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3. mri in acute stroke 2017 vietnam v2
- 1. MRI in Acute Ischemic Stroke Associate Professor Henry Ma Director of Neurology, Monash Health Head, Stroke Unit, Monash Health Senior Research Fellow, Florey Neuroscience and Mental Health Institutes Co-Chair, Australasia Stroke Trial Network (ASTN)
- 2. MRI Basics : The Sequences : • DWI • ADC • eADC • FLAIR • T2 • T1 • SWI • MRA • MR Perfusion / ASL
- 3. DWI: Diffuse Weighted Images • Indicates acute abnormality / infarct • Positive from 30 minutes from onset to about 2 weeks. • Not just acute ischemic stroke but also in • Haemorrhage (rim) • Tumour • Demyelination plaques • Infection • Beware of T2 shine through https://openi.nlm.nih.gov/detailedresult.php?img=PMC3109577_bcr2815-4&req=4
- 4. ADC : Apparent Diffusion Coefficient • Basically the reverse of DWI • So it is dark when acute and normal if non-acute • It can be difficult to decide on ‘how much darker’ especially small lesions • So there is another entity called exponential ADC (eADC) • Which looks bright (just like DWI) when acute • So an acute event will be • Bright on DWI and dark on ADC • Bright on DWI and bright of eADC
- 5. DWI and ADC with time DWI become bright and then dark ADC become dark and then normal / bright DWI ADC
- 6. DWI : ADC : eADC : FLAIR in Acute Stroke DWI Bright ADC Dark eADC Bright FLAIR Bright
- 7. ACUTE DWI ACUTE ADC Acute Ischemic Changes Bright Dark k
- 8. DWI ADC T2 T1 FLAIR SWI Chronic Ischemic Changes
- 9. FLAIR, T1 and T2 • T1 • mainly use for structure lesions or loss of volume (black holes) • Excellent for contrast enhancement assessment – tumour, inflammation, infarct • T2 • Reverse of T1, great for smaller lesions • Important to beware of the T2 shine through of DWI • FLAIR • T2 with black CSF / Fluid • Good for white matter lesions and identify grey white matter blurring
- 10. DWI ADC T2 FLAIR SWI Chronic Changes Bright DWI: T2 Shine through Bright T2Bright ADC Haemorrhagic transformation
- 11. Susceptibility Weighted Images (SWI) Gradient Echo Sequence (GRE) or T2* • These sequences mainly look at iron deposition • Hence it is often used for • Cerebral haemorrhages • Micro-hemorrhages • Subarachnoid haemorrhages • AVM • Amyloid angiopathy • Does not tell old or new blood – may be…… • May be useful for ‘bright CT lesions’
- 12. American Journal of Neuroradiology February 2007, 28 (2) 316-317; Susceptibility Weighted Images (SWI) Micro-hemorrhages : Amyloid Angiopathy and AVM George et al. Neurology India
- 13. SWI and Subarachnoid Haemorrhage American Journal of Neuroradiology February 2009, 30 (2) 232-252; DOI: https://doi.org/10.3174/ajnr.A1461 SWI is a lot more sensitive to pick up SAH than non- contrast CT
- 14. MRA • Usually time of flight hence no need for contrast • Intracranial and extracranial need different coils so cannot be done at the same time • Can overcall the severity of stenosis • Less details than CTA and prone to artefacts
- 15. MRA : Time of flight (TOF) vs Contrast MRA TOF MRA shows significant artefacts compare to contrast related MRA Mair G et al. B J Radiol 2014;87
- 16. Acute Stroke : all about salvage of the ischemic penumbra Clinical Improvement Baron J. Cerebrovascular Disease 1999;9:193-201
- 17. MR Perfusion : Shows the core and the penumbra
- 18. Pit Falls of MRI • Motion artefacts • MRI is very sensitive to motion • Pseudo-normalisation of DWI • Negative DWI due to delayed scanning – always scan within 2 weeks • MRA over-call • Degree of stenosis • ‘vasculitis’ • Vasospasm
- 19. Journal de Radiologie Diagnostique et Interventionnelle, Volume 93, Issue 12, December 2012, Pages 988-1001 MRI : Motion artefact : ghosting
- 20. Journal de Radiologie Diagnostique et Interventionnelle, Volume 93, Issue 12, December 2012, Pages 988-1001 Artefact : MRI : Metal
- 21. DWI : Real or not? artefact Real
- 22. MRI and its application Help to Diagnose
- 23. Forster et al Jan 2012 · European Neurology Small infarct difficult to see on non-contrast CT : helps to confirm the diagnosis
- 24. DWI: Small infarct, hard to see on CT and also may be hard to see on initial DWI To avoid missing a lesion need to think about the potential location from clinical details
- 25. Journal de Radiologie Diagnostique et Interventionnelle, Volume 93, Issue 12, December 2012, Pages 988-1001 TIA : Small infarction : cannot pick up by CT
