computed radiography system simulation focusing on the ...€¦ · computed radiography system...
TRANSCRIPT
Computed Radiography System
Simulation Focusing on the Optical
Readout Process
Min YAO INSA de Lyon
Valérie KAFTANDJIAN INSA de Lyon
Philippe DUVAUCHELLE INSA de Lyon
Angéla PETERZOL-PARMENTIER AREVA
Andreas SCHUMM EDF
Peter WILLEMS GE
Juin 22, 2015
Digital Industrial Radiology and Computed Tomography (DIR 2015) 22-25 June 2015, Belgium, Ghent - www.ndt.net/app.DIR2015
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Outline
1. Computed radiography principle, advantages and
limitations
2. Optical readout simulation
Involved phenomena
Simulation method
– Laser spreading inside imaging plate (Monte Carlo tool)
– Laser scanning (Analytical model)
3. Illustration of different optical effects
4. Conclusion
3 / 18
What is Computed Radiography (CR)?
Imaging Plate Moved Translationally
Laser
ADCDigitizedSignal
2.Readout
3.Erasure
Intense Light
1.X-Ray Exposure
IPirradiation
Imaging Plate (IP)
Latent image
X-ray source
object
4 / 18
Advantages and limitations
• Advantages
+ Flexibility of detector
+ Direct digital image
+ Reusability
+ High dynamic range up to 105
• Limitations
- Poor efficiency at high energies
- Poor spatial resolution
due to the optical readout process
5 / 18
Objective
• CR imaging chain modeling
Exposure Readout
Source
object
detector
ScannerX-ray
Latent imageX-ray CR final imageLatent image
6 / 18
Optical readout simulation: involved phenomena
Imaging Plate Moved Translationally
Laser
ADC DigitizedSignal
Scan (Laser Beam) Direction
Sub-s
can (
Pla
te
Tra
nsla
tion)
Direction
* AAPM Task Group 10 (2006)
• Flying spot scanner
Latent image read by a scanning laser
7 / 18
Optical readout simulation: involved phenomena
• Static laser
Photo-stimulation by laser beam
Light emission: photo-stimulated luminescence (PSL)
Laser beam
Support
Protective layer
PSL
Phosphor layer
8 / 18
• Scanning laser
PSL emission
Latent image
modification
PSLLaser
t+Δt
PSLLaser
t+2Δt
PSLLaser
t+3Δt
Optical readout simulation: involved phenomena
9 / 18
• Analytical operator using a Monte Carlo optical response model
Optical readout simulation: method
H2
Latent image
Limg(x,y,z)
CR final imageDimg(x,y)
Optical response
model f(x,y,z)
Scanning
parameters
PSLLaser
PSLLaser
PSLLaser
),,(),( 2 parametersscanningfLimgHyxDimg nm
10 / 18
yx
scanlasernm
z
nm
dxdytPzyyxxfzyxLimgdzzP
parametersscanningfLimgHyxDimg
,
(mod)
2
),,(exp1),,()(
),,(),(
Optical readout simulation: method
latent image
modified by
scanning
optical cross
section of
photostimulation
optical response
(Monte Carlo)
PSL
detection
probability
Scanning
parameters
* Modified fromThoms (1996)
11 / 18Radius (m)
De
pth
(
m)
-200 -100 0 100 200
0
50
100
150
La
se
r d
istr
ibu
tio
n (
cm
-2)
2
4
6
8
10
x 106
Optical readout simulation: method
• Monte Carlo tool to obtain the optical response f(x,y,z)
IP is described by
Absorption coefficient
Scattering coefficient
Anisotropic factor :
– Forward peaked scattering
– Isotropic
– ...
Boundary conditions
• Output
light intensity function f(x,y,z)
Laser
f(x,y,z)
* Wang et al. (1995)
Fasbender et al. (2003)
12 / 18
100 200
Different optical effects illustration: absorption coefficient
• Great absorption coefficient: small scattering region
Bad efficiency, good resolution
100 times higher absorptionreference
-200 -100200
150
100
50
0
-200 -100200
150
100
50
0
Laser
-200 -100200
150
100
50
0
50
100
150
200
250
300
350
400
Intensity
IP d
epth
(µ
m)
Radius (µm)
I(x,y,z)
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100 200
-200 -100200
150
100
50
0
• Forward peaked scattering: great penetration depth
Good efficiency, good resolution
Different optical effects illustration: anisotropy factor
Forward peaked scattering
Laser
reference
-200 -100200
150
100
50
0
50
100
150
200
250
300
350
400
IP d
epth
(µ
m)
Radius (µm)
Intensity
-200 -100200
150
100
50
0
I(x,y,z)
14 / 18
Different optical effects illustration: laser intensity
• Great intensity: great penetration depth
Good efficiency, bad resolution
2 times more intensity
100 200
Laser
reference
-200 -100200
150
100
50
0
-200 -100200
150
100
50
0
50
100
150
200
250
300
350
400
IP d
epth
(µ
m)
Radius (µm)
-200 -100200
150
100
50
0 Intensity
I(x,y,z)
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Different optical effects illustration: IP thickness
• Small thickness: small scattering region
Bad efficiency, good resolution
Small thickness
100 200
Laser
reference
-200 -100200
150
100
50
0
-200 -100200
150
100
50
0
50
100
150
200
250
300
350
400
IP d
epth
(µ
m)
Radius (µm)
-200 -100200
150
100
50
0 Intensity
I(x,y,z)
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Different optical effects illustration: scanning effect
x (mm)
y (
mm
)
-1 -0.5 0 0.5 1
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1 15.2
15.4
15.6
15.8
16
16.2
16.4
16.6
16.8
17Readout factor1010
x (mm)
y (
mm
)
-1 -0.5 0 0.5 1
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1 660
670
680
690
700
710
720
730
Readoutfactor1016
x (mm)
y (
mm
)
-1 -0.5 0 0.5 1
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
13.8
3.85
3.9
3.95
4
4.05
4.1
4.15
4.2
4.25
x 104
Limg
x 104
Readout factor= Laser power × scanning time
Example of latent image (reference test object with various holes)
17 / 18
-10 -8 -6 -4 -2 0 2 4 6 8 100.92
0.93
0.94
0.95
0.96
0.97
0.98
0.99
1
y (mm)
No
rma
lize
d p
rofi
le
Latent image
1e10
1e16
-10 -8 -6 -4 -2 0 2 4 6 8 100.92
0.93
0.94
0.95
0.96
0.97
0.98
0.99
1
y (mm)
No
rma
lize
d p
rofi
le
Latent image
1e10
1e16
-10 -8 -6 -4 -2 0 2 4 6 8 100.92
0.93
0.94
0.95
0.96
0.97
0.98
0.99
1
y (mm)
No
rma
lize
d p
rofi
le
Latent image
1e10
1e16
• Influence of readout factor
Different optical effects illustration: scanning effect
18 / 18
Conclusion
• Simulation of optical readout process combining
analytical and MC tool
Interest of the tool
→ study of different optical effects
– absorption and scattering factors, IP thickness …
– scanning parameters
Modeling of the complete CR system is now available
→ in use at industrial site AREVA and EDF
To be done in the future : structural noise of IP
Thank you for your attention!