates that CO2 emissions caused by shallow geologic storage of carbon are a small fraction of the injected carbon.
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Dióxido de Carbono , Carbono , Inundaciones , Cambio ClimáticoRESUMEN
Residents of socioeconomically disadvantaged neighbourhoods have higher rates of overweight and obesity and chronic disease than their counterparts from advantaged neighbourhoods. This study assessed whether associations between neighbourhood disadvantage and measured body mass index (BMI) and waist circumference, are accounted for by obesogenic environments (i.e., residential distance to the Central Business District [CBD], supermarket availability, access to walkable destinations). The study used 2017-18 National Health Survey data for working-aged adults (aged ≥18 years, n = 9,367) residing in 3,454 neighbourhoods across Australia's state and territory capital cities. In five of eight cities (i.e., Sydney, Melbourne, Brisbane, Adelaide, and Perth) residents of disadvantaged neighbourhoods had significantly higher BMI and a larger waist circumference than residents of more advantaged areas. There was no association between neighbourhood disadvantage and body size in Hobart, Darwin, and Canberra. Associations between neighbourhood disadvantage and body size were partially explained by neighbourhood differences in distance to the CBD but not supermarket availability or walkable amenities. The results of this study point to the role of urban design and city planning as mechanisms for addressing social and economic inequities in Australia's capital cities, and as solutions to this country's overweight and obesity epidemic and associated rising rates of chronic disease.
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Sobrepeso , Disparidades Socioeconómicas en Salud , Adulto , Humanos , Adolescente , Persona de Mediana Edad , Ciudades , Factores Socioeconómicos , Tamaño Corporal , Características de la Residencia , Obesidad/epidemiología , Características del Vecindario , Australia/epidemiologíaRESUMEN
PURPOSE: To explore if and how Parkinson's disease dance class participation and public performance contributes to perceptions of wellbeing. MATERIALS AND METHODS: A qualitative design using audio-recorded one-on-one semi-structured interviews with five class participants and three teachers/volunteers from two metropolitan Dance for Wellbeing class locations. Data were inductively thematically analysed by three researchers. RESULTS: Five themes illustrated the experience of dance class and performance for people with Parkinson's Disease: 1) 'the enabling learning environment'; 2) 'physical benefits from class participation; 3) 'mental/psychological benefits from class participation'; 4) 'social benefits from class participation; 5) 'sense of self and life engagement from class participation'. Themes 4 and 5 in particular were considered to be 'magnified by public performance', providing an opportunity for solidarity within the group and a supportive avenue for "coming out" and living publicly with the PD diagnosis. CONCLUSION: Dance performance magnifies health and wellbeing experiences of people with Parkinson's disease when part of an enabling, inclusive and emotionally and physically safe learning dance class environment. Elements of holistic benefits, as well as the fun and playful nature of the experience may be important elements to consider for motivation, recruitment and retention in this population.IMPLICATIONS FOR REHABILITATIONRehabilitation professionals should consider the use of dance class as an art-based activity that has a holistic therapeutic benefit.Flexible and fun environments are constructive for dancers to sustain attendance and interest.Rehabilitation professionals can be cognisant of the impact of public dance performance as 'coming out' with Parkinson's Disease.
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Danzaterapia , Enfermedad de Parkinson , Humanos , Enfermedad de Parkinson/rehabilitación , Investigación Cualitativa , VoluntariosRESUMEN
Humans have long dreamed of traveling to space. In response to the recent increase in commercial space flight, this paper evaluates environmental impacts of human space travel, both past and present, to shed light on the large environmental footprint of such activities. This environmental impact also has a moral component, since most of the global population will never be able to participate in such activities, yet still must bear the cost. Ironically, instead of a space future acting as a relief valve on Earth's resources, few activities exact a heavier burden on our planet's resources than the space pursuit, for the number of people it serves. This analysis utilized the structure of life cycle assessment. Data on launch vehicles mass and propellant type and mass was taken from public sources. Combustion emission results were calculated using combustion analysis software. These data were then combined with data from life cycle inventory databases and impact assessment methods to evaluate midpoint impact indicators. The hourly impact from sustaining humans in space over 1500 kg CO2-eq per hour. To put this into context, this is 2000 times greater than the emission rate of the average person on the globe, which we term global citizen equivalents (GCE). This global warming impact is also 650 times greater than the average person in the U.S. In terms of familiar activities, this is equivalent to continuously supplying at least 4 MW of electricity from the U.S. grid; simultaneously driving over sixty diesel buses; or occupying twenty seats on a Boeing 747 that never lands. Clearly such impacts raise questions not only to the sustainability of such activities, but also to the moral and ethical implications where such travel is limited to only the very wealthiest, but the costs are borne by all with few benefits to show from the endeavour.
