title: A new head holder for reducing axial movement and repositioning errors during physiological CT imaging.
abstract: OBJECTIVE
  We designed a new head holder for immobilization and repositioning in dynamic CT studies of the brain.
  
  
  METHODS
  A customized thermoplastic face mask and foam head rest were made to restrict movement of the head in all directions, but particularly out of the axial plane (z-movement).
  
  
  RESULTS
  This design provided a rigid, detailed mold of the face and back of the head that minimized motion during lengthy CT studies and enabled accurate repositioning of the head for follow-up studies. Markers applied directly to the skin were used to quantify z-movement.
  
  
  CONCLUSIONS
  When tested on 12 subjects, immobilization was limited to < 2.0 mm under worst-case conditions when the subject was asked to attempt forced movements. Repositioning was accurate to < 1.5 mm when the subject was removed from the head holder and then placed back into it.
authors.affiliation: Department of Biomedical Engineering, IL 60201.
authors.forename: S
authors.initials: S
authors.lastname: Shrawder
authors.forename: G D
authors.initials: GD
authors.lastname: Lapin
authors.forename: C V
authors.initials: CV
authors.lastname: Allen
authors.forename: N A
authors.initials: NA
authors.lastname: Vick
authors.forename: D R
authors.initials: DR
authors.lastname: Groothuis
mesh_terms: D001921:Brain / Q000000981:diagnostic imaging; D002266:Carboxymethylcellulose Sodium; D004867:Equipment Design; D005500:Follow-Up Studies; D006257:Head / Q000033:anatomy & histology*; D006801:Humans; D007103:Immobilization; D008397:Masks; D020366:Methylmethacrylate; D008768:Methylmethacrylates; D009068:Movement; D011137:Polystyrenes; D011140:Polyurethanes; D011187:Posture; D011336:Probability; D011858:Radiographic Magnification; D012149:Restraint, Physical / Q000295:instrumentation*; D012867:Skin; D014057:Tomography, X-Ray Computed / Q000295:instrumentation*
chemical_list: D008768:Methylmethacrylates; D011137:Polystyrenes; D011140:Polyurethanes; D020366:Methylmethacrylate; C024075:styrofoam; D002266:Carboxymethylcellulose Sodium