Analysis of five Gigantic Jets observed near Réunion Island with video and photographic cameras

Five gigantic jets (GJ) have been recorded by a camera on March 7th 2010, at a very closedistance above an isolated tropical storm east of Réunion Island. Three of them were produced within about 4 minutes before the storm reached its coldest cloud top temperature (-81°C), and two others occurred during the extension of the cloud. The GJs tops have been estimated between 80 and 90 km. According to ELF data recorded at Nagycenk (Hungary), all GJs are negative. The GJs are accompanied by long continuous cloud illumination and they are preceded and followed by intermittent optical flashes from the cloud. The jet duration ranged from 333 ms to 850 ms while that of the leading jets markedly varied from 33 to 167 ms and that of the trailing jets ranged from 300 to 683 ms. The trailing jet exhibits a continuous decrease of luminosity in different parts of the jet (lower channel, transition zone and for most events carrot sprite-like top) and in the cloud. The lowers channels (~20-40 km altitude) produce blue luminosity which decreases with altitude and becomes more and more diffuse with time. The transition zone (around 40-65 km) consists of red luminous beads slowly going up (~ 104 m s-1), jet channels.Postprint (published version

UTILITE DU DOSSIER MEDICAL ANTERIEUR DANS LES SERVICES D'URGENCES

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Determination of the k correction factors for several detectors used with an 800 MU/min CyberKnife® system equipped with fixed collimators and study of detector characteristics on their response in small photon beams using a Monte Carlo method

International audienceIn a previous work, output ratio (ORdet) measurements were performed for the 800 MU/min CyberKnife® at the Oscar Lambret Center (COL, France) using several commercially available detectors (Sun Nuclear EDGE, IBA SFD, PTW 60016, PTW 60017, PTW 31014 and PTW 60003) designed for small beams as well as using two passive dosimeters (EBT2 radiochromic film and Harshaw micro-LiF TLD-700). The primary aim of this work was to determine by Monte Carlo calculations the output factor in water (OFMC,w) and to identify the detectors best suited to the measurements of output factors (OF) in small beams. The secondary aim was to calculate the correction factors; and also, to determine the detector response in small beams using Monte Carlo simulation

Méthodologie pour choisir un modèle de croissance du grain de blé

International audienceA methodology for choosing a model describing the wheat kernel growth of 16 wheat cultivars, grown in nine environments, is presented. Indeed, it was a preliminary and essential step before comparing the cultivars for their rates and durations of grain filling. Four current growth functions, i.e. logistic with three parameters assuming that the lower asymptote equals 0, logistic with four parameters estimating the lower asymptote, Weibull and Gompertz functions, were compared. In a first step the parameters of the curve were estimated assuming that the variance of the observed kernel weight was constant. Examining the graphs of absolute values of standardized residuals against predicted values of kernel weight highlighted that the variance of errors in the regression model was not constant and suggested modelling the variance using a power function. In a second step, modelling of the variance was added to the model. The models were compared using the likelihood ratio tests, the graphs of residuals, Akaike’s criterion and the biological meaning of the estimated final kernel weight. Significant likelihood ratio tests indicated that, for all functions except Weibull, the assumption of homogeneous variances had to be rejected; thus, it was necessary to model the variance. Comparisons of the four functions using Akaike’s criterion led to keeping the logistic function with four parameters and modelling of the variance. Comparing the estimates of the final kernel weight (95 % of the upper asymptote) obtained with this model with observed kernel weights revealed that some of the estimates were not realistic from a biological point of view. Finally, we chose to model the kernel growth using the logistic curve with three parameters for modelling the growth curve and the power function for modelling the heterogeneity of variance. In addition, a modification of the sampling protocol is also presented. (© Inra/Elsevier, Paris.)Une méthodologie pour choisir un modèle décrivant la croissance du grain de 16 variétés de blé, cultivées dans 9 milieux, est présentée. En effet, c’est une étape préliminaire et indispensable pour comparer les variétés pour leurs vitesses et durées de remplissage du grain. Quatre fonctions de croissance classiques, i. e. la logistique à trois paramètres supposant l’asymptote inférieure égale à 0, la logistique à quatre paramètres estimant l’asymptote inférieure, les fonctions de Weibull et Gompertz, ont été comparées. Lors d’une première étape, les paramètres de la courbe sont estimés avec l’hypothèse d’une variance des poids de grain observés constante. L’examen des graphiques des valeurs absolues des résidus centrés réduits contre les valeurs prédites des poids de grain indique que la variance des erreurs n’est pas constante et suggère de modéliser la variance à l’aide d’une fonction puissance. Lors d’une seconde étape, la modélisation de la variance est introduite dans le modèle. Les modèles sont comparés à l’aide du test des rapports de vraisemblance, des graphiques des résidus, du critère d’Akaike et de la signification biologique des estimations du poids de grain final. Les tests de rapport de vraisemblance significatifs indiquent que pour toutes les fonctions excepté la fonction Weibull, l’hypothèse d’homogénéité des variances doit être rejetée; il est donc nécessaire de modéliser la variance. Les comparaisons des quatre fonctions avec le critère d’Akaike conduit à garder la fonction logistique à quatre paramètres et modélisation de la variance. La comparaison des estimations du poids final du grain (95% de l’asymptote supérieure) obtenues avec ce modèle aux valeurs observées de poids du grain révèlent que certaines estimations ne sont pas réalistes d’un point de vue biologique. Finalement, une courbe logistique à trois paramètres pour modéliser la croissance du grain, avec une fonction puissance pour modéliser l’hétérogénéité des variances est retenue. Une modification du protocole de prélèvements est aussi présentée. (© Inra/Elsevier, Paris.

