Abstract: Objective We examined typical changes in hippocampus volume and metabolite ratios in the workers chronically exposed to lead,and compared with those of control individuals, using magnetic resonance imaging (MRI ) and proton magnetic resonance spectroscopy (1 H-MRS),then,investigated whether an abnormality in brain capacity or metabolism associated with memory changes.Methods The subj ects included 8 workers chronically exposed to lead (j ob years 6-37)and 8 gender age and matched healthy people,MRS was used in the related region of the brain to detect N-acetyl aspartate(NAA),lipid(Lip),choline(Cho),glutamate and glutamine (Glx),Lactate(Lac)and myoinositol(mI)levels,and each item was expressed respectively as a ratio to creatine and phosphocreatine (Cr).We also assessed the hippocampus volume on 3D T1-weighted MRI.Neurobehavioral tests were also performed to define memory status.Results NAA/Cr ratio in the frontal lobe,basal ganglia and hippocampus,MI/Cr ratio in basal ganglia and hippocampus,and the hippocampal volume were significantly different to those of control subj ects (P < 0.05 ).For the workers conformed lead poisoned,the blood lead concentration was significantly correlated with MI/Cr ratio,NAA/Cr ratio in the hippocampus as well as hippocampus volume (P<0.05 ).Conclusion Occupational exposure to lead may cause subtle structural and functional alteration in human brains,which may be one reason of memory lost.

Key words: lead poisoing, nervous system, adult, magnetic reonance imaging, magnetic resonance spectroscopy