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Vehículos a Motor , Vuelo Espacial , Humanos , Calentamiento Global , Ambiente , Principios MoralesRESUMEN
The causal premise of the evolutionary debunking argument contends that human moral beliefs are explained by the process of natural selection. While it is universally acknowledged that such a premise is fundamental to the debunker's case, the vast majority of philosophers focus instead on the epistemic premise that natural selection does not track moral truth and the resulting skeptical conclusion(s). Recently, however, some have begun to concentrate on the causal premise. So far, the upshot of this small but growing literature has been that the causal premise is likely false due to the seemingly persuasive evidence that our moral beliefs are in fact not the result of natural selection. In this paper, I argue that this view is mistaken. Specifically, I advocate the Innate Biases Model, which contends that there is not only compelling evidence for an evolved cognitive capacity for acquiring norms but also for the existence of an evolutionarily instilled set of cognitive biases that make it either more or less likely that we adopt certain moral beliefs.
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Principios Morales , HumanosRESUMEN
BACKGROUND: Most people who suffer an anterior cruciate ligament (ACL) injury search for information online. OBJECTIVES: Summarise the proportion of webpages on ACL rupture management that present evidence-based information. DESIGN: Content analysis. METHODS: We examined webpage information on ACL ruptures identified through (1) Google searches using terms synonymous with 'anterior cruciate ligament rupture' and searching 'knee surgeon' linked to each Australian capital city, and (2) websites of professional associations. The primary outcome was the proportion of webpages that suggest people can return to at least some form of sport with non-surgical management. Secondary outcomes included webpage information on return to sport with ACL reconstruction (ACLR) and non-surgical management, benefits, harms, and risk of osteoarthritis related to these options, and activity modification. RESULTS: Out of 115 webpages analysed, 48% suggested people can return to at least some form of sport with non-surgical management. Almost half of webpages suggested most people will return to some form of sport following ACLR (41%) and mentioned benefits of ACLR (43%). Fewer webpages mentioned benefits of non-surgical management (14%), approximately two in three people return to pre-injury level of sport following ACLR (4%), risk of re-injury following ACLR (23%), most people return to sport within 9 months of ACLR (27%), activity modification as a management approach (20%), and ACLR will reduce the risk of osteoarthritis (23%). CONCLUSION: Most online information on ACL rupture management isn't aligned with the best available evidence. Inaccurate information could mislead patients' treatment choices and create unrealistic expectations for return to sport.
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Lesiones del Ligamento Cruzado Anterior , Osteoartritis , Ligamento Cruzado Anterior , Lesiones del Ligamento Cruzado Anterior/cirugía , Australia , Humanos , Volver al DeporteRESUMEN
This commentary characterises as an insurgency those elements of the Food Industry seeking to retain and expand industry profit-making opportunity with scant regard to the effect on public health and wellbeing. Premised on a conflict in which the battlespace encompasses the drivers of (un)healthful behaviour, our view encourages opponents of Food Industry methods to consider an approach based on analogy of successful Counter-Insurgency strategies to a health promotion context.
