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imaginginstroke.pptx
- 1. IMAGING IN ISCHEMICSTROKE DR. SANDRA JOHNS 1st year PGRD
- 2. Definition A NEUROLOGICAL DEFICITOF ▪Sudden onset ▪ With focal rather than global dysfunction ▪ In which, after adequate investigations, symptoms are presumed to be of non- traumatic vascular origin ▪ and lasts for >24 hours
- 3. Functional loss ofcell CYTOTOXICEDEMA, CELL DEATH Increased water content VASOGENIC EDEMA MASS EFFECT GLIOSIS MINUTES 12-24 hrs 24hrs-2wks PATHOPHYSIOLOGY Reduced blood flow Autoregulation
- 4. Role of imagingin ischemic stroke ▪ To rule out mimics esp hemorrhage ▪ To suggest the therapeutic role ▪ To establish the etiology
- 5. Stroke – Temporalphases ▪ Early Hyperacute – 0-6hrs ▪ Late Hyperacute 6 to 24 hrs ▪ Acute- 24 hrs to one week ▪ Subacute- 1 to 3 weeks ▪ Chronic- > 3wks
- 6. NCCT in stroke ▪Very sensitive in detecting hemorrhage ▪ Other mimics ruled out- ISCHEMIA SUSPECTED
- 7. Early CT findings A)Hypoattenuating grey matter structures B)Presence of one or more hyperattenuating arteries C)Early Mass effect
- 8. Obscuration of lentiform nucleus ▪Proximal MCA occlusion Lenticulostriate Perforator arteries
- 9. Insular ribbon sign ▪Hypoattenuation of insular cortex
- 10. NCCT in acutestroke ▪ OTHER EARLY SIGNS Loss of grey white matter differentiation Early mass effect- Narrowing of sylvian fissure Loss of cortical sulci
- 11. Hyperdense MCA sign ONLYREVERSIBLE EARLYSIGN ▪ MCA occluded by fresh thrombus ▪ -specificity- 100%, sensitivity -30% ▪ Hyperdense MCA can also be seen ➢high hematocrit level ➢calcification in such cases – usually bilateral
- 12. Hyperdense artery sign ▪Hyperedense basilar artery sign
- 13. NCCT ▪ Importance ofwindow settings Normal settings- w80 HU,C- 20HU W- 8HU- C-32 HU SENSITIVITYINCREASED
- 14. NCCT ▪ Advantages very usefulto exclude hemorrhage widely accessible convenient short imaging time ▪ Disadvantages findings are subtle not useful for ischemic penumbra Not useful for posterior fossa infarcts
- 15. MRI in stroke DWI Mostsensitive sequence in stroke imaging High intensity in DWI indicate restriction of the ability of water proton to diffuse extracellularly.
- 17. DWI- stroke ▪ Hyperacutestroke-Cytotoxic edema ▪ Lesion appears bright
- 18. Conventional MRI inacute stroke- T2 and FLAIR • These sequences detect 80% infarct before 24 hrs • It can be negative upto 2 to 4 hrs
- 20. Temporal sensitivity Spacial sensitivity After55 min After 5 hrs
- 21. Post contrast techniques ▪Acute- Meningeal enhancement adjacent to infarct • Subacute -Gyriform enhancement • Meningeal enhancement decrease by 1 wk
- 22. Conventional MR imaging Hyperacuteinfarct Subacute infarct
- 23. Pseudonormalization of DWI Occursbetween 10 - 15 days
- 24. Types of infarcts ▪Large artery occlusions ▪ Lacunar infarcts ▪ Watershed infarcts ▪ Embolic infarcts ▪ Venous infarcts
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- 31. Lt PCA Iterritory
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- 34. Lacunar infarcts ▪ Upto1.5 cm in size ▪ Occlusion of perforating arteries ▪ Deep grey matter , deep white matter,brainstem ▪ Multiple
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- 37. Watershed infarcts ▪ Junctionof large arterial territories ▪ Chronic large vessel stenosis precipitated by hypotension ▪ DWI , PW helpful in etiology
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- 40. CTA ▪ Fast, thinsection,volumetric spiralCT examination performed with a time- optimized bolus of contrast material for the opacification of vessels.
- 41. CTA- Source images ▪Occlusion ,stenosis or significant calcification of an Extracranial internal carotid artery ▪ Detection of hyperacute infarct ▪ Substraction perfusion
- 43. CTA- adv ▪ Volumerendering. ▪ Groups of voxels within defined attenuation thresholds are selected,and a color as well as an “opacity” is assigned
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- 45. CTA- comparison ▪ Degreeof stenosis-Axial,VR images ▪ Calcification- axial, MIP ▪ Anatomical, spacial relationship-axial,VRT
- 46. MRA - techniques ▪TOF techniques use of gradient pulses withTRshorter than background tissue– Flow related enhancement of inflowing nuclei ▪ 2D technique- individual slices useful in slow flow states ▪ 3D techniques-A volume of slab useful in high flow states Better spacial resolution
- 47. CE MRA RAPID 3DGRADIENT ECHO (GRE) SEQUENCE FIRST PASS MRA USINGA SELECTIVELY LARGE BOLUS OF GADOLINIUM BASEDCONTRAST. ▪ ADVANTAGES : NOT SUSCEPTIBLETO SIGNAL LOSS FROMTURBULENCEOR SLOW FLOW COMPAREDWITHTOF OR PCTECHNIQUE ▪ ALLOWS BETTERVESSELTO BACKGROUNDCONTRASTCOMPAREDWITH TOF /PC ▪ SHORTER IMAGINGTIME ▪ LESS SUSCEPTIBLETO MOTIONARTIFACTS ▪ ALLOWS IDENTIFICATION OF SLOW FLOW IN NEARLYOCCLUDEDVESSEL ▪ ALLOWS MORE ACCURATEASSESSMENTOF STENOSIS &VISUALIZATION OF ULCERATED PLAGUE
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- 49. Ischemic penumbra ▪ Functionallyimpaired, morphologically intact ▪ Between thresholds of electrophysiological dysfunction and tissue damage
- 50. Normal blood flow parametres TissueCBF(ML/100g/mn) Normal 50-60 Oligaemic 35 Penumbra( salvagable) 2o Infarct <10
- 51. Imaging - ischemicpenumbra ▪ Functional studies CT perfusion MR perfusion
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- 53. CT- perfusion parameters ▪ ▪ ▪ ▪ CEREBRALBLOODVOLUME the volume of blood per unit of brain tissue CEREBRAL BLOOD FLOW the volume of blood flow per unit of brain tissue per minute MEANTRANSITTIME, the time difference between the arterial inflow and venous outflow TIMETO PEAK ENHANCEMENT the time from the beginning of contrast material injection to peak enhancement
- 54. CT perfusion -Interpretation M TT CBF CBV Arterial stenosis normal normal Oligaemia (>60%) near normal Penumbra (>30%) Normal or increased Infarct (<30%) (<40%)
- 55. CBV CBF MTT INFARCTWITH SALVAGABLE PENUMBRA
- 56. MTT CBF CBV COMPLETEDinfarct
- 57. MR perfusion interpretation Parameters CBF CBV MTT Interpretationby Deconvolution technique same as in CT perfusion Maps of CBF are taken to assess mismatch with DWI
- 58.