title: Validating fiducial markers for image-guided radiation therapy for accelerated partial breast irradiation in early-stage breast cancer.
abstract: OBJECTIVE
  Image-guided radiation therapy (IGRT) may be beneficial for accelerated partial breast irradiation (APBI). The goal was to validate the use of intraparenchymal textured gold fiducials in patients receiving APBI.
  
  
  METHODS
  Twenty-six patients were enrolled on this prospective study that had three or four textured gold intraparenchymal fiducials placed at the periphery of the lumpectomy cavity and were treated with three-dimensional (3D) conformal APBI. Free-breathing four-dimensional computed tomography image sets were obtained pre- and posttreatment, as were daily online megavoltage (MV) orthogonal images. Intrafraction motion, variations in respiratory motion, and fiducial marker migration were calculated using the 3D coordinates of individual fiducials and a calculated center of mass (COM) of the fiducials. We also compared the relative position of the fiducial COM with the geometric center of the seroma.
  
  
  RESULTS
  There was less than 1 mm of intrafraction respiratory motion, variation in respiratory motion, or fiducial marker migration. The change in seroma position relative to the fiducial COM was 1 mm ± 1 mm. The average position of the geometric seroma relative to the fiducial COM pretreatment compared with posttreatment was 1 mm ± 1 mm. The largest daily variation in displacement when using bony landmark was in the anteroposterior direction and two standard deviations (SD) of this variation was 10 mm. The average variation in daily separation between the fiducial pairs from daily MV images was 3 mm ± 3 mm therefore 2 SD is 6 mm.
  
  
  CONCLUSIONS
  Fiducial markers are stable throughout the course of APBI. Planning target volume margins when using bony landmarks should be 10 mm and can be reduced to 6 mm if using fiducials.
authors.affiliation: Department of Radiation Oncology, H. Lee Moffitt Cancer Center & Research Institute, Tampa, FL 33612, USA.
authors.forename: Catherine K
authors.initials: CK
authors.lastname: Park
authors.forename: Jakub
authors.initials: J
authors.lastname: Pritz
authors.forename: Geoffrey G
authors.initials: GG
authors.lastname: Zhang
authors.forename: Kenneth M
authors.initials: KM
authors.lastname: Forster
authors.forename: Eleanor E R
authors.initials: EE
authors.lastname: Harris
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D059925:Anatomic Landmarks / Q000000981:diagnostic imaging; D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D005240:Feasibility Studies; D005260:Female; D057918:Fiducial Markers; D056973:Four-Dimensional Computed Tomography / Q000379:methods; D006046:Gold; D006801:Humans; D015412:Mastectomy, Segmental; D008875:Middle Aged; D009068:Movement; D009367:Neoplasm Staging; D011446:Prospective Studies; D020266:Radiotherapy, Conformal / Q000379:methods*; D061089:Radiotherapy, Image-Guided; D012119:Respiration; D049291:Seroma / Q000000981:diagnostic imaging
chemical_list: D006046:Gold