Full body and organ anatomical imaging: T1/T2 weighted
imaging.
These multi-slice spin echo images of rat brain with an in-plane
resolution of 134µm and a slice thickness of 400 µm
show high structural details.
Angiography
Angiography: Detailed images of vasculature in the head
and brain for development, stroke and tumours.
A 3D reconstruction of blood vessels of rat head (at 117 µm)
obtained using a flow-compensated 2D FLASH sequence.
These images were obtained without using a contrast agent.
Diffusion Tensor imaging
Diffusion tensor imaging: Diffusion of water molecules
in biological tissues can be used to track fibre paths related to
brain injury.
Diffusion Weighted-Spin echo in rat brain.
The insert indicates the colour coding of the directional vectors:
Left-right: Red
Up-down: Green
Dorsal-rostral: Blue
Directional variation in the oriented fibres, optical pathways and
ventricles can be ascertained.
Fibre Tractography
DTI data can be further processed with specialist software (in
this case ExploreDTI ) to reconstruct in 3D any fibre tracts of
interest. The image on the right shows a reconstruction of a rat
corpus callosum. Once reconstructed the volume of these fibres can
be calculated. This approach is useful for the monitoring of damage
to fibre tracts due to stroke or disease.
Spectroscopy
Single voxel spectroscopy: allows detection of the chemical
composition of a selected region.
1H-Press spectra in the right hemisphere of a normal rat. Classic
major metabloite peaks of Cr+PCr (Creatine and Phosphocreatine),
Glut+Glutm (Glutamine and Glutamate), Cho (Choline), and N-Aspartyl
Aspartaate (NAA) are present.
Heart Imaging
Triggered heart imaging: Cardiac gating allows image acquisition
at different phases of the cardiac cycle. Image sequences can be
made into a movie to reveal important structural and functional
data.
The images show ECG-triggered CINE-FLASH images of juvenile rat
at different parts of cardiac cycle. Left image:Four chamber view,
Right image:Short axis view - Tagged.
fMRI
Functional imaging: Signal changes in the brain due to
changing neuronal activity can be measured by BOLD (blood oxygenation
level-dependent) contrast.
This image (generated in FSL) shows the activation of a rat brain
in response to an amphetamine challenge. The brain is scanned many
times in the presence and absence of of stimulation. The resultant
images are then aligned and subtracted from each other. A map is
then generated of any brain areas that have a significantly different
contrast between the active and inactive states (orange areas) which
can be overlaid on a higher quality anatomical image to reveal which
areas are activated by the stimulus presented to the subject.
Molecular imaging
Tracking labelled cells within a graft or active transport
along neuronal pathways.
Embryonic stem cells were lipofected with USPIO's (ultra small
particle iron oxide), implanted into a rat brain and their fate
tracked with high-resolution 2D MRI(A).
The labelled embryonic stem cells migrate along the corpus callosum
to the affected area (C) (Images courtesy of Hoehn et al., MPI for
Neurological Research, Cologne, Germany).
3-D imaging
True 3D imaging gives higher through plane resolution and allows
image reslicing in any plane.
This multi-view image of a chick embryo shows the same slice of
the image in all 3 orientations at 117µm. The maximum intensity
projection reconstruction (bottom right) allows internal structures
to be visualised with relation to the external form.
This movie shows a high resolution scan of a new caledonian crow
brain.
