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Imaging Anatomy of Imaging Anatomy of the CNSthe CNS
Basic Imaging TypesBasic Imaging Types
X-rayX-ray CT (Computed Tomography)CT (Computed Tomography) MRI (Magnetic Resonance MRI (Magnetic Resonance
Imaging)Imaging) AngiographyAngiography
X-rayX-ray
Limited UseLimited Use Evaluation of:Evaluation of:
– Bones, fracturesBones, fractures– CalcificationCalcification
X-rayX-ray
Computed TomographyComputed Tomography
What is CT?What is CT?
X- ray study, therefore has risks.X- ray study, therefore has risks. Beams of X-ray are shot through Beams of X-ray are shot through
object, and received on the other side.object, and received on the other side. This is done in a 360This is done in a 360oo manner. manner. Computer reconstructions of each Computer reconstructions of each
360360o o turn gives us each image “slice”.turn gives us each image “slice”. Based on tissue density.Based on tissue density. Sections only in axial plane.Sections only in axial plane.
Magnetic Resonance Magnetic Resonance ImagingImaging
What is MR?What is MR?
Not an X-ray, electromagnetic (similar Not an X-ray, electromagnetic (similar to microwave)to microwave)
Electromagnetic field aligns all the Electromagnetic field aligns all the protons in the brain.protons in the brain.
Radiofrequency pulses cause the Radiofrequency pulses cause the protons to spin.protons to spin.
Amount of energy emitted from the spin Amount of energy emitted from the spin is proportional to number of protons in is proportional to number of protons in the tissue.the tissue.
No ferromagnetic objects.No ferromagnetic objects.
AngiographyAngiography
AngiographyAngiography
Real time X-ray studyReal time X-ray study Catheter placed through femoral Catheter placed through femoral
artery is directed up aorta into the artery is directed up aorta into the cerebral vessels.cerebral vessels.
Radio-opaque dye is injected and Radio-opaque dye is injected and vessels are visualizedvessels are visualized
Gold standard for studying Gold standard for studying cerebral vessels.cerebral vessels.
AngiographyAngiography
AP Right ICA Lateral Right ICA
AngiographyAngiography
AP Right Vertebral
Planes of SectionPlanes of Section
Axial (transverse)Axial (transverse) SagittalSagittal Coronal (frontal)Coronal (frontal) ObliqueOblique
What is an AXIAL What is an AXIAL section?section?
CT without contrast
Lateral ventricles
CT with contrast
CT bone window
Brain CT…Brain CT… Note that we take axial slices beginning from the Note that we take axial slices beginning from the
skull base., parallel to a standard line (orbito-skull base., parallel to a standard line (orbito-meatal or canthomeatal line).meatal or canthomeatal line).
The thickness of the slice (the distance between The thickness of the slice (the distance between a slice –picture- and the following slice –picture-) a slice –picture- and the following slice –picture-) is 10mm or as determined.is 10mm or as determined.
The skull base is a bony area with much small The skull base is a bony area with much small details, so we take the slices with less thickness details, so we take the slices with less thickness (5mm) to show al the details.(5mm) to show al the details.
You have to recognize the following:You have to recognize the following: 1- Cerebral hemispheres1- Cerebral hemispheres 2- Brainstem2- Brainstem 3- Ventricular system3- Ventricular system 4- Basal ganglia and thalamus4- Basal ganglia and thalamus 5- Basal cisterns (subarachnoid space)5- Basal cisterns (subarachnoid space)
Cerebral Hemispheres Cerebral Hemispheres (Lobes) & Brain (Lobes) & Brain Stem…Stem…
Lobes in the cerebral hemispheres Lobes in the cerebral hemispheres are the frontal, temporal, parietal, are the frontal, temporal, parietal, and occipital lobes.and occipital lobes.
Note that the white matter appears Note that the white matter appears grey, and the grey matter appears grey, and the grey matter appears white.white.
Brainstem is composed of the Brainstem is composed of the midbrian, pons & medulla midbrian, pons & medulla oblongata. oblongata.
