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The SmartPET Project

The SmartPET Project. Andy Boston ajboston@liv.ac.uk. What is the SmartPET project? Detector performance Pulse Shape Analysis Electric Field Simulation First PET images from the scanner Future work plans. SmartPET project : Outline of Talk. Imaging with Semiconductor Detectors.

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The SmartPET Project

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  1. The SmartPET Project SmartPET - status report AGATA week Andy Boston ajboston@liv.ac.uk

  2. What is the SmartPET project? Detector performance Pulse Shape Analysis Electric Field Simulation First PET images from the scanner Future work plans SmartPET project : Outline of Talk SmartPET - status report AGATA week

  3. Imaging with Semiconductor Detectors SmartPET - status report AGATA week

  4. Detector Specification Depletion at -1300V, Operation at -1800V 12 x12 Segmentation, 5mm strip pitch 1mm thick Aluminium entrance window The SmartPET DSGSD detectors SmartPET - status report AGATA week • Warm FET configuration, 300mV/MeV pre-amps • Average energy resolution ~ 1.5keV FWHM @ 122keV

  5. 59.5 17.8 26.3 20.8 59.5 26.3 Number of Counts Energy (keV) Contact profile and performance Contacts • AC • 0.3microns • Strip gap 180microns • DC • 50microns • Strip gap 300microns Energy resolution @ 60 keV • AC06 • FWHM = 1.45 keV • DCO6 • FWHM = 1.12 keV SmartPET - status report AGATA week

  6. Detector energy resolutions at 122 keV SmartPET - status report AGATA week

  7. 1mm Tungsten collimation (9cm) 1mm step positions Sources 1GBq 241Am annular source – 40cps 1.8GBq 57Co source (pellet) – 150cps 70.21MBq 137Cs – 35cps Scans 241Am 120 seconds at each position (AC and DC) 57Co 60 seconds (AC and DC) 120 seconds (side) 137Cs 180 seconds Ge crystal Collimator Source x-y position table Position dependent performance: Singles Source Scans SmartPET - status report AGATA week

  8. The results are presented for 60 keV with 2 minutes of data per position. AC01 AC12 Am-241 AC x-y surface intensity distribution DC12 DC1 SmartPET - status report AGATA week

  9. The influence of charge sharing 10.5M – 9.4M = 1.1M (10.7%) We need to be able to cope with events that share charge between adjacent strips and are not true Compton scatters if we are to image. SmartPET - status report AGATA week

  10. The results are presented for 122 keV with 1 minute of data per position. Source on AC side. Co-57 AC x-y surface intensity distribution SmartPET - status report AGATA week

  11. The results are presented for 122 keV with 1 minute of data per position. Source on DC side. Co-57 DC x-y surface intensity distribution SmartPET - status report AGATA week

  12. The results are presented for 122 keV with 1 minute of data per position. The source was on the AC side. Co-57 AC x-y surface rise time distribution T30 = T30 – T10 T90 = T90 – T10 SmartPET - status report AGATA week

  13. The results are presented for 122 keV with 1 minute of data per position. The source was on the AC side. Co-57 DC x-y surface rise time distribution T30 = T30 – T10 T90 = T90 – T10 SmartPET - status report AGATA week

  14. The results are presented for 122 keV with 1 minute of data per position. Co-57 side surface intensity distribution SmartPET - status report AGATA week

  15. Co-57 side surface T30 rise time distribution T30 AC SmartPET - status report AGATA week T30 DC

  16. Co-57 side surface T90 rise time distribution T90 AC SmartPET - status report AGATA week T90 DC

  17. 137Cs Intensity map AC • The performance of the detector has been investigated use a 137Cs source to probe the response to gamma-ray photons. Depth DC SmartPET - status report AGATA week

  18. SmartPET detector depth response “superpulse” pulse shapes for 137Cs events versus depth AC signals DC signals SmartPET - status report AGATA week DC signals AC signals

