ModernComputationalPhantomsandTheirApplications

JointICRP-RERF-JHPSWorkshopRecentProgressonRadiationDosimetryforEpidemiologyandRadiologicalProtection

Sunday,December2,2017

WesleyBolch,UniversityofFloridaICRPCommittee2

PresentationObjectives

1. Reviewofdifferentphantomformattypes– stylized,voxel,andhybrid2. CurrentseriesofphantomsusedandadoptedbyICRP– adult,pediatric,andpregnantfemale3. Reviewofdifferentphantommorphometriccategories– phantomlibraries&individual-specific4. Exampleapplicationofphantomlibraries– pediatricCTradiationepidemiology5. FuturephantomsfromtheICRP– polygonmeshformats&toolsforvoxel-to-meshconversion

ComputationalAnatomicPhantomsEssentialtoolfororgandoseassessment

n Definition - Computerizedrepresentationofhumananatomyforuseinradiationtransportsimulationofthemedicalimagingorradiationtherapyprocedure

n Needforphantomsvaryacrossareasofradiologicalprotectionn Establishingdosecoefficientsforinternalradiationexposure

n Specificabsorbedfractionsforbothself-doseandcross-dosetointernalorgansarecomputedusingcomputationalphantoms.TheseSAFvaluesarethenused,alongwithbiokineticmodelsandradionuclidedecayschemes,tocomputedosecoefficients- organequivalentdoseoreffectivedoseperactivityingestedorinhaled

n Establishingdosecoefficientsforexternalradiationexposuren Eitheroccupationalorenvironmentalfieldsofradiationorradionuclideemissions

n Computingorgandosesinradiologicalaccidents– retrospectively/prospectively

ComputationalAnatomicPhantomsEssentialtoolfororgandoseassessment

n Definition - Computerizedrepresentationofhumananatomyforuseinradiationtransportsimulationofthemedicalimagingorradiationtherapyprocedure

n Needforphantomsvarywiththemedicalapplicationn NuclearMedicine

n 3Dpatientimagesgenerallynotavailable,especiallyforchildren

n Diagnosticradiologyandinterventionalfluoroscopyn No3Dimage

n Computedtomographyn 3Dpatientimagesavailable,problem– organsegmentationn Noanatomicinformationatedgesofscancoverage

n Radiotherapyn Neededforcharacterizingout-of-fieldorgandoses

n Examples– IMRTscatter,protontherapyneutrondose

Computational Anatomic PhantomsPhantom Types and Morphometric Categories

n PhantomFormatTypesð Stylized(ormathematical)phantoms

ð Voxel(ortomographic)phantoms

ð Hybrid(orNURBS/PM)phantoms

Stylized(mathematical)phantomsFlexiblebutanatomicallyunrealistic

Voxel(tomographic)phantomsAnatomicallyrealisticbutnotveryflexible

Hybrid(NURBS/PolygonMesh)phantomsBothanatomicallyrealisticandflexible

SegmentationPolygonization

NURBSmodeling Voxelization

SegmentpatientCTimagesusing3D-DOCTORTM

Convertintopolygonmeshusing3D-DOCTORTM

MakeNURBSmodelfrom

polygonmeshusing

RhinocerosTM

ConvertNURBSmodelintovoxelmodelusingMATLABcodeVoxelizer

ExampleoftheprocessusedattheUniversityofFlorida

Voxelizer Algorithm - See Phys Med Biol 52 (12) 3309-3333 (2007)

HybridPhantomConstruction

ComputationalAnatomicPhantomsPhantomTypesandCategories

n PhantomFormatTypesð Stylized(ormathematical)phantoms

ð Voxel(ortomographic)phantoms

ð Hybrid(orNURBS/PM)phantoms

n PhantomMorphometricCategoriesð Reference(50th percentileindividual,patientmatchingbyageonly)

ð Patient-dependent(patientmatchedbynearestheight/weight)

ð Patient-sculpted(patientmatchedtoheight,weight,andbodycontour)

ð Patient-specific(phantomuniquelymatchingpatientmorphometry)

MorphometricCategories– ReferencePhantoms

ReferenceIndividual- AnidealisedmaleorfemalewithcharacteristicsdefinedbytheICRPforthepurposeofradiologicalprotection,andwiththeanatomicalandphysiologicalcharacteristicsdefinedinICRPPublication89(ICRP2002).

