Advanced parallel magnetic resonance imaging methods with applications to MR spectroscopic imaging

Parallel magnetic resonance imaging offers a framework for acceleration of conventional MRI encoding using an array of receiver coils with spatially-varying sensitivities. Novel encoding and reconstruction techniques for parallel MRI are investigated in this dissertation. The main goal is to improve the actual reconstruction methods and to develop new approaches for massively parallel MRI systems that take advantage of the higher information content provided by the large number of small receivers. A generalized forward model and inverse reconstruction with regularization for parallel MRI with arbitrary k-space sub-sampling is developed. Regularization methods using the singular value decomposition of the encoding matrix and pre-conditioning of the forward model are proposed to desensitize the solution from data noise and model errors. Variable density k-space sub-sampling is presented to improve the reconstruction with the common uniform sub-sampling. A novel method for massively parallel MRI systems named Superresolution Sensitivity Encoding (SURE-SENSE) is proposed where acceleration is performed by acquiring the low spatial resolution representation of the object being imaged and the stronger sensitivity variation from small receiver coils is used to perform intra-pixel reconstruction. SURE-SENSE compares favorably the performance of standard SENSE reconstruction for low spatial resolution imaging such as spectroscopic imaging. The methods developed in this dissertation are applied to Proton Echo Planar Spectroscopic Imaging (PEPSI) for metabolic imaging in human brain with high spatial and spectral resolution in clinically feasible acquisition times. The contributions presented in this dissertation are expected to provide methods that substantially enhance the utility of parallel MRI for clinical research and to offer a framework for fast MRSI of human brain with high spatial and spectral resolution

Reacción Electroquímica de Polietilendioxitiofeno (PEDOT). Metodología para el cálculo de parámetros cinéticos

El propósito de desarrollar modelos cinéticos es el de obtener las constantes del proceso de tal manera que permita una mejora en las posibles aplicaciones (actuadores, membranas o dispositivos electrocrómicos).Agradecimientos: trabajo financiado por el MEC. Proyecto CTQ2005-00908 (grupo D023-01) y (CTQ2006-26262-E)

Bacterial communities and antibiotic resistance in human-impacted water environments

From a One-Health concept the health of humans, animals and the environment is interconnected and what happens to one of the domains will affect the other two simultaneously. This concept can be applied not only to the transmission of bacterial infectious diseases but also to the transmission of antibiotic resistance. While bacterial infectious diseases caused by water-borne pathogens are still a leading cause of morbidity and mortality worldwide, the development and spread of antibiotic resistant bacteria is threatening human health like never before. If we are not able to control the generation and spread of antibiotic resistant bacteria, in the near future thousands of people will die of infections that were treatable before. The relationship between human and animal health has been widely studied before but the environment is usually set aside minimizing the impact and effect of contaminated environments on human and animal health. Contaminated water environments represent a suitable place for the accumulation, spread and transmission of pathogenic and antibiotic resistant bacteria. In that sense, water environments are good interfaces where the transfer of antibiotic resistance determinants between bacteria might occur. Hence water environments might represent a good place for the surveillance of pathogenic bacteria and antibiotic resistance. In this thesis we aimed to characterize pathogenic and non-pathogenic bacterial communities as well as antibiotic resistant bacteria and antibiotic resistance genes in highly contaminated rivers in La Paz and Oruro in Bolivia as well as in a waster water pump at a suburban community in Oslo. We also aimed to evaluate the potential of bacterial communities from contaminated water environments to transfer antibiotic resistance determinants to E. coli and test the effect of heavy metals in the occurrence and transfer of antibiotic resistance. We found high prevalence of enterobacteria, pathogenic E. coli and other diarrheal bacteria in water, agricultural soil and vegetables from an urban-impacted basin in La Paz, Bolivia (Paper I). Moreover, we repeatedly found the globally distributed and multi-drug resistant E. coli sequence types ST131 in Norway and ST648 both in Bolivia and Norway showing the important role of the environment for the dispersion of pathogenic and antibiotic resistant bacteria (Paper I and II). Additionally, we proved a high capability of bacterial communities from contaminated water environments to transfer antibiotic resistance determinants to E. coli. We showed that presence of metals such as ZnSO4 and CuSO4 in conjugation experiments might favor the transfer/acquisition of more diverse phenotypic multi-drug resistance profiles and mobile genetic elements carrying higher diversity of genes including extended spectrum beta-lactamases and other relevant genes conferring important advantages to the bacterial host (Paper III). Bacterial donors from contaminated irrigation water transferred a high diversity of antibiotic resistance determinants at considerable levels showing the potential risk of transmission of antibiotic resistance to human populations by contaminated irrigation water and vegetables (Paper III). We did not find significant associations between metal composition, bacterial communities and the abundance of selected antibiotic resistance determinants in acid mine drainage contaminated watersheds in Oruro, Bolivia (Paper IV)

