1.
“HOW TO READ A
HEAD CT SCAN”
4 MARCH, 2013

2.
MUST FOR EVERY PHYSICIAN
• CT HEAD is an extremely useful diagnostic tool
used routinely in the care of A&E patients.
• The treating physician needs to be able to
accurately interpret and act upon certain CT
findings without specialist (e.g., radiologist)
assistance, because many disease processes are
time dependent and require immediate action.
• It has been shown that even a brief educational
intervention can significantly improve the
physician’s ability to interpret cranial CT scans.

3.
SCHEME OF THE LECTURE
• BASIC PRINCIPLES OF CT SCAN
• NORMAL NEUROANATOMY AS SEEN ON HEAD
CT SCANS
• ILLUSTRATIONS

4.
BASIC PRINCIPLES OF
CT SCAN

5.
HISTORY
• Sir Godfrey hounsfield-1972
• Nobel prize in 1979
• Original scanners took approximately 6
minutes to perform a rotation (one slice) and
20 minutes to reconstruct. Despite many
technological advances since then, the
principles remain the same.

6.
PARTS
1) Gantry- which houses X ray apparatus
2) X ray tube-akin to that in a X ray machine.
3) Detectors
4) Patient couch
5) Viewing console

7.
PRINCIPLE
• Uses X rays applied in sequence of slices
across the organ
• Images reconstructed from X ray absorption
data
• X ray beam moves around the patient in a
circular path

8.
PRINCIPLES OF CT………

9.
PRINCIPLE…..
• CT scan provides a 3D display of the
intracranial anatomy built up from a vertical
series of transverse axial tomograms.
• Each tomogram represents a horizontal slice
through the patient’s head.

10.
TECHNIQUE…..
Slice thickness may
vary, but in general, it is
between 5 and 10 mm
for a routine Head CT

11.
BASICS….
• X-RAYS ARE ABSORBED TO DIFFERENT DEGREES BY
DIFFERENT TISSUES
• Always describe CT findings as densities-
isodense/hypodense/hyperdense.
• Higher the density = whiter is the appearance
• Lower the density = darker the appearance
• Brain is the reference density
• Anything of the density as brain= isodense
• Higher density than brain= hyperdense ( skull is the
best example)
• Anything darker (lower density) than brain=
hypodense( CSF and air are classical examples)

12.
HOUNSFIELD UNITS
• Related to composition & nature of tissue
• Represent the density of tissue
• Also called as CT NUMBER

13.
air --- 1000
fat ---70
Pure water 0
Csf +8
White matter +30
Gray matter +45
blood +70
Bone/calcification +1000

14.
Densities on ct scan…….

15.
NORMAL NEUROANATOMY AS
SEEN ON HEAD CT SCANS

16.
AXIAL SECTIONS OF CT HEAD
POSTERIOR FOSSA CUTS
-ABOVE THE FORAMEN MAGNUM LEVEL
-LEVEL OF THE FOURTH VENTRICLE
-ABOVE THE FOURTH VENTRICULAR LEVEL
-TENTORIAL
SUPRATENTORIAL CUTS
-THIRD VENTRICULAR LEVEL
-LATERAL VENTRICULAR LEVEL
-ABOVE THE VENTRICULAR LEVEL

17.
Lateral View of Brain

18.
NORMAL ANATOMY…….
A= ORBIT , B= SPHENOID SINUS , C= TEMPORAL LOBE, D=EXTERNAL AUDITORY CANAL
E= MASTOID AIR CELLS F= CEREBELLAR HEMISPHERES

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.
NORMAL ANATOMY…….
A=FRONTAL LOBE B= SYLVIAN FISSURE C=TEMPORAL LOBE
D=SUPRASELLAR CISTERN E=MIDBRAIN F=FOURTH VENTRICLE
G= CEREBELLAR HEMISPHERE

21.
NORMAL ANATOMY……..
A=FALX CEREBRI B=FRONTAL LOBE C=ANTERIOR HORN LAT VENTRICLE
D=THIRD VENTRICLE E=QUADRIGEMINAL PLATE CISTERN F=CEREBELLUM

