title: A generic high-dose rate (192)Ir brachytherapy source for evaluation of model-based dose calculations beyond the TG-43 formalism.
abstract: OBJECTIVE
  In order to facilitate a smooth transition for brachytherapy dose calculations from the American Association of Physicists in Medicine (AAPM) Task Group No. 43 (TG-43) formalism to model-based dose calculation algorithms (MBDCAs), treatment planning systems (TPSs) using a MBDCA require a set of well-defined test case plans characterized by Monte Carlo (MC) methods. This also permits direct dose comparison to TG-43 reference data. Such test case plans should be made available for use in the software commissioning process performed by clinical end users. To this end, a hypothetical, generic high-dose rate (HDR) (192)Ir source and a virtual water phantom were designed, which can be imported into a TPS.
  
  
  METHODS
  A hypothetical, generic HDR (192)Ir source was designed based on commercially available sources as well as a virtual, cubic water phantom that can be imported into any TPS in DICOM format. The dose distribution of the generic (192)Ir source when placed at the center of the cubic phantom, and away from the center under altered scatter conditions, was evaluated using two commercial MBDCAs [Oncentra(®) Brachy with advanced collapsed-cone engine (ACE) and BrachyVision ACUROS™ ]. Dose comparisons were performed using state-of-the-art MC codes for radiation transport, including ALGEBRA, BrachyDose, GEANT4, MCNP5, MCNP6, and PENELOPE2008. The methodologies adhered to recommendations in the AAPM TG-229 report on high-energy brachytherapy source dosimetry. TG-43 dosimetry parameters, an along-away dose-rate table, and primary and scatter separated (PSS) data were obtained. The virtual water phantom of (201)(3) voxels (1 mm sides) was used to evaluate the calculated dose distributions. Two test case plans involving a single position of the generic HDR (192)Ir source in this phantom were prepared: (i) source centered in the phantom and (ii) source displaced 7 cm laterally from the center. Datasets were independently produced by different investigators. MC results were then compared against dose calculated using TG-43 and MBDCA methods.
  
  
  RESULTS
  TG-43 and PSS datasets were generated for the generic source, the PSS data for use with the ace algorithm. The dose-rate constant values obtained from seven MC simulations, performed independently using different codes, were in excellent agreement, yielding an average of 1.1109 ± 0.0004 cGy/(h U) (k = 1, Type A uncertainty). MC calculated dose-rate distributions for the two plans were also found to be in excellent agreement, with differences within type A uncertainties. Differences between commercial MBDCA and MC results were test, position, and calculation parameter dependent. On average, however, these differences were within 1% for ACUROS and 2% for ace at clinically relevant distances.
  