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Industria de Alimentos , Salud Pública , Alimentos , Promoción de la Salud , HumanosRESUMEN
Critical metals, identified from supply, demand, imports, and market factors, include rare earth elements (REE), platinum group metals, precious metals, and other valuable metals such as lithium, cobalt, nickel, and uranium. Extraction of metals from U.S. saline aqueous, emphasizing saline, sources is explored as an alternative to hardrock ore mining. Potential aqueous sources include seawater, desalination brines, oil-and-gas produced waters, geothermal aquifers, and acid mine drainage, among others. A feasibility assessment reveals opportunities for recovery of lithium, strontium, magnesium, and several REE from select sources, in quantities significant for U.S. manufacturing and for reduction of U.S. reliance on international supply chains. This is a conservative assessment given that water quality data are lacking for a significant number of critical metals in certain sources. The technology landscape for extraction and recovery of critical metals from aqueous sources is explored, identifying relevant processes along with knowledge gaps. Our analysis indicates that aqueous mining would result in much lower environmental impacts on water, air, and land than ore mining. Preliminary assessments of the economics and energy consumption of recovery show potential for recovery of critical metals.
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INTRODUCTION: Paraspinal stereotactic body radiotherapy (SBRT) involves risks of severe complications. We evaluated the safety of the paraspinal SBRT program in a large academic hospital by applying failure modes and effects analysis. METHODS: The analysis was conducted by a multidisciplinary committee (two therapists, one dosimetrist, four physicists, and two radiation oncologists). The paraspinal SBRT workflow was segmented into four phases (simulation, treatment planning, delivery, and machine quality assurance (QA)). Each phase was further divided into a sequence of sub-processes. Potential failure modes (PFM) were identified from each subprocess and scored in terms of the frequency of occurrence, severity and detectability, and a risk priority number (RPN). High-risk PFMs were identified based on RPN and were studied for root causes using fault tree analysis. RESULTS: Our paraspinal SBRT process was characterized by eight simulations, 11 treatment planning, nine delivery, and two machine QA sub-processes. There were 18, 29, 19, and eight PFMs identified from simulation, planning, treatment, and machine QA, respectively. The median RPN of the PFMs was 62.9 for simulation, 68.3 for planning, 52.9 for delivery, and 22.0 for machine QA. The three PFMs with the highest RPN were: previous radiotherapy outside the institution is not accurately evaluated (RPN: 293.3), incorrect registration between diagnostic magnetic resonance imaging and simulation computed tomography causing incorrect contours (273.0), and undetected patient movement before ExacTrac baseline (217.8). Remedies to the high RPN failures were implemented, including staff education, standardized magnetic resonance imaging acquisition parameters, and an image fusion process, and additional QA on beam steering. CONCLUSIONS: A paraspinal SBRT workflow in a large clinic was evaluated using a multidisciplinary and systematic risk analysis, which led to feasible solutions to key root causes. Treatment planning was a major source of PFMs that systematically affect the safety and quality of treatments. Accurate evaluation of external treatment records remains a challenge.
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Análisis de Modo y Efecto de Fallas en la Atención de la Salud , Radiocirugia , Humanos , Aceleradores de Partículas , Planificación de la Radioterapia Asistida por Computador , Medición de RiesgoRESUMEN
Managing TG-51 reference dosimetry in a large hospital network can be a challenging task. The objectives of this study are to investigate the effectiveness of using Statistical Process Control (SPC) to manage TG-51 workflow in such a network. All the sites in the network performed the annual reference dosimetry in water according to TG-51. These data were used to cross-calibrate the same ion chambers in plastic phantoms for monthly QA output measurements. An energy-specific dimensionless beam quality cross-calibration factor, k q n S W , was derived to monitor the process across multiple sites. The SPC analysis was then performed to obtain the mean, ã k q n S W ã , standard deviation, σ k , the Upper Control Limit (UCL) and Lower Control Limit (LCL) in each beam. This process was first applied to 15 years of historical data at the main campus to assess the effectiveness of the process. A two-year prospective study including all 30 linear accelerators spread over the main campus and seven satellites in the network followed. The ranges of the control limits (±3σ) were found to be in the range of 1.7% - 2.6% and 3.3% - 4.2% for the main campus and the satellite sites respectively. The wider range in the satellite sites was attributed to variations in the workflow. Standardization of workflow was also found to be effective in narrowing the control limits. The SPC is effective in identifying variations in the workflow and was shown to be an effective tool in managing large network reference dosimetry.
