RPC2001 VI Workshop on Resistive Plate Chamber
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Transcript of RPC2001 VI Workshop on Resistive Plate Chamber
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RPC2001 VI Workshop on Resistive Plate Chamber
Perspectives in Positron Emission Tomography (PET) with RPCs
A.Blanco (1,5), P.Fonte (1,4), I.Lopes (1), R.Marques (1,2), V.Peskov (3), A.Policarpo (1,2), V.Tchepel (1)
(1) LIP, laboratorio de Instrumentacao e Fisica Experimental de Particulas(2) Departamento de Física da Universidade de Coimbra
(3) KTH, Stockholm(4) ISEC, Coimbra, Portugal.
(5) GENP, Dept. Fisica de Particulas, Univ. Santiago de Compostela, Spain.
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What is and How PET works Positron Emission Tomography (PET) is a radiotracer imaging technique, in which tracer compounds labelled with positron emitting radionuclides are injected into the subject of the study. These tracers compounds can then be used to track biomedical and physiological process.
RPC2001 VI Workshop on Resistive Plate Chamber
Coincidence events can be stored in arrays corresponding to projections through the object and reconstructed using standard tomographic techniques.
Perspectives in Positron Emission Tomography (PET) with RPC´s Alberto Blanco
Unstable parent nucleus
Proton decays to neutron in nucleus
Two anti-parallel 511 keV photons produced
Positron combines with electron and annihilates
Resulting image shows the tracer distribution throughout the object of the study.
positron and neutrino emitted
Electronic
Coincidence
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RPC2001 VI Workshop on Resistive Plate Chamber
TOF-PET
Perspectives in Positron Emission Tomography (PET) with RPC´s Alberto Blanco
10ysensitivitoftImprovemen size[mm]object *2
][ pst
a) Reconstructed image without TOF. b) Reconstructed image using TOF information
[NIM A 471(2001) 200-204]
a) b)
2
][][
psmmX t
FWHM
X = 80 cm TOF = 2.6 ns
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RPC2001 VI Workshop on Resistive Plate Chamber
The basic idea
Incident photon
e-
Compton or photoelectric interaction
A previous work
“The Rutherford Appleton Laboratory´s Mark I Multiwire Proportional Counter Position Camera” J.E. Bateman et al. NIM 225 (1984) 209-231
....
High quantum efficiency material
Stacked plates
Gas gap
Quantum
Efficiency?
Geant simulations
Perspectives in Positron Emission Tomography (PET) with RPC´s Alberto Blanco
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RPC2001 VI Workshop on Resistive Plate Chamber
Efficiency of a MWPC with 21 lead plates (250 um)
[from J.E. Bateman NIM 221 (1984 131-141]
5.5%
6.0%
6.5%
7.0%
7.5%
8.0%
8.5%
9.0%
0 100 200 300 400Thickness (um)
Qu
an
tum
Eff
icie
nc
y
.
Geant 4
J.E. Bateman
Experimental data Geant 4Can we trust Geant 4?
Perspectives in Positron Emission Tomography (PET) with RPC´s Alberto Blanco
Geant seems accurate
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RPC2001 VI Workshop on Resistive Plate Chamber
10-2
10-1
100
10110
-4
10-2
100
Energy (MeV)
Ra
nge
(g
/cm
2)
Ranges of electrons in Aluminium
From NIST (National Institute of Standards and Technology).
2
Perspectives in Positron Emission Tomography (PET) with RPC´s Alberto Blanco
Experimental data Geant 4Can we trust Geant 4?
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RPC2001 VI Workshop on Resistive Plate Chamber
Perspectives in Positron Emission Tomography (PET) with RPC´s Alberto Blanco
Experimental data Geant 4Can we trust Geant 4?
Absorption curves of monoenergetic electrons of various energies in aluminium .
[From J. Marshall and A. G. Ward, Can. J. Research A15, 39 (1937)]
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Measured projected positron range distribution
Isotope 18F 11C 68Ga 82Rb
Maximun +
energy (MeV)0.64 0.96 1.90 3.35
FWHM (mm) 0.13 0.13 0.31 0.42
RPC2001 VI Workshop on Resistive Plate Chamber
Perspectives in Positron Emission Tomography (PET) with RPC´s Alberto Blanco
82Sr
68Ga11C
18F
mm water equivalent
Proj
ecte
d P
SF d
ue to
ran
ge o
nly
From “Mathematical removal of positron range blurring in high resolution tomography” Derenzo et all. IEEE NS, vol 33
No1”
Experimental data Geant 4Can we trust Geant 4?
