nnp 3 2012:Neurologia 1-2006.qxd 2012-06-27 14:08 Strona 233
ORIGINAL PAPER/ARTYKUŁ ORYGINALNY
Accuracy of transcranial colour-coded sonography in the diagnosis of anterior
cerebral artery vasospasm
SkutecznoSć przezczaszkowej ultrasonografii z przepływem krwi kodowanym kolorami
w diagnostyce skurczu tętnicy przedniej mózgu
Grzegorz Turek1, Jan Kochanowicz1,2, Robert Rutkowski1, Jaroslaw Krejza3,4,5, Tomasz Lyson1, Krzysztof Gorbacz1,
Justyna Zielinska-Turek6, Zenon Mariak1
1
Department of Neurosurgery, Medical University of Bialystok, Poland
2
Department of Invasive Neurology, Medical University of Bialystok, Poland
3
Department of Radiology, University of Pennsylvania, Philadelphia, USA
4
Imam University, Riyadh, Kingdom of Saudi Arabia
5
Department of Nuclear Medicine, Medical University of Gdansk, Poland
6
Department of Neurology, Medical University of Bialystok, Poland
Neurologia i Neurochirurgia Polska 2012; 46, 3: 233-238
DOI: 10.5114/ninp.2012.29131
Abstract Streszczenie
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Background and purpose: Transcranial colour-coded sono- Wstęp i cel pracy: PrędkoSć krwi w naczyniu zwiększa się
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graphy (TCCS) has been proven to be a method of high per- w czasie jego skurczu. Przezczaszkowa ultrasonografia dop-
plerowska z kodowanym kolorami przepływem krwi (trans-
formance in the diagnosis of spasm of the middle cerebral
cranial colour-coded sonography TCCS) to uznana metoda
artery (MCA). Relevant data concerning the anterior cere-
w diagnostyce skurczu tętnicy Srodkowej mózgu. Dane
bral artery (ACA) varies amongst studies. The aim of this
dotyczące czułoSci i swoistoSci tej metody w diagnostyce skur-
study was to assess the performance of TCCS in the diagno-
czu tętnicy przedniej mózgu nie są jednak jednoznaczne.
sis of spasm affecting the ACA.
Materiał i metody: Za pomocą TCCS wykonanej bezpo-
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Material and methods: Ninety-two patients (39 women and
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Srednio przed wykonaniem angiografii mózgowej zbadano
53 men, age 51 ą 12.1 years) were examined using TCCS
92 pacjentów. W badaniu wzięło udział 39 kobiet i 53 męż-
before cerebral angiography. Of 184 examined ACAs, only
czyzn (Srednia wieku: 51 ą 12,1 roku). Ze 184 badanych tęt-
133 arteries could be visualized due to insufficiency of the tem-
nic przednich mózgu tylko 133 mogły być uwidocznione
poral acoustic window. Therefore, only 15 out of 25 arteries
z powodu braku okienka akustycznego w koSci skroniowej.
in which vasospasm was diagnosed with angiography (by two
Z tego powodu spoSród 25 tętnic, w których angiograficznie
neuroradiologists not informed about the sonographic find-
stwierdzono skurcz naczyniowy (przez dwóch neuroradiolo-
ings) could be included in the analysis. Receiver operating
gów nieznających wyników sonograficznych), tylko 15 włą-
characteristic (ROC) curves were constructed for specific
czono do analizy statystycznej. Krzywą charakterystyki
blood flow velocities: peak systolic (PSV), mean (M) and end- odbiornika (ROC) wyliczono dla prędkoSci skurczowej, Sred-
diastolic (EDV). The area under the ROC curve was used to
niej oraz końcoworozkurczowej. WielkoSć pola pod krzywą
measure the overall diagnostic performance of TCCS. ROC odpowiadała skutecznoSci diagnostycznej TCCS.
