Prompt GammaRay Imaging by GEANT4

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Prompt Gamma-Ray Imaging by GEANT4

• Libai Xu
• Center of Engineering Applications of
  Radioisotopes
• Department of Nuclear Engineering
• North Carolina State University
• OCT. 20. 2005

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OUTLINE

• Introduction to Prompt Gamma-Ray Imaging
• Introduction to Geant4
• PGI Simulation by Geant4
• Results
• Conclusions

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• Introduction to Prompt Gamma-Ray Imaging
• Small animal imaging
• System Diagram
• Potential of PGI Over PET
• Introduction to Geant4
• PGI Simulation by Geant4
• Results
• Conclusions

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Why small animal imaging?

• Why small animal imaging is important?
• It is an invasive tool to build animal models of
  human diseases.
• Save animals, reduce cost
• Get more complete data, especially for
  longitudinal studies
• Currently available imaging systems for small
  animals
• Anatomical Imaging
• Micro-CT, MRI, Ultrasound
• Detailed info about tissue structure and
  composition
• Functional Imaging
• Micro-PET, Micro-SPECT
• Spatial distribution or evolution of radio
  nuclides in the body

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INTRODUCTION-gtSystem Diagram
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INTRODUCTION-gt Potential of PGI Over PET

• Co-registration procedure for PGI with neutron
  imaging
• Expansion from ingested radioisotopes to
  non-radioactive elements like Gd, Cd, N, and Hg
  tagged compounds.
• The natural distribution of selected compounds
  and the distribution of specific compounds that
  are deliberately introduced.
• Positron range.

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• Introduction to Prompt Gamma-Ray Imaging
• Introduction to Geant4
• History
• Physics Models
• Visualization
• PGI Simulation by Geant4
• Results
• Conclusions

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GEANT4-gtHistory

• Geant4 was started as RD44 (1994) at CERN with
  aim to provide a detector simulation toolkit for
  HEP based on object oriented software technology.
• The heart of Geant4 is an abundant set of physics
  models
• Applications are in particle physics, nuclear
  physics, accelerator design, space engineering,
  and medical physics.

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Geant4 Collaboration
HARP
PPARC
Univ. Barcelona
Lebedev
Collaborators also from non-member institutions,
including Budker Inst. of Physics IHEP
Protvino MEPHI Moscow Pittsburg University
Helsinki Inst. Ph.
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GEANT4-gtPhysics model
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Visualization
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• Introduction to Prompt Gamma-Ray Imaging
• Introduction to Geant4
• PGI Simulation by Geant4
• If Geant4 is capable to do this job?
• Geant4 modification
• Prompt gamma-ray imaging simulation
• Results
• Conclusions

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IF Geant4 can do this job?

• If Geant4 can simulate coincident prompt gamma
  rays?
• Geant4 has two methods to produce prompt gamma
  rays
• Follow the full transition scheme
• Follow the energy-intensity table

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• Geant4 can simulate coincident prompt gamma rays,
  but using different physics model and data
  libraries to generate prompt gamma rays.

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Modify neutron capture reaction model

• Modify Geant4 to generate prompt gamma rays which
  are agreed with ENSDF
• Physics model
• Data libraries for H, C, N, O, Na, Mg, Al, Si, P,
  S, Cl, K, Ca, Fe, Zn, Hg .

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Prompt gamma imaging simulation
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• Introduction to Prompt Gamma-Ray Imaging
• Introduction to Geant4
• PGI simulation by Geant4
• Results
• Yields
• Imaging
• Conclusions

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Yields
Detector
Thermal neutron
tissue
Detector
Purposes 1) Prompt gamma yields by each
component 2) Select some coincident gamma rays
for each component as their main recognizable
features.
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Capture reactions for each component in soft
tissue (per 1.E6 thermal neutrons)

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sample
Detector plane
Pinhole
Coincident detector
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370kev prompt gamma-ray from Hg
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6Mev prompt gamma rays from Hg
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Why pinhole doesnt work?

• Useful for low energy such as 140kev
• Attenuation of 3mm Lead
• For 140kev
• Exp(-1.91cm2/g11.350.3)0.0015
• For 370kev
• Exp(-0.26cm2/g11.350.3)0.41
• For 6Mev
• Exp(-0.043811.350.3)0.86

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Conclusions

• Geant4 has the ability to simulate coincident
  prompt gamma rays.
• Geant4 (n,r) capture reaction data libraries need
  to be modified to be agreed with ENSDF. (around
  10min for each isotopes)
• Speed 10hours/1million capture reactions.
• No physics related variance reduction techniques.

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Future work

• Variance Reduction Techniques
• Looking for new imaging collimators