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RPC2001 VI Workshop on Resistive Plate Chamber
The basic idea
30 Stacked plates
0%
2%
4%
6%
8%
10%
12%
14%
0 200 400 600 800 1000 1200Thickness (um)
Qua
ntu
m E
ffic
iency
.
Lead
Lead GlassLead Acrylic
Data from the simulation on Geant 4 showing quantum efficiency vs. plate thickness for tree different materials and 30 stacked plates.
....
Stacked plates
Geant 4 simulation
Mechanically more convenient
Perspectives in Positron Emission Tomography (PET) with RPC´s Alberto Blanco
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RPC2001 VI Workshop on Resistive Plate Chamber
The basic idea
100 stacked plates
0%
5%
10%
15%
20%
25%
30%
35%
0 200 400 600 800 1000 1200Thickness (um)
Qua
ntu
m e
ffic
iency
.
LeadLead GlassLead Acrylic
Data from the simulation on Geant 4 showing quantum efficiency vs. plate thickness for tree different materials and 100 stacked
plates.
Perspectives in Positron Emission Tomography (PET) with RPC´s Alberto Blanco
....
Stacked plates
Geant 4 simulation
Mechanically more convenient
22 %
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RPC2001 VI Workshop on Resistive Plate Chamber
The detector blocks
X-Codification
Z-C
odif
icat
ion
Y-Cod
ifica
tion
Time
Perspectives in Positron Emission Tomography (PET) with RPC´s Alberto Blanco
• n - stacked counters built with a high quantum efficiency material
• Tridimensional localisation of the photon interaction point.
• Time measurement independent of position measurement yielding a 50 ps resolution.
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RPC2001 VI Workshop on Resistive Plate Chamber
The detector blocks
X leftX right
Time signalHV
Y-strips(on PCB)
RC
passive netw
ork
RC passive network
X-strips(deposited on glass)
out left
out right
10 strips for eachcoordinate at 4 mm pitch
Perspectives in Positron Emission Tomography (PET) with RPC´s Alberto Blanco
TESTED
Other position readout methods also possible
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RPC2001 VI Workshop on Resistive Plate Chamber
Expected spatial resolution
1 cm
Perspectives in Positron Emission Tomography (PET) with RPC´s Alberto Blanco
Reconstructed point spread function [PSF] of the source.
1) RPC PET (100 m counter resolution) 180 m FWHM
2) RPC PET (500 m counter resolution) 490 m FWHM
No parallax effect
Geant 4 simulation of 3 point-like positron source (max energy 640 keV) surrounded by a water sphere and seen by a RPC-PET with spatial resolution of 100m.
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RPC2001 VI Workshop on Resistive Plate Chamber
Human PET Small animal PET
- TOF capability is of no value due to the small dimension of the object.
+ An higher radiation dose may be acceptable, with animals.
+ The lack of energy resolution play a minor role. The compton interactions in the object are almost negligible.
+ TOF capability compensates the low efficiency.
- The lack of energy resolution increase the compton background.
The two possible applications
Perspectives in Positron Emission Tomography (PET) with RPC´s Alberto Blanco
+ Tridimensional localisation of the interaction point of photons, reducing the parallax effect, with high spatial resolution providing a good image quality.
+ The low cost.
+ The excellent timing allows to improve the background rejection.
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RPC2001 VI Workshop on Resistive Plate Chamber
The first prototypea small animal PET
• 2 head rotatory system
• 16 stacked glass-metal counters 2%
• 32 1mm wide X pickup strip
• Time measurement not yet included
4x3x1 cm3
Object
The detector in Geant.
Perspectives in Positron Emission Tomography (PET) with RPC´s Alberto Blanco
Glass
Copper
Copper strips
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RPC2001 VI Workshop on Resistive Plate Chamber
Conclusions
Perspectives in Positron Emission Tomography (PET) with RPC´s Alberto Blanco
Simulations suggest that RPC´s could be used for TOF-PET
Low cost large field of view increased sensitivity
High spatial resolution provides high definition images