InternationalSocietyforMagneticResonanceinMedicine(ISMRM),The24th
AnnualMeetingandExhibition,Singapore,7-13May2016.
DevelopmentofanAutomatedShapeandTexturalSoftwareModelofthe
PaediatricKneeforEstimationofSkeletalAge.
CaronParsons1,2,CharlesHutchinson1,2,EmmaHelm2,AlexanderClarke3,Asfand
BaigMirza3,QiangZhang4andAbhirBhalerao4.
1DivisionofHealthSciences,UniversityofWarwick,Coventry,UnitedKingdom,
2DepartmentofRadiology,UniversityHospital
Coventry&Warwickshire,Coventry,UnitedKingdom,3WarwickMedicalSchool,
Coventry,UnitedKingdom,4Departmentof
ComputerSciences,UniversityofWarwick,Coventry,UnitedKingdom
Synopsis:
Therearemultiplemethodsavailableforskeletalagedeterminationinthe
paediatricendocrinepopulation.Onlytwomethods,usinglefthandandwristxraysareinfrequentclinicaluse,howeverGreulich&Pyleisbasedondata
collatedbetween1931and1942andTannerWhitehouseusesdatafromasfar
backas1949.Wepresenttheinitialresultsofanautomatedsoftwaremodelof
shapeandtexturalanalysisoftheepiphysesoftheknee.
Introduction
Disordersofgrowthandmetabolismareasignificantpublichealthproblem,
responsibleforthemajorityofpaediatricendocrinologyreferralsanda
significantnumberofconsultationswithgeneralpractitioners.Correlationof
skeletalage(SA)andchronologicalage(CA)alongsideotherclinicalfindingsis
keytothediagnosisandmanagementofmanyendocrineconditions,including
pubertydisordersandshortstature.Thesechildrenoftenundergoserialx-rays
duringtheirperiodoftreatmenttoassessboneage.RecentstudiesofJapanese
[1]andItalian[2]childrenexaminedthepotentialofmagneticresonanceimages
(MRI)oftheleftwristforskeletalageestimation,demonstratingcorrelation(R2
>0.9)betweenCAandSA.
OthermethodsofSAdeterminationincludeevaluationofkneex-rays[3],digital
atlasesofthewrist[4]andautomatedsoftwaremodelsofwristx-rays[5],
howevertoourknowledgetherehasnotbeenanyevaluationofthetexturaland
shapechangeattheepiphysisonMRI.
Duringtheearlierstagesofgrowthwhencorrectiveproceduresareunder
consideration,theepiphysisisnotfullyossifiedandthereforeawealthof
informationismissingfromanx-ray.Theshapeandtexturalfeaturesofan
epiphysisonMRIshouldgeneratemoreinformation,potentiallyallowingfor
moreaccurateageestimation.
Purpose
1)TotrainandtestasoftwaremodelofMRIkneephysisshapeandtexturefor
estimationofSA.
2)Tocomparethemodel'sSAestimationwithCA.
InternationalSocietyforMagneticResonanceinMedicine(ISMRM),The24th
AnnualMeetingandExhibition,Singapore,7-13May2016.
Methods:
AretrospectivereviewofallpaediatricMRIsofthekneeperformedatUniversity
HospitalCoventry&Warwickshireidentified143patientsontheradiology
informationsystembetween18/08/2010and10/08/2015.4caseswere
excludedduetosynovialabnormalityorarthropathyand6wereexcludeddueto
movementartefactorinadequatesequences.
Theimageanalysisconsistedofthreestages:(1)expertmark-upoftraining
imagestobuildtheshapeandappearancemodelsofvariation[6];(2)validation
oftheaccuracyofthemodelsusingleave-one-outtestingonthetraining
samples;(3)regressionofshapeandtextureco-factorsfromtrainingsamplesto
CA.
Duringstage(1)weusedproton-densityandfatsaturationsequencesto
produceaccuratesurfacedelineationsoftheepiphyses.Thepointdatawere
convertedtoasurfacemesh,co-registeredandthesurfacesre-sampledwitha
smallersub-setofcorrespondingpointsatwhichappearancedatawasextracted.
Atstage(2),wepartitionedthetrainingdataandusedcross-validationtestingto
verifytheaccuracyoftheshapeandappearancemodelfitting.Inaddition,the
modelcharacterisedthetexturalchangesacrosstheepiphysealplateandthis
wasusedtoproduceanmodelofnormalage-relatedchangebyusing
multivariate,non-linearregressiontoCA.Thiswascarriedoutbymeansofa
neuralnetworkclassifier[7].
