Minimally Invasive Parathyroidectomy in Patients with Previous Endocrine Surgery

Minimally invasive parathyroidectomy with a lateral approach was found to be an acceptable option in select patients with sporadic primary hyperparathyroidism and previous endocrine neck surgery

Application of a high-resolution weather model in the area of the western Gulf of Corinth for the tropospheric correction of interferometric synthetic aperture radar (InSAR) observations

La Géodésie spatiale, par interférométrie radar à synthèse d’ouverture (InSAR) et Global Navigation Satellite System (GNSS), permet de cartographier les déformations tectoniques de la Terre. Les vitesses inter-sismiques, sont petites, de l’ordre de quelques mm an⁻¹. Pour atteindre une précision de positionnement relatif millimétrique, surtout dans la composante verticale, les délais troposphériques affectant les signaux GNSS et InSAR doivent être parfaitement corrigés. Pour le GNSS, les délais troposphériques peuvent être évalués précisément grâce à la géométrie d’observation et à la redondance des données. La précision est telle que ces délais sont désormais assimilés en routine dans les modèles météorologiques. La correction des interférogrammes est plus complexe parce que les données InSAR ne contiennent pas d’information permettant de remonter explicitement aux délais troposphériques. Au premier ordre, il est possible de calculer la part de l’interférogramme corrélée avec la topographie et de la corriger. Mais cette correction n’éliminer pas les hétérogénéités de courte longueurs d'onde ni les gradients régionaux. Pour cela il faut utiliser d’autres méthodes qui peuvent être basées sur l’utilisation des délais zénithaux GNSS disponibles dans la région ou sur des modèles météorologiques à haute résolution, ou sur une combinaison des deux. Les délais zénithaux GNSS présentent l’intérêt de leur exactitude et de leur précision maîtrisée, mais dans la plupart des régions, ils ne sont disponibles, au mieux, qu’à quelques dizaines de points dans une image typique de 100 x 100 km. À l’opposé les modèles troposphériques à haute résolution apportent une vision matricielle globale, cependant leur précision est difficile à évaluer, surtout en zone de montagne. Dans ma thèse, je calcule, sur la partie ouest du golfe de Corinthe, et pour l’année 2016, des modèles météorologiques à la résolution de 1 km, à l’aide du modèle américain WRF (Weather Research and Forecasting). Je compare les délais zénithaux prédits par le modèle avec ceux observés à dix-neuf stations GNSS permanentes. Ces données GNSS me permettent de choisir, parmi cinque jeux différents de paramètres de calcul WRF, celui qui aboutit au meilleur accord entre les délais GNSS et ceux issus de mes modèles. Je compare ensuite les séries temporelles GNSS de l’année 2016 aux sorties de modèles aux dix-neuf pixels correspondants. J’utilise enfin les sorties de mes modèles pour corriger les interférogrammes Sentinel-1 produits dans la zone d’étude avec des intervalles d’acquisition de 6, 12, 18 et 24 jours pour lesquels la cohérence des interférogramme demeure généralement élevée. Je montre qu’un modèle météorologique à haute résolution, ajusté à l'échelle locale à l’aide de données GNSS disponibles, permet une correction troposphérique des interférogrammes qui élimine une partie significative des effets de courte longueur d’onde, jusqu’à 5 km environ, donc plus courte que la longueur d’onde typique du relief.Space geodesy techniques (SAR interferometry and GNSS) have recently emerged as an important tool for mapping regional surface deformations due to tectonic movements. A limiting factor to this technique is the effect of the troposphere, as horizontal and vertical surface velocities are of the order of a few mm yr⁻¹, and high accuracy (to mm level) is essential. The troposphere introduces a path delay in the microwave signal, which, in the case of GNSS Precise Point Positioning (PPP), can nowadays be successfully removed with the use of specialized mapping functions. Moreover, tropospheric stratification and short wavelength spatial turbulences produce an additive noise to the low amplitude ground deformations calculated by the (multitemporal) InSAR methodology. InSAR atmospheric phase delay corrections are much more challenging, as opposed to GNSS PPP, due to the single pass geometry and the gridded nature of the acquired data. Several methods have been proposed, including Global Navigation Satellite System (GNSS) zenithal delay estimations, satellite multispectral imagery analysis, and empirical phase/topography estimations. These methods have their limitations, as they rely either on local data assimilation, which is rarely available, or on empirical estimations which are difficult in situations where deformation and topography are correlated. Thus, the precise knowledge of the tropospheric parameters along the propagation medium is extremely useful for the estimation and minimization of atmospheric phase delay, so that the remaining signal represents the deformation mostly due to tectonic or other geophysical processes. In this context, the current PhD Thesis aims to investigate the extent to which a high-resolution weather model, such as WRF, can produce detailed tropospheric delay maps of the required accuracy, by coupling its output (in terms of Zenith Total Delay or ZTD) with the vertical delay component in GNSS measurements. The model initially is operated with varying parameterization in order to demonstrate the best possible configuration for our study, with GNSS measurements providing a benchmark of real atmospheric conditions. In the next phase, the two datasets (predicted and observed) are compared and statistically evaluated for a period of one year, in order to investigate the extent to which meteorological parameters that affect ZTD, can be simulated accurately by the model under different weather conditions. Finally, a novel methodology is tested, in which ZTD maps produced from WRF and validated with GNSS measurements in the first phase of the experiment are used as a correction method to eliminate the tropospheric effect from selected InSAR interferograms. Results show that a high-resolution weather model which is fine-tuned at the local scale can provide a valuable tool for the tropospheric correction of InSAR remote sensing data

