Comparativa de análisis de imputación da datos faltantes con análisis de casos completos en pruebas diagnósticas

El objetivo principal de este trabajo es la comparación de diversos métodos de tratamiento de datos faltantes en bases de datos de pruebas diagnósticas generadas a partir de una base de datos, sin pérdida de datos, mediante los diferentes mecanismos de pérdida de datos (MCAR, MAR y MNAR). La base de datos original recoge información sobre tumores mamarios malignos y benignos en una muestra de mujeres. La comparación se basa en los efectos que tienen los métodos de tratamiento de datos faltantes, tanto en el modelo diagnóstico que se obtenga mediante regresión logística con sus errores estándar, como en las curvas ROC y los valores asociados a dichas curvas. El objetivo secundario es obtener el mejor modelo de regresión logística para realizar el diagnóstico de los tumores. Se parte de la base de datos original sin datos faltantes, y el modelo fina obtenido es el que se aplica para comparar los efectos de los métodos de tratamiento de datos faltantes. Se explica la manera en la que se generan bases de datos con datos faltantes según cada mecanismo de pérdida de datos, tras detallar lo que representan las diferentes variables de la base de datos original. Se explican minuciosamente los métodos utilizados de tratamiento de datos faltantes con imputación múltiple, Missing Forest y MICE, y de manera más sencilla los demás métodos, el análisis de casos completos, el método de sustitución por la media y el uso de variables indicadoras de pérdida de datos

Psychological symptoms of the outbreak of the COVID-19 confinement in Spain

We studied the short-term psychological effects of the COVID-19 crisis and the quarantine on 3550 adults from the Spanish population in a cross-sectional survey. Symptoms of anxiety, depression, and stress were analyzed using the 21-item version of the Depression Anxiety Stress Scale. Symptoms of posttraumatic stress disorder were analyzed using the Impact of Event Scale. Symptomatic scores of anxiety, depression, and stress were observed in 20% to 30% of respondents. Symptomatic scores indicating psychological stress were found in 47.5% of respondents. Similar to the findings of other multiple studies, confinement has been found to have significant emotional impact in the Spanish population

Moment-based representation of the diffusion inside the brain from reduced DMRI acquisitions: Generalized AMURA

Producción CientíficaAMURA (Apparent Measures Using Reduced Acquisitions) was originally proposed as a method to infer micro-structural information from single-shell acquisitions in diffusion MRI. It reduces the number of samples needed and the computational complexity of the estimation of diffusion properties of tissues by assuming the diffusion anisotropy is roughly independent on the b-value. This simplification allows the computation of simplified expressions and makes it compatible with standard acquisition protocols commonly used even in clinical practice. The present work proposes an extension of AMURA that allows the calculation of general moments of the diffusion signals that can be applied to describe the diffusion process with higher accuracy. We provide simplified expressions to analytically compute a set of scalar indices as moments of arbitrary orders over either the whole 3-D space, particular directions, or particular planes. The existing metrics previously proposed for AMURA (RTOP, RTPP and RTAP) are now special cases of this generalization. An extensive set of experiments is performed on public data and a clinical clase acquired with a standard type acquisition. The new metrics provide additional information about the diffusion processes inside the brain.Ministerio de Ciencia, Innovación y Universidades (grant RTI2018-094569-B-I00)Polish National Agency for Academic Exchange (grant PN/BEK/2019/1/00421)Ministry of Science and Higher Education of Poland (scholarship 692/STYP/13/2018)Junta de Castilla y León - Fondo Social Europeo (ID: 376062

Structural brain changes in patients with persistent headache after COVID-19 resolution

