This document provides an overview of brain CT, including its history, principles, indications, anatomy, and normal findings. It discusses how CT uses X-rays to reconstruct high-definition cross-sectional images of the brain, and how densities are described. Key indications for brain CT include acute stroke, head injury, and mental status changes. Normal anatomy seen on CT includes the ventricles, sulci and fissures, basal ganglia, and pineal and choroid plexus calcifications in many adults. The document outlines important axial slice locations and normal variations to aid physicians in accurate CT interpretation.

2. Basics and Anatomy of a brain CT
Dr Gauhar Mahmood Azeem
House Officer, New Radiology Dept.
SHL

3. CT scan machine

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

7. Slice them up!
Usually 5 to 10mm

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)

11. Hounsfield again

12. Hounsfield Units
• Related to the composition and nature of
tissue
• Represent the density of the tissue
• Also called CT number

13. An HFU table

14. Brain Anatomy as seen by House
Officer

15. Brain anatomy as seen by Professors

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

24. Admit it you’ve percussed your
relatives too!

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

28. Choroid Plexus and Pineal Gland
Calcifications

29. Calcification of Falx Cerebri

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

31. Ventricular system

32. Normal Anatomy
A. Falx Cerebri B. Sulcus
C. Gyrus D. Superior Sagittal Sinus

33. Thank You!