1) The document discusses imaging protocols for acute ischemic stroke, including non-contrast CT (NCCT), CT angiography (CTA), MRI, and thrombectomy procedures. 2) NCCT can help identify hemorrhage as a contraindication to thrombolysis and detect early ischemia. CTA can demonstrate thrombi to guide thrombolysis or thrombectomy and assess vessel occlusion, core infarction, and collaterals. 3) MRI is more sensitive than CT for acute stroke, detecting most infarcts by 24 hours. Diffusion-weighted imaging (DWI) is most sensitive in the first few hours. Perfusion imaging assesses penumbra. 4) For severe strokes,

1. IMAGING IN ACUTE ISCHEMIC STROKE
Mr. Alwine Anto
2nd year BSc Radiography student
Dept of Neuro Imaging and Interventional Radiology
NIMHANS
Bengaluru

2. INTRODUCTION
 Stroke is defined as an acute central nervous
system injury with abrupt onset.
Can be of the following 2 types
 Ischemic
 Hemorrhagic
Approximately 80% of all strokes are due to acute
ischemia
 Hyper acute
 Early - < 6 hrs
 Late – 6 – 24 hrs
 acute --- 24 hours-1week
 Sub acute --- 1-3 weeks
 Chronic --- more than 3 weeks

3. ACUTE CVA IMAGING PROTOCOL

4. NCCT
 Widely available.
 Can be done quickly.
 It not only can help identify a
hemorrhage (contraindication to
thrombolytic therapy),
but it also can help detect early-stage acute
ischemia by
depicting features such
 Hyperdense vessel sign.
 Obscuration of the lentiform nucleus
 Insular ribbon sign.
 Hypoattenuating brain tissue
 Sulcal effacement

5. CT ANGIOGRAPHY
• CT angiographic demonstration of a
significant thrombus can guide
appropriate therapy in the form of
intraarterial thrombolysis or mechanical
thrombectomy
Benefits of CTA:
• Presence of large vessel occlusion(LVO)
• Core on CTA source image
• Collateral circulation assessment
• Arch anatomy – facilitate DSA
• Other – unstable aortic thrombus
• arterial dissections
CTA PROTOCOL
Coverage : aortic arch to circle of willis
Scanning parameters : 120 kV, 260 mAs
Scanning delay : dependent on ROI placed
over aortic arch to detect contrast medium
bolus
Contrast medium dose : 60-70 ml of
nonionic contrast medium at the rate of 3-4
ml/sec by preessure injector
Slice thickness : 0.625 mm
• Delayedscanfromskullbaseshould betakento
checkforcollateralsupply.

6. MRI IN ACUTE STROKE
MRI IMAGING FOR ACUTE STROKE
CONVENTIONAL
MRI
MRI DIFFUSION
STUDIES
MR
ANGIOGRAPHY
MR PERFUSION
STUDIES

7. CONVENTIONAL MRI
 SPIN ECHO IMAGES
MORE SENSITIVE AND
SPECIFIC THAN CT IN
ACUTE CVA
 SEQUENCES
 FLAIR
 SWI
 DWI
 T2
 Signs on MRI
 Hyper on T2 and FLAIR
 Loss of gray white matter
differentiation
 Sulcal effacement
 Mass effect
 Loss of flow void in T2WI in vessel
 Blooming in SWI
 Less sensitive than DWI in first few
hours
These sequences detect 80% of infarction before 24 hours.
They may be negative up to 2-4 hours post ictus, FLAIR hyperintensity -- 6 hours

8.  Based on the principle of
Brownian motion
 A DWI sequence is most
often acquired using a T2
weighted EPI sequence.
 Acute stroke causes excess
intracellular water
accumulation or “cytotoxic
edema”, with an overall
decreased rate of water
molecular diffusion within
the affected tissue.
 Thus appear bright on DWI
and shows restriction
DWI (DIFFUSION WEIGHTED IMAGING)
 Increasing the b-value increases
the sensitivity to the motion
(diffusion) of extra-cellular
water in tissue and thus
increases the diffusion
weighting . Increase b value for
posterior fossa infarct

