labr 3 and lyso monolithic crystals coupled to photosensor arrays for tof-pet

Peter DendoovenPeter Dendooven

LaBrLaBr33 and LYSO monolithic and LYSO monolithic

crystals coupled to photosensor crystals coupled to photosensor arrays for TOF-PETarrays for TOF-PET

Physics for Health in Europe WorkshopPhysics for Health in Europe WorkshopFebruary 2-4, 2010, CERNFebruary 2-4, 2010, CERN

Physics for Health in Europe February 2-4, 2010, CERNPeter Dendooven

ContentsContents

• introduction– time-of-flight positron emission tomography (TOF-PET)– monolithic vs. block detectors

• experiments • results• conclusions and outlook


Time-of-flight PET (TOF-PET)Time-of-flight PET (TOF-PET)

500 ps 7.5 cm

uniform probability on line-of-response

€

Δx=cΔt2

W.W. Moses, IEEE Trans. Nucl. Sci. 50 (2003)1325


Monolithic vs. block detectorsMonolithic vs. block detectors

scintillator read out bypixellated photosensor

scintillatorpixellatedsensor

pixellated scintillator blockread out by 4 photosensors

scintil

lator

pixels

PMTs

PMTs


3D photoconversion position3D photoconversion position

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”

xy

z (DOI)

DOI


Effect of time walk vs. positionEffect of time walk vs. position

W.W. Moses and S.E. Derenzo, IEEE Trans. Nucl. Sci. 46 (1999) 474-478

γ

crystal pixel monolithic crystal

γ

γPMT

PMT

~150 ps/cm

surface reflection

crystal surfaces are far away:• smaller time walk ?• how to correct ?


Detector components for fast timingDetector components for fast timing

fast photonsensor arrays

Multi-anode PMTHamamatsu H8711-03

SiPM arrayHamamatsu MPPC S11064-050P(X1)

fast dedicated electronics

fast and bright crystals

16-channel fast amplifierfor SiPM array


Set-up LYSO:Ce + MA PMTSet-up LYSO:Ce + MA PMT

XP2020Q

BaF2

25.4 mm x 20 mm

collimator

22Na

monolithic LYSO:Ce20x20x12 mm3

H8711-03

spectralonx

y

z

5 mm

40 cm5 cm

translationstages

high-speed digitizer

16-channel QDC

anodedynode 16 anodes

last dynode

AND

ch 1 ch 2

trigger intrigger out

gate in in

anode #64.2 mm

1 event = 16 energies + 2 timing signal traces


Set-up LaBrSet-up LaBr33:Ce(5%) + SiPM array:Ce(5%) + SiPM array

22Na

bare LaBr3:Ce(5%)

3x3x5 mm3

Hamamatsu S11064-050P(X1)4 x 4 array, 3x3 mm2 pixels50 m microcell (3600 per pixel)

bare LaBr3:Ce(5%)

16.2x18x10 mm3

polished, teflon-wrapped

combined timing output with extra amplification

to 8 GS/s digitizer

16 channel preamp

16 energy outputs


3D photoconversion position: method3D 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.


3D photoconversion position: results3D photoconversion position: results

• 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

y profilex profile

LYSO:Ce + MAPMT


Coincidence timing resolution (CTR)Coincidence timing resolution (CTR)

FWHM:235 ps

single detector resolution:224 ps FWHM

“scanner” CTR: 315 ps

LaBr3:Ce(5%) + SiPM arrayvs. small LaBr3:Ce(5%) + SiPM

LYSO:Ce + MA PMTvs. BaF2 + PMT

single detector resolution:310 ps FWHM

“scanner” CTR: 440 ps

FWHM:358 ps


DOI (mm)0 2 4 6 8

20

0

-2010

Position-dependent time walkPosition-dependent time walk

LaBr3:Ce(5%) + SiPM array LYSO:Ce + MA PMT

R. Vinke et al., 2008 IEEE Nucl. Sci. Symp. Conf. Rec. M06-207R. Vinke et al., 2009 IEEE Nucl. Sci. Symp. Conf. Rec. M06-2R. Vinke et al., submitted to Nucl. Instr. Meth. A


Time walk correctionTime walk correction

LYSO:Ce + MA PMT

residual time walk is negligeable

resulting CTR = 354 ps FWHM


• 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

Timing resolution with small crystalsTiming resolution with small crystalsindicates the limit of a crystal-sensor combination


Time pickoffTime pickoff

digitized timing signal



cubic spline interpolation to recover waveform




determination of baseline level directly before pulse onset

baseline


baseline



determination of baseline level directly before pulse onset

timestamp based on constant level with respect to baseline (leading edge pickoff)


100 ps CTR for LaBr100 ps CTR for LaBr33 + SiPM + SiPM

timing spectrum shifts according to

103.4 ps 99.5 ps 101.8 ps

20 mm 20 mmR.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

CTR for LYSO:

170 ps FWHM


ConclusionsConclusions

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

LYSO:Ce LaBr3:Ce(5%)

monolithic 440 315

small crystal 170 100

coincidence timing resolutions (ps)


OutlookOutlook

thicker crystals

up to 20 mm

new project:

use of TOF-PET for proton dose verification in proton therapy ?

16 channel preamp

small crystal

timing channels

new 16-channel amplifier

CTR < 300 ps for LYSO:Ce

CTR < 200 ps for LaBr3:Ce ?

R. Vinke, H. Löhner,

F. Schreuder, P. Dendooven

D. Schaart, S. Seifert, M. de Boer,

H. van Dam, F. Beekman


no TOF ~600 ps TOF

www.medical.philips.com Philips Gemini TruFlight PET/CT promo brochure

Why do we do this ?Why do we do this ?

TOF-PET allows

•better image

•shorter scan

•smaller radiation dose to patient

labr 3 and lyso monolithic crystals coupled to photosensor arrays for tof-pet

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