Application d'un modèle météorologique à haute résolution à la correction troposphérique d'observations interférométriques de radar à synthèse d'ouverture (InSAR) dans la région de l'ouest du golfe de Corinthe, Grèce

Space geodesy techniques (SAR interferometry and GNSS) have recently emerged as an important tool for mapping regional surface deformations due to tectonic movements. A limiting factor to this technique is the effect of the troposphere, as horizontal and vertical surface velocities are of the order of a few mm yr⁻¹, and high accuracy (to mm level) is essential. The troposphere introduces a path delay in the microwave signal, which, in the case of GNSS Precise Point Positioning (PPP), can nowadays be successfully removed with the use of specialized mapping functions. Moreover, tropospheric stratification and short wavelength spatial turbulences produce an additive noise to the low amplitude ground deformations calculated by the (multitemporal) InSAR methodology. InSAR atmospheric phase delay corrections are much more challenging, as opposed to GNSS PPP, due to the single pass geometry and the gridded nature of the acquired data. Several methods have been proposed, including Global Navigation Satellite System (GNSS) zenithal delay estimations, satellite multispectral imagery analysis, and empirical phase/topography estimations. These methods have their limitations, as they rely either on local data assimilation, which is rarely available, or on empirical estimations which are difficult in situations where deformation and topography are correlated. Thus, the precise knowledge of the tropospheric parameters along the propagation medium is extremely useful for the estimation and minimization of atmospheric phase delay, so that the remaining signal represents the deformation mostly due to tectonic or other geophysical processes. In this context, the current PhD Thesis aims to investigate the extent to which a high-resolution weather model, such as WRF, can produce detailed tropospheric delay maps of the required accuracy, by coupling its output (in terms of Zenith Total Delay or ZTD) with the vertical delay component in GNSS measurements. The model initially is operated with varying parameterization in order to demonstrate the best possible configuration for our study, with GNSS measurements providing a benchmark of real atmospheric conditions. In the next phase, the two datasets (predicted and observed) are compared and statistically evaluated for a period of one year, in order to investigate the extent to which meteorological parameters that affect ZTD, can be simulated accurately by the model under different weather conditions. Finally, a novel methodology is tested, in which ZTD maps produced from WRF and validated with GNSS measurements in the first phase of the experiment are used as a correction method to eliminate the tropospheric effect from selected InSAR interferograms. Results show that a high-resolution weather model which is fine-tuned at the local scale can provide a valuable tool for the tropospheric correction of InSAR remote sensing data.La Géodésie spatiale, par interférométrie radar à synthèse d’ouverture (InSAR) et Global Navigation Satellite System (GNSS), permet de cartographier les déformations tectoniques de la Terre. Les vitesses inter-sismiques, sont petites, de l’ordre de quelques mm an⁻¹. Pour atteindre une précision de positionnement relatif millimétrique, surtout dans la composante verticale, les délais troposphériques affectant les signaux GNSS et InSAR doivent être parfaitement corrigés. Pour le GNSS, les délais troposphériques peuvent être évalués précisément grâce à la géométrie d’observation et à la redondance des données. La précision est telle que ces délais sont désormais assimilés en routine dans les modèles météorologiques. La correction des interférogrammes est plus complexe parce que les données InSAR ne contiennent pas d’information permettant de remonter explicitement aux délais troposphériques. Au premier ordre, il est possible de calculer la part de l’interférogramme corrélée avec la topographie et de la corriger. Mais cette correction n’éliminer pas les hétérogénéités de courte longueurs d'onde ni les gradients régionaux. Pour cela il faut utiliser d’autres méthodes qui peuvent être basées sur l’utilisation des délais zénithaux GNSS disponibles dans la région ou sur des modèles météorologiques à haute résolution, ou sur une combinaison des deux. Les délais zénithaux GNSS présentent l’intérêt de leur exactitude et de leur précision maîtrisée, mais dans la plupart des régions, ils ne sont disponibles, au mieux, qu’à quelques dizaines de points dans une image typique de 100 x 100 km. À l’opposé les modèles troposphériques à haute résolution apportent une vision matricielle globale, cependant leur précision est difficile à évaluer, surtout en zone de montagne. Dans ma thèse, je calcule, sur la partie ouest du golfe de Corinthe, et pour l’année 2016, des modèles météorologiques à la résolution de 1 km, à l’aide du modèle américain WRF (Weather Research and Forecasting). Je compare les délais zénithaux prédits par le modèle avec ceux observés à dix-neuf stations GNSS permanentes. Ces données GNSS me permettent de choisir, parmi cinque jeux différents de paramètres de calcul WRF, celui qui aboutit au meilleur accord entre les délais GNSS et ceux issus de mes modèles. Je compare ensuite les séries temporelles GNSS de l’année 2016 aux sorties de modèles aux dix-neuf pixels correspondants. J’utilise enfin les sorties de mes modèles pour corriger les interférogrammes Sentinel-1 produits dans la zone d’étude avec des intervalles d’acquisition de 6, 12, 18 et 24 jours pour lesquels la cohérence des interférogramme demeure généralement élevée. Je montre qu’un modèle météorologique à haute résolution, ajusté à l'échelle locale à l’aide de données GNSS disponibles, permet une correction troposphérique des interférogrammes qui élimine une partie significative des effets de courte longueur d’onde, jusqu’à 5 km environ, donc plus courte que la longueur d’onde typique du relief

