MAE[501] Project

8/3/2019 MAE[501] Project

1/37

[Project: FEAAPPLICATION IN

BIOSTRUCTURES

]

[MAE]

[501]

[INDEPENDENT STUDIES ][ 27thApril

2011]

By:

MandeepSingh


2/37

2|P a g e

Contents1 Introduction................................................................................................................................... 3

2

Problemdefinition

/Problem

statement

......................................................................................

9

3 ResultsandDiscussions............................................................................................................... 10

3.1 DICOMImages:................................................................................................................... 11

3.2 MIMICS:............................................................................................................................... 12

3.3 Meshsmoothening:............................................................................................................ 18

3.4 AssigningMaterial:.............................................................................................................. 21

4

FiniteElement

Analysis

:..............................................................................................................

22

5 Conclusion.................................................................................................................................... 24

6 Appendix...................................................................................................................................... 24

6.1 SolidWorkscapabilitiesforBiostructures............................................................................ 24

6.2 DATAPROCESSING............................................................................................................... 30

7 References................................................................................................................................... 37


3/37

3|P a g e

1 Introduction

Inthe lasttwodecades,there isconsiderablepopularitygainfortheapplicationof

computational mechanics in understanding the complex biostructures. These

techniques provide an efficient feature to simulate the complex structure for the

biomedicalresearchinanethicalway.Thesetechniquesalsohelpinoptimizingand

simulatingtheartificialbodyimplantsandsupportsinbetterdesign.

Thisstudywillfocusonthetechniquesandexposureofthefiniteelementanalysisin

the field for Orthopedics. There has been many advances in the study of

understandingthe

fracture

of

the

bone.

My

study

takes

the

motivation

on

how

we

can apply finite element methods to understand and contribute in the study of

osteoporosis.Forthatpurposewewillstartourstudyfromthescratch,thatis,we

will first understand the basic structure of the Bone. One of the prime reason of

applying the mechanical knowledge to the bio field is to better understand the

phenomenonofnaturedesign.Someoftheimportantfuctionsofboneare:

Support

Motion

Protectionoforgans

Nourishment

SoundTransmission(e.g.themiddleear)

Storageof

minerals

&

chemicals


4/37

4|P a g e

Boneisbasicallyaconnectivetissuethatsupportsthebodyorgans.Ithavetheself

inherentpropertyofrepair ,growandremodel. It ismainlycomprisedofminerals

and protein. Minerals like calcium provide rigidity and at the same time proteins

provideelasticityandstrengthtothestructure.

Thedifferentshapesoftheboneare:

LongBone:Femur

ShortBone:Fingers

Flatbone:Skull

IrregularBone

:Spine

Generally the bone is has compact and rigid structure on the outer surface and

spongy on the interior. This adaption has taken place to lower the weight of the

boneandatthesametimeprovidestiffness.Theinnerportiononthebone,which

isspongycontainsbloodvesselwhichcirculatestheessentialnutrientsandminerals.

The compact bone is also called as cortical bone. The spongy bone is called

Cancellousbone.

Thecompactbonecontainsosteonsthatrunparallelacrossthelengthofthebones.

Theosteonsarecomposedofconcentriccylindricalbonelaminatedovereachwhich

form a structure like cable wire but these are rigid and provides strength to the

structure.Thecentralpartofosteonhaveharversiancanal.

These osteons forms a composite structure. The Periosteum forms the outer

coveringofthebone,whichappearslikeawrappingbindingthebone.

CollagenarethebasicstructuralelementforOsteonwhicharebasicallycomposed

ofprotein.Theseproteinsaretwistedinthegroupofthreeformingahelicalspring

likeshape.


5/37

5|P a g e

HierarchicalStructuresequenceforthecompactboneisgivenbelow:

Apatite(mineralcrystals(200400Long)

Collagenfibers

ConcentricLamella(37m)

Osteon

Bundles

CompactBone


6/37

6|P a g e

CompositionofBone: Osteocytes

Osteoblasts

Osteoclasts

Boneisadynamictissuewherecontinuouschangestakesplaceforremodeling.Old

cells,fracture,bodyadaptionduetoweight,exerciseandothermetabolicactivities

always involve inchanges inbonetissue.Thisdevelopment inthebone isdoneby

theabove

listed

cells

i.e.,

Osteocytes

,Osteoblasts

&

Osteoclasts

.These

cells

are

controlledbyhormonesandMacrophages(Greek:bigeaters,frommakros"large"+

phagein "eat"). In the bone tissue system , Osteoblasts are the those cells which

createscollagenandhydroxyapatite.Someoftheosteoblastsgetcloggedintotheir

own matrix and referred as Osteocytes which are infact accounts as highest

percentage of all cells in the bone tissue. Osteoblasts add calcium to our bones

contrary to the osteoclasts which removes calcium from the bones when needed.