Results:
Chronologicalagerangedbetween4.99and18.4years,ofwhich43.4%were
male.Overallroot-mean-squareerror(RMSE)was592days(1.62years)andthe
averageabsoluteagepredictionerrorwas457days(1.25years).Regressionof
theappearanceandshapefactorstoCAshowedmoderatecorrelation(R2=
0.634)(fig2).Analysisofthedegreeoferrorbyagegroupdemonstrateda
highermeanerrorinthegroupswithsmallersamples(fig3).
Discussion:
SAdeterminationisanimportanttoolinpaediatricendocrinology,but
assessmentstillreliesonout-datedatlases[8,9]andthereaderreliabilityofthe
interpreter,withintra-observerdifferencesofupto0.96years[10].Thereare
differencesinSAversusCAthatexistwithindifferentpopulationssuchasethnic
background[11]andobesity[12].
Thisworkrepresentsafirststepinthedevelopmentofanautomatedsoftware
modelforSAdeterminationusingkneeMRI.Despitethesmallsamplesize,the
averageagepredictionerrorof1.25yearslieswithinthe95%confidence
intervalsofreportedintra-observererrorbasedonboththeTW2andGPatlases
[10],howeverrelativelyhighagepredictionerrorsoccurredwheretherewere
smallernumberswithinanagegroup.
InternationalSocietyforMagneticResonanceinMedicine(ISMRM),The24th
AnnualMeetingandExhibition,Singapore,7-13May2016.
Conclusion:
Wepresenttheinitialresultsofanautomatedsoftwaremodelofshapeand
texturalanalysisoftheepiphysesonkneeMRIwithameanagepredictionof
1.25years.Furthernormativedataisneededtorefinethesoftwaremodel.,so
thatitcanbeusedforpredictionofepiphysealfusionandskeletalage
determination.
Bibliography
1.
Terada,Y.,etal.,Skeletalageassessmentinchildrenusinganopencompact
MRIsystem.MagnResonMed,2013.69(6):p.1697-702.
2.
Tomei,E.,etal.,ValueofMRIofthehandandthewristinevaluationof
boneage:Preliminaryresults.JournalofMagneticResonanceImaging,
2014.39(5):p.1198-1205.
3.
O'Connor,J.E.,etal.,Amethodtoestablishtherelationshipbetween
chronologicalageandstageofunionfromradiographicassessmentof
epiphysealfusionattheknee:anIrishpopulationstudy.JAnat,2008.
212(2):p.198-209.
4.
Gilsanz,V.andO.Ratib,HandBoneAge.2nded.2011:Springer.
5.
Thodberg,H.H.,etal.,TheBoneXpertmethodforautomateddetermination
ofskeletalmaturity.IEEETransMedImaging,2009.28(1):p.52-66.
6.
Cootes,T.F.,G.J.Edwards,andC.J.Taylor,Activeappearancemodels,in
ComputerVision—ECCV’98,H.BurkhardtandB.Neumann,Editors.1998,
SpringerBerlinHeidelberg.p.484-498.
7.
Duda,R.O.,P.E.Hart,andD.G.Stork,PatternClassification(2ndEdition).
2000:Wiley-Interscience.
8.
Greulich,W.andP.Pyle,Radiographicatlasofskeletaldevelopmentofthe
handandwrist..2nded.1959,Stanford:StanfordUniversityPress.
9.
TannerJM,W.R.,CameronN,MarshallWA,HealyMJr,GoldsteinH
Assessmentofskeletalmaturityandpredictionofadultheight(TW2
method).1983,London:AcademicPress.
10. King,D.G.,etal.,Reproducibilityofboneageswhenperformedbyradiology
registrars:anauditofTannerandWhitehouseIIversusGreulichandPyle
methods.BrJRadiol,1994.67(801):p.848-51.
11. Mora,S.,etal.,SkeletalagedeterminationsinchildrenofEuropeanand
Africandescent:applicabilityoftheGreulichandPylestandards.Pediatr
Res,2001.50(5):p.624-8.
12. Johnson,W.,etal.,Patternsoflineargrowthandskeletalmaturationfrom
birthto18yearsofageinoverweightyoungadults.IntJObes(Lond),
2012.36(4):p.535-41.
InternationalSocietyforMagneticResonanceinMedicine(ISMRM),The24th
AnnualMeetingandExhibition,Singapore,7-13May2016.
InternationalSocietyforMagneticResonanceinMedicine(ISMRM),The24th
AnnualMeetingandExhibition,Singapore,7-13May2016.