Producción CientíficaHeadache is among the most frequently reported symptoms after resolution of COVID-19. We assessed structural brain changes using T1- and diffusion-weighted MRI processed data from 167 subjects: 40 patients who recovered from COVID- 19 but suffered from persistent headache without prior history of headache (COV), 41 healthy controls, 43 patients with episodic migraine and 43 patients with chronic migraine. To evaluate gray matter and white matter changes, morphometry parameters and diffusion tensor imaging-based measures were employed, respectively. COV patients showed significant lower cortical gray matter volume and cortical thickness than healthy subjects (p < 0.05, false discovery rate corrected) in the inferior frontal and the fusiform cortex. Lower fractional anisotropy and higher radial diffusivity (p < 0.05, family-wise error corrected) were observed in COV patients compared to controls, mainly in the corpus callosum and left hemisphere. COV patients showed higher cortical volume and thickness than migraine patients in the cingulate and frontal gyri, paracentral lobule and superior temporal sulcus, lower volume in subcortical regions and lower curvature in the precuneus and cuneus. Lower diffusion metric values in COV patients compared to migraine were identified prominently in the right hemisphere. COV patients present diverse changes in the white matter and gray matter structure. White matter changes seem to be associ- ated with impairment of fiber bundles. Besides, the gray matter changes and other white matter modifications such as axonal integrity loss seemed subtle and less pronounced than those detected in migraine, showing that persistent headache after COVID-19 resolution could be an intermediate state between normality and migraine.Gerencia Regional de Salud (GRS) de Castilla y León, (GRS 2284/A/2020)Publicación en abierto financiada por el Consorcio de Bibliotecas Universitarias de Castilla y León (BUCLE), con cargo al Programa Operativo 2014ES16RFOP009 FEDER 2014-2020 DE CASTILLA Y LEÓN, Actuación:20007-CL - Apoyo Consorcio BUCL

Optimisation of quantitative brain diffusion-relaxation MRI acquisition protocols with physics-informed machine learning

Diffusion-relaxation MRI aims to extract quantitative measures that characterise microstructural tissue properties such as orientation, size, and shape, but long acquisition times are typically required. This work proposes a physics-informed learning framework to extract an optimal subset of diffusion-relaxation MRI measurements for enabling shorter acquisition times, predict non-measured signals, and estimate quantitative parameters. In vivo and synthetic brain 5D-Diffusion- T 1 - T 2 ∗ -weighted MRI data obtained from five healthy subjects were used for training and validation, and from a sixth participant for testing. One fully data-driven and two physics-informed machine learning methods were implemented and compared to two manual selection procedures and Cramér-Rao lower bound optimisation. The physics-informed approaches could identify measurement-subsets that yielded more consistently accurate parameter estimates in simulations than other approaches, with similar signal prediction error. Five-fold shorter protocols yielded error distributions of estimated quantitative parameters with very small effect sizes compared to estimates from the full protocol. Selected subsets commonly included a denser sampling of the shortest and longest inversion time, lowest echo time, and high b-value. The proposed framework combining machine learning and MRI physics offers a promising approach to develop shorter imaging protocols without compromising the quality of parameter estimates and signal predictions

Default mode network components and its relationship with anomalous self-experiences in schizophrenia: A rs-fMRI exploratory study

Producción CientíficaAnomalous self-experiences (ASEs) in schizophrenia have been under research for the last 20 years. However, no neuroimage studies have provided insight of the possible biological underpinning of ASEs. In this novel approach, the connectivity within the default mode network, calculated through a ROI-based analysis of functional magnetic resonance imaging data, was correlated to the ASEs scores assessed by the Inventory of Psychotic-Like Anomalous Self-Experiences (IPASE) in a sample of 22 schizophrenia patients. The Pearson's correlation coefficients between IPASE scores and intrahemispheric connectivity of the parahippocampal gyrus with the isthmus cingulate cortex in both hemispheres, and right parahippocampal gyrus with the right rostral anterior cingulate cortex were positive and significant suggesting a relation between hyperactive functional connectivity and anomalous self-experiences intensity. Prior literature reported these areas to have a role in self-processing and consciousness as well as being anatomically connected. Further research with larger sample size and comparison with controls are needed to confirm the relationship of this connectivity with anomalous self-experiences.Instituto de Salud Carlos III (beca ID PI18/00178)Junta de Castilla y León (Dirección Regional de Salud de Castilla y León - grant ID GRS 2121/A/20)Junta de Castilla y León” and the European Social Fund (grant IDs VA-183-18 to IFL, VA-223-19 to RMBR

Band-gaps electromagnéticos con celdas unidad de tres dieléctricos

Electromagnetic band-gap structures (EBG) with Kronig-Penney morphology implemented inside rectangular waveguides are theoretically and experimentally examined using a unit cell with three dielectrics. Filtering properties of these structures are analysed, invoking the Floquet theorem for ideal structures (infinite in the propagation direction), and by means of the scattering matrix technique for real structures (i.e., of finite length). Measurements of the transmission coefficient for the fundamental mode in the Ku-band are presented

A multimodal analysis of Magnetic Resonance Imaging for the study of brain abnormalities in migraine: gray matter morphometry, white matter integrity and structural connectivity

