7 July, 2003 AZ/Manchester Knees Meeting 1 AstraZeneca & University of Manchester Knees Project...

7 July, 20037 July, 2003 AZ/Manchester Knees MeetingAZ/Manchester Knees Meeting 11

AstraZeneca & University of AstraZeneca & University of ManchesterManchester

Knees ProjectKnees Project

Project MeetingProject Meeting

ISBE, University of ISBE, University of ManchesterManchester

77thth July 2003 July 2003


BackgroundBackground

Measure cartilage Measure cartilage changes during changes during osteoarthritis osteoarthritis disease disease progressionprogression

LocalisedLocalised Global measures Global measures

insufficientinsufficient Cartilage Volume, Cartilage Volume,

Mean ThicknessMean Thickness Dense set of Dense set of

measuring pointsmeasuring points

Sub-MillimetreSub-Millimetre Combine data from a Combine data from a

population of patientspopulation of patients Cartilage UnstableCartilage Unstable

Use the underlying Use the underlying bone as the frame of bone as the frame of referencereference

CP78 DataCP78 Data 45 Patients at 45 Patients at

Baseline and 6 MonthsBaseline and 6 Months Cartilage and Bone Cartilage and Bone

SegmentationsSegmentations


Statistical Shape Model Statistical Shape Model (SSM)(SSM)

Concise description a set of shapesConcise description a set of shapes Set of points on each exampleSet of points on each example Vectors of how these points vary Vectors of how these points vary

between examplesbetween examples Best Model Best Model Anatomically Anatomically

Corresponding PointsCorresponding Points Means of combining and comparing Means of combining and comparing

individual measurements between individual measurements between any two or more examplesany two or more examples


Statistical Shape ModelStatistical Shape Model

Amy Bone SegmentationsAmy Bone Segmentations Full setFull set Insufficient coverage of bone Insufficient coverage of bone

shaftshaft Lisa Bone SegmentationsLisa Bone Segmentations

Full TP1 but limited TP2Full TP1 but limited TP2 Bone shaft includedBone shaft included

Use Lisa TP1 Bone Use Lisa TP1 Bone SegmentationsSegmentations Register TP1 Bone with TP2 Register TP1 Bone with TP2

CartilageCartilage

50 60 70 80 90 100 110

70

80

90

100

110

120

130

140

150

X

AB121247_a2BFem

Y

50 60 70 80 90 100 110

70

80

90

100

110

120

130

140

150

X

AB121247_l2BFem

Y


Model ConvergenceModel Convergence

Population size Population size 3636

1026 1026 Correspondence Correspondence PointsPoints

Processing time Processing time 10hrs10hrs

0 1000 2000 3000 4000 5000 6000 7000 8000 9000-140.8324

-140.8323

-140.8322

-140.8321

-140.832

-140.8319

-140.8318

-140.8317

-140.8316Objective Value Convergence n=36

Obj

ectiv

e V

alue

Iterations


Corresponding PointsCorresponding Points


Shape ModelShape Model

Mode 1 Mode 2


Visualisation ToolsVisualisation Tools

Interactive examination of the Interactive examination of the corresponding pointscorresponding points

Useful to validate the modelUseful to validate the model


-1 -0.5 0 0.5 1 1.5 2-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

X

Z

Validation using Synthetic Validation using Synthetic ShapeShape

Synthesised Brick and Bump shapeSynthesised Brick and Bump shape Control correspondences’ positionsControl correspondences’ positions Validate automatic 3D shape buildingValidate automatic 3D shape building

Analogous to to moving bump in 2DAnalogous to to moving bump in 2D

-1 -0.5 0 0.5 1 1.5 2-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

X

Z

-1 -0.5 0 0.5 1 1.5 2-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

X

Z

-1 -0.5 0 0.5 1 1.5 2-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

X

Z

-1 -0.5 0 0.5 1 1.5 2-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

X

Z


TibiaTibia


PatellaPatella


Surface ConstructionSurface Construction

Currently using ‘Spans & Ridges’Currently using ‘Spans & Ridges’ Semi-Automated, Robust, Versatile Semi-Automated, Robust, Versatile Reliable thickness measurementsReliable thickness measurements Not continuous or smoothNot continuous or smooth

