pet thin line
DESCRIPTION
w. w. d. w. > LTRANSCRIPT
PETThin Line
CollimatorThin Cone
PinholeThin Cone
CodedApertureThin Cones
ComptonCone Surface
Resolution (R)=2
wL
d+L2
⎛ ⎝ ⎜ ⎞
⎠ ⎟
€
Efficiency ∝w
L
⎛
⎝ ⎜
⎞
⎠ ⎟2
Resolution=w Resolution=w
Efficiency∝ n
wd
⎛
⎝ ⎜
⎞
⎠ ⎟ 2
Efficiency∝wd
⎛
⎝ ⎜
⎞
⎠ ⎟ 2
better res. small FOVlower eff.
w
ww
- results similar to pinhole- higher efficiency
> L <
d
changing L,defficiency vs sp.res.
0 – 20 mm1 – 0.009 %
New Detector (Pin hole 0.7 mm tungsten, H8500 64 ch)
(1.8 x 1.8 mm2) (1.0 x 1.0 mm2)
Good pixel identification For 1.8 x 1.8 not so good for 1.0 x 1.0-> better anode sampling is needed --> H8500 256 channels
QuickTime™ and aTIFF (PackBits) decompressorare needed to see this picture.
QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.
Flood Field irradiation
E = 122 keV
0
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45
50
0 100 200 300 400 500 600
Read-out electronics
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now the chip VA-HDR11 is used
Reconstruction of a 122 keV point-like source using the coded apertures
FWHM=0.93 mm
Sensitivity=145 cps /MBq
5 cps/MBq with pinhole
Submillimeter spatial
resolution
High sensitivity
(factor ~ 30)
cm
cm
0.5 0.9 1.4 1.8
0.2
0.5
0.7
0.9
1.1
1.4
1.6
1.8
NTHT MURA 22x22
10 20 30 40
5
10
15
20
25
30
35
40
cm
cm
0.5 0.9 1.4 1.8
0.2
0.5
0.7
0.9
1.1
1.4
1.6
1.8
10Ci in 10 s
4444 pixels
1.25 x 1.25 mm2
FoV 22 cm2.
Mask NTHT MURA 2222, =2, 1% transparent, thickness 1.5 mm W. Pitch 0.68 mm.
Line source10Ci in 10 s
cm
cm
0.5 0.9 1.4 1.8
0.2
0.5
0.7
0.9
1.1
1.4
1.6
1.8
2D source10Ci in 10 s
simulation for our desktop detector
sensitivity improved by a factor 30!
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coded aperture
collimators
High resolution preserving high SNR ?
Ideal pinhole +perfect resolution -zero transmitted power
Total source counts: 350k
Ideal Pinhole
Real pinhole +some signal through -degraded resolution
Total source counts: 35M
Real Pinhole
Total source counts: 35M
Coded Aperture
Coded Aperture +signal of finite pinhole +resolution of ideal pinhole
coded apertures
0
50
100
150
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400
450
50 70 90 110 130 150 170 190
image pixel
counts
0
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150 170 190 210 230 250 270 290 310 330 350image pixel
counts
Peak
Valley
catene resistive vs multiwire
Read-out electronics
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Coded apertures
I (Image) = O (object) x A (aperture)
There are decoding patterns G allowing:
A G = then A G = Ô, in fact
Ô = R G = ( O × A ) G = O * (A G) = O * PSF
MURA 79 x 79
20 40 60
20
40
60
Product array 77 x 77
20 40 60
20
40
60
No Two Holes Touching MURA 62 x 62
20 40 60
10
20
30
40
50
60
m sequence 63 x 65
20 40 60
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Example of apertures with known decoding pattern
Figure adapted from:Fenimore and Cannon, Optical Engineering, 19, 3, 283-289, 1980.