1 / 28

A novel gamma-ray detector with sub-millimeter resolutions using a monolithic MPPC array

A novel gamma-ray detector with sub-millimeter resolutions using a monolithic MPPC array with pixelized Ce:LYSO and Ce:GGAG scintillators. Takuya Kato J.Kataoka, T.Nakamori, T.Miura, H.Matsuda A.Kishimoto ( Waseda Univ .)

joyce
Télécharger la présentation

A novel gamma-ray detector with sub-millimeter resolutions using a monolithic MPPC array

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 novel gamma-ray detector with sub-millimeter resolutions using a monolithic MPPC array with pixelized Ce:LYSO and Ce:GGAG scintillators Takuya Kato J.Kataoka, T.Nakamori, T.Miura, H.Matsuda A.Kishimoto (Waseda Univ.) K.Sato, Y.Ishikawa, K.Yamamura, S,Nakamura N.Kawabata (Hamamatsu) H.Ikeda (ISAS/JAXA) S.Yamamoto (KCCT) K.Kamada (Furukawa Co., Ltd.) 8 December 2011 8th Hiroshima Symposium @ Academia Sinica, Taipei

  2. 2 Contents PET and our approach Performances of the MPPC array Charge division readout technique Sub-millimeter pixelized scintillators Future prospects and summary

  3. 3 Positron Emission Tomography ⇒Well-established method for detecting cancers • Functional imaging with 511keV annihilation gamma-ray • Time of Flight(ToF) and Depth of Interaction(DoI) information improve image quality DoI Cancer ⇒compactness, low power and high time resolution are required ToF • MRI-PET has become common as a multimodality imaging device ⇒insensitivity to B fields is required PMT is incorporated in conventional PET scanner However, PMT is … • intricate in construction • large size • sensitive to B fields PMT Scintillator APD can overcome these points

  4. 4 APD-PET project Kataoka, Matsuda et al. 2009, NIM-A, 2010 IEEE-TNS Koizumi et al. 2009, Yoshino et al. 2011, NIM -A APD is a compact and insensitive to B fields Developed large size APD and dedicated LSI Sub-millimeter resolution was achived 256ch APD-array • APD gain is relatively low (~50) 3.1ns (FWHM) ⇒easily affected by electric noise contamination • Time resolution is a few ns ⇒unfavorable for ToF

  5. 5 Multi-Pixel Photon Counter Geiger -mode quenching resistor I Geiger-mode APD quenching discharge ON Off ~50ns V Vbr Vop charge • 2D-array of Geiger mode APD pixels • charges proportional to the number of fired pixels • compact • low bias voltage (<100V) • high gain (105~106) • insensitive to B fields

  6. 6 Characteristics summary APD PMT PD MPPC 50-100 gain 105~6 1 105~6 Q.E. (PDE) >25 >80 >25 volume small large interfered by B yes no structure complex simple low high power consumption suitable for PET • High gain, doesn’t need CSA ⇒much betterS/N ⇒much better time resolution (suitable for ToF-PET) • Less photon-detection efficiency ⇒worse energy resolution • Narrow dynamic range due to limited number of pixels ⇒need linearity correction

  7. 7 4 × 4 Monolithic MPPC array • 4×4 array with 3×3mm2 pixel • 50μm type (3600 APDs/pixel) • 0.2mm gap • With FPC(flexible printed circuit) • monolithic • buttable • low dark counts rate (400kcps @ 20deg) 13.6mm 13.6mm Gain vs Voltage Gain map@72.01V, 20deg Gain (×105) ±5.6% 10 3.5 averaged gain = 7.5 × 105 71.5 72.5 Bias Voltage [V]

  8. 8 Performance with Ce:LYSO • 4×4 array of 3×3×10mm3 crystals • reflective BaSO4 layer divide pixels • coupled using optical grease • irradiated by 137Cs @20deg, 72.01V ρ=7.10 g/cm3 25 ph/keV τ=40 ns LYSO array 137Csspectra energy resolution map Counts 11.5±0.5% (FWHM) for 662keV Energy [keV]

  9. 9 Time resolution of the MPPC array reference detector • PMT • 3×3×10mm3 Ce:LYSO crystal PMT LYSO start CFD TAC 22Na PHADC LYSO CFD delay stop MPPC array time resolution map 493±22ps(FWHM)

  10. 10 Charge division readout technique • often used for MAPMT • 16 anodes are connected to red circles • interaction positions are calculated by centroid method • irradiatedby 137Cs @20deg, 72.01V 137Cs ×10 linear amp ×16ch Fan I/O 100ns delay resistor network CSADC gate (700ns) 4ch analog sum Gate Generator Discriminator

