title: T1 Relaxation Rate (R1) Indicates Nonlinear Mn Accumulation in Brain Tissue of Welders With Low-Level Exposure.
abstract: Although the essential element manganese (Mn) is neurotoxic at high doses, the effects of lower exposure are unclear. MRI T1-weighted (TIW) imaging has been used to estimate brain Mn exposure via the pallidal index (PI), defined as the T1W intensity ratio in the globus pallidus (GP) versus frontal white matter (FWM). PI may not, however, be sensitive to Mn in GP because Mn also may accumulate in FWM. This study explored: (1) whether T1 relaxation rate (R1) could quantify brain Mn accumulation more sensitively; and (2) the dose-response relationship between estimated Mn exposure and T1 relaxation rate (R1). Thirty-five active welders and 30 controls were studied. Occupational questionnaires were used to estimate hours welding in the past 90 days (HrsW) and lifetime measures of Mn exposure. T1W imaging and T1-measurement were utilized to generate PI and R1 values in brain regions of interest (ROIs). PI did not show a significant association with any measure of Mn and/or welding-related exposure. Conversely, in several ROIs, R1 showed a nonlinear relationship to HrsW, with R1 signal increasing only after a critical exposure was reached. The GP had the greatest rate of Mn accumulation. Welders with higher exposure showed significantly higher R1 compared either with controls or with welders with lower exposure. Our data are additional evidence that Mn accumulation can be assessed more sensitively by R1 than by PI. Moreover, the nonlinear relationship between welding exposure and Mn brain accumulation should be considered in future studies and policies.
authors.affiliation: *Department of Neurology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania.
authors.forename: Eun-Young
authors.initials: EY
authors.lastname: Lee
authors.affiliation: Department of Environmental Sciences and Engineering, School of Public Health, University of North Carolina, Chapel Hill, North Carolina.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Flynn
authors.affiliation: *Department of Neurology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania.
authors.forename: Guangwei
authors.initials: G
authors.lastname: Du
authors.affiliation: *Department of Neurology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, Department of Pharmacology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania.
authors.forename: Mechelle M
authors.initials: MM
authors.lastname: Lewis
authors.affiliation: Department of Environmental Sciences and Engineering, School of Public Health, University of North Carolina, Chapel Hill, North Carolina.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Fry
authors.affiliation: Department of Biostatistics, School of Public Health, University of North Carolina, Chapel Hill, North Carolina.
authors.forename: Amy H
authors.initials: AH
authors.lastname: Herring
authors.affiliation: Department of Biostatistics, School of Public Health, University of North Carolina, Chapel Hill, North Carolina.
authors.forename: Eric
authors.initials: E
authors.lastname: Van Buren
authors.affiliation: Department of Biostatistics, School of Public Health, University of North Carolina, Chapel Hill, North Carolina.
authors.forename: Scott
authors.initials: S
authors.lastname: Van Buren
authors.affiliation: Department of Environmental Sciences and Engineering, School of Public Health, University of North Carolina, Chapel Hill, North Carolina.
authors.forename: Lisa
authors.initials: L
authors.lastname: Smeester
authors.affiliation: Department of Public Health Sciences, Pennsylvania State University, Hershey, Pennsylvania and.
authors.forename: Lan
authors.initials: L
authors.lastname: Kong
authors.affiliation: Departments of Radiology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania.
authors.forename: Qing
authors.initials: Q
authors.lastname: Yang
authors.affiliation: *Department of Neurology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, Department of Pharmacology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania.
authors.forename: Richard B
authors.initials: RB
authors.lastname: Mailman
authors.affiliation: *Department of Neurology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, Department of Pharmacology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, Departments of Radiology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, Department of Kinesiology, Pennsylvania State University, University Park, Pennsylvania Xuemei@psu.edu.
authors.forename: Xuemei
authors.initials: X
authors.lastname: Huang
mesh_terms: D000328:Adult; D001921:Brain / Q000378:metabolism*; D016022:Case-Control Studies; D006801:Humans; D008274:Magnesium / Q000378:metabolism*; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D016273:Occupational Exposure; D014896:Welding
chemical_list: D008274:Magnesium
keywords: MRI; R1; manganese; pallidal index; welders