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AMIC : An Expandable Front-End for Gamma-ray Detectors with Light Distribution Analysis Capabilities. Vicente Herrero* , Christoph W. Lerche Michelle Spaggiari , Ramón Aliaga, Néstor Ferrando and Ricardo Colom. q. Continuous Scintillator Ray Detector. - PowerPoint PPT Presentation
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AMIC: AN EXPANDABLE FRONT-END AMIC: AN EXPANDABLE FRONT-END FOR GAMMA-RAY DETECTORS WITH FOR GAMMA-RAY DETECTORS WITH
LIGHT DISTRIBUTION ANALYSIS LIGHT DISTRIBUTION ANALYSIS CAPABILITIESCAPABILITIES
Vicente Herrero* , Christoph W. Lerche
Michelle Spaggiari, Ramón Aliaga,
Néstor Ferrando and Ricardo Colom.
17th REAL TIME CONFERENCE / IEEE - NPSS
ContinuousContinuous ScintillatorScintillator RayRay DetectorDetector
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q
Lower cost.
Higher detector sensibility. [1]
Better energy resolution. [2]
Light Distribution Analysis [3][4]
Geometry and Coating can be changed for optimization. [5]
[3] C. W. Lerche, et al. “Depth of gamma-ray interaction within continuous crystals from the width of its scintillation light-distribution” IEEE Trans. Nucl. Sci., (52), 560, 2005.
Designed for PET applicationsLSO : 42x42x10 mm
PMT : Hamamatsu H8500
[2] P. Bruyndonckx, et al. “Initial Characterization of a Nonpixelated Scintillator Detector in a PET Prototype Demonstrator”, IEEE Trans. Nucl. Sci., (53), 2543, 2006.
[1] P. Bruyndonckx, et al. “Performance Study of a PET Detector Module Based on a Continuous Scintillator”, IEEE Trans. Nucl. Sci., (53), 2536, 2006.
[5] C. W. Lerche, et al. “Dependency of Energy, Position and Depth of Interaction on Scintillation Crystal Coating and Geometry", IEEE Trans. Nucl. Sci., 55, (2008) 1344.
[4] C. W. Lerche, et al. “Fast circuit topology for spatial signal distribution analysis and its application to nuclear medicine imaging” IEEE NPSS RT 2010,
17th REAL TIME CONFERENCE / IEEE - NPSS
PESICPrevious WorkPrevious Work
21/04/23 3
◦ Individual Anode Gain Adjustment for Detector Equalization [7]
◦ Reduces error due to signal delay in resistor network [6]
◦ Not an expandable architecture
◦ Low resolution in Depth of Interaction (DOI) measurements [7]
[7] V. Herrero, et al. “Position sensitive scintillator based detector improvements by means of an integrated frontend”, NIMA., (604), 77, 2009.
[6] V. Herrero, et al. “PESIC: an integrated front-end for PET applications”, IEEE TNS., (55), 27, 2008.
17th REAL TIME CONFERENCE / IEEE - NPSS
Mathematical Foundations of Mathematical Foundations of AMICAMIC
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Moment n of distribution f(x)
ENERGY
CENTROID (x AXIS)VARIANCE (width of distribution)
xxfxm xx )(1
xxfm xx )()1(0
xxfxm xx )(22
xxfxm xx )(33SKEWNESS (assymetry of distribution)
… …
DISCRETIZED
BASICOPERATION
fx(0)
fx(1)
fx(2)
fx(3)
Kn(x)
Kn(0)
Kn(1)
Kn(2)
Kn(3)
+nxm
[4] C. W. Lerche, et al. “Fast circuit topology for spatial signal distribution analysis and its application to nuclear medicine imaging” IEEE NPSS RT 2010,
17th REAL TIME CONFERENCE / IEEE - NPSS
AMIC ArchitectureAMIC Architecture
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64 input buffers
8 Computational Blocks
8 Output Amplifiers (current & voltage)
64 light distribution samples
I2C interface (coef.
program.)
17th REAL TIME CONFERENCE / IEEE - NPSS
Preamplifiers and Output Preamplifiers and Output StageStage
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Both SiPM and PMT capable
Optimized PMT Bandwidth > 34 MHz Noise 0.1 uArms
Mismatch in current mirror between different preamps
Solved by calibration of coeff. values
40ux100u
175u x135u
Current Output Voltage Output using
an R amplifier Bandwidth > 20 MHz SlewRate = 350 V/us
(CL= 50pF)
THD < 0.35 % (0.5mApp)
17th REAL TIME CONFERENCE / IEEE - NPSS
Computational BlockComputational Block
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1540u x120u
Analog Current Mode Filter
40u x50u
Coefficient values < 1 with 8 bits precision offers 256 different values for coefficients. A linear distribution (M1) of 28 values on one
axis means 256x256 inputs 64*8=512 Coefficient units !! Area needs
to be restricted
[5] K. Bult and G. Geelen “An inherently linear and compact most-only current division technique", 39th IEEE-ISSCC 189 (1992).
