title: Localization of the subthalamic nucleus: optimization with susceptibility-weighted phase MR imaging.
abstract: OBJECTIVE
  On clinical MR images, the subthalamic nuclei (STN) are poorly delineated from adjacent structures, impeding safe direct targeting for placement of electrodes in the treatment of Parkinson disease. Susceptibility-weighted MR phase imaging offers improved contrast and spatial resolution at reduced imaging times relative to clinically used T2-weighted spin-echo imaging for STN visualization. Our purpose was to assess STN visibility by using phase imaging, comparing phase and magnitude images obtained concurrently by using susceptibility-weighted imaging (SWI). The goal was to identify an efficient scanning protocol for high-quality phase images of STN.
  
  
  METHODS
  Seventy-eight SWI scans were acquired at 3T by using different TEs and acceleration factors. STN visibility and delimitation from adjacent structures were scored from 0 (not interpretable) to 5 (excellent). Regression analyses assessed the relationship of STN visibility to scanning parameters
  
  
  RESULTS
  STN were identified at all studied TEs on phase images. Visibility and delimitation of STN were consistently superior on phase images compared with magnitude images. Good visualization (score of >or=4) of STN on phase imaging occurred at a mean TE of 20.0 ms and a sensitivity encoding (SENSE) of 1.40. Scores of STN visualization on phase images were dependent on SENSE (P < .002) and TE (P < .031). Good delimitation of the STN on phase imaging occurred at a mean TE of 21.6 ms and a SENSE of 1.36.
  
  
  CONCLUSIONS
  Visualization and delimitation of STN was superior on phase images and was achieved at 3T in <2.5 minutes. A TE of 20 ms and an acceleration factor of <or=1.5 are recommended to visualize STN by using this method.
authors.affiliation: Department of Radiology, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: A T
authors.initials: AT
authors.lastname: Vertinsky
authors.forename: V A
authors.initials: VA
authors.lastname: Coenen
authors.forename: D J
authors.initials: DJ
authors.lastname: Lang
authors.forename: S
authors.initials: S
authors.lastname: Kolind
authors.forename: C R
authors.initials: CR
authors.lastname: Honey
authors.forename: D
authors.initials: D
authors.lastname: Li
authors.forename: A
authors.initials: A
authors.lastname: Rauscher
mesh_terms: D000328:Adult; D000465:Algorithms; D001185:Artificial Intelligence; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D016247:Information Storage and Retrieval / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010363:Pattern Recognition, Automated / Q000379:methods*; D011786:Quality Control; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D020531:Subthalamic Nucleus / Q000033:anatomy & histology*; D055815:Young Adult