  19. Average pulse shape vs depth 50 % SmartPET - status report AGATA week 10 % T50

  20. Contribution of holes and electrons? Edge effects? Middle of detector T50 response on the DC side SmartPET - status report AGATA week Distance away from contact

  21. Recalculation of the position • T50 is a good measure to evaluate the depth of interaction inside the major part of the detector Gaussian fit: σ = 1 mm Position from table (mm) Position from T50 fit (mm) SmartPET - status report AGATA week

  22. The typical maximum size of an image charge pulse is 15% that of the real charge signal. 241Am pulse response. SmartPET : Image charge response SmartPET - status report AGATA week e- h

  23. The typical maximum size of an image charge pulse is 15% that of the real charge signal. 241Am pulse response. SmartPET : Image charge response SmartPET - status report AGATA week e- h

  24. The typical maximum size of an image charge pulse is 15% that of the real charge signal. 241Am pulse response. SmartPET : Image charge response SmartPET - status report AGATA week e- h

  25. The typical maximum size of an image charge pulse is 15% that of the real charge signal. 241Am pulse response. SmartPET : Image charge response SmartPET - status report AGATA week e- h

  26. The typical maximum size of an image charge pulse is 15% that of the real charge signal. 241Am pulse response. SmartPET : Image charge response SmartPET - status report AGATA week e- h

  27. Electric field simulations have been performed and comparisons have been made with experimental pulse shape data. I Geometry II Potential Electric field III Drift velocities IV Weighting fields SmartPET detector response Electric Field Simulations : MGS SmartPET - status report AGATA week

  28. MGS pulse shapes vs depth MGS detector simulation SmartPET - status report AGATA week

  29. Three 22Na Point Sources • Coincidence Mode • 108mm detector separation SmartPET Results imaging results SmartPET - status report AGATA week

  30. y y y y x x x x Initial Image Reconstruction • Filtered Back Projection (FBP) & ML-EM • Treats problem as 12 independent sets of 2D data SmartPET - status report AGATA week z

  31. Three 22Na Point Sources. • 36 projections (angles) between 0 and 180 (5° increments) • 7.5 hours data collection per projection. (270 hours total) Measurement – No Scatter Total Data Collected: ~ 3,000 Gb (13 SDLT tapes) Total Number of Events: ~ 100,000,000 Data Zero-Suppressed: ~ 760 Gb (25%, 4 SDLT tapes) (Trace Reduction) Presorted for 1,1,1,1 events: ~ 110 Gb (3% size, 18% events) - Single strip fires on DC and AC side of both detectors SmartPET - status report AGATA week

  32. Measurement – No Scatter • [1,1,1,1] Events • Total: 18 million events, 110 Gb of data • Per projection:Ave 50,000 counts, 3 Gb of data Using Pixelation of detector gives up to 20,736 (144*144)unique Lines of Response (LoR) per projection. 144 LoRs to face of detectors. Number of events in each LOR histogramed: i) All events ii) 511 keV gated ( ± 20 keV) Two sets of image data (sinograms), gated and ungated Currently only parallel LORs used as these are simplest to image SmartPET - status report AGATA week

  33. 80mm Three Point Sources Initial Image ReconstructionEnergy Gated (FBP, Ramp Filter) 1 2 3 4 Summed image 5 6 7 8 9 10 11 12 SmartPET - status report AGATA week Each image has been scaled individually

  34. Initial Image ReconstructionNo Energy Gated (ML-EM, 100 Iterations) 1 2 3 4 5 6 7 8 9 10 11 12 SmartPET - status report AGATA week Three Point Sources Each image has been scaled individually

  35. Initial Image Reconstruction SmartPET - status report AGATA week

  36. Commission new SmartPET digital DAQ. Complete detector characterisation. Implement level 1 and 2 algorithms. Record and image “real time”. SmartPET project : Future work SmartPET - status report AGATA week

  37. The SmartPET Project SmartPET - status report AGATA week Andy Boston ajboston@liv.ac.uk

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