Note– Whileorgansize/massarespecified inanICRPreferencephantom,organshape,depth,positionwithinthebodyarenotdefined byreferencevalues

ReferencePhantomsUsedbytheICRPUntilveryrecently,alldosecoefficientspublishedbytheICRPwerebasedoncomputationaldatageneratedusingtheORNLstylizedphantomseries.

ORNLTM-8381Cristy&Eckerman

PublicationsfromICRPusingthePublication110Phantoms• ICRPPublication116– ExternalDoseCoefficients(2010)• ICRUReport84– CosmicRadiationExposuretoAircrew(2010)• ICRPPublication123– AssessmentofRadiationExposureofAstronautsinSpace(2013)

ReferencePhantomsAdoptedbytheICRP

ICRPPublication110– AdultReferenceComputationalPhantoms

PublicationsfromICRPusingthePublication110Phantoms• Publication133- Referencespecificabsorbedfractions(SAF)forinternaldosimetry• Publication130Series- Dosecoefficientsforradionuclideinternaldosimetryfollowinginhalation/ingestion

ReferencePhantomsAdoptedbytheICRPICRPsupcomingreferencephantomsforpediatricindividualsarebasedupontheUF/NCIseriesofhybridphantoms

CurrentPublicationsUnderDevelopmentinICRPCommittee2UsingPediatricPhantoms

TaskGroup90DoseCoefficientsforEnvironmentalExternalExposures

TaskGroup95DoseCoefficientsforEnvironmentalInternalExposures

TaskGroup96SpecificAbsorbedFractionsforInternalExposures

ICRPSeriesofReferenceFetalModels

ICRPSeriesofReferencePregnantFemaleModels

Definition-Expandedlibraryofreferencephantomscoveringarangeofheight/weightpercentiles

NHANES Database7320 individuals

AgeWeightStanding heightSitting heightBMIBiacromial breadthBiiliac breadthArm circumferenceWaist circumferenceButtocks circumferenceThigh circumference

ICRP - based UFHADM

US based phantom library10% 25% 50% 75% 90%

Reference weights @ 1 or more fixed anthropometric parameter(s)NHANES - based

UFHADM

MorphometricCategories– PatientDependentPhantoms

Patient-DependentHybridPhantoms– UFSeries

Geyeretal.– PhysMedBiol(2014)

MorphometricCategories– PatientDependentPhantoms

UF/NCIPhantomLibrary- Children

Phantomforeachheight/weightcombinationfurthermatchingaveragevaluesofbodycircumferencefromCDCsurveydata

85pediatricmales73pediatricfemales

UF/NCIPhantomLibrary- Adults

Phantomforeachheight/weightcombinationfurthermatchingaveragevaluesofbodycircumferencefromCDCsurveydata

100adultmales93adultfemales

ArticlefromBrenneretal.2001whichchangedCTimagingpracticeworldwide

RESULTS.Thelargerdosesandincreasedlifetimeradiationrisksinchildrenproduceasharpincrease,relativetoadults,inestimatedriskfromCT.EstimatedlifetimecancermortalityrisksattributabletotheradiationexposurefromaCTina1-year-oldare0.18%(abdominal)and0.07%(head)—anorderofmagnitudehigherthanforadults—althoughthosefiguresstillrepresentasmallincreaseincancermortalityoverthenaturalbackgroundrate.IntheUnitedStates,ofapproximately600,000abdominalandheadCTexaminationsannuallyperformedinchildrenundertheageof15years,aroughestimateisthat500oftheseindividualsmightultimatelydiefromcancerattributabletotheCTradiation.