Εφαρμογή μετεωρολογικού μοντέλου υψηλής ευκρίνειας για την τροποσφαιρική διόρθωση παρατηρήσεων InSAR στην περιοχή του Δυτικού Κορινθιακού Κόλπου

Space geodesy techniques (SAR interferometry and GNSS) have recently emerged as an important tool for mapping regional surface deformations due to tectonic movements. A limiting factor to this technique is the effect of the troposphere, as horizontal and vertical surface velocities are of the order of a few mm yr-1, and high accuracy (to mm level) is essential. The troposphere introduces a path delay in the microwave signal, which, in the case of GNSS Precise Point Positioning (PPP), can nowadays be successfully removed with the use of specialized mapping functions. Moreover, tropospheric stratification and short wavelength spatial turbulences produce an additive noise to the low amplitude ground deformations calculated by the (multitemporal) InSAR methodology. InSAR atmospheric phase delay corrections are much more challenging, as opposed to GNSS PPP, due to the single pass geometry and the gridded nature of the acquired data. Several methods have been proposed, including Global Navigation Satellite System (GNSS) zenithal delay estimations, satellite multispectral imagery analysis, and empirical phase/topography estimations. These methods have their limitations, as they rely either on local data assimilation, which is rarely available, or on empirical estimations which are difficult in situations where deformation and topography are correlated. Thus, the precise knowledge of the tropospheric parameters along the propagation medium is extremely useful for the estimation and minimization of atmospheric phase delay, so that the remaining signal represents the deformation mostly due to tectonic or other geophysical processes. In this context, the current PhD Thesis aims to investigate the extent to which a high-resolution weather model, such as WRF, can produce detailed tropospheric delay maps of the required accuracy, by coupling its output (in terms of Zenith Total Delay or ZTD) with the vertical delay component in GNSS measurements. The model initially is operated with varying parameterization in order to demonstrate the best possible configuration for our study, with GNSS measurements providing a benchmark of real atmospheric conditions. In the next phase, the two datasets (predicted and observed) are compared and statistically evaluated for a period of one year, in order to investigate the extent to which meteorological parameters that affect ZTD, can be simulated accurately by the model under different weather conditions. Finally, a novel methodology is tested, in which ZTD maps produced from WRF and validated with GNSS measurements in the first phase of the experiment are used as a correction method to eliminate the tropospheric effect from selected InSAR interferograms. Results show that a high-resolution weather model which is fine-tuned at the local scale can provide a valuable tool for the tropospheric correction of InSAR remote sensing data.