- Diffusion-weighted MRI is more sensitive than non-contrast CT for distinguishing acute ischemic stroke from other conditions, as it can detect ischemia earlier. It shows hyperintensity on DWI and hypointensity on the ADC map in the acute setting. - MRI can also identify chronic cerebrovascular pathology better than CT. However, CT is more readily available, less costly, and does not require removing metal/electronics from patients. - Multimodal CT and MRI, combining perfusion, angiography, and diffusion images, can identify the ischemic core and penumbra. This helps determine if patients may benefit from reperfusion therapies in the acute period.

1. Neuro imaging
Dr Teddy Sp.S
NEUROLOGIST VIEW

2. • A brain CT or MRI scan is urgently
recommended for all patients with
suspected acute stroke or transient
ischemic attack
• Noncontrast CT and gradient-recalled
echo MRI show similar accuracy in
the diagnosis of acute intracerebral
hemorrhage

3. • Diffusion-weighted MRI is markedly more
sensitive than noncontrast CT for
distinguishing acute ischemic stroke from
nonstroke conditions
• Combined multimodal parenchymal, perfusion
and vascular imaging with CT
or MRI could potentially identify patients with
an ischemic penumbra that might be
amenable to acute reperfusion therapies

4. • MRI identifies a broad range of acute and chronic
cerebrovascular pathologies that could aid
decisions about acute intervention, in-hospital
management and secondary prevention
• Overall, MRI is diagnostically superior to CT for
cerebrovascular indications, but is
contraindicated in ≈10% of patients, has limited
availability at many hospitals, and can be costly
and time-consuming

5. • CT is more readily available than MRI for
emergency use
• Equipment costs and patient charges are
lower for CT than for MRI
• CT involves exposure to ionizing radiation; no
known biological risk exists for MRI
• MRI is markedly more sensitive and accurate
than CT in early imaging-based diagnosis of
ischemic stroke

6. • MRI is contraindicated in a subset of patients
• Patients, personnel and equipment must be
screened to exclude unacceptable metal or
electronics from the MRI scanning environment
• In cases of severe renal failure, intravenous
contrast agent is contraindicated for both CT and
MRI, but noncontrast alternatives for vascular
and perfusion imaging are available for MRI

7. Vein
Artery
a
c
d
e
f
b 100
75
50
25
0
20
15
10
5
0
200
150
100
50
0
Vein
Artery
Figure 1 | Multimodal CTsurvey. A57 year-old male with a right MCAsyndrome underwent CT. a | The unenhanced CTscan
ruled out a cerebral hemorrhage, and showed effacement of the sulci, and subtle loss of gray–white matter differentiation in
the inferior right MCAterritory. From the CTPraw data, three parametric maps were extracted, relating to b | mean transit time,
c | cerebral blood flow, and d | cerebral blood volume. e | Application of the concept of ischemic penumbra led to a prognostic
map, which depicted the infarct in red and the penumbra in green, the latter being a potential target for acute reperfusion
therapies. f | CTAidentified an occlusion at the distal right ICAjust proximal to the MCAorigin (arrow) as the origin of the
REVIEWS

8. • Multimodal CT survey. A 57 year-old male with a right MCA
syndrome underwent CT. a | The unenhanced CT scan ruled
out a cerebral hemorrhage, and showed effacement of the
sulci, and subtle loss of gray–white matter differentiation in
the inferior right MCA territory. From the CTP raw data,
three parametric maps were extracted, relating to b | mean
transit time, c | cerebral blood flow, and d | cerebral blood
volume. e | Application of the concept of ischemic
penumbra led to a prognostic map, which depicted the
infarct in red and the penumbra in green, the latter being a
potential target for acute reperfusion therapies. f | CTA
identified an occlusion at the distal right ICA just proximal
to the MCA origin (arrow) as the origin of the
hemodynamic disturbance demonstrated by CTP. CTA also
revealed a calcified atheromatous plaque at the right
carotid bifurcation (arrowhead).

