title: Repositioning accuracy: comparison of a noninvasive head holder with thermoplastic mask for fractionated radiotherapy and a case report.
abstract: OBJECTIVE
  To compare accuracy, clinical feasibility, and subjective patient impression between a noninvasive head holder (Vogele Bale Hohner [VBH]; Wellhoefer Dosimetry, Schwarzenbruck, Germany) developed at the University of Innsbruck and the thermoplastic mask fixation system for use in fractionated external radiotherapy. We present a case report of an actual patient fixated in the VBH head holder during radiation therapy.
  
  
  METHODS
  The VBH head holder consists of an individualized vacuum dental cast connected to a head plate via two hydraulic arms allowing noninvasive, reproducible head fixation of even uncooperative patients. Accuracy was tested and compared with that of the thermoplastic mask using the Phillips EasyGuide navigation system on five volunteers. Specific external registration points served as landmarks and their positions were compared after each repositioning. System and operator inaccuracy were also taken into account. The times taken for production and repositioning of the respective fixation devices were compared, and subjective impressions were noted.
  
  
  RESULTS
  Mean VBH head holder repositioning accuracy was 1.02 mm while that of the thermoplastic mask was 3.05 mm. 69% of mask repositionings showed a deviation > 2 mm and 41% > 3 mm (as opposed to 8% and 1% respectively for the VBH head holder) Those points located farthest away from the respective plane of fixation showed the largest deviations. Both production and repositioning times were similar between the systems; depending upon the patient, the VBH head holder was generally better tolerated than the mask system.
  
  
  CONCLUSIONS
  Due to its significantly better repositioning accuracy compared to that of the thermoplastic mask, the VBH head holder is especially suited for external radiation requiring precise repositioning due to critical tissues in immediate surrounding of the area to be irradiated.
authors.affiliation: Department of Radiotherapy-Radiooncology, University Hospital Innsbruck, Austria.
authors.forename: R
authors.initials: R
authors.lastname: Sweeney
authors.forename: R
authors.initials: R
authors.lastname: Bale
authors.forename: M
authors.initials: M
authors.lastname: Vogele
authors.forename: M
authors.initials: M
authors.lastname: Nevinny-Stickel
authors.forename: A
authors.initials: A
authors.lastname: Bluhm
authors.forename: T
authors.initials: T
authors.lastname: Auer
authors.forename: G
authors.initials: G
authors.lastname: Hessenberger
authors.forename: P
authors.initials: P
authors.lastname: Lukas
mesh_terms: D000328:Adult; D003528:Carcinoma, Adenoid Cystic / Q000532:radiotherapy*; D003760:Dental Impression Materials; D003761:Dental Impression Technique; D019583:Dose Fractionation, Radiation; D004867:Equipment Design; D006257:Head; D006801:Humans; D007103:Immobilization; D008297:Male; D009064:Mouth Protectors; D010255:Paranasal Sinus Neoplasms / Q000532:radiotherapy*; D015203:Reproducibility of Results; D013101:Sphenoid Sinus
chemical_list: D003760:Dental Impression Materials