Imaging
description
Transcript of Imaging
ImagingImaging
PETPET
Course LayoutCourse LayoutClassDateClass + Content
I23.2.2005Physical Principles of PET
II2.3.2005Physical principles of MRI
III9.3.2005Imaging applications
IV16.3.2005Image Reconstruction PET and MRI
V23.3.2005Automatic Image Alignment
VI30.3.2005PCA
VII6.4.2005No Class
VIII13.4.2005GLM
IX4.5.2005GLM relation to classical tests (Anova, T-test..)
X18.5.2005Covariates
XI25.5.2005Gaussian fields Theory
XII1.6.2005Specific experiment design and analysis
XIII8.6.2005Specific experiment design and analysis
XIV15.6.2005Correction for multiple measurements
Talk LayoutTalk Layout Repetition of PET princinplesRepetition of PET princinples PET image reconstruction -FBPPET image reconstruction -FBP Physics of NMRPhysics of NMR Application to imaging of NMR -MRIApplication to imaging of NMR -MRI
PETPET
Positron emissionPositron emission
PETPET
Coincidence EventsCoincidence Events
1
1. Detected True Coincidence Event
2
2. True Event Lost to Sensitivity or Deadtime
3
3. True Event Lost to Photon Attenuation
4
4. Scattered Coincidence Event
5a 5b
5a,b. Random Coincidence Event
Attenuation CorrectionAttenuation Correction
0 0
( ') ' ( ') ' ( ') '
1 2
x R R
x
x dx x dx x dx
p p p e e e
Filtered Back ProjectionFiltered Back Projection
FilteredFiltered B Baack Projectionck Projection
Filtered Back Projection
Filtered backprojection• Filter the measured projection data at different projection angles with a special function.• Backproject the filtered projection data to form the reconstructed image.
Filtering can be implemented in 2 ways, in the spatial domain, the filter operation is equivalent to to convolving the measured projection data using a special convolving function h(t)
p t p t h t, ( , ) ( , ) ( )
More efficient multiplication will be in the spatial frequency domain.• FFT the measured projection data into the frequency domain:p(,)=FT {p(t, )• Multiply the the fourier transform projections with the special function.•Inverse Fourier transform the product p’(,).
2D Vs. 3D2D Vs. 3D
RandomsRandoms
ScattersScatters
Principles of MRIPrinciples of MRI
Felix BlochFelix Bloch
AtomsAtoms
SpinsSpins
PrecessionPrecession
RF pulseRF pulse
T1 and T2T1 and T2
T1 and T2T1 and T2
T1 and T2T1 and T2
Effect of tissueEffect of tissueT1 and T2 CONSTANTS
T1 Constants at 1.5 T Controlled by TR
T2 Constants at 1.5 T Controlled by TE
Fat85
Muscle86045
White matter78090
Gray matter920100
CSF30001400
Slice selectionSlice selection
K spaceK space
K SpaceK Space
NMRNMR