22.
NORMAL ANATOMY……..
A=ANTERIOR HORN LAT VENTRICLE B=CAUDATE NUCLEUS C=ANT LIMB INT CAPSULE
D=GLOBUS PALLIDUS AND PUTAMEN E=POST LIMB INT CAPSULE F=THIRD VENTRICLE
G=QUADRIGEMINAL PLATE CISTERN H=CEREBELLAR VERMIS I=OCCIPITAL LOBE

23.
NORMAL ANATOMY……..
A=GENU OF CORPUS CALLOSUM B=ANT HORN OF LATERAL VENTRICLE C=INT CAPSULE
D=THALAMUS E=PINEAL GLAND F=CHOROID PLEXUS G=STARAIGHT SINUS

24.
NORMAL ANATOMY…….
A=FALX CEREBRI B=FRONTAL LOBE C=BODY OF LATERAL VENTRICLE
D=SPLENIUM OF CORPUS CALLOSUM E=PARIETAL LOBE F=OCCIPITAL LOBE
G=SUPERIOR SAGITTAL SINUS

25.
NORMAL ANATOMY……..
A=FALX CEREBRI B=SULCUS C=GYRUS D=SUPERIOR SAGGITAL SINUS

26.
1. Frontal bone
2. Superior frontal gyrus
3. Coronal suture
4. Precentral sulcus
5. Falx cerebri
6. Precentral gyrus
7. Parietal bone
8. Paracentral lobule
9. Central sulcus
10. Postcentral gyrus
11. Superior parietal lobule
12. Precuneus
13. Sagittal suture
14. Superior saggital sinus

27.
Frontal
bone
Falx cerebri
Central
sulcus
Parietal bone
Superior
saggital
sinus

28.
WHENEVER THE BRAIN SWELLS , THE GYRI
BECOME LARGER AND THE SULCI SHRINK

29.
BASICS….

30.
1. Frontal bone
2. Superior saggital sinus
3. Superior frontal gyrus
4. Coronal suture
5. Falx cerebri
6. Middle frontal gyrus
7. Longitudinal cerebral fissure
8. Precentral sulcus
9. Precentral gyrus
10. Central sulcus
11. Cerebral white matter (centrum
semiovale)
12. Postcentral gyrus
13. Paracentral lobule
14. Supramarginal gyrus
15. Parietal bone
16. Inferior parietal lobule
17. Precuneus
18. Parieto-occipital sulcus
19. Occipital bone

31.
CORONA RADIATA
CORPUS CALLOSUM

32.
2 Frontal sinus
5 Falx cerebri
6 Caudate nucleus (head)
9 Corpus callosum (genu)
11 Lateral ventricle
12 Third ventricle
13 Central sulcus
14 Precentral gyrus
15 Fornix
16 Postcentral gyrus
17 Interventricular foramen
(foramen of Monro)
18 Lateral sulcus
19 Claustrum
20 insular Cistern
22 Insula
23 Thalamus
25 Pineal gland
31 Vermis of cerebellum
32 Lateral ventricle (trigone
with choroid plexus)
33 Straight sinus
34 Middle temporal gyrus
37 Superior sagittal sinus
38 Occipital gyri

33.
Physiological calcifications

34.
2 Frontal sinus
3 Falx cerebri
7 Corpus callosum (genu)
13 External capsule
14 Putamen
15 Septum verum
(precommissural septum)
16 Cistern of lateral cerebral fossa
(insular cistern)
17 Hypothalamus
19 Third ventricle
20 Claustrum
21 Superior temporal gyrus
22 Extreme capsule
27 Hippocampus
28 Thalamus
30 Pineal gland (calcified)
31 Tentorium cerebelli
32 Quadrigeminal plate
33 Vermis of cerebellum
34 Quadrigeminal
and ambient cisterns
35 Straight sinus
37 Superior sagittal sinus
38 Lateral ventricle (trigone)

