Computerised Image Analysis VT03 5/4/2004

1

Medical Image AnalysisMedical Image Analysis

Computer assisted Image Analysis VT04

Lecture 10 (part 1) Xavier Tizon29 april 2004

Medical Image ProcessingMedical Image Processing•• Medical imaging modalitiesMedical imaging modalities

•• XRayXRay, CT, CT•• UltrasoundUltrasound•• MRIMRI•• PET, SPECTPET, SPECT

•• Generic problems in Medical Image ProcessingGeneric problems in Medical Image Processing•• EnhancementEnhancement•• RegistrationRegistration•• SegmentationSegmentation•• InterpretationInterpretation

•• Visualization of Medical ImagesVisualization of Medical Images•• MPR, MIPMPR, MIP•• Surface and Volume renderingSurface and Volume rendering

Images are Images are acquiredacquired to to getget information information about about AnatomyAnatomy andand PhysiologyPhysiology ofof a patienta patient

US

PET

MRI

CT

1901

1975

2000

Use of XRays Computed Tomography

Computerised Image Analysis VT03 5/4/2004

2

XrayXray –– techniquetechnique PulmonaryPulmonary

MusculoMusculo--skeletalskeletalAngiographyAngiography

AngiographyAngiography MammographyMammography

Computerised Image Analysis VT03 5/4/2004

3

CT CT –– techniquetechnique CT: skeleton CT: skeleton -- neuroneuro

abdominalabdominal

angiographyangiography Ultrasound Imaging

Computerised Image Analysis VT03 5/4/2004

4

Cardiac imaging abdominal

imaging

AngiographyGynecologyObstetrics

GynecologyObstetrics

Positron Emission Tomography : the scanner

Computerised Image Analysis VT03 5/4/2004

5

PET: principlesPET: principles Positron Emission Tomography : production of radioactive products

PET : examples

Scintigraphy (SPECT): imaging device

Nuclear Imaging

Application to thedetection of bone

metastases

Computerised Image Analysis VT03 5/4/2004

6

T1 T2 PDW

MR tomograph

MusculoMusculo--skeletal (joints)skeletal (joints) neurologicalneurological

Multiple sclerosis

angiographyangiography angiographyangiography

Computerised Image Analysis VT03 5/4/2004

7

abdominalabdominalCardiac Cardiac imagingimaging

Functional imagingFunctional imaging Other medical imaging modalitiesOther medical imaging modalities

•• MicroscopyMicroscopy

Generic problems in Generic problems in Medical Image ProcessingMedical Image Processing

•• EnhancementEnhancement•• RegistrationRegistration•• SegmentationSegmentation•• InterpretationInterpretation

EnhancementEnhancement•• Noise (ex. MRI)Noise (ex. MRI)

•• Requires good knowledge of imaging physicsRequires good knowledge of imaging physics•• And a good approximation algorithmAnd a good approximation algorithm

Computerised Image Analysis VT03 5/4/2004

8

EnhancementEnhancement

•• BackgroundBackground•• Ex: MRIEx: MRI•• Field variations Field variations

produce nonproduce non--uniform uniform backgroundbackground

•• Corrected by fitting a Corrected by fitting a lowlow--order polynomial order polynomial to the imageto the image

RegistrationRegistration

•• Registration = matching 2 volumes by applying Registration = matching 2 volumes by applying geometric correction to one of themgeometric correction to one of them

•• The need for registrationThe need for registration•• Study over timeStudy over time•• Fusion of different imaging modalitiesFusion of different imaging modalities•• Matching to an atlasMatching to an atlas•• Organs movementOrgans movement

Magnetic Resonance ImagingMagnetic Resonance Imaging

MRI gives anatomical information

Computed tomographyComputed tomography

CT gives anatomical information

Positron Emission TomographyPositron Emission Tomography

PET gives functional information

Single Photon Emission TomographySingle Photon Emission Tomography

SPECT gives functional information

Computerised Image Analysis VT03 5/4/2004

9

Choose starting par

Transform Study

Evaluate similarity(cost function)

Converged?

Choose newset ofparameters

Reference Study

NoYes

Application: surgeryApplication: surgery Segmentation & interpretationSegmentation & interpretation

•• Segmentation: the need for more sophisticated algorithmsSegmentation: the need for more sophisticated algorithms•• Deformable modelsDeformable models•• WatershedWatershed•• Level set methodsLevel set methods•• Fuzzy connectednessFuzzy connectedness•• ……

•• InterpretationInterpretation•• Labeling from segmentation resultLabeling from segmentation result•• TopTop--down image analysisdown image analysis•• Expert systemsExpert systems

⇒ Bildanalys II

⇒ Artificial Intelligence

Visualization of Medical ImagesVisualization of Medical Images

•• 2D2D•• 3D3D

•• MultiMulti--Planar ReconstructionPlanar Reconstruction•• Maximum Intensity ProjectionMaximum Intensity Projection•• Surface RenderingSurface Rendering•• Volume RenderingVolume Rendering

MultiMulti--Planar ReconstructionPlanar Reconstruction

Computerised Image Analysis VT03 5/4/2004

10

Maximum Intensity ProjectionMaximum Intensity Projection

Shaded Surface Display (SSD)Shaded Surface Display (SSD)

•• Preliminary segmentationPreliminary segmentation•• Voxel set Voxel set ⇒⇒ surface surface

( with for ex. marching cube)( with for ex. marching cube)•• Surface elements rendered according to Surface elements rendered according to

some illumination modelsome illumination model•• Optionally textureOptionally texture

Computerised Image Analysis VT03 5/4/2004

11

Volume RenderingVolume Rendering

•• ReflexionReflexion/transmission properties assigned to /transmission properties assigned to each voxeleach voxel

Volume rendering

Visualization of Computed Tomography volumetric data

Visualization of Ultrasound volumetric data Visualization of « The Visible Human »

Computerised Image Analysis VT03 5/4/2004

12

PerspectivePerspective

•• Fusion Fusion ofof techniques (MR, CT, PET,techniques (MR, CT, PET,……))•• Dual Dual imagingimaging devicesdevices•• Image Image ProcessingProcessing

•• InterventionalInterventional use use ofof MedicalMedical ImagesImages•• RealReal--timetime imagingimaging•• VirtualVirtual surgerysurgery

•• HigherHigher powerpower BUT BUT toughertougher problemsproblems•• IncreaseIncrease ofof computation computation capabilitiescapabilities•• IncreaseIncrease ofof resolutionresolution, , nbnb ofof dimensions, dimensions, physicianphysician’’ss demanddemand

•• CompleteComplete automation automation isis a DREAMa DREAM•• AmountAmount ofof data data tootoo importantimportant•• GoodGood interaction interaction isis more more reliablereliable

Going furtherGoing further

•• Visible Human ProjectVisible Human Project•• http://http://www.nlm.nih.gov/research/visible/visible_human.htmlwww.nlm.nih.gov/research/visible/visible_human.html•• http://visiblehuman.epfl.ch/http://visiblehuman.epfl.ch/

•• LinksLinks•• http://www.comp.leeds.ac.uk/comir/resources/links_c.htmlhttp://www.comp.leeds.ac.uk/comir/resources/links_c.html•• ……

•• Come pay us a visit!Come pay us a visit!

Spiral CT

Whole-body PET

(1-8 min total)

(6-40 min total)

Corrections:• scatter• attenuation

Fused PET/CT

PET

CT

PET/CT scan protocolPET/CT scan protocol

Reconstruction:• FORE + OSEM

CT PET

CT PET