Simplisticmethodsoforgandose

ResponsestoBrennerArticle:• Developmentofprofessionalsocietyalliances– ImageGently,StepLightly,GowiththeGuidelines• Developmentofsize-specificandstandardizedimagingprotocols• Developmentofnewtechnologies

• TubecurrentmodulationinCT• Improveddetectortechniques• Improvedimagereconstructionalgorithms

Distinctionbetween…Riskprojection – organdoseestimatescoupledwithexistingcancerriskmodelsRiskassessment– directmeasureofcancerriskthroughepidemiologystudies

UseofCTscansinchildrentodelivercumulativedosesofabout50mGymightalmosttripletheriskofleukaemia anddosesofabout60mGymighttripletheriskofbraincancer.Becausethesecancersarerelativelyrare,thecumulativeabsoluterisksaresmall:inthe10yearsafterthefirstscanforpatientsyoungerthan10years,oneexcesscaseofleukaemia andoneexcesscaseofbraintumour per10000headCTscansisestimatedtooccur.Nevertheless,althoughclinicalbenefi tsshouldoutweighthesmallabsoluterisks,radiationdosesfromCTscansoughttobekeptaslowaspossibleandalternativeprocedures,whichdonotinvolveionising radiation,shouldbeconsideredifappropriate.

TheincreasedincidenceofcancerafterCTscanexposureinthiscohortwasmostlyduetoirradiation.Becausethecancerexcesswasstillcontinuingattheendoffollow-up,theeventuallifetimeriskfromCTscanscannotyetbedetermined.RadiationdosesfromcontemporaryCT scans are likely to be lower than those in 1985-2005, but someincreaseincancerriskisstilllikelyfromcurrentscans.FutureCTscansshouldbelimitedtosituationswherethereisadefiniteclinicalindication,witheveryscanoptimised toprovideadiagnosticCTimageatthelowestpossibleradiationdose.

RiskofPediatricandAdolescentCancerAssociatedwithMedicalImagingR01CA185687

The use of medical imaging that delivers ionizing radiation is high in the United States. The potentialharmful effects of this imaging must be understood so they can be weighed against its diagnosticbenefits, and this is especially critical for our vulnerable populations of children and pregnant women.The proposed study will comprehensively evaluate patterns of medical imaging, cumulative exposureto radiation, and subsequent risk of pediatric cancers in four integrated health care delivery systemscomprising over 7 million enrolled patients enrolled from 1996-2017.

ProjectManagementUniversityofCalifornia,SanFrancisco(UCSF)

BiostatisticsandEpidemiologyUniversityofCalifornia,Davis(UCD)

OrganDoseAssessmentUniversityofFlorida(UF)

PatientEnrollmentSitesKaiserPermanenteNorthernCalifornia(KPNC)KaiserPermanenteNorthWest(KPNW)KaiserPermanenteHawaii(KPHI)KaiserPermanenteWashington(KPWA)MarshfieldClinicResearchInstitute(MCRI)PediatricOncologyGroupofOntario(POGO)GeisingerHealthSystems(GE)HarvardPilgrimHealthPlan(HP)

Aim1:ImagingUtilizationPatternsAim1A– PatternsofimagingutilizationinpregnantwomenAim1B– PatternsofimagingutilizationinchildrenAim1C– Patternsofimagingutilizationinadultsandchildren

Aim2:OrganDoseandAssociationwithCancerOutcomesAim2A– Imaginginpregnantwomen andchildhoodcancerriskAim2B– Imaginginchildren andchildhoodleukemiariskAim2C– Imaginginpregnantwomenandchildren andchildhoodcancerrisk

RiskofPediatricandAdolescentCancerAssociatedwithMedicalImagingR01CA185687

1.OrganDoseReconstructioninComputedTomography

CTProcedureDetailsYearofscanScan#incurrentyearSeries#incurrentscanBodypartimagedMedicalfacilityCTscannermanufacturerCTscannermodel