Correspondence address: Grzegorz Turek, Department of Neurosurgery, Medical University of Bialystok, Skłodowskiej-Curie 24a, 15-276 Bialystok,
Poland, phone +48 696 45 47 53, fax +48 857 46 86 26, e-mail: turekgrzegorz@vp.pl
Received: 15.04.2011; accepted: 14.02.2012
233
Neurologia i Neurochirurgia Polska 2012; 46, 3
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nnp 3 2012:Neurologia 1-2006.qxd 2012-06-27 14:08 Strona 234
Grzegorz Turek, Jan Kochanowicz, Robert Rutkowski, Jaroslaw Krejza, Tomasz Lyson, Krzysztof Gorbacz, Justyna Zielinska-Turek, Zenon Mariak
Results: The area under the ROC curve for PSV was 0.83, Wyniki: WartoSć pola pod krzywą dla prędkoSci skurczowej
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which indicates good performance. The PSV threshold of krwi wyniosła 0,83, co odpowiada względnie wysokiej sku-
98 cm/s corresponded to maximum accuracy and was asso- tecznoSci metody w diagnostyce skurczu tętnicy przedniej
ciated with 71% sensitivity vs. 88% specificity. Average sys- mózgu. Największa skutecznoSć testu diagnostycznego zwią-
tolic blood flow velocity in the vessels with vasospasm was
zana jest z progiem prędkoSci skurczowej 98 cm/s, przy któ-
129 cm/s, whereas in unaffected vessels it was 76 cm/s.
rym czułoSć testu wynosi 71%, a swoistoSć 88%. PrędkoSć
Conclusions: The accuracy of TCCS in the diagnosis of
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skurczowa w naczyniach objętych skurczem wynosiła Sred-
ACA spasm is relatively high the value of the area under
nio 129 cm/s, a bez skurczu 76 cm/s.
the ROC amounts to 0.83. PSV performs best and the thresh-
Wnioski: SkutecznoSć TCCS w diagnostyce skurczu tętnicy
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old of 98 cm/s is associated with an optimal trade-off between
przedniej mózgu jest względnie wysoka wartoSć pola pod
sensitivity and specificity.
krzywą wynosi 0.83. Najlepszą relację czułoSci do swoistoSci
metody osiąga się, stosując diagnostyczny próg prędkoSci
Key words: cerebral vasospasm, anterior cerebral artery, tran-
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98 cm/s.
scranial colour-coded sonography, ROC curve.
Słowa kluczowe: skurcz naczyń mózgowych, tętnica przed-
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nia mózgu, przezczaszkowa ultrasonografia dopplerowska
z kodowanym kolorami przepływem krwi, krzywa ROC.
Introduction Material and methods
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Cerebral vasospasm is a frequent and dangerous com- We examined 92 patients in whom blood flow velo-
city was effectively sampled in 133 ACAs. The study group
plication of subarachnoid haemorrhage (SAH) [1-4].
consisted of 39 women and 53 men with a mean age of
Early diagnosis of spasm allows for the application of
51 ą 12.1 years (range 17-71 years). The age of 13 patients
aggressive medical therapy to prevent the development
was below 40 years, the next 57 fell into the age span
of critical brain ischaemia [1,3,5]. Digital subtraction
of 40-60 years, and 22 were older than 60 years. All
angiography is the most accurate reference method to
were hospitalized in the Department of Neurosurgery of
detect vasospasm but it is invasive and carries the risk
the Medical University of Bialystok, due to SAH
of stroke [6,7]. Because blood flow velocity increases in
(68 patients) and intracerebral haemorrhage (ICH)
a vessel affected by spasm, transcranial Doppler ultra-
(24 patients). All patients were examined clinically with
sonography (TCD), a widespread non-invasive technique,
digital cerebral angiography, which was performed soon
is commonly used to detect and monitor this condition,
after admission to detect and secure possible vascular mal-
despite some methodological problems and limited ac-
formation, and each of them underwent TCCS testing,
curacy [8-10]. Transcranial colour-coded sonography
directly before the angiographic examination. Testing in
(TCCS), which is a newer, more technologically advanced such an order was consequently observed to prevent sit-
technique, in some opinions is more suitable for the detec- uations in which any sort of treatment and/or interven-
tion could affect the status of cerebral vasculature or hemo-
tion of cerebral vasospasm because it enables the opera-
dynamic parameters. In our department, all patients with
tor to visualize the vessel in question in colour, to iden-
SAH and ICH are monitored with TCCS daily and we
tify the site of the highest velocity acceleration and to
perform the first examination as early as possible to obtain
obtain angle-corrected measurements of blood flow velo-
a basis for subsequent changes in the status of the cere-
cities [11-18]. Despite these technological advancements,
bral vasculature. In our hands, TCCS examination takes
imaging of the anterior cerebral artery (ACA) remains
5-10 minutes, so neither angiography nor aneurysm han-
difficult due to the small calibre and relatively awkward
dling was delayed to any significant degree. The pro-
and changeable course of this vessel.