  11. 11 Result of charge division readout flood image 137Cs spectra Y position (a.u.) Counts X position (a.u.) averaged FWHM of peaks Energy [keV] • 4×4pixels are clearly resolved • averaged FWHM of peaks is 0.19mm • spectra are extracted from flood image • energy resolution is slightly better 10.2±0.4% (FWHM) for 662keV

  12. 12 Sub-millimeter pixelized scintillator Ce:LYSO Ce:GGAG ρ=6.63 g/cm3 42 ph/keV τ=52.8 12×12 array 1.0×1.0×10mm3 17×17 array 0.7×0.7×10mm3 22×22 array 0.5×0.5×10mm3 • Ce:GGAG is a brand-new scintillator which has very large light yield • 0.1mm thick BaSO4 layer • coupled with 1mm thick acrylic light guide • read out by resistor network scintillator light guide resistor network MPPC array

  13. 13 Comparison between LYSO and GGAG 137Cs spectra LYSO GGAG 3mm 9.7% (FWHM) 7.9% (FWHM) 3mm • 3×3mm2 , 50μm type MPPC • 3×3×10mm3 scintillator crystals Normalized counts pulse shapes of 662keV photoelectric absorption events Charge[pC] • GGAG has larger light yield ⇒GGAG has better energy resolution • Decay time of LYSO is shorter ⇒LYSO is suitable for ToF

  14. 14 1.0mm2 Ce:LYSO array flood image 137Cs spectra Y position (a.u.) Counts X position (a.u.) Energy [keV] • irradiate by 137Cs • side pixels are overlapped, but central 8×8 pixels are successfully resolved • energy spectra are extracted from flood image 11.5±0.9% (FWHM) for 662keV

  15. 15 0.7 and 0.5mm2 arrays flood images 0.7mm2Ce:LYSO 0.5mm2Ce:LYSO 0.5mm2Ce:GGAG Y position (a.u.) Y position (a.u.) Y position (a.u.) X position (a.u.) X position (a.u.) X position (a.u.) 11.7±0.7% 14.3±1.8% 12.0±1.3% (FWHM) for 662keV • irradiated by 137Cs • side pixels are overlapped, but central pixels are successfully resolved • energy resolution of GGAG is better than that of LYSO

  16. 16 Future prospects tweezers type coincidence imaging system Yamamoto et.aｌ. 2011, IEEE • Monolithic MPPC array with FPC cable ⇒more compact • Sub-millimeter pixelized scintillator ⇒much better spatial resolution • Experimental coincidence measurements are conducted 22Na • Simple 2-dimensional geometrical reconstruction is achieved ~1.3mm (FWHM) ⇒~1.3mm (FWHM) resolution

  17. 17 Summary • We developed 4×4monolithic MPPC array • Fine gain uniformity of ±5.6% and low dark count rates of ~400kcps were obtained • We achieved resolving 0.5mm2 pixelized scintillator in flood image • Energy resolution was 10.2% (FWHM @662keV) • Time resolution was 493ps (FWHM) • MPPC with sub-millimeter scintillator could be promising for high spatial and time resolution gamma-ray imaging, particularly in PET scanner

  18. Appendix

  19. About Ce:GGAG Kamada et al. 2011, Cryst Growth Des. Comparison with APD GGAG decay curve decay time 52.8ns (73%), 282ns (27%)

  20. Performances of Hamamatsu MPPC • Low dark count (e.g. 3x3mm2 ,50um pixel) 10Mcps (2007) --> 5Mcps (2009) --> 1Mcps (2010 – best run) --> consolidate • High time resolution (jitter) (e.g. 1x1mm, 1 p.e. level) aro 250ps (2009) --> Lower than 130ps (2010)

  21. Linearity correction 1275keV of 22Na 662keV of 137Cs 511keV of 22Na 356keV of 133Ba 122keV of 57Co

  22. Comparison between MPPC and APD 22Na MCA CSA only when using APDs TAC CFD MPPC or APD 100ns delay CFD Time resolutons MPPC: 624ps(FWHM) APD: 5300ps(FWHM)

  23. Time resolution of APD X-ray beam 1-2 ns width Kataoka et al. 2010, IEEE TAC • 155 ps (FWHM) for 10keVbeam • (=corresponding to the charge of • 511keV when coupled with LYSO) CSA limits time resolution

  24. Setup for measuring gain aluminum case ×100 linear amp 465nm Fan I/O MPPC array CSADC LED gate (100ns) 100s delay Attenuator Clock Generator Gate Generator LED light spectrum offset 1photon Counts Q 2photon 3photon CSADC channel

  25. Dark count rates ~400kcps @ 0.5p.e. level

  26. Gain vs time resolution

  27. Detail about resistor network HV out3 out1 … out4 out2 red：51Ω blue：100Ω

  28. Charges of 662keV photopeak 3mm2 1mm2 1 4 D A 0.7mm2 0.5mm2 1 1 4 4 D A D A

More Related