Image reproduction +fMRI. Filtered Back Projection.
-
date post
22-Dec-2015 -
Category
Documents
-
view
217 -
download
1
Transcript of Image reproduction +fMRI. Filtered Back Projection.
![Page 1: Image reproduction +fMRI. Filtered Back Projection.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d815503460f94a65ec2/html5/thumbnails/1.jpg)
Image reproduction Image reproduction +fMRI+fMRI
![Page 2: Image reproduction +fMRI. Filtered Back Projection.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d815503460f94a65ec2/html5/thumbnails/2.jpg)
![Page 3: Image reproduction +fMRI. Filtered Back Projection.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d815503460f94a65ec2/html5/thumbnails/3.jpg)
Filtered Back ProjectionFiltered Back Projection
![Page 4: Image reproduction +fMRI. Filtered Back Projection.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d815503460f94a65ec2/html5/thumbnails/4.jpg)
Filtered Back Projection
![Page 5: Image reproduction +fMRI. Filtered Back Projection.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d815503460f94a65ec2/html5/thumbnails/5.jpg)
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’(,).
![Page 6: Image reproduction +fMRI. Filtered Back Projection.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d815503460f94a65ec2/html5/thumbnails/6.jpg)
Phase EncodingPhase Encoding
Gradient
Slice Plane
Slice Phase Frequency
XY Z X or Y Y or X
XZ Y X or Z Z or X
YZ X Y or Z Z or Y
![Page 7: Image reproduction +fMRI. Filtered Back Projection.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d815503460f94a65ec2/html5/thumbnails/7.jpg)
Phase encodingPhase encoding
![Page 8: Image reproduction +fMRI. Filtered Back Projection.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d815503460f94a65ec2/html5/thumbnails/8.jpg)
K spaceK space
![Page 9: Image reproduction +fMRI. Filtered Back Projection.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d815503460f94a65ec2/html5/thumbnails/9.jpg)
K SpaceK Space
![Page 10: Image reproduction +fMRI. Filtered Back Projection.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d815503460f94a65ec2/html5/thumbnails/10.jpg)
Partial K Partial K space space
reconstrucreconstructiontion
![Page 11: Image reproduction +fMRI. Filtered Back Projection.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d815503460f94a65ec2/html5/thumbnails/11.jpg)
Partial K space Partial K space reconstructionreconstruction
![Page 12: Image reproduction +fMRI. Filtered Back Projection.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d815503460f94a65ec2/html5/thumbnails/12.jpg)
Partial K space Partial K space reconstructionreconstruction
![Page 13: Image reproduction +fMRI. Filtered Back Projection.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d815503460f94a65ec2/html5/thumbnails/13.jpg)
Zero paddingZero padding
![Page 14: Image reproduction +fMRI. Filtered Back Projection.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d815503460f94a65ec2/html5/thumbnails/14.jpg)
ConjugatConjugate e
symmetrysymmetry
![Page 15: Image reproduction +fMRI. Filtered Back Projection.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d815503460f94a65ec2/html5/thumbnails/15.jpg)
Conjugate symmetryConjugate symmetry
![Page 16: Image reproduction +fMRI. Filtered Back Projection.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d815503460f94a65ec2/html5/thumbnails/16.jpg)
Homodyne Homodyne reconstructionreconstruction
![Page 17: Image reproduction +fMRI. Filtered Back Projection.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d815503460f94a65ec2/html5/thumbnails/17.jpg)
Homodyne Homodyne reconstructionreconstruction
![Page 18: Image reproduction +fMRI. Filtered Back Projection.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d815503460f94a65ec2/html5/thumbnails/18.jpg)
Homodyne Homodyne reconstructionreconstruction
![Page 19: Image reproduction +fMRI. Filtered Back Projection.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d815503460f94a65ec2/html5/thumbnails/19.jpg)
HomodyHomodyne ne
reconstrreconstructionuction
![Page 20: Image reproduction +fMRI. Filtered Back Projection.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d815503460f94a65ec2/html5/thumbnails/20.jpg)
Mechanism of BOLD Mechanism of BOLD Functional MRIFunctional MRI
Brain activity
Oxygen consumption Cerebral blood flow
OxyhemoglobinDeoxyhemoglobin
Magnetic susceptibility
T2*
MRI signal intesity
![Page 21: Image reproduction +fMRI. Filtered Back Projection.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d815503460f94a65ec2/html5/thumbnails/21.jpg)
Magnetic Properties of Magnetic Properties of Oxyhemoglobin and Oxyhemoglobin and DeoxyhemoglobinDeoxyhemoglobin
Deoxyhemoglobin: paramagnetic ( > 0) paramagnetic with respect to the surrounding tissue
Oxyhemoglobin: diamagnetic ( < 0) isomagnetic with respect to the surrounding tissue
22HbOOHb
cdiamagneti ,0 icparamagnet ,0 if
HM
![Page 22: Image reproduction +fMRI. Filtered Back Projection.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d815503460f94a65ec2/html5/thumbnails/22.jpg)
TT22* Effect in fMRI* Effect in fMRI
excitation reception
MR
sig
nal (S
)
actionrest
TE t
![Page 23: Image reproduction +fMRI. Filtered Back Projection.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d815503460f94a65ec2/html5/thumbnails/23.jpg)
Time Series and Activation Time Series and Activation MapsMaps
Off Off Off OffOn On On On
Scan Number
Sig
nal
In
ten
sity
![Page 24: Image reproduction +fMRI. Filtered Back Projection.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d815503460f94a65ec2/html5/thumbnails/24.jpg)
Temporal resolutionTemporal resolution
Impulse-response function
2s
5s
12s
![Page 25: Image reproduction +fMRI. Filtered Back Projection.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d815503460f94a65ec2/html5/thumbnails/25.jpg)
0 20 40 60 80 100 120
4
3
2
1
Com
pone
nt
Frame
Temporal components (sd, % variance explained)
105.7, 77.8%
26.1, 4.8%
15.8, 1.7%
14.8, 1.5%
Slice
Com
pone
nt
Spatial components
0 2 4 6 8 10
1
2
3
4
PCA_IMAGE: PCA of time space:
1: excludefirst frames
2: drift
3: long-range correlationor anatomicaleffect: removeby converting to % of brain
4: signal?