title: Intra- and interfractional patient motion for a variety of immobilization devices.
abstract: The magnitude of inter- and intrafractional patient motion has been assessed for a broad set of immobilization devices. Data was analyzed for the three ordinal directions--left-right (x), sup-inf (y), and ant-post (z)--and the combined spatial displacement. We have defined "rigid" and "non-rigid" immobilization devices depending on whether they could be rigidly and reproducibly connected to the treatment couch or not. The mean spatial displacement for intrafractional motion for rigid devices is 1.3 mm compared to 1.9 mm for nonrigid devices. The modified Gill-Thomas-Cosman frame performed best at controlling intrafractional patient motion, with a 95% probability of observing a three-dimensional (3D) vector length of motion (v95) of less than 1.8 mm, but could not be evaluated for interfractional motion. All other rigid and nonrigid immobilization devices had a v95 of more than 3 mm for intrafractional patient motion. Interfractional patient motion was only evaluated for the rigid devices. The mean total interfractional displacement was at least 3.0 mm for these devices while v95 was at least 6.0 mm.
authors.affiliation: Northeast Proton Therapy Center, Massachusetts General Hospital and Department of Radiation Oncology, Harvard Medical School, 55 Fruit Street, Boston, Massachusetts 02114, USA.
authors.forename: Martijn
authors.initials: M
authors.lastname: Engelsman
authors.forename: Stanley J
authors.initials: SJ
authors.lastname: Rosenthal
authors.forename: Susan L
authors.initials: SL
authors.lastname: Michaud
authors.forename: Judith A
authors.initials: JA
authors.lastname: Adams
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Schneider
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Bradley
authors.forename: Jacob B
authors.initials: JB
authors.lastname: Flanz
authors.forename: Hanne M
authors.initials: HM
authors.lastname: Kooy
mesh_terms: D000465:Algorithms; D004867:Equipment Design; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D007103:Immobilization / Q000379:methods*; D009038:Motion; D009068:Movement; D011187:Posture; D011522:Protons; D011878:Radiotherapy / Q000295:instrumentation* / Q000379:methods*; D015203:Reproducibility of Results; D012149:Restraint, Physical
chemical_list: D011522:Protons