title: Development of a randomized 3D cell model for Monte Carlo microdosimetry simulations.
abstract: OBJECTIVE
  The objective of the current work was to develop an algorithm for growing a macroscopic tumor volume from individual randomized quasi-realistic cells. The major physical and chemical components of the cell need to be modeled. It is intended to import the tumor volume into GEANT4 (and potentially other Monte Carlo packages) to simulate ionization events within the cell regions.
  
  
  METHODS
  A MATLAB© code was developed to produce a tumor coordinate system consisting of individual ellipsoidal cells randomized in their spatial coordinates, sizes, and rotations. An eigenvalue method using a mathematical equation to represent individual cells was used to detect overlapping cells. GEANT4 code was then developed to import the coordinate system into GEANT4 and populate it with individual cells of varying sizes and composed of the membrane, cytoplasm, reticulum, nucleus, and nucleolus. Each region is composed of chemically realistic materials.
  
  
  RESULTS
  The in-house developed MATLAB© code was able to grow semi-realistic cell distributions (~2 × 10(8) cells in 1 cm(3)) in under 36 h. The cell distribution can be used in any number of Monte Carlo particle tracking toolkits including GEANT4, which has been demonstrated in this work.
  
  
  CONCLUSIONS
  Using the cell distribution and GEANT4, the authors were able to simulate ionization events in the individual cell components resulting from 80 keV gamma radiation (the code is applicable to other particles and a wide range of energies). This virtual microdosimetry tool will allow for a more complete picture of cell damage to be developed.
authors: School of Chemistry and Physics, University of Adelaide, North Terrace, Adelaide 5005, South Australia, Australia. Michael.Douglass@adelaide.edu.au
authors: Michael
authors: M
authors: Douglass
authors: Eva
authors: E
authors: Bezak
authors: Scott
authors: S
authors: Penfold
mesh_terms: D000465:Algorithms; D002477:Cells / Q000473:pathology / Q000528:radiation effects*; D009010:Monte Carlo Method; D011874:Radiometry / Q000379:methods*; D013997:Time Factors; D047368:Tumor Burden