maurizio conti, siemens molecular imaging, knoxville, tennessee, usa
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1 Maurizio Conti: Introduction to PET1 Maurizio Conti: Introduction to PET - reproduction authorized for educational purposes only
Maurizio Conti, Siemens Molecular Imaging,
Knoxville, Tennessee, USA
Detectors for PET
2 Maurizio Conti: Detectors for PET - reproduction authorized for educational purposes only
Summary
introduction inorganic scintillators TOF detectors new light sensors and scintillators
3 Maurizio Conti: Detectors for PET - reproduction authorized for educational purposes only
Detection process:
positron emission and annihilation two emission
interaction in the patient body and absoption or scatter
interaction in the detectors (scintillator+photodetector or solid state devices)
Most common detector:
inorganic scintillator + Photo Multiplier Tube (PMT)
4 Maurizio Conti: Detectors for PET - reproduction authorized for educational purposes only
coincidence
e+
e-
detector
Light detector
5 Maurizio Conti: Detectors for PET - reproduction authorized for educational purposes only
detector: scintillator
PMT
detector: scintillator
Light detector(APD, SiPM)
detector = solid state detector(Si, CZT)
Detector components
6 Maurizio Conti: Detectors for PET - reproduction authorized for educational purposes only
E
X = A / (A + B)
X1 = 100 / (100 + 0) = 1 X2 = 55 / (55 + 45) = 0.55
A B
Detector architecture: the block
7 Maurizio Conti: Detectors for PET - reproduction authorized for educational purposes only
BA
AX
DC
CY
Anger Logic
Y
X
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1986 - ECAT with Block Detector
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PMTs
PMTs 52 cm
36 cm
light guide scintillator
scintillator
Detector architecture: the panel
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Compton Effect
e-
E
E’
Eel
E -
E’
EC
)cos1(1'
2
mchvhv
hv
11 Maurizio Conti: Detectors for PET - reproduction authorized for educational purposes only
Photoelectric Effect
e-
E
E
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Interaction cross sections
LSO LaBr3
Compton
photoelectric
511 keV 511 keV
x
13 Maurizio Conti: Detectors for PET - reproduction authorized for educational purposes only
A good detector must have:
high density and Z: ph ZandComp Z
high light output: energy and time resolution 1 / N1/2
short rise time and decay time: time resolution and dead time
if scintillator, > 400 nm emission wavelength (better for PMTs)
solid technology: not hygroscopic, uniform, easy to make, low cost, etc
14 Maurizio Conti: Detectors for PET - reproduction authorized for educational purposes only
15 Maurizio Conti: Detectors for PET - reproduction authorized for educational purposes only
Characteristics of Selected Scintillators
16 Maurizio Conti: Detectors for PET - reproduction authorized for educational purposes only
NEC, the noise equivalent count rate,
NEC = [(True+scatter)*(1-scf)]2/[True+scatter + randoms]
• NEC is related with image quality. ”The higher the NEC the better the images”.
17 Maurizio Conti: Detectors for PET - reproduction authorized for educational purposes only
Search for new scintillators
Ce3+ 5d-4f transition
18 Maurizio Conti: Detectors for PET - reproduction authorized for educational purposes only
P. Dorenbos, Presentedat SCINT09, JejuIsland, Korea, June 2009
Search for new scintillators
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First Paper on LSO
Ce3+ 5d-4f transition
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LSO Energy Spectrum
0
1000
2000
3000
4000
5000
6000
7000
8000
0 200 400 600 800 1000
176Lu backgroundLSO @511keV
energy
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LSO manufacturing
22 Maurizio Conti: Introduction to PET22 Maurizio Conti: Introduction to PET - reproduction authorized for educational purposes only
Comparing fast scintillators with TOF PET potentiality
(experimental work, presented at SORMA conference, 2008)
Emission and excitation spectraDecay time Absolute light output Time resolutionFigure of merit for TOF PET
23 Maurizio Conti: Introduction to PET23 Maurizio Conti: Introduction to PET - reproduction authorized for educational purposes only
Materials
Scintillator composition sample size surface manufacturer
LSO(Ce) Lu2SiO5
5x5x5mm3,
10x10x10mm3as cut University of Tennessee
LuAG(Pr) Lu3Al5O12
5x5x5mm3,
10x10x10mm3
as cut or
polished
University of Tennessee,
Furukawa Co. Ltd.
