Acute central nervous system injury with abrupt onset Mechanism: • Interruption of blood flow(Ischemic Stroke) or • Bleeding into or around the brain(Hemorrhagic stroke)

1. Imaging In Acute Stroke

2. Stroke
Acute central nervous system injury with abrupt
onset
Mechanism:
• Interruption of blood flow(Ischemic Stroke)
or
• Bleeding into or around the brain(Hemorrhagic
stroke)

3. Stroke Types
Most common stroke etiologies:
1) Cerebral Infarction 80%
2) Primary Intracranial Hemorrhage 15%
3) Non traumatic subarachnoid hemorrhage
5%

4. Symptoms in stroke
• Transient Ischemic Attacks
• A transient ischemic attack (TIA) is a reversible
episode of focal neurologic dysfunction that
typically lasts anywhere from a few minutes to a
few hours. Attacks are usually caused by tiny
emboli that lodge in an artery and then quickly
break up and dissolve, with no residual damage.
• Clinical presentation of TIAs varies slightly
depending on whether the carotid or basilar
artery is involved

5. Symptoms of TIAs in the Carotid
Arteries
• Reduction of oxygen to the eye ,,, visual effect
“shade being pulled down.”
• Poor night vision.
• When the cerebral hemisphere is affected, the
patient may experience problems with
speech, partial and temporary paralysis,
tingling, and numbness, typically on one side
of the body.

6. Symptoms of TIAs in the Basilar
Artery
• Symptoms often occur on both sides of the body and
include the following:
– Temporarily dim, gray, blurry, or lost vision in both eyes
– Tingling or numbness in the mouth, cheeks, or gums
– Headache in the back of the head
– Dizziness
– Nausea and vomiting
– Difficulty swallowing
– Inability to speak clearly
– Weakness in the arm and legs, sometimes causing a
sudden fall

7. Symptoms of a Major Ischemic Stroke
• Onset: variable depending on the source.
• unilateral weakness, loss of feeling on one side of
the face or in an arm or leg, or blindness in one
eye.
• If the left hemisphere of the brain is affected,
speech problems often occur.
• inability to express thoughts verbally or
understand spoken words.
• The victim may experience major seizures and
possibly coma.

8. Symptoms of Hemorrhagic Stroke
• Depend, to some extent, on where and how the hemorrhage occurs.
• Cerebral hemorrhage
– usually begin very suddenly and evolve over the course of several
hours.
– They include headache, nausea and vomiting, and altered mental
state.
• SAH
– may produce warning signs from the leaky blood vessel a few days to a
month before the aneurysm fully develops and ruptures.
• abrupt headaches, nausea and vomiting, and sensitivity to light.
– When the aneurysm ruptures,
• terrible headache; neck stiffness; vomiting; an altered state of consciousness; eyes
that become fixed in one direction or a loss of vision; or stupor, rigidity, and even
coma.

9. Radiological Tests
CT:
w/ or w/o contrast
CT angiogram (CTA)
MR:
w/ or w/o contrast
T1 or T2 weighted (T1WI, T2WI)
FLAIR
Diffusion weighted image (DWI) Susceptibility(very important)
MR angiogram
Cerebral Angiogram

10. ISCHEMIC INFARCT

11. Goal of imaging
• Establish diagnosis fast(exclude hemorrhage)
• Obtain accurate information regarding intracranial
vasculature and brain perfusion
• Appropriate therapy(In case of infarction tPA
inclusion)

12. 4 Ps of Acute Stroke Imaging
• Parenchyma:
– Assess early sign of acute stroke, rule out hemorrhage
(unenhanced CT)
• Pipes:
– Assess extracranial circulation (carotid and vertebral
arteries of the neck)
– Assess intracranial circulation for evidence of intravascular
thrombus
• Perfusion:
– Assess Cerebral blood volume, cerebral blood flow, and
mean transit time
• Penumbra:
– assess tissue at risk of dying if ischemia continues without
recanalization of intravascular thrombus

13. PENUMBRA
a core of irreversibly infracted tissue surrounded
by a peripheral region of ischemic but salvageable tissue referred to as a
penumbra. Without early recanalization,
the infarction gradually expands to include the penumbra.

14. CT EARLY SIGN
• Hypo attenuating brain tissue
• Obscuration of lentiform nucleus
• Dense MCA sign
• Insular ribbon sign
• Loss of sulcal effacement

15. Hypo attenuating brain tissue
• MCA infarction: on CT an
area of hypo attenuation
appearing within six
hours is highly specific for
irreversible ischemic brain
damage

19. Obscuration lentiform nucleus
Axial unenhanced CT image
shows hypo attenuation and
obscuration of the left
lentiform nucleus (arrows),
which, because of acute
ischemia in the lenticulostriate
distribution, appears abnormal
in comparison with the right
lentiform nucleus.

21. Insular ribbon Sign
Axial unenhanced CT image,
showsL:
• hypo attenuation and
obscuration of the
posterior part of the right
lentiform nucleus (white
arrow)
• and a loss of GM–WM
definition in the lateral
margins of the right insula
(black arrows)………..
insular ribbon sign.

23. Insular ribbon Sign

24. Dense MCA sign
This is a result of thrombus or embolus in the MCA.
On the left a patient with a dense MCA sign.
On CT-angiography occlusion of the MCA is visible.

26. Dense MCA sign
(a) Unenhanced CT shows
hyper attenuation in a
proximal segment of the
left MCA (arrows).
(b, c) Axial (b) and coronal (c)
reformatted
images from CT
angiography show the
apparent absence of the
same vessel
segment(arrows

27. Hemorrhagic infarcts
• 15% of MCA infarcts are initially hemorrhagic.

30. CTA and CT Perfusion
• Once we have diagnosed the infarction, we
want to know which vessel is involved by
performing a CTA.