- 26. Journal de Radiologie Diagnostique et Interventionnelle, Volume 93, Issue 12, December 2012, Pages 988-1001 Transient ischemic attack (TIA) : DWI may help to identify real ischemic event which won’t know otherwise
- 27. DWI : White matter ischemia (WMI) Beware : WMI can be bright on DWI! DWI Bright = acute ADC Bright = non-acute T1 FLAIR Chronic WMI mimic DWI
- 28. Acute DWI lesion can be hidden by White matter ischemia FLAIR : nothing acute! DWI: Hidden acute ischemic lesion! Dark ADC confirms this is an acute ischemic lesion
- 29. MRI and its application: Identify the right patient for reperfusion therapy Find the patient with the best risk : benefit ratio
- 30. Thomalla et al. Mar 2013 · International Journal of Stroke DWI : FLAIR Mismatch DWI-FLAIR Mismatch The DWI lesion is larger than FLAIR lesion (the infarction) hence the DWI is PART of the penumbral tissue which can be reversed DWI-FLAIR NO Mismatch The DWI and FLAIR are of the same size hence no salvageable tissue
- 31. Kang et al · Oct 2012 · Stroke DWI : FLAIR Mismatch : What is missing? The Perfusion lesion is much larger than the DWI lesion and the DWI:PWI mismatch is different to the DWI:FLAIR mismatch So the DWI:FLAIR mismatch underestimate the real penumbral volume
- 32. DWI-FLAIR mismatch • Principle • FLAIR = irreversible infarction • DWI = potentially reversible ischemia • Hence DWI-FLAIR mismatch = reversible component of DWI • However • DWI reversal is rare • Does not provide any information on the ischemic penumbra • Significant inter-observer variation in assessing the FLAIR signal changes (k- score 0.46 to 0.65) • Background chronic white matter ischemia affects the interpretation of the FLAIR lesion *Aokiet al. J Neurol Sci 2010 ;293:39 ^Ebinger et al. Stroke 2010;40:250 #Petkova et al. Radiology 2010;257:782
- 33. EPITHET: MR Perfusion tPa vs Placebo 3-6 hours from stroke onset • Phase 2 randomised double blinded placebo controlled study • 3 – 6 hours from stroke onset • Alteplase vs placebo • MR perfusion imaging using Tmax 2sec as penumbral selection • Alteplase reduced infarct growth 33
- 34. DEFUSE 2 Response to endovascular reperfusion is not time-dependent in patients with salvageable tissue : using MR Perfusion 34 Must have perfusion mismatch to benefit!!
- 35. 35 • Penumbral mismatch exists up to 48 hours • Its salvage can lead to clinical improvement • Time may / may not be a factor IJS 2015
- 36. Collateral circulation in ASL Stroke 2014;45(4):1202-1207 In good collateral cases there is hyperintensive of vessel signal in ASL but not in poor collateral Patients with good collateral may have better functional outcome.
- 37. 21 year old Sudden onset of aphasia DWI - No acute ischemic Large area of hypoperfusion in the left cortex Left sided brush sign Insight Imaging 2017(8);91-100 FLAIR DWI DWI-ASL PERFUSION SWI DWI-ASL PERFUSION IN ACUTE NEUROLOGICAL CASE Migraine
- 38. 65 year old sudden onset of right sided weakness DWI showed changes NOT within any vascular territory MRA - no vessel occlusion in the region but more of a dilataion Hyperperfusion in the region Insight Imaging 2017(8);91-100MRA MRA-PERFUSION HYPERPERFUSION DWI DWIFLAIR DWI-ASL PERFUSION IN ACUTE NEUROLOGICAL CASE Status epilepticus
- 39. 85 yo with past history of stroke Presented with left arm weakness Initial DWI did not show ischemic changes DWI – ASL Perfusion Areas of hypoperfusion related to previous stroke Area of hyperperfusion suggests partial seizure Insight Imaging 2017(8);91-100 FLAIR DWI DWI-ASL PERFUSION DWI-ASL in Acute Neurological Situation
- 40. MRI and its application Hemorrhages
- 41. J Neurol Neurosurg Psychiatry 2012;83:124e137 Amyloid Angiopathy
- 42. J Neurol Neurosurg Psychiatry 2012;83:124e137 Various presentations of Amyloid Angiopathy
- 43. Journal de Radiologie Diagnostique et Interventionnelle, Volume 93, Issue 12, December 2012, Pages 988-1001 SWI : More Sensitive for microhemorrhages
- 44. Journal de Radiologie Diagnostique et Interventionnelle, Volume 93, Issue 12, December 2012, Pages 988-1001 DWI can be bright in Cerebral Haemorrhage, Subarachnoid Hemorrhage SAH SAH ICH
- 45. Front. Neurol., 25 May 2012 | https://doi.org/10.3389/fneur.2012.00086 Cerebral Haemorrhage : MRI helps to identify underlying causes
- 46. SWI – see more than just blood 48 year old with sudden onset of vertigo SWI showed clot in PICA 85 yo with left side weakness Long segment of M1 clot on SWI 72 yo with right homonymous hemianopia PCA territory infarct on DWI but nothing on the MRA SWAN showed left P2 clot with upstream artefact Insight Imaging 2017(8);91-100
