title: A dosimetric comparison of IORT techniques in limited-stage breast cancer.
abstract: OBJECTIVE
  For intraoperative radiotherapy (IORT) during breast-conserving treatment four different techniques have been addressed: interstitial brachytherapy, an inflatable balloon with a central high-dose-rate source (MammoSite), a miniature orthovolt system (Intrabeam), and linac-based electron radiotherapy (IOERT). The dosimetric properties of these methods are compared.
  
  
  METHODS
  Planning target volumes (PTVs) of the same size but of different shapes are assumed, corresponding to the technique's specific situs. Dose distributions for the PTVs and for surrounding tissues are demonstrated by dose-volume histograms and a list of physical parameters. A dose inhomogeneity index (DII) is introduced to describe the deviation of a delivered from the prescribed dose, reaching its minimal value 0 in case of perfect homogeneity.
  
  
  RESULTS
  In terms of DII, IOERT reaches the lowest value followed by the MammoSite, the Intrabeam and interstitial implants. The surrounding tissues receive the smallest average dose with IOERT, closely followed by the orthovolt system.
  
  
  CONCLUSIONS
  When comparing simplified geometric figures, IOERT delivers the most homogeneous dose distributions. However, in clinical reality PTVs often present asymmetric shapes instead of ideal geometries. Due to a strictly centric dose fall-off, any system with a round central applicator will have technical limits. During IOERT margin-directed applicator guidance is possible and interstitial brachytherapy allows for polygonal dose shaping. These techniques seem to be superior for asymmetric PTV irradiation.
authors.affiliation: Department of Radio-Oncology, Salzburger Landeskliniken and Paracelsus Private Medical University (PMU), Salzburg, Austria.
authors.forename: Olaf
authors.initials: O
authors.lastname: Nairz
authors.forename: Heinz
authors.initials: H
authors.lastname: Deutschmann
authors.forename: Michael
authors.initials: M
authors.lastname: Kopp
authors.forename: Karl
authors.initials: K
authors.lastname: Wurstbauer
authors.forename: Gerhard
authors.initials: G
authors.lastname: Kametriser
authors.forename: Gerd
authors.initials: G
authors.lastname: Fastner
authors.forename: Florian
authors.initials: F
authors.lastname: Merz
authors.forename: Roland
authors.initials: R
authors.lastname: Reitsamer
authors.forename: Christian
authors.initials: C
authors.lastname: Menzel
authors.forename: Felix
authors.initials: F
authors.lastname: Sedlmayer
mesh_terms: D001943:Breast Neoplasms / Q000532:radiotherapy* / Q000601:surgery*; D006801:Humans; D007430:Intraoperative Care / Q000379:methods*; D015412:Mastectomy, Segmental / Q000379:methods*; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016896:Treatment Outcome