Imaging in acute ischemic stroke cases.pptx

imaging in acute ischemic stroke

1. Imaging in Acute ischemic stroke Presenter: Dr. Vipul Phogat

2. Why to use imaging in stroke ? 20% cases- wrongly diagnosed clinically!!!!!!!!! To decide treatment

3. Acute stroke Hyperacute stroke: 0-6hrs Acute stroke: 6-48hrs

4. Acute stroke CT protocol A multimodal protocol including NCCT brain CT angio neck + brain vessels ( not MR angio- motion artefacts) Perfusion CT All can be done within 15 mins with helical acquisition with separate contrast boluses.

5. NCCT Initial vs late parenchymal signs Initial hours (0-3) Lost GM-WM differentiation After 24 hours Well delineated hypodensity with cortical sulcal effacement

6. NCCT Other Initial signs Hyperdense MCA sign Dense artery sign Hyperdense MCA Normal MCA Hyperdense basilar artery Infarct Dot sign M2 M2 M3

7. NCCT Other signs Insular ribbon sign Hypodense Rt insula Disappearing BG sign Hypodense Rt BG Normal Lt BG Calcified emboli Old infarcts Calcified emboli Calcified emboli

8. ASPECT score Alberta Stroke Program Early Computed Tomography Score Can be applied to both CT and MR A 10 point score. 1 point subtracted for each region affected. MCA cortex= 6 points Subcortical structures= 3 points Insular ribbon= 1 point Score <7= >1/3rd MCA territory involvement

9. pc-ASPECTS MIDBRAIN- 2 POINT OCCIPITAL LOBES- 1 POINT EACH PONS- 2 POINT CEREBELLUM- 1 POINT EACH THALAMI- 1 POINT EACH

10. NCCT Malignant MCA infarct More than 1/3rd MCA territory involved i.e ASPECT score <7 C/F : Rapid deterioration of consciousness, headache, vomiting, Pathology : Severe cerebral swelling, Importance : increased risk of- Hemorrhagic transformation on thrombolysis Transtentorial herniation Brainstem compression From BMJ

11. CT Angiography

12. CT Angiography Neck + Brain vessels From aortic arch to vertex To assess - Location of thrombus- Large vessel occlusion? Length of thrombus Collateral blood flow

13. CT Angiography Coronal CTA shows right MCA occlusion. Note poor opacification of right M3, M4 branches compared with normal left side . Axial CTA showing Right M1 occlusion with collateral flow in delayed phase

14. Left CCA stenosis Right proximal ICA stenosis

15. Perfusion CT

16. Perfusion CT To see extent of infarcted core and ishcemic penumbra Faster and correlates well with DWI and pMR (but inferior) Less reliable for- estimating final infarct volume Predicting those who will not benefit from intra-arterial therapy Parameters seen: CBV: Volume of blood flowing in a given volume of brain (ml/100mg) CBF: Rate of blood flowing in a given volume of brain (ml/100mg/min) MTT: Avg. time taken by blood to flow through a given brain volume (sec)

17. pCT Normal CBV CBF CBV MTT Normal perfusion parameters are: Gray matter CBF: 60 mL/100 g/min CBV: 4 mL/100 g MTT: 4 s White matter CBF: 25 mL/100 g/min CBV: 2 mL/100 g MTT: 4.8 s

18. pCT Stroke CBF CBV TTP MTT CBF 10-25ml/100mg/min- Ichemia ( Blue ) CBF <10ml/100mg/min- infarction ( purple -black)

19. pCT Ischemic penumbra CBV/CBF mismatch CBV CBF CBV/MTT mismatch CBV MTT

20. pCT Acute crossed cerebellar diaschisis CBF TPP TPP

21. MR in stroke Time consuming, so expediated rapid stroke protocol: Fast FLAIR T2 DWI pMR Superior to CT in detecting small vessel and brainstem stroke. Better delineation of ischemic penumbra in cases of CT/CTA and clinical mismatch

22. MRI DWI-ADC Positive in ~95% hyperacute infarcts Diffusion restriction and ADC fall Within minutes Due to cytotoxic edema DTI: even more sensitive, especially for pontine and medullary lesions. DWI negative strokes : lacunar strokes, brainstem lesions, rapid recanalisation, transient/fluctuating hypoperfusion.

23. MRI FLAIR 0-4 hrs- 30% to 50% cases show hyperintensity and cortical swelling. >7hr- nearly all strokes positive T2: Positive after 12-24 hours. Intra-arterial hyperintensity = slow/ retrograde flow , an early sign.

24. MRI FLAIR-DWI mismatch DWI+ and FLAIR- Occurs in early stroke A quick indicator of viable ischemic penumbra Eligibility for thrombolysis

25. MRI T2-GRE Blooming thrombus sign Succeptibility vessel sign

26. MRI T1-C+ Intravascular enhancement due to slow flow in patent non-thrombosed vessels No parenchymal enhancement in acute stroke

27. Perfusion MRI DWI reflects the densely ischemic core pMR shows the ischemic penumbra also DWI-PWI mismatch: Ratio >2.6 provides 90% sensitivity and 83% specificity

28. Stroke mimics False hyperdense vessel sign on CT In a case of HSV encephalitis, due to relative hypodensity of surrounding parenchyma

29. Stroke mimics False hyperdense vessel sign on CT Calcified Right MCA. Attenuation values close to bone

30. Stroke mimics False hyperdense vessel sign on CT Diffuse hyperdense vessels due to raised hematocrit in a case of polycythemia vera

31. Stroke mimics DWI Case of Rt sided weakness with left cortical and thalamic DWI restriction (non-vascular pattern) with sparing of WM, in a case of status epilepticus DWI restriction in Hypoglcemia in a neonate

32. Primary CNS lymphoma. Left frontal periventricular lesion showing prominent diffusion restriction, presenting with hyperintensity on DWI ( a ), low ADC value ( b ) and mild hyperintensity on T2WI ( c ), all typical features of this type of hypercellular tumour. T1WI post gadolinium ( d ) shows homogeneous and intense contrast enhancement