Spectral x-ray photon counting

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  • Light and its nature have caused a lot of ink to flow during these last decades. Its dual behavior is partly explained by (1)Double-slit experiment of Thomas Young - who represents the photon’s motion as a wave - and also by (2)the Photoelectric effect in which the photon is considered as a particle. A Revolution: SALEH THEORY solves this ambiguity and this difficulty presenting a three-dimensional trajectory for the photon's motion and a new formula to calculate its energy. More information on https://youtu.be/mLtpARXuMbM
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Spectral x-ray photon counting

  1. 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 2011dirk.meier@gm-ideas.com 2011-April, CERN, SpecX-Ray Workshop 1
  2. 2. ASIC Designs Overview dirk.meier@gm-ideas.com 2011-April, CERN, SpecX-Ray Workshop 2
  3. 3. Radiation Detector Design and Development for ScienceScience: e.g. space, physics Requirements, PreliminaryJAXA, BepiColombo Specifications ASIC wafer Design Simulation Implementation, Rule checks, simulationATHENA Manufacture, Foundry Radiation sensor Assembly Integration Tests, Verification and Validation dirk.meier@gm-ideas.com 2011-April, CERN, SpecX-Ray Workshop 3
  4. 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. dirk.meier@gm-ideas.com 2011-April, CERN, SpecX-Ray Workshop 4
  5. 5. Spectral X-ray Photon Counting - Principle dirk.meier@gm-ideas.com 2011-April, CERN, SpecX-Ray Workshop 5
  6. 6. Spectral X-ray Photon Counting - Principle dirk.meier@gm-ideas.com 2011-April, CERN, SpecX-Ray Workshop 6
  7. 7. ASIC Channel Architecture – 1 out of 32/64Mikkelsen et al. (2008), Proc. IEEENSS dirk.meier@gm-ideas.com 2011-April, CERN, SpecX-Ray Workshop 7
  8. 8. ASIC Specifications dirk.meier@gm-ideas.com 2011-April, CERN, SpecX-Ray Workshop 8
  9. 9. ASIC Floorplan, Padframe, Block Diagram dirk.meier@gm-ideas.com 2011-April, CERN, SpecX-Ray Workshop 9
  10. 10. ASIC Block Diagram dirk.meier@gm-ideas.com 2011-April, CERN, SpecX-Ray Workshop 10
  11. 11. 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 dirk.meier@gm-ideas.com 2011-April, CERN, SpecX-Ray Workshop 11
  12. 12. Spectral X-ray Counting DetectorX-ray Line CameraModules: CdTe + ASICsWang et al. (2009), Proc. IEEE NSS dirk.meier@gm-ideas.com 2011-April, CERN, SpecX-Ray Workshop 12
  13. 13. Radiation Sensor - CdTe Crystal with Electrodes -500V 3 mm 0.4 mm Anode Pitch dirk.meier@gm-ideas.com 2011-April, CERN, SpecX-Ray Workshop 13
  14. 14. Spectral X-ray Counting Detector - Specifications dirk.meier@gm-ideas.com 2011-April, CERN, SpecX-Ray Workshop 14
  15. 15. Photographs of X-ray Line Detector dirk.meier@gm-ideas.com 2011-April, CERN, SpecX-Ray Workshop 15
  16. 16. Photographs of X-ray Line Detector dirk.meier@gm-ideas.com 2011-April, CERN, SpecX-Ray Workshop 16
  17. 17. 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 dirk.meier@gm-ideas.com 2011-April, CERN, SpecX-Ray Workshop 17
  18. 18. Example Material Identification – Luggage PhantomGrey scale image based on Color coded based on the ratio ofattenuation at one energy attenuation at two energies, [80,100] keV and [35,50] keV dirk.meier@gm-ideas.com 2011-April, CERN, SpecX-Ray Workshop 18
  19. 19. Food Safety - Pieces of Glass in Raisins Grey scale image based on Dual-energy attenuation at one energy information, enhanced to ’see’ only glass and eliminate raisins dirk.meier@gm-ideas.com 2011-April, CERN, SpecX-Ray Workshop 19
  20. 20. Material Separation – Hard Disk Drive Grey scale image based on Regions color coded based on attenuation at one energy attenuation ratio between high and low energy dirk.meier@gm-ideas.com 2011-April, CERN, SpecX-Ray Workshop 20
  21. 21. Count Rate and Spectra Mono-energetic x-rays Customer data dirk.meier@gm-ideas.com 2011-April, CERN, SpecX-Ray Workshop 21
  22. 22. 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 dirk.meier@gm-ideas.com 2011-April, CERN, SpecX-Ray Workshop 22
  23. 23. Charge Sharing Customer data 80 keV Summed Count rate Summed energy dirk.meier@gm-ideas.com 2011-April, CERN, SpecX-Ray Workshop 23
  24. 24. Spectra with Gd Contrast Agent2.8 Water PMMA POM2.4 PTFE Cortical bone Iodine solution 2 Gd solution1.61.20.80.4 Wang, 2011 30 40 50 60 70 80 90 100 Energy (keV) Energy-dependent x-ray attenuation dirk.meier@gm-ideas.com 2011-April, CERN, SpecX-Ray Workshop 24
  25. 25. CT Phantom Images and Energy Thresholds Trimming dirk.meier@gm-ideas.com 2011-April, CERN, SpecX-Ray Workshop 25
  26. 26. Summary We have built a X-ray Line Camera capable of Spectral X-ray Photon Counting. 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 dirk.meier@gm-ideas.com 2011-April, CERN, SpecX-Ray Workshop 26
  27. 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 PhotonCounting 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. dirk.meier@gm-ideas.com 2011-April, CERN, SpecX-Ray Workshop 27
  28. 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 dirk.meier@gm-ideas.com 2011-April, CERN, SpecX-Ray Workshop 28

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