1. What can you see by MRI ?
Stephen Paisey

2. Each imaging technique has its own advantages
Why MRI ?
Each imaging technique has its own advantages
Optical imaging
Very high spatial resolution
(sub cellular)
Fast time resolution (µs)
Non invasive
Very low sample
penetration (1-2mm)

3. Each imaging technique has its own advantages
Why MRI ?
Each imaging technique has its own advantages
Optical imaging
Ultrasound
Very high spatial resolution
(sub cellular)
Fast time resolution (µs)
Non invasive
Very low sample
penetration (1-2mm)
Non invasive
Portable
Average sample penetration
Average time resolution
(ms-s)
Low spatial resolution
(mm-cm)

4. Each imaging technique has its own advantages
Why MRI ?
Each imaging technique has its own advantages
Optical imaging
Ultrasound
Very high spatial resolution
(sub cellular)
Fast time resolution (µs)
Non invasive
Very low sample
penetration (1-2mm)
Non invasive
Portable
Average sample penetration
Average time resolution
(ms-s)
Low spatial resolution
(mm-cm)
CT/Xray
Good sample penetration
Good sensitivity
Average time resolution
(s-min)
Average spatial resolution (350 µ m)
Requires ionising radiation

5. Each imaging technique has its own advantages
Why MRI ?
Each imaging technique has its own advantages
Optical imaging
Ultrasound
Very high spatial resolution
(sub cellular)
Fast time resolution (µs)
Non invasive
Very low sample
penetration (1-2mm)
Non invasive
Portable
Average sample penetration
Average time resolution
(ms-s)
Low spatial resolution
(mm-cm)
CT/Xray
PET imaging
Good sample penetration
Good sensitivity
Average time resolution
(s-min)
Average spatial resolution (350 µ m)
Requires ionising radiation
Good sample penetration
Very high sensitivity (pM)
Low spatial resolution (mm)
Requires radioactive tracer
compounds

6. Each imaging technique has its own advantages
Why MRI ?
Each imaging technique has its own advantages
Optical imaging
Ultrasound
Very high spatial resolution
(sub cellular)
Fast time resolution (µs)
Non invasive
Very low sample
penetration (1-2mm)
Non invasive
Portable
Average sample penetration
Average time resolution
(ms-s)
Low spatial resolution
(mm-cm)
CT/Xray
MRI
PET imaging
Good sample penetration
Good sensitivity
Average time resolution
(s-min)
Average spatial resolution (350 µ m)
Requires ionising radiation
Good sample penetration
Non invasive
Adjustable contrast
Average spatial resolution
(70 µ m)
Low sensitivity (mM)
Low time resolution
(seconds to hours)
Good sample penetration
Very high sensitivity (pM)
Low spatial resolution (mm)
Requires radioactive tracer
compounds

7. Quick to acquire (10 min) exaggerates susceptibility boundaries
Versatility of MRI
MRI acquisition parameters can be tuned to produce a range of image contrasts
FLASH
Images
Quick to acquire (10 min) exaggerates susceptibility boundaries T1 T2
T2*
Diffusion
RARE
Images
Longer to acquire (10 min - hours) less susceptible to artefacts

8. Versatility of MRI Echo Planar Imaging Quality optimised
Speed optimised
Whole brain scan time 0.6 seconds
15 slices (0.5mm thickness)
Resolution 273µm
Rapid imaging technique (0.5-10s)
Highly prone to distortion and ghosting artefacts
Lower resolution than
FLASH or RARE
Used when speed is more important than quality
Quality optimised
Whole brain scan time seconds
15 slices (0.5mm thickness)
Resolution 273µm

9. Versatility of MRI fMRI / phMRI
Functional imaging involves analysing the differences in contrast between images of a resting brain state and an excited brain state
Contrast differences can arise from; a decrease in blood oxygenation levels, dilation of blood vessels, increase in blood flow, subject movement, magnet drift, random noise.

10. Diffusion Tensor Imaging
Versatility of MRI
Diffusion Tensor Imaging
DTI measures the mean diffusion direction in each voxel and colour codes the resultant images by diffusion direction
This scan type highlights fibre bundles with in the brain
7 minute scan time for whole brain at 312 µm in-plane resolution.

11. Versatility of MRI Angiography No contrast agents required
20 min scan time
This scan type is useful for following changes blood flow due to angiogenesis or stroke models.

12. Magnetic Resonance Spectroscopy
Versatility of MRI
Magnetic Resonance Spectroscopy
MRI usually focuses on the water signal from within samples
There are other proton signals that can be detected
The spectrum reports natural metabolite concentrations from specifically chosen regions within a sample
Concentrations down to ~0.5mM can be detected
10 minutes set up time + 10 minutes scan time.

13. Magnetic Resonance Spectroscopy
Versatility of MRI
Magnetic Resonance Spectroscopy

14. Versatility of MRI Spectral editing
Peak overlap in crowded spectra make the analysis of some metabolites difficult
Richard Edden is developing a method to extract out peaks in certain metabolites
NAA

15. Versatility of MRI Spectral editing
Peak overlap in crowded spectra make the analysis of some metabolites difficult
Richard Edden is developing a method to extract out peaks in certain metabolites
NAA
Applying a pulse to methyl groups in a molecule
Inverts the CH signal in a different region of the spectum
This technique can be adapted to detect: GABA - Glutamate/Glutamine - Lactate – Ascorbate – Creatine – Choline - N-Acetyl Aspartate - N-Acetyl Aspartyl Glutamate – myoinositol - lipid/fat

16. Chemical Shift Imaging
Versatility of MRI
Chemical Shift Imaging
CSI involves taking the metabolite concentration information and mapping it onto an anatomical image.
30 minute scan time
Spectra are less well resolved than PRESS but with more volume information

17. Future Development of EMRIC
Heteronuclear Imaging / Spectroscopy
Higuchi, et al Nature Neuroscience  8, (2005)
1H is not the only NMR detectable nucleus. We hope to obtain new coils to enable the detection of other nuclei such as:
19F for tracer uptake studies
31P to monitor energy usage in different tissue types.

18. Future Development of EMRIC
Heteronuclear Imaging / Spectroscopy
1H is not the only NMR detectable nucleus. We hope to obtain new coils to enable the detection of other nuclei such as:
19F for tracer uptake studies
31P to monitor energy usage in different tissue types.
Higuchi, et al Nature Neuroscience  8, (2005)
Functional Imaging
We are making a concerted effort to develop fMRI this year and would welcome the involvement of people wishing to use the technique. There are many aspects to consider:
Appropriate anaesthetic
Stimulus type / method of delivery
Timescale / strength of response
Appropriate analysis method
Shwarz, AJ et al, Neuroimage, 34 (4),

19. Lots of other help from CUBRIC
Acknowledgements
Dave McGonigle
PawełTokarczuk
Andrew Stewart
Lots of other help from CUBRIC