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