The

minerals

and

chemicals

from

and

to

these

cells

are

transferred

through

the

canals(HaversiansandVolkmanns).

MechanicalBehaviorofSkeletonandMeasuringStraininBones:Nowasweknowthatbonehasthecompositestructurethatmeansitexhibitsallthe

mechanicalpropertiesthatwestudyintheSolidmechanicsliketoughness,stiffness,

rigidity,poissonsratioetc.

Similarlyithavethestressstraincurveswhichreflectsitsmaterialproperties.Ifthe

energysupplied to thebone isgreater than itcanabsorb , the bonewill fracture.


7/37

7|P a g e

TheMotherNaturehasdesignedthebonestructuresoastohaveagoodstrength

whilemaintainingitscompactshape(lessweight).

CorticalBoneisviscoelasticinnature. Itisquitestrongandstiffbutbecomesquite

brittlewhen

strain

rate

increases.

Now we study some features and terminology about Gait analysis and the

parameterthataffectsthegait.Theseanalysishelpsinunderstandingthekinematics

andkineticsofthemotion.Withthesestudieswecancalculatetheforcesactingon

the body. These forces are hence utilized to calculate the forces acting on the

musclesandbonestocalculatethestressesinthetissues(bonesandmuscles).

Forgait

analysis

following

variables

are

important:

1. Time

2. Mass

3. Force

4. Centerofgravity

5. Moments

6. Linearandangularmotion

Now to study the motions we defines anatomical planes to measure the motion

parameters.

Thebodyisdividedintothreeplanes:

1. SagittalPlane

2. CoronalPlane

3. TransversePlane


8/37

8|P a g e

For studying the plane we use some motion definition as defined below. These

termsarerelatestheplanetothebodymotion.

Abduction : It is the motion which brings the body part away from the

sagittalPlane

Adduction:Itisthemotionwhichbringsthebodypartnearertothesagittal

Planeorinotherwordsitistheoppositeofabduction

Flexion : It is the movement in which the joint angle decreases. This

movementgenerallyoccurinsagittalplane.

Extension:It

is

the

movement

to

increase

the

joint

angle.

Thefollowingmethodsareusedtounderstandthegaitmechanics:

Sagittal

plane

Transverse

Plane

Coronal

plane


9/37

9|P a g e

VisualGaitAnalysis:Thisanalysisrequiresconsiderableexperiencesincethe

data is not recorded. This analysis is used to observe movements but not

forces. Micromotion or fast motion cannot be studied through this type of

analysis.

Timing Gait Cycle : This type of analysis bifurcates the motion into small

activities and duration of these submotions are studied under the time to

analyzethemotion.

Direct Motion Measurement Systems : This Analysis is carried out using

electronicequipmentsuchassensors,videorecordingetcwhichhelpin

Electrogoniometers

Electromyography

CombinedKinetic/KinematicSystems

2 Problemdefinition/ProblemstatementIn this project we will be carrying out the study how to analyze the biological

structureusingtheapplicationoffiniteelementmethods.Theprojectwillfocuson

theconductingtheFEAbasedstudyofthefemurboneoveraload.Theprojectlife

cycle starts from how to generate the model for the bone (femur), meshing the

model, assigning the material property and finally applying the loads. The process

looks simple but while transferring the scanned data (cloud points or mesh ) to a

CAD software always includes data loss, hence we have to generate surfaces

matching the profile of the structure. By this project we will incorporate the

difficultiesoccurredwhileconductingsuchprojects.


10/37

10|P a g e

3 ResultsandDiscussions

Applicationof

Finite

Element

Analysis

(FEA)

is

widely

adopted

to

investigate

the

mechanicalbehaviorofthebonestructure(1).

