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Operated by Los Alamos National Security, LLC for the U.S. Department of Energy’s NNSA
U N C L A S S I F I E D
LAUR-12-01659
Slide 1
Mesh Human Phantoms
with MCNP
Casey Anderson ([email protected])
Karen Kelley, Tim Goorley
Los Alamos National Laboratory
Operated by Los Alamos National Security, LLC for the U.S. Department of Energy’s NNSA
U N C L A S S I F I E D Slide 2
Summary
Monte Carlo for Radiation Transport
• MCNP
MCNP with Abaqus/CAE
Computational Phantoms
Examples
• Snyder Head, Zubal Head, VIP-Man, XCAT, UM Lungs
Future Work
Conclusion
Acknowledgments
Operated by Los Alamos National Security, LLC for the U.S. Department of Energy’s NNSA
U N C L A S S I F I E D Slide 3
A stochastic method of
determining a solution
• Random sampling
Radiation - subatomic particle
• Carries energy
• Interacts with matter
Any one event undergone by
a particle is “random”
Collision physics & nuclear
data determine probabilities
Large sample = statistical
result
Sample the source
(Location, Energy, Direction)
Track the particle
Sample the collision
(Location, Interaction Type)
Random
number
Random
number
Monte Carlo for Radiation Transport
Operated by Los Alamos National Security, LLC for the U.S. Department of Energy’s NNSA
U N C L A S S I F I E D Slide 4
Monte Carlo for Radiation Transport: Random Walk
Operated by Los Alamos National Security, LLC for the U.S. Department of Energy’s NNSA
U N C L A S S I F I E D Slide 5
Monte Carlo n-Particle (MCNP)
Developed and maintained by Los Alamos National
Laboratory, with thousands of users worldwide for neutral
and charged particle transport
• 11,000 requests in 10 years
Applications: nuclear reactor fuel cycles, medical radiation
therapy, shielding, homeland security, isotope production
Calculates flux, dose, energy deposition based on nuclear
interactions within the geometry
Uses constructive solid geometry (CSG) to define three-
dimensional space
• User specifies bounding surfaces and cells
• Tedious and time consuming for complex geometries
Operated by Los Alamos National Security, LLC for the U.S. Department of Energy’s NNSA
U N C L A S S I F I E D Slide 6
Why am I here?
Operated by Los Alamos National Security, LLC for the U.S. Department of Energy’s NNSA
U N C L A S S I F I E D Slide 7
We can now use a finite element
mesh from Abaqus/CAE as the
geometry description for particle
transport in MCNP6
Easy creation of geometries, 3D visualization capabilities, multi-
physics analysis with the mesh
Spoiler Alert!
Operated by Los Alamos National Security, LLC for the U.S. Department of Energy’s NNSA
U N C L A S S I F I E D Slide 8
CSG
Universe
CSG
Background
Embedded
Mesh
How its done: Hybrid Geometry
The mesh is embedded
in the CSG background
• All mesh types supported
Transport through the
CSG and mesh universe
• Element-to-element
Energy deposition, flux
calculated in the mesh
Results can be used for
3D visualization and
multi-physics analysis
Operated by Los Alamos National Security, LLC for the U.S. Department of Energy’s NNSA
U N C L A S S I F I E D Slide 9
How it's done: Multi-Physics Analysis
Energy density in the meshMCNP6
Power density at nodesPython script
Abaqus/CAE Power density at integration points
PROGRAM RESULTS
Operated by Los Alamos National Security, LLC for the U.S. Department of Energy’s NNSA
U N C L A S S I F I E D Slide 10
Application to
Health Physics
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U N C L A S S I F I E D Slide 11
Computational Phantoms
Mathematical Phantoms
• Equations for surfaces, volumes
Snyder Head
MIRD-5 Adult Male
Tomographic Phantoms
• Developed from CT/MRI data
XCAT
Zubal Head
VIP-Man
Operated by Los Alamos National Security, LLC for the U.S. Department of Energy’s NNSA
U N C L A S S I F I E D Slide 12
Testing of the Hybrid Capability
No CAD/CAE tomographic solid
models readily available
• Meshing issues with XCAT
phantom, developed in CAD
Generated hexahedra mesh
from the voxelized lattice
geometry
• Snyder Head, Zubal Head, VIP-
Man, XCAT
Created an analytical Snyder
Head in Abaqus/CAE
Fill material
Operated by Los Alamos National Security, LLC for the U.S. Department of Energy’s NNSA
U N C L A S S I F I E D Slide 13
Examples
Operated by Los Alamos National Security, LLC for the U.S. Department of Energy’s NNSA
U N C L A S S I F I E D Slide 14
Snyder Head Phantom
Mathematical model from W.S. Snyder
4 mm and 8 mm voxelized models
converted into an Abaqus/CAE mesh
Created solid model in Abaqus/CAE using
the analytical equations
Allows comparison of voxelized CSG,
voxelized mesh, and unstructured mesh
models for various resolutions
• 10 cm diameter photon beam
• Mesh tallies used as a comparison
Operated by Los Alamos National Security, LLC for the U.S. Department of Energy’s NNSA
U N C L A S S I F I E D Slide 15
Snyder Head Phantom
8 mm 4 mm Unstructured
Voxelized Voxelized Mesh
Operated by Los Alamos National Security, LLC for the U.S. Department of Energy’s NNSA
U N C L A S S I F I E D Slide 16
Snyder Head Phantom: Photon Flux Results
