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 (casey_a@lanl.gov)

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

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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

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U N C L A S S I F I E D Slide 4

Monte Carlo for Radiation Transport: Random Walk

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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

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U N C L A S S I F I E D Slide 6

Why am I here?

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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!

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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

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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

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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

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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

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U N C L A S S I F I E D Slide 13

Examples

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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

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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

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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

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U N C L A S S I F I E D Slide 17

Snyder Head Phantom: Flux Comparison

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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

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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

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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

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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

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U N C L A S S I F I E D Slide 29

Unstructured Mesh Lungs Model

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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

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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

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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)

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U N C L A S S I F I E D

LAUR-12-01659

Slide 33

Mesh Human Phantoms

with MCNP

Casey Anderson (casey_a@lanl.gov)

Karen Kelley, Tim Goorley

Los Alamos National Laboratory