  
  CONCLUSIONS
  A hypothetical, generic HDR (192)Ir source was designed and implemented in two commercially available TPSs employing different MBDCAs. Reference dose distributions for this source were benchmarked and used for the evaluation of MBDCA calculations employing a virtual, cubic water phantom in the form of a CT DICOM image series. The implementation of a generic source of identical design in all TPSs using MBDCAs is an important step toward supporting univocal commissioning procedures and direct comparisons between TPSs.
authors.affiliation: Department of Atomic, Molecular and Nuclear Physics, University of Valencia, Burjassot 46100, Spain.
authors.forename: Facundo
authors.initials: F
authors.lastname: Ballester
authors.affiliation: Department of Medical and Health Sciences (IMH), Radiation Physics, Faculty of Health Sciences, Linköping University, Linköping SE-581 85, Sweden and Department of Medical Physics, Karolinska University Hospital, Stockholm SE-171 76, Sweden.
authors.forename: Åsa
authors.initials: Å
authors.lastname: Carlsson Tedgren
authors.affiliation: Department of Radiation Physics, ERESA, Hospital General Universitario, Valencia E-46014, Spain.
authors.forename: Domingo
authors.initials: D
authors.lastname: Granero
authors.affiliation: Department of Physical Sciences, Peter MacCallum Cancer Centre and Royal Melbourne Institute of Technology, Melbourne, Victoria 3000, Australia.
authors.forename: Annette
authors.initials: A
authors.lastname: Haworth
authors.affiliation: Department of Radiation Oncology, Helen F. Graham Cancer Center, Christiana Care Health System, Newark, Delaware 19713.
authors.forename: Firas
authors.initials: F
authors.lastname: Mourtada
authors.affiliation: Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP, São Paulo 05508-000, Brazil and Department of Radiation Oncology (MAASTRO), GROW, School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht 6201 BN, The Netherlands.
authors.forename: Gabriel Paiva
authors.initials: GP
authors.lastname: Fonseca
authors.affiliation: Medical Physics Laboratory, Medical School, University of Athens, 75 MikrasAsias, Athens 115 27, Greece.
authors.forename: Kyveli
authors.initials: K
authors.lastname: Zourari
authors.affiliation: Medical Physics Laboratory, Medical School, University of Athens, 75 MikrasAsias, Athens 115 27, Greece.
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Papagiannis
authors.affiliation: Department of Radiation Oncology, Tufts University School of Medicine, Boston, Massachusetts 02111.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Rivard
authors.affiliation: Clinic of Radiotherapy, University Hospital of Schleswig-Holstein, Campus Kiel, Kiel 24105, Germany.
authors.forename: Frank-André
authors.initials: FA
authors.lastname: Siebert
authors.affiliation: Department of Medical Physics, Cross Cancer Institute, Edmonton, Alberta T6G 1Z2, Canada and Department of Oncology, University of Alberta, Edmonton, Alberta T6G 2R3, Canada.
authors.forename: Ron S
authors.initials: RS
authors.lastname: Sloboda
authors.affiliation: The William Buckland Radiotherapy Centre, Alfred Hospital, Melbourne, Victoria 3000, Australia.
authors.forename: Ryan L
authors.initials: RL
authors.lastname: Smith
authors.affiliation: Carleton Laboratory for Radiotherapy Physics, Department of Physics, Carleton University, Ottawa, Ontario K1S 5B6, Canada.
authors.forename: Rowan M
authors.initials: RM
authors.lastname: Thomson
authors.affiliation: Department of Radiation Oncology (MAASTRO), GROW, School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht 6201 BN, The Netherlands and Department of Medical Physics, McGill University Health Centre, Montréal, Québec H3G 1A4, Canada.
authors.forename: Frank
authors.initials: F
authors.lastname: Verhaegen
authors.affiliation: Department of Atomic, Molecular and Nuclear Physics, University of Valencia and IFIC (CSIC-UV), Burjassot 46100, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Vijande
authors.affiliation: Département de Radio-Oncologie et Axe oncologie du Centre de Recherche du CHU de Québec, CHU de Québec, Québec, Québec G1R 2J6, Canada and Département de Physique, de Génie Physique et d'Optique et Centre de recherche sur le cancer, Université Laval, Québec, Québec G1R 2J6, Canada.
authors.forename: Yunzhi
authors.initials: Y
authors.lastname: Ma
authors.affiliation: Département de Radio-Oncologie et Axe oncologie du Centre de Recherche du CHU de Québec, CHU de Québec, Québec, Québec G1R 2J6, Canada and Département de Physique, de Génie Physique et d'Optique et Centre de recherche sur le cancer, Université Laval, Québec, Québec G1R 2J6, Canada.
authors.forename: Luc
authors.initials: L
authors.lastname: Beaulieu
mesh_terms: D000465:Algorithms; D001918:Brachytherapy / Q000379:methods*; D006801:Humans; D007496:Iridium Radioisotopes / Q000627:therapeutic use*; D009010:Monte Carlo Method; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D014867:Water
chemical_list: D007496:Iridium Radioisotopes; D014867:Water