Outline 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 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 voxel 3D lattice

STEP 1: Constructing 3D Lattice Define voxel surfaces Define lattice 1 rpp 0 0.2 0 0.2 0 0.8 Block 2 x y z 999 0 -1 lat=1 u=999 & fill=0:254 0:131 0:219 & Block 1 x y z Indices: 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 #1 5 6 -1.05 7 u= 5 $ universe #5 Block 1 Mapping: mat + rho => universe Plane 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 Fill the phantom box cell with lattice 100 0 -2 fill=999 Block 2 x y z 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 coord-s sampling 0 0 0 0 0 0 $ coord-s start at low voxel border 0.2 1 0.2 1 0.8 1

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 prdmp 2j 1 $ get data via MCTAL file

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 non-void 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 MCNP-5