Browsing by Subject "R1 mapping"

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    Subject-Specific Mapping of Excess Manganese Accumulation in the Brain of Welders Using Magnetic Resonance Imaging Relaxometry
    (MDPI, 2025-02-25) Monsivais, Humberto; Dydak, Ulrike; Radiology and Imaging Sciences, School of Medicine
    Chronic overexposure to manganese (Mn) can occur in occupational settings, such as welding, leading to increased Mn levels in the brain. Excess brain Mn accumulation may result in neurotoxicity, which is characterized by Parkinsonian-like symptoms including motor and cognitive dysfunctions. In this work, we demonstrate a novel methodology for personalized diagnosis and spatial characterization of abnormal Magnetic Resonance Imaging R1 (R1 = 1/T1) relaxation rates arising from excessive Mn accumulation in welders' brains. Utilizing voxel-wise population-derived norms based on a frequency age-matched non-exposed group (n = 25), we demonstrate the ability to conduct subject-specific assessments and mapping of Mn exposure using MRI relaxometry. Our results show elevated R1 in multiple brain regions in individual welders, but also extreme between-subject variability in Mn accumulation, debasing the concept that high exposures correlate with uniformly high Mn deposition in the brain. Consequently, the presented personalized methodology serves as a counterpart to group-based comparison, which allows for understanding the level of individual exposure and the toxicokinetics of Mn accumulation. This work lays a foundation for improved occupational health assessments and preventive measures against neurotoxic metal exposure.
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    Whole-brain mapping of increased manganese levels in welders and its association with exposure and motor function
    (Elsevier, 2024) Monsivais, Humberto; Yeh, Chien-Lin; Edmondson, Alex; Harold, Roslyn; Snyder, Sandy; Wells, Ellen M.; Schmidt-Wilcke, Tobias; Foti, Dan; Zauber, S. Elizabeth; Dydak, Ulrike; Neurology, School of Medicine
    Although manganese (Mn) is a trace metal essential for humans, chronic exposure to Mn can cause accumulation of this metal ion in the brain leading to an increased risk of neurological and neurobehavioral health effects. This is a concern for welders exposed to Mn through welding fumes. While brain Mn accumulation in occupational settings has mostly been reported in the basal ganglia, several imaging studies also revealed elevated Mn in other brain areas. Since Mn functions as a magnetic resonance imaging (MRI) T1 contrast agent, we developed a whole-brain MRI approach to map in vivo Mn deposition differences in the brains of non-exposed factory controls and exposed welders. This is a cross-sectional analysis of 23 non-exposed factory controls and 36 exposed full-time welders from the same truck manufacturer. We collected high-resolution 3D MRIs of brain anatomy and R1 relaxation maps to identify regional differences using voxel-based quantification (VBQ) and statistical parametric mapping. Furthermore, we investigated the associations between excess Mn deposition and neuropsychological and motor test performance. Our results indicate that: (1) Using whole-brain MRI relaxometry methods we can generate excess Mn deposition maps in vivo, (2) excess Mn accumulation due to occupational exposure occurs beyond the basal ganglia in cortical areas associated with motor and cognitive functions, (3) Mn likely diffuses along white matter tracts in the brain, and (4) Mn deposition in specific brain regions is associated with exposure (cerebellum and frontal cortex) and motor metrics (cerebellum and hippocampus).