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Single Planar Detector Monte Carlo Simulations

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Single Planar Detector Monte Carlo Simulations

Andrew Mather

arm@ns.ph.liv.ac.uk

- 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).

- 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.

- 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

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

- 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

- 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)

Definition of Angle

Detector

Main Interaction

First Interaction

θ

Point Source

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

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