gramme of the study was approved by the Ethics Com-
The accuracy of TCCS in the detection of ACA spasm,
mittee of the Medical University and all patients gave
however, has not yet been reliably established. The aim
their fully informed consent.
of our study was to assess the value of TCCS in the diag-
A Toshiba Aplio SSA 770A scanner endowed with
nosis of ACA vasospasm using cerebral angiography as
a 2.5 MHz probe was used for all sonographic exami-
a gold standard . nations. The A1 segments were insonated through the
234 Neurologia i Neurochirurgia Polska 2012; 46, 3
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nnp 3 2012:Neurologia 1-2006.qxd 2012-06-27 14:08 Strona 235
Sonographic diagnosis of ACA spasm
temporal acoustic window using methods we described of this approach, vasospasm of the A1 segment was diag-
elsewhere [11,19]. The mean, peak systolic, and end-dias- nosed in 14 patients and in 15 ACAs.
tolic velocities were calculated by tracing the maximum
frequency envelope of the Doppler waveform. The angle
Statistical analyses
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of insonation was visually adjusted to the vessel course
The Shapiro-Wilk test was used for testing the dis-
to obtain the angle-corrected blood flow velocity. Selec-
tribution of continuous variables. Student s t-test was used
tive intra-arterial digital subtraction angiography was per-
for testing hypotheses about mean values of two conti-
formed via the Seldinger approach through the femoral
nuous variables as the distribution of all tested variables
artery with the Argos 2M Mecall device [20]. The image
was found to be normal.
showing the most severe ACA narrowing was used for
Diagnostic accuracy of TCCS was assessed using the
comparison with TCCS findings. Two neuroradiologists
receiver operating characteristic (ROC) curve method
who were not familiar with the sonographic findings
[13,20,21]. The ROC curve is a plot of sensitivity against
reviewed the angiographs to detect the presence of cere-
1-specificity for a family of cut points that define posi-
bral vasospasm. Different degrees of focal ACA nar-
tive and negative values for a given test. The accuracy
rowing [i.e. mild up to 25% 11 ACAs (44%), mo-
of a test can be quantified by calculating the area under
derate from 25% to 50% 6 ACAs (24%) and severe
the ROC curve.
more than 50% 8 ACAs (32%)] were combined to
The area under the ROC curve was computed sepa-
form one group: vessels with vasospasm . Such grading
rately for each blood flow velocity (peak systolic, mean, and
of vasospasm was used to follow the set-up of our ear-
end-diastolic). Blood flow velocity thresholds were estab-
lier studies with TCCS in the diagnosis of middle cere-
lished that corresponded to the best efficiency of TCCS
bral artery (MCA) spasm [13,15,20].
as the diagnostic test. They were identified automatical-
Single-sided narrowing of the A1 segment was dia-
ly by the statistical software to represent the best trade-off
gnosed using angiography in 23 patients, whereas dou-
between maximum sensitivity and specificity. Both basic
ble-sided narrowing was present in one patient. Altogether,
statistics and the ROC curves were calculated and plot-
25 ACAs in 24 patients were classified as narrowed
ted with Statistica software for Windows. A probability of
(18.8%). In 6 of these patients, ultrasound examination
less than 0.05 was considered statistically significant.
