Stroke Dr.amarnath

8/3/2019 Stroke Dr.amarnath

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IMAGING IN ISCHEMICSTROKE

DR.C.AMARNATH,MD,DNB,FRCR

ASSOCIATE PROFESSOR & HOD,STANLEY MEDICAL COLLEGE

Consultant radiologist, SCANS WORLD


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ACKNOWLEDGEMENTS

ORGANISERS


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Sudden onset of neurological deficit

caused by impaired blood supply to the

brain

Defining stroke


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STROKETypes of Ischemic Stroke

1. TIA Transient Ischemic Attack

A sudden neurological disturbance lasting for more than 15

minute but with complete resolution with in 24 hours.

35% of these patients may develop major stroke in 12 months

of initial incident

2. RIND reversible Ischemic Neurological Deficit RIND is a deficit

that persist for more than 24 hours but complete recovery

within 3 weeks

3. PRIND Progressive Reversible Ischemic Neurological Deficit

4. Stroke in evolution

5. Complete Stroke


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STROKEOccurrence Rate according to the Type

Ischemic Stroke

83-85%

Hemorrhagic Stroke

15-17%

Thrombotic

51.5%

Embolic

31.5%

Intracerebral

Hemorrhage

10%

Subarachnoid

Haemorrhage

7%

All Stroke 100%


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STROKE ETIOLOGIES :

TYPE OF STROKE PERCENT (% )

INFARCTION (80 % )

large vessel occlusion 40-50

small vessel (lacunar ) infarcts 25

Cardio-embolic 15

Blood disoders 5Vasculitis 5

PRIMARY ICH (15 % )

HTN 40-60

amyloid 15-25vascular malformations 10-15

NON-TRAUMATIC SAH (5 % )

aneurysm 75-80

vascular malformation 10-15

Non-aneurysmal SAH 5-15


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DIFFUSION / PERFUSION MISMATCHDIFFUSION / PERFUSION MISMATCH

Modified from Kidwell et al. Stroke 2003

ml/100g

m/minRegional CBF 55

GM 65-75

WM 15-20

Electricaldysfunction 10-20

Neuronal

death


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Pathophysiology:Pathophysiology:

Ischemic penumbraIschemic penumbra the area surrounding the primary injury CBF is 10-20 ml/100g of brain/min

Electrical silence but irreversible damage has

not yet occurred Animal studies:

reversible neurologic deficit if cerebral vesselocclusion lasts less than 2h

after 6h of occlusion: irreversible neurologic deficit Thus the 2-6 hour therapeutic window for

thrombolysis


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The ischemic brain

Central infarcted core dead non salvageable tissue

Penumbra surrounding salvageable stunned brain tissue

Time is Brain ` < 3 hours postictus

IV thrombolysis

`3- 6(?9) hours postictus

IA thrombolysis

` > 6(?9) hours postictus

Usually not a

thrombolysis candidate


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Hyperacute -0-6 hrs

Acute 6-24 hrs Subacute 24 hrs 2 weeks

Chronic - > 2 weeks

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Stroke characterization-time


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ACUTE STROKE IMAGINGACUTE STROKE IMAGING

PRIMARY GOAL :

1.STROKE TYPE ?

2.STROKE MIMIC ?

SECONDARY GOAL :1.PROGNOSTIC .

2.ISCHAEMIC VIABLE TISSUE VS INFARCTED TISSUE

3.DETECTION & LOCALIZATION OF ARTERIAL OCCLUSION .

FOR PATIENT SELECTIONINDIVIDUALIZE Tt

EXTEND THERAPEUTIC WINDOW

IMPROVE Tt OUTCOME .


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Techniques CT - MRI

Nonenhanced CT

CT perfusion

CT Angiography

Conventional MR

GRE

Diffusion MR

Perfusion MR

MRA

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Non contrast CT

Primary imaging modality

To reveal early direct or indirect signs of

brain infarction To exclude lesions that mimic stroke

intracranial hemorrhage, subdural

hematoma, cerebritis, migraine, tumorsSensitivity 45 - 88% (mean 55.3%)


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ACUTE INFARCTS

HYPERACUTE (


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Insular ribbon sign

F, 732 hours


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Obscuration of lentiform nuclei

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Non enhanced CTEarly ischemic

changes


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Hyper dense MCA/vessel sign

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Non enhanced CTEarly ischemic

changes


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Disappearing basal ganglia sign

Caused by MCA

M1 segment

occlusion

proximally tolenticulostriate

arteries


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Disappearing basal ganglia sign

F,58, 6 hours

Setting of variable window width to accent the graywhite matter contrast

window width80 HU

center level 20

HU

W 8 HU

C 32 HU

Narrow

window


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Quantification of ischemia-

The ASPECTS systemEach MCA region score 1

Deduct one score for each region involved

ALBERTA STROKE PROGRAMME EARLY CTSCORE


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Quantification of ischemia-

The ASPECTS systemDiffuse ischemia score 0

Normal score 10


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SUBACUTE INFARCTS


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STROKE OR TUMOUR

Sudden onset

Grey and white matter

involved

Wedge shaped

Typical distribution

Gradual onset

Preferentially involves

white matter

Round/infilterating

Not confined to any

vascular territory


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CTA-MCA occlusion

Vessel occlusion or cutoff related to

thromboemboli

Delayed (antegrade) flow


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CTA ICA stenosis


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CTA-Aneurysm MCA


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CT Perfusion -Technique


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CT Perfusion

rMTT(sec)

