SmartPET ½ Day Meeting

Transcription

SmartPET ½ Day Meeting
10:00
10:15
10:45
11:00
11:15
12:00
12:30
Welcome and Coffee
Overview of SmartPET project
Pulse Shape Analysis
Wavelet Analysis
PET Images from SmartPET
Tour of the Lab
Lunch
Helen Boston
Ren Cooper
David Scraggs
Andy Mather
SmartPET Overview : Helen Boston
SmartPET Overview
Helen Boston
Overview
•
•
•
•
•
•
•
Overview of the SmartPET project
The requirements of the system
The detectors
The design of the SmartPET system
Initial characterisation the detector
Initial Compton images
Pulse shape analysis (PSA) – Ren Cooper
• rjc@ns.ph.liv.ac.uk
• Wavelet analysis – David Scraggs
• dps@ns.ph.liv.ac.uk
• Image reconstruction – Andy Mather
• arm@ns.ph.liv.ac.uk
SmartPET Project
•
•
•
Investigate use of Ge for purpose of PET
Aim is to show proof of principle for a small animal PET
demonstrator
• Can we use Ge properties to get a better image in a
shorter time?
• As energy resolution is very good, we can use much
more of the data
Require a detector system with good energy and time
resolution, and some way of getting good spatial
resolution
SmartPET Detectors
• Each detector houses an electrically segmented orthogonal strip
Germanium detector (DSSGeD)
• The active crystal volume is 60 x 60 x 20 mm
• 24 readouts per detector
• Strip pitch is 5mm
• Natural spatial resolution 5 x 5 x 20mm
• Electrical segmentation so
no loss in efficiency
• Each detector has a 72
hour LN dewar attached
• All angle dewar
• Mechanical cooler being
investigated
SmartPET Detectors
In Lab
SmartPET: Design
60 mm
5 mm
50 mm
60 mm
91 cm
BGO Comparison
• Hexagonal BGO : thickness 25mm, length 70mm,
tapered to 5º
Bank 1FWHM
detector 4=: 3.3keV
96.8keV
• FWHMBGO BGO
= 96.8keV,
DC06
4000
Number of Counts
3500
3000
FWHM =
96.8keV
2500
2000
1500
1000
500
0
0
200
400
Energy (keV)
600
800
Initial measurements
• Analogue system
•
•
•
•
HV – ORTEC 659 NIM unit
± 12V supplied by NIM bin
671 ORTEC spectroscopic amplifier unit
ORTEC software for data collection
• Measurements
•
•
•
•
Check to see signal present for each strip
Measure DC offset and sensitivity
Resolution measurements using a variety of sources
Possible problems investigated further
Scope
Spec
Amp
Maestro
241Am
Data
300000
¾AC
∼0.3microns
∼Strip gap 300microns
¾DC
∼50microns
∼Strip gap 180microns
10000
Number of Counts
250000
17.8
8000
DC06
26.3
20.8
6000
200000
4000
150000
2000
0
100000
10
20
30
50000
0
0
250000
200000
26.3
4000
0
10
20
30
50000
0
0
60
•AC06
•FWHM = 1.45 keV
•DC06
•FWHM = 1.12 keV
8000
100000
40
20.8
12000
150000
20
Energy (keV)
16000
Number of Counts
17.8
AC06
20
40
Energy (keV)
60
152Eu
Efficiency
0.0003
AC06 Absolute Efficiency
0.00025
Efficiency
0.0002
0.00015
0.0001
0.00005
0
0
200
400
600
800
1000
1200
1400
1600
Energy (keV)
Absolute efficiency at 511keV is 0.1%
Equates to 1 in 1000 events being collected fully
Energy
(keV)
FWHM
122
1.78
244
1.84
344
1.88
779
2.12
964
2.34
1111
2.40
1408
2.90
60Co
•AC06
•FWHM = 2.39 keV
•AREA = 1768 ± 56
•PT = 1.86%
•DCO6
•FWHM = 3.75 keV
•AREA = 2726 ± 80
•PT = 2.25%
60
Co results for AC06
200
Number of Counts
Data
150
100
50
0
1150
1200
1250
1300
1350
Energy (keV)
1400
200
Number of Counts
1100
60
Co result for DC06
150
100
50
0
1150
1200
1250
1300
Energy (keV)
1350
1400
Detector Characterisation
What is characterisation?
• Provides a full description of the detector
response
• Full characterisation of germanium crystals
– Detailed source scans
T90
90%
T30
∆E
30%
10%
Singles Scan Sources
• 1mm Tungsten collimation
• 1mm step positions
• Sources
• 1GBq 241Am annular source – 25cps
• 1850MBq 57Co source (pellet) – 67cps SPET1
• 70.21MBq 137Cs – 35cps SPET1
• Scans
•
•
•
241Am
120 seconds at each position (AC and DC)
57Co 60 seconds (AC and DC), 120 seconds (side)
