Monitoring daily MLC positional errors using trajectory log files and EPID measurements for IMRT and VMAT deliveries

This work investigated the differences between multileaf collimator (MLC) positioning accuracy determined using either log files or electronic portal imaging devices (EPID) and then assessed the possibility of reducing patient specific quality control (QC) via phantom-less methodologies. In-house software was developed, and validated, to track MLC positional accuracy with the rotational and static gantry picket fence tests using an integrated electronic portal image. This software was used to monitor MLC daily performance over a 1 year period for two Varian TrueBeam linear accelerators, with the results directly compared with MLC positions determined using leaf trajectory log files. This software was validated by introducing known shifts and collimator errors. Skewness of the MLCs was found to be 0.03 ± 0.06° (mean ±1 standard deviation (SD)) and was dependent on whether the collimator was rotated manually or automatically. Trajectory log files, analysed using in-house software, showed average MLC positioning errors with a magnitude of 0.004 ± 0.003 mm (rotational) and 0.004 ± 0.011 mm (static) across two TrueBeam units over 1 year (mean ±1 SD). These ranges, as indicated by the SD, were lower than the related average MLC positioning errors of 0.000 ± 0.025 mm (rotational) and 0.000 ± 0.039 mm (static) that were obtained using the in-house EPID based software. The range of EPID measured MLC positional errors was larger due to the inherent uncertainties of the procedure. Over the duration of the study, multiple MLC positional errors were detected using the EPID based software but these same errors were not detected using the trajectory log files. This work shows the importance of increasing linac specific QC when phantom-less methodologies, such as the use of log files, are used to reduce patient specific QC. Tolerances of 0.25 mm have been created for the MLC positional errors using the EPID-based automated picket fence test. The software allows diagnosis of any specific leaf that needs repair and gives an indication as to the course of action that is required.

Facilities management: Tracing its development trajectory

Purpose – The purpose of this paper is to provide facilities management (FM) practitioners and researchers with a better understanding of the FM industry sector by analyzing the trend of its development.
Design/methodology/approach – Semi-structured interview is adopted in this research as the main methodology. In total, 30 FM professionals in the UK were interviewed to explore the past, present and future of FM. The analysis of interview results helps to identify the key areas in which FM has changed, is changing and will change. It also helps to explain the implications of FM development in each key area.
Findings – FM evolves and matures continuously. It is important for FM organizations and practitioners to recognize the dynamic nature of this industry sector, based on which they can develop appropriate strategies to adapt to changing circumstances. This is probably the only way for them to
keep pace with the times.
Originality/value – Both backward looking and forward looking are crucial to the development of an industry sector. However, existing studies on FM development are conducted through either review or outlook. On the other hand, most of these studies focus on one particular management area or one particular industry sector. Based on 30 expert interviews, this research attempts to bridge the knowledge gap and analyze the trend of FM development in a systematic way. A better understanding of the trend provides a possibility and a guide for FM organizations and practitioners to pursue best practice.

The validity of classical trajectory and perturbative quantal methods for electron-impact ionization from excited states in H-like ions

To test the validity of classical trajectory and perturbative quantal methods for electron-impact ionization of H-like ions from excited states, we have performed advanced close-coupling calculations of ionization from excited states in H, Li 2+ and B 4+ using the R -matrix with pseudo states and the time-dependent close-coupling methods. Comparisons with our classical trajectory Monte Carlo (CTMC) and distorted-wave (DW) calculations show that the CTMC method is more accurate than the DW method for H, but does not improve with n and grows substantially worse with Z , while the DW method improves with Z and grows worse with n .

Examining Ambrosia Pollen Episodes at Poznań (Poland) Using Back-trajectory Analysis

The pollen grains of Ambrosia spp. are considered to be important aeroallergens in parts of southern and central Europe. Back-trajectories have been analysed with the aim of finding the likely sources of Ambrosia pollen grains that arrived at Poznań (Poland). Temporal variations in Ambrosia pollen at Poznań from 1995–2005 were examined in order to identify Ambrosia pollen episodes suitable for further investigation using back-trajectory analysis. The trajectories were calculated using the transport model within the Lagrangian air pollution model, ACDEP (Atmospheric Chemistry and Deposition). Analysis identified two separate populations in Ambrosia pollen episodes, those that peaked in the early morning between 4 a.m. and 8 a.m., and those that peaked in the afternoon between 2 p.m. and 6 p.m.. Six Ambrosia pollen episodes between 2001 and 2005 were examined using backtrajectory analysis. The results showed that Ambrosia pollen episodes that peaked in the early morning usually arrived at Poznań from a southerly direction after passing over southern Poland, the Czech Republic, Slovakia and Hungary, whereas air masses that brought Ambrosia pollen to Poznań during the afternoon arrived from a more easterly direction and predominantly stayed within the borders of Poland. Back-trajectory analysis has shown that there is a possibility that long-range transport brings Ambrosia pollen to Poznań from southern Poland, the Czech Republic, Slovakia and Hungary. There is also a likelihood that Ambrosia is present in Poland, as shown by the arrival of pollen during the afternoon that originated primarily from within the country.

