title: Quantitative susceptibility mapping of the midbrain in Parkinson's disease.
abstract: BACKGROUND
  Parkinson's disease (PD) is marked pathologically by dopamine neuron loss and iron overload in the substantia nigra pars compacta. Midbrain iron content is reported to be increased in PD based on magnetic resonance imaging (MRI) R2* changes. Because quantitative susceptibility mapping is a novel MRI approach to measure iron content, we compared it with R2* for assessing midbrain changes in PD.
  
  
  METHODS
  Quantitative susceptibility mapping and R2* maps were obtained from 47 PD patients and 47 healthy controls. Midbrain susceptibility and R2* values were analyzed by using both voxel-based and region-of-interest approaches in normalized space, and analyzed along with clinical data, including disease duration, Unified Parkinson's Disease Rating Scale (UPDRS) I, II, and III subscores, and levodopa-equivalent daily dosage. All studies were done while PD patients were "on drug."
  
  
  RESULTS
  Compared with controls, PD patients showed significantly increased susceptibility values in both right (cluster size = 106 mm(3)) and left (164 mm(3)) midbrain, located ventrolateral to the red nucleus that corresponded to the substantia nigra pars compacta. Susceptibility values in this region were correlated significantly with disease duration, UPDRS II, and levodopa-equivalent daily dosage. Conversely, R2* was increased significantly only in a much smaller region (62 mm(3)) of the left lateral substantia nigra pars compacta and was not significantly correlated with clinical parameters.
  
  
  CONCLUSIONS
  The use of quantitative susceptibility mapping demonstrated marked nigral changes that correlated with clinical PD status more sensitively than R2*. These data suggest that quantitative susceptibility mapping may be a superior imaging biomarker to R2* for estimating brain iron levels in PD.
authors.affiliation: Department of Neurology, Penn State University-Milton S. Hershey Medical Center, Hershey, Pennsylvania, United States.
authors.forename: Guangwei
authors.initials: G
authors.lastname: Du
authors.affiliation: MedImageMetric LLC, New York, New York, United States.
authors.forename: Tian
authors.initials: T
authors.lastname: Liu
authors.affiliation: Department of Neurology, Penn State University-Milton S. Hershey Medical Center, Hershey, Pennsylvania, United States.|Department of Pharmacology, Penn State University-Milton S. Hershey Medical Center, Hershey, Pennsylvania, United States.
authors.forename: Mechelle M
authors.initials: MM
authors.lastname: Lewis
authors.affiliation: Department of Public Health Sciences, Penn State University-Milton S. Hershey Medical Center, Hershey, Pennsylvania, United States.
authors.forename: Lan
authors.initials: L
authors.lastname: Kong
authors.affiliation: Department of Radiology, Weill Cornell Medical College, New York, New York, United States.
authors.forename: Yi
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Neurosurgery, Penn State University-Milton S. Hershey Medical Center, Hershey, Pennsylvania, United States.
authors.forename: James
authors.initials: J
authors.lastname: Connor
authors.affiliation: Department of Neurology, Penn State University-Milton S. Hershey Medical Center, Hershey, Pennsylvania, United States.|Department of Pharmacology, Penn State University-Milton S. Hershey Medical Center, Hershey, Pennsylvania, United States.
authors.forename: Richard B
authors.initials: RB
authors.lastname: Mailman
authors.affiliation: Department of Neurology, Penn State University-Milton S. Hershey Medical Center, Hershey, Pennsylvania, United States.|Department of Pharmacology, Penn State University-Milton S. Hershey Medical Center, Hershey, Pennsylvania, United States.|Department of Neurosurgery, Penn State University-Milton S. Hershey Medical Center, Hershey, Pennsylvania, United States.|Department of Radiology, Penn State University-Milton S. Hershey Medical Center, Hershey, Pennsylvania, United States.|Department of Kinesiology, Penn State University-Milton S. Hershey Medical Center, Hershey, Pennsylvania, United States.
authors.forename: Xuemei
authors.initials: X
authors.lastname: Huang
mesh_terms: D000368:Aged; D015415:Biomarkers / Q000032:analysis; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007501:Iron / Q000378:metabolism; D007980:Levodopa / Q000627:therapeutic use; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008636:Mesencephalon / Q000187:drug effects* / Q000378:metabolism; D008875:Middle Aged; D010300:Parkinson Disease / Q000188:drug therapy* / Q000378:metabolism
chemical_list: D015415:Biomarkers; D007980:Levodopa; D007501:Iron
keywords: Parkinson's disease; iron; magnetic resonance imaging; quantitative susceptibility mapping; substantia nigra