Joint Dual Photopeak Image Reconstruction in Lu-177 SPECT · 2019-12-17 · Energy Spectrum of...

JointDualPhotopeak ImageReconstructioninLu-177SPECT

2018EANM

HongkiLim,JeffreyFessler,YuniDewarajaUniversityofMichigan,AnnArbor

EANMDisclosure Statement

1) I or one of my co-authors hold a position as an employee, consultant, assessor or advisor for a pharmaceutical, deviceor biotechnology company. If yes, please specify name/position/company:Nothing to disclose

2) I or one of my co-authors receive support from a pharmaceutical, device or biotechnology company. If yes, pleasespecify name/position/company/which project and whether support is in kind or monetary:Yuni Dewaraja is paid consultants forMIM Software Inc., Cleveland, USA

3) I or one of my co-authors hold property rights/patents for (radio)pharmaceuticals, medical devices or medicalconsulting firms. If yes, please specify name/position/company:Nothing to disclose

4)Ioroneofmyco-authorshavewrittenarticlesfor(radio)pharmaceutical,medicaldevice,biotechnologyorconsultingcompaniesduringthelast5years.Ifyes,pleasespecifyname/position/company/article/journalandco-authors:Nothing to disclose

2/21JointdualphotopeakimagereconstructioninLu-177SPECT

HongkiLim(Universityof Michigan)

EnergySpectrumof177Lu

3/21JointdualphotopeakimagereconstructioninLu-177SPECT


1. Ljungberg et al. "MIRD pamphlet no. 26" J Nucl Med 57.1 (2016): 151-62.

q Generalrecommendation1

• MEcollimator+208keV

q Anotheroption

• MEcollimator+113&208keV

0 300Re

lativeCo

unts

Energy(keV)

Simulationwithpointsourceinwaterphantom&MEcollimator

Totalevents PrimaryEvents Total- Primary

EnergySpectrumofLu-177

3/21

q Generalrecommendation

• MEcollimator+208keVàClinicallyadoptedoption

q Anotheroption

• MEcollimator+113&208keV

0 300Re

lativeCo

unts

Energy(keV)



208

JointdualphotopeakimagereconstructioninLu-177SPECT



3/21

q Generalrecommendation

• MEcollimator+208keV

q Anotheroption

• MEcollimator+113&208keVàGoodtousewhen#ofcountsis

insufficient(imagingatlatertimepointorpretherapydiagnosticimaging)

0 300Re

lativeCo

unts

Energy(keV)



113 208




4/21

q Comparedto208-keV,113-keV has

! ~60%ofYield! ~70%PrimaryCounts(cps/MBq)forMEcollimator

0 300Re

lativeCo

unts

Energy(keV)



113 208



Optionsforusingbothphotopeaks- 113&208keV

5/21

q Twooptions1) Reconstructtwoimagesseparately andmakesum

𝑦#~Poisson 𝐴#𝑥# + 𝑠# ,𝑥/# = argmin𝑥#𝑓(𝑥#; 𝑦#, 𝑠#)𝑦8~Poisson 𝐴8𝑥8 + 𝑠8 ,𝑥/8 = argmin𝑥8𝑓(𝑥8; 𝑦8, 𝑠8)𝑥/ = 𝑥/#+𝑥/8

2)Reconstructoneimagejointly

𝑦 =𝑦#𝑦8 ~Poisson( 𝐴#𝐴8

𝑥 +𝑠#𝑠8 )

𝑥/ = argmin𝑥𝑓(𝑥; 𝑦, 𝑠)

• 𝒚#(𝒚8) ismainenergywindowand𝒔#(𝒔8) isscatterenergywindowacquisitionaround208(113)-keV• 𝑓(𝑥)denotesnegativePoisson likelihood function• Forscatterestimation,weusedtriple-energy-window(TEW)technique



