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Analysis of Manganese Accumulation in the Pituitary Gland and Hippocampus of Smelters Using High Resolution 3-D T1-Weighted MRI

Chronic exposure to excessive manganese (Mn) has neurotoxic eff ects, which can lead to behavioral and motor defi cits. Overexposure to Mn may occur in the smelting and welding industries, and previous studies have found signifi cant Mn accumulation in the basal ganglia of exposed populations using Magnetic Resonance Imaging (MRI). MRI can identify Mn accumulation in the brain because Mn acts as a contrast agent, increasing the signal in T1-weighted images. This study investigates brain Mn accumulation in the pituitary gland and hippocampus. High-resolution 3-D T1-weighted images from a former study on 10 Mn ore smelters and 10 controls with no history of exposure were analyzed. 3-D volumes of interest (VOI) were placed in the pituitary gland and right and left hippocampi. A separate VOI was placed in the neck muscle as an internal reference. The relative signal intensity for each region was determined by calculating the ratio of the brain region to the neck, which represents the relative Mn accumulation in that region. Group diff erences were tested using linear regression.