9. MRA ( MR ANGIOGRAPHY )
 Sensitive for intravascular
thrombus.
 Bright blood imaging is the
golden standard for imaging in
acute stroke such as TOF MRA
and CE MRA.
 MR angiogram in a patient with
acute stroke symptoms reveal
flow gaps in the basilar artery.
Findings were due to
intravascular thrombus.
3D TOF
• Based on the inflow effect of blood
vessels with the use of GRE sequence
• TR=25-50 ms
• Flip angle =20°- 30°
• TE=min
CE-MRA
• Based on the use of GRE sequence
where gadolinium contrast is injected
along with the flush of saline by
injector at the rate of 2.5ml/sec

10.  DWI  Depicts irreversibly damaged infarct
 PWI  Reflects the complete areaof hypoperfusion
 The volume difference between these two, the PWI/DWI mismatch would be
the PENUMBRA
 If there is no difference in PWI and DWI, no penumbra is present
DWI V/S PWI

11. THROMBECTOMY
• A small proportion of severe ischaemic strokes can be treated by an
emergency procedure known as thrombectomy. This removes blood
clots and helps restore blood flow to the brain.
• Accessed using a large guide catheter – 6F Neuron Max as distally as
possible into ICA
• Large bore aspiration reperfusion catheter – ACE 68(PENUMBRA) is
inserted.
• Advanced over a 3 MAX microcatheter and Traxcess micro guidewire
combination
• Aspiration catheter advanced just proximal to thrombus and
connected to aspiration pump.
• Thrombus is withdrawn for 60-90 seconds with aspiration pump
“ON”
• Thrombectomy is done by two techniques-aspiration technique and
stentriever technique.

14. ADVANTAGES OF THE TECHNIQUE
• Large bore catheter
• so greater suction force for clot aspiration
• Use of stent retriever may be done through it
• Recent catheters -- More flexible; less traumatic
• Less technically demanding
• Time to recanalisation – reduced
• Less chance of fragmentation and distal emboli
• Aspiration - no traction of artery; less dissection

15. RADIOGRAPHER’S ROLE IN STROKE RESPONSE TEAM
• PLAIN CT TO BE DONE IN SPIRAL OR HELICAL TECHNIQUE.
• CALL THE DUTY RADIOLOGIST.
• ENQUIRE/CONFIRM TIME OF ONSET FROM PATIENT/PATIENT PARTY.
• CT ANGIOGRAPHY TO BE DONE. TIME TO DO CTA< 20MIN.
• CREATININE NOT NEEDED FOR CT ANGIOGRAPHY. (AHA GUIDELINES 2018)
• IV LINE ACCESS FROM RIGHT HAND - REDUCE ARTIFACT.
• BOLUS TRACKING TECHNIQUE SHOULD BE USED FOR CTA –BECAUSE
PATIENTS HAVE DIFFERENT HEART RATE.
• DELAYED SCAN HAS TO BE TAKEN IMMEDIATELY TO CHECK FOR COLLATERALS.
• THICK CONTINOUS MIP RECONS TO BE DONE UNDER 3-5MM. (CONTINOUS).
• MRI –DWI,FLAIR,SWI,PERFUSION TO BE DONE . MRA IF DECIDED BY THE
RADIOLOGIST.
DSA
• CHECK THE MACHINE.
• MATERIALS /INVENTRY TAKEN OUT.
• SHIFTING AND PREPARING PATIENT ALONG WITH THE RADIOLOGIST.
• CHECK AND PREPARE SUCTION PUMP.

16. PATIENT - 8 JULY
• 35/M C/O SUDDEN ONSET WEAKNESS OF LEFT UPPER AND
LOWER LIMB
• TIME – SINCE 6 PM ON 8 JULY

17. CT + CTA
8:47 PM

18. 8:47PM

19. DSA
PATIENT SHIFTED IN AT 10:30PM
PUNCTURE – 10:35PM

20. MRI – POST PROCEDURE

22. THE FUTURE
 Selection of patients for mechanical thrombectomy
may be made more effectively by performing
appropriate imaging studies rather than relying on
the time of onset as the sole determinant of
selection.
 Mechanical thrombectomy is an option for patients
with a large vessel occlusion by a long thrombus
causing a severe stroke.
 Image wisely to save lives for the patients who are in
ischemic stroke and a protocol must be set in
hospital when dealing with ischemic stroke.

23. BIBLIOGRAPHY
• www.radiopedia.org
• www.mriquestions.com
• MRI IN PRACTICE – CATHERINE WESTBROOK
• ARTICLES FROM RADIOGRAPHICS
• AHA (AMERICAN HEART ASSOCIATION) GUIDELINES - 2018

24. Thank you