radiotherapy treatment planning with monte carlo on a distributed system stéphane chauvie, ircc...
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Radiotherapy treatment planning
with Monte Carlo on a distributed system
Stéphane Chauvie,
IRCC & Mauriziano Hospital & INFN & S Croce e Carle Hospital
Turin, Italy
Genova, 8 Marzo 2004
Radiotherapy Treatment Planning
Analitical algorithms for dose calculation
Monte Carlo methods
Cluster set-up
Monte Carlo parallelization
Data analisys and experimental measurements comparison: open field and IM field
Head and neck tumor with IMRT
Contents
Grant 2002-03/645
Radiotherapy Oncology
CTV
PTV
Spinal cord
S.c. PRV
Pharotid
spare the surrounding
healthy tissues.
deliver high dose to the
target volume
allow local control of
tumor
avoid side-effects
3D-CRT vs IMRT
IM field
Critical points:
- high dose gradients
- strongly unhomogeneous areas
3DCRT & IMRT used in complex anatomical
regions
How much is accurate the dose
calculation ?
Dose calculation algorithms
Expensive
Quick but inaccurate
Accurate but very slow
Cheap (free)
• Pencil beam
• Convolution/Superposition• Monte Carlo
Dose determination accuracy
Total Total with dose calculation
4,1% 4,2%(1%) to 6,5% (5%)
Ahnesjo 1999
Meas in ref pomint, neam
stability &flatness, CT data, setup
=+
Cluster Beowulf parallelisation
Beowulf
Th: High performance networks of PCs are now realistic alternative since offer parallel processing of MC at a lower cost showing competitive performances.
PC & Ethernet
Cluster set-up
Monte Carlo
simulation
Hardware installation
RUN
Monte Carlo parallelisation
Benchmarking
Software configuratio
n
Installation, configuration & benchmarking
to H-LAN
SWITCH
Master
Node03
Node04
Node08
Node07
Node06
Node05
Node02
Parallelization:LAM-MPI
Security:SSH
BiosOSDisk confPartitionRAIDMemoryCPUCompilatorsLinking models
Installation, configuration & benchmarking
to H-LAN
SWITCH
Master
Node03
Node04
Node08
Node07
Node06
Node05
Node02
Efficiency = Sup/ Nprocessors = 0.997
Sup = Tser/Tpar = 3.99
Simulation: geometry
Varian 600C/D Millenium120-leaf MLC
e-
V = 6 MV
NO TUNING, NO CUT
ParticleParticle
ProcessesProcessesMultiple scattering BremsstrahlungIonisationAnnihilationPhotoelectric effect Compton scattering Rayleigh effect conversione+e- pair production
e-e+
Geant4 has only production thresholds, no tracking cuts all particles are tracked down to zero range energy, TOF ... cuts can be defined by the user
simulation: physics
Patient model
DIC
OM
interface
Bone:- CT-el linearity
- cortical bone - bone marrow diluition
Lung:
- CT- linearity
Soft tissue:- CT-tissue relationship
ICRU
IM simple field in
homogeneous phantom
Phase Space Data
IMRT treatment
Anthropomorphic phantom
measurements
Water measurements
Simulation inside patient
IM patient field in
homogeneous phantom
Monte Carlo ParallelizationTake care of PRNG
Phase Space Data
(x,y,z) (px,py,pz)
PSD
E
Water measurementsPDD and dose profile in water
10X10 20X20
P
DD
%
Scanner IC15 ionization chamber
SSD=SAD
Anthropomorphic phantom measurements Measure Monte Diff Broad Diff Pencil Diff Super/ Diff
Carlo % beam % beam % conv % 100,02,4 100,02,2 0,0 103,1 3,1 102,9 2,9 101,9 1,9
178,43,0 175,42,3 -1,7 166,0 -6,9 173,2 -2,9 176,3 -1,2
120,12,7 118,02,2 -1,7 122,3 1,8 124,7 3,8 121,8 1,4 98,83,4 97,02,3 -1,8 100,0 1,2 107,0 8,3 98,3 -0,5
Microchamber A14SL SSD=SAD
Patient simulation
X=10 Y=10
SSD=SAD
Gantry 0°
TAC
IMRT treatment simulation
10X10
isocentric technique
7 field!
Every field
segments no.
165,415,3
events no.
(15,50,5)107
hits no.
(4,02 0,39) 105
time (hours)
0,510,03
IMRT plan evaluation in 3,5 hours with 280000 hits and 3
nodes
E=0.9925
Current ”Geant4” activities in Cuneo...
10 MeV Cyclotron
CT-PET