Examining High Magnitude Grass Pollen Episodes at Worcester, United Kingdom, Using Back-Trajectory Analysis

Trajectory analysis is a valuable tool that has been used before in aerobiological studies, to investigate the movement of airborne pollen. This study has employed back-trajectories to examine the four highest grass pollen episodes at Worcester, during the 2001 grass pollen season. The results have shown that the highest grass pollen counts of the 2001 season were reached when air masses arrived from a westerly direction. Back-trajectory analysis has a limited value to forecasters because the method is retrospective and cannot be employed directly for forecasting. However, when used in conjunction with meteorological data this technique can be used to examine high magnitude events in order to identify conditions that lead to high pollen counts.

Investigating Ambrosia Pollen Episodes in Poland Using Back-Trajectory Analysis

Background: The pollen grains of Ambrosia spp. are considered to be important aeroallergens. Previous studies have shown that the long-range transport of Ambrosia pollen to Poland is intermittent and mainly related to the passage of air masses over the Carpathian and Sudetes mountains from sources to the south, e.g. the Czech Republic, Slovakia and Hungary. In this study, Ambrosia pollen counts and back-trajectories from specific episodes in 1999 and 2002 have been analysed with the aim of identifying possible new sources of Ambrosia pollen arriving at three sites in Poland. Method: The combination of Ambrosia pollen measurements (daily average and bi-hourly concentrations) and air mass trajectory calculations were used to investigate two Ambrosia pollen episodes recorded at Rzeszow, Krakow and Poznań on the 4th and 5th September 1999 and 3rd September 2002. Ambrosia pollen counts were recorded by volumetric spore traps of the Hirst design. Trajectories were calculated using the transport model within the Lagrangian air pollution model, ACDEP (Atmospheric Chemistry and Deposition). Results: The collective results of pollen measurements and back-trajectory analysis indicate plumes of Ambrosia pollen travelling up through Poland from the southeast during the investigated episodes. In 1999, the plume was first recorded at Rzeszow in Southeastern Poland during the morning of the 4th September. Its route can be followed as it passed Krakow during the afternoon of the 4th, and later on the 4th and 5th September at Poznań. Similarly, back-trajectories calculated during the morning and afternoon from Krakow and Rzeszow on the 3rd September 2002 indicates that the air masses arrived at these sites from the East or Southeast. Conclusion: This study shows the progress of Ambrosia plumes into Poland from the southeast. Ambrosia pollen release occurs mainly during the day and so a midday peak in Ambrosia pollen concentrations may indicate a local source. However, if the plume of Ambrosia pollen tracked along its northwesterly path over Poland during investigated episodes did not originate from inside Poland, then it is likely that it came from the Ukraine. This identifies a possible new source of ragweed pollen for Poland. Trajectory analysis can only show the path along which an air mass travels, not the specific source area. Further investigation could therefore include source based transport models such as 3D Eulerian atmospheric transport models.

Determination of Alternaria spp. Habitats Using 7-Day Volumetric Spore Trap, Hybrid Single Particle Lagrangian Integrated Trajectory Model and Geographic Information System

There are many species among the Alternaria genus, which hosts on economically important crops causing significant yield losses. Less attention has been paid to fungi hosting on plants constituting substantial components of pastures and meadows. Alternaria spp. spores are also recognised as important allergens. A 7-day volumetric spore trap was used to monitor the concentration of airborne fungal spores. Air samples were collected in Worcester, England (2006–2010). Days with a high spore count were then selected. The longest episode that occurred within a five year study was chosen for modelling. Two source maps presenting distribution of crops under rotation and pastures in the UK were produced. Back trajectories were calculated using the HYSPLIT model. In ArcGIS clusters of trajectories were studied in connection with source maps by including the height above ground level and the speed of the air masses. During the episode no evidence for a long distance transport from the continent of Alternaria spp. spores was detected. The overall direction of the air masses fell within the range from South-West to North. The back trajectories indicated that the most important sources of Alternaria spp. spores were located in the West Midlands of England.

Evolutionary trajectory optimization for redundant robots

The trajectory planning of redundant robots is an important area of research and efficient optimization algorithms have been investigated in the last years. This paper presents a new technique that combines the closed-loop pseudoinverse method with genetic algorithms. In this case the trajectory planning is formulated as an optimization problem with constraints.

