1.
Go to 51:47-1:06 mark listen for 9 minutes

2. = γ
= γ 2π 2π

4. Spin echo signal strength More Signal Loss when encoding for diffusion
Diffusion of water used in Diffusion MRI Imaging and Diffusion Tensor Imaging (DTI) MRI
Spin echo signal strength
More Signal Loss when encoding for diffusion

5. Don’t let protons move -NO DIFFUISIONy RF Gx Gy Gz -
Time
The rest of the sequence x
Area under the gradients is b
Don’t let protons move -NO DIFFUISION
protons (Hydrogen)
signal loss
with DIFFUISION

6. = Dxx 1 0 0 Dxx Dxy Dxz 1 Dyx Dyy Dyz Dzx Dzy Dzz Y X Z D = Dxx Time
1 0 0
Dxx Dxy Dxz
Dyx Dyy Dyz
Dzx Dzy Dzz 1
D = Dxx
= Dxx RF Gx Gy Gz -
Time Y X Z
Every voxel has a diffusion
tensor to describe diffusion

7. 1 1 0 Dxx Dxy Dxz 1 Dyx Dyy Dyz Dzx Dzy Dzz = ½(Dxx + 2Dyx + Dyy) Y X
1 1 0
Dxx Dxy Dxz
Dyx Dyy Dyz
Dzx Dzy Dzz 1
(½)
= ½(Dxx + Dyx + Dxy + Dyy)
= ½(Dxx + 2Dyx + Dyy) Y RF Gx Gy Gz -
Time X Z

8. another stroke example
Why diffusion
another stroke example
Diffusion Weighted Image
Size of DTI ellipsoid
Dead
Perfusion Weighted Imaging
Will Die
Blood Volume
Blood Flow
Mean Transit Time
Look for mismatch and find healthy tissue

9. Information available through DTI
2) Fiber tracking
Information available through DTI
Tract
Monkey brain, in-vivo
Pixel by pixel map of the diffusion ellipsoids in the ROI shown in the image.
The Diffusion ellipsoids summarize all the information that we can obtain with DTI.
This presentation is focused on the scalar ones, but we can clearly see the direction of the fibers in the corpus callosum.

10. Fiber tracking rat spine – T2 background post injury
Diffusion Tensor Imaging
Colored FA
ADC
Fiber tracking rat spine – T2 background post injury
DWI T2
Fiber tracking mouse brain
Pre injury
Post injury

11. Functional Magnetic Resonance Imaging
fMRI
Functional Magnetic Resonance Imaging

12. The BOLD Effect Frequency spread causes signal loss over time
Karen Miller
Frequency spread causes signal loss over time
BOLD contrast: Amount of signal loss reflects [dHb]
Deoxygenated hemoglobin – unpaired iron electrons
Contrast increases with delay (TE = echo time)

13. Vascular Response to Activation
Karen Miller
neuron
capillary
HbO2
HbO2
dHb
HbO2
HbO2
dHb
dHb = deoxyhemoglobin
HbO2 = oxyhemoglobin
[dHb]
O2 metabolism
blood flow
Decreased deoxygenated larger signal in metabolically active regions
blood volume

15. Language fMRI task Acquire Images when someone is processing language
and when they are not.
Subtract them.
Colored areas
are the signals
that remain.
Science Direct

16. Advanced Preoperative Neurosurgery MRI (unique to UKY in Kentucky)
Function MRI – Listening to Music
Temporal Lobe Epilepsy Surgery
Young Girl – Aspiring Musician – Surgery Complete Success
Motor (finger tapping)
Language (word generation)

17. Spectroscopy

18. Forget about making an image, let’s look at hydrogen other than H20
inside the BIG RED VOXEL.
Frequency

19. Frequency
Frequency

21. More details – notice line splitting
Extra chemical shift due to J coupling

24. Multi – Voxel Spectroscopy (aka Chemical Shift Imaging – CSI)
Do many voxels at once
Can be some disadvantages with signal to noise (S/N) and “voxel bleeding”
(ie signal from one voxel may appear in neighboring voxels due to poor shim)

25. Can we image with other nuclei than hydrogen?
We can image and do spectroscopy with other nuclei !!

26. Can even image with 23Na in Rat Brain
(low resolution images are sodium 23 images)
(high resolution images are hydrogen images)
Need different
hardware

28. 31P Spectroscopy (again – need different hardware)
Capable of detecting those key metabolites that play a role in tissue metabolism

29. 13C Spectroscopy (again – need different hardware)
Low sensitivity, but almost all metabolically relevant compounds contain
carbon and large chemical shifts allow peak discrimination.
Can infuse with 13C rich solution and follow metabolic pathway.