perfusion imaging of stroke for early detection and selectiong appropriate patients for thrombolytic therapy

2. Adila Iqbal
R-3, NRD, SHL.

3. LEARNING OBJECTIVES
 Brief review of vascular territories
 Early CT and MR signs of infarction
 How to identify patients with tissue at risk for guidance in
selecting the appropriate therapy

4. Penumbra

5. Rai AT, Carpenter JS, Peykanu JA, Popovich T, Hobbs GR, Riggs JE. The role of CT perfusion imaging in acute stoke diagnosis: a large single-
center experience. J Emerg Med 2008; 35:287–292

9. STANDARD WINDOW SETTING
(W80 C 20) – SENSITIVITY 57%
SPECIFICITY 100%
STROKE WINDOW SETTING (W8 C
32) SENSITIVITY 71% SPECIFICITY
100%

10. Alberta Stroke Program Early CT Score
(ASPECTS)
 Proposed in 2001 as a
means of quantitatively
assessing acute
ischemia on CT images.
 MCA territory is divided
into 10 regions, each of
which accounts for one
point in the total score.
Silvennoinen HM, Hamberg LM, Lindsberg PJ, Valanne L, Hunter GJ. CT perfusion identifies increased salvage of tissue in patients receiving intravenous
recombinant tissue plasminogen activator within 3 hours of stroke onset. Am J Neuroradiol 2008; 29:1118–1123

11. 10 regions of the MCA distribution, each of which accounts for one point in the ASPECTS system:
M1, M2, M3, M4, M5, M6, the caudate nucleus (C), the lentiform nucleus (L), the internal capsule (IC), and the insular
cortex (I).
For each area involved in ischemia depicted at unenhanced CT, one point is subtracted from the total score of 10.
Silvennoinen HM, Hamberg LM, Lindsberg PJ, Valanne L, Hunter GJ. CT perfusion identifies increased salvage of tissue in patients receiving intravenous
recombinant tissue plasminogen activator within 3 hours of stroke onset. Am J Neuroradiol 2008; 29:1118–1123

12. Normal symmetric brain perfusion.
All color maps are coded red for higher values and blue for
lower values.
PERFUSION CT BRAIN
Healthy 53-year-old man
Unenhanced CT scan
Perfusion CT cerebral blood volume
Perfusion CT cerebral blood flow
Perfusion CT mean transit time

13. Perfusion CT maps cerebral blood volume
CBV:
Total volume of blood within an imaging voxel including blood in the tissues and
blood vessels.
CBV is measured in units of milliliters of blood per 100 g of brain.
Hopyan J, Ciarallo A, Dowlatshahi D, et al. Certainty of stroke diagnosis: incremental benefit with CT perfusion over noncontrast CT and CT angiography.
Radiology 2010; 255:142–153

14. Perfusion CT cerebral blood flow
CBF:
Total volume of blood moving through a voxel in a given unit of time and is
commonly measured in units of milliliters of blood per 100 g of brain tissue per
minute.
After a bolus of contrast material is injected, time is required for each individual
molecule of contrast material to circulate.
Hopyan J, Ciarallo A, Dowlatshahi D, et al. Certainty of stroke diagnosis: incremental benefit with CT perfusion over noncontrast CT and CT angiography.
Radiology 2010; 255:142–153

15.  MTT:
 Average transit time of all the molecules of contrast medium with the
bolus through a given volume of brain measured in seconds.
 MTT can be approximated according to the central volume principle:
MTT = CBV / CBF.
Perfusion CT mean transit time
Hopyan J, Ciarallo A, Dowlatshahi D, et al. Certainty of stroke diagnosis: incremental benefit with CT perfusion over noncontrast CT and CT angiography.
Radiology 2010; 255:142–153

16. CBF maps show flow reduction in nearly the whole cortical
territory of the left MCA.
Temporal (B2), severe; parietal (B1), moderate to severe.
Color code: red, blood vessels; green, normal cortex; blue,
normal white matter; violet, low flow area).
61-year-old woman experienced acute
right hemiplegia and global aphasia
during coronary angiography.
Hopyan J, Ciarallo A, Dowlatshahi D, et al. Certainty of stroke diagnosis: incremental benefit with CT perfusion over noncontrast CT and CT angiography.
Radiology 2010; 255:142–153

17. TTP concentration of contrast enhancement maps show
time delay in the cortical territory of the left MCA and
artifact in areas where no peak is discernible.
Color code: blue, segmented blood vessels, normal cortex;
dark green, normal white matter; light green, yellow, and
red, low flow area).
61-year-old woman experienced acute
right hemiplegia and global aphasia
during coronary angiography.
Hopyan J, Ciarallo A, Dowlatshahi D, et al. Certainty of stroke diagnosis: incremental benefit with CT perfusion over noncontrast CT and CT angiography.
Radiology 2010; 255:142–153

18. CT PERFUSION PROTOCOL
 Arterial and venous regions of interest
(ROIs) and pre- and postenhancement
cutoff values are selected from the
perfusion CT source images to generate
representative arterial input and venous
outflow time-attenuation curves.
 The A2 segment of the anterior cerebral
artery is commonly used to obtain the
arterial input function (AIF) ROI because
it travels perpendicular to the axial plane.
 Similarly, the superior sagittal sinus can
be used to obtain the venous output
function (VOF) ROI.
Murayama K, Katada K, Nakane M, et al. Whole brain perfusion CT performed with a prototype 256-detector row CT system: initial experience. Radiology
2009; 250:202–211