was impossible due to insufficiency of the acoustic tem-
poral window, and as a consequence they could not be
included in the study group. There were 18 patients with
Results
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local ACA narrowing 11 of them had a transparent
acoustic window and they were directly included in the Table 1 shows mean value and standard deviation of
study. In 7 patients, the entire A1 segment was classified blood flow velocities calculated for the group of arteries
as narrow in comparison to the opposite ACA, and these with vasospasm as well as for the arteries which were unaf-
patients were referred for delayed angio-computed fected in the angiography. Blood flow velocity in the nar-
tomography (angio-CT) examinations. This study was rowed arteries was higher in comparison to the unaffected
performed 4-6 months after discharge by a radiologist vessels and the difference was statistically significant, as
blinded to earlier angiographic and TCCS results and tested with Student s t-test.
revealed persistent narrowing of the A1 segment (hypo- The ROC curves for all three blood flow velocities
plasia or atheromatosis) in 4 patients and a return to a nor- are shown in Fig. 1. The area under the curve for peak
mal artery calibre in 3 patients. Subsequently, these systolic velocity was 0.83. The mean and end-diastolic
3 patients were included in the analysis. As a consequence blood flow velocity showed worse performance in the diag-
Table 1. Mean value and standard deviations of particular blood flow velocities in the unaffected anterior cerebral arteries (ACAs) (Spasm ) and in the arteries
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with spasm (Spasm +). P probability: the result of t-test
Velocity (cm/s) No. of ACAs Spasm (+) Spasm ( ) P-value
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peak systolic 133 129 cm/s (ą 57) 76 cm/s (ą 25) 0.002
mean 133 76 cm/s (ą 36) 49 cm/s (ą 18) 0.008
end-diastolic 133 48 cm/s (ą 23) 32 cm/s (ą 15) 0.014
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Grzegorz Turek, Jan Kochanowicz, Robert Rutkowski, Jaroslaw Krejza, Tomasz Lyson, Krzysztof Gorbacz, Justyna Zielinska-Turek, Zenon Mariak
of patients with a sufficient temporal window. When based
1.0
on peak systolic blood velocity, the calculated area under
0.9
the ROC curve was 0.83. Because this parameter is uni-
versal, it allows the diagnostic performance of different
0.8
tests to be easily compared. For example, the corresponding
0.7
value for mammography (which is an accepted screening
examination for breast cancer) is 0.84 [22].
0.6
Our findings that the PSV value performs better in
0.5
the diagnosis of ACA vasospasm than the M and EDV
is in agreement with results obtained by other authors
0.4
[13,14]. It is also in agreement with reports that end-
0.3 diastolic velocity (and consequently mean velocity) is
more strongly influenced than peak systolic velocity by
0.2
Peak-systolic; A = 0.83; 0.71-0.94 (CI)
the status of the peripheral cerebral circulation [13]. As
Mean; A = 0.75; 0.62-0.88 (CI)
the microcirculation can be affected by many uncontroll-
0.1
End-diastolic A = 0.71; 0.58-0.85 (CI)
ed factors (such as normal aging, arteriosclerosis, hor-
0.0
monal status, intracranial pressure, etc.), false negative
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
results and less perfect sensitivity are more likely to appear
1-specificity
when using the end-diastolic velocity than the peak sys-
A area under the curve, CI confidence interval
tolic velocity values.
