Tetrahedral Mesh Geometry Capabilities for OpenTOPAS

Largely based on the Geant4 example using the ICRP 145 phantoms

Authors:

• Isaac Meyer
• Alejandro Bertolet
• Dohyeon Yoo

Loading mesh geometries

Currently only the .ele/.node/.material format of tetrahedral meshes is supported where the file formats of ICRP 145 are followed.

MRCP Phantoms

Phantoms need to be defined as geometry components in the parameter file (Type="TsTetGeom"), and the directory where the files .node, .ele and .material provided by IRCP are located needs to be specified (see example "15F_SOBP_Liver.txt"). The mesh phantom geometries can be downloaded from the ICRP website.

Omed Phantom

Included in the examples folder is a coarse mesh geometry phantom named Omed (demo backwards). Visualization of the ICRP phantoms is extremely slow in the TOPAS GUI, and not recommended for checking geometry setups. Omed is oriented in the same direction as the ICRP 145 phantoms with a floating "R" for a right arm and "L" for left arm.

Other Tetrahedral Meshes

Can be defined using the specification of file paths for each file e.g.

s:Ge/TetGeom/PhantomDirectory = "/mesh/file/directory/"
s:Ge/TetGeom/NodeFile         = "my_mesh.node"
s:Ge/TetGeom/MaterialFile     = "my_mesh.material"
s:Ge/TetGeom/EleFile          = "my_mesh.ele"

Scoring

A specific class of scorer is needed for MRCP phantoms by specifying (Quantity="TsTetGeom"). By default, dose to water is computed, but other material can be used to calculate the dose by using the parameter Material. For each organ involved it is necessary to add a new scorer, specifying the list parameter Organ=1 "Name", where Name should be one (or more) of the materials listed in the .material file of the MRCP phantom, e.g., "Liver" or "Stomach_contents". This will restrict the dose considered only to the organ(s) of interest.

Version

Tested for OpenTOPAS v4.0.0 and Geant4 v11.1.2