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. 2023 Sep 19;9(10):e20229.
doi: 10.1016/j.heliyon.2023.e20229. eCollection 2023 Oct.

M-TAG: A modular teaching-aid for Geant4

Liam Carroll  1   2 , Shirin A Enger  1   2
Affiliations

M-TAG: A modular teaching-aid for Geant4

Liam Carroll et al. Heliyon. .

Abstract

Geant4 is a versatile Monte Carlo radiation transport simulation toolkit with a steep learning curve. This work introduces a user-code called M-TAG (Modular Radiation Teaching-Aid for Geant4), built on top of Geant4. M-TAG is designed to help gradually introduce the Geant4 toolkit to new users. The goal of Geant4 is to record quantities from the simulated radiation as it is transported through geometries. M-TAG simplifies the inclusion of new geometric elements and detector components in the simulation by including new classes. M-TAG also provides basic validated examples for some common detector development tasks. Geant4 intercom modules, called messenger classes, manage these classes. To validate M-TAG, simulations were performed to calculate the range of positrons in water. One hundred million decays at the center of a water-filled sphere with a radius of 1 m were allowed for fluorine-18, carbon-11, oxygen-15 and gallium-68. These results were compared to literature values. An inexperienced Geant4 user was tasked with creating a simulation model for a plastic scintillator-based detector and conducting basic tests to assess the effectiveness of M-TAG as a teaching tool. The simulation involved calculating the dose to the detector's sensitive volume using a 2x2 cm planar monoenergetic photon source spanning energies from 20 to 100 keV. One billion particles were simulated twice: once with the actual detector geometry and once with the sensitive volume replaced by water. The validity of M-TAG was also verified by computing dose ratios and comparing them with mass-attenuation ratios obtained from NIST XCOM data sets. The mean positron travel distances were within the distribution of literature values. Simulated positron energy spectra means were within 1.8% of literature means. Simulated dose ratios agreed with literature values within uncertainties. We have developed and verified a modular Geant4 teaching aid called M-TAG. It was used to introduce a new user to Geant4, who used it to perform further validation simulations.

Keywords: Geant4 simulation toolkit; Monte Carlo simmulation; Teaching aid.

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Conflict of interest statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Figure 1
Figure 1
Geometry of toy Geant4 example showing the electron source, tungsten block, photons and sensitive detector.
Figure 2
Figure 2
Classes and functions required to add a basic detector element to a Geant4 simulation.
Figure 3
Figure 3
User inputs and flow of information through M-TAG classes. * Show mandatory user input. (1) Before project compilation, a Python script registers phantom geometry and RunSD header files in the project directory, and (2) formats the factory classes used to build them. (3) At run time, user macro files select which detector RunSD and phantom geometries will be used. This information is passed to messenger classes, which (4) pass the information to the detector construction class. (5) The detector construction uses the phantom header and detector header factory classes to build the required phantoms/detectors. (6) The factories access the phantom geometry and RunSD classes to build the components, and (7) pass the object back to the detector construction.
Figure 4
Figure 4
Basic macro file showing how a user would use a phantomGemoetry and RunSD M-TAG module.
Figure 5
Figure 5
Simple example showing the usage of the CreatePhantom class.
Figure 6
Figure 6
Simulation geometries created using M-TAG. (A) Scintillating fiber in a plastic bolus. (B) Bare scintillating fiber-based detector. (C) 16-channel scintillating fiber-based detector. (D) Spiral scintillating fiber-based detector.
Figure 7
Figure 7
Cross-section of the simulated hyperscint detector showing sensitive volume in white, optical fiber in magenta, acrylic cover in yellow and polyethylene sheath cover in blue. All dimensions are in mm.
Figure 8
Figure 8
Results from the validation simulations. (a) Comparison of simulated positron emission energy spectra (solid lines) to those calculated by Champion and Le Loirec (dotted lines). (b) Comparison of simulated positron ranges in this study with 1 and 0.1 keV energy cutoff analytical equation for range , PeneloPET simulation , GATE simulation , and simulation taking into account positronium formation .
Figure 9
Figure 9
Results from the hyperscint simulation. The simulated dose ratios (PVT/water) are shown as data points, and the mass-energy absorption coefficients are shown as a smooth line. We expected the results for this simulation to agree with the mass-energy absorption coefficient ratios.
See this image and copyright information in PMC

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