Trajectory planning of redundant manipulators using genetic algorithms

The trajectory planning of redundant robots is an important area of research and efficient optimization algorithms are needed. This paper presents a new technique that combines the closed-loop pseudoinverse method with genetic algorithms. The results are compared with a genetic algorithm that adopts the direct kinematics. In both cases the trajectory planning is formulated as an optimization problem with constraints.

Fractional dynamics in the trajectory control of redundant manipulators

Under the pseudoinverse control, robots with kinematical redundancy exhibit an undesirable chaotic joint motion which leads to an erratic behavior. This paper studies the complexity of fractional dynamics of the chaotic response. Fourier and wavelet analysis provides a deeper insight, helpful to know better the lack of repeatability problem of redundant manipulators. This perspective for the study of the chaotic phenomena will permit the development of superior trajectory control algorithms.

Manipulator trajectory planning using a MOEA

Generating manipulator trajectories considering multiple objectives and obstacle avoidance is a non-trivial optimization problem. In this paper a multi-objective genetic algorithm based technique is proposed to address this problem. Multiple criteria are optimized considering up to five simultaneous objectives. Simulation results are presented for robots with two and three degrees of freedom, considering two and five objectives optimization. A subsequent analysis of the spread and solutions distribution along the converged non-dominated Pareto front is carried out, in terms of the achieved diversity.

Assessing waiting times in the clinical trajectory of patients with lung cancer

Le cancer du poumon a une incidence et une létalité parmi les plus hautes de tous les cancers diagnostiqués au Canada. En considérant la gravité du pronostic et des symptômes de la maladie, l’accès au traitement dans les plus brefs de délais est essentiel. Malgré l’engagement du gouvernement fédéral et les gouvernements provinciaux de réduire les délais de temps d’attente, des balises pour les temps d’attente pour le traitement d’un cancer ne sont toujours pas établis. En outre, le compte-rendu des indicateurs des temps d’attente n’est pas uniforme à travers les provinces. Une des solutions proposées pour la réduction des temps d’attente pour le traitement du cancer est les équipes interdisciplinaires. J’ai complété un audit du programme interdisciplinaire traitant le cancer du poumon à l’Hôpital général juif (l’HGJ) de 2004 à 2007. Les objectifs primaires de l’étude étaient : (1) de faire un audit de la performance de l’équipe interdisciplinaire à l’HGJ en ce qui concerne les temps d’attente pour les intervalles critiques et les sous-groupes de patients ; (2) de comparer les temps d’attente dans la trajectoire clinique des patients traités à l’HGJ avec les balises qui existent ; (3) de déterminer les facteurs associés aux délais plus longs dans cette population. Un objectif secondaire de l’étude était de suggérer des mesures visant à réduire les temps d’attente. Le service clinique à l’HGJ a été évalué selon les balises proposées par le British Thoracic Society, Cancer Care Ontario, et la balise pan-canadienne pour la radiothérapie. Les patients de l’HGJ ont subi un délai médian de 9 jours pour l’intervalle «Ready to treat to first treatment», et un délai médian de 30 jours pour l’intervalle entre le premier contact avec l’hôpital et le premier traitement. Les patients âgés de plus de 65 ans, les patients avec une capacité physique diminuée, et les patients avec un stade de tumeur limité étaient plus à risque d’échouer les balises pour les temps d’attente.

Src family kinases are required for limb trajectory selection by spinal motor axons

Signal relay by guidance receptors at the axonal growth cone is a process essential for the assembly of a functional nervous system. We investigated the in vivo function of Src family kinases (SFKs) as growth cone guidance signaling intermediates in the context of spinal lateral motor column (LMC) motor axon projection toward the ventral or dorsal limb mesenchyme. Using in situ mRNA detection we determined that Src and Fyn are expressed in LMC motor neurons of chick and mouse embryos at the time of limb trajectory selection. Inhibition of SFK activity by C-terminal Src kinase (Csk) overexpression in chickLMCaxons using in ovo electroporation resulted inLMC axons selecting the inappropriate dorsoventral trajectory within the limb mesenchyme, with medial LMC axon projecting into the dorsal and ventral limb nerve with apparently random incidence. We also detected LMC axon trajectory choice errors in Src mutant mice demonstrating a nonredundant role for Src in motor axon guidance in agreement with gain and loss of Src function in chickLMCneurons which led to the redirection ofLMCaxons. Finally, Csk-mediated SFK inhibition attenuated the retargeting ofLMCaxons caused by EphA or EphB over-expression, implying the participation of SFKs in Eph-mediated LMC motor axon guidance. In summary, our findings demonstrate that SFKs are essential for motor axon guidance and suggest that they play an important role in relaying ephrin:Eph signals that mediate the selection of motor axon trajectory in the limb.