Optionsforusingbothphotopeaks- 113&208keV

5/21

àMorealignedwithactualPoissonnatureofmulti-windowacquisition

• 𝒚#(𝒚8) ismainenergywindowand𝒔#(𝒔8) isscatterenergywindowacquisitionaround208(113)-keV• 𝑓(𝑥)denotesnegativePoisson likelihood function• Forscatterestimation,weusedtriple-energy-window(TEW)technique

q Twooptions1) Reconstructtwoimagesseparately andmakesum

𝑦#~Poisson 𝐴#𝑥# + 𝑠# ,𝑥/# = argmin𝑥#𝑓(𝑥#; 𝑦#, 𝑠#)𝑦8~Poisson 𝐴8𝑥8 + 𝑠8 ,𝑥/8 = argmin𝑥8𝑓(𝑥8; 𝑦8, 𝑠8)𝑥/ = 𝑥/#+𝑥/8

2)Reconstructoneimagejointly

𝑦 =𝑦#𝑦8 ~Poisson( 𝐴#𝐴8

𝑥 +𝑠#𝑠8 )

𝑥/ = argmin𝑥𝑓(𝑥; 𝑦, 𝑠)



Whatfactorsneedtobeconsideredforjointreconstruction?

6/21

q SystemModel𝑦#𝑦8 ~Poisson(

𝐴#𝐴8

𝑥 +𝑠#𝑠8 ),

where𝑎EFG = 𝛼G𝑝EFG𝑔EFG

𝑎EFG: elementofsystemmodel(𝐴G) at𝑖-th rowand𝑗-th column in𝑘-th energywindow

𝛼G:Relativecameradetection efficiency × branchingratio𝑝EFG :depth-dependentandenergy-dependenteffectofattenuation𝑔EFG:depth-dependentandenergy-dependent3D-collimator detectorresponse



Experimentalsetting

7/21

q 2measurements+1simulation+1patientscan

I. Spherephantommeasurement(4scans)

II. Liver-torsophantommeasurement(4scanswithhigh/low-counts)

III. XCATphantomsimulation (10realizationswithhigh/low-counts)

IV. Patientscan



Physicalphantommeasurement1

8/21

q Spherephantommeasurement(4scanstoassessnoise)- Sphere-to-backgroundratiowas6:1 ,30minutesacquisition- Mainwindowwidth:20%,scatterwindowwidth:10%

208-keVmainwindow 208-keVscatterwindow




Physicalphantommeasurement2

9/21

q Liver-torsophantommeasurement- 4scanstoassessnoise:

4scanof35 min(mimickingDay3post177Lu-DOTATATE)4scansof3 min(mimickingDay3pre-therapydiagnosticimaging)

- Lesion-to-liverratiowas4:1

35 minutesscan

208-keVmainwindow

113-keVmainwindow

208-keVmainwindow

113-keVmainwindow

3 minutesscanJointdualphotopeakimagereconstructioninLu-177SPECT


XCATsimulation

10/21

q XCATcoupledwithSIMIND2 simulation(10realizationstoassessnoise)- Realisticactivitydistributionfor177Lu-DOTATATE

2. Ljungberg M. Monte Carlo Calculation in Nuclear Medicine: Application in Diagnostic Imaging, 2nd edn, 2012.

OrganRelativeactivity

concentration

Lesioninliver 1.00

Spleen 0.59

Kidney 0.48

Liver 0.16

Gallbladder 0.02

Renalpelvis 0.02

Post-therapyDay1count-level Pre-therapyDay1count-level

208-keVmain 208-keVscatter






177Lu-DOTATATEPatientscan

11/21

q Day5 acquisition- 1clinicalscanwith208-keV (Scannedfor25minutes)- 3researchscanswithboth photopeaks (Scannedfor2 minutestomimicpre-therapy)

25minutesscanatDay5

2minutesscanatDay5






ReconstructionandEvaluationmethods

12/21

I. Activity-recovery

II. Contrast-recovery

III. Image-ensemble-noise(variabilityacrossmultipleacquisitions)

q Reconstructiondetails(forbothsingleandjoint)• AppliedGaussiansmoothingtoTEWscatterestimate• EMalgorithm+50iteration(1subset)

q Evaluationmetrics



Calibrationfactorforabsolutequantification

13/21

1. NISTrecommendation3 (0.9%uncertainty)• 3mL177Luina10mLSchottvial:CRC-15Rdialsetting449x10

2. TransferringCalibrationtoanewgeometry(10mLsyringe)• Activity insyringe=activityinvial- residual

3. Withthesyringe inthedosecalibratoradjustsetting• Settingtogetcorrectreadingfor3mLinsyringe:480x10

Syringe tapedtoSourceholder

q Imagingforcalibrationfactor• planar with20%mainwindow&10%TEWSC

q 208keV(head1):12.9cps/MBq(head2):13.4cps/MBq

à (within1%ofmanuf.specifiedvalue for5/8”xtal)q 113keV(head1): 9.2cps/Mbq (70%ofabove)