FortheFEAmodel,werequirethe3Dor2Dmodelwhereweapplytheboundary

conditionsandloadingsforstudy.OneoftheMajorApplicationfortheFEAstudy

has been found to the patients suffering with osteoporosis in which with the

helpofmicroCTscanandimageprocessingthesafeloadbearingcapacityofthe

bone

can

be

monitored

and

can

be

advised

to

the

patients.

It

is

has

been

surveyedthat1/3rdofthewomenntheiroldagegetsaffectedbyosteoporosis.

Thisdiseaseisconsideredequallyproneascancer.

FortheFEAbasedstudyofanycomponent,someofthebasicrequirementare

1. Model

2. LoadingsandBoundaryconditions

3. Boneproperties

Image processing is widely used for developing the 3D images of the tissues.

Various imaging devices like Xray, Computer aided Tomographic(CT) images,

ultrasoundareusedextensively forthepurposeofmedicaldiagnosis(3).These

devises are used for diagnosis, measurement (like size of tumor) etc. For our

studyof the femurbone, the3Dmodel for the femurbone isgeneratedusing

theCTscannedslices.Theexampleforsuchslicesisshowninthefigurebelow.


11/37

11|P a g e

Figure1(DicomImagesset)

Now theseCT slices are placed overeach other using and using the softwares

like RHINO, MIMICS we can generate the 3D model of the part we need for

analysis.ThesesoftwaresareextensivelyusedfortheRapidPrototyping.

3.1 DICOMImages:

Digital Imaging and Communications in Medicine (DICOM) images are the

standard format developed for maintaining a common platform for universal

communication among medical imaging vendors and health care IT

organizations. Earlier each manufacturer used proprietary image formats and

communicationswhichmadetheprocesschaoticandfraughtwithdifficultyfor

communicating(4) .Hence DICOM standard was adopted. Hence the CT, MR

scanners generate the images in the form of DICOM. A DICOM data object

consistsofanumberofattributeitemslikenameofthepatient,ID,imagepixel


12/37

12|P a g e

dataetc.whichmakesthedistinguishesevery imageandsothattheimagecan

never be separated from this information by mistake. The National Electrical

ManufacturersAssociation(NEMA)holdsthecopyrighttothisstandard.(5)

3.2 MIMICS:This project utilized the mimics software to develop the 3D model for the

geometry. This software is an image processing software which utilizes the CT

scannedimagestodevelopa3Dmodel.

Firststep isto importthe DICOM,jpeg,bmpsetofCTscanned files.Figure2.

Shows

the

front

,

top,

and

side

view

of

the

imported

model.

Figure2(imagesimportedtomimics)

Nowwecanalsomanagethenumberofimageswewanttouseforgenerating

the model. We can select and skip the images in between. Fig 3 show the CT

imagesselectedforgeneratingthemodelandorganizingtheimages.


13/37

13|P a g e

Figure3(Managingtheimages)

To process the images from these CT images, MIMICS use the gray value as a

thresholdtoseparatethesofttissuefromthehardtissuei.e.,todistinguishthe

thesofttissuesfromthehardones(basicallymusclesfromthebones).

Grey value interpolation is a real 3D interpolation that takes into account the

Partial Volume effect and therefore its more accurate. With the grey value

interpolationmethodweassume that thebonedensitiesgivean indicationon

theamountofbonewithinonepixel.Alledgesofthesurfacearedecidedbased

onthegreyvalues.Alsotheplaceinbetweenthese2pixelsisbasedonthegrey

valuesofthe2pixels.

Theaimofdefiningathresholdistoholdthesegmentationobject(visualizedby

a colored mask) which only contains those pixels of the image with a value

higher than or equal to the threshold value. A low threshold value makes it

possibletoselectthesofttissueofthescannedpatient.Withahighthreshold,

onlytheverydensepartsascorticalbonesremainselected.Inthisproject,soas


14/37

14|P a g e

toanalyzethestructureoffemur,sowechosegrayvalue1364 2637tobethe

threshold(seefigure4).

Thethresholdlimitsoftheresultingmaskareupdatedaccordingtothevaluesof

themasksAandBandtheoperationapplied.:

1. Subtraction(Minus):

Thresholdvalue=ThresholdvaluemaskA

2. Intersection:

lowerthreshold=max(lowmaskA,lowmaskB))

higherthreshold=min(highmaskA,highmaskB))

3. Union:

lowerthreshold=min(lowmaskA,lowmaskB))

higherthreshold=max(highmaskA,highmaskB))

Figure4(ThresholdValue)

Hencethreshold

values

help

us

to

separate

bone

from

the

soft

tissues.