> 145%

aCBV

(ml/100g)

< 2.0


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CT perfusion

Advantages : Quantification and resolution

Arterial input function

Disadvantages: Limited coverageIonizing radiation

Iodinated contrast

Complex postprocessingCBF/CBV mismatchStroke


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Hemorrhage

Estimate area of ischemia

Determine infarct core

Determine penumbra

Status of vessels

Conclusions from CT

Nonenhanced CT

(primary goal)

Secondary goal

CT perfusion

CT Angiography


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No hemorrhage

Involvement of 7

Penumbra >20 % infarct

Intravenous Thrombolysis Based

on Advanced CT Imaging


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Conventional MR Anatomy

DW MR -Hyper acute irreversible

ischemia(core)

GRE /Susceptibility MR - Hemorrhage.

MRA-neck and intracranial vessels

Diffusion Perfusion mismatch - penumbra.

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MRI


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Sagittal T1-weighted

Axial DW

Axial GRE

Axial FLAIR

MR Perfusion

MR angiography (MRA)

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MR- Emergent protocol


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Diffusion Imaging in Stroke

Goals

1. To visualize the ischemic penumbra

2. To identify at an early time the difference between

salvageable, nonsalvageable and undamaged tissue

3. This will help in selecting proper cases for intervention

4. Prediction of outcome of intervention


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DWI-Hyperintense in ischemia

ADC-hypointense in ischemia

Hyperintense tissue on DWI-irreversibly infarcted

tissue(core)

Diffusion weighted MRI


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Large artery infarction

Small vessel or lacunar infarction

Cardioembolic infarctions multiple vascular

territories

Watershed infarctions-Border zones

Global ischemia

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TOAST classification


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DWI-Large arterial territory


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DWI-Lacunar infarct


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DWI-Embolic


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DWI-Watershed


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Endogenous spin arterial labelling

Exogenous tracer-commonly used

Signal loss due to T2* shortening

MR Perfusion-Technique


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PWI-DWI DISCONCORDANCE :

TYPE 1: PWI >>> DWI

TYPE 2 : PWI = DWI

TYPE 3 : PWI


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PATTERN 1 : PI>DWI

Proportion of PI>DWI patterns decreased with

scan delay,

constituting 75.0% before 6 hours,which in the following6-hour periods decreased

to71.4%, 50.0%, and 44.4% .

The greater efficacy of thrombolytic treatment.


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Salvage of mismatch region with thrombolytic

therapy.


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PATTERN 2 OR 3 :PATTERN 2 OR 3 :

(MATCHED OR PWI


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DWI CBV CO-REGISTERED

NO MISMATCH


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PATTERN 4: Isolated DWIThe reperfusion:

Strongly suggests that the initial

proximal occlusion has been lysed .

PATTERN 5: Only PI deficit .Represents tissue at risk but not committed to

infarction . Spontaneous resolution of clinical and

perfusion deficits or may progress to infarction .

- TIA


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DIFFUSION WEIGHTED MR

PWI > DWI - Neuroprotective agents and / or

Thrombolysis is beneficial

PWI = DWI

PWI < DWI

Not beneficial


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MRA-Extracranial vessels

3 D TOF MRA CE MRA


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MRA-Intracranial vessels


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8 HOURS 2 DAY 1 WEEK

Contrast-enhanced T1-weighted images show intravascular

enhancement over the infarct on the first and second days and

moderate cortical and subcortical enhancement 1 week after stroke.


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Absolute contraindications

Intracranial hge ,mass lesions

>1/3rd MCA

3 hrs for IV thrombolysis

Ictus >6 hrs for IA thrombolysis

Criteria for thrombolysis


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` Favourable factors

Proximal MCA or basilar tip occlusion

Diffusion perfusion mismatch or penumbra on CTP

Unfavourable factors

Microbleeds on GRE

Early parenchymal enhancement

Larger DWI abn volume

Very low CBF

Criteria for thrombolysis


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61%

35%

11%

Recanal. rate

Rate of recanalization after tPA and site

of occlusion

ACI M1 M2-M3


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NECT/MRI+DWI

No hemorrhage

0-3 hourspost ictal

IV thrombolytics

3-6 hrs post ictal

CTA +CTP/DWI+MRP

Thrombus withpenumbra

IA thrombolytics

No penumbra +/-thrombus

No IA thrombolytics

Hemorrhage

No Rx


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Is There a Hemorrhage?

MR=CT for parenchymal hge

CT better than MR for SAH

Is there a penumbra?

MRP provides more brain coverage than CTP

MRP only qualitative but CTP is quantitative

Recap ; MR or CT


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Is a Large Vessel Occluded?

CTA =MRA

MRA prone to artifacts due to motion in emergent

situation

` Time?

CT fast to perform ,post processing and reporting

difficult

MR difficult to perform,easy to report

Recap: MR or CT


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Time is brain


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Both CT and MR equally efficacious for imaging

acute stroke

Using individual modality is according to

availability, logistics and preference

Penumbra is the most important thing to imageafter 3 hrs and CTP and MR DW P mismatch

both excellent to detect

Conclusion


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Thank you

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