Imaging Acute Stroke and Cerebral Ischemia

Transcription

1 Department of Radiology University of California San Diego Imaging Acute Stroke and Cerebral Ischemia John R. Hesselink, M.D.

2 Causes of Stroke Arterial stenosis Thrombosis Embolism Dissection Hypotension Anoxia / hypoxia Hypoglycemia

3 Imaging Acute Stroke Conventional Imaging Abnormal vascular density / signal Vascular enhancement Loss of gray / white contrast Cortical swelling Sulcal effacement Ventricular compression MRA \ CTA

4 History: 85 y/o man with a right hemiparesis 291

5 Dx: MCA embolus with cerebral infarction {Page 2}

6 History: 62 y.o. male with transient weakness on the right side O2027

7 Dx: Left carotid occlusion {Page 2}

8 History: 58 y.o. man with altered mental status

9 History: 59 y/o woman with headache and left-sided weakness 187

10 1 Weakness {Page 2} 2 T1 - FATSAT T2W 3

11 Dx: Right ICA dissection {Page 3}

12 History: 37 y/o HIV + female with acute right sided weakness 172

13 Dx: Acute MCA infarct 18 hours later {Page 2}

14 History: 50 y/o male with acute right hemianopsia following coronary artery angioplasty & stenting 666

15 {Page 2} Treated with intra-arterial TPA 1 day later

16 {Page 3}

17 {Page 4} Dx: Hemorrhagic occipital infarct

18 History: 77 y/o woman with right-sided weakness 733

19 {Page 2}

20 {Page 3} Dx: Amyloid angiopathy

21 Diffusion and Perfusion Imaging

22 Cerebral Ischemia / Infarction Physiology Brain requires glucose & oxygen Normal CBF ml/100gm/min If CBF < 18, electrical activity ceases If CBF < 10, neuronal metabolism stops CBF called the "ischemic penumbra" Pathologic effect depends on the degree & duration of ischemia

23 Diffusion Weighted Imaging Physical Principles Random molecular movement or "Brownian motion" Addition of a pair of strong gradient pulses 1st pulse - dephases the spins 2nd pulse - rephases spins if no net movement If net movement of spins occurs between gradient pulses, signal attenuation occurs Warach S: Diffusion & Perfusion MRI, in Clinical MRI, Edelman et al, Saunders, Chap. 26, pp

24 Acute Cerebral Ischemia Diffusion-Weighted Imaging CBF lowered to < 10 ml/100gm/min Cell membrane Na K pump fails Net movement of water from extracellular to intracellular compartment Diffusion restricted by cell membranes ADC & signal intensity on DWI

25 History: 47 y/o man with von-hippel-lindau disease & new left arm weakness 486

26 {Page 2} DWI ADC Dx: Infarct & MCA stenosis

27 History: 80 y/o woman with a fluent aphasia 405

28 {Page 2} DWI

29 {Page 3} DWI Dx: Acute & chronic strokes

30 History: 73 y/o woman with weakness 427

31 {Page 2} {Video clip} Dx: Acute pontine infarct

32 History: 76 y.o. male with vertebral-basilar TIA's 119

33 TIA's {Page 2} Dx: FLAIR & Diffusion - DWMI

34 History: 64 y/o man with bilateral leg weakness & ataxia 347

35 {Page 2}

36 Leg weakness {Page 3} Dx: Acute infarcts in pons & left corona radiata DWI

37 History: 16 y/o male with new onset of seizures 350

38 {Page 2} Diffusion

39 Dx: Brain abscess - Streptococcus milleri {Page 3}

40 History: 63 y/o man with seizures for 8 years 365

41 {Page 2}

42 {Page 3} Diffusion Dx: Epidermoid

43 Other Causes of Positive DWI Bacterial abscess, Epidermoid tumor Acute demyelination Acute encephalitis Tumors undergoing central necrosis Tumors with high nuclear:cytoplasmic ratios Creutzfeldt-Jakob disease Diffuse axonal injury T2 shine-through (High ADC)

