spectral x-ray photon counting
DESCRIPTION
TRANSCRIPT
[email protected] 2011-April, CERN, SpecX-Ray Workshop 1
ASIC Development for Energy Resolved Spectral Counting and Imaging of X-rays
S. Azman, W. Dang, C. Gheorghe, M. Gjetanger, T.M. Johansen,D. Meier, S. Mikkelsen, G. Mæhlum, J. Talebi, T. Ødegaard
Gamma Medica – Ideas (Norway) AS
CERN, 4.-6. April 2011
[email protected] 2011-April, CERN, SpecX-Ray Workshop 3
Radiation Detector Design and Development for Science
JAXA, BepiColombo
ATHENA
Requirements, Preliminary
Specifications
Design Simulation
Implementation,Rule checks, simulation
Manufacture, Foundry
Assembly
Integration
Tests,Verification and
Validation
Science: e.g. space, physics
ASIC wafer
Radiation sensor
[email protected] 2011-April, CERN, SpecX-Ray Workshop 4
Abstract – ASIC for Spectral X-ray Photon Counting
We describe an integrated circuit (IC) for spectral counting and imaging of polychromatic x-rays.
The circuit has been designed for the readout of cadmium telluride (CdTe) radiation sensors with up to 64 pixel electrodes. Each readout channel contains a charge sensitive amplifier, up to 6 discriminators and 6 counters which increment when the amplitude exceeds a given threshold. The energy dynamic range is about 120 keV. Subsequently we designed and assembled camera prototypes from 1D-linear arrays of CdTe read out by 32 ASICs. We have tested the cameras with imaging phantoms and polychromatic x-rays in a micro-computed tomography (microCT) setup. We studied the use of the cameras for material separation, especially with gadolinium and iodine based contrast agents, for medical imaging. The presentation will focus on the ASIC design specifications which were originally set for industrial scanning, but also discuss the requirements for x-ray microCT and medical imaging.
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ASIC Channel Architecture – 1 out of 32/64
Mikkelsen et al. (2008), Proc. IEEE NSS
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Spectral X-ray Photon Counting – Applications
Security e.g. explosives
Food safety e.g. foreign objects
Separtion & sorting e.g. metals, waste....
NDT Medical
e.g. contrast agents Physics research
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Spectral X-ray Counting Detector
X-ray Line Camera
Modules: CdTe + ASICs
Wang et al. (2009), Proc. IEEE NSS
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Radiation Sensor - CdTe Crystal with Electrodes
0.4 mm Anode Pitch
3 mm
-500V
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Spectral X-ray Counting Detector - Specifications
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X-Ray Line Camera - Hardware Details
External COUNT signal synchronized with conveyor belt or CT system
1500 frames/seconds maximum (0.67 ms frames)
Short dead time between frames (40us)
Interface to PC through National Instruments I/O card
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Example Material Identification – Luggage Phantom
Color coded based on the ratio of attenuation at two energies, [80,100] keV and [35,50] keV
Grey scale image based on attenuation at one energy
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Food Safety - Pieces of Glass in Raisins
Dual-energy information, enhanced to ’see’ only glass and eliminate raisins
Grey scale image based on attenuation at one energy
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Material Separation – Hard Disk Drive
Regions color coded based on attenuation ratio between high and low energy
Grey scale image based on attenuation at one energy
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Count Rate and Spectra
Customer data
Mono-energetic x-rays
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Spectral Distortion in Photon Counting Detector
Comparison between• GM-I Spectral Photon
Counting Detector• AMTEK CdTe
Spectrometer
Effects:• Energy resolution• Pulse pileup• Characteristic x-ray• Charge sharing
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Charge Sharing
80 keVSummed Count rate Summed energy
Customer data
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Spectra with Gd Contrast Agent
0.4
0.8
1.2
1.6
2
2.4
2.8
30 40 50 60 70 80 90 100
WaterPMMAPOMPTFECortical boneIodine solutionGd solution
Energy (keV)
Energy-dependent x-ray attenuation
Wang, 2011
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CT Phantom Images and Energy Thresholds Trimming
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Summary
We have built a X-ray Line Camera capable of Spectral X-ray PhotonCounting. The design is based on CdTe custom made ASICs.
The prototype cameras allow one to study the potentials of spectral x-ray photon counting.
It is important to understand and improve:
• Spectral response vs. count rate– Charge sharing in CdTe– Rate capability of CdTe pixels and ASIC, especially for CT
• Threshold uniformity and trimming
[email protected] 2011-April, CERN, SpecX-Ray Workshop 27
References
[1] S. Mikkelsen et al. (2008), ”An ASIC for Multi-Energy X-ray Counting”, Proc. IEEE NSS 2008.
[2] X. Wang et al. (2009), ”A Digital Line-Camera for Energy Resolved X-ray Photon Counting”, Proc. IEEE MIC 2009.
[3] X. Wang et al. (2011), “Material Separation in X-ray CT with Energy Resolved Photon Counting Detectors", Medical Physics (0094-2405), 3/1/2011. Vol.38,Iss.3;p.1534-1546.
[4] X.Wang et al. (2011), “MicroCT with energy-resolved photon-counting detectors2011“, Phys. Med. Biol. 56 2791–2816.
[email protected] 2011-April, CERN, SpecX-Ray Workshop 28
Acknowledgments
We like to thank our customers and collaborators.
and
X. Wang, E. Frey, K. Taguchi, B.M.W. Tsui at Johns Hopkins University
D. Wagenaar at Gamma Medica, Northridge
B. Sundal at Corentium, Norway
Thank you