Psychotherapy to treat consequences of interpersonal violence suffered in childhood and adolescence in Latin America:A systematic review

Introduction/Objective. As in the rest of the world, in Latin America there is a high prevalence of interpersonal violence (IV) in childhood and adolescence, which is associated with psychological consequences in the short, medium and long term. At the international level, progress has been made in the recognition of evidence-based psychotherapies, but the situation in Latin America is unknown. The objective of this systematic review of the literature is to identify which models or modalities of psychotherapy have been shown to be effective in Latin America. Methods. A systematic search of five databases was carried out with search terms relating to psychosocial interventions people exposed to IV during childhood, based in Latin America. Studies on Latino populations based in United States were excluded.Results. 14 papers describing 13 studies and one follow-up were identified. Individual and group interventions (mainly cognitive-behavioural and with psychodynamic influence) were included. Although all showed clinically or statistically significant changes in symptoms of post-traumatic stress, anxiety and depression, most were pilot studies with important methodological limitations and high risk of bias.Conclusions. It is necessary to progress clinical practice in Latin America with more robust research (i.e. controlled and randomized clinical trials) that produce more reliable evidence of the effectiveness of psychosocial interventions for IV in children and adolescents in in the Latin American context

4D Lung MRI With High-Isotropic-Resolution Using Half-Spoke (Ute) and Full-Spoke 3D Radial Acquisition and Temporal Compressed Sensing Reconstruction

Objective: To develop a respiratory motion-resolved 4D MRI technique with high-isotropic-resolution (1.1 mm) using 3D radial sampling, camera-based respiratory motion sensing, and temporal compressed sensing reconstruction for lung cancer imaging. Approach: Free-breathing half- and full-spoke 3D golden-angle radial acquisitions were performed on eight healthy volunteers and eight patients with lung tumors of varying size. A back-and-forth k-space ordering between consecutive interleaves of the 3D radial acquisition was performed to minimize eddy current-related artifacts. Data were sorted into respiratory motion states using camera-based motion navigation and 4D images were reconstructed using temporal compressed sensing to reduce scan time. Normalized sharpness indices of the diaphragm, apparent signal-to-noise ratio (aSNR) and contrast-to-noise ratio (CNR) of the lung tumor (patients only), liver, and aortic arch were compared between half- and full-spoke 4D MRI images to evaluate the impact of respiratory motion and image contrast on 4D MRI image quality. Respiration-induced changes in lung volumes and center of mass shifts were compared between half- and full-spoke 4D MRI measurements. In addition, the motion measurements from 4D MRI and the same-day 4D CT were presented in one of the lung tumor patients. Main Results: Half-spoke 4D MRI provides better visualization of the lung parenchyma, while full-spoke 4D MRI presents sharper diaphragm images and higher aSNR and CNR in the lung tumor, liver, and aortic arch. Lung volume changes and center of mass shifts measured by half- and full-spoke 4D MRI were not statistically different. For the patient with 4D MRI and same-day 4D CT, lung volume changes and center of mass shifts were generally comparable. Significance: This work demonstrates the feasibility of a motion-resolved 4D MRI technique with high-isotropic-resolution using 3D radial acquisition, camera-based respiratory motion sensing, and temporal compressed sensing reconstruction for treatment planning and motion monitoring in radiotherapy of lung cancer