1 / 29

A Compact 16-Module Camera Using 64-Pixel CsI(Tl)/Si PIN Photodiode Imaging Module

A Compact 16-Module Camera Using 64-Pixel CsI(Tl)/Si PIN Photodiode Imaging Module. W.-S. Choong 1 , G.J. Gruber 1 , W.W. Moses 1 , S.E. Derenzo 1 , S.E. Holland 1 , M. Pedrali-Noy 1 , B. Krieger 1 , E. Mandelli 1 , G. Meddeler 1 , N.W. Wang 1 , C.S. Tindall 1 , and E.K. Witt 2.

lew
Download Presentation

A Compact 16-Module Camera Using 64-Pixel CsI(Tl)/Si PIN Photodiode Imaging Module

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. A Compact 16-Module Camera Using 64-Pixel CsI(Tl)/Si PIN Photodiode Imaging Module W.-S. Choong1, G.J. Gruber1, W.W. Moses1, S.E. Derenzo1, S.E. Holland1, M. Pedrali-Noy1, B. Krieger1, E. Mandelli1, G. Meddeler1, N.W. Wang1, C.S. Tindall1, and E.K. Witt2 1Lawrence Berkeley National Laboratory, Berkeley, CA 94720 2Capintec, Inc, Ramsey, NJ 07446

  2. Bulky Long imaging distance Intrinsic resolution ~ 3.5 mm Significant dead area around the periphery DE/E ~ 9% FWHM Compact Short imaging distance Intrinsic resolution ~ 2 - 3 mm Small dead area around the periphery DE/E < 15% FWHM Motivation Anger Camera Compact Camera

  3. Approaches to Compact Cameras • Discrete scintillator/photodiode camera: gamma rays interact in an array of optically-isolated scintillation crystals that are coupled 1-to-1 to a photodiode array • Solid-state camera: gamma rays interact directly with a pixellated solid-state detector (e.g. CdZnTe) • Position-sensitive photomultiplier tube camera: gamma rays interact in one or more scintillation crystals which are then read out by PSPMT.

  4. LBNL Low-Noise Photodiode Arrays • Low leakage current (<50 pA/pixel @ 50 V) • 3 pF/pixel capacitance • 80% quantum efficiency for 540 nm light • 98.5% good pixel yield during fabrication 64 3x3 mm2 pixels (edge and corner pixels are 30% and 50% smaller area respectively)

  5. Photodiode Fabrication • Made on 300 m thick, high resistivity (>10 k-cm), n-type silicon • Low leakage current is achieved by depositing a thick layer of phosphorus-doped polysilicon to getter impurity atoms • p+ junctions are fabricated by ion-implanting boron • n+ back-side contact is made by re-depositing a thin layer of polysilicon after etching off the thick polysilicon gettering layer • A layer of indium tin oxide (ITO) is deposited on the back-side to serve as an anti-reflective (AR) coating optimized for 540 nm light (the peak output of CsI(Tl) scintillator crystal) Reference: S.E. Holland, N.W. Wang, and W.W. Moses, “Development of low noise, back-side illuminated silicon photodiode arrays,” IEEE Transactions on Nuclear Science, vol. 41, pp. 443-447, 1997

  6. PETRIC Readout IC • Input: 64 photodiode signals plus control signals that modify ASIC behavior • Front end: 64 channels of low-noise charge-sensitive preamplifiers and adjustable shaper amplifiers • “Winner Take All” (WTA): reduces the 64 amplified, shaped signals to a single “winner” channel (the one with the greatest amplitude) • Output: the 1 analog “winner” plus 6 digital bits identifying the winning pixel Reference: M. Pedrali-Noy, G.J. Gruber, B. Krieger, E. Mandelli, G. Meddeler, W.W. Moses, et al., “PETRIC-A Positron Emission Tomograph Readout Integrated Circuit,” IEEE Transactions on Nuclear Science, vol. 48, pp. 479-484, 2001

  7. Components of Module Surface mount connectors Low-noise Si PIN photodiode array EMF shield for PETRIC PETRIC CsI(Tl) array Ceramic PCB Surface mount capacitors Getek PCB

  8. Complete 64-Pixel Module • PETRIC readout: 64 front end channels followed by “Winner Take All” circuitry that selects the channel with the greatest amplitude • Custom printed circuit boards: provide electrical connections to the photodiodes and the PETRIC • Custom Si PIN photodiodes: very low leakage current (<50 pA/pixel) => low electronic noise • CsI(Tl) crystals: commercial 3 x 3 x 5 mm3 crystal array Capacitors EMF shield Connectors 14 mm 24 mm 24 mm

  9. 16-Module Camera Design • A scintimammography imaging camera constructed from tiling 16 individual 64-pixel modules • Separate WTA multiplexes signals from up to 16 modules WTA, peak detect, interface I/O

  10. Motherboard: Block Diagram

  11. PETRIC I/O Signals

  12. Motherboard: Timing Diagram

  13. Photograph of the 16-Module Camera Comparator Readout timing circuitry Peak detector WTA-3 Four 64-pixel module Cable to NI-DAQ card Photodiode bias voltage

  14. Pulse Height Spectrum (Tc99m) The numbers in parenthesis are the corresponding fwhm energy resolution.

  15. Energy Resolution Inner Pixels Edge Pixels

  16. Energy Resolution(From a High SNR Module) Inner Pixels Edge Pixels

  17. Energy Resolution(From a Low SNR Module) Inner Pixels Edge Pixels

  18. System Spatial Resolution(with Line Source) In Air 10 cm Acrylic Block All-Purpose Collimator 8000 cps/mCi, 23.5 mm thick High-Sensitivity Collimator 16,200 cps/mCi, 23.5 mm thick Collimator

  19. System Spatial Resolution

  20. Noise Sources (7% - 10% fwhm) (2% - 3% fwhm) (8% - 10% fwhm)

  21. Electronic Noise (w/o PD) Module #1 Module #2

  22. Electronic Noise (w/ PD) Module #1 Module #2

  23. Light Collection Inhomogeneity(Measured w/ PMT, Excited by 511 keV) Center = 147 Center = 137 Center = 123 Center = 157 Note:All crystals have similar performance if re-wrapped with Teflon tape.

  24. Future Directions • Working with Capintec, Inc under a CRADA (Cooperative Research and Development Agreement) project to build a 25-module and 100-module gamma camera using smaller pixel (2.4 mm x 2.4 mm) photodiode arrays. • Design and fabricate a new WTA I.C. with 32 input channels and a peak detect to be used in the gamma camera.

  25. Canberra Photodiode Arrays LBNL Photodiode Canberra Photodiode 64 2.4x2.4 mm2 pixels (edge and corner pixels are 32% and 54% smaller respectively) 19.6 mm 19.6 mm

  26. Canberra Photodiode Arrays: Performance

  27. 32-Channel WTA IC with Peak Detect

  28. Conclusions • Have implemented a compact 16-module gamma camera • Have demonstrated the working of the 16-module gamma camera (at least with 4 modules) with good SNR (12.4% and 14.4% on the inner and edge pixel respectively for 140 keV emissions of Tc99m) • Have measured system spatial resolution with an all-purpose and high-sensitivity collimator • This technology is promising and may soon be available for breast cancer and axillary lymph nodes imaging • Working with Capintec, Inc to build a 25-module and 100-module gamma camera using 2.4 mm x 2.4 mm pixel photodiode array

  29. Funding • U.S. Department of Army • U.S. Department of Energy • National Institute of Health • Capintec, Inc

More Related