Transcript Compton camera tutorial

GAMOS tutorial
Compton Camera
Exercises
http://fismed.ciemat.es/GAMOS
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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 sequential
Use the commands of the previous exercise (only change what is
indicated)
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Compon Camera Exercise 1a: Compton
geometry
Scatterer: 0.5 cm X 0.5 cm X 1 cm Si crystal
Absorber: 0.5 cm X 0.5 cm X 2 cm CZT crystal
12 x 12 crystals in 1 block in each ring
2 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
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Compton Camera Exercise 1b: use
gamma source in water
Place gamma source homogeneously distributed in a
water sphere
Activity: 1 milliCurie
Energy: 141 keV
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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
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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
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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 events
How many are true single single events?
How many have more than 2 reconstructed hits?
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Compton Camera Exercise 3a: Energy
resolution
Set the photopeak energy gate as 1%
Observe differences in number of Compton imaging
events
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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
events
Observe differences in hits energy
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Compton Camera Exercise 3aii: Energy
resolution
Set the photopeak energy gate as 1%
Set the absorber detector energy resolution as 5%
Observe differences in number of Compton imaging
events
Observe differences in hits energy
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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%
Observe differences in number of Compton imaging
events
Observe differences in hits energy
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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
Observe differences in number of Compton imaging
events
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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
Observe differences in number of Compton imaging
events
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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
Observe differences in number of Compton imaging
events
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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
Observe differences in number of Compton imaging
events
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Compton Camera Exercise 3cii:
Measuring time
Set the measuring time of the absorber detector crystals
as 1 microseconds
Two signals in a crystal cannot be distinguised if they differe
less than a given amount
Observe differences in number of Compton imaging
events
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Compton Camera Exercise 3cii:
Measuring time
Set the measuring time of the scatterer and absorber
detector crystals as 1 microseconds
Two signals in a crystal cannot be distinguised if they differe
less than a given amount
Observe differences in number of Compton imaging
events
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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 detector
This 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.
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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 Algorithm
Only single/singles will be identified
Write out singles using
/gamos/setParam CC:EvtClass:DumpSingles 1
/gamos/setParam CC:EvtClass:DumpMultiples 0
Observe number of Compton imaging events
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Compton Camera Exercise 3b: Using
events with multiple interactions
Set the ComptonRecHitDist for the scatterer to 6 mm
and absorber to 0 mm.
/gamos/setParam CC:EvtClass:ComptRecHitDistScat 6.*mm
/gamos/setParam CC:EvtClass:ComptRecHitDistAbs 0.*mm
Use the NM1stHitByEnergy Algorithm
Only multiples/singles and singles/multiples will be
identified
Write out only the multiples using
/gamos/setParam CC:EvtClass:DumpSingles 0
/gamos/setParam CC:EvtClass:DumpMultiples 1
Observe number of Compton imaging events
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Compton Camera Exercise 3c: Using
events with multiple interactions
Set the ComptonRecHitDist for the scatterer to 0 mm
and absorber to 6 mm.
/gamos/setParam CC:EvtClass:ComptRecHitDistScat 0.*mm
/gamos/setParam CC:EvtClass:ComptRecHitDistAbs 6.*mm
Use the NM1stHitByEnergy Algorithm
Only singles/multiples and singles/multiples will be
identified
Write out only the multiples using
/gamos/setParam CC:EvtClass:DumpSingles 0
/gamos/setParam CC:EvtClass:DumpMultiples 1
Observe number of Compton imaging events
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Compton Camera Exercise 3d: Using
events with multiple interactions
Set the ComptonRecHitDist for the scatterer to 6 mm
and absorber to 6 mm.
/gamos/setParam CC:EvtClass:ComptRecHitDistScat 6.*mm
/gamos/setParam CC:EvtClass:ComptRecHitDistAbs 6.*mm
Use the NM1stHitByEnergy Algorithm
Multiples/multiples, singles/multiples, multiples/singles
and singles/multiples will be identified
Write out only the multiples using
/gamos/setParam CC:EvtClass:DumpSingles 0
/gamos/setParam CC:EvtClass:DumpMultiples 1
Observe number of Compton imaging events
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Compton Camera Exercise 3d: Using
events with multiple interactions
Set the ComptonRecHitDist for the scatterer to 0 mm
and absorber to 6 mm.
/gamos/setParam CC:EvtClass:ComptRecHitDistScat 0.*mm
/gamos/setParam CC:EvtClass:ComptRecHitDistAbs 6.*mm
Use the NM1stHitByXYZPos Algorithm
singles/multiples will be identified
Write out only the multiples using
/gamos/setParam CC:EvtClass:DumpSingles 0
/gamos/setParam CC:EvtClass:DumpMultiples 1
Observe number of Compton imaging events
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Introducción a GEANT4
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