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Ce doped lanthanum tri-bromide crystal: recent advances in scintillation imaging

Ce doped lanthanum tri-bromide crystal: recent advances in scintillation imaging. Roberto Pani On behalf of SCINTIRAD Collaboration INFN and Sapienza-University of Rome Italy. LaBr 3 :Ce/PMT Pulse height non linearity. Co 60 gamma ray pulse height spectra measured with LaBr 3 :Ce

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Ce doped lanthanum tri-bromide crystal: recent advances in scintillation imaging

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  1. Ce doped lanthanum tri-bromide crystal: recent advances in scintillation imaging Roberto Pani On behalf of SCINTIRAD Collaboration INFN and Sapienza-University of Rome Italy

  2. LaBr3:Ce/PMT Pulse height non linearity Co60 gamma ray pulse height spectra measured with LaBr3:Ce at cathode voltages a) HV = -500 V and b) HV = -700 V. Gamma Ray Spectroscopy With a Ø 19 x19 mm3 LaBr3 : 0:5% Ce3+ Scintillator P. Dorenbos, J. T. M. de Haas, and C. W. E. van Eijk, Member, IEEE TRANSACTIONS ON NUCLEAR SCIENCE, VOL. 51, NO. 3, JUNE 2004

  3. Scintillation crystals • Planar LaBr3:Ce 49494 mm3 + 3 mm glass window • Planar NaI(Tl) 49494 mm3 + 3 mm glass window • LaBr3:Ce cylinder ½” Ø  ½” thickness (gold standard)

  4. R6231 Hamamatsu:optimized PMT for LaBr3:Ce crystal • QE typ. = 30 % @ 420 nm • Number of dinode = 8 • Gain= 2.7 E+05 @ HV= -1000 V • Voltage Divider modified by Saint Gobain

  5. Pulse height linearity vs photon energy Hamamatsu R6231 HV=-1000V

  6. Planar LaBr3:Ce 49x 49 x 4 mm3 + 3 mm window Planar NaI(Tl) 49x 49 x 4 mm3 + 3 mm window Cylinder LaBr3:Ce ½” Ø x ½ “ thickness Energy resolution FWHM R6231 Hamamatsu PMT @ HV=-1000 V

  7. Overall EnergyResolution: Theory • Rs= intrinsic resolution of scintillator crystal • N = mean value of photon • = 0.3 , =0.98,  ~4.8 (PMT R6231 Hamamatsu @ HV=-1000 V) • Photon Energy 122 keV a:Comparative study of scintillators for PET/CT detectorsNassalski, A.; Kapusta, M.; Batsch, T.; Wolski, D.; Mockel, D.; Enghardt, W.; Moszynski, M.;Nuclear Science Symposium Conference Record, 2005 IEEE, Volume 5,  23-29 Oct. 2005 Page(s):2823 – 2829

  8. LaBr3:Ce - Energy Resolution Summary a:Comparative study of scintillators for PET/CT detectorsNassalski, A.; Kapusta, M.; Batsch, T.; Wolski, D.; Mockel, D.; Enghardt, W.; Moszynski, M.;Nuclear Science Symposium Conference Record, 2005 IEEE, Volume 5,  23-29 Oct. 2005 Page(s):2823 – 2829 bX-ray and gamma-ray response of a 2”x2” LaBr3:Ce scintillation detector F. Quarati, A.J.J. Bos, S. Brandenburg, C. Dathy, P. Dorenbos, S. Kraft,R.W. Ostendorf, V. Ouspenski, Alan Owens, Nuclear Instruments and Methods in Physics Research A 574 (2007) 115–120

  9. 15 mm 50 mm H8500 Hamamatsu FP : • Metal channel dynode • QE typ. = 24 % @ 420 nm • Number of dinode = 12 • Gain= 1.5 E+06 typ. • Number of anodes = 8 x 8 array (6.08 mm pitch) Energy resolution analysis The output signal was obtained from the short circuit of all anodic signals

  10. Pulse height linearity vs photon energy LaBr3:Ce continuous crystal + Hamamatsu H8500 FP (sc anode) HV=-1000V

  11. Planar LaBr3:Ce 49 x 49 x 4 mm3 + 3 mm glass window Energy resolutionH8500 Hamamatsu F.P. (sc anode) @ HV= -1000V

  12. R7600-200 Hamamatsu PMT • QE max. = 41.6 % @ 380 nm • Number of dinode = 10 • Gain= 2.0 E+06 @ HV=-800 V LaBr3:Ce Cylinder (½”Ø  ½” thickness)

  13. 32 keV NaI(Tl) planar + R6231 81 keV 356/380 keV 274/302 keV 356 keV 302 keV 274 keV 380 keV R7600-200 HamamatsuLaBr3:Ce Cylinder (½” Ø x ½ “ thickness)Ba133 source HV=-700V

  14. Spatial Resolution PSF image PSF Image Scintillation event Light PSF Co57 pulse height analisys Position linearity

  15. New algorithm: Standard algorithm: t = threshold (0÷1) LaBr3:Ce Charge spread HV=-825V After procedure Centroid Algorithmfor small FoV gamma camera

  16. Performances Analysis: LaBr3(Ce) 49  49  4 mm3 + 3 mm glass window • Coupled to the MA-PMT H8500 tube • 0.4 mm Øcollimated Tc99m source (140 keV photon energy) 1.5 mm step scanning • Image analysis with and without new algorithm

  17. HV = - 750V SR = 1.90 mm SR=1.36 mm SR = 1.67 mm SR=1.28 mm HV = - 800V LaBr3(Ce): Overall Spatial Resolution@140 keV New algorithm Standard algorithm

  18. Experimental data vs Monte Carlo simulation GEANT4: Pulse Height Centroid @ 140 keV

  19. Experimental data vs Monte Carlo simulation: Charge distribution spread @ 140 keV LaBr3:Ce 49x49x4 mm3 continuous crystal + H8500 MA-PMT Monte Carlo Simulation

  20. Experimental data vs Monte Carlo simulation: Spatial resolution & position linearity without new centroid algorithm LaBr3:Ce 49x49x4 mm3 + 3mm glass window continuous crystal + 8x8 anode array • Experimental measurement: • 0.4 mm Ø point source Tc99m • 1.5 mm step • Monte Carlo simulation: • 140 keV photon energy • 6 mm step

  21. Experimental data vs Monte Carlo simulation: Spatial resolution & position linearity with new centroid algorithm LaBr3:Ce 49x49x4 mm3 + 3mm glass window continuous crystal + 8x8 anode array • Experimental measurement: • 0.4 mm Ø point source Tc99m • 1.5 mm step • Monte Carlo simulation: • 140 keV photon energy • 6 mm step

  22. Conclusions • LaBr3:Ce seems a very attractive scintillation crystal for SPET application (140 keV) • At 140 keV photon energy, continuous crystal can allow the highest values of spatial resolution, energy resolution and detection efficiency • Hamamatsu MAPMT photodetector are limiting energy resolution and spatial resolution response • Probably the new ultra high Q.E. MAPMT could solve such limitations

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