Smooth surface constructionSmooth surface construction 3D Surface interpolation3D Surface interpolation More accurate cartilage representation More accurate cartilage representation

and thickness measurementsand thickness measurements


Image/Surface Image/Surface RegistrationRegistration

Corrects for Chemical Shift ArtefactCorrects for Chemical Shift Artefact Corrects any movement between Corrects any movement between

successive Bone and Cartilage scanssuccessive Bone and Cartilage scans Deals with inadequate set of TP2 bone Deals with inadequate set of TP2 bone

segmentationssegmentations Register TP1 Bone scan with TP2 Cartilage scanRegister TP1 Bone scan with TP2 Cartilage scan Halves the number of training examplesHalves the number of training examples

Weakest linkWeakest link Approximately 80% successfulApproximately 80% successful


Rigid Image RegistrationRigid Image Registration

Slices 10 to 18 Region of Region of Interest Interest determined by determined by bone bone segmentationsegmentation

Mutual Mutual Information used Information used as quality as quality measure of measure of matchmatch

Steepest descent Steepest descent search algorithmsearch algorithm


Bone and Cartilage Surface Bone and Cartilage Surface RegistrationRegistration

Measure Cortical Bone ThicknessMeasure Cortical Bone Thickness Distance along bone 3D normal to inner Distance along bone 3D normal to inner

cartilage surfacecartilage surface Mean, Standard Deviation and Range give Mean, Standard Deviation and Range give

quality measure of registrationquality measure of registration

MC04MC04TP1TP1Mean: 0.92Mean: 0.92StdDev: StdDev: 0.6890.689

TP2TP2Mean: -0.61Mean: -0.61StdDev: StdDev: 1.7661.766


Bone-Cartilage Bone-Cartilage RegistrationRegistration

Persevere with automatic approachesPersevere with automatic approaches Image Registration 80% successImage Registration 80% success Surface RegistrationSurface Registration distorts Cortical Bone distorts Cortical Bone

thicknessthickness EndPoint Active Shape ModelEndPoint Active Shape Model

Builds model of intensities around TP1 Builds model of intensities around TP1 surfacesurface

Matches model to TP2 imageMatches model to TP2 image Initial tests promisingInitial tests promising

Segment Time point 2 boneSegment Time point 2 bone


Thickness MapsThickness Maps Thickness measured along 3D Thickness measured along 3D

normal to bone surfacenormal to bone surface Measurements at the Corresponding Measurements at the Corresponding

PointsPoints

Bone surface

Cartilage inner surface

Cartilage outer surface

3D Normal to bone surface at correspondence point

Cartilage Thickness

Cartilage Thickness = Cartilage Thickness = distance between distance between intersections of the intersections of the normal with the inner normal with the inner and outer cartilage and outer cartilage surfacessurfaces


Thickness Thickness MeasurementsMeasurements

Choose valid Choose valid correspondence pointscorrespondence points 50% of correspondence with 50% of correspondence with

cartilage presentcartilage present 0 thickness if cartilage not 0 thickness if cartilage not

presentpresent Distance along 3D normal Distance along 3D normal

of bone surface to inner of bone surface to inner and outer cartilage and outer cartilage surfacessurfaces

Measurements Measurements aggregated and aggregated and comparedcompared Average from all examples Average from all examples

including 0 thicknessincluding 0 thickness


Pair-wise Thickness Pair-wise Thickness MapsMaps

Examine changes in thickness in Examine changes in thickness in individual patientsindividual patients

