Article

Carotid Artery Stenosis: Grayscale and Doppler Ultrasound Diagnosis???Society of Radiologists in Ultrasound Consensus Conference

Department of Radiology, University of