Extremely sensitive to Vout = Vdump◦ Small differences introduce big linearity errors
Area ratio optimized for a maximum input current of 6mA (BW > 60 MHz)
Needs biasing to get a better linearity
Vout=Vdump
Coefficient Unit
17th REAL TIME CONFERENCE / IEEE - NPSS
Computational BlockComputational Block
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Necessary to stabilize DUMP & OUT voltages to the same value
High bandwidth (>200 MHz), PM (>80º) and Low THD (<0.05 %)
Matched layout needed for DUMP & OUT current paths◦ Differences in parasitic resistance introduce voltage
variations in DUMP & OUT voltages close to coeff.
◦ 1 collector handles 16 coeff.
Fully Differential Current Collector
200u x50u
17th REAL TIME CONFERENCE / IEEE - NPSS
Architecture Expansion using Architecture Expansion using AMICAMIC
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AMIC is the basic building block
Each AMIC generates up to 8 «partial moments»
1 AMIC is enough to implement the final addition of all «partial moments» (up to 64 «partial moments» of 64 inputs which means 4096 inputs !!)
Anyway if you need more… just add more AMICs at the output◦ Only noise generated in the front-end
limits the number of inputs
AMIC 1
AMIC II
AMIC III
AMIC IV
AMIC V
8x
8x
8x
8x
8x
17th REAL TIME CONFERENCE / IEEE - NPSS
Performance Test Performance Test MeasurementsMeasurements
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0 50 100 150 200 2500
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Coefficient Code
Nor
mal
ized
Val
ue
y(x) = a (x - b)a = 0.0039294b = 3.0374R = 0.99991 (lin)
Linearity of Coefficient Values
Most codes lie inside the limits but… 7 effective bits
Area constrains in Coeff. Unit introduce mismatch
Bandwidth 16 MHz
Linearity vs. Input Current
(Coeff. Value =128)
± 0.65 %
Input Dynamic Range
(within Linearity limits)
1.65 mA
THD 0.5 mA / 100kHz
0.5%
Noise (current output)
1.8 µArms
Switch matrix made with 8 ADG2128 (Analog Devices)
17th REAL TIME CONFERENCE / IEEE - NPSS
Experimental Setup Test Experimental Setup Test MeasurementsMeasurements
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5x5 Sweep on detector surface
(6 mm steps)
17th REAL TIME CONFERENCE / IEEE - NPSS
Experimental Setup Test Experimental Setup Test MeasurementsMeasurements
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AMIC calibrated for preamp mismatch compensation
Collimation Spot = 1 mm M1x & M1y OUTPUTs (same
results)
No improvements made by adding information of other moments
As usual border effect increases resolution far from center
Just testing everything works
M1x calibrated coefficients
17th REAL TIME CONFERENCE / IEEE - NPSS
Experimental Setup Test Experimental Setup Test MeasurementsMeasurements
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AMIC calibrated for preamp mismatch compensation
«Non invasive» method DOI can improve 2D position
resolution and also reduce parallax error after reconstruction stage
Improvement of 300% over previous results with PESIC
M2 calibrated coefficients
of light
distribution Depth of Interaction
[3] C. W. Lerche, et al. “Depth of gamma-ray interaction within continuous crystals from the width of its scintillation light-distribution” IEEE Trans. Nucl. Sci., (52), 560, 2005.
[3]
+++
[7] V. Herrero, et al. “Position sensitive scintillator based detector improvements by means of an integrated frontend”, NIMA., (604), 77, 2009.
17th REAL TIME CONFERENCE / IEEE - NPSS
The higher the number of inputs the better the spatial resolution… but also:
2D position calculation can be improved by using other moments information
DOI calculation can also be improved the same way
NOW WORKING WITH NEURAL NETWORKS to optimize full reconstruction of detected events
This is just the beginning…This is just the beginning…
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17th REAL TIME CONFERENCE / IEEE - NPSS
A lot of information waiting A lot of information waiting there to be used …there to be used …
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Check out Christoph W. Lerche’s work at the poster session !!!!
[4] C. W. Lerche, et al. “Fast circuit topology for spatial signal distribution analysis and its application to nuclear medicine imaging” IEEE NPSS RT 2010,
17th REAL TIME CONFERENCE / IEEE - NPSS
We also work on:
◦Increasing Timing resolution in Coincidence Detection J. M. Monzó
◦High Performance Data Acquisition Systems R. Aliaga
Other work being carried Other work being carried out…out…
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17th REAL TIME CONFERENCE / IEEE - NPSS
THANK YOU FOR THANK YOU FOR YOUR ATTENTIONYOUR ATTENTION
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