We found that the threshold of peak systolic veloci-
Fig. 1. Receiver operating characteristic curves for peak systolic, mean, and
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1
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end-diastolic blood flow velocity
ty amounting to 98 cm/s was associated with maximum
efficiency and the trade-off between sensitivity and
nosis of vasospasm in the ACA with the area under the
specificity equalled 0.71 and 0.88, respectively. This peak
ROC curve 0.75 and 0.71, respectively.
systolic velocity threshold can therefore be recommend-
The peak systolic velocity value associated with an
ed for optimal performance for the task of ACA spasm
optimal trade-off between specificity and sensitivity
diagnosis.
was established at 98 cm/s. This value is identified by Sta-
To our knowledge, there is only one study available
tistica software automatically. A sensitivity of 71% and
in the literature (by Proust et al.) dealing with the diag-
specificity of 88% corresponded to this blood flow
nosis of ACA spasm with colour-coded Doppler sono-
velocity threshold (Table 2). Table 2 also summarizes opti-
graphy [14]. Proust and colleagues identified a lower
mal thresholds for mean and end-diastolic blood flow
optimal peak systolic velocity threshold only 75 cm/s
velocity together with the corresponding sensitivity and
(though, interestingly, their associated sensitivity and speci-
specificity for these values. In accordance with their poor-
ficity were nearly the same as in our study: 0.71 and 0.84,
er diagnostic performance, the associated values of sen-
respectively). To discuss this discrepancy, it should be
sitivity and specificity were also found to be lower than
mentioned that Proust et al. based their study on a group
those related to peak systolic velocity.
of only 30 patients whereas our study group was more
numerous, comprising 92 patients. Also the prevalence
of ACA spasm was different in both studied populations:
Discussion
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in Proust s it was 11/30 patients whereas in ours it was
The value of TCCS in the screening of the ACA for
15/92 patients. And it is commonly known that preva-
spasm was found to be at least satisfactory in the group
lence of a diagnosed condition in a screened population
Table 2. Optimal thresholds of blood flow velocity to diagnose spasm of the anterior cerebral artery
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Velocity (cm/s) Velocity threshold Sensitivity Specificity
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peak systolic 98 cm/s 0.71 0.88
mean 55 cm/s 0.65 0.73
end-diastolic 44 cm/s 0.53 0.77
236 Neurologia i Neurochirurgia Polska 2012; 46, 3
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Sensitivity
nnp 3 2012:Neurologia 1-2006.qxd 2012-06-27 14:08 Strona 237
Sonographic diagnosis of ACA spasm
can significantly influence the result of studied diagnostic artery in 33. This constitutes 28% of arteries having
performance of a diagnostic method. It must also be not- escaped visualization with TCCS a sizable figure when
ed that Proust et al. established a velocity of 75 cm/s as compared to only 11% of MCAs which could not be visu-
an optimal diagnostic threshold for ACA spasm where- alized with this technique in a similar group of patients
as this velocity is lower than the mean peak systolic veloc- [13]. The above anatomical features (relatively small cal-
ity in a group of 182 healthy subjects (which was found ibre, awkward and changeable course, often significant
to be 79 cm/s) [23]. Our optimal performance peak sys- asymmetry) make the ACA apparently a much more dif-
tolic velocity value of 98 cm/s is by 20% higher than
ficult target for sonographic imaging in comparison with
the mean in healthy people, but still remains within the
MCA. It was shown that even in a group of 182 healt-
established span of normal reference values for ACA (37- hy subjects, as many as 14% of ACAs could not be visu-
121 cm/s). Needless to say, this overlap with the range
alized with TCCS, the same being true for only 8% of
of normal reference values explains why the sensitivity
MCAs [23]. The problem becomes even worse when the
and specificity associated with our diagnostic threshold
artery is in spasm because in this condition the course and
of peak systolic velocity is less than perfect.
calibre of the vessel in question changes unpredictably
It is of interest to add that the authors who used con- and the signal produced by the stream of flowing blood
ventional, i.e. blind , TCD for the diagnosis of ACA spasm
becomes weaker [11].
obtained very divergent and often useless figures of sen-
The low prevalence of moderate and severe ACA nar-
sitivity and specificity. For example, Lennihan et al. noted
rowing in our study group is obviously a result of ran-
13% sensitivity and 100% specificity [24]. Wozniak et al.
dom sampling of patients after SAH an approach sug-
had findings of 18% sensitivity and 65% specificity [18].
gested by Ransohoff and Feinstein [26]. Our patients
Only Kyoi Kikuo et al. reported 82% sensitivity and 71%
were usually referred for angiography shortly after their
specificity [24]. Lysakowski and Walder in their system-
admission to the hospital, when vasospasm was less like-
atic review published in Stroke concluded that as to the use-
ly to be advanced, whereas severe vasospasm usually devel-
fulness of blind transcranial Doppler in the diagnosis of
ops between the first and third weeks after SAH [1].