PatientDataStudyIDAgeGenderHeightWeightEffectivediameteratcenterslice(cm)

PregnantFemalesGestationalage

CTTechniqueFactorsScanlength(cm)Beamcollimation(mm)Beamenergy(kVp)PitchCTDIvol(mGy)DLP(mGy-cm)FixedormodulatedmAExamAveragedmAs

DataCollection– 2006to2017 RadimetricsDataCollection– 1996to2006 DataAbstraction

𝑁𝐹𝐸,𝐶(𝑝ℎ𝑜𝑡𝑜𝑛𝑠𝑚𝐴𝑠 ) =

𝐴𝑖𝑟𝐾𝑒𝑟𝑚𝑎𝑚𝑒𝑎𝑠𝑢𝑟𝑒𝑑 (𝑚𝐺𝑦𝑚𝐴𝑠)

𝐴𝑖𝑟𝐾𝑒𝑟𝑚𝑎𝑠𝑖𝑚𝑢𝑙𝑎𝑡𝑒𝑑 (𝑚𝐺𝑦𝑝ℎ𝑜𝑡𝑜𝑛)

1

𝑂𝑟𝑔𝑎𝑛𝐷𝑜𝑠𝑒 +𝑚𝐺𝑦𝑚𝐴𝑠0

= 2 3 𝑂𝑟𝑔𝑎𝑛𝐷𝑜𝑠𝑒𝑖 +𝑚𝐺𝑦𝑝ℎ𝑜𝑡𝑜𝑛0

𝑧𝑒𝑥𝑎𝑚 𝑒𝑛𝑑

𝑖=𝑍𝑒𝑥𝑎𝑚 𝑠𝑡𝑎𝑟𝑡

< × 𝑁𝐹𝐸,𝐶 +𝑝ℎ𝑜𝑡𝑜𝑛𝑠𝑚𝐴𝑠 01

𝑊𝐹(𝑧) = 𝐴𝑉𝑎𝑣𝑒𝑟 𝑎𝑔𝑒 (𝑧)

∑ 𝐴𝑉𝑎𝑣𝑒𝑟𝑎𝑔𝑒 ,𝑖𝑍𝑒𝑥𝑎𝑚 𝑒𝑛𝑑𝑖=𝑍𝑒𝑥𝑎𝑚 𝑠𝑡𝑎𝑟𝑡

1

𝐸𝑓𝑓𝑒𝑐𝑡𝑖𝑣𝑒𝑚𝐴𝑠 =(𝐸𝑥𝑎𝑚𝐴𝑣𝑒𝑟𝑎𝑔𝑒𝑚𝐴) × 𝑅𝑜𝑡𝑎𝑡𝑖𝑜𝑛𝑇𝑖𝑚𝑒(𝑠)

𝐸𝑥𝑎𝑚𝑃𝑖𝑡𝑐ℎ1

𝑂𝑟𝑔𝑎𝑛𝐷𝑜𝑠𝑒(𝑚𝐺𝑦) = 12 𝑂𝑟𝑔𝑎𝑛𝐷𝑜𝑠𝑒𝑖 4𝑚𝐺𝑦𝑚𝐴𝑠

6 ×𝑊𝐹𝑖𝑍𝑒𝑥𝑎𝑚 𝑒𝑛𝑑

𝑖=𝑍𝑒𝑥𝑎𝑚 𝑠𝑡𝑎𝑟𝑡

> × 𝐸𝑓𝑓𝑒𝑐𝑡𝑖𝑣𝑒𝑚𝐴𝑠1

CTcomputationalmethodology– FixedTubeCurrent

CTcomputationalmethodology– ModulatedTubeCurrent

SixMethodsofPatient-to-PhantomMatchingforCTOrganDosimetry

1. PatientAge/GenderOnly UF/NCIReferencePhantom2. HeightandWeight UF/NCILibraryPhantom

3. EffectiveDiameter– ScanAveraged UF/NCILibraryPhantom4. EffectiveDiameter– CenterSlice UF/NCILibraryPhantom

5. WaterEquivalentDiameter– ScanAveraged UF/NCILibraryPhantom6. WaterEquivalentDiameter– CenterSlice UF/NCILibraryPhantom

