1,721,200 research outputs found
Chapter 9. Pulse Sequences Combining Advanced Diffusion Encoding and Image Read-out
No full textAdvanced diffusion encoding strategies open new windows of exploration into microstructure in vivo. Their success in research and clinical applications relies on imaging methods able to sample this multidimensional parameter space efficiently to provide high quality data. Furthermore, creative strategies to encode novel contrasts, such as combined relaxation-diffusion correlation weightings and novel diffusion preparations can in turn inspire new analysis possibilities. This chapter introduces the most commonly used single-shot Cartesian echo planar imaging technique, discusses acceleration strategies and introduces concepts for increased flexibility. </p
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Translational Motion of Water in Biological Tissues-A Brief Primer
No full textAs an introduction to the rigorous treatment of diffusion encoding in the rest of the book, this chapter gives simple non-mathematical explanations of the relations between the properties of biological tissues and the translational motion of the tissue water with the aim of conveying an intuitive feel of the relevant time and length scales and the level of detail of the information that can be obtained. The influence of biomembranes and macromolecules on water dynamics is reviewed from both molecular and cellular scale perspectives. The potentially complex motion patterns are decomposed into short-time diffusivity, restriction, anisotropy, flow, and exchange, which can be independently assessed and correlated with advanced diffusion encoding methods in MRI
Advanced Diffusion Encoding Methods in MRI
No full textThe medical MRI community is by far the largest user of diffusion NMR techniques and this book captures the current surge of methods and provides a primary source to aid adoption in this field.
There is a trend to adapting the more advanced diffusion encoding sequences developed by NMR researchers within the fields of porous media, chemical engineering, and colloid science to medical research. Recently published papers indicate great potential for improved diagnosis of the numerous pathological conditions associated with changes of tissue microstructure that are invisible to conventional diffusion MRI. This book disseminates these recent developments to the wider community of MRI researchers and clinicians. The chapters cover the theoretical basis, hardware and pulse sequences, data analysis and validation, and recent applications aimed at promoting further growth in the field.
This is a fast moving field and chapters are written by key MRI scientists that have contributed to the successful translation of the advanced diffusion NMR methods to the context of medical MRI, from global locations
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Estimating chemical and microstructural heterogeneity by correlating relaxation and diffusion
Full text linkWhereas diffusion NMR can probe the structural configurations of microscopic environments in biological tissue, relaxation can provide complementary information mainly related to their chemical composition. This chapter considers experiments in which diffusion and relaxation properties are sampled simultaneously by varying multiple acquisition parameters. As such, correlations between the diffusion and relaxation can be established, providing an altogether more complete picture of heterogeneous tissue
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Clinical Research with Advanced Diffusion Encoding Methods in MRI
No full textThis chapter offers a comprehensive summary of applications of advanced diffusion encoding methods in MRI within a narrowly defined area of in vivo human measurements with imaging read-out and voxel-by-voxel data analysis. The list of methods comprises tensor-valued encoding to investigate cell densities, shapes, and orientations in heterogeneous tissues, time/frequency-dependent encoding for estimating structural length scales, adjustable velocity-encoding to monitor flow in the microcapillary network, double encoding with varying mixing times to assess diffusional exchange between distinct tissue microenvironments and across cell membranes, and relaxation-diffusion correlation to resolve and separately characterize tissue microenvironments in terms of their local chemical composition and microstructure. The shown examples include proof-of-concept measurements on healthy volunteers, pilot investigations of pathologies, and clinical research involving 10-100 subjects. Studied organs include brain, breast, prostate, liver, kidney, placenta, muscle, and peripheral nerve, with examples of pathologies from tumors, schizophrenia, multiple sclerosis, stroke, neurocysticercosis, pre-eclampsia, and chronic exertional compartment syndrome
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
