4. CT Head: Extremely important
investigation
• CT head is an extremely important
investigation used routinely in indoor as well
as ER patients.
• A quality physician needs to be able to
accurately interpret and act upon certain
findings without specialist advise, because
these disease processes are time dependant
and demand immediate action.
5. History of the CT
• Sir Godfrey Hounsefield- an electrical engineer-
1972
• Nobel Prize for Physiology or Medicine 1979
• Hounsfield units named after him
• Through the years CT’s have come from 1
rotation in 6 minutes to one in under 0.33
seconds
6. Principle
• X rays are passed through the patient in a
circular path
• The absorption data is used in a computer to
reconstruct high definition images
• The images are seen on a computer output
device or films and be interpreted
• 3D reconstruction is also possible
8. Basics
• Always describe CT findings as densities,
isodense/hypodense/hyperdense
• Higher the density the whiter it is (towards
bone)
• Lower the density the darker it is (towards air)
• Brain here is the reference density and thus
isodense
9. Indications for Brain CT
• Acute stroke
• Transient Ischemic Attack
• Acute headache with focal neurological signs
• Acute head injury
• Suspected hydrocephalus
• Mental status change
• Secondary indications when MRI not available
including diplopia, CN problems, seizures,
syncope etc
10. Indications for CT brain with IV
contrast
• To look for
• Tumours
• Infections (meningial enhancement, abscess)
• Inflammation (MS, granulomatous diseases
etc)
16. Axial Sections of CT brain
• Axial sections are most important in a head CT
• We must have for a complete view posterior
fossa and supratentorial(above tentorium
cerebelli) cuts
17. Axial Sections of CT brain
• Posterior Fossa Cuts
• Above Foramen Magnum, Level of 4th
ventricle, Above 4th ventricle, Tentorial
• Supra Tentorial Cuts
• Third Ventricle Level, Lateral Ventricle Level,
Above Ventricular level
18. Normal Anatomy
A. Orbit B. Sphenoid Sinus
C. Temporal Lobe D. External Auditory Canal
E. Mastoid Air Cells F. Cerebellar Hemisphere
19. Normal Anatomy
A. Frontal Lobe B. Frontal Bone (Superior Surface of Orbital Part)
C. Dorsum Sellae D. Basilar Artery
E. Temporal Lobe F. Mastoid Air Cells
G. Cerebellar Hemisphere
20. Of Cisterns, Sulci and Fissures
• A cistern is any opening in the subarachnoid
space of the brain created by a separation of
the arachnoid and pia matter. These spaces
are filled with cerebrospinal fluid.
• A sulcus is a depression in the cerebral cortex
• A fissure is a large furrow that divides the
brain into lobes, and also into the two
hemispheres
21. Normal Anatomy
A. Frontal Lobe B. Sylvian Fissure (divides frontal, parietal from temporal)
C. Temporal Lobe D. Suprasellar Cistern
E. Midbrain F. Fourth Ventricle
G. Cerebellar Hemisphere
22. Normal Anatomy
A. Falx Cerebri B. Frontal Lobe
C. Anterior Horn of Lateral Ventricle D. Third Ventricle
E. Quadrigeminal Plate Cistern F. Cerebellum
23. Normal Anatomy
A. Anterior Horn of the Lateral Ventricle B. Caudate Nucleus (BG)
C. Anterior Limb of the Internal Capsule D. Putamen and Globus Pallidus (BG)
E. Posterior Limb of the Internal Capsule F. Third Ventricle
G. Quadrigeminal Plate Cistern H. Cerebellar Vermis
25. Normal Anatomy
A. Genu of the Corpus Callosum B. Anterior Horn of the Lateral Ventricle
C. Internal Capsule D. Thalamus
E. Pineal Gland F. Choroid Plexus
G. Straight Sinus
26. Normal Calcifications in the brain
• Pineal Gland
– seen in 2/3 of the adult population and increases with age
– calcification over 1cm in diameter or under 9 years of age may be suggestive
of a neoplasm
• Hebenula
– it has a central role in the regulation of the limbic system and is often calcified
with a curvilinear pattern a few millimeters anterior to the pineal body in 15%
of the adult population
• Choroid Plexus
– a very common finding, usually in the atrial portions of the lateral ventricles
– calcification in the third or fourth ventricle or in patients less than 9 years of
age is uncommon
27. Normal Calcifications in the brain
• Basal Ganglia Calcification
– are usually idiopathic incidental findings that have an incidence of ~1% (range
0.3-1.5%) and increases with age
– usually demonstrate a faint punctuate or a coarse conglomerated symmetrical
calcification pattern
• Falx, Dura Matter, Tentorium Cerebelli
– occur in ~10% of the elderly population
– dural and tentorial calcifications are usually seen in a laminar pattern and can
occur anywhere within the cranium
• Superior Saggital Sinus
– common age-related degeneration sites and usually have laminar or mildly
nodular patterns
30. Normal Anatomy
A. Falx Cerebri B. Frontal Lobe
C. Body of the Lateral Ventricle D. Splenium of the Corpus Callosum
E. Parietal Lobe F. Occipital Lobe
G. Superior Sagittal Sinus