ACA spasm there had been & lack of evidence of either
Despite recent technical refinements, sonographic
accuracy or of any usefulness [12].
diagnosis of cerebral vasospasm is by no means straight-
Apparently, sonographic diagnosis of ACA spasm is
forward nor always reliable. Clinical application of TCD
a much more difficult task than when one is dealing with
is still considered primarily as a useful tool for screen-
MCA. That is why serious limitations of this methodo-
ing and not for definite diagnosis. Nevertheless, this
logy must be clearly indicated. The first is purely anato-
method is irreplaceable in daily monitoring of the patient
mical. The course of the anterior cerebral artery in its A1
and every increase of blood flow velocity in comparison
segment is changeable and to some extent unpredictable.
to the initial examination must be considered a sign of
The A1 usually runs in a more or less arcuate manner
ongoing cerebral vasospasm.
towards the midline, to the front and slightly upwards. Very
often, both segments are asymmetrical in their calibre, length
and course [25]. Especially mild to moderate vasospasm
Conclusions
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(< 50%) can escape detection because one may find it
difficult to localize any relatively straight section of the artery
1. In patients with a sufficient temporal window, the
to place the probe and to reliably measure the angle between
accuracy of TCCS in the diagnosis of spasm of the
the stream of blood and the sonographic beam. It must also
ACA is satisfactory, as expressed by the value of 0.83
be mentioned that according to some opinions vasospasm
of the area under the ROC curve. Twenty-eight per-
< 25% of a vessel calibre usually escapes sonographic detec- cent of ACAs cannot be visualized through the tem-
tion, to become detectable only when approaching 50% of
poral acoustic window.
the initial vessel calibre.
2. The best performing TCCS parameter in the detec-
Another problem that affects the general performance
tion of ACA spasm is peak systolic velocity. Maxi-
of TCCS in the diagnosis of ACA spasm is insufficien- mum efficiency (i.e. an optimal trade-off between sen-
cy of the temporal acoustic window. While being a prob- sitivity and specificity) is associated with a peak
lem inherited for every kind of transcranial sonography, systolic velocity diagnostic threshold of 98 cm/s.
it becomes even more serious with the visualization of the 3. The performance of TCCS in the diagnosis of ACA
ACA. Among our 92 patients (184 anterior cerebral arter- spasm does not match that established earlier for the
ies), no artery could be visualized in 9 subjects and one MCA.
237
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nnp 3 2012:Neurologia 1-2006.qxd 2012-06-27 14:08 Strona 238
Grzegorz Turek, Jan Kochanowicz, Robert Rutkowski, Jaroslaw Krejza, Tomasz Lyson, Krzysztof Gorbacz, Justyna Zielinska-Turek, Zenon Mariak
14. Proust F., Callonec F., Clavier E., et al. Usefulness of transcra-
Acknowledgments
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nial color-coded sonography in the diagnosis of cerebral
vasospasm. Stroke 1999; 30: 1091-1098.
This study was supported by the Medical Univer-
15. Krejza J., Mariak Z., Lewko J. Standardization of flow veloci-
sity of Bialystok grants N 3-55-772 and 3-55773.
ties with respect to age and sex improves the accuracy of tran-
scranial color Doppler sonography of middle cerebral artery spasm.
AJR 2003; 181: 245-252.
Disclosure
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16. Swiat M., Weigele J., Hurst R.W., et al. Middle cerebral artery
vasospasm: transcranial color-coded duplex sonography versus
Authors report no conflict of interest.
conventional nonimaging transcranial Doppler sonography.
Crit Care Med 2009; 37: 963-968.
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