31. CTA
• Insular ribbon sign in
right insular cortex
• CTA disclose
thrombus in rt. MCA

32. CT Perfusion (CTP)
• With CT and MR imaging we can get a good impression of the
area that is infracted.
• but we cannot preclude a large ischemic penumbra (tissue at
risk).
• With perfusion studies we monitor the first pass of an
iodinated contrast agent bolus through the cerebral
vasculature.
• Perfusion will tell us which area is at risk.
• Approximately 26% of patients will require a perfusion study
to come to the proper diagnosis.

33. • CT perfusion provides qualitative and quantitative evaluation
of cerebral perfusion.
• by calculating regional blood flow (rCBF) and regional blood
volume (rCBV) and mean transit time (MTT).
• Adv:
– widespread availability of CT scanners,
– their high image quality,
– and relatively low costs.
– In addition, simply extending the routine CT examination
eliminates time-consuming transport of patients between
CT and MR scanners that serves to further delay
treatment.

34. Radiographic features
• The key to interpreting CT perfusion in the
setting of acute ischemic stroke is
understanding and identifying the infarct core
and the ischemic penumbra, as a patient with
a small core and a large penumbra is most
likely to benefit from reperfusion therapies.

35. • The three parameters typically used in
determining these two areas are:
• mean transit time (MTT) or time to peak
(TTP)of the deconvolved tissue residue
function (Tmax) 3
• cerebral blood flow (CBF)
• cerebral blood volume (CBV)

36. Normal perfusion parameters
Gray matter
• MTT: 4 s
• CBF: 60 ml/100 g/min
• CBV: 4 ml/100 g
White matter
• MTT: 4.8 s
• CBF: 25 ml/100 g/min
• CBV: 2 ml/100 g

37. Infarct core
• Is the part of the ischemic
brain which has already
infarcted or is destined to
infarct regardless of
therapy.
• It has
– increased MTT/Tmax
– markedly decreased CBF
– markedly decreased CBV
Ischemic penumbra
• The area which in most
cases surrounds the infarct
core = salvageable ischemic
brain tissue.
• It has
– increased MTT/Tmax
– moderately reduced CBF
– near normal or increased CBV

38. Large
Mismatch
between
DWI and MTT

39. MGH Single Slab Perfusion Protocol
• Perfusion (single slab, cine)
– 80 kVp 200 mA, 1 second rotation, 8 x 5 mm slices
– Phase I (cine): 1 image every second for 40s (0.5s recon
interval)
– Phase II (axial): 1 image every 3 seconds for 27 s
– Total duration = 67 s
– Total X-ray exposure = 49 s
• CTDI vol=470 mGy
• DLP =1890 mGy-cm (dose length priduct=CTDIvolxscan length)
• CTP protocol well within the 0.5 Gy CTDI (vol)
• Further 25% reduction with 150mA

41. CTP Dose
• Low kVp is desirable
– 80 kVp standard
– Less radiation dose
– More iodine conspicuity
• Low mAs is sufficient
– <200
– As low as 100;
• Epilation threshold (hair loss)
– ~ 3-7 Gy, ~ 3 wk delay (temporary), >7Gy,, permenant
– If CTP is 8x the .5 Gy max, dose at least 4 Gy!

45. CT Perfusion (CTP)
• The limitation of CT-perfusion is the limited
coverage.

46. NECT, CTP and CTA
• Study demonstrates that Plain CT, CTP and CTA
can provide comprehensive diagnostic
information in less than 15 minutes, provided
that you have a good team.

47. NECT, CTP and CTA
• CT is normal but patient
is symptomatic
• CTP shows a perfusion
defect
• CTA was subsequently
performed and a
dissection of the left
internal carotid was
demonstrated.

48. Selection for t-PA (Tissue Plasminogen Activator) therapy
• No evidence of :
– Hemorrhage
• EDH/SDH
• IPH
• SAH
– Non-stroke etiology
• Tumor
• Abscess
• Trauma

49. Hemorrhagic Stroke
• Intracranial haemorrhage is a collective term
encompassing many different conditions
characterized by the extra vascular
accumulation of blood within different
intracranial spaces.

50. Cranial CT Scanning and Hemorrhage
• First line imaging study in
suspected stroke patients
– Exquisite sensitivity for the
detection of blood
– Widely available in hospitals
– So our focus is CT

51. Hemorrhagic Stroke
• Intra-axial haemorrhage
– intracerebral haemorrhage
– basal ganglia haemorrhage
– lobar haemorrhage
– pontine haemorrhage
– cerebellar haemorrhage
• Intraventricular haemorrhage (IVH)
• extra-axial haemorrhage
– extradural haemorrhage (EDH)
– subdural haemorrhage (SDH)
– subarachnoid haemorrhage (SAH)

52. Intracerebral Hemorrhage
• Large intracerebral
hemorrhage with midline
shift

53. ICH with Intraventricular Extension

54. Basal Ganglia Hemorrhage with IC
extension

55. Lobar intracerebral hemorrhage.

56. Pontine Hemorrhage

57. Cerebellar Hemorrhage

58. Subarachnoid Hemorrhage

59. Non Traumatic Subdural Hematoma
• Acute subdural
hematoma. Note the
bright (white) image
properties of the blood on
this non contrast cranial
CT scan. Note also the
midline shift.

60. THANX