44 Perfusion Techniques Cerebral blood flow PET Xenon CT CT and MRI Vascular transit time Cerebral blood volume

45 CT Perfusion Technique kvp, mas 2 8 sections / 5 10 mm thick Acquire 1 image set per second 40 second acquisition 40 ml of contrast ( mg I/ml) Inject 5-8 ml / sec

46 CT Perfusion Time Density Curve TTP CVA TTP rcbf = rcbv / MTT MTT Area = rcbv HU Baseline Injection Time (sec) Normal

47 History: 38 y/o male with a left hemiparesis DWI ADC 752

48 {Page 2}

49 MTT CBV CBF {Page 3} Dx: MCA embolus & stroke

50 76 y/o woman developed a complete aphasia & right hemiplegia 35 minutes earlier Tomandl BF, et al: Radiographics 23:565-92, 2003

51 Symptoms resolved completely within 2 hours 24 hours later

52 History: 18 y/o male with confusion & 7 seizures 633

53 {Page 2}

54 {Page 3} Dx: Moya Moya

55 MR Perfusion Methods Intravascular magnetic susceptibility - Inject bolus of gadolinium - Obtain time-intensity curve - Measure area under curve EPISTAR (QUIPSS) - Tag in-flowing blood with 180 o inversion pulse - Presaturate slice of interest - 90 o readout pulse to slice - Repeat sequence without tag - Subtract 4 from 3 - Signal difference proportional to perfusion

56 EPI Perfusion Sequence Gadolinium injection TR = 1000 msec; 90 o flip angle TE = 60 msec Fat saturation Matrix = 128 x 128 Acquisition time = 40 sec

57 EPI Perfusion Time Intensity Curve Baseline TTP CVA rcbf = rcbv / MTT Baseline Normal MTT Area = rcbv SI Injection TTP Time (sec)

58 History: 38 y/o man with altered mental status & a right hemiparesis ADC DWI 631

59 {Page 2} Dx: Embolic MCA infarct right ventricular cardiac thrombus rcbv CBV/MTT= rcbf Perfusion TTP rmtt

60 History: 59 y.o. woman with an upper GI bleed developed a left hemiparesis & slurred speech FLAIR DWI b=1000 ADC 623

61 {Page 2} 3D-TOF CE-MRA CTA

62 Perfusion TTP rmtt DWI rcbv CBV/MTT=rCBF

63 {Page 4} rmtt CT perfusion rcbv rcbf

64 {Page 5} CT perfusion Dx: DWI/PWI mismatch

65 Interpretation Right ACA-MCA watershed DWI abnormalities Perfusion imaging (4-5cc Gd/sec) N TTP MTT CBV (auto-regulation compensatory vasodilatation reduced functional reserve) CBF (CBV/MTT) Large DWI/PWI mismatch (penumbra) (large volume of tissue at risk = salvageable brain)

66 Ischemic Penumbra DWI / PWI Mismatch Diffusion Abnormality CBF < 10 ml/100g/min Cytotoxic edema Irreversible ischemia Perfusion Abnormality CBF = ml/100g/min Neuronal paralysis Penumbra Reversible ischemia

67 635 History: 56 y/o woman with hypertension & hyperlipidemia developed dysarthria & left facial droop

68 {Page 2} MTT rcbv TTP rcbf Dx: Acute infarct with matched DWI and perfusion

69 History: 40 y/o male metamphetamine abuser developed acute bilateral arm numbness, leg weakness & dysarthria 627

70 {Page 2}

71 {Page 3} L R Perfusion Imaging Pons

72 {Page 4} rcbv rmtt CBV/MTT=rCBF

73 {Page 5} Post tpa Day 3 Dx: Basilar thrombosis & posterior fossa ischemia

74 Acute Cerebral Ischemia Imaging Sensitivity CT scan MRI (T2/FLAIR) DWI Perfusion hours 6-12 hours < 1.5 hours Instantly

75 Acute Cerebral Ischemia The Integrated MR Exam T2 / FLAIR sequences Diffusion imaging (Diagnostic) Perfusion imaging (Prognostic) MR Angiography (Site for therapy)

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77 UCSD Neuroradiology Teaching File Website URL -