Ventricular System…Ventricular System… It is composed of the lateral ventricles, 3It is composed of the lateral ventricles, 3rdrd
ventricle and the 4ventricle and the 4thth ventricle. ventricle. Remember that the ventricles contain the Remember that the ventricles contain the
choroid plexuses which maybe normally calcified choroid plexuses which maybe normally calcified so appears white in CT.so appears white in CT.
The lateral ventricle is composed of the frontal The lateral ventricle is composed of the frontal horn (anterior horn), ventricular body, occipital horn (anterior horn), ventricular body, occipital horn (posterior horn) and the temporal horn horn (posterior horn) and the temporal horn (inferior horn).(inferior horn).
Normally, the temporal horns can’t be seen in Normally, the temporal horns can’t be seen in CT. So, when they appear we call them CT. So, when they appear we call them “prominent temporal horns”; If they are dilated, “prominent temporal horns”; If they are dilated, this indicates hydrocephalus.this indicates hydrocephalus.
44thth ventricle is situated behind the pons. ventricle is situated behind the pons.
Basal Ganglia & Basal Ganglia & Thalamus…Thalamus…
You need to recognize:You need to recognize: 1- thalamus1- thalamus 2- caudate nucleus2- caudate nucleus 3- lentiform nucleus3- lentiform nucleus 4- internal capsule (it’s 4- internal capsule (it’s
anterior limb and it’s posterior anterior limb and it’s posterior limb)limb)
Basal Cisterns Basal Cisterns (Subarachnoid Space)(Subarachnoid Space)…… They contain cerebrospinal fluid (CSF), They contain cerebrospinal fluid (CSF),
so they normally appear black in brain so they normally appear black in brain CT.CT.
Basal cisterns are: Basal cisterns are: 1- prepontine cistern1- prepontine cistern 2- cerebellopontine cistern2- cerebellopontine cistern 3- interpeduncular cistern3- interpeduncular cistern 4- ambient cistern4- ambient cistern 5- quadrageminal cistern5- quadrageminal cistern 6- sylvian cistern (sylvian fissure) 6- sylvian cistern (sylvian fissure)
CT Brain Bone CT Brain Bone Window…Window…
It’s done by just giving an order for the CT It’s done by just giving an order for the CT machine to give us a CT brain- bone machine to give us a CT brain- bone window.window.
You have to recognize the following:You have to recognize the following: 1- Frontal, parietal, temporal & occipital 1- Frontal, parietal, temporal & occipital
bones (Bone appears white on CT scan).bones (Bone appears white on CT scan). 2- Bone sinuses (Sinuses are full of air)2- Bone sinuses (Sinuses are full of air)
MRI WeightingMRI Weighting
T1 Weighted MRI
T2 Weighted MRI
Axial T1
Axial T2
Axial FLAIR
Diffusion
Axial T1 with contrast
Brain MRIBrain MRI
Most brain lesion are seen by Most brain lesion are seen by T2 or FLAIR MRI.T2 or FLAIR MRI.
Usually, we use T1 MRI to Usually, we use T1 MRI to visualize brain anatomy, while visualize brain anatomy, while T2 MRI & FLAIR is used for T2 MRI & FLAIR is used for visualizing brain pathology.visualizing brain pathology.
Coronal T1 with contrast
Coronal Brain MRICoronal Brain MRI
You have to recognize:You have to recognize:
1- sella turcica: which 1- sella turcica: which contains the pituitary glandcontains the pituitary gland
2- cavernous sinus2- cavernous sinus
3- sphenoidal sinus3- sphenoidal sinus
4- optic chiasma4- optic chiasma
Sagittal T1 with contrast
4th ventriclr
Body of lateral ventricle Body
Genu
RostrumSplenium
Sagittal Brain MRI…Sagittal Brain MRI…
In a sagittal MRI, you have to In a sagittal MRI, you have to recognize:recognize:
The Corpus callosum that is The Corpus callosum that is composed of: rostrum, genu, body composed of: rostrum, genu, body and splenium.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