LuYAP(Ce) Lu0.52Y0.48AlO3
5x5x5mm3,
10x10x10mm3polished SAES Srl.
LaBr3(Ce) LaBr3
cylinders, 13 mm dia,
13 mm height
polished,sealed,
with reflectantSaint-Gobain
LaCl3(Ce) LaCl3cylinders, 13 mm dia,
13 mm height
polished,sealed,
with reflectant
Saint-Gobain
24 Maurizio Conti: Introduction to PET24 Maurizio Conti: Introduction to PET - reproduction authorized for educational purposes only
Emission and excitation spectra
0
2000
4000
6000
8000
10000
12000
200 250 300 350 400 450 500
w avelength (nm)
LuAG emission LuAG excitation
0
500
1000
1500
2000
2500
200 250 300 350 400 450 500
w avelength (nm)
LuYAP emission LuYAP excitation
0
20
40
60
80
100
120
140
160
200 250 300 350 400 450 500
w avelength (nm)
LaBr emission LaBr excitation
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
200 250 300 350 400 450 500
w avelength (nm)
LaCl emission LaCl excitation
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
200 250 300 350 400 450 500
w avelength (nm)
LSO emission LSO excitation
25 Maurizio Conti: Introduction to PET25 Maurizio Conti: Introduction to PET - reproduction authorized for educational purposes only
Decay time measurement
LSO
one component, 30-37nsPMT=XP2020Q Cs137 source
Trigger (anode)
Measure (anode)
Amp474(x10)
CFD935
delayCFD935
TAC567
start
stop
MCA
26 Maurizio Conti: Introduction to PET26 Maurizio Conti: Introduction to PET - reproduction authorized for educational purposes only
Decay time measurement
LuYAP
fast component, 16 ns (57%) 145 ns (22% 594 ns (21%)
LuAG
fast component, 18 ns (77%) 530 ns (23%)
27 Maurizio Conti: Introduction to PET27 Maurizio Conti: Introduction to PET - reproduction authorized for educational purposes only
Decay time measurement
LaBr3
one component, 17 ns
LaCl3
fast component, 18 ns (70%) 125 ns (21%) 220 ns (9%)
28 Maurizio Conti: Introduction to PET28 Maurizio Conti: Introduction to PET - reproduction authorized for educational purposes only
Absolute light output
Self-absorption observed: lower light output in larger crystals
Scintillator
Light
output
(ph/MeV)
fast
component (%)
Light output
fast (ph/MeV)
LSO(Ce) 32000 100 32000
LuAG(Pr) 18000 77 13900
LuYAP(Ce) 16000 57 9200
LaBr3(Ce) 58000 100 58000
LaCl3(Ce) 29000 70 20600 Lower than in data sheet
PMT=H3177
Spectroscopy Amplifier Ortec 672 (3s shaping)Pre Amplifier Canberra 2005
dynodeMCATukan-8k Cs137 source
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Time resolution measurement
D#1 (anode)
CFD935
delayCFD935
TAC567
start
stop
MCA
Amp855(x40/5,1.5us)
SCA551
SCA551
FastCoinc414A
PreAmp113(100pF)
strobe
D#2 (anode)
D#1 (dynode)
D#2 (dynode)
FWHM of the gaussian fit
PMT=XP2020QNa22 source
30 Maurizio Conti: Introduction to PET30 Maurizio Conti: Introduction to PET - reproduction authorized for educational purposes only
0.0
100.0
200.0
300.0
400.0
500.0
600.0
0.000 0.010 0.020 0.030 0.0401/sqrt(N)
Tim
e R
es
olu
tio
n (
ps
)
Time resolution measurement
LuYAP
LuAG
LaClLSO
LaBr
N= ph-e (includes E and QE)
31 Maurizio Conti: Introduction to PET31 Maurizio Conti: Introduction to PET - reproduction authorized for educational purposes only
N= ph-e (includes E and QE)
Figure of merit to compare scintillators for TOF PET
Fast is not enough!
Needs to be bright and dense!
