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

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