Methodology for choosing a model for wheat kernel growth

A methodology for choosing a model describing the wheat kernel growth of 16 wheat cultivars, grown in nine environments, is presented. Indeed, it was a preliminary and essential step before comparing the cultivars for their rates and durations of grain filling. Four current growth functions, i.e. logistic with three parameters assuming that the lower asymptote equals 0, logistic with four parameters estimating the lower asymptote, Weibull and Gompertz functions, were compared. In a first step the parameters of the curve were estimated assuming that the variance of the observed kernel weight was constant. Examining the graphs of absolute values of standardized residuals against predicted values of kernel weight highlighted that the variance of errors in the regression model was not constant and suggested modelling the variance using a power function. In a second step, modelling of the variance was added to the model. The models were compared using the likelihood ratio tests, the graphs of residuals, Akaike's criterion and the biological meaning of the estimated final kernel weight. Significant likelihood ratio tests indicated that, for all functions except Weibull, the assumption of homogeneous variances had to be rejected; thus, it was necessary to model the variance. Comparisons of the four functions using Akaike's criterion led to keeping the logistic function with four parameters and modelling of the variance. Comparing the estimates of the final kernel weight (95 % of the upper asymptote) obtained with this model with observed kernel weights revealed that some of the estimates were not realistic from a biological point of view. Finally, we chose to model the kernel growth using the logistic curve with three parameters for modelling the growth curve and the power function for modelling the heterogeneity of variance. In addition, a modification of the sampling protocol is also presented. (© Inra/Elsevier, Paris.)Méthodologie pour choisir un modèle de croissance du grain de blé. Une méthodologie pour choisir un modèle décrivant la croissance du grain de 16 variétés de blé, cultivées dans 9 milieux, est présentée. En effet, c'est une étape préliminaire et indispensable pour comparer les variétés pour leurs vitesses et durées de remplissage du grain. Quatre fonctions de croissance classiques, i. e. la logistique à trois paramètres supposant l'asymptote inférieure égale à 0, la logistique à quatre paramètres estimant l'asymptote inférieure, les fonctions de Weibull et Gompertz, ont été comparées. Lors d'une première étape, les paramètres de la courbe sont estimés avec l'hypothèse d'une variance des poids de grain observés constante. L'examen des graphiques des valeurs absolues des résidus centrés réduits contre les valeurs prédites des poids de grain indique que la variance des erreurs n'est pas constante et suggère de modéliser la variance à l'aide d'une fonction puissance. Lors d'une seconde étape, la modélisation de la variance est introduite dans le modèle. Les modèles sont comparés à l'aide du test des rapports de vraisemblance, des graphiques des résidus, du critère d'Akaike et de la signification biologique des estimations du poids de grain final. Les tests de rapport de vraisemblance significatifs indiquent que pour toutes les fonctions excepté la fonction Weibull, l'hypothèse d'homogénéité des variances doit être rejetée; il est donc nécessaire de modéliser la variance. Les comparaisons des quatre fonctions avec le critère d'Akaike conduit à garder la fonction logistique à quatre paramètres et modélisation de la variance. La comparaison des estimations du poids final du grain (95% de l'asymptote supérieure) obtenues avec ce modèle aux valeurs observées de poids du grain révèlent que certaines estimations ne sont pas réalistes d'un point de vue biologique. Finalement, une courbe logistique à trois paramètres pour modéliser la croissance du grain, avec une fonction puissance pour modéliser l'hétérogénéité des variances est retenue. Une modification du protocole de prélèvements est aussi présentée. (© Inra/Elsevier, Paris.

Study of the use of gel dosimetry in combination with 3D printing phantom for personalized pretreatment QA in radiotherapy

Le congrès a bien eu lieu en mai (https://iopscience.iop.org/article/10.1088/1742-6596/2167/1/011001/pdf) et non en juin (https://iopscience.iop.org/article/10.1088/1742-6596/2167/1/012017)International audienceIn modern radiotherapy, pretreatment patient-specific quality assurance (PSQA) generally consists in delivering the treatment plan to a phantom equipped with a detector and in comparing the measured dose and the dose calculated by the treatment planning system (TPS) in order to detect any gap between both dose distributions. Dosimetric gels have interesting properties for QA. In this work, the use of gel dosimetry together with a patient-based 3D printed phantom for personalized PSQA is investigated. CT images of a patient with a right mesencephalic brain tumor were used to generate a 3D printed phantom. Then it was filled with water and a radiochromic gel jar and irradiated according to the patient intracranial stereotactic plan using a Novalis TrueBeam STX accelerator. Measured dose distributions agree well with the calculated ones. Regarding 3D gamma-index (1 mm – 2%) estimated within the central 85% of the jar volume, 96.3% of points pass the test. In addition, 86.5% of the points pass the local 2D 3 mm-3% gamma-index. Results are promising but further work is needed to improve the protocol and investigate the possibility to extend it to end-to-end tests