Afterthresholding,weuseregiongrowingtoformaclosedregionwiththesame

threshold.


15/37

15|P a g e

Thenwecangeneratethe3Dmodelbyusingthe3Dcalculatingfunctionofthe

softwareasshowninfigure5.

Figure5(Calculatingthe3D)

Hencethe3DisgeneratedfromtheCTscanasshowninthefigure6below.

Figure6(3DGeneratedasshowninbottomright)

Finallywegeta3Dmodelofthefemurforfurtheroperation.(Noticethatthe3D

modelinthisstageisonlya3Dshellandthereisnodefinedvolumeormeshin


16/37

16|P a g e

it). By erasing and completing the patch work and editing the unwanted

geometriesoneobtaintherequiredfemurbonemodelasshowninthefigure.

Manytimethecontourofthebonescurruptduetothedatalossorerrorindata

transmission.Hence the geometry obtained discontinuities. To correct the

discontinuties,patchingofthecontoursiscarriedout.

Figure7(Imageshowingthenoiseinthe3Dforwhichweneedtodopatchworktocorrectthegeometry)

On the above image we can see the that the model has irregularity in the

geometry.Actuallythegeometryiscalculatedusingthesliceswhichcontainthe

polylinesrunningonthesurfaceboundary.Thesesurfaceboundarypolylinesare

extrudedtoformthe3D.Thesepolylinescanbeeditedtoreformthegeometry

tocorrecttheerror.


17/37

17|P a g e

Figure8(Thefigureshowingthepatchingprocesstocorrectthegeometryusingpolyline)

Aftercorrectingthegeometryweobtainthefollowing(fig.8)geometrywiththe

correctedprofileofthebone.

Figure9(Correctedgeometry)


18/37

18|P a g e

Figure10

(3DgeometryExtractedfromtheimages)

Afterobtaining thegeometry(fig.10)we generate themesh.Most of the time

duetoabruptchanges inthegeometry ,wedontobtainthequalitymeshand

theelementssizeandshapearenotoptimal.Toenhancethequalityofmeshwe

utilizetheremeshingtoolintheMIMICS.

Aftergeneratingsurfacemeshesforthestructure,weneedtoimprovethemesh

quality.Fortheelementsgeneratedautomaticallyarenotoptimalallthetime,

especiallyintheconditionsthatthesurfaceshapechangesseverelyandthesize

of the elements varies rapidly. In this project, the surface mesh generated is

triangleelement,soweneedtoenhancethemeshqualityforthetrianglesinthe

surface. To improve the shape of the triangle elements, we need to consider

boththeshapeandthesizeoftheelements.

3.3 Meshsmoothening:In mesh smoothening process , the interior nodes is moved keeping the

topologicalordersame.Oneoftheefficientsmoothingmethod istheLaplacian


19/37

19|P a g e

algorithm. In this method the interior node is moved to the centroid of the

polygon.Thisprocessisalsocalleddiffusion.

The new position to smoothen the surface by changing the location internal

nodesisgivenby

WhereNisthenumberofneighbouringnodesofi.Themeshsmoothingprocess

usuallyconsistsof35iterations.

Figureshowsthechangeinthelocationofcenternodeforbettershape.

Meshqualitycanalsobeenhancedbytwobasictechniques:

1. NodeElimination

2. DiagonalSwapping


20/37

20|P a g e

Figure11(source:www.mpiinf.mpg.de/~ag4gm/handouts)

Thenewpositionofthe internalnodeforchangingthesharpabruptheights is

givenby

Where is the average to the vectors to the neighboring vertices Q , and P is the

verticesofthecentroidraisedatheightL.

Figure12

Note

that

the

smoothness

does

not

reduce

the

number

of

elements

in

the

mesh. L(P) , which is known as the Umbrella operator which depends on the

numberofiterations isgivenby

)( oldoldnew PPP L+


21/37

21|P a g e

Ifconverges,inthelimitwehave:

Mimics uses this mesh smoothing feature which approximates the complex

geometryandgivessmoothprofileoverforthemeshsurface.