137Cs 180 seconds
241Am
AC
DC
• XY position information
• 1mm steps, 120sec pp
AC01
AC12
DC12
DC01
Energy, position Mγ =1 gated
AC face scan
• 60keV gate
• 6keV wide gate
DC
Side
ScanAC
DC12
1
AC
2
0
C
A
1
DC01
57Co
AC DC
• HT coupling capacitors
• Maximum intensity close
to centre depth
Side scan
• AC electrodes visible
AC01
AC12
57Co
DC12
DC face scan
50
40
30
40
50
60
70
80
90 100
110
100
90
80
70
60
50
40
30
20
10
70
60
50
50
40
40
R ise tim e (ns)
T30
Y (m m )
DC01
AC12
Y (m m )
AC01
R ise tim e (ns)
AC coupled side
30
30
40
20
50
60
70
80
90 100
10
X (mm)
X (mm)
40
30
40
50
60
70
80
X (mm)
90 100
140
120
50
100
40
30
40
80
60
50
60
70
80
X (mm)
90 100
40
20
R ise tim e (ns)
160
Y (m m )
50
200
180
160
140
120
100
80
60
40
20
R ise tim e (ns)
T90
Y (m m )
DC coupled side
57Co
200
100
AC
DC
90
80
AC
DC
190
180
50
40
AC side
60
Risetime (ns)
170
70
DC side
Risetime (ns)
X=77 Risetimes
160
150
140
130
30
120
20
110
10
100
0
2
4
6
8
10 12 14 16 18 20
Depth (mm)
T30
0
2
4
6
8
10 12 14 16 18 20
Depth (mm)
T90
Position Resolution
• From X-Y position information spatial resolution achieved
using PSA 1mm in X and Y
• Using sensitivity in T30 for both the AC and DC
60
40
20
0
0
DC side
Diference in T30AC - T30DC
80
5
10
15
-20
-40
-60
y = 0.0295x3 - 1.2558x2 + 8.1028x + 58.5
Depth (mm)
20
Compton Camera
• 10µCi 152Eu
• 60mm from SPET1
• Source rotated
• Zero degrees in 15º
steps up to 60º
• Detector separation
• 3 – 11cm in 2cm steps
• Gates set on energies
• 779, 1408keV
• 2 22Na sources at
different x and y
Compton Scattering
Scatter
Absorber
Event 1
β
θ
(Ee ,x1)
Event 2
(Es, x2)
α
Source somewhere on cone
•
•
•
Electronic collimation
γ must have a trajectory along a cone surface,
described by axis : β and θ
Energy of incident gamma E0 (Ee, x1), and location of
second event
J Gillam Monash
152Eu
Spectrum
• 0 degrees rotation
• 3cm crystal separation
344 (10644)
244
778 (3883)
962 (3430)
1408
(2467)
keV
Back Cone Projection
•
•
Detector to detector 3cm
Zero source rotation
•
•
60˚ source rotation
Iterative Reconstruction
•
•
Zero source rotation
•
•
60˚ source rotation
Compton Camera
• 152Eu point source imaging
• 30 keV gate on 778 keV
• 30mm detector separation
with 5mm position
resolution
• Single interactions in each
detector
Cone beam reconstruction
with 10 iterations.
~6mm image resolution x-y.
6cm source
to scatter
detector
separation
3cm detector
detector separation
Compton Camera
• 152Eu point source imaging
• 30 keV gate on 1408 keV
• 30mm detector separation
with 5mm position
resolution
• Single interactions in each
detector
Cone beam reconstruction
with 10 iterations.
~8mm image resolution x-y.
6cm source
to scatter
detector
separation
3cm detector
detector separation
New Sources for scanner characterisation
• Micro Deluxe Phantom filled with 370kBq of 22Na
• Main Applications:
– Small animal system evaluation (with field-of view greater than
45 mm)
– Spatial resolution measurements
– Evaluation of centre-of-rotation error
• Specifications:
– Rod diameters: 1.2, 1.6, 2.4, 3.2, 4.0 and 4.8 mm
– Height of rods: 3.4 cm
– Insert diameter: 4.4 cm
– Cylinder outside diameter: 5 cm
– Cylinder inside diameter: 4.5 cm
– Cylinder inside height: 3.7 cm
Conclusion
• Full characterisation of the first detector completed
• Number of Cs scanned finished for second detector
• Data collection in coincidence between the two
detectors for number of sources in number of
positions
• PSA, wavelet analysis and PET investigated and
presented in upcoming talks
• SmartPET system due to excellent energy
resolution Compton camera for SPECT investigated
• Initial images produced from PET and Compton
camera

SmartPET ½ Day Meeting

Transcription

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