title: A Monte Carlo based source model for dose calculation of endovaginal TARGIT brachytherapy with INTRABEAM and a cylindrical applicator.
abstract: OBJECTIVE
  To generate and validate a source model of a miniature X-ray generator (INTRABEAM, Carl Zeiss Surgical, Oberkochen, Germany) for endovaginal TARGeted Intra-operative radioTherapy (TARGIT) brachytherapy a Geant4-based Monte Carlo (MC) tool was developed. The model was used to calculate the accurate relative dose distribution for the source combined with a cylindrical applicator which was developed for endovaginal treatment.
  
  
  METHODS
  Geometries with given materials of the X-ray source and applicator were implemented in a Geant4-based dose calculation framework. To reduce the calculation time, phase space files for a set of circular electron beam foci and different beam radii were precalculated. Different beam radii had to be considered because the exact electron beam path on the target is not known in advance. To estimate the electron beam radius distribution of the system, a least squares minimization between the EBT film measured relative dose distribution and the simulation was performed.
  
  
  RESULTS
  Relative dose distributions were calculated and compared with Gafchromic EBT film measurements to validate the MC method. In a region of interest around the source, the 2%/2mm gamma criterion matched with 98%. Profiles showed excellent agreement between measurement and simulation. The calculation time to simulate an entire treatment was twelve minutes.
  
  
  CONCLUSIONS
  The method was able to predict the radius and width of the trajectory where the electrons impact on the target. This enables the complete simulation. The developed method allows calculating relative dose distributions for endovaginal TARGIT brachytherapy matching measured relative dose distributions within clinically acceptable limits.
authors: Department of Radiation Oncology, Universitätsmedizin Mannheim, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany. sven.clausen@umm.de
authors: Sven
authors: S
authors: Clausen
authors: Frank
authors: F
authors: Schneider
authors: Lennart
authors: L
authors: Jahnke
authors: Jens
authors: J
authors: Fleckenstein
authors: Jürgen
authors: J
authors: Hesser
authors: Gerhard
authors: G
authors: Glatting
authors: Frederik
authors: F
authors: Wenz
mesh_terms: D001918:Brachytherapy / Q000295:instrumentation*; D003198:Computer Simulation; D005260:Female; D006801:Humans; D008954:Models, Biological; D015233:Models, Statistical; D009010:Monte Carlo Method; D019736:Prostheses and Implants; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012542:Scattering, Radiation; D012984:Software; D014621:Vagina