Figure13(Showingsmoothingofthemeshedsurface)

There are many more options to modify the mesh and smoothen the mesh

surfaceinMIMICS(notdisussedhere)

3.4 AssigningMaterial:Inmimicswecanassignthematerialpropertiestothemodelbasedon itsgray

values.Thisgrayvalue inthescandependsonthedensityofthematerial.The

materialpropertiesofthebonesdependonthebonedensity.Inthisprojectwe

utilizedtheexamplegivenintheMIMICStoassigntheboneproperties.

= 13.4 +1017 grayvalue

E=388.8+5925 [6]

( ) PQn

PQn

PLn

i

i

n

i

i == == 11

11

( ) 0)( =PLw


22/37

22|P a g e

Figure14(AssigningMaterialDensity)

Wedividedthefemurinto10differentmaterialgotthemodelasshown inthe

figureabove.

4 FiniteElementAnalysis:In MIMICS , we have the interface of transferring the model to ANSYS

workbench, in which we can import the volume mesh along with the defined

material.ThisprojectutilizedthestaticstructuralanalysismoduleofANSYS.

Inthisprojectasimplepressureloadof100Paisappliedoverthefemoralhead,

withfixed

support

under

the

condyles.


23/37

23|P a g e

Figure15(LoadingandBoundaryconditions)

We observed the maximum stress reaches the bone to be 1464.7Pa, and the

maximumstrainunderthisstressis7.32233e9.Theresultsareshowedbelow

Figure16(Results)


24/37

24|P a g e

5 Conclusion

Bydoingthisproject,weunderstoodthe lifecycleofFEAbasedprojectsandthe

difficultiesthatoccurswhileexecutingtheprojects. Imageprocessingoffersan

ethical way of analyzing the biological structures. The project involves reading

the CT scans, generating the 3D models, assigning the material properties,

meshing and smoothing, and application of finite element analysis. We also

studied the mesh surface enhancementprocess. Wecan see the tensilestress

developedoverthelateralsideofthefemur.

Inthisprojectthereareseverallimitationsthatneedtobeaddressedtomakeit

closertopracticalapplication.Forexamplewetreatedtheboneasasolidmodel,

whichishollowfrominside.Themodelandtheboundaryconditionschosenare

too simple to be rigid fixed at the bottom. In reality the structure boundary

conditions are much more complicated with many ligaments and tendons

attachedtothebone.

6 Appendix6.1 SolidWorkscapabilitiesforBiostructures

Whilecarryingouttheabovestudy,wealsocametoknowaboutthefeaturesof

SolidWorks.SolidWorksalsohavethecapabilityofreadingthecloudpointdata

orthesurfacemeshwhichcanbeutilizedtogeneratethe3Dmodels.Whenever

weexportthedataofthecloudpointorthesurfacemeshtothemodelingsolver

like Solidworks , we face some data loss in the form of surface damage. This

happensbecause

of

the

complicated

shape

of

the

surface.

In

solid

Works

,there

areseveralfeaturestobuildupthesurfaceandcorrectthegeometry.


25/37

25|P a g e

Figure17(Patchfordevelopingthesurface) Figure18(Patchforgeneratingthesurface

matchingtheprofile)

SolidWorks also have the feature of finite element analysis. The geometries

correctedin

SolidWorks

can

also

be

exported

to

advance

tools

for

FEA

like

ANSYS

orAbaqus.WhenweimportthemeshdataorthecloudpointdatainSolidWorks

wegetsharpedgysurfaceasshowninfigure19whichshowsthefemoralhead

surface.

Figure19(MeshoftheFemoralHead)

Forgeneratingasolidstructurethroughthissurfacecloudpointdata,wedefine

severalplanesperpendiculattotheaxisofthebonemodel.


26/37

26|P a g e

Thenthesurface intersectingtheplaneandthemeshcanbeusedtogenerate

theprofileoftheoutersurface.This feature issimilartheslicesoftheCTscan

used in the MIMICS software. The figure 20 below shows the planes and the

profilesgenerated.Thisworkrequiresalotoftimesincetogetabetterprofile,

considerableamountofplanesaregeneratedandequallythenumberofprofiles

generatedoverthesurface.