9. Box 2 | Early CTfindings in patients with acute stroke
Noncontrast CT
Sulcal effacement■
Loss of the insular ribbon■
Blurring of the gray–white matter junction■
Obscuration of the lentiform nucleus■
Hyperdense artery sign, indicative of intravascular■
thrombus
Multimodal CT
Arterial occlusion on CTA■
Reduction or absence of contrast on CTA source■
images
Reduction or absence of perfusion on CT perfusion■
parameter maps
Abbreviation: CTA, CT angiography.
Box 3 | Early MRI
Hyperintensity o■
minimal or no c
sequences
Hypointensity o■
Hypointense (‘b■
intravascular th
sequences
Arterial occlusio■
Absence of arte■
occlusion, on T2
Hyperintense ve■
or collateral flow
Reduction or ab■
source images
Reduction or ab■
parameter map
Abbreviations: FLAIR

10. best outcomes.38
r seen in 95%of
not used.33
acute stroke
on
travascular
TA source
CT perfusion
Box 3 | Early MRI findings in patients with acute stroke
Hyperintensity on diffusion-weighted imaging, with■
minimal or no changes on T2-weighted or FLAIR
sequences
Hypointensity on apparent diffusion coefficient■
Hypointense (‘blooming’) artery sign of acute■
intravascular thrombus on gradient-recalled echo
sequences
Arterial occlusion on magnetic resonance angiography■
Absence of arterial flow void, which is indicative of■
occlusion, on T2-weighted or FLAIR sequences
Hyperintense vessel sign, which is indicative of slow■
or collateral flow, on FLAIR sequences
Reduction or absence of contrast on dynamic PWI■
source images
Reduction or absence of perfusion on PWI perfusion■
parameter maps
Abbreviations: FLAIR, fluid-attenuated inversion recovery; PWI,
perfusion-weighted imaging.

11. a
c
d
e
b
f
Figure 2 | Multimodal MRI. The patient arrived at the emergency room 45 min after symptom onset. MRI was
started 20 min later, and the patient was treated with intravenous tissue plasminogen activator 55 min after arrival.
a | DWI sequence showed an area of hyperintensity in the right temporal, insular and frontal lobes. b | Apparent diffusion
coefficient map showed a matching area of hypointensity, confirming that the DWI lesion was due to acute ischemia.
c | Mean transit time maps showed an area of hypoperfused tissue larger than the DWI abnormality; the difference
represented the penumbra. d | Fluid-attenuated inversion recovery showed no matching hyperintensity, indicating that the

12. ER2010 | VOLUME6 www.nature.com/ nrneurol
fluid-attenuated inversion recovery (FLAIR), magnetic
resonanceangiography(MRA),and perfusion-weighted
imaging(PWI). Thesesequencesshow pathologyspeci-
ficto stroke, and thesequencesarecomplementary and
confirmatory, aswewill discussbelow.
Diffusion-weighted imaging
DWI hastransformed thediagnosisof ischemic stroke
in itsearliest stages, from relianceon amostly clinical
inferenceabout thepresence, localization and sizeof an
ischemiclesion to imagingconfirmation of theinfarct.
e
Figure 2 | Multimodal MRI. The patient arrived at the emergency room 45 min after symptom onset. MRI was
started 20 min later, and the patient was treated with intravenous tissue plasminogen activator 55 min after arrival.
a | DWI sequence showed an area of hyperintensity in the right temporal, insular and frontal lobes. b | Apparent diffusion
coefficient map showed a matching area of hypointensity, confirming that the DWI lesion was due to acute ischemia.
c | Mean transit time maps showed an area of hypoperfused tissue larger than the DWI abnormality; the difference
represented the penumbra. d | Fluid-attenuated inversion recovery showed no matching hyperintensity, indicating that the
DWI lesion was <6 h old. e | The gradient-recalled echo sequence showed no evidence of acute or chronic hemorrhage, but a
clot was seen in the right MCA(arrow). f | Contrast-enhanced MRAof the neck and brain revealed a chronic asymptomatic
right carotid occlusion, although the patient had good collateral flow through the anterior communicating artery, and his right
carotid artery was normal. The proximal right MCAabruptly terminated in the proximal portion, as confirmed by axial MRA.
Abbreviations: DWI, diffusion-weighted imaging; MCA, middle cerebral artery; MRA, magnetic resonance angiography.
© 20 Macmillan Publishers Limited. All rights reserved10

