title: Optimal MRI methods for direct stereotactic targeting of the subthalamic nucleus and globus pallidus.
abstract: OBJECTIVE
  Reliable identification of the subthalamic nucleus (STN) and globus pallidus interna (GPi) is critical for deep brain stimulation (DBS) of these structures. The purpose of this study was to compare the visibility of the STN and GPi with various MRI techniques and to assess the suitability of each technique for direct stereotactic targeting.
  
  
  METHODS
  MR images were acquired from nine volunteers with T2- and proton density-weighted (PD-W) fast spin echo, susceptibility-weighted imaging (SWI), phase-sensitive inversion recovery and quantitative T1, T2 and T2* mapping sequences. Contrast-to-noise ratios (CNR) for the STN and GPi were calculated for all sequences. Targeting errors on SWI were evaluated on magnetic susceptibility maps. The sequences demonstrating the best conspicuity of DBS target structures (SWI and T2*) were then applied to ten patients with movement disorders, and the CNRs for these techniques were assessed.
  
  
  RESULTS
  SWI offers the highest CNR for the STN, but standard PD-W images provide the best CNR for the pallidum. Susceptibility maps indicated that the GPi margins may be shifted slightly on SWI, although no shifts were seen for the STN.
  
  
  CONCLUSIONS
  SWI may improve the visibility of the STN on pre-operative MRI, potentially improving the accuracy of direct stereotactic targeting.
authors.affiliation: Department of Neuroradiology, King's College Hospital, Denmark Hill, London, SE5 9RS, UK. ruth.ogorman@kcl.ac.uk
authors.forename: Ruth L
authors.initials: RL
authors.lastname: O'Gorman
authors.forename: Karin
authors.initials: K
authors.lastname: Shmueli
authors.forename: Keyoumars
authors.initials: K
authors.lastname: Ashkan
authors.forename: Michael
authors.initials: M
authors.lastname: Samuel
authors.forename: David J
authors.initials: DJ
authors.lastname: Lythgoe
authors.forename: Asal
authors.initials: A
authors.lastname: Shahidiani
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Wastling
authors.forename: Michelle
authors.initials: M
authors.lastname: Footman
authors.forename: Richard P
authors.initials: RP
authors.lastname: Selway
authors.forename: Jozef
authors.initials: J
authors.lastname: Jarosz
mesh_terms: D000328:Adult; D005260:Female; D005917:Globus Pallidus / Q000000981:diagnostic imaging*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D011859:Radiography; D012015:Reference Standards; D013238:Stereotaxic Techniques; D020531:Subthalamic Nucleus / Q000000981:diagnostic imaging*