Figure20(Figureshowingplanesintowhichthebonemeshisdivided)


27/37

27|P a g e

Figure21(Polylinesforgeneratingthesurface)

Thefigure21,aboveshowsthesurfaceprofilegeneratedusingtheintersection

of the mesh cloud point data surface. Now these profiles are connected using

theBoundaryfeatureoftheSolidworkswhichgeneratesurfaceconnectingthe

profile.BelowFigure22,showsthesurfacegenerationovertheprofiles.


28/37

28|P a g e

Figure22(Surfacebeinggenerated)

Figure23(Figureshowingsurfacebeinggenerated)


29/37

29|P a g e

Afterjoining all the surfaces we get the complete geometry of the bone as

shownintheFig24below.

Figure24(Completegeometrygeneratedinsolidworks)

Figure25(Figureshowingthesectionofthebone)


30/37

30|P a g e

Note this geometry can be meshed in the SolidWorks as shown in the figure

beloworitcanbeexportedtoANSYSforfurtheranalysis.

Figure26(MeshedModelwithboundaryconditionapplied)

6.2 DATAPROCESSINGSoftware AnyBody : This software is used for calculating the loadings on the

musculoskeletonelements.Thissoftware isascriptbasedsoftwarewhichhave

thecapabilitiestomodelthebonesandwellasmuscles. ItusestheCplatform

and

inbuilt

graphics.

Using

the

script

commands

we

can

generate

the

model

that

wewanttoanalyze.SomeoftheApplicationsofthissoftwareare

1. Therapy/Medicalrehabilitation

2. ErgonomicDesigninthefieldsofautomotives,sportsetc.


31/37

31|P a g e

3. Functionalperformancestudies

4. Trainingtoolsforsurgeonswhencombinedwithvirtualenvironment

Thissoftwarecontainsgaitanalysisasoneofitsexamplewhichcanbeutilizedto

calculatetheloadingsondifferentpartsofthemusculoskeletan.Thescriptbased

featuresmakesthissoftwarelittletedioustounderstand.

Theinterfaceislookslikeasshowninthefigurebelow:

Figure27(InterfacelookfortheSoftwareAnybody)

Thereareinbuiltscripsformodellingthespecificbonesandmusclesthatmakes

thegraphicworklittleeasier.TheinversedynamicanalysisinAnyBodyStudyisat

the heart of what the AnyBody Modeling System does. An InverseDynamics

operation is like the Kinematics operation, except it is augmented with

calculationofforcesinthesystem,i.e.kineticordynamicanalysis.


32/37

32|P a g e

Inverse dynamics had the advantage that it allows for analysis of very

complicated musculoskeletal systems comprising hundreds of muscles on

desktopor

laptop

computers

in

afew

seconds.

Figure28(FiguretakenfromatutorialinAnybodyModelingSimulationsoftware)

To understand the principal of inverse dynamics, consider the fig 28 shown

above.

Ifweknowthemagnitudeoftheexternalforce,andweknowthelengthofthe

forearmandthe insertionpointofthebicepsmuscleontheforearm,then it is

notdifficulttocomputethemuscleforcefromsimplemomentequilibriumabout

theelbow.

Further

equilibrium

equations

can

subsequently

give

us

the

reaction

forcesintheelbowjoint.

This isreallytheprincipleof inversedynamicsas ittakesplace intheAnyBody

ModelingSystem.Thecomplication iswedonthavejustonemuscle.Henceto

calculate the loadings on such complex structure AnyBody Modeling System

comeshandy.

HereExample

of

Gait

Analysis

was

utilized

to

calculate

the

load

on

the

hip

joint

(loadonthefemoralhead)duringstance.


33/37

33|P a g e

AnyBodyModelingSystemhasthecapabilitiestousecarryoutdataprocessing.

It can read the raw C3D data which contains the raw data for the Gait using

EMG.

TheC3D

specification

expects

physical

measurements

to

be

one

of

two

types,

either positional information (3D coordinates) or numeric data (analog

information).

Each 3D coordinate is stored as a raw X, Y, Z data samples with information

about the sample accuracy (the average error or residual), and camera

contribution(whichcameraswereusedtoproducethedata).

Eachsample

of

numeric

data

can

contain

analog

information

from

sources

such

asEMGandForcePlatesetc.andislinkedtothe3Dsamplessothatitiseasyto

determinethecorrectnumericdatavaluesforany3Dsamplewithinthefile. If

desired (forhighanalog ratesetc.)TheC3D formatcanstoremultiplenumeric

samples per 3D coordinate sample. As a result many C3D files contain both

analogand3Ddatalinkedframebyframewhichisabigimprovementoverthe

OEM formats that store analog and video data separately. Storing related

informationin

asingle

file

gives

agreater

degree

of

confidence

in

the

data

and

makesiteasiertoretrievetherelevantdata[7].

