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Radiotherapy treatment planning with Monte Carlo on a distributed system
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Radiotherapy treatment planning with Monte Carlo on a distributed system

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

  2. 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

  3. PTV Pharotid CTV S.c. PRV Spinal cord Radiotherapy Oncology spare the surrounding healthy tissues. deliver high dose to the target volume allow local control of tumor avoid side-effects

  4. IM field 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 ?

  5. Dose determination accuracy Total Total with dose calculation 4,1% 4,2%(1%) to 6,5% (5%) Ahnesjo 1999 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

  6. Beowulf 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.

  7. Cluster set-up Hardware installation Monte Carlo simulation Software configuration Benchmarking Monte Carlo parallelisation RUN

  8. to H-LAN Node03 Node08 Node04 Node07 Node06 Node05 Node02 Master SW I T C H Installation, configuration & benchmarking Bios OS Disk conf Partition RAID Memory CPU Compilators Linking models Parallelization: LAM-MPI Security: SSH

  9. to H-LAN Node03 Node07 Node05 Node02 Node08 Node06 Node04 Master Sup = Tser/Tpar = 3.99 SW I T C H Installation, configuration & benchmarking Efficiency = Sup/ Nprocessors = 0.997

  10. Simulation: geometry V = 6 MV e- • Varian 600C/D Millenium • 120-leaf MLC

  11. Particle Processes Multiple scattering Bremsstrahlung Ionisation Annihilation Photoelectric effect Compton scattering Rayleigh effect g conversion e+e- pair production e- e+  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

  12. Patient model Soft tissue: - CT-tissue relationship ICRU DICOM interface Bone: - CT-el linearity - cortical bone - bone marrow diluition Lung: - CT- linearity

  13. 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

  14. E Phase Space Data PSD (x,y,z) (px,py,pz)

  15. px,py pz Phase Space Below jaws 50,4 cm from source

  16. 10X10 20X20 PDD % Water measurements PDD and dose profile in water Scanner IC15 ionization chamber SSD=SAD

  17. Measure Monte Diff Broad Diff Pencil Diff Super/ Diff Carlo % beam % beam % conv % 100,02,4 100,02,2 0,0 103,1 3,1 102,9 2,9 101,9 1,9 178,43,0 175,42,3 -1,7 166,0 -6,9 173,2 -2,9 176,3 -1,2 120,12,7 118,02,2 -1,7 122,3 1,8 124,7 3,8 121,8 1,4 98,83,4 97,02,3 -1,8 100,0 1,2 107,0 8,3 98,3 -0,5 Anthropomorphic phantom measurements Microchamber A14SL SSD=SAD

  18. Patient simulation TAC X=10 Y=10 SSD=SAD Gantry 0°

  19. Skip & shoot IMRT simple field in homogeneous phantom • Films • - Simulation 12 segments Film X-OMAT V SSD=90 cm

  20. 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

  21. CONCLUSIONs E=0.9925 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