Migraine is one of the most common causes of disability, especially among young women. Despite the high migraine prevalence and its consequences, currently there are no migraine biomarkers and the diagnosis is exclusively based on the description of the symptoms by the patient. Furthermore, the migraine pathophysiology is not completely understood yet. In order to find a migraine biomarker and better understand the migraine pathophysiology, Magnetic Resonance Imaging (MRI) has been employed thanks to its excellent tissue contrast and spatial resolution using non-ionizing radiation. Multiple studies that have assessed gray matter and white matter structure in patients with migraine have shown conflicting results, although some patterns such as loss of gray matter volume have been widely described. From the clinical point of view, other important assessments like the comparison between the two current main migraine types, Chronic Migraine (CM) and Episodic Migraine (EM), have been barely carried out. Considering the technical perspective, specific evaluations of the structural connections between gray matter regions and the relationships between the MRI findings from different modalities have not been performed. In the present doctoral thesis, the main objective was the characterization of gray matter and white matter structural properties of patients with CM and EM. With regard to both migraine groups, the comparison between the two migraine types through the employment of diverse MRI processing techniques is also included in the main objective. The use of advanced and novel diffusion measures not employed previously in the migraine literature was also considered to provide an additional strategy for the assessment of white matter. An evaluation of the diffusion MRI (dMRI) acquisition parameters in association with the sample size was carried out to identify possible sources of the variability. Moreover, the structural connections between gray matter regions through the white matter tracts were assessed, bearing in mind their possible relationship with gray matter morphometry.Departamento de Teoría de la Señal y Comunicaciones e Ingeniería TelemáticaDoctorado en Tecnologías de la Información y las Telecomunicacione

Longitudinal evaluation of the psychological impact of the COVID-19 crisis in Spain

The aim of this study was to assess the temporal evolution of the psychological impact of the COVID-19 crisis and lockdown from two surveys carried out in Spain with a time difference of about one month. Symptoms of depression, anxiety and stress, and the psychological impact of the situation were longitudinally analyzed using the Depression Anxiety and Stress Scale (DASS-21) and the Impact of Event Scale (IES) respectively. The Brief Resilient Coping Scale (BRCS) and the Mini-Social Phobia Inventory (Mini-SPIN) were also employed to evaluate resilience and social anxiety. There was a total of 4,724 responses from both surveys. Symptomatic scores of anxiety, depression and stress were exhibited by 37.22%, 46.42% and 49.66% of the second survey respondents, showing a significant increase compared to the first survey (32.45%, 44.11% and 37.01%, respectively). There was no significant longitudinal change of the IES scores, with 48.30% of the second survey participants showing moderate to severe impact of the confinement. Low resilience was shown by 40.5% of the respondents, and high social anxiety by 34.8%. Constant news consumption about COVID-19 was found to be positively associated with symptomatic scores in the different scales. On the other hand, daily physical activity was found to be negatively associated with DASS-21 scores. Results indicate that people with social anxiety might be especially vulnerable to the development of other mental disorders after the relaxation of the confinement measures

Psychological symptoms of the outbreak of the COVID-19 crisis and confinement in the population of Spain

Background: The outbreak and spread of a novel coronavirus disease (COVID-19) led to a confinement situation in many countries worldwide. Our objective was to analyze the short-term psychological effects of the COVID-19 crisis and the quarantine on the population. Methods: A cross-sectional study was conducted. A survey was completed by 3550 adults from Spain. Symptoms of anxiety, depression and stress were analyzed using the 21-item version of the Depression Anxiety Stress Scale. Symptoms of posttraumatic stress disorder were analyzed using the Impact of Event Scale. Results: Symptomatic scores of anxiety, depression, stress were observed in 32.4%, 44.1% and 37.0% of respondents, respectively. Also, symptomatic scores indicating psychological stress were found in 88.6% of respondents. Increased prevalence of anxiety, depression and stress symptoms was associated with female sex, younger age, self-reported COVID-19 symptoms, previous psychological or psychiatric treatment, intake of psychoactive medication and negative effect on social relationships and relationships with people living in the same place. Higher scores related to symptoms of posttraumatic stress disorder was associated with most of those factors, and also with the acquaintance with a COVID-19 patient. Conclusion: An important emotional impact of confinement related to COVID-19 has been found in Spanish population. Considering a possible long period of confinement, the evolution of the psychological effects should be controlled to prevent severe mental health disorders