AB121247 Cartilage Thickness TP1 and AB121247 Cartilage Thickness TP1 and TP2TP2


Pair-wise Thickness Pair-wise Thickness MapsMaps

DA030535DA030535

JD190847JD190847

RG271036RG271036

SP190445SP190445


Corresponded Thickness Corresponded Thickness MapsMaps

TP1: 1.768 TP2: 1.753TP2-TP1: -0.0156

(N = 28 Lisa Bone, Amy Cartilage)


Patient DifferencesPatient DifferencesDA030535DA030535

JD190847JD190847

RG271036RG271036

SP190445SP190445


Confidence MeasuresConfidence Measures

Standard Deviation of Standard Deviation of corresponding corresponding differences across differences across populationpopulation

T-Test: mean(TP1)-mean(TP2) / T-Test: mean(TP1)-mean(TP2) / var(TP1)+var(TP2)var(TP1)+var(TP2)


CP78 Work-PlanCP78 Work-Plan

DevelopmenDevelopmentt

1010

Reduced SetReduced Set

3232Full SetFull Set

(45)(45)

FemurFemur July 03July 03

TibiaTibia July 03July 03 Aug 03Aug 03

PatellaPatella Aug 03Aug 03 Aug 03Aug 03

Bones

Set Size


Future WorkFuture Work Improved Image RegistrationImproved Image Registration Statistical AnalysisStatistical Analysis Extend to Tibia and PatellaExtend to Tibia and Patella Amy and Lisa Cartilage SegmentationsAmy and Lisa Cartilage Segmentations Smooth Cartilage and Bone Surfaces Smooth Cartilage and Bone Surfaces Third Party ValidationThird Party Validation ImorphicsImorphics

Incorporation into EndPointIncorporation into EndPoint Automatic Segmentation and AnnotationAutomatic Segmentation and Annotation Extend to other anatomical regionsExtend to other anatomical regions


CP77 Bone CP77 Bone SegmentationSegmentation

Complete set of Bone Complete set of Bone scansscans 5 x 3 + 15 x 1 = 305 x 3 + 15 x 1 = 30 6 man days6 man days

CP77 Bone CP77 Bone SegmentationSegmentation Funding and Funding and

RecruitmentRecruitment Use current resourcesUse current resources

1001LR1L slice 40

50 100 150 200 250

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100

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250

1001LR2L slice 40

50 100 150 200 250

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250


PublicationsPublications Preliminary ResultsPreliminary Results

MIUA Sheffield PosterMIUA Sheffield Poster IPMI Ambleside PosterIPMI Ambleside Poster MICCAI MontrealMICCAI Montreal

CP78 Bone Model Disease ProgressionCP78 Bone Model Disease Progression Method (Image Processing Journal)Method (Image Processing Journal) Results (Medical Journal)Results (Medical Journal)

CP77 Normal RangeCP77 Normal Range


Publication PlanPublication PlanPaperPaper DisclosuresDisclosures TargetTarget DateDate Main Main

AuthorAuthorss

Shape Shape Model Model PreliminaryPreliminary

SSM, Bone SSM, Bone Reference, Reference, Corresponded Corresponded Thickness MapsThickness Maps

Image Image ProcessinProcessing Conf.g Conf.

June June 20032003

ISBEISBE

Normal Normal RangeRange

CP77 normal range CP77 normal range of cartilage of cartilage thickness and thickness and coveragecoverage

Image Image ProcessinProcessing Conf.g Conf.

October October 20032003

ISBEISBE

Shape Shape Model Model MethodMethod

All compartments, All compartments, full population full population thickness maps, thickness maps, statistical analysis statistical analysis

Image Image ProcessinProcessing Journalg Journal

NovembeNovember 2003r 2003

ISBEISBE

OA Disease OA Disease ProgressioProgressionn

Corresponded Corresponded thickness maps, thickness maps, clinical information, clinical information, disease progression.disease progression.

OA/OA/

Medical Medical JournalJournal

NovembeNovember 2003r 2003

AZAZ

7 July, 2003 AZ/Manchester Knees Meeting 1 AstraZeneca & University of Manchester Knees Project...

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