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OBJECTIVE: Adaptive radiation therapy (ART) is an integral part of MR-guided RT (MRgRT), requiring a new RT plan for each treatment fraction and resulting in a significant increase in patient-specific quality assurance (PSQA). This study investigates the possibility of using treatment log-file for automated PSQA. METHOD: All treatment plans were delivered in 1.5T Unity MR-Linac (Elekta). A Unity compatible version of LinacView (Standard Imaging) was commissioned to automatically monitor and analyze the log-files. A total of 220 fields were delivered and measured by ArcCheck® -MR (Sun Nuclear) and LinacView. Thirty incorrectly matched fields were also delivered to check for error detection sensitivity. The gamma analysis, γ, with 3%, 3 mm criteria was used in both ArcCheck® -MR and LinacView. Additionally, the gantry angle, jaws, and multileaf collimators (MLC) positions reported in the log-file were compared with plan positions using TG-142 criteria. RESULT: The γ (3%, 3 mm) for the 190 plans were found to be between the range of 72.5%-100.0% and 95.4%-100.0% for ArcCheck® -MR and LinacVeiw, respectively. All the delivered gantry angle and jaws were found to be within 0.2° and 2 mm. MLCs that were outside the guard leaves or under the diaphragms were found to have more than 1.0 mm discrepancy. This was attributed to the linac internal override for these MLCs and had no dosimetric impact. Excluding these discrepancies, all MLC positions were found to be within 1.0 mm. The γ (3%, 3 mm) for the 30 incorrectly matched fields were found to be 3.9%-84.8% and 0.1%-64.4% for ArcCheck® -MR and LinacVeiw, respectively. CONCLUSION: Significant ranked correlation demonstrates the automated log-file analysis can be used for PSQA and expedite the ART workflow. Ongoing PSQA will be compared with log-file analysis to investigate the longer term reproducibility and correlation.
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Radioterapia de Intensidad Modulada , Humanos , Aceleradores de Partículas , Fantasmas de Imagen , Garantía de la Calidad de Atención de Salud , Dosificación Radioterapéutica , Planificación de la Radioterapia Asistida por Computador , Reproducibilidad de los ResultadosRESUMEN
PURPOSE: This study aimed to evaluate and compare different system calibration methods from a large cohort of systems to establish a commissioning procedure for surface-guided frameless cranial stereotactic radiosurgery (SRS) with intrafractional motion monitoring and gating. Using optical surface imaging (OSI) to guide non-coplanar SRS treatments, the determination of OSI couch-angle dependency, baseline drift, and gated-delivered-dose equivalency are essential. METHODS: Eleven trained physicists evaluated 17 OSI systems at nine clinical centers within our institution. Three calibration methods were examined, including 1-level (2D), 2-level plate (3D) calibration for both surface image reconstruction and isocenter determination, and cube phantom calibration to assess OSI-megavoltage (MV) isocenter concordance. After each calibration, a couch-angle dependency error was measured as the maximum registration error within the couch rotation range. A head phantom was immobilized on the treatment couch and the isocenter was set in the middle of the brain, marked with the room lasers. An on-site reference image was acquired at couch zero, the facial region of interest (ROI) was defined, and static verification images were captured every 10° for 0°-90° and 360°-270°. The baseline drift was assessed with real-time monitoring of the motionless phantom over 20 min. The gated-delivered-dose equivalency was assessed using the electron portal imaging device and gamma test (1%/1mm) in reference to non-gated delivery. RESULTS: The maximum couch-angle dependency error occurs in longitudinal and lateral directions and is reduced significantly (P < 0.05) from 1-level (1.3 ± 0.4 mm) to 2-level (0.8 ± 0.3 mm) calibration. The MV cube calibration does not further reduce the couch-angle dependency error (0.8 ± 0.2 mm) on average. The baseline drift error plateaus at 0.3 ± 0.1 mm after 10 min. The gated-delivered-dose equivalency has a >98% gamma-test passing rate. CONCLUSION: A commissioning method is recommended using the 3D plate calibration, which is verified by radiation isocenter and validated with couch-angle dependency, baseline drift, and gated-delivered-dose equivalency tests. This method characterizes OSI uncertainties, ensuring motion-monitoring accuracy for SRS treatments.