Figure29


34/37

34|P a g e

The C3D data containing the motion data when processed through Anybody

Modeling System, the skeleton gets equipped with markers that carry small

coordinatesystemswithredandgreenarrows.

Theseare

the

marker

points

defined

on

the

human

body,

and

the

red

and

green

arrowsdesignatedirections inwhichthemarkerposition is fixedversus freetobe

optimized.Afreemarkerpositionisonethatisnotwellknownbytheclinician.

TheC3D fileexamplecontainthemotiondataofabodyofweight62kg.Thegait

skeletoncanbeseeninthefollowingfigure

Figure30(FigureshowingtheskeletonmodelanalyzedcomputationallyforthegivenC3Ddataforgaitmotion)

The green arrows designate directions in which we have the greatest uncertainty

aboutwhetherthemarkerisplacedinthemodelasitwasintheexperiment.


35/37

35|P a g e

Thebottomrectangularslabsrepresentthepressureplatewhichwecalculateasa

raw data. The center of pressure can be seen in the figure with blue line. Hence

using the inverse dynamics tools we can calculate the loadings on different

structuralelements.

The following chart is obtained for the reaction on the hip joint. Due to the

restrictionsofusingthisDemousage,wehavenotuseditintheproject.Theabove

explanationisdescribedtomakeawareoftheinbuiltcapabilitiesofthissoftware.

Figure31(PlotshowingthevaryingreactioninthehipJoint)


36/37

36|P a g e

Henceforconductingfiniteelementanalysis,theproject lifecycleforanybiostructurecan

besummerizedasshowninfig32.

Figure32(LifecycleoftheFEAProject)


37/37

7 References1. CinziaZannoni,RaffaellaMantovani,MarcoViceconti,Materialpropertiesassignmentto

finiteelementmodelsofbonestructures:anewmethod,Nov,1998.

2. http://www.efunda.com/formulae/solid_mechanics/mat_mechanics/hooke_orthotropic.cf

m

3. TinkuAcharya,AjoyK.Ray Imageprocessing:principlesandapplications,2005.

4. http://www.mathworks.com/company/newsletters/digest/nov02/dicom.html

5. http://medical.nema.org/

6. W.R.Taylor,E.Roland,H.Ploeg,D.Hertig,R.Klabunde,M.D.Warner,M.C.Hobatho,L.

Rakotomananab,S.E.CliftDeterminationoforthotropicboneelasticconstantsusingFEAand

modalanalysis

7. www.c3d.org

8. EmilyJ.Rayfield,FiniteElementAnalysisandUnderstandingtheBiomechanicsand

EvolutionofLivingandFossilOrganisms

9. http://www.mathworks.com/company/newsletters/digest/nov02/dicom.html

10.HengLiHuang,JuiTingHsu,LihJyhFuh,MingGeneTu,ChingChangKo,YenWenShen

Bonestressandinterfacialslidinganalysisofimplantdesignsonanimmediatelyloaded

maxillaryimplant:Anonlinearfiniteelementstudy

11.ProfRogerLakeswebpage http://silver.neep.wisc.edu/~lakes/

12.ProfHeidiLynnPloegwebpage http://www.engr.wisc.edu/groups/BM/

13.RHuiskes,AsurveyofFiniteElementanalysisinOrthopedicBiomechanics:ThefirstDecade

14.http://www.feppd.org/ICB

Dent/campus/biomechanics_in_dentistry/ldv_data/mech/basic_bone.htm#remodeling

15.http://www.dclunie.com/medicalimagefaq/html/part8.html

16.W.R.Taylora,E.Rolandb,H.Ploegc,D.Hertigc,R.Klabundec,M.D.Warnera,M.C.

Hobathod,L.RakotomananabandS.E.Clift,Determinationoforthotropicboneelastic

constantsusingFEAandmodalanalysis,2002

Date post:	06-Apr-2018
Category:	Documents
Upload:	anonymous-uohuag
View:	217 times
Download:	0 times

MAE[501] Project

Documents