Transcript Voxel Phantom Setup in MCNPX

Outline
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Intro: voxel phantom + MCNPX
Building geometry
Source sampling (ext, int)
Scoring (average, distribution)
Examples: Klara, Godwin
Summary
Voxel Phantom
Anatomical Realism
before
now
Millions of
boxes assigned
to different
organs and
media
MCNPX
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Monte Carlo general purpose code
MCNP-4C3 + LAHET + Fluka89 + CEM2k + ...
34 particles
Mix-and-match (tables vs models)
Fast lattice initialization new
Fast scoring in lattice
new
And more…
Voxel Phantom Specification
• Voxel dimensions
X-Y-Z
• 3D array of organ IDs
~ 10 MB in binary
• Organ ID => Material
• Material definitions
elements, density
MCNPX Repetitive Geometry
Traditional cells/tallies: 10e6?
Repeated Structures
voxe
l
3D lattice
STEP 1: Constructing 3D Lattice
• Define voxel surfaces
1 rpp 0 0.2 0 0.2 0
0.8
x
y
Block 2
z
• Define lattice
999 0 -1 lat=1 u=999 &
fill=0:254 0:131
0:219 &
Indices: x
y z
Block 1
Followed
by array of
universes
(organ
IDs)
STEP 2: Defining Basic Universes
• Universe = Organ
• Define a list of universes
1 10 -0.95 7 u= 1 $ universe #1Block 1
5 6 -1.05 7 u= 5 $
universe #5
Mapping:
mat + rho =>
universe
Plan
e
7 pz 1000e2
Block 2
STEP 3
Filling Phantom Box with Lattice
• Define surfaces of phantom box
2 rpp 0 51 0 26.4 0 176
x
y
Block 2
z
• Fill the phantom box cell with
lattice
100 0 -2 fill=999
Block 1
Miscellaneous
• Geometry plot!
• Compressor of voxel data
bin 12 MB => ASCII 3 MB
• READ card + NOECHO option
read phantom.geom noecho
read phantom.mat noecho
• Suppress huge tables in production runs
print -128 -140
saves
RAM
Source Sampling
• External Source
sdef par=p erg=3 sur=2.1 x=51 y=d2 z=d3 vec=-1 0 0
dir=1
si2 0 26.7 $ samples Y from 0 to 26.7 cm
sp2 0 1 $ samples Y uniformly
si3 0 176 $ samples Z from 0 to 176 cm
sp3 0 1 $ uniformly
• Internal Source
(efficiency!)
sdef par=p erg=0.1 cel=d5 x=d1 y=d2 z=d3 eff=1e-4
si5 L (11<999<100) $ all voxels of uni 11 in lat 999 in
cell 100 sp5 1
$ uniform sampling
# si1 sp1 si2 sp2 si3 sp3 $ three distr-s for coords sampling
0
0
0 0
0 0 $ coord-s start at low
voxel border
MCNPX Scoring in Lattice
• Recent versions speedup for scoring in
lattice
by orders of magnitude
in full
mesh!
• Unified syntax (source sampling and
scoring)
*f18:p,e (1<999<100) $ id=1 Adipose
tissue, head
• Newest version 2.5.0: F8 tallies in all voxels
*f8:p,e (999<999[0:254 0:131 0:219]<100)
talnp
$ tally no print
Adjusted Voxel Phantoms:
Klara, Godwin
• Based on CT data: woman and man
• Adjusted to ICRP 89 Reference Man (V, m, h)
Godwin
(2.085 × 2.085 × 8)
mm
255 × 132 × 220
7.4e6
voxels
2e6 nonvoid
85 organs
GOdwin
LLAT
mcplib02
Fixed XS
1 source photon
No transport: NOTRN
Time = 14 min
1-MeV Neutron Beam
TECplot
MCNPX plot
Summary
• Geometry objects used
• Fast initialization: < 1 min
• Acceptable speed: 1-2 h per 10e6 src
photons
• RAM used: 500 MB
(scoring,
tables!)
• Good agreement with EGSnrc
• Get fresh version of MCNPX