title: Isocenter accuracy in frameless stereotactic radiotherapy using implanted fiducials.
abstract: OBJECTIVE
  The stereotactic radiotherapy (SRT) system verifies isocenter accuracy in patient space. In this study, we evaluate isocenter accuracy in frameless SRT using implanted cranial gold markers.
  
  
  METHODS
  We performed frameless SRT on 43 intracranial tumor patients between August 1997 and December 2000. The treatment technique was determined by the tumor shape and volume, and by the location of critical organs. The coordinates of anterior-posterior and lateral port film were inputted to ISOLOC software, which calculated (1) the couch moves translation distance required to bring the target point to the isocenter, and (2) the intermarker distance comparisons between the CT study and the treatment machine films. We evaluated the isocenter deviation based on the error between orthogonal film target coordinates and isocenter coordinates.
  
  
  RESULTS
  The mean treatment isocenter deviations (x, y, z) were -0.03, 0.14, and -0.04 mm, respectively. The systematic component isocenter standard deviations were 0.28, 0.31, and 0.35 mm (1 SD), respectively, and the random component isocenter standard deviations were 0.53, 0.52, and 0.50 mm (1 SD), respectively.
  
  
  CONCLUSIONS
  The isocenter accuracy in the frameless SRT-implanted fiducial system is highly reliable and is comparable to that of other stereotactic radiosurgery systems.
authors.affiliation: Department of Therapeutic Radiology, Chungnam National University, Taejon, South Korea.
authors.forename: Ki-Hwan
authors.initials: KH
authors.lastname: Kim
authors.forename: Moon-June
authors.initials: MJ
authors.lastname: Cho
authors.forename: Jun-Sang
authors.initials: JS
authors.lastname: Kim
authors.forename: Jae-Sung
authors.initials: JS
authors.lastname: Kim
authors.forename: Chang-Joon
authors.initials: CJ
authors.lastname: Song
authors.forename: Shi-Hun
authors.initials: SH
authors.lastname: Song
authors.forename: Seon-Hwan
authors.initials: SH
authors.lastname: Kim
authors.forename: Lee
authors.initials: L
authors.lastname: Myers
authors.forename: Yong-Eun
authors.initials: YE
authors.lastname: Kim
mesh_terms: D001921:Brain / Q000601:surgery*; D003287:Contrast Media; D016371:Cranial Irradiation / Q000295:instrumentation / Q000379:methods*; D006046:Gold; D006801:Humans; D007472:Iohexol / Q000031:analogs & derivatives*; D019300:Medical Errors / Q000517:prevention & control; D008863:Microspheres; D019736:Prostheses and Implants; D016634:Radiosurgery / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation*; D015203:Reproducibility of Results; D013238:Stereotaxic Techniques / Q000295:instrumentation*; D016683:Supine Position; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media; D007472:Iohexol; C038192:iopromide; D006046:Gold