Transcript Neuroimaging

Imaging Anatomy of the CNS
Basic Imaging Types
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X-ray
CT (Computed Tomography)
MRI (Magnetic Resonance Imaging)
Angiography
X-ray
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Limited Use
Evaluation of:
– Bones, fractures
– Calcification
X-ray
Computed Tomography
What is CT?
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X- ray study, therefore has risks.
Beams of X-ray are shot through object, and
received on the other side.
This is done in a 360o manner.
Computer reconstructions of each 360o turn
gives us each image “slice”.
Based on tissue density.
Sections only in axial plane.
Magnetic Resonance Imaging
What is MR?
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Not an X-ray, electromagnetic (similar to microwave)
Electromagnetic field aligns all the protons in the
brain.
Radiofrequency pulses cause the protons to spin.
Amount of energy emitted from the spin is
proportional to number of protons in the tissue.
No ferromagnetic objects.
Angiography
Angiography
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Real time X-ray study
Catheter placed through femoral artery is
directed up aorta into the cerebral vessels.
Radio-opaque dye is injected and vessels are
visualized
Gold standard for studying cerebral vessels.
Angiography
AP Right ICA
Lateral Right ICA
Angiography
AP Right Vertebral
Planes of Section
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Axial (transverse)
Sagittal
Coronal (frontal)
Oblique
What is an AXIAL section?
CT without contrast
Lateral ventricles
CT with contrast
CT bone window
Brain CT…
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Note that we take axial slices beginning from the skull base.,
parallel to a standard line (orbito-meatal or canthomeatal line).
The thickness of the slice (the distance between a slice –
picture- and the following slice –picture-) is 10mm or as
determined.
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The skull base is a bony area with much small details, so we
take the slices with less thickness (5mm) to show al the details.
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You have to recognize the following:
1- Cerebral hemispheres
2- Brainstem
3- Ventricular system
4- Basal ganglia and thalamus
5- Basal cisterns (subarachnoid space)
Cerebral Hemispheres (Lobes)
& Brain Stem…
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Lobes in the cerebral hemispheres are the
frontal, temporal, parietal, and occipital
lobes.
Note that the white matter appears grey,
and the grey matter appears white.
Brainstem is composed of the midbrian,
pons & medulla oblongata.
Ventricular System…
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It is composed of the lateral ventricles, 3rd ventricle and
the 4th ventricle.
Remember that the ventricles contain the choroid
plexuses which maybe normally calcified so appears
white in CT.
The lateral ventricle is composed of the frontal horn
(anterior horn), ventricular body, occipital horn (posterior
horn) and the temporal horn (inferior horn).
Normally, the temporal horns can’t be seen in CT. So,
when they appear we call them “prominent temporal
horns”; If they are dilated, this indicates hydrocephalus.
4th ventricle is situated behind the pons.
Basal Ganglia & Thalamus…
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You need to recognize:
1- thalamus
2- caudate nucleus
3- lentiform nucleus
4- internal capsule (it’s anterior limb and
it’s posterior limb)
Basal Cisterns (Subarachnoid
Space)…
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They contain cerebrospinal fluid (CSF), so they
normally appear black in brain CT.
Basal cisterns are:
1- prepontine cistern
2- cerebellopontine cistern
3- interpeduncular cistern
4- ambient cistern
5- quadrageminal cistern
6- sylvian cistern (sylvian fissure)
CT Brain Bone Window…
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It’s done by just giving an order for the CT machine to
give us a CT brain- bone window.
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You have to recognize the following:
1- Frontal, parietal, temporal & occipital bones (Bone
appears white on CT scan).
2- Bone sinuses (Sinuses are full of air)
MRI Weighting
T1 Weighted MRI
T2 Weighted MRI
Axial T1
Axial T2
Axial FLAIR
Diffusion
Axial T1 with contrast
Brain MRI
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Most brain lesion are seen by T2 or
FLAIR MRI.
Usually, we use T1 MRI to visualize
brain anatomy, while T2 MRI & FLAIR
is used for visualizing brain pathology.
Coronal T1 with contrast
Coronal Brain MRI
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You have to recognize:
1- sella turcica: which contains the
pituitary gland
2- cavernous sinus
3- sphenoidal sinus
4- optic chiasma
Body
Body of lateral ventricle
Genu
Rostrum
4th ventriclr
Sagittal T1 with contrast
Splenium
Sagittal Brain MRI…
In a sagittal MRI, you have to recognize:
The Corpus callosum that is composed of:
rostrum, genu, body and splenium.
Neck MRA
Brain MRA
Brain MRA
Brain MRA
Sagittal T1 Cervical spine
Sagittal T2 Cervical
spine
Sagittal T1 dorsal spine
Coronal T1 Cervical spine