(head2):9.3cps/MBq

‘NISTgeometry’fordosecalibrator

Transfertosyringeforfillingphantomandcamerasensitivity

3. Bergeron DE, Cessna JT. Nucl Med Commun. 2018 Jun;39(6):500-504



Result:Spherephantommeasurement

14/21

Single208-keV Single113-keV Joint


0 200 400 600x-axis

0

5

10

Activ

ity (B

q/m

l)

104

TRUESIR 208SIR 113JIR

Profileacrosscoldspot

Profile



Result:Spherephantommeasurement

15/21

0

2

4

6

8

10

12

14

0 50 100 150

ContrastRecoverytoNoiseRatio

SphereSize(ml)

SinglePhotopeakRecon@208-keV


JointPhotopeakRecon

0

20

40

60

80

100

0 20 40 60 80 100 120

ContrastRecovery

SphereSize(ml)



JointPhotopeakRecon

0

20

40

60

80

100

120

0 20 40 60 80 100 120

ActivityRecovery

SphereSize(ml)



JointPhotopeakRecon



Result:Liver-torsophantommeasurement(axialview)

16/21



HighCountsà

LowCountsà



Result:Liver-torsophantommeasurement

17/21

Noise ContrastRecovery CRNR29mlovoid 16mlsphere 29mlovoid 16mlsphere

208-keV 11.4 75.3 70.4 6.6 6.2113-keV 16.4 72.4 66.6 4.4 4.1Joint 9.5 74.4 69.1 7.8 7.2


208-keV 36.4 65.2 63.7 1.8 1.8113-keV 48.5 58.7 51.8 1.2 1.1Joint 29.3 62.1 58.1 2.1 2.0

35 minutesscan

3 minutesscan



Result:XCATphantomsimulation

18/21


208keV 10.1 76.3 92.9 7.5 9.2113keV 12.9 73.3 90.4 5.7 7.0Joint 8.0 75.0 91.8 9.4 11.5


208keV 65.2 75.8 91.7 1.2 1.4113keV 85.5 68.7 91.5 0.8 1.1Joint 52.2 72.8 91.6 1.4 1.8

Post-therapyDay1count-level

Pre-therapycount-level

208-keV 113-keV Joint

208-keV 113-keV Joint

Liver

Kidneys



Result:Patientscan

19/21

25minutes scan,208-keVSPECT/CT

Single208-keVShortScan

Single113-keVShortScan

JointShortScan

Recon(unit:Bq/ml) RMSD* Noise*208-keV 1.47e4 332.9113-keV 1.90e4 278.6Joint 1.45e4 260.4*RMSDrelativetolongscan*Imageensemblenoisebetween3repeatshortscans

Spleen

Liver

Tumor

Single208-keVLongScan



Summary

20/21

q Jointreconstructionw/E-dependentsystemmodel&TEWSCiseasytoimplementq Comparedtosinglephotopeak(208-keV)reconstruction,jointreconstruction- Gavecomparableactivity/contrastrecovery- Improvednoisesignificantlyevenforhigh-countsdataà Importantforvoxel-leveldosimetry- Improvedcontrastrecoverytonoiseratio: 16.7-27.3%

q Jointreconstructioncanbebeneficialforreducingscantime

ExperimentsSpherephantom Liverphantom XCAT

Count-level High Low High Low

Improvement(%) 20.9-23.2 16.7-17.5 17.3-21.5 25.4-25.8 24.7-27.3

Improvement(%)ofContrastRecoverytoNoiseRatiooversingle208-keV



Thank You

Weacknowledge• UofMichiganRadiologySeedGrant• JeremyNiedbala,Gerrid Rosebushforallhelpinmeasurementsandcalibration

Contact:[email protected]

Joint Dual Photopeak Image Reconstruction in Lu-177 SPECT · 2019-12-17 · Energy Spectrum of...

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