1. Introduction to diffusion MRI
Robert Frost

2. Field gradients
𝜔(𝑥)=𝛾𝐵(𝑥)

3. Phase representation

4. Phase representation

5. Diffusion gradient

6. Reverse diffusion gradient
“Refocus”

7. Diffusion parallel to gradient

8. Reverse diffusion gradient
Not fully refocused

9. Diffusion perpendicular to gradient

10. Reverse diffusion gradient
Refocusing of spins diffusing parallel to gradient

11. Diffusion encoding
Measure a reduced signal when spins diffuse along the direction of the diffusion gradient
Measure less signal if there is more diffusion
Can measure diffusion in different directions by repeating the experiment with different diffusion gradient orientations

12. Water self-diffusion in the brain
Diffusion coefficient, 𝐷~ 10 −3 𝑚𝑚 2 /𝑠
𝑟 𝑅𝑀𝑆 = 2𝐷𝑡 ~10𝜇𝑚 in 50ms
anisotropic
isotropic