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Radiocirugia , Humanos , Posicionamiento del Paciente , Fantasmas de Imagen , Dosificación Radioterapéutica , CráneoRESUMEN
The use of trajectory log files for routine patient quality assurance is gaining acceptance. Such use requires the validation of the trajectory log itself. However, the accurate localization of a multileaf collimator (MLC) leaf while it is in motion remains a challenging task. We propose an efficient phantom-less technique using the EPID to verify the dynamic MLC positions with high accuracy. Measurements were made on four Varian TrueBeams equipped with M120 MLCs. Two machines were equipped with the S1000 EPID; two were equipped with the S1200 EPID. All EPIDs were geometrically corrected prior to measurements. Dosimetry mode EPID measurements were captured by a frame grabber card directly linked to the linac. All leaf position measurements were corrected both temporally and geometrically. The readout latency of each panel, as a function of pixel row, was determined using a 40 × 1.0 cm2 sliding window (SW) field moving at 2.5 cm/s orthogonal to the row readout direction. The latency of each panel type was determined by averaging the results of two panels of the same type. Geometric correction was achieved by computing leaf positions with respect to the projected isocenter position as a function of gantry angle. This was determined by averaging the central axis position of fields at two collimator positions of 90° and 270°. The radiological to physical leaf end position was determined by comparison of the measured gap with that determined using a feeler gauge. The radiological to physical leaf position difference was found to be 0.1 mm. With geometric and latency correction, the proposed method was found to be improve the ability to detect dynamic MLC positions from 1.0 to 0.2 mm for all leaves. Latency and panel residual geometric error correction improve EPID-based MLC position measurement. These improvements provide for the first time a trajectory log QA procedure.
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Aceleradores de Partículas , Radioterapia de Intensidad Modulada , Humanos , Fantasmas de Imagen , RadiometríaRESUMEN
BACKGROUND: Residential environment features such as availability of supermarkets may shape dietary behaviour and thus overweight and obesity. This relationship may not be consistent between cities. This Australian national-level study examined: 1) the relationship between supermarket availability and body size; and 2) whether this relationship varied by capital city. METHODS: This study used 2017-18 Australian National Health Survey data including individual-level socio-demographic information (age, sex, country of birth, education, occupation, household income), and measured body size (height and weight to derive body mass index [BMI], and waist circumference [WC]). Objectively-expressed measures of residential environments included: counts of supermarkets (major chain outlets), counts of amenities (representing walkable destinations including essential services, recreation, and entertainment), and area of public open space - each expressed within road-network buffers at 1000 m and 1500 m; population density (1km2 grid cells); and neighbourhood disadvantage (Index of Relative Socioeconomic Disadvantage) expressed within Statistical Area Level 1 units. Data for adult respondents ≥18 years residing in each of Australia's state and territory capital cities (n = 9649) were used in multilevel models to estimate associations between supermarket availability and body size sequentially accounting for individual and other environment measures. An interaction term estimated city-specific differences in associations between supermarket availability and body size. Models were consequently repeated stratified by city. RESULTS: Body size (BMI and WC) and supermarket availability varied between cities. Initial inverse associations between supermarket availability and body size (BMI and WC) were attenuated to null with inclusion of all covariates, except for BMI in the 1000 m buffer model (beta = - 0.148, 95%CI -0.27, - 0.01, p = 0.025). In stratified analyses, the strengths of associations varied between cities, remaining statistically significant only for some cities (BMI: Melbourne, Brisbane Hobart; WC: Brisbane, Hobart) in fully adjusted models. Different patterns of attenuation of associations with inclusion of covariates were evident for different cities. CONCLUSIONS: For Australian capital cities, greater availability of supermarkets is associated with healthful body size. Marked between-city variations in body size, supermarket availability, and relationships between supermarket availability and body size do not, however, support universal, "one-size-fits-all" solutions to change built environments to support healthful body size.