32 Maurizio Conti: Introduction to PET32 Maurizio Conti: Introduction to PET - reproduction authorized for educational purposes only
Figure of merit (conventional)
PPFe x )1(
2
Image quality (or SNR) depends on number of coincidence counts in the scan
Detection efficiency
Deposited energy (MeV)
Coincidence efficiency
PPF=PhotoPeakFraction
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Hyman theory
pheNPMThHt
),,(
PMT noise/gain
Discriminator level
Decay time
1
),,( PMThH
34 Maurizio Conti: Introduction to PET34 Maurizio Conti: Introduction to PET - reproduction authorized for educational purposes only
Time resolution estimate
pheNt
0 < < 1
PET scanner system time resolution
pheNPMThHt
),,(
pheNt
pheNtt
35 Maurizio Conti: Introduction to PET35 Maurizio Conti: Introduction to PET - reproduction authorized for educational purposes only
Fast Photomultipliers for TOF PETT. Szczesniak, M. Moszynski, L. Swiderski, A. Nassalski, P. Lavoute, M.Kapusta2007 TNS conf record
Hyman theory
plastic
CsF2
LaBr3
LuAP
LaCl
YAP
LSO
LGSO
NaI
36 Maurizio Conti: Introduction to PET36 Maurizio Conti: Introduction to PET - reproduction authorized for educational purposes only
Figure of merit (with TOF)
Nt
t
DGTOF
TOF sensitivity gain or amplification
Conventional sensitivity 2Sens
N
GTOF 22Overall sensitivity of TOF PET scanner
N
GTOF
37 Maurizio Conti: Introduction to PET37 Maurizio Conti: Introduction to PET - reproduction authorized for educational purposes only
Figure of merit for TOF PET
Scintillatordecay time
(ns)
N(fast)
(ph/MeV)
(cm-1)
photopeak
fraction
(2 cm)sqrt(N
Lu2SiO5 37 32000 0.821 0.73 0.351 29.40 10.19
Lu3Al5O12 18 13900 0.710 0.77 0.345 27.79 9.58
Lu0.5Y0.5AlO3 16 9200 0.651 0.73 0.280 23.98 6.70
LaBr3 17 58000 0.432 0.43 0.061 58.41 3.56
LaCl3 18 20600 0.338 0.51 0.064 33.83 2.18
nonTOF TOF
38 Maurizio Conti: Introduction to PET38 Maurizio Conti: Introduction to PET - reproduction authorized for educational purposes only
Figure of merit for TOF PET scintillators
LaBr
LuYAP
LuAG
LaCl
LSO
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1A
rbit
rary
uni
ts
efficiency TOF gain eff*GTOF
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DenseBrightFast
LSO/LYSO is dominating now….
N
tGTOF
222 1
dense bright
fast
New scintillators for TOF PET ?
40 Maurizio Conti: Introduction to PET40 Maurizio Conti: Introduction to PET - reproduction authorized for educational purposes only
New scintillators for TOF PET ?
Derenzo and Moses (LBNL, Berkeley):Systematic search of new scintillators, combining powders and testing with X-rays microcrystals
Hundreds of compounds tested.
41 Maurizio Conti: Detectors for PET - reproduction authorized for educational purposes only
New scintillators for TOF PET ?
42 Maurizio Conti: Detectors for PET - reproduction authorized for educational purposes only
New scintillators for TOF PET ?
New approaches:
Crystals with a highly populated donor band (ZnO)
Nanocrystals with quantum dots
Make use of Cerenkov light
Improve light collection with photonic crystals
43 Maurizio Conti: Detectors for PET - reproduction authorized for educational purposes only
LSO crystal
2.8mm
1.3
mm
0.6
mm
100x100m2
10 m2.5 m
Improve light collection with photonic crystals
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Improve light collection with photonic crystals
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When will SiPM get there ? ….
FastEfficientCount rate capabilitySmall dead areas, compact and scalable
New photodetectors for TOF PET ?
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SiPM: new photodetectors for TOF PET ?
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SiPM: new photodetectors for TOF PET ?
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SiPM: new photodetectors for TOF PET ?
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SiPM: new photodetectors for TOF PET ?
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SiPM: new photodetectors for TOF PET ?
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SiPM: new photodetectors for TOF PET ?
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SiPM: new photodetectors for TOF PET ?
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