title: A clinical comparison of patient setup and intra-fraction motion using frame-based radiosurgery versus a frameless image-guided radiosurgery system for intracranial lesions.
abstract: OBJECTIVE
  A comparison of patient positioning and intra-fraction motion using invasive frame-based radiosurgery with a frameless X-ray image-guided system utilizing a thermoplastic mask for immobilization.
  
  
  METHODS
  Overall system accuracy was determined using 57 hidden-target tests. Positioning agreement between invasive frame-based setup and image-guided (IG) setup, and intra-fraction displacement, was evaluated for 102 frame-based SRS treatments. Pre and post-treatment imaging was also acquired for 7 patients (110 treatments) immobilized with an aquaplast mask receiving fractionated IG treatment.
  
  
  RESULTS
  The hidden-target tests demonstrated a mean error magnitude of 0.7mm (SD=0.3mm). For SRS treatments, mean deviation between frame-based and image-guided initial positioning was 1.0mm (SD=0.5mm). Fusion failures were observed among 3 patients resulting in aberrant predicted shifts. The image-guidance system detected frame slippage in one case. The mean intra-fraction shift magnitude observed for the BRW frame was 0.4mm (SD=0.3mm) compared to 0.7mm (SD=0.5mm) for the fractionated patients with the mask system.
  
  
  CONCLUSIONS
  The overall system accuracy is similar to that reported for invasive frame-based SRS. The intra-fraction motion was larger with mask-immobilization, but remains within a range appropriate for stereotactic treatment. These results support clinical implementation of frameless radiosurgery using the Novalis Body Exac-Trac system.
authors.affiliation: Department of Radiation Oncology, Brigham and Women's Hospital and Dana Farber Cancer Institute, Boston, MA, USA. naren.ramakrishna@orhs.org
authors.forename: Naren
authors.initials: N
authors.lastname: Ramakrishna
authors.forename: Florin
authors.initials: F
authors.lastname: Rosca
authors.forename: Scott
authors.initials: S
authors.lastname: Friesen
authors.forename: Evrim
authors.initials: E
authors.lastname: Tezcanli
authors.forename: Piotr
authors.initials: P
authors.lastname: Zygmanszki
authors.forename: Fred
authors.initials: F
authors.lastname: Hacker
mesh_terms: D001932:Brain Neoplasms / Q000000981:diagnostic imaging / Q000601:surgery*; D006801:Humans; D019047:Phantoms, Imaging; D016634:Radiosurgery / Q000379:methods*; D014057:Tomography, X-Ray Computed