(particles/cm^2)8 mm 4 mm Unstructured
Voxelized Voxelized Mesh
Operated by Los Alamos National Security, LLC for the U.S. Department of Energy’s NNSA
U N C L A S S I F I E D Slide 17
Snyder Head Phantom: Flux Comparison
Operated by Los Alamos National Security, LLC for the U.S. Department of Energy’s NNSA
U N C L A S S I F I E D Slide 18
Snyder Head Phantom: MCNP Computer Run Time
* Run times for 100 million histories
** Unstructured Mesh, .2 cm seed size
Model Parts ElementsVolume (cm3)
% Analytical Volume
Processing(min)
Transport * (min)
8 mm (Mesh)
64 28,553 3,322 +19.9% 0.16 17,804
4 mm (Mesh)
40 159,484 3,037 +9.6% 0.43 64,580
Analytical (Mesh) **
3 18,150 2,751 -0.7% 0.12 14,847
8 mm (CSG)
64 28,553 3,322 +19.9% 0.19 1,213
Analytical(CSG)
2,771 0.0% 0.03 360
Operated by Los Alamos National Security, LLC for the U.S. Department of Energy’s NNSA
U N C L A S S I F I E D Slide 19
Zubal Head Phantom: Photon Flux
(particles/cm^2)
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U N C L A S S I F I E D Slide 20
Visible Photographic Man (VIP-Man)
4 mm resolution model provided by Dr. X George Xu
• In MCNP lattice format
Optimized to reach 30k – 50k elements per part
• Fat, muscle, and bone divided into multiple parts
Volumetric Iodine-131 source placed in the thyroid
• Common treatment used for hypothyroidism
• Source set in the thyroid
• 60 MBq (1.62 mCi) , 55% uptake
• Dose calculation to the testes
• Posterior – Anterior photon source
Operated by Los Alamos National Security, LLC for the U.S. Department of Energy’s NNSA
U N C L A S S I F I E D Slide 21
Voxelized 4 mm VIP-Man: Geometry
Abaqus/CAE
Viewer MCNP Plotter
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U N C L A S S I F I E D Slide 22
Voxelized 4 mm VIP-Man: Split Model
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U N C L A S S I F I E D Slide 23
Voxelized 4 mm VIP-Man: Optimization
PartsMax.
ElementsAvg.
Elements
Pre-Processing
(min)
Transport (min) *
Memory (GB)
61 645,491 26,700 605.6 36,171 2.0
99 72,543 16,450 30.9 19,882 3.1
139 72,543 11,712 17.9 20,345 3.5
142 54,709 11,476 13.8 20,143 4.0
**108 35,199 11,856 7.6 19,536 2.6
Processor -- 2.67 GHz Intel Xeon X7542
* Run times for 100 million histories
** Torso Model (No Legs)
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U N C L A S S I F I E D Slide 24
Voxelized 4 mm VIP-Man: Thyroid Source
Energy Deposition (MeV/gram)
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U N C L A S S I F I E D Slide 25
Voxelized 4 mm VIP-Man: Thyroid Source
Mass (g)Dose
(Mev/g)Dose (J/kg)
mSv
Prostate 19.5 1.98E+06 3.17E-03 3.17 (.09)
Testes 21.4 7.11E+05 1.14E-03 1.14 (.40)
Thyroid 27.5 9.73E+10 1.56E+01 1.56E+04
Society of Nuclear Medicine Procedure
Guideline for Therapy of Thyroid Disease
with Iodine-131 (Sodium Iodide)
• 3 Mbq/gram, 55% uptake
• Dose to testes (20 g thyroid)
— 0.026 mGy/MBq = 1.56 mSv
MCNP Results
Operated by Los Alamos National Security, LLC for the U.S. Department of Energy’s NNSA
U N C L A S S I F I E D Slide 26
Voxelized 4 mm VIP-Man: PA Source
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U N C L A S S I F I E D Slide 27
Voxelized 4 mm VIP-Man: PA Source
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U N C L A S S I F I E D Slide 28
Voxelized XCAT Phantom: 6.25 mm resolution
Operated by Los Alamos National Security, LLC for the U.S. Department of Energy’s NNSA
U N C L A S S I F I E D Slide 29
Unstructured Mesh Lungs Model
Operated by Los Alamos National Security, LLC for the U.S. Department of Energy’s NNSA
U N C L A S S I F I E D Slide 30
Future Work
Testing full body unstructured mesh human phantoms
• Currently only UM sections and voxelized mesh models
Dose conversion factors
• Dose calculations with neutrons
Include other particles
• Limited to neutrons and photons
Operated by Los Alamos National Security, LLC for the U.S. Department of Energy’s NNSA
U N C L A S S I F I E D Slide 31
Conclusion
The unstructured mesh capability in MCNP6 allows generation of
complex geometries, improved 3D visualization capabilities, and
multi-physics analysis
Detailed computational phantoms with unstructured mesh can be
generated and used for dose assessment
• Anatomically detailed, patient specific
Dose calculation results compared well for simple iodine thyroid
source
Abaqus/CAE is a useful tool for generating complex geometries,
meshing for particle transport, multi-physics analysis, and
visualization
Operated by Los Alamos National Security, LLC for the U.S. Department of Energy’s NNSA
U N C L A S S I F I E D Slide 32
Acknowledgments
Karen Kelley
Tim Goorley
Steve McCready
Chelsea D'Angelo
David Crane
Roger Martz
George Xu (Rensselear Polytechnic Institute)
Paul Segars (John Hopkins / Duke University)
George Zubal (Yale University)
Operated by Los Alamos National Security, LLC for the U.S. Department of Energy’s NNSA
U N C L A S S I F I E D
LAUR-12-01659
Slide 33
Mesh Human Phantoms
with MCNP
Casey Anderson ([email protected])
Karen Kelley, Tim Goorley
Los Alamos National Laboratory