13. Key words umur infark
Hiperaut < 6 jam
• DWI bright
• ADC dark
• Flair normal,,
• karena flair baru ada
kelainan setelah 6 jam
infark
< 4 hari
• DWI Bright
• ADC dark
• Flair bright,,

14. Umur infark 2
Infark > 4 hari
• DWI bright
• ADC bright
• Flair bright,,
ADC bright setelah 4 hari
Infark kronik > masa akut
• DWI dark
• ADC bright
Kebalikan infark akut

15. Axial unenhanced CT images in a proximal segment of the left MCA in a 53-year-old man (a) and a
distal segment of the left MCA in a 62-year-old woman (b), obtained 2 hours after the onset of
right hemiparesis and aphasia, show areas of hyperattenuation (arrow) suggestive of intravas-
cular thrombi.

17. Bila aspects score >7,, trombolyze!

19. CT perfusi
• Infark CBV
• Iskemi CBF dan MTT

20. Acute stroke in a 65-year-old man with left hemiparesis. CT perfusion maps of cerebral blood vol-
ume (a), cerebral blood flow (b), and mean transit time (c) show mismatched abnormalities
(arrows) that imply the presence of a penumbra. The area with decreased blood volume
represents the ischemic core, and that with normal blood volume but decreased blood flow and
increased mean transit time is the penumbra

21. Perdarahan pada MRI
• T2 dan Flair intensitas meningkat tidak
homogen
• GRE hitam

22. Acute stroke in the left me- dial temporal lobe in a 44-year-old man. (a, b) Axial T2-weighted (a)
and fluid- attenuated inversion recovery (b) images show areas with increased signal intensity. (c)
Gradient-echo image shows abnormal low signal intensity in the same areas. These findings are
suggestive of hemor- rhage

24. Konfirmasi akut stroke
• DWI putih
• ADC hitam

25. Acute stroke of the posterior circulation in a 77-year-old man. (a) Diffusion- weighted MR image (b 􏰁 1000
sec/mm2) shows bilateral areas of increased signal intensity (arrows) in the thalami and occipital lobes.(b) ADC
map shows decreased ADC values in the same areas (arrows). These findings are indicative of acute ischemia.

26. Kronik infark
• DWI hitam
• ADC bright
Kebalikan dari infark akut

27. Chronic infarcts in a 71-year-old man with a remote history of multiple strokes. (a) Diffusion-
weighted MR image (b 􏰁 1000 sec/mm2) shows areas of decreased signal intensity in the left
frontal lobe. (b) ADC map shows increased ADC values in the white matter of the right frontal
lobe. These features are suggestive of chronic infarction.

28. Acute stroke in a 67-year-old woman with acute left hemiplegia 2 hours after ca- rotid
endarterectomy. (a) Dif- fusion-weighted MR image
(b 􏰁 1000 sec/mm2) shows an area of mildly increased signal intensity in the right parietal lobe
(arrows). The ADC values in this region were decreased. (b) Perfusion-weighted MR image shows
a larger area with increased time to peak en- hancement (arrows) in the right cerebral
hemisphere. The mis- match between the perfusion and diffusion images is indica- tive of a large
penumbra.

29. Flow chart shows an acute stroke imaging protocol,,Radiographics october 2006