Third-order harmonic expansion of the magnetoencephalography forward and inverse problems in an ellipsoidal brain model.

We present a forward modeling solution in the form of an array response kernel for magnetoencephalography. We consider the case when the brain's anatomy is approximated by an ellipsoid and an equivalent current dipole model is used to approximate brain sources. The proposed solution includes the contributions up to the third-order ellipsoidal harmonic terms; hence, we compare this new approximation against the previously available one that only considered up to second-order harmonics. We evaluated the proposed solution when used in the inverse problem of estimating physiologically feasible visual evoked responses from magnetoencephalography data. Our results showed that the contribution of the third-order harmonic terms provides a more realistic representation of the magnetic fields (closer to those generated with a numerical approximation based on the boundary element method) and, subsecuently, the estimated equivalent current dipoles are a better fit to those observed in practice (e.g., in visual evoked potentials). Copyright © 2016 John Wiley & Sons, Ltd.

Propuesta de modelo de trauma vascular mediante la caracterización mecánica de prótesis endovasculares (stents) a través del análisis estructural con técnicas FEA / Proposed model of vascular trauma by mean of mechanical characterization of endovascular prostheses (stents) based on structural analysis by FEA

Resumen Objetivo Tras las evidencias acumuladas mediante el uso de técnicas de angioplastia con stents, surge la polémica sobre los factores que inciden en la respuesta final, ya que hay estudios que reportan reestenosis de la luz en el 30-40% alrededor de 6 meses luego de ser implantados, vinculándose como una de las causas al diseño del dispositivo. Este artículo propone la caracterización funcional de stents endovasculares, analizando su influencia mecánica en el sistema vascular y prediciendo los factores de trauma implícitos en el lecho de los vasos. Métodos Utilizando modelos computacionales de prótesis endovasculares tipo stents, mediante técnicas Finite Elements Analysis, se procedió al análisis estructural de dichos dispositivos con el fin de predecir el comportamiento mecánico y el trauma vascular. Para ello, las prótesis fueron consideradas estructuras tubulares compuestas por múltiples eslabones que están sometidos a cargas de presión, que se reflejan como concentradores de esfuerzos. Resultados El estudio permitió visualizar cómo se ajusta la geometría del stent a las diferentes cargas, obteniéndose una aproximación a la respuesta de interacción "sólido-sólido" entre el stent y la pared arterial. Así, se caracterizó el patrón de esfuerzos y se planteó un modelo conceptual que explica su incidencia mecánica en la interacción stent-vaso, para inferir en la funcionalidad del diseño del dispositivo. Conclusiones El modelo conceptual planteado permite determinar la relación entre las condiciones de interacción mecánicas del stent, y advierte sobre los efectos en lo que sería la operación del dispositivo en el ambiente vascular.

Abstract Objective The accumulated evidence on angioplasty techniques with stents has raised a controversy about the factors that influence the final vascular response. Indeed, several studies have shown there might be re-stenosis between 30% to 40% about 6 months after placement, relating to the design of the device as one of the main causes. This paper proposes the functional characterization of endovascular stents, analyzing its mechanical influence in the vascular system and predicting implicit traumatic factors in the vessel. Methods A structural analysis was made for several computational models of endovascular stents using Finite Element Analysis in order to predict the mechanical behavior and the vascular trauma. In this way, the stents were considered as tubular devices composed of multiple links under radial pressure loads, reflecting stress concentration effects. Results The analysis allowed to visualize how the geometry of stents is adjusted under several load conditions, in order to obtain the response of "solid-solid" interaction between the stent and the arterial wall. Thus, an analysis was performed in order to calculate stress, and a conceptual model that explains its mechanical impact on the stent-vessel interaction, was raised, to infer on the functionality from the design of the devices. Conclusions The proposed conceptual model allows to determine the relationship between the conditions of mechanical interaction of the stents, and warns about the effects in what would be the operation of the device on the vascular environment.

[Proposed model of vascular trauma by mean of mechanical characterization of endovascular prostheses (stents) based on structural analysis by FEA]. / Propuesta de modelo de trauma vascular mediante la caracterización mecánica de prótesis endovasculares (stents) a través del análisis estructural con técnicas FEA.

OBJECTIVE: The accumulated evidence on angioplasty techniques with stents has raised a controversy about the factors that influence the final vascular response. Indeed, several studies have shown there might be re-stenosis between 30% to 40% about 6 months after placement, relating to the design of the device as one of the main causes. This paper proposes the functional characterization of endovascular stents, analyzing its mechanical influence in the vascular system and predicting implicit traumatic factors in the vessel. METHODS: A structural analysis was made for several computational models of endovascular stents using Finite Element Analysis in order to predict the mechanical behavior and the vascular trauma. In this way, the stents were considered as tubular devices composed of multiple links under radial pressure loads, reflecting stress concentration effects. RESULTS: The analysis allowed to visualize how the geometry of stents is adjusted under several load conditions, in order to obtain the response of "solid-solid" interaction between the stent and the arterial wall. Thus, an analysis was performed in order to calculate stress, and a conceptual model that explains its mechanical impact on the stent-vessel interaction, was raised, to infer on the functionality from the design of the devices. CONCLUSIONS: The proposed conceptual model allows to determine the relationship between the conditions of mechanical interaction of the stents, and warns about the effects in what would be the operation of the device on the vascular environment.

[Treatment in unstable thorax. Case report]. / Tratamiento de tórax flotante. Presentación de caso.

We present 45 years-old male patient with bilateral luxation of all costochondral joints due to a compression mechanism while he was working beneath a car and the support was lost. He presented with floating sternum and ventilatory compromise among other injuries. Initially he was intubated and the costochondral joints were temporary fixated with dexon suture while making counter balance with 2 kg. As he was on positive pressure ventilation, lungs reexpanded we decided to place three anchors in each side of the sternum, fixated to an external aluminum support. After 10 days out of the intensive care unit, he was discharged and seen every 2 weeks. The anchors were retired in week number four and after 3 months he reintegrated to normal labor and daily activities, with limitation on flexo-extension of the left elbow by arthrogryposis.

Síndrome de Cornelia de Lange / Cornelia de Lange Syndrome

El Síndrome de Cornelia de Lange es un trastorno cromosómico severo e infrecuente en nuestro medio. Para su tratamiento óptimo, es preciso establecer el diagnóstico clínico temprano basándonos en las características fenotípicas más comunes y así permitir ubicar oportunidades de apoyo y manejo a largo plazo para estos pacientes. Presentamos el caso clínico de un recién nacido admitido al serviciode pediatría y neonatología del Hospital Juan XXIII de La Paz, Bolivia. Se hace un detalle de características clínicas y una discusión de algunos aspectos importantes de esta enfermedad.

Cornelia de Lange Syndrorne is a severe chromosomal anomaly infrequently seen in Bolivia. In order to offer the best treatment currently available, it is important to make an early and correct diagnosis based on the most commonly encountered pheonotypical characteristics and in this manner, establish longterm support and follow up for these patients. We present the case of a neonate admitted to the pediatric and neonatology service at Juan XXIII Hospital in La Paz, Bolivia and a discussion of some of the important features this syndrome encompasses.