1. Evidence-Base Medicine
Stroke
Int 韓孟志、蘇熙淵

2. Issue 1
What is the imaging modality of choice for the detection of intracranial hemorrhage?

3. Angiography: DSA gold standard for vascular anomaly(84%)
ICH
NECT
T1WI
T2WI
Hyperacute
(intracellular oxy-Hgb)
Hyperdense
Isointense
Hyperintense
Acute
(intra deoxy-Hgb)
Hypointense
Subacute-early
(intra met-Hgb)
Isodense
Subacute-late
(extra met-Hgb)
Chronic-early
(extra met-Hgb, hemosiderin,ferritin)
Hypodense
Chronic-late
(Hemosiderin)
Angiography: DSA gold standard for vascular anomaly(84%)

4. Image recommendation Initial Dx: NECT Staging/workup: MRI, MRA, MRV
Angiography: no clear cause; young, normtensive, stable, surgical candidates
Diagnostic Imaging, p:I4-58;Blaser etc.

5. MRI for early detection of hemorrhage
typically the first diagnostic study susp stroke
widespread access ; speed of acquisition.
MRI for early detection of hemorrhage
Gradient-echo images can also show the presence of old hemorrhages
MRI is more sensitive than CT for the early diagnosis of brain infarction,
Overview of the evaluation of stroke – 2006 UpToDate; Louis R Caplan, MD 3a

6. CT of the head is the imaging procedure of choice in the initial evaluation of suspected ICH
Angiography should be considered for all patients without a clear cause of hemorrhage who are surgical candidates, particularly young, normotensive patients who are clinically stable
MRI and MRA are helpful and may obviate the need for contrast cerebral angiography in selected patients.
Guidelines for the Management of Spontaneous Intracerebral Hemorrhage, Joseph P ,etc. (Stroke. 1999;30: ) 3a

7. MRI may be as accurate as CT for the detection of acute hemorrhage in patients presenting with acute focal stroke symptoms and is more accurate than CT for the detection of chronic intracerebral hemorrhage
Comparison of MRI and CT for detection of acute intracerebral hemorrhage. JAMA Oct 20;292(15): ) Kidwell CS, Chalela JA, Saver JL, 4

8. New evidence suggests that MR imaging alone may be adequate to identify hemorrhagic stroke in the acute setting, and that MR imaging is superior to CT for identification of chronic microbleeds and hemorrhagic conversion of infarction.
Hemorrhagic stroke. (Neuroimaging Clin N Am May;15(2):259-72), Smith EE, Rosand J,Greenberg SM.

9. Issue 2
What are the imaging modalities of choice for the identification of brain ischemia and the exclusion of stroke mimics?

10. Image recommendation Acute: MR+T2, DWI Subacute: MR+ DWI, T2, T1C+
Chronic: CT or MRI
Diagnostic Imaging, p:I4-76~84;Blaser etc.

11. Perfusion and diffusion MRI together with MR angiography (MRA) are very helpful for the acute evaluation of patients with ischemic stroke. MRI and MRA are the recommended techniques for screening cerebral aneurysms and for the diagnosis of cerebral venous thrombosis and arterial dissection.
EFNS guideline on neuroimaging in acute stroke. Report of an EFNS task force. Masdeu JC etc.
European Federation of Neurological Societies (EFNS)

12. MR imaging
More sensitive and specific than CT for detection of acute cerebral ischemia within the first few hours
Depicting the pathologic entity (stroke and mimics)
Ashok Srinivasan,MD, et al; Radiographics 2006; 26; S75-S95

13. Diffusion-weighted MRI
DWI represents a major advance in the early diagnosis of acute ischemic stroke
DWI can be normal in the ischemic brain regions.
A sensitive and specific measure of normal rCBF is a necessary complement to a negative DWI
F.S.Buonanno, et al. Neurology 1999;52;

14. Low CBF may occur in patients with migrainous aura, or postictal cortical depression.
Best use DWI in concert with MRI bases rMTT/rCBF maps as a clinically valuable indicator: requires further systematic study.
F.S.Buonanno, et al. Neurology 1999;52;

15. Issue 3
What imaging modality should be used for the determination of tissue viability the ischemic penumbra?

16. CT perfusion image
Measure the following perfusion parameter: (1)cerebral blood volume, (2)cerebral blood flow, (3)mean transit time, (4)time to peak enhancement

