Nanodosimetric Cluster Size Distributions from 250MeV Protons

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Nanodosimetric Cluster Size Distributions from
250MeV Protons

• Andrew Wroe1, Reinhard Schulte2, Vladimir
  Bashkirov2, Anatoly Rosenfeld1, Bernd Grosswendt3
• Centre for Medical Radiation Physics, University
  of Wollongong, Australia
• Loma Linda University Medical Center, Loma Linda,
  CA, USA
• Physikalisch-Technische Bundesanstalt,
  Braunschweig, Germany
• E-mail ajw16_at_uow.edu.au

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Project Outline

• Develop greater understanding of techniques used
  in proton therapy
• Improve our understanding of the interactions of
  protons on a DNA level
• Apply this understanding to improve proton therapy

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What is Proton Therapy?
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What is Proton Therapy?
X-Ray Proton
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What is Proton Therapy?
X-Ray Proton
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Loma Linda University Medical Center

• 900 bed hospital situated approximately 60 miles
  outside LA
• 3 Gantry treatment rooms
• 2 fixed beam treatment lines
• 3 research beam lines
• 150 patients treated daily with plans to expand
  this to 200-250

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Loma Linda University Medical Center
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LLUMC Gantry Room
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LLUMC Treatment Room
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Limitations of Proton Therapy

• Proton therapy at present has 2 limitations
• Both are related to treatment planning
• 1. Inaccuracy of CT number conversion
• 2. Varying proton RBE

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What is Nanodosimetry?

• Measures the effect of radiation on a DNA level
• Determines level of cell death and mutation
• 2-5 ionisations - repairable cell damage
• 6-10 ionisations - irreparable cell damage

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What is Nanodosimetry?

• DNA damage can occur via
• Direct Damage Processes
• Indirect Damage Processes
• DNA damage can produce
• DSBs
• SSBs
• Base Lesions

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What is Nanodosimetry?
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Nanodosimetry Applications

• Radiation therapy
• Radiation protection
• Space exploration
• Biological and electronic systems

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Nanodosimetry Program

• Experimental Low pressure gas detector counts
  ionisations in an equivalent DNA volume
• Simulations Reproduce experimental conditions,
  results and can be used to determine the effect
  on more complex structures

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Experimental Nanodosimetry
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Nanodosimetry Simulations

• Simulates experimental conditions outside the
  detector including beam modifying devices
• Simulates interactions within the nanodosimeter

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Nanodosimetry Simulations
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Nanodosimetry Simulations
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Nanodosimetry Simulations
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Nanodosimetry Results
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Nanodosimetry Results

• Excellent agreement for small clusters
• Disagreement for cluster size gt 9
• High LET particles and secondary electrons
  produced by beam modifying devices effect
  accuracy of simulations for large clusters
• Secondary electrons significant to DNA damage by
  low LET particles

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Nanodosimetry Results

• Particles tested include
• Protons 13.6 MeV (LET of 3.8 keV/mm in water)
• Alpha particles 4.25 MeV (LET of 107 keV/mm in
  water)
• Carbon ions 24.8 MeV (LET of 500 keV/mm in water)

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Nanodosimetry Results
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Further Research

• Validation of GEANT4 low energy electron
  transport models
• Utilise GEANT4 in the simulation of both the
  LLUMC beam-line and Nanodosimeter to improve
  accuracy
• Obtain NCDs for both homogeneous and
  heterogeneous structures

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Acknowledgements

• Anatoly Rosenfeld and the CMRP
• Dr Reinhard Schulte and the staff at LLUMC
• Dimitri Alexiev, Mark Reinhard and the staff at
  the Australian Nuclear Science and Technology
  Organisation
• Australian Institute of Nuclear Science and
  Engineering