Personalized pretreatment QA for intracranial stereotactic treatments using gel dosimetry and 3D printing of phantom: A feasibility study

Introduction.In stereotactic radiotherapy, pretreatment patient-specific quality controls (PSQA) are performed on generic phantoms to check the agreement between the dose calculated by the treatment planning system (TPS) and the measured dose by a point or 2D detector. For those controls, gel dosimetry seems a promising technique as it presents several advantages compared with conventional dosimeters such as 3D absolute dose determination with high spatial resolution [1]. Thus, we investigated the feasibility of gel dosimetry in combination with a patient-based 3D printed phantom for personalized PSQA.Methods. CT images of a patient treated by intracranial stereotactic radiotherapy were processed to generate a STL file. Phantom was 3D printed at scale 1:1 using an Ultimaker 3 extended 3D printer. The phantom consisted in a 1.2mm thick wall made of PET and the nose was printed separately to be used as a plug. This phantom filled with water includes a cylindrical insert at the target location to place a radiochromic gel jar. It was scanned with the patient’s stereotactic mask and the patient plan was recalculated using the phantom CT on the iPlan TPS (BrainLab). The radiochromic gels were manufactured and calibrated according to a protocol developed at IRSN [2]. One treatment fraction was delivered on the phantom with the gel in place using a Novalis TrueBeam STX accelerator. Gels were optically read following the protocol and data analysis was performed using MatLab.Results. A good agreement is found between the dose distribution measured with the gel and calculated with the TPS. For a coronal slice at the center of the gel dosimeter, the local 2D 3 mm-3% gamma-index was evaluated within the central 85% of the cylinder diameter. The gamma passing rate reaches 86.5%. In the same region, the local 3D 3 mm-3% gamma-index passing rate is 95.2%. Within the central 85% of the cylinder volume, 87.2% and 96.2% of points pass the local 2 mm-2% and the global 1 mm-2% gamma-index 3D respectively.Conclusions. This study presents promising results for personalized PSQA for stereotactic radiotherapy and this work could be extended to end-to-end tests. Other cases are currently investigated in order to benchmark the methods and the reproducibility of the measurement protocol

Out-of-field doses from radiotherapy using photon beams: A comparative study for a pediatric renal treatment

International audiencePurpose: First, this experimental study aims at comparing the normal tissue doses delivered by three radiotherapy techniques using photon beams (3DCRT, VMAT (with two different accelerators), and tomotherapy) for a typical paediatric renal treatment. Secondly, the accuracy of commercial treatment planning systems (TPS) for the assessment of normal tissue doses is evaluated.Methods: EBT3 films rigorously calibrated were positioned in two anthropomorphic phantoms representing children aged 5 and 10 years old. Those phantoms were irradiated according to one 3DCRT plan (Clinac 2100CS, Varian), two VMAT plans (Clinac 2100CS and Halcyon, Varian) and one tomotherapy plan optimized for a same tumour volume. 3-D dose determination was performed with an in-house Matlab tool using linear interpolation of film measurements. The doses were compared between techniques in 1-D, 2-D and 3-D. Finally, measured doses were also compared to the Eclipse™ (Varian Medical System) and Tomotherapy (Accuray) TPS dose calculations. Results: Advanced radiotherapy techniques (VMATs and tomotherapy) deliver higher out-of-field doses compared to 3DCRT. The differences increase with distance to target and reach a factor of 3 between VMAT and 3DCRT. This increase in peripheral doses is due to increased beam-on time triggered by intensity modulation. Besides, tomotherapy delivers lower doses than VMAT. Indeed, although tomotherapy beam-on-time is higher than in VMAT, the additional shielding of the Hi-Art tomotherapy system reduces out-of-field doses. The Halcyon system, operating in FFF mode, proves to deliver lower peripheral doses than conventional accelerators. Regarding TPS calculation, the Tomotherapy TPS proves to be suitable for out-of-field dose determination up to 30 cm from field edge whereas Eclipse™ largely underestimates those doses.Conclusion: This experimental study shows that the high dose conformation allowed by advanced radiotherapy is done at the cost of higher doses delivered outside the treatment field border. In the context of treatment-related risk estimation, the consequence of this increase in peripheral dose might be significative. The modern systems require adapted head shielding to spare normal tissues and a particular attention has to be taken regarding on-board imaging dose. Finally, advanced dose calculation algorithms implemented in commercial TPS do not certify dose accuracy beyond treatment field edges and thus, those doses are not suitable for risk assessment

Characterisation of two new radiochromic gel dosimeters TruView™ and ClearView™ in combination with the vista™ optical CT scanner: A feasibility study

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Estimating the seed content of Vitis vinifera cv. Gewurztraminer berries by two parameters related with the fecundation process

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