19. Figure 3b. Perfusion CT software. (a) CT scan with superimposed labels illustrates semiautomatic selection of arterial (ACA or contralateral MCA) and
venous ROIs. (b) Graph illustrates time-attenuation curves for arterial (red) and venous (blue) ROIs.
RadioGraphics,
http://pubs.rsna.org/doi/abs/10.1148/rg.286085502
Published in: Enrique Marco de Lucas; Elena Sánchez; Agustín Gutiérrez; Andrés González Mandly; Eva Ruiz; Alejandro Fernández Flórez; Javier Izquierdo; Javier
Arnáiz; Tatiana Piedra; Natalia Valle; Itziar Bañales; Fernando Quintana; RadioGraphics 2008, 28, 1673-1687.
DOI: 10.1148/rg.286085502
© RSNA, 2008
One PowerPoint slide of each figure may be downloaded and used for educational, non-promotional purposes by an author for slide presentations only. The RSNA citation line must appear in at least 10-point type on
all figures in all presentations. Pharmaceutical and Medical Education companies must request permission to download and use slides, and authors and/or publishing companies using the slides for new article
creations for books or journals must apply for permission. For permission requests, please contact the publisher at permissions@rsna.org
Perfusion CT software : Graph illustrates time-attenuation curves for arterial (red)
and venous (blue) ROIs.
Mathematical modeling can be then used to calculate perfusion parameters and
generate color coded perfusion maps (deconvolution analysis)

20. CT PERFUSION INTERPRETATION
Acute Infarction
 Areas of decreased CBF and CBV, and
increased MTT and TTP.
 Matched perfusion abnormalities on CBV and
MTT maps correspond to areas of
nonsalvageable brain tissue and neuronal
death, also known as “core infarct”.
 Mismatched areas of prolonged MTT and
diminished CBF where CBV is relatively
preserved correspond to areas of salvageable
tissue, also called “ischemic penumbra”.
Murayama K, Katada K, Nakane M, et al. Whole brain perfusion CT performed with a prototype 256-detector row CT system: initial experience. Radiology
2009; 250:202–211

21. CT PERFUSION INTERPRETATION
Acute Infarction
 Because of compensatory
cerebrovascular mechanisms, many
patients are able to preserve CBV within
an area at risk for ischemic injury shortly
after the initial insult.
 Patients with areas of CBV-MTT
mismatch that are large or that involve
eloquent areas of brain may be good
candidates for reperfusion therapy.
 CBF may also be decreased to a lesser
degree within ischemic penumbra.
Murayama K, Katada K, Nakane M, et al. Whole brain perfusion CT performed with a prototype 256-detector row CT system: initial experience. Radiology
2009; 250:202–211

22. Murayama K, Katada K, Nakane M, et al. Whole brain perfusion CT performed with a prototype 256-detector row CT system: initial experience. Radiology
2009; 250:202–211

23. Mean transit time reveals prolongation
within same region (arrows)
51-year-old man who presented with
right facial droop and acute aphasia.
Cerebral blood flow reveals region
of decreased perfusion within left
middle cerebral artery (MCA)
territory
Cerebral blood volume shows
relative symmetric maintenance of
blood volume.

24. An example of applying the CT protocol to triage patients with acute ischemic stroke for
endovascular therapy-mm clot on the coronal ultrathin noncontrasted CT (middle).
Shang T , and Yavagal D R Neurology 2012;79:S86-S94
Copyright © 2012 by AAN Enterprises, Inc.

27. Acute stroke–induced cytotoxic edema in posterior, anterior and middle
cerebral infarction

28. Any abnormality???

30. CLINICAL APPLICATION OF DWI
 More sensitive for detection of hyperacute ischemia
 becomes abnormal within 30 minutes
 Distinguish b/w old and new stroke
 DWI should always be used with ADC to assess AGE OF
INFARCT

32. Pseudo-normalization of DWI in a 2 weeks old posterior infarction normal DWI.
On T2WI there is some subtle hyperintensity in the right occipital lobe in the vascular territory of
the posterior cerebral artery.
The T1WI after the administration of Gadolinium shows gyral enhancement

33. Time course of an ischemic infarction

35. large area with restricted diffusion in the territory of the right MCA
with involvement of the basal ganglia.
There is a perfect match with the perfusion images, so this patient should not
undergo any form of thrombolytic therapy

38. g
Acute stroke (6 hours evolution) in a 46-year-old woman with left
hemiplegia

39. Acute stroke (2 hours evolution) in a 46-year-old man with left
hemiparesis.

41. SUMMARY
The on-call radiologist has a key role in the
management of acute stroke.
A complete CT study (nonenhanced CT, perfusion CT,
and CT angiography) may be performed and
analyzed rapidly and easily by general radiologists
using a simple standardized protocol.
Hemorrhages should be ruled out at nonenhanced CT,
but time should not be lost in puzzling over subtle
early ischemic signs.
Perfusion CT can delineate the salvageable brain
tissue (mismatch), and CT angiography helps
detect vessel occlusion and collateral flow.

42. What do you see here? What do you expect on
CTA?

44. ?