Acute Ischemic Stroke : Infarct Core Estimation On Ct Angiography Source Images Depends On Ct Angiography Protocol Page 2

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NEURORADIOLOGY:
Infarct Core Estimation on CT Angiography Source Images Depends on Protocol
Pulli et al
A
lthough there remains no perfect
in past ( 4,5 ) and ongoing randomized
protocols to maximize arterial-phase
imaging technique for delineating
controlled clinical trials to select pa-
contrast enhancement ( 15,16 ). In our
infarction size and extent in the
tients for reperfusion therapy by using
institution, we increased table speed
acute setting, magnetic resonance (MR)
the mismatch concept and has been
and changed imaging direction to take
imaging with diffusion-weighted (DW)
used as the reference standard in lesion
full advantage of the new multisection
imaging is widely considered the best
volume–comparison studies between
scanners. However, faster image acqui-
imaging tool currently available. Com-
computed tomographic (CT) and MR
sition has been hypothesized to prevent
pared with other imaging approaches
imaging ( 6,7 ). However, performing
suffi cient delay time for a steady state
available in the treatment setting, DW
MR imaging in the acute setting is dif-
between arterial and tissue contrast
imaging possesses the highest accuracy
fi cult outside of major medical centers,
material to be reached, thus leading
for depicting acute brain ischemia ( 1 ),
largely because of time constraints.
to overestimation of infarct size ( 17 ).
and its use for the evaluation of pa-
In contrast to MR imaging units, CT
In support of this latter idea, a recent
tients with acute ischemic stroke is en-
scanners are more widely available in the
study ( 18 ) in which CT angiography
dorsed by multiple expert panels ( 2,3 ).
setting of immediate imaging in patients
source images were compared with
Moreover, DW imaging has been used
with acute stroke. Hypoattenuation at un-
perfusion CT images for measurement
to measure the infarct core, which is
enhanced CT in the acute setting has been
of CBV and cerebral blood fl ow (CBF)
defi ned as irreversibly damaged tissue,
shown to predict fi nal infarct volume ( 8 ),
demonstrated a better correlation of le-
but this test lacks sensitivity compared
sions on CT angiography source images
Advances in Knowledge
with DW imaging ( 1 ). CT angiography
with regions of depressed CBF.
source images, on the other hand, have
We sought to test whether the re-
In a consecutive series of 100
n
higher sensitivity in the detection of acute
lationship between ischemic lesion size
patients with acute ischemic
ischemia compared with unenhanced CT
on CT angiography source images and
stroke, infarct estimation on CT
images ( 9 ), and the extent of hypoattenu-
that on concurrently obtained DW MR
angiography source images was
ation on CT angiography source images
images is dependent on the CT angiog-
highly dependent on the CT angi-
correlates with not only the volume of
raphy acquisition protocol and to eval-
ography acquisition protocol; the
the region of hyperintensity at DW imag-
uate its potential effect on treatment
delay from contrast material in-
ing ( 10,11 ) but also with fi nal infarct vol-
decisions.
jection to imaging of the anterior
ume in patients who undergo successful
circulation territory ( P , .0001)
recanalization ( 12 ). It is thought that on
and atrial fi brillation ( P = .0002)
Published online before print
CT angiography source images, hypoat-
were independent predictors of
10.1148/radiol.11110896 Content code:
tenuation represents areas of the brain
signifi cant infarct overestimation
with depressed cerebral blood volume
Radiology 2012; 262:593–604
on CT angiography source images
(CBV) in steady-state contrast conditions
compared with estimation on
Abbreviations:
( 13,14 ). Therefore, hypoattenuation on
diffusion-weighted (DW) images.
CBF = cerebral blood fl ow
CT angiography source images offers the
CBV = cerebral blood volume
As compared with CT angiog-
n
promise of reliable estimation of acute in-
CI = confi dence interval
raphy source images acquired by
DW = diffusion weighted
farct size in the absence of DW imaging.
using relatively slower CT scan-
ICA = internal carotid artery
With the advent of multidetector
ners, when source images are
IQR = interquartile range
scanners, many hospitals have modi-
MCA = middle cerebral artery
acquired by using protocols
fi ed their CT angiography acquisition
NIHSSS = National Institutes of Health Stroke Scale Score
adapted to faster, multisection
tPA = tissue plasminogen activator
CT scanners, the reduced time
Implications for Patient Care
from contrast material injection
Author contributions:
to imaging leads to overestima-
The use of CT angiography
Guarantors of integrity of entire study, B.P., R.G.G., A.J.Y.;
n
study concepts/study design or data acquisition or data
tion of infarct size.
source images to estimate the
analysis/interpretation, all authors; manuscript drafting
size of irreversible tissue injury
The observed infarct overestima-
n
or manuscript revision for important intellectual content,
may lead to inappropriate
tion may be large (ratio of
all authors; manuscript fi nal version approval, all authors;
exclusion of patients from reper-
volume on CT angiography
literature research, B.P., Z.A.C., A.J.Y.; clinical studies, B.P.,
fusion therapy by incorrectly sug-
P.W.S., R.H., Z.A.C., M.H.L., A.J.Y.; statistical analysis, B.P.,
source images to volume on DW
gesting the presence of a large
Z.A.C., R.G.G., A.J.Y.; and manuscript editing, B.P., P.W.S.,
images, 3.5; median overestima-
Z.A.C., M.H.L., J.A.H., R.G.G., A.J.Y.
infarct.
tion, 54 mL), and, as compared
with patient selection performed
The use of CT angiography
Funding:
n
by using DW imaging, may lead
source imaging requires technical
This research was supported by the National Institutes
of Health (grants NS050041 and NS051343-01A2).
to inappropriate treatment
standardization before it can be
exclusion in 44.4%–90.3% of
used as a surrogate for DW
Potential confl icts of interest are listed at the end
patients.
imaging.
of this article.
594
Radiology: Volume 262: Number 2—February 2012
n

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