title: Diffusion tensor imaging (DTI) and colored fractional anisotropy (FA) mapping of the subthalamic nucleus (STN) and the globus pallidus interna (GPi).
abstract: BACKGROUND
  The subthalamic nucleus (STN) and the globus pallidus internus (GPi) are the most common surgical targets for the treatment of Parkinson's disease. We studied directionally colored fractional anisotropy (FA) and diffusion tensor imaging (DTI) sequences to better target these anatomical regions.
  
  
  METHODS
  Four patients undergoing stereotactic surgery for movement disorders were studied. Stereotactic targets and fiber tractography were determined on MRIs using the Schaltenbrand-Wahren atlas for definition in the iPlan software. In addition, post-operative imaging was fused to preoperative FA sequences for end-result identification. Axial, sagittal, and coronal images of the FA sequence were studied. DTI parameters used ranged from 2 to 4 mm for voxel size in the x/y/z planes, fiber length was kept constant at 15 mm and FA threshold of 0.25.
  
  
  RESULTS
  Colored FA maps resulted in a key signature in and around the STN and GPi. Regions identified include, but were not limited to: the internal capsule, nigral projections, the thalamic fasciculus, Forel's fields H1 and H2, zona incerta, suthalamic fasciculus, tegmental tracts, and cerebello-rubro-thalamic tract.
  
  
  CONCLUSIONS
  Colored FA maps allow a potential method to identify the STN and GPi accurately. DTI has proven to be a powerful tool that can be used to augment identification of the STN nucleus and GPi used for stereotactic surgery.
authors.affiliation: Department of Neurosurgery, University of California Los Angeles, 90095, USA. msedrak@gmail.com
authors.forename: Mark
authors.initials: M
authors.lastname: Sedrak
authors.forename: Alessandra
authors.initials: A
authors.lastname: Gorgulho
authors.forename: Ausaf
authors.initials: A
authors.lastname: Bari
authors.forename: Eric
authors.initials: E
authors.lastname: Behnke
authors.forename: Andrew
authors.initials: A
authors.lastname: Frew
authors.forename: Inga
authors.initials: I
authors.lastname: Gevorkyan
authors.forename: Nader
authors.initials: N
authors.lastname: Pouratian
authors.forename: Antonio
authors.initials: A
authors.lastname: DeSalles
mesh_terms: D016880:Anisotropy; D001931:Brain Mapping / Q000379:methods*; D046690:Deep Brain Stimulation / Q000379:methods*; D056324:Diffusion Tensor Imaging / Q000379:methods*; D004558:Electric Stimulation / Q000379:methods; D005917:Globus Pallidus / Q000033:anatomy & histology / Q000601:surgery*; D006801:Humans; D008839:Microelectrodes; D011300:Preoperative Care / Q000379:methods*; D012189:Retrospective Studies; D013238:Stereotaxic Techniques / Q000295:instrumentation; D020531:Subthalamic Nucleus / Q000033:anatomy & histology / Q000601:surgery*