title: A method to estimate the spatial extent of activation in thalamic deep brain stimulation.
abstract: OBJECTIVE
  The goal of this study was to develop, evaluate, and apply a method to quantify the unknown spatial extent of activation in deep brain stimulation (DBS) of the ventral intermedius nucleus (Vim) of the thalamus.
  
  
  METHODS
  The amplitude-distance relationship and the threshold amplitudes to elicit clinical responses were combined to estimate the unknown amplitude-distance constant and the distance between the electrode and the border between the Vim and the ventrocaudal nucleus (Vc) of the thalamus. We tested the sensitivity of the method to errors in the input parameters, and subsequently applied the method to estimate the amplitude-distance constant from clinically-measured threshold amplitudes.
  
  
  RESULTS
  The method enabled estimation of the amplitude-distance constant with a median squared error of 0.07-0.23V/mm2 and provided an estimate of the distance between the electrode and the Vc/Vim border with a median squared error of 0.01-0.04mm. Application of the method to clinically-measured threshold amplitudes to elicit paresthesias estimated the amplitude-distance constant to be 0.22V/mm2.
  
  
  CONCLUSIONS
  The method enabled robust quantification of the spatial extent of activation in thalamic DBS and predicted that stimulation amplitudes of 1-3.5V would produce a mean effective radius of activation of 2.0-3.9mm.
  
  
  CONCLUSIONS
  Knowing the spatial extent of activation may improve methods of electrode placement and stimulation parameter selection in DBS.
authors.affiliation: Department of Biomedical Engineering, Duke University, Hudson Hall 136, Box 90281, Durham, NC 27708-0281, USA.
authors.forename: Alexis M
authors.initials: AM
authors.lastname: Kuncel
authors.forename: Scott E
authors.initials: SE
authors.lastname: Cooper
authors.forename: Warren M
authors.initials: WM
authors.lastname: Grill
mesh_terms: D003198:Computer Simulation; D046690:Deep Brain Stimulation / Q000295:instrumentation* / Q000379:methods*; D004056:Differential Threshold / Q000502:physiology; D004307:Dose-Response Relationship, Radiation; D004566:Electrodes; D005069:Evaluation Studies as Topic; D007839:Functional Laterality; D006801:Humans; D008954:Models, Biological; D013788:Thalamus / Q000502:physiology* / Q000528:radiation effects*