Browsing by Author "García Saborit, Marisleydis"

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    Quantitative Susceptibility Mapping MRI in Deep-Brain Nuclei in First-Episode Psychosis
    (2023) García Saborit, Marisleydis; Jara Vallejos, Alejandro Antonio; Muñoz Camelo, Néstor Andrés; Milovic, Carlos; Tepper, Angeles; Alliende Correa, Luz María; Mena, Carlos; Iruretagoyena Bruce, Bárbara Arantzazu; Ramírez Mahaluf, Juan Pablo; Diaz, Camila; Nachar, Rubén; Castaneda, Carmen Paz; Gonzalez, Alfonso; Undurraga, Juan; Crossley, Nicolás; Tejos Núñez, Cristián Andrés
    Background Psychosis is related to neurochemical changes in deep-brain nuclei, particularly suggesting dopamine dysfunctions. We used an magnetic resonance imaging-based technique called quantitative susceptibility mapping (QSM) to study these regions in psychosis. QSM quantifies magnetic susceptibility in the brain, which is associated with iron concentrations. Since iron is a cofactor in dopamine pathways and co-localizes with inhibitory neurons, differences in QSM could reflect changes in these processes. Methods We scanned 83 patients with first-episode psychosis and 64 healthy subjects. We reassessed 22 patients and 21 control subjects after 3 months. Mean susceptibility was measured in 6 deep-brain nuclei. Using linear mixed models, we analyzed the effect of case-control differences, region, age, gender, volume, framewise displacement (FD), treatment duration, dose, laterality, session, and psychotic symptoms on QSM. Results Patients showed a significant susceptibility reduction in the putamen and globus pallidus externa (GPe). Patients also showed a significant R2* reduction in GPe. Age, gender, FD, session, group, and region are significant predictor variables for QSM. Dose, treatment duration, and volume were not predictor variables of QSM. Conclusions Reduction in QSM and R2* suggests a decreased iron concentration in the GPe of patients. Susceptibility reduction in putamen cannot be associated with iron changes. Since changes observed in putamen and GPe were not associated with symptoms, dose, and treatment duration, we hypothesize that susceptibility may be a trait marker rather than a state marker, but this must be verified with long-term studies.
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    Studying psychiatric diseases using quantitative susceptibility mapping (QSM)
    (2025) García Saborit, Marisleydis; Tejos Nuñez, Cristián Andrés; Pontificia Universidad Católica de Chile. Escuela de Ingeniería
    Quantitative Susceptibility Mapping (QSM), a sophisticated MRI-based technique for quantifying brain magnetic susceptibility, has emerged as a valuable tool in exploring neurodegenerative diseases and, more recently, psychiatric disorders such as first-episode schizophrenia, depression, anxiety, and stress. This method allows the measurement of magnetic susceptibilities in various tissues, unveiling associations with diverse phenotypes like body iron, blood assays, diet, and alcohol consumption. Furthermore, investigations into genetic variations across the genome have revealed intriguing links between magnetic susceptibility and clusters of genes responsible for crucial biological functions, including iron regulation, calcium mechanisms, myelin development, and the extracellular matrix.Our primary objective in this thesis is to study associations between psychiatric illnesses and iron content in the gray matter nucleus utilizing QSM. In pursuit of this goal, we conducted two comprehensive analyses involving cohorts of first-episode psychosis patients from Chile and individuals with psychotic-like experiences from the UK biobank. The study scrutinized QSM and R2* differences in gray brain nuclei between patients and controls, employing linear mixed models to explore associations with demographic and clinical variables and genetic factors. Notably, the incorporation of polygenic risk scores (PGS) for psychotic-like experiences in our statistical analyses yielded significant differences in QSM and R2∗ rates between patients and control subjects. Organized into six chapters, our thesis begins with an introduction to the characteristics of psychotic diseases and image biomarkers. Subsequent chapters delve into the theoretical framework linking psychiatric disorders with magnetic susceptibility, detail the methodology employed, present the results, discuss the findings, and conclude with overarching insights. Our findings demonstrate that QSM serves as a powerful tool that may help to elucidate the neurophysiological processes in psychosis and their relationship with iron metabolism. Finally, the proposed methods contribute valuable insights to our current understanding and offer promising image biomarkers for ongoing and future psychiatric research.