LaBr 3 and LYSO monolithic crystals coupled to photosensor arrays for TOF-PET

1. Peter Dendooven LaBr3 and LYSO monolithic crystals coupled to photosensor arrays for TOF-PET Physics for Health in Europe Workshop February 2-4, 2010, CERN

2. Contents • introduction • time-of-flight positron emission tomography (TOF-PET) • monolithic vs. block detectors • experiments • results • conclusions and outlook

3. Time-of-flight PET (TOF-PET) uniform probability on line-of-response 500 ps  7.5 cm W.W. Moses, IEEE Trans. Nucl. Sci. 50 (2003)1325

4. Monolithic vs. block detectors scintillator read out by pixellated photosensor pixellated scintillator block read out by 4 photosensors pixellated sensor scintillator PMTs scintillator pixels

5. 3D photoconversion position DOI Anger logic x,y position resolution: pixel size depth-of-interaction (DOI) requires special tricks light distribution over sensor array x,y,z position resolution < sensor pixel size depth-of-interaction (DOI) “included” z (DOI) x y

6. Effect of time walk vs. position crystal pixel monolithic crystal • crystal surfaces are far away: • smaller time walk ? • how to correct ? PMT γ γ PMT γ surface reflection ~150 ps/cm W.W. Moses and S.E. Derenzo, IEEE Trans. Nucl. Sci. 46 (1999) 474-478

7. Detector components for fast timing fast and bright crystals fast photonsensor arrays Multi-anode PMT Hamamatsu H8711-03 SiPM array Hamamatsu MPPC S11064-050P(X1) fast dedicated electronics 16-channel fast amplifier for SiPM array

8. Set-up LYSO:Ce + MA PMT y spectralon monolithic LYSO:Ce 20x20x12 mm3 x BaF2 25.4 mm x 20 mm 22Na z XP2020Q collimator H8711-03 last dynode 16 anodes dynode 5 mm anode translation stages 40 cm 5 cm 4.2 mm AND anode #6 16-channel QDC high-speed digitizer gate in in ch 1 ch 2 trigger in 1 event = 16 energies + 2 timing signal traces trigger out

9. Set-up LaBr3:Ce(5%) + SiPM array Hamamatsu S11064-050P(X1) 4 x 4 array, 3x3 mm2 pixels 50 mm microcell (3600 per pixel) bare LaBr3:Ce(5%) 16.2x18x10 mm3 polished, teflon-wrapped 16 channel preamp bare LaBr3:Ce(5%) 3x3x5 mm3 16 energy outputs 22Na combined timing output with extra amplification to 8 GS/s digitizer

10. 3D photoconversion position: method procedure: • calibration scan across the front surface (XY-scan) • calibration scan across one side surface (YZ-scan) • 3D photoconversion position determination using a maximum likelihood estimation (MLE) algorithm • FWHM position resolution ~2.5 mm in 3D R. Vinke, et al. “Time walk correction for TOF-PET detectors based on a monolithic scintillation crystal coupled to a photosensor array”, submitted to Nucl. Instr. Meth. A.

11. 3D photoconversion position: results LYSO:Ce + MAPMT x profile y profile • x,y resolution(FWHM) • ~2.4 mm • slight DOI dependence • DOI-resolution (FWHM) • 2.3 mm near PMT • 4 mm at 10 mm from PMT • edge artifacts

12. Coincidence timing resolution (CTR) FWHM: 235 ps LaBr3:Ce(5%) + SiPM array vs. small LaBr3:Ce(5%) + SiPM LYSO:Ce + MA PMT vs. BaF2 + PMT FWHM: 358 ps single detector resolution: 224 ps FWHM “scanner” CTR: 315 ps single detector resolution: 310 ps FWHM “scanner” CTR: 440 ps

13. Position-dependent time walk LaBr3:Ce(5%) + SiPM array LYSO:Ce + MA PMT 20 0 -20 0 2 4 6 8 10 DOI (mm) R. Vinke et al., 2008 IEEE Nucl. Sci. Symp. Conf. Rec. M06-207 R. Vinke et al., 2009 IEEE Nucl. Sci. Symp. Conf. Rec. M06-2 R. Vinke et al., submitted to Nucl. Instr. Meth. A

14. Time walk correction LYSO:Ce + MA PMT residual time walk is negligeable resulting CTR = 354 ps FWHM

15. Timing resolution with small crystals indicates the limit of a crystal-sensor combination • crystal: 3x3x5 mm3 • bare LaBr3:Ce(5%) • LYSO • Hamamatsu SiPMS10362-33-050c • spectralon reflective material • Agilent DC282 digitizer • 8 GS/s • 700 MHz anti-aliasing filter • extra amplification timing channel

16. Time pickoff digitized timing signal

17. Time pickoff cubic spline interpolation to recover waveform

18. Time pickoff cubic spline interpolation to recover waveform determination of baseline level directly before pulse onset baseline

19. Time pickoff cubic spline interpolation to recover waveform determination of baseline level directly before pulse onset timestamp based on constant level with respect to baseline (leading edge pickoff) baseline

20. 100 ps CTR for LaBr3 + SiPM 103.4 ps 99.5 ps 101.8 ps timing spectrum shifts according to CTR for LYSO: 170 ps FWHM R.Vinke et al., 2009 IEEE Nucl. Sci. Symp. Conf. Rec. M06-2 S.Seifert et al., 2009 IEEE Nucl. Sci. Symp. Conf. Rec. J01-4 20 mm 20 mm

21. Conclusions • benefits of monolithic detectors for TOF-PET: • maximum sensitivity • 3D photoconversion position can be determined • FWHM ~2.5 mm • position-dependent time walk can be corrected to < ±10 ps • parallax error can be avoided coincidence timing resolutions (ps)

22. Outlook thicker crystals up to 20 mm timing channels new 16-channel amplifier CTR < 300 ps for LYSO:Ce CTR < 200 ps for LaBr3:Ce small crystal ? 16 channel preamp new project: use of TOF-PET for proton dose verification in proton therapy ? R. Vinke, H. Löhner, F. Schreuder, P. Dendooven D. Schaart, S. Seifert, M. de Boer, H. van Dam, F. Beekman

23. Why do we do this ? • TOF-PET allows • better image • shorter scan • smaller radiation dose to patient no TOF ~600 ps TOF www.medical.philips.com Philips Gemini TruFlight PET/CT promo brochure