Το αντικείμενο της διδακτορικής διατριβής είναι η ανάπτυξη μίας καινοτόμου μεθοδολογίας για την αφαίρεση της τροποσφαιρικής επίδρασης από εφαρμογές διαστημικής γεωδαισίας (GNSS και InSAR), οι οποίες αποτελούν σημαντικά εργαλεία για την παρακολούθηση περιβαλλοντικών παραμέτρων όπου απαιτείται υψηλή ακρίβεια ανίχνευσης (της τάξεως των χιλιοστών του μέτρου), όπως για παράδειγμα η μέτρηση επιφανειακών μετατοπίσεων του φλοιού της γης εξαιτίας τεκτονικών φαινομένων. Η τροπόσφαιρα εισαγάγει μια καθυστέρηση στο ηλεκτρομαγνητικό σήμα, η οποία διορθώνεται μερικώς (μόνο για τα GNSS), με την χρήση εξειδικευμένων τροποσφαιρικών μοντέλων. Επιπροσθέτως, η ατμοσφαιρική διαστρωμάτωση και οι έντονες χωροχρονικές διακυμάνσεις των υδρατμών μέσα σε αυτήν παράγουν ένα πρόσθετο «θόρυβο» στην παραμόρφωση του εδάφους που υπολογίζεται με την μεθοδολογία της συμβολομετρίας (InSAR). Επομένως, η γνώση των τροποσφαιρικών παραμέτρων κατά μήκος του μέσου διάδοσης μπορεί να χρησιμοποιηθεί για τον υπολογισμό και την ελαχιστοποίηση της επίδραση του θορύβου αυτού, έτσι ώστε το εναπομένον σήμα να περιγράφει την παραμόρφωση, ως επί το πλείστον, λόγω τεκτονικών ή άλλων γεωφυσικών διεργασιών. Ο πρωταρχικός στόχος της παρούσας διδακτορικής διατριβής είναι η σύζευξη της κατακόρυφης συνιστώσας των μετρήσεων GNSS υψηλής ακρίβειας (Precise Point Positioning), με τα δεδομένα εξόδου ενός μετεωρολογικού μοντέλου υψηλής ανάλυσης (WRF), ώστε να εξακριβωθεί η εγκυρότητα των αποτελεσμάτων και να παραμετροποιηθεί κατάλληλα το μοντέλο. Ταυτόχρονα, η τρισδιάστατη «τομογραφία» της τροπόσφαιρας που προκύπτει, μας επιτρέπει την ανάκτηση, με μεγαλύτερη ακρίβεια, του συνολικού ποσοστού των υδρατμών στην κατακόρυφη στήλη (Integrated Water Vapor ή IWV) από τα τροποσφαιρικά δεδομένα των μετρήσεων, μετατρέποντας έτσι, δυνητικά, ένα επίγειο δίκτυο δεκτών GNSS σε μετεωρολογικό προγνωστικό εργαλείο. Επιπλέον, η μελέτη επεκτείνεται στην διόρθωση της τροποσφαιρικής επίδρασης σε συμβολογραφήματα από περιοδικές λήψεις InSAR, κατά την ίδια περίοδο, για την περιοχή του Δυτικού Κορινθιακού Κόλπου. Κατ’ αυτόν τον τρόπο, η μεθοδολογία συνδυάζει σημειακές μετεωρολογικές παρατηρήσεις (GNSS) με τρισδιάστατα χωρικά μετεωρολογικά δεδομένα (WRF), για την παραγωγή αναλυτικών χαρτών ζενιθείας τροποσφαιρικής διόρθωσης (ZTD), που χρησιμοποιούνται για την αφαίρεση του θορύβου από τις απεικονίσεις InSAR

Online)

ABSTRACT Context Heterotopic pancreas of the gallbladder is an extremely rare entity, especially when pancreatic tissue appears histologically with an exclusively exocrine structure. Case report We report the case of a 35-year-old man who presented with symptoms of acalculous gallbladder disease with high levels of amylasuria. Immunohistochemical analysis of the surgical specimen of the cholecystectomy revealed pancreatic tissue at the gallbladder wall. Conclusions Heterotopic pancreatic tissue is a rare pathological finding in the gallbladder. It requires consideration and sensitization in the differential diagnosis of acalculous gallbladder disease, which can explain hyperamylasuria in cases of unknown origin

Tropospheric Correction of Sentinel-1 Synthetic Aperture Radar Interferograms Using a High-Resolution Weather Model Validated by GNSS Measurements

