What can you see by MRI ? Stephen Paisey

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)

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)

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

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

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

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

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 90 seconds 15 slices (0.5mm thickness) Resolution 273µm

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.

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.

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.

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.

Magnetic Resonance Spectroscopy Versatility of MRI Magnetic Resonance Spectroscopy

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

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

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

Future Development of EMRIC Heteronuclear Imaging / Spectroscopy Higuchi, et al Nature Neuroscience  8, 527 - 533 (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.

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, 527 - 533 (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), 1627-1636

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