1. Dr Mohamed El Safwany. MD.
How to Read a Head CT
Dr Mohamed El Safwany. MD.

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

3. Head CT
Has assumed a critical role in the daily practice of Emergency Medicine for evaluating intracranial emergencies. (e.g. Trauma, Stroke, SAH, ICH).
Most practitioners have limited experience with interpretation.
In many situations, the Emergency Physician must initially interpret and act
on the CT without specialist assistance.

4. Head CT
“Blood Can Be Very Bad”

5. Blood Can Be Very Bad
Blood
Cisterns
Brain
Ventricles
Bone

6. Blood Can Be Very Bad
Blood
Cisterns
Brain
Ventricles
Bone

7. Blood Can Be Very Bad
Blood
Cisterns
Brain
Ventricles
Bone

8. Blood Can Be Very Bad
Blood
Cisterns
Brain
Ventricles
Bone

9. Blood Can Be Very Bad
Blood
Cisterns
Brain
Ventricles
Bone

10. CT Scan Basics
A CT image is a computer-generated picture based on multiple x-ray exposures taken around the periphery of the subject.
X-rays are passed through the subject, and a scanning device measures the transmitted radiation.
The denser the object, the more the beam is attenuated, and hence fewer x-rays make it to the sensor.

11. CT Scan Basics The denser the object, the whiter it is on CT
Bone is most dense = Hounsfield U.
Air is the least dense = H Hounsfield U.

12. CT Scan Basics: Windowing
Focuses the spectrum of gray-scale used on a particular image.

13. 2 Sheet Head CT

14. Posterior Fossa Brainstem Cerebellum Skull Base Clinoids Petrosal bone
Sphenoid bone
Sella turcica
Sinuses

15. CT Scan

16. CT Scan

17. 2nd Key Level Sagittal View
Circummesencephalic Cistern

18. Cisterns at Cerebral Peduncles Level

19. CT Scan

20. CT Scan

21. 3rd Key Level Sagittal View
Circummesencephalic Cistern

22. Cisterns at High Mid-Brain Level

23. CT Scan

24. CSF Production
Produced in choroid plexus in the lateral ventricles  Foramen of Monroe  IIIrd Ventricle  Acqueduct of Sylvius  IVth Ventricle  Lushka/Magendie
0.5-1 cc/min
Adult CSF volume is approx. 150 cc’s.
Adult CSF production is approx cc’s per day.

25. 1 day year years 25
Andrew D. Perron, MD, FACEP

26. B is for Blood 1st decision: Is blood present?
2nd decision: If so, where is it?
3rd decision: If so, what effect is it having?

27. B is for Blood Acute blood is bright white on CT (once it clots).
Blood becomes isodense at approximately 1 week.
Blood becomes hypodense at approximately 2 weeks.

28. B is for Blood Blood becomes hypodense at approximately 2 weeks.
Acute blood is bright white on CT (once it clots).
Blood becomes isodense at approximately 1 week.
Blood becomes hypodense at approximately 2 weeks.

29. B is for Blood Blood becomes hypodense at approximately 2 weeks.
Acute blood is bright white on CT (once it clots).
Blood becomes isodense at approximately 1 week.
Blood becomes hypodense at approximately 2 weeks.

30. CT Scans

31. Subdural Hematoma Typically falx or sickle-shaped.
Crosses sutures, but does not cross midline.
Acute subdural is a marker for severe head injury. (Mortality approaches 80%)
Chronic subdural usually slow venous bleed and well tolerated.

32. Subarachnoid Hemorrhage

33. Subarachnoid Hemorrhage
Blood in the cisterns/cortical gyral surface
Aneurysms responsible for 75-80% of SAH
AVM’s responsible for 4-5%
Vasculitis accounts for small proportion (<1%)
No cause is found in 10-15%
20% will have associated acute hydrocephalus

34. CT Scan 34

35. CT Scan 35

36. Intraventricular/ Intraparenchymal Hemorrhage

37. CT Scan 37

38. C is for CISTERNS (Blood Can Be Very Bad) 4 key cisterns
Circummesencephalic
Suprasellar
Quadrigeminal
Sylvian
Circummesencephalic

39. Cisterns 2 Key questions to answer regarding cisterns: Is there blood?
Are the cisterns open?

40. 40

41. 41
Andrew D. Perron, MD, FACEP

42. B is for BRAIN
(Blood Can Be Very Bad)

43. 43

44. Tumor 44

45. Atrophy 45

46. Abscess 46

47. Hemorrhagic Contusion47

48. Mass Effect 48

49. Intracranial Air 49

50. Intracranial Air 50

51. 51

52. 52

53. 53

54. 54

55. 55
Andrew D. Perron, MD, FACEP

56. Blood Can Be Very Bad
If no blood is seen, all cisterns are present and open, the brain is symmetric with normal gray-white differentiation, the ventricles are symmetric without dilation, and there is no fracture, then there is no emergent diagnosis from the CT scan.

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

58. Assignment
Two students will be selected for assignment.

59. Question
Define differences between subdural and epidural hematoma?

60. Thank You