International audienceSynthetic Aperture Radar Interferometry (InSAR) is a space geodetic technique used for mapping deformations of the Earth’s surface. It has been developed and used increasingly during the last thirty years to measure displacements produced by earthquakes, volcanic activity and other crustal deformations. A limiting factor to this technique is the effect of the troposphere, as spatial and temporal variations in temperature, pressure, and relative humidity introduce significant phase delays in the microwave imagery, thus “masking” surface displacements due to tectonic or other geophysical processes. The use of Numerical Weather Prediction (NWP) models as a tropospheric correction method in InSAR can tackle several of the problems faced with other correction techniques (such as timing, spatial coverage and data availability issues). High-resolution tropospheric modelling is particularly useful in the case of single interferograms, where the removal of the atmospheric phase screen (and especially the highly variable turbulent component) can reveal large-amplitude deformation signals (as in the case of an earthquake). In the western Gulf of Corinth, prominent topography makes the removal of both the stratified and turbulent atmospheric phase screens a challenging task. Here, we investigate the extent to which a high-resolution WRF 1-km re-analysis can produce detailed tropospheric delay maps of the required accuracy by coupling its output (in terms of Zenith Total Delay or ZTD) with the vertical delay component in GNSS measurements. The model is operated with varying physical parameterization in order to identify the best configuration, and validated with GNSS zenithal tropospheric delays, providing a benchmark of real atmospheric conditions. We correct sixteen Sentinel-1A interferograms with differential delay maps at the line-of-sight (LOS) produced by WRF re-analysis. In most cases, corrections lead to a decrease in the phase gradient, with average root-mean-square (RMS) and standard deviation (SD) reductions in the wrapped phase of 6.0% and 19.3%, respectively. Results suggest a high potential of the model to reproduce both the long-wavelength stratified atmospheric signal and the short-wave turbulent atmospheric component which are evident in the interferograms

Use of GNSS Tropospheric Delay Measurements for the Parameterization and Validation of WRF High-Resolution Re-Analysis over the Western Gulf of Corinth, Greece: The PaTrop Experiment

International audienceIn the last thirty years, Synthetic Aperture Radar interferometry (InSAR) and the Global Navigation Satellite System (GNSS) have become fundamental space geodetic techniques for mapping surface deformations due to tectonic movements. One major limiting factor to those techniques is the effect of the troposphere, as surface velocities are of the order of a few mm yr−1, and high accuracy (to mm level) is required. The troposphere introduces a path delay in the microwave signal, which, in the case of GNSS Precise Point Positioning (PPP), can nowadays be partly removed with the use of specialized mapping functions. Moreover, tropospheric stratification and short wavelength spatial turbulences produce an additive noise to the low amplitude ground deformations calculated by the (multitemporal) InSAR methodology. InSAR atmospheric phase delay corrections are much more challenging, as opposed to GNSS PPP, due to the single pass geometry and the gridded nature of the acquired data. Thus, the precise knowledge of the tropospheric parameters along the propagation medium is extremely useful for the estimation and correction of the atmospheric phase delay. In this context, the PaTrop experiment aims to maximize the potential of using a high-resolution Limited-Area Model for the calculation and removal of the tropospheric noise from InSAR data, by following a synergistic approach and integrating all the latest advances in the fields of remote sensing meteorology (GNSS and InSAR) and Numerical Weather Forecasting (WRF). In the first phase of the experiment, presented in the current paper, we investigate the extent to which a high-resolution 1 km WRF weather re-analysis can produce detailed tropospheric delay maps of the required accuracy, by coupling its output (in terms of Zenith Total Delay or ZTD) with the vertical delay component in GNSS measurements. The model is initially operated with varying parameterization, with GNSS measurements providing a benchmark of real atmospheric conditions. Subsequently, the final WRF daily re-analysis run covers an extended period of one year, based on the optimum model parameterization scheme demonstrated by the parametric analysis. The two datasets (predicted and observed) are compared and statistically evaluated, in order to investigate the extent to which meteorological parameters that affect ZTD can be simulated accurately by the model under different weather conditions. Results demonstrate a strong correlation between predicted and observed ZTDs at the 19 GNSS stations throughout the year (R ranges from 0.91 to 0.93), with an average mean bias (MB) of –19.2 mm, indicating that the model tends to slightly underestimate the tropospheric ZTD as compared to the GNSS derived values. With respect to the seasonal component, model performance is better during the autumn period (October–December), followed by spring (April–June). Setting the acceptable bias range at ±23 mm (equal to the amplitude of one Sentinel-1 C-band phase cycle when projected to the zenithal distance), it is demonstrated that the model produces satisfactory results, with a percentage of ZTD values within the bias margin ranging from 57% in summer to 63% in autumn