title: Dosimetric and radiobiological comparison of TG-43 and Monte Carlo calculations in192Ir breast brachytherapy applications.
abstract: OBJECTIVE
  To investigate the clinical significance of introducing model based dose calculation algorithms (MBDCAs) as an alternative to TG-43 in192Ir interstitial breast brachytherapy.
  
  
  METHODS
  A 57 patient cohort was used in a retrospective comparison between TG-43 based dosimetry data exported from a treatment planning system and Monte Carlo (MC) dosimetry performed using MCNP v. 6.1 with plan and anatomy information in DICOM-RT format. Comparison was performed for the target, ipsilateral lung, heart, skin, breast and ribs, using dose distributions, dose-volume histograms (DVH) and plan quality indices clinically used for plan evaluation, as well as radiobiological parameters.
  
  
  RESULTS
  TG-43 overestimation of target DVH parameters is statistically significant but small (less than 2% for the target coverage indices and 4% for homogeneity indices, on average). Significant dose differences (>5%) were observed close to the skin and at relatively large distances from the implant leading to a TG-43 dose overestimation for the organs at risk. These differences correspond to low dose regions (<50% of the prescribed dose), being less than 2% of the prescribed dose. Detected dosimetric differences did not induce clinically significant differences in calculated tumor control probabilities (mean absolute difference <0.2%) and normal tissue complication probabilities.
  
  
  CONCLUSIONS
  While TG-43 shows a statistically significant overestimation of most indices used for plan evaluation, differences are small and therefore not clinically significant. Improved MBDCA dosimetry could be important for re-irradiation, technique inter-comparison and/or the assessment of secondary cancer induction risk, where accurate dosimetry in the whole patient anatomy is of the essence.
authors.affiliation: Medical Physics Laboratory, Medical School, National and Kapodistrian University of Athens, Greece.
authors.forename: V
authors.initials: V
authors.lastname: Peppa
authors.affiliation: Medical Physics Laboratory, Medical School, National and Kapodistrian University of Athens, Greece.
authors.forename: E P
authors.initials: EP
authors.lastname: Pappas
authors.affiliation: Medical Physics Laboratory, Medical School, National and Kapodistrian University of Athens, Greece.
authors.forename: P
authors.initials: P
authors.lastname: Karaiskos
authors.affiliation: National Institute of Oncology, Budapest, Hungary.
authors.forename: T
authors.initials: T
authors.lastname: Major
authors.affiliation: National Institute of Oncology, Budapest, Hungary.
authors.forename: C
authors.initials: C
authors.lastname: Polgár
authors.affiliation: Medical Physics Laboratory, Medical School, National and Kapodistrian University of Athens, Greece. Electronic address: ppapagi@med.uoa.gr.
authors.forename: P
authors.initials: P
authors.lastname: Papagiannis
mesh_terms: D000465:Algorithms; D055592:Biophysical Phenomena; D001918:Brachytherapy / Q000379:methods* / Q000706:statistics & numerical data; D001943:Breast Neoplasms / Q000532:radiotherapy*; D003198:Computer Simulation; D005260:Female; D006801:Humans; D007496:Iridium Radioisotopes / Q000627:therapeutic use*; D009010:Monte Carlo Method; D019047:Phantoms, Imaging; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000706:statistics & numerical data*; D012189:Retrospective Studies
chemical_list: D007496:Iridium Radioisotopes
keywords: (192)Ir; Brachytherapy; Breast; Dosimetry; MBDCA; TG-43