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Vicente Herrero* , Christoph W. Lerche Michelle Spaggiari , Ramón Aliaga,

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.

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Vicente Herrero* , Christoph W. Lerche Michelle Spaggiari , Ramón Aliaga,

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  1. 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 andRicardo Colom.

  2. q ContinuousScintillator RayDetector • Designedfor PET applications LSO : 42x42x10 mm PMT : Hamamatsu H8500 • Lowercost. • Higher detector sensibility. [1] • Betterenergyresolution. [2] • Light DistributionAnalysis[3][4] • Geometry and Coating can be changed for optimization. [5] [1] P. Bruyndonckx, et al. “Performance Study of a PET Detector Module Based on a Continuous Scintillator”, IEEE Trans. Nucl. Sci., (53), 2536, 2006. [2] P. Bruyndonckx, et al. “Initial Characterization of a Nonpixelated Scintillator Detector in a PET Prototype Demonstrator”, IEEE Trans. Nucl. Sci., (53), 2543, 2006. [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. [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, [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.

  3. PreviousWork PESIC • 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] [6] V. Herrero, et al. “PESIC: an integrated front-end for PET applications”, IEEE TNS., (55), 27, 2008. [7] V. Herrero, et al. “Position sensitive scintillator based detector improvements by means of an integrated frontend”, NIMA., (604), 77, 2009.

  4. MathematicalFoundations of AMIC Moment n of distribution f(x) ENERGY CENTROID (x AXIS) VARIANCE (width of distribution) SKEWNESS (assymetry of distribution) Kn(x) … … Kn(0) DISCRETIZED BASIC OPERATION Kn(1) [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, + Kn(2) Kn(3)

  5. AMIC Architecture 64 light distribution samples I2C interface (coef. program.) 64 input buffers 8 Computational Blocks 8 Output Amplifiers (current & voltage)

  6. Preamplifiers and Output Stage • BothSiPM and PMT capable • Optimized PMT • Bandwidth > 34 MHz • Noise 0.1 uArms • Current Output • Voltage Output usingan R amplifier • Bandwidth > 20 MHz • SlewRate = 350 V/us(CL= 50pF) • THD < 0.35 % (0.5mApp) 40ux100u Solved by calibration of coeff. values • Mismatch in currentmirrorbetweendifferentpreamps 175u x135u

  7. Computational Block Analog Current Mode Filter 1540u x120u Coefficient Unit • Coefficientvalues < 1 with8 bits precision • offers 256 differentvaluesforcoefficients. • A linear distribution (M1) of 28valuesonone axis means 256x256 inputs • 64*8=512 Coefficientunits !!  Areaneedsto be restricted • ExtremelysensitivetoVout = Vdump • Small differences introduce biglinearityerrors • Area ratio optimizedfor a maximum input current of 6mA (BW > 60 MHz) • Needsbiasingtoget a betterlinearity Vout=Vdump [5] K. Bult and G. Geelen“An inherently linear and compact most-only current division technique", 39th IEEE-ISSCC 189 (1992). 40u x50u

  8. Computational Block 200u x50u Fully Differential Current Collector • Necessarytostabilize DUMP & OUT voltagestothesamevalue • High bandwidth (>200 MHz), PM (>80º) and Low THD (<0.05 %) • Matchedlayoutneededfor DUMP & OUT currentpaths • Differences in parasiticresistance introduce voltagevariations in DUMP & OUT voltagesclosetocoeff. • 1 collectorhandles 16 coeff.

  9. ArchitectureExpansionusing AMIC 8x AMIC 1 • AMIC isthebasicbuilding block • Each AMIC generates up to 8 «partialmoments» • 1 AMIC isenoughtoimplementthe final addition of all «partialmoments» (up to 64 «partialmoments» of 64 inputs whichmeans 4096 inputs !!) • Anywayifyouneed more… justadd more AMICs at the output • Onlynoisegenerated in thefront-endlimitsthenumber of inputs AMIC II 8x 8x AMIC V 8x AMIC III AMIC IV 8x

  10. Performance Test Measurements Linearity of Coefficient Values Mostcodes lie insidethelimitsbut… 7 effective bits Areaconstrains in Coeff. Unit introduce mismatch Switch matrix made with 8 ADG2128 (Analog Devices)

  11. Experimental Setup Test Measurements 5x5 Sweep on detector surface (6 mm steps)

  12. Experimental Setup Test Measurements • AMIC calibratedforpreampmismatchcompensation • Collimation Spot = 1 mm • M1x & M1yOUTPUTs (sameresults) • No improvementsmadebyaddinginformation of othermoments • As usual bordereffectincreasesresolutionfarfrom center • Justtestingeverythingworks M1x calibrated coefficients

  13. Experimental Setup Test Measurements • AMIC calibratedforpreampmismatchcompensation • «Non invasive» method • DOI can improve 2D position resolution and also reduce parallax error afterreconstructionstage • Improvement of 300% overpreviousresultswith PESIC [7] V. Herrero, et al. “Position sensitive scintillator based detector improvements by means of an integrated frontend”, NIMA., (604), 77, 2009. M2 calibrated coefficients +++ of light distribution Depth of Interaction [3] [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.

  14. Thisisjustthebeginning… • Thehigherthenumber of inputs thebetterthespatialresolution… butalso: • 2D position calculation can be improvedbyusingothermomentsinformation • DOI calculation can also be improvedthesameway • NOW WORKING WITH Neural Networkstooptimize full reconstruction of detectedevents

  15. A lot of informationwaitingthereto be used … [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, Check out Christoph W. Lerche’s work at the poster session !!!!

  16. Otherworkbeingcarriedout… • We also work on: • Increasing Timing resolution in Coincidence Detection • J. M. Monzó • High Performance Data Acquisition Systems • R. Aliaga

  17. THANK YOU FOR YOUR ATTENTION

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