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Maurizio Conti, Siemens Molecular Imaging, Knoxville, Tennessee, USA

Maurizio Conti, Siemens Molecular Imaging, Knoxville, Tennessee, USA. Detectors for PET. Summary. introduction inorganic scintillators TOF detectors new light sensors and scintillators. Detection process:. positron emission and annihilation two g emission

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Maurizio Conti, Siemens Molecular Imaging, Knoxville, Tennessee, USA

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  1. Maurizio Conti, Siemens Molecular Imaging, Knoxville, Tennessee, USA Detectors for PET

  2. Summary introduction inorganic scintillators TOF detectors new light sensors and scintillators

  3. Detection process: positron emission and annihilation two g emission g interaction in the patient body and absoption or scatter g interaction in the detectors (scintillator+photodetector or solid state devices) Most common detector: inorganic scintillator + Photo Multiplier Tube (PMT)

  4. e+ e- g detector Light detector Dt coincidence

  5. g detector: scintillator g detector: scintillator PMT Light detector (APD, SiPM) • detector = solid state detector (Si, CZT) Detector components

  6. X = A / (A + B) Detector architecture: the block E B A X1 = 100 / (100 + 0) = 1 X2 = 55 / (55 + 45) = 0.55

  7. Anger Logic Y X

  8. 1986 - ECAT with Block Detector

  9. PMTs 36 cm 52 cm Detector architecture: the panel scintillator light guide scintillator PMTs

  10. Compton Effect E’ E  e- Eel EC E -E’

  11. E Photoelectric Effect E e-

  12. Interaction cross sections mx r LSO LaBr3 m m Compton photoelectric 511 keV 511 keV

  13. A good detector must have: high density and Z: ephµ r Z4 andeCompµ rZ high light output: energy and time resolution µ1 / N1/2 short rise time and decay time: time resolutionand dead timeµta if scintillator, > 400 nm emission wavelength (better for PMTs) solid technology: not hygroscopic, uniform, easy to make, low cost, etc

  14. Characteristics of Selected Scintillators

  15. NEC, the noise equivalent count rate, • NEC = [(True+scatter)*(1-scf)]2/[True+scatter + randoms] • NEC is related with image quality. ”The higher the NEC the better the images”.

  16. Search for new scintillators Ce3+ 5d-4f transition

  17. Search for new scintillators P. Dorenbos, Presentedat SCINT09, JejuIsland, Korea, June 2009

  18. First Paper on LSO Ce3+ 5d-4f transition

  19. LSO Energy Spectrum

  20. LSO manufacturing

  21. Comparing fast scintillators with TOF PET potentiality(experimental work, presented at SORMA conference, 2008) Emission and excitation spectra Decay time Absolute light output Time resolution Figure of merit for TOF PET

  22. Materials

  23. Emission and excitation spectra

  24. Amp474(x10) Trigger (anode) start CFD935 TAC567 MCA Measure (anode) CFD935 stop delay Decay time measurement LSO one component, 30-37ns PMT=XP2020Q Cs137 source

  25. Decay time measurement LuYAP LuAG fast component, 16 ns (57%) 145 ns (22% 594 ns (21%) fast component, 18 ns (77%) 530 ns (23%)

  26. Decay time measurement LaBr3 LaCl3 one component, 17 ns fast component, 18 ns (70%) 125 ns (21%) 220 ns (9%)

  27. MCA Tukan-8k dynode Absolute light output Self-absorption observed: lower light output in larger crystals Lower than in data sheet Cs137 source PMT=H3177 Pre Amplifier Canberra 2005 Spectroscopy Amplifier Ortec 672 (3ms shaping)

  28. D#1 (anode) start CFD935 TAC567 MCA D#2 (anode) stop CFD935 delay strobe PreAmp113 (100pF) Amp855 (x40/5,1.5us) D#1 (dynode) SCA551 Fast Coinc 414A D#2 (dynode) SCA551 Time resolution measurement Na22 source PMT=XP2020Q FWHM of the gaussian fit

  29. Time resolution measurement LuYAP LuAG LaCl LSO LaBr N= ph-e (includes E and QE)

  30. Figure of merit to compare scintillators for TOF PET Fast is not enough! Needs to be bright and dense! N= ph-e (includes E and QE)

  31. Figure of merit (conventional) Image quality (or SNR) depends on number of coincidence counts in the scan Detection efficiency Coincidence efficiency Deposited energy (MeV) PPF=PhotoPeakFraction

  32. Hyman theory PMT noise/gain Discriminator level Decay time

  33. Time resolution estimate 0 < a < 1 PET scanner system time resolution

  34. NaI LaCl LGSO LaBr3 LSO YAP LuAP CsF2 plastic Hyman theory Fast Photomultipliers for TOF PET T. Szczesniak, M. Moszynski, L. Swiderski, A. Nassalski, P. Lavoute, M.Kapusta 2007 TNS conf record

  35. Conventional sensitivity TOF sensitivity gain or amplification Overall sensitivity of TOF PET scanner Figure of merit (with TOF)

  36. nonTOF TOF Figure of merit for TOF PET

  37. Figure of merit for TOF PET scintillators

  38. bright dense fast New scintillators for TOF PET ? • Dense • Bright • Fast LSO/LYSO is dominating now….

  39. New scintillators for TOF PET ? Derenzo and Moses (LBNL, Berkeley): Systematic search of new scintillators, combining powders and testing with X-rays microcrystals Hundreds of compounds tested.

  40. New scintillators for TOF PET ?

  41. New scintillators for TOF PET ? • New approaches: • Crystals with a highly populated donor band (ZnO) • Nanocrystals with quantum dots • Make use of Cerenkov light • Improve light collection with photonic crystals

  42. Improve light collection with photonic crystals 100x100mm2 10 mm 2.5 mm 2.8mm 1.3mm 0.6mm LSO crystal

  43. Improve light collection with photonic crystals

  44. New photodetectors for TOF PET ? • Fast • Efficient • Count rate capability • Small dead areas, compact and scalable When will SiPM get there ? ….

  45. SiPM: new photodetectors for TOF PET ?

  46. SiPM: new photodetectors for TOF PET ?

  47. SiPM: new photodetectors for TOF PET ?

  48. SiPM: new photodetectors for TOF PET ?

  49. SiPM: new photodetectors for TOF PET ?

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