35.
1 Frontal sinus
2 Frontal bone
3 Falx cerebri
4 Orbital gyri
5 Straight gyrus
6 Anterior cerebral artery
7 Anterior communicating artery
8 Internal carotid artery
9 Superior temporal gyrus
10Mi ddle temporal gyrus
11 Middle cerebral artery
12 Posterior communicating
artery
13 Optic chiasm
14 Amygdaloid body
15 Pituitary stalk
16 Lateral ventricle (temporal
horn)
17 Dorsum sellae
18 Hippocampus
19 Pentagon of basal cisterns
20Infe rior temporal gyrus
21 Posterior cerebral artery
22 Parahippocampal gyrus
23 Tentorium cerebelli
24 Basilar artery and basal sulcus
25 Pons
26 Sigmoid sinus
27 Cerebellar peduncle (middle)
28 Fourth ventricle
29 Dentate nucleus
30V ermis of cerebellum (superior
part)
31 Temporal bone
32 Confluence of the sinuses
33 Cerebellar hemisphere
34 Transverse sinus
35 Occipital bone

36.
1 Frontal bone
2 Frontal sinus
3 Straight gyrus
4 Temporal muscle
5 Orbital gyri
6 Roof of orbit
7 Superior temporal gyrus
8 Optic nerve
9 Internal carotid artery
10Pi tuitary gland
11 Middle temporal gyrus
12 Dorsum sellae
13 Parahippocampal gyrus
14 Basilar artery
15 Lateral ventricle (temporal
horn)
16 Inferior temporal gyrus
17 Trigeminal nerve (V)
18 Trochlear nerve
19 Pontine cistern
20Mas toid antrum
21 Tentorium cerebelli
22 Fourth ventricle
23 Pons
24 Temporal bone
25 Cerebellar peduncle
26 Vermis of cerebellum
27 Sigmoid sinus
28 Cerebellar hemisphere
29 Dentate nucleus
30Occip ital sinus
31 Occipital bone
32 Semispinalis capitis muscle

37.
1 Nasal bone
2 Eyeball
3 Medial rectus muscle
4 Nasal septum
5 Ethmoidal cells
6 Zygomatic bone
7 Pterygopalatine fossa
8 Inferior rectus muscle
9 Occipital bone (basilar part)
10T emporal muscle
11 Foramen ovale with
mandibular nerve
12 Sphenoidal sinus
13 Temporal bone (apex of the
petrous pyramid)
14 Zygomatic arch
15 Internal carotid artery
16 Masseter muscle
17 Jugular vein (bulb)
18 Lateral pterygoid muscle
(superior head)
19 External auditory meatus
20Auditor y tube
21 Medulla oblongata
22 Head of mandible
23 Mastoid process
24 Foramen lacerum
25 Sigmoid sinus
26 Vertebral arteries
27 Petro-occipital fissure
28 Flocculus
29 Cerebellar tonsil
30Dig astric muscle
31 Splenius capitis muscle
32 Cerebellar hemisphere (caudal lobe)
33 Rectus capitis posterior minor muscle
34 Cisterna magna (posterior cerebellomedullary
cistern)
35 Rectus capitis posterior major muscle
36 Occipital bone
37 Semispinalis capitis muscle
38 Trapezius muscle

38.
medulla
Cerebellar
hemisphere Cisterna
magna

39.
THANKS

40.
1. Frontal bone
2. Superior frontal gyrus
3. Falx cerebri
4. Middle frontal gyrus
5. Cingulate sulcus
6. Coronal suture
7. Pericallosal artery
8. Precentral gyrus
9. Corona radiata
10. Central sulcus
11. Corpus callosum
12. Postcentral gyrus
13. Lateral ventricle(choroid plexus)
14. Postcentral sulcus
15. Parietal bone
16. Supramarginal gyrus
17. Precuneus
18. Angular gyrus
19. Parieto-occipital sulcus
20. Occipital gyri
21. Cuneus
22. Occipital bone
23. Superior saggital sinus