𝐸𝑓𝑓𝑒𝑐𝑡𝑖𝑣𝑒𝐷𝑖𝑎𝑚𝑒𝑡𝑒𝑟(𝑐𝑚) =0𝐷𝑖𝑎𝑚𝑒𝑡𝑒𝑟𝐿𝑎𝑡𝑒𝑟𝑎𝑙 (𝑐𝑚) × 𝐷𝑖𝑎𝑚𝑒𝑡𝑒𝑟𝐴𝑃(𝑐𝑚)1

𝑊𝑎𝑡𝑒𝑟𝐸𝑞𝑢𝑖𝑣𝑎𝑙𝑒𝑛𝑡𝐷𝑖𝑎𝑚𝑒𝑡𝑒𝑟(𝑐𝑚) = 2561

1000𝐶𝑇(𝑥, 𝑦)𝑅𝑂𝐼AAAAAAAAAAAAAAA + 1C

𝐴𝑅𝑂𝐼(𝑐𝑚2)𝜋

1

𝐶𝑇(𝑥, 𝑦) = *𝜇(𝑥, 𝑦) − 𝜇𝑤𝑎𝑡𝑒𝑟

𝜇𝑤𝑎𝑡 𝑒𝑟2 × 10001 𝜇" = 𝜌 ×'(')𝑤𝑖 ,

𝜇𝜌-𝑖,𝑗𝑝𝑗 1

𝑁𝑒

𝑗

4𝑁𝑐

𝑖

1

AAPMTaskGroup204

AAPMTaskGroup220

BoxplotscomparingorgandosepercentdifferenceforeachofthesixmatchingparametersbasedonCDCBMIclassificationsforpediatricpatients.Theverticallinesextendatmost1.5timestheinterquartilerange.

2.OrganDoseReconstructioninDiagnosticFluoroscopy

FluoroscopyProcedureDetailsProceduretype(1to6)CumulativefluoroscopytimeCumulativereferenceairkermaCumulativekerma-areaproduct

PatientDataStudyIDAgeGenderHeightWeight

ReferenceFluoroscopyExams1.UpperGastrointestinalSeries(UGI)2.UpperGastrointestinalSerieswithFollow-Through(UGI-FT)3.VoidingCystourethrogram(VCUG)4.RehabilitationSwallow(RS)5.LowerGastrointestinalSeries/BariumEnema(LGI)6.GastrostomyTubePlacement(G-Tube)

DataCollection– 2006to2017 RadimetricsDataCollection– 1996to2006 DataAbstraction

Problem – nearlyalldiagnosticfluoroscopysystemscannotgenerateRDSRsSolution – create“reference”diagnosticexamsandscaledosesbyFT,RAK,KAP

DiagnosticFluoroscopyProcedureOutlines- UF

ProcedureDuration:120secondsVCUG

IodineContrast

3.OrganDoseReconstructioninDiagnosticNuclearMedicine

NMProcedureDetailsProceduretype(1to6)AdministeredActivity

PatientDataStudyIDAgeGenderHeightWeight

ReferenceNMProcedures1.Tc-99mDMSA2.Tc-99mMDP3.Tc-99mMAG34.F-18FDG5.Tc-99mSulfurColloid6.I-123MIBG

DataCollection– 2006to2017 RadimetricsDataCollection– 1996to2006 DataAbstraction

Problem – InjectedactivitymightnotbeavailableSolution – Usecurrentguidelinesorperiod-specificweight-baseddosingschemes

