Single Planar Detector Monte Carlo Simulations

# Single Planar Detector Monte Carlo Simulations

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## Single Planar Detector Monte Carlo Simulations

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1. Single Planar Detector Monte Carlo Simulations Andrew Mather arm@ns.ph.liv.ac.uk

2. Introduction - Simulation • Simulations run of a single 6 x 6 x 2 cm Germanium crystal. • Point isotropic source @ 10cm from the front face of the crystal, 10 million gamma’s emitted. (100-1000 keV step 10 keV) • The same (geometric wise) simulation reproduced in GEANT 4 & MCNP [G.Turk]. • Both simulations output all interaction positions and energies in the same format. • Results produced from this file for both codes using the same analysis software (Java).

3. Introduction - Packing • The analysis program uses a packing algorithm that packs any interaction points closer together than a specified amount into a single point. • Packing is used to make simulated results more comparable to real detectors. • Takes the average positions of the points to be packed and a sum of the energy deposited at each point. • Using 1mm currently as the maximum distance apart two interactions have to be for a “real” detector to be able to resolve them as two individual interactions.

4. Event defined as a gamma ray depositing some energy in the detector. • Interactions can be Compton or Photoelectric. • @ 511 keV Photo-peak events = ~ 2.5 interactions

5. Full energy event is an event where all the energy is deposited in the detector. • @ 511 keV : Geant = 29% MCNP = 36%

6. First Interaction – The actual first time the gamma-ray interacts. • Main Interaction – The interaction depositing the most energy. • @ 511 KeV : 70% of the time the first interaction = main interaction

7. When the first interaction isn’t the main interaction – What is the average distance between the two? • (Important to know if we make the assumption on real data to give and idea of how the imaging will be affected as a result)

8. Definition of Angle Detector Main Interaction First Interaction θ Point Source

9. ~ 8.7mm perpendicular from line joining source and first interaction position.

10. Current & Future Work • Simulation with two planar detectors and back to back 511 keV emitting source. • Look at imaging from interaction position file using both first interaction is the main interaction assumption and with the true first interaction. 2D Image reconstruction using BP Geant 4 visual of two detectors Image reconstruction from Geant 4 data