1. Basics of MRI

2. NMR verses MRI
Spectrum
Projection

3. Spin Warp MRI

4. Slice Selection
Excitation Spectrum RF +
Selected Slice
Gradient

5. Slice Selection RephasingRF
Gradient

6. Frequency Encoding
NMR &
Sampling
Object
Profile
Gradient GR
dFOV

7. Frequency Encoding
NMR
Gradient

8. Phase Encoding npe NMR Gread Gphase
Collect a trace for each value of the phase encoding gradient
Just like 2d NMR
NMR
Gread
Gphase
npe

9. Contrast in MRI Image contrast arises from differences in signals!
What differences?
Signal is a function of:
 - Proton density
T1 Spin-Lattice relaxtion time
T2 - Spin-Spin relaxation time
T2* - magnetic susceptibility
D - diffusion
flow - blood, CSF etc
function - brain function, cardiac function
etc

10. Basic MRI Acquisition Schemes
Gradient Echo (Spin Warp) - GEMS
T2* dependence
Spin Echo - SEMS
T2 dependence
Fast Spin Echo - FSE
Echo Planar Imaging - EPI
Spiral MRI
Many hybrids of above!!!

11. Gradient Echo GEMS - Varian seqlib Other names: FLASH, GRASS, FFE
< 90° (flip angle)
Contrasts:
dependent on  & TR
T1, proton density
Sensitivity to Susceptibility depends on TE
Variants:
RF or Gradient Spoiling
Turbo FLASH (SnapShot)
RF &
NMR
GSlice
GRead
GPhase

12. Refocused Gradient Echo
GEMS - Varian seqlib
Other names:
FAST, Refocused FLASH, GRASS, FFE, FISP
< 90° (flip angle)
Steady-state preserved by rewinding phase gradient.
Contrasts:
dependent on  & TR
T1, proton density
Sensitivity to Susceptibility depends on TE
RF &
NMR
GSlice
GRead
GPhase

13. Spin Echo SEMS - Varian seqlib Contrasts: T2 thru TE T1 thru TR
Proton density
RF &
NMR
GSlice
GRead
GPhase

14. Fast Spin Echo Fast Spin Echo (FSE) Turbo Spin Echo (TSE) RARE RF &
NMR
GSlice
GRead
GPhase

15. Echo Planar Imaging - EPI
Images in <50-100ms
Gradient Echo &
Spin Echo variants
Disadvantages:
Susceptibility
Nyquist Ghosts
RF &
NMR
GSlice
GRead
GPhase

16. Spiral Imaging Images in <50-100ms Gradient Echo &
Spin Echo variants
Disadvantages:
Very Complicated Recon
Very Demanding of HW
Advantages:
Motion insensitivity
RF &
NMR
GSlice
GRead
GRead