1. Dr Mohamed el Safwany, MD.
CT BRAIN - BASICS
Dr Mohamed el Safwany, MD.

2. Intended learning outcome
The student should learn at the end of this lecture CT brain basics.

3. CT Principle
RING OF XRAY DETECTORS

4. Frankfurt plane

5. HOUNSFIELD UNITS Numeric information in each pixel of ct image
Related to composition & nature of tissue
Represent the density of tissue
Also called as CT NUMBER

6. air
fat
---70
Pure water
Csf +8
White matter
+30
Gray matter
+45
blood
+70
Bone/cacification
+1000

7. CT /MRI CT PICTURE MR PICTURE
WHITE MATTER IS DARKER THAN GREY MATTER SINCE LIPID CONTAINING MATERIAL IS RADIOLUCENT
CSF IS BLACK
MR PICTURE
GREY MATTER
T1WI
DARK
T2WI
BRIGHT
WHITE MATTR
CSF
GREY TO DARK
WHITE

8. Step wise approach Ventricles/ cisterns Cortex Deep gray matter
Focal lesions
Bone
Extracranial soft tissue
Para nasal sinuses

9. LV 3V FORAMEN OF MONRO 4 V FRONTAL HORN trigone OCCIPITAL HORN
TEMBORAL HORN
4 V
AQUEDUCT OF SYLVIUS

10. COMMON SECTIONS AXIAL SECTIONS CORONAL SECTIONS SAGITTAL SECTIONS
POSTERIOR FOSSA CUTS
-ABOVE THE FORAMEN MAGNUM LEVEL
-LEVEL OF THE FOURTH VENTRICLE
-ABOVE THE FOURTH VENTRICULAR LEVEL
- TENTORIAL
SUPRATENTORIAL CUTS
-THIRD VENTRICULAR LEVEL
-LOW VENTRICULAR LEVEL
-ABOVE THE VENTRICULAR LEVEL
-FRONTAL HORN LEVEL
-THIRD VENTRICULAR LEVEL
-MID VENTRICULAR LEVEL
-OCCIPITAL HORN LEVEL
-MID SAGITTAL LEVEL
-PARASAGITTAL LEVEL THROUGH THE LATERAL VENTRICULAR BODY
-LATERAL ORBITAL LEVEL

11. ABOVE THE LEVEL OF FORAMEN MAGNUMVA
MEDULLA
4 V
TONSIL
INT OCC PROT

12. LEVEL OF FOURTH VENTRICLE
Optic nerve
CPCISTERN
TEM HORN
PONS 4V
MCP

13. 4V LEVEL ABOVE FOURTH VENTRICLE vermis SUPRA SELLAR CISTERN OLF SULCUS
SYLV FISSURE
SUPRA SELLAR CISTERN
AMB CIST MB 4V
vermis

14. THIRD VENTRICULAR LEVEL

15. LOW VENTRICULAR

16. Above ventricle level

17. Cerebral Arterial Territory
MCA-most of lateral hemisphere, Basal ganglia, insula,
ACA-Inferomedial basal ganglia,ventromedial frontal lobes, anterior 2/3rd medial cerebral hemispheres, 1 cm supero medial brain convexity
PCA-Thalami, midbrain, posterior 1/3of medial hemisphere, occipital lobe, postero medial temporal lobe

18. ACA
MCA
PCA

19. AICA- inferolateral part of pons, middle cerebellar peduncle, floccular region, anterior petrosal surface of cerebellar hemisphere
PICA-posteroinferior surface of cerebellar hemisphere , ipsilateral part of inferior vermis,
Superior cerebellar artery-superior aspect of cerebellar hemisphere (tentorial surface), ipsilateral superior vermis, largest part of deep white matter including dentate nucleus, pons

21. Water shed infarct

22. CEREBRAL ISCHEMIA

23. Cerebral ischemia
Significantly diminished blood supply to all parts(global ischemia) or selected areas(regional or focal ischemia) of the brain
Focal ischemia- cerebral infarction
Global ischemia-hypoxic ischemic encephalopathy(HIE),hypotensive cerebral infarction

24. Goal of imaging Exclude hemorrhage
Identify the presence of an underlying structural lesion such as tumour , vascular malformation ,subdual hematoma that can mimic stroke
Identify stenosis or occlusion of major extra- and intracranial arteries
Differentiate between irreversibly affected brain tissue and reversibly impaired tissue (dead tissue versus tissue at risk)

25. Infarct vs pneumbra
In the central core of the infarct, the severity of hypoperfusion results in irreversible cellular damage .
Around this core, there is a region of decreased flow in which either:
The critical flow threshold for cell death has not reached
Or the duration of ischemia has been insufficient to cause irreversible damage.

27. Hyper acute infarct(<12 hours)
Subacute infarct( days)
Chronic infarct(>2 weeks)
Old infarct(>2 months)

28. CT-Hyperacute infarct
Hyperdense MCA sign-acute intraluminal thrombus
Attenuation of lentiform nulei
Dot sign-occluded MCA branch in sylvian fissure
Insular ribbon sign –grey white interface loss along the lateral insula

29. Dense mca sign

30. ‘ loss of insular ribbon’

31. M C A DOT SIGN

32. ATTENUATION OF LENTICULAR NUCLEUS

33. CT- Acute infarct Low density basal ganglia Sulcal effacement
Wedge shaphed parenchymal hypo density area that involves both grey and white matter
Increasing mass effect
Hemorrhagic transformation may occur -15 to 45% ( basal ganglia and cortex common site) in 24 to 48 hours

34. CT-chronic infarct Plain ct
Focal, well-delineated low-attenuation areas in affected vascular distribution
sulci become prominent; ipsilateral ventricle enlarges
Dystrophic Ca++ may occur in infarcted brain but is very rare
CECT: No enhancement

35. INFARCT / TUMOUR CLINICAL HISTROY DISTRIBUTION SHAPES
GRAY / WHITE INVOLVEMENT
ADVANCED IMAGING

36. VENOUS INFARCT HISTROY BEYOND VASCULAR DISTRIBUTION
HAEMORRHAGIC INFARCT
THORMBUS IN VENOUS SINUSES
SYMMETRICAL LOW ATTENUATION IN DEEP GRAY MATTER - DEEP CEREBRAL VEIN THORMBUS

37. EDEMA/ INFARCT INFARCT TYPICAL VASCULAR DISTRIBUTION
GRAY MATTER INVOLVEMENT
EDEMA
NOT CONFINED TO VASCULAR DISTRIBUTION
MOSTLY INVOLVES WHITE MATTER

38. PCA INFARCT

39. MCA INFARCT

40. ACA INFARCT

41. WATERSHED INFARCT

42. Old infarct

43. H’gic infarct

44. Text Book David Sutton’s Radiology
Clark’s Radiographic positioning and techniques

45. Assignment
Two students will be selected for assignment.

46. Question
Describe CT of acute brain infarction?

47. Thank u