title: Subthalamic nuclear tissue contrast in inversion recovery MRI decreases with age in medically refractory Parkinson's disease.
abstract: OBJECTIVE
  MRI appearance of subthalamic nucleus (STN) boundaries in Parkinson's patients is often unreliable and not well understood. An objective comparison between FSE T2 and inversion recovery (FSTIR) sequences for stereotactic placement of deep brain stimulators is presented to advance current understanding of STN tissue contrast for refractory Parkinson's disease (PD).
  
  
  METHODS
  We imaged 12 PD (age 53-82) and 12 control patients (age 48-77) using T2 and FSTIR sequences at 1.5 T. To avoid MR contrast variation from hardware and patient dependent sources we used an internal thalamic tissue standard to normalize STN signal intensity and correlated it with patient age for these two groups.
  
  
  RESULTS
  Normalized FSTIR-weighted STN contrast decreased with increasing age for PD patients (Spearman Rank correlation = -.5) while remained virtually unchanged for controls with age (Spearman Rank coefficient ≈ 0). T2-weighted STN contrast did not show appreciable changes with age for both the groups (Spearman correlation ≈ -.1).
  
  
  CONCLUSIONS
  STN, a common stimulation target, shows an age dependent trend for normalized FSTIR MRI contrast. Although larger patient pools are needed, our work points to tissue relaxation-based changes in STN that may provide insight in early stages of brain pathology involving DBS targets in medically refractory Parkinson's disease.
authors.affiliation: Department of Radiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, 02215.
authors.forename: Subhendra N
authors.initials: SN
authors.lastname: Sarkar
authors.affiliation: School of Medicine, University of Texas Health Science Center, San Antonio, TX, 78229.
authors.forename: Pooja R
authors.initials: PR
authors.lastname: Sarkar
authors.affiliation: Division of Neurosurgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, 02215.
authors.forename: Efstathios
authors.initials: E
authors.lastname: Papavassiliou
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000473:pathology*; D002908:Chronic Disease; D004599:Electric Stimulation Therapy; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000473:pathology* / Q000628:therapy; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D020531:Subthalamic Nucleus / Q000473:pathology*; D017211:Treatment Failure
keywords: DBS MRI; FSTIR; STN; Subthalamic nucleus; deep brain stimulation; refractory parkinson's disease