Utilización de los diagramas de Minkowski para la enseñanza de la Teoría Especial de la Relatividad en la escuela secundaria

En este trabajo se presentan los resultados de la implementación de una etapa de una Secuencia de Enseñanza y Aprendizaje diseñada para abordar la Teoría Especial de la Relatividad en la escuela secundaria superior, en Argentina. Se adopta el modelo de Enseñanza para la Comprensión dentro de un marco teórico más amplio que promueve un aprendizaje significativo de la Teoría Especial de la Relatividad.El objetivo de esta investigación es analizar si la utilización de los diagramas de Minkowski, para establecer la simultaneidad de eventos en la Teoría Especial de la Relatividad, es una herramienta apropiada para la escuela secundaria.La metodología empleada en la investigación es cualitativa de tipo descriptiva. La implementación se realizó en dos cursos de secundaria superior de una escuela pública dependiente de la Universidad Nacional del Centro, conformados por 65 alumnos. Los resultados obtenidos evidencian rasgos de aprendizaje significativo de la Teoría Especial de la Relatividad, por parte de los alumnos.In this paper the results of the implementation of a step in a Teaching - Learning sequence designed to approach the Special Relativity Theory in high school in Argentina are presented. The purpose of this research is to analyze whether the use of Minkowski diagrams to establish the simultaneity of events in the Special Relativity Theory is an appropriate tool for high school. The methodology used in this research is qualitative and descriptive. The implementation was done in two courses of a public high school that is dependent of the Universidad Nacional del Centro (Argentina), with 65 students. The results show that students achieved meaningful learning in some topics of Special Relativity Theory.Fil: Cayul, Esther. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Grupo Educación en Ciencias con Tecnologías; ArgentinaFil: Arriassecq, Irene. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Grupo Educación en Ciencias con Tecnologías; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

User-initialized active contour segmentation and golden-angle real-time cardiovascular magnetic resonance enable accurate assessment of LV function in patients with sinus rhythm and arrhythmias

BACKGROUND: Data obtained during arrhythmia is retained in real-time cardiovascular magnetic resonance (rt-CMR), but there is limited and inconsistent evidence to show that rt-CMR can accurately assess beat-to-beat variation in left ventricular (LV) function or during an arrhythmia. METHODS: Multi-slice, short axis cine and real-time golden-angle radial CMR data was collected in 22 clinical patients (18 in sinus rhythm and 4 patients with arrhythmia). A user-initialized active contour segmentation (ACS) software was validated via comparison to manual segmentation on clinically accepted software. For each image in the 2D acquisitions, slice volume was calculated and global LV volumes were estimated via summation across the LV using multiple slices. Real-time imaging data was reconstructed using different image exposure times and frame rates to evaluate the effect of temporal resolution on measured function in each slice via ACS. Finally, global volumetric function of ectopic and non-ectopic beats was measured using ACS in patients with arrhythmias. RESULTS: ACS provides global LV volume measurements that are not significantly different from manual quantification of retrospectively gated cine images in sinus rhythm patients. With an exposure time of 95.2 ms and a frame rate of > 89 frames per second, golden-angle real-time imaging accurately captures hemodynamic function over a range of patient heart rates. In four patients with frequent ectopic contractions, initial quantification of the impact of ectopic beats on hemodynamic function was demonstrated. CONCLUSION: User-initialized active contours and golden-angle real-time radial CMR can be used to determine time-varying LV function in patients. These methods will be very useful for the assessment of LV function in patients with frequent arrhythmias

Women physicians in cardiovascular magnetic resonance: past, present, and future

Women's engagement in medicine, and more specifically cardiovascular imaging and cardiovascular MRI (CMR), has undergone a slow evolution over the past several decades. As a result, an increasing number of women have joined the cardiovascular imaging community to contribute their expertise. This collaborative work summarizes the barriers that women in cardiovascular imaging have overcome over the past several years, the positive interventions that have been implemented to better support women in the field of CMR, and the challenges that still remain, with a special emphasis on women physicians

Parallel MR imaging

Parallel imaging is a robust method for accelerating the acquisition of magnetic resonance imaging (MRI) data, and has made possible many new applications of MR imaging. Parallel imaging works by acquiring a reduced amount of k ‐space data with an array of receiver coils. These undersampled data can be acquired more quickly, but the undersampling leads to aliased images. One of several parallel imaging algorithms can then be used to reconstruct artifact‐free images from either the aliased images (SENSE‐type reconstruction) or from the undersampled data (GRAPPA‐type reconstruction). The advantages of parallel imaging in a clinical setting include faster image acquisition, which can be used, for instance, to shorten breath‐hold times resulting in fewer motion‐corrupted examinations. In this article the basic concepts behind parallel imaging are introduced. The relationship between undersampling and aliasing is discussed and two commonly used parallel imaging methods, SENSE and GRAPPA, are explained in detail. Examples of artifacts arising from parallel imaging are shown and ways to detect and mitigate these artifacts are described. Finally, several current applications of parallel imaging are presented and recent advancements and promising research in parallel imaging are briefly reviewed

GRAPPA Operator Shift Correction for Non-Cartesian Imaging Trajectories

Gradient timing delays can cause deviations from the ideal trajectory in non-Cartesian imaging. The proposed method aims to correct for trajectory errors and determine the signal at the center of k-space. Paths between points acquired along mis-centered radial projections and the true center of k-space are traced by a gradient ascent algorithm which iteratively applies a GRAPPA operator to shift k-space data while continually evaluating an estimate of the echo peak signal. This method can be used to perform trajectory measurement without field monitoring or extra acquisitions, and signal at the true k-space center can be used for retrospective self-gated imaging

MR Fingerprinting with Chemical Exchange (MRF-X) for In Vivo Multi-Compartment Relaxation and Exchange Rate Mapping

MR Fingerprinting with Chemical Exchange (MRF-X) is presented for in vivo quantification of relaxation times, volume fraction, and exchange rate for tissues with two compartments. Data are presented in healthy volunteers in both brain and leg skeletal muscle and compared with previously reported measurements