pedro arce introducción a geant4 1 gamos tutorial compton camera exercises

Pedro Arce Introducción a GEANT4 1

GAMOS tutorial

Compton Camera

Exercises

http://fismed.ciemat.es/GAMOS


Compton Camera Simulation Exercises

Ex. 1: Define Compton camera geometry

Ex. 2: Obtain information about what is happening in the simulation

Ex. 3: Apply Detector effects

The exercises are sequentialUse the commands of the previous exercise (only change what is indicated)


Compon Camera Exercise 1a: Compton geometry

Scatterer: 0.5 cm X 0.5 cm X 1 cm Si crystalAbsorber: 0.5 cm X 0.5 cm X 2 cm CZT crystal12 x 12 crystals in 1 block in each ring2 cm separation between scatterer ring and absorber ring

Source of 141 keV photons at (0,0,0) towards the X axis, 5 cm from scatterer ring


Compton Camera Exercise 1b: use gamma source in water

Place gamma source homogeneously distributed in a water sphere

Activity: 1 milliCurieEnergy: 141 keV


Compton Camera Exercise 2a: obtain information

Make info about the physics processes that occur

Make the crystal sensitive detector and produce signals (hits)

Obtain histograms about hits quantities (energy, position, …)

Get detailed info about Compton and Photoelectric effect in crystals


Compton Camera Exercise 2b: standard physics

Use GEANT4 standard electromagnetic package, instead of low energy electromagnetic package

Observe differences in energy distribution

Observe differences in processes occurring

Observe differences in CPU time


Compton Camera Exercise 2c: Classify events as Compton Imaging events

A Compton imaging event is defined as one that has at least one signal in at least one scatterer crystal and one absorber crystal, with a summed energy approximately equal to the source energy

Classification is done looking at the reconstructed hits

Define a RecHitBuilder that builds hits for each crystal and defines the position as the centre of the pixel

Count % of Compton imaging eventsHow many are true single single events?

How many have more than 2 reconstructed hits?


Compton Camera Exercise 3a: Energy resolution

Set the photopeak energy gate as 1%

Observe differences in number of Compton imaging events


Compton Camera Exercise 3ai: Energy resolution

Set the photopeak energy gate as 1%Set the scatterer detector energy resolution as 1%

Observe differences in number of Compton imaging eventsObserve differences in hits energy


Compton Camera Exercise 3aii: Energy resolution

Set the photopeak energy gate as 1%Set the absorber detector energy resolution as 5%



Compton Camera Exercise 3aiii: Energy resolution

Set the photopeak energy gate as 1%Set the scatterer detector energy resolution as 1% AND the absorber detector energy resolution as 5%



Compton Camera Exercise 3bi: Dead time

Set the dead time of scatter detector crystals as 1 microseconds

When a crystal takes signal, the full 12x12 crystal array becomes dead for a time



Compton Camera Exercise 3bii: Dead time

Set the dead time of absorber detector crystals as 1 microseconds

When a crystal takes signal, the full 12x12 crystal array becomes dead for a time



Compton Camera Exercise 3biii: Dead time

Set the dead time of scatterer and absorber detector crystals as 1 microseconds

When a crystal takes signal, the full 12x12 becomes dead for a time



Compton Camera Exercise 3ci: Measuring time

Set the measuring time of the scatterer detector crystals as 1 microseconds

Two signals in a crystal cannot be distinguised if they differe less than a given amount



Compton Camera Exercise 3cii: Measuring time

Set the measuring time of the absorber detector crystals as 1 microseconds




Compton Camera Exercise 3cii: Measuring time

Set the measuring time of the scatterer and absorber detector crystals as 1 microseconds




Compton Camera Exercise 2c: Using events with multiple interactions

Compton imaging is done on 2 detector events, so when there are multiple interactions within a detector event it is necessary to identify the position and energy of the interaction of interest, to reduce to one interaction in each detectorThis can be achieved via “Identifying Compton Interactions” using various algorithms It may be appropriate to use the interaction energy, position or separations to identify the 1st interaction.


Compton Camera Exercise 3a: Using events with multiple interactions

Set the ComptonRecHitDist for the scatterer and absorber to 0 mm.

/gamos/setParam CC:EvtClass:ComptRecHitDistScat 0.*mm/gamos/setParam CC:EvtClass:ComptRecHitDistAbs 0.*mm

Use the NM1stHitByEnergy AlgorithmOnly single/singles will be identifiedWrite out singles using

/gamos/setParam CC:EvtClass:DumpSingles 1/gamos/setParam CC:EvtClass:DumpMultiples 0

Observe number of Compton imaging events


Compton Camera Exercise 3b: Using events with multiple interactions

Set the ComptonRecHitDist for the scatterer to 6 mm and absorber to 0 mm.


Use the NM1stHitByEnergy AlgorithmOnly multiples/singles and singles/multiples will be identifiedWrite out only the multiples using




Compton Camera Exercise 3c: Using events with multiple interactions



Use the NM1stHitByEnergy AlgorithmOnly singles/multiples and singles/multiples will be identifiedWrite out only the multiples using




Compton Camera Exercise 3d: Using events with multiple interactions



Use the NM1stHitByEnergy AlgorithmMultiples/multiples, singles/multiples, multiples/singles and singles/multiples will be identifiedWrite out only the multiples using




Compton Camera Exercise 3d: Using events with multiple interactions



Use the NM1stHitByXYZPos Algorithmsingles/multiples will be identifiedWrite out only the multiples using



pedro arce introducción a geant4 1 gamos tutorial compton camera exercises

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