Post on 03-Oct-2021
New Mexico Workshop, May 15, 2011
Pablo P. Yepes, Rice U. 1
Fast and Accurate Calculations for Proton Therapy
Pablo Yepes 1,2, John Eley2, Jessie Huang 1,2, Dragan Mirkovic 2, Wayne Newhauser 2, Sharmalee Randeniya 2, Uwe Titt 2, Phil Taddei 2
1) T.W. Bonner Lab, Rice University2) University of Texas, MD Anderson Cancer Center
New Mexico Workshop, May 15, 2011
Pablo P. Yepes, Rice U. 2
Outline
FDC (track repeating algorithm) for dose calculations
Justification: MC vs Analytical Applications
GPU Implementation Applications, examples.
Why the Monte Carlo Approach
Pros: higher accuracy Information about off-field and
background (for example neutrons) radiation
Cons Very high computational demands
New Mexico Workshop, May 15, 2011
Pablo P. Yepes, Rice U. 4
Proton TherapyMonte Carlo versus Analytical
MC computational times are very high: >500 cpu hours for 1 beam treatment plan
Dose in Lung
AnalyticalMC (MCNPX)
New Mexico Workshop, May 15, 2011
Pablo P. Yepes, Rice U. 5
Proton TherapyMC versus Analytical (Con't)
Along beame
New Mexico Workshop, May 15, 2011
Pablo P. Yepes, Rice U. 6
Fast Dose Calculator (FDC)
A track repeating algorithm for proton dose calculations
Uses pre-calculated tracks in water to estimate dose in a variety of other materials by scaling path lengths and scattering angles.
Uses GEANT4 as engine to generate pre-calculated tracks. Same technique could be applied for the MC of your choice (MCNPX, FLUKA, etc).
• J. S. Li, B. Shahine, E. Fourkal and C.M. Ma, “A particle track-repeating algorithm for proton beam dose calculation”, Phys. Med. Biol., 50, 1001–10 (2005).
•P. Yepes, S. Randeniya, P. Taddei, W. Newhauser, A Track Repeating Algorithm for Fast Monte Carlo Dose Calculations of Proton Radiotherapy, Nuclear Technology 168, 334 (2009).
• P.Yepes P, S. Randeniya, P. J. Taddei and W. D. Newhauser, “Monte Carlo fast dose calculator for proton radiotherapy: application to a voxelized geometry representing a patient with prostate cancer”, Phys. Med. Biol., 54, N21-N28 (2009).
• Yepes, T. Brannan, J. Huang, D. Mirkovic, W.D. Newhauser, P.J. Taddei, U. Titt, “Application of a fast proton dosecalculation algorithm to a thorax geometry”, Rad. Meas. 45, 1367 (2010).
• P. Yepes, D. Mirkovic, P.J. Taddei, “A GPU implementation of a track-repeating algorithm for proton radiotherapy dose calculations”, Phys. Med. Biol. 55, 7107 (2010).
New Mexico Workshop, May 15, 2011
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Generate Pre-calculated tracks GEANT breaks trajectories in steps. For each step stores deposited energy, energy change, step length and direction. Simulate 250 MeV protons on a 660x660x750 mm3 water phantom. “Pick-up” the trajectory at whatever energy is needed. Average of 460 steps and 3.5Kbytes per proton Generate 10 million protons in water for database in ~15 min on 100 CPUs
New Mexico Workshop, May 15, 2011
Pablo P. Yepes, Rice U. 8
“Water history”
Re-trackinga “water history” inheterogeneousmedia
New Mexico Workshop, May 15, 2011
FDC Scaling Parameters
Analytical Approach: Length scaling from Proton Stopping Power
(Bethe-Block Formula) Angle scaling from Multiple Scattering Theory.
Numerical Approach:
Obtain the scaling parameters by minimizing the difference in dose distributions in various homogeneous phantoms for various materials for FDC and GEANT4.
New Mexico Workshop, May 15, 2011
Pablo P. Yepes, Rice U. 10
Proton Simulation Setup
Aperture conforms the beam/field to the transverse shape of the tumor
Range compensator conforms the beam/field to the longitudinal shape of the tumor
Aperture
Range Compensator
Phantom
p
New Mexico Workshop, May 15, 2011
Pablo P. Yepes, Rice U. 11
GEANT4 versus FDCProtons Prostate
Realistic Beam and Shaping Elements (Aperture and Range Compensator
New Mexico Workshop, May 15, 2011
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Proton Prostate SimulationAccuracy/Timing
GEANT: 0.3 s/proton; FDC: 0.6 ms/proton
Accuracy relative to full Monte Carlo (GEANT) better than 2%
FDC Timing is ~ 500 faster than GEANT
New Mexico Workshop, May 15, 2011
Protons Lung• 140 MeV proton circular beam• Lung is a highly inhomogeneous medium, a tough test for FDC
FDCGEANT4
GEANT4-FDC
New Mexico Workshop, May 15, 2011
FDC on GPUs
New Mexico Workshop, May 15, 2011
FDC on GPUs (GFDC) Graphic Cards with multiple (GPU cores)
processors.
NVIDIA developed tools to allow running “regular” code on such cards.
Miniature computer cluster on a card for a fraction of the cost and maintenance.
Code divided on CPU and GPU sections
GPU code is regular (C and quasi C++) with some size and process limitations.
Each GPU core works on the re-tracking of one particular history.
Substantial reorganization of the code
GEFORCE GTX 295, NVIDIA
New Mexico Workshop, May 15, 2011
GFDC Logic Flow
New Mexico Workshop, May 15, 2011
GPU FDC for Protons
Circular Mono-energetic 121 MeV beam with 4 cm radius
Thorax phantom with 6 million voxels GFDC speed up of 75.5 with respect to FDC
CPU version
Protons/s
GEANT4 ~1
FDC 2,444
GFDC 184,525
New Mexico Workshop, May 15, 2011
Energy Deposited in Thorax for ProtonsAlong beam axis
New Mexico Workshop, May 15, 2011
Energy Deposited in Thorax for ProtonsCross Section: Axis Perpendicular to Beam
New Mexico Workshop, May 15, 2011
Lung Cross Section for ProtonsWhat about tails?
New Mexico Workshop, May 15, 2011
Accuracy
New Mexico Workshop, May 15, 2011
Statistical Errors/Timing
Batch
History-by-history
New Mexico Workshop, May 15, 2011
FDC Website(Part of code from dicompyler: Adit Panchal, Roy Keyes)
New Mexico Workshop, May 15, 2011
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Conclusions Track-repeating algorithm for proton and photon
implemented on a GPU architecture. Computational times reduced by four orders of
magnitude compared to full Monte Carlo. GPU results reproduce full Monte Carlo within
2%. A system with multiple GPU cards should allow
real-time Monte-Carlo-accurate dose calculations for radio-therapy.
February 23, 2009 Pablo P. Yepes, Rice U. 25
Keep it simple!Keep it simple!
New Mexico Workshop, May 15, 2011
Pablo P. Yepes, Rice U. 26
Fast Dose Calculator in a Nutshell
Water to Material M scaling
For each step, length (L) and angle with respect to previous step (φ) are scaled.Length: LM= α (E) Lh2o
Scattering Angles: φM= β φh20
M=