- 47. 76 year old Right side weakness DWI lesion with smaller FLAIR changes (DWI-FLAIR mismatch) Large region of hypoperfusion SWI showed clot in M2 Brush sign of hyperperfusion with tPA ? Indication of reperfusion ? Relate to better outcome ? Relate to risk of haemorrhagic transformation Insight Imaging 2017(8);91-100 DWI FLAIR PERFUSION DWI-PERFUSION OVERLAP SWI SWI MR Perfuson, DWI and SWI together give more information
- 48. Right sided weakness Left MCA hypoperfusion with haemorrhage (SWI superimposition) DWI-ASL PERFUSION IN ACUTE NEUROLOGICAL CASE Subsequent recovery of some of the DWI lesions and hyperperfusion related to better clinical recovery. But ?? Increase risk of haemorrhagic transformation
- 49. MRI and its application Vessel Imaging
- 50. MRA : Ulcerated plaque T2 flow void with slightly higher wall signal Ulcerated Plaque T2 flow void with a projection into the lumen and high signal intensity Plaque ulceration Contrast MRA Shows contrasts media within the plaque In general contrast MRA performs better for ulceration identification because the fibrous cap will appear dark while the lack of such between the grey plaque content and contrast in lumen suggests ulceration. TOF is affected by ulcer location and orientation Insight imaging 2017(8) 213-225
- 51. MRA Wall Imaging Left M1 occlusion on MRA Heterogenous T2 signal and wall thickening T1 pre- and post-contrast lesion enhancement Atherosclerotic disease ? Unstable plaques JNNP 2016;87(6):589-597
- 52. Journal de Radiologie Diagnostique et Interventionnelle, Volume 93, Issue 12, December 2012, Pages 988-1001 MRA often pick up un-expected pathology Don’t just look at the stroke! Such as aneurysm
- 53. MRA : more than just MRA 4 year old girl with recurrent neurological deficit White matter lesions Bilateral ICA, MCA occlusion Collateral Moya Moya Angiogram showed flow void (arrow) and Moya Moya collateral The application of clinical genetic 2015 Feb (8)
- 54. Samaniego EA, Dabus G, Generoso GM, et al Postpartum cerebral angiopathy treated with intra-arterial nicardipine and intravenous immunoglobulin Journal of NeuroInterventional Surgery 2013;5:e12 Reversible Vasospasm : MRA
- 55. Journal de Radiologie Diagnostique et Interventionnelle, Volume 93, Issue 12, December 2012, Pages 988-1001 Sinus Thrombosis : MRI
- 56. Agrawal A, Swarnakar N. Cerebral venous thrombosis complicated by intracranial hypertension. Ann Trop Med Public Health [serial online] 2012 [cited 2017 Aug 4];5:268-70. Sinus thrombosis and venous infarct Non-vascular territory infarction Sinus thrombosis DWI FLAIR
- 57. Journal of Cancer Research and Therapeutics, Vol. 9, No. 4, October-December, 2013, pp. 751-753 60 year old with headache and mild dysarthria
- 58. MRI Venous Imaging Angiogram and Dynamic MR Angiography (DMRA) Both had Left MCA occlusion AB showed lack of cortical vein draining in both DSA and DMRA = poor collateral CD showed good cortical vein drainage (symmetrical transverse sinus drainage) = good collateral JNNP 2017;88:62-69
- 59. MR Venous Imaging Using T2* / GRE The cortical and medullary veins are seem on GRE or T2* Hypointensse vein can be seem with lack of arterial flow in TTP / MTT JNNP 2017;88:62-69
- 60. MRI and its application Other applications and stroke mimics
- 61. MRI : Cases 56 year old diabetes with rheumatoid arthritis and on immunosuppression presented with acute confusion, headache, and speech disturbance. Initial non-contrast CT normal Herpes Encephalitis
- 62. CADASIL
- 63. MELAS
- 64. SMART Syndrome The classical look along with history can help the diagnosis
- 65. MRI and its application A Case
- 66. Case 85 year old male • Went to bed well • Woke up in the middle of the night locked – in • Fully awake, could hear wife walking around in the morning but not able to call out or move Wife tried to wake patient up but saw him non-responsive and pooling saliva Ambulance arrived – intubation ED – continued intubation Stroke team assessment – 17 hours later
- 67. Patient made a full recovery and went home 2 days later Small DWI lesion Received Clot Retrieval
- 68. Summary • MRI is extremely useful in both acute and chronic setting • DWI - good for acute stroke identification especially if the clinical setting is unclear • SWI - helps to identify patient with high risk of bleeding • MRA – can provide information on the cause of the problem • Perfusion – crucial for reperfusion treatment • MRI – also able to identify stroke mimics