Biokinetics – AssumeICRPreferencemodelsRadionuclideSvalues– AssumevaluesfromtheUFreferencephantoms

Committee2TaskGroup103

MRCPs (Mesh-typeReferenceComputationalPhantoms)

VRCPs (Voxel-typeReferenceComputationalPhantoms)

(ICRPPublication110)FigurecourtesyofCHKim– TG103Chair

10-1 100 101 102 103 104 105 106100

101

102

103

104

105

106

Helium MRCP Voxelized MRCP (0.6) Voxelized MRCP (1.0) Voxelized MRCP (2.0) Voxelized MRCP (4.0) ICRP-110 Phantom

Com

puta

tion

spee

d(p

artic

les/

seco

nd)

Energy (MeV/u)

MRCP

10-3 10-2 10-1 100 101 102 103 104 105100

101

102

103

104

105

106

Electron MRCP Voxelized MRCP (0.6) Voxelized MRCP (1.0) Voxelized MRCP (2.0) Voxelized MRCP (4.0) ICRP-110 Phantom

Com

puta

tion

spee

d(p

artic

les/

seco

nd)

Energy (MeV)

MRCP

10-8 10-6 10-4 10-2 100 102 104100

101

102

103

104

105

106

Neutron

Com

puta

tion

spee

d(p

artic

les/

seco

nd)

MRCP Voxelized MRCP (0.6) Voxelized MRCP (1.0) Voxelized MRCP (2.0) Voxelized MRCP (4.0) ICRP-110 Phantom

Energy (MeV)

MRCP

10-3 10-2 10-1 100 101 102 103 104 105100

101

102

103

104

105

106

Photon

Com

puta

tion

spee

d(p

artic

les/

seco

nd)

MRCP Voxelized MRCP (0.6) Voxelized MRCP (1.0) Voxelized MRCP (2.0) Voxelized MRCP (4.0) ICRP-110 Phantom

Energy (MeV)

MRCP

ComputationSpeed- PHITS

FigurecourtesyofCHKim– TG103Chair

10-6

10-5

10-4

10-3

10-2

10-1

100

101

10-6

10-5

10-4

10-3

10-2

10-1

100

101

10-6

10-5

10-4

10-3

10-2

10-1

100

101

10-2 10-1 100 10110-6

10-5

10-4

10-3

10-2

10-1

100

101

10-2 10-1 100 101 10-2 10-1 100 101

Publication 133 data Mesh phantom-AF (Geant4) Voxel phantom-AF (Geant4)

Publication 133 data Mesh phantom-AM (Geant4) Voxel phantom-AM (Geant4)

Photon Energy (MeV)

Lungs

Spec

ific

Abso

rbed

Fra

ctio

n (k

g-1)

AM

Source: Lungs

RBM Stomach

Heart Liver Spleen

Lungs

AF

RBM Stomach

Heart Liver Spleen

10-1

100

101

102

103

104

10-1

100

101

102

103

104

10-9 10-7 10-5 10-3 10-1 101 10310-1

100

101

102

103

104

10-9 10-7 10-5 10-3 10-1 101 103

AP

Publication 116 data Mesh phantom (Geant4) Voxel phantom (Geant4) Mesh phantom (PHITS)

PA

LL

Effe

ctiv

e D

ose

per F

luen

ce (p

Sv c

m2 )

RL

ROT

Neutron Energy (MeV)

Effective Dose - Neutron

ISO

ImportantConclusion–

UseofMesh-TypePhantomsDoseNotAlterInAnyMeaningfulWayDoseCoefficientsPreviouslyPublishedbyICRP

n Successfulconversionofvoxelphantomtosurfacemeshedphantomwithuniquevertices

n SurfacemeshreadyforTetgenTM togeneratetetrahedralmesh

n JointcollaborationbetweenUFandJAEA(manuscriptinpreparation)

Recently Developed Voxel to TM Algorithm

Thankyouforyourattention!