title: Improving dose homogeneity in large breasts by IMRT: efficacy and dosimetric accuracy of different techniques.
abstract: OBJECTIVE
  Evaluation of a simplified intensity-modulated irradiation (IMRT), a three-field (MFT), and a conventional two-tangential-field technique regarding dose homogeneity, target coverage, feasibility and, for the first time, dosimetric reliability in patients with large breasts treated postoperatively for breast cancer on a low-energy linac.
  
  
  METHODS
  CT datasets of ten patients with relatively large breast volumes treated for breast cancer were selected. For each patient, four treatment plans were created: low-energy conventional (C-LE), high-energy conventional (C-HE), three-field (MFT), and a two-field aperture-based IMRT technique. Apertures for the IMRT and MFT were created with the aid of a three-dimensional dose display. Dosimetric accuracy of each technique was evaluated in an anthropomorphic thorax/breast phantom.
  
  
  RESULTS
  The mean of planning target volumes receiving < 95% or > 105% of the prescribed total dose was reduced from 16.0% to 13.9% to 10.4% to 8.9% in the C-LE, C-HE, MFT, and IMRT plans, respectively. Phantom dose measurements agreed well with the calculated dose within the breast tissue.
  
  
  CONCLUSIONS
  Aperture-based IMRT using two tangential incident beam directions, as well as a three-field technique with inverse optimization, provide a better alternative to the standard wedged tangential beams for patients with large breasts treated on low-energy linacs while maintaining the efficiency of the treatment-planning and delivery process.
authors.affiliation: Department of Radiation Oncology, Mannheim Medical Center, University of Heidelberg, Mannheim, Germany. abomadyan.yasser@radonk.ma.uni-heidelberg.de
authors.forename: Yasser
authors.initials: Y
authors.lastname: Abo-Madyan
authors.forename: Martin
authors.initials: M
authors.lastname: Polednik
authors.forename: Angelika
authors.initials: A
authors.lastname: Rahn
authors.forename: Frank
authors.initials: F
authors.lastname: Schneider
authors.forename: Barbara
authors.initials: B
authors.lastname: Dobler
authors.forename: Frederik
authors.initials: F
authors.lastname: Wenz
authors.forename: Frank
authors.initials: F
authors.lastname: Lohr
mesh_terms: D000465:Algorithms; D001940:Breast / Q000503:physiopathology; D001943:Breast Neoplasms / Q000503:physiopathology* / Q000532:radiotherapy*; D003198:Computer Simulation; D005260:Female; D006801:Humans; D008954:Models, Biological; D009929:Organ Size; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000379:methods*; D012062:Relative Biological Effectiveness; D015203:Reproducibility of Results; D012542:Scattering, Radiation; D012680:Sensitivity and Specificity