title: Image guidance using 3D-ultrasound (3D-US) for daily positioning of lumpectomy cavity for boost irradiation.
abstract: OBJECTIVE
  The goal of this study was to evaluate the use of 3D ultrasound (3DUS) breast IGRT for electron and photon lumpectomy site boost treatments.
  
  
  METHODS
  20 patients with a prescribed photon or electron boost were enrolled in this study. 3DUS images were acquired both at time of simulation, to form a coregistered CT/3DUS dataset, and at the time of daily treatment delivery. Intrafractional motion between treatment and simulation 3DUS datasets were calculated to determine IGRT shifts. Photon shifts were evaluated isocentrically, while electron shifts were evaluated in the beam's-eye-view. Volume differences between simulation and first boost fraction were calculated. Further, to control for the effect of change in seroma/cavity volume due to time lapse between the 2 sets of images, interfraction IGRT shifts using the first boost fraction as reference for all subsequent treatment fractions were also calculated.
  
  
  RESULTS
  For photon boosts, IGRT shifts were 1.1 ± 0.5 cm and 50% of fractions required a shift >1.0 cm. Volume change between simulation and boost was 49 ± 31%. Shifts when using the first boost fraction as reference were 0.8 ± 0.4 cm and 24% required a shift >1.0 cm. For electron boosts, shifts were 1.0 ± 0.5 cm and 52% fell outside the dosimetric penumbra. Interfraction analysis relative to the first fraction noted the shifts to be 0.8 ± 0.4 cm and 36% fell outside the penumbra.
  
  
  CONCLUSIONS
  The lumpectomy cavity can shift significantly during fractionated radiation therapy. 3DUS can be used to image the cavity and correct for interfractional motion. Further studies to better define the protocol for clinical application of IGRT in breast cancer is needed.
authors.affiliation: Department of Radiation Oncology, Beth Israel Medical Center, New York, NY, USA. mchadha@chpnet.org
authors.forename: Manjeet
authors.initials: M
authors.lastname: Chadha
authors.forename: Amy
authors.initials: A
authors.lastname: Young
authors.forename: Charles
authors.initials: C
authors.lastname: Geraghty
authors.forename: Robert
authors.initials: R
authors.lastname: Masino
authors.forename: Louis
authors.initials: L
authors.lastname: Harrison
mesh_terms: D001940:Breast / Q000473:pathology; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000601:surgery*; D003198:Computer Simulation; D054893:Cone-Beam Computed Tomography / Q000379:methods; D004583:Electrons; D004867:Equipment Design; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D019018:Imagery, Psychotherapy; D021621:Imaging, Three-Dimensional / Q000379:methods*; D015412:Mastectomy, Segmental / Q000379:methods*; D056888:Patient Positioning; D017785:Photons; D014463:Ultrasonography / Q000379:methods*