Medical Applications of Monte Carlo Methods with SuperComputing

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Portland, 21 October 2003
Radiotherapy treatment planning with Monte Carlo
on a distributed system
Stéphane Chauvie, Giuseppe Scielzo
IRCC - Ordine Mauriziano INFN Turin, Italy
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Contents

• 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

Grant 2002-03/645
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Radiotherapy Oncology
spare the surrounding healthy tissues.
deliver high dose to the target volume
allow local control of tumor
avoid side-effects
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3D-CRT vs IMRT
Critical points - high dose gradients - strongly
unhomogeneous areas
3DCRT IMRT used in complex anatomical regions
How much is accurate the dose calculation ?
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Dose calculation algorithms

• Pencil beam
• Convolution/Superposition

• Monte Carlo

Meas in ref pomint, neam stability flatness, CT
data, setup
Accurate but very slow Cheap (free)
Expensive Quick but inaccurate
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Cluster Beowulf parallelisation


PC Ethernet
Th High performance networks of PCs are now
realistic alternative since offer parallel
processing of MC at a lower cost showing
competitive performances.
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Cluster set-up
Hardware installation
Monte Carlo simulation
Software configuration
Benchmarking
Monte Carlo parallelisation
RUN
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Installation, configuration benchmarking
Bios OS Disk conf Partition RAID Memory CPU Compil
ators Linking models
Parallelization LAM-MPI
Security SSH
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Installation, configuration benchmarking
Efficiency Sup/ Nprocessors 0.997
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Simulation geometry
?V 6 MV
e-
Varian 600C/D Millenium 120-leaf MLC
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simulation physics

• 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

NO TUNING, NO CUT
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Patient model
DICOM interface
Soft tissue - CT-tissue relationship ICRU
Bone - CT-?el linearity - cortical bone - bone
marrow diluition
Lung - CT-? linearity
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Monte Carlo Parallelization
Take care of PRNG
IM simple field in homogeneous phantom
Phase Space Data
Water measurements
IM patient field in homogeneous phantom
Anthropomorphic phantom measurements
Simulation inside patient
IMRT treatment
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Phase Space Data
PSD
(x,y,z) (px,py,pz)
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Phase Space
Below jaws 50,4 cm from source
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Water measurements
PDD and dose profile in water
Scanner IC15 ionization chamber SSDSAD
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Anthropomorphic phantom measurements
Microchamber A14SL SSDSAD
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Patient simulation
TAC
X10 Y10 SSDSAD Gantry 0
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IMRT simple field in homogeneous phantom

• Films
• - Simulation

12 segments
Film X-OMAT V SSD90 cm
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IMRT treatment simulation
10X10 isocentric technique 7 field!
Every field segments no. 165,4?15,3 events
no. (15,5?0,5)107 hits no. (4,02 ? 0,39) 105
time (hours) 0,51?0,03
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CONCLUSIONs
E0.9925
MC - evaluate dose distributions at boundaries
and highly unhomogeneous areas - verify
traditional algorithms Cluster scalable, cheap
and easy to use
IMRT plan evaluation in 3,5 hours with 280000
hits and 3 nodes