17. CT perfusion image penumbra Infarcted tissue
Increased mean transit time with moderately decreased cerebral blood flow(>60%) and normal/increased cerebral volume(80~100%)
Increased mean transit time with markedly reduced cerebral blood flow (>30%) and moderately reduced cerebral volume (>60%)
Infarcted tissue
Severely decreased cerebral blood flow (<30%) and cerebral volume (<40%) with increased mean transient time

18. Diffusion-weighted MRI
Areas of cytotoxic edema  restricted motion of water molecule.
Higher rate of diffusion  greater loss of signals
Patients with hyperacute stroke ischemic tissues appears bright in comparison with normal brain tissue.

19. Perfusion-weighted MRI
Maps of the mean transit time the largest area of abnormality
Mean cerebral blood volume underestimation of the final infarcted size
Mismatch between initial cerebral blood flow maps and diffusion-weighted MRI  predicted a further extension of the infarct.

20. Diffusion and perfusion weighted MRI
Region shows both diffusion and perfusion abnormality: irreversibly infarcted tissue.
Only perfusion abnormality and normal diffusion: viable ischemic tissue

21. Diffusion and perfusion weighted MRI
Lesion on the diffusion-weighted images < on the perfusion-weighted images: penumbra
The same size on diffusion and perfusion weighted images: irreversibly infarcted tissue
Lesion on the diffusion-weighted images > on the perfusion-weighted images or only on diffusion-weighted images: early reperfusion of ischemic tissue
Ashok Srinivasan,MD, et al; Radiographics 2006; 26; S75-S95

22. Issue 2
What are the imaging modalities of choice for the identification of brain ischemia and the exclusion of stroke mimics?

23. MR imaging
More sensitive and specific than CT for detection of acute cerebral ischemia within the first few hours
Depicting the pathologic entity (stroke and mimics)
Ashok Srinivasan,MD, et al; Radiographics 2006; 26; S75-S95

24. Diffusion-weighted MRI
DWI represents a major advance in the early diagnosis of acute ischemic stroke
DWI can be normal in the ischemic brain regions.
A sensitive and specific measure of normal rCBF is a necessary complement to a negative DWI
F.S.Buonanno, et al. Neurology 1999;52;

25. Low CBF may occur in patients with migrainous aura, or postictal cortical depression.
Best use DWI in concert with MRI bases rMTT/rCBF maps as a clinically valuable indicator: requires further systematic study.
F.S.Buonanno, et al. Neurology 1999;52;

26. Issue 3
What imaging modality should be used for the determination of tissue viability the ischemic penumbra?

27. CT perfusion image
Measure the following perfusion parameter: (1)cerebral blood volume, (2)cerebral blood flow, (3)mean transit time, (4)time to peak enhancement

28. CT perfusion image penumbra Infarcted tissue
Increased mean transit time with moderately decreased cerebral blood flow(>60%) and normal/increased cerebral volume(80~100%)
Increased mean transit time with markedly reduced cerebral blood flow (>30%) and moderately reduced cerebral volume (>60%)
Infarcted tissue
Severely decreased cerebral blood flow (<30%) and cerebral volume (<40%) with increased mean transient time

29. Diffusion-weighted MRI
Areas of cytotoxic edema  restricted motion of water molecule.
Higher rate of diffusion  greater loss of signals
Patients with hyperacute stroke ischemic tissues appears bright in comparison with normal brain tissue.

30. Perfusion-weighted MRI
Maps of the mean transit time the largest area of abnormality
Mean cerebral blood volume underestimation of the final infarcted size
Mismatch between initial cerebral blood flow maps and diffusion-weighted MRI  predicted a further extension of the infarct.

31. Diffusion and perfusion weighted MRI
Region shows both diffusion and perfusion abnormality: irreversibly infarcted tissue.
Only perfusion abnormality and normal diffusion: viable ischemic tissue

32. Diffusion and perfusion weighted MRI
Lesion on the diffusion-weighted images < on the perfusion-weighted images: penumbra
The same size on diffusion and perfusion weighted images: irreversibly infarcted tissue
Lesion on the diffusion-weighted images > on the perfusion-weighted images or only on diffusion-weighted images: early reperfusion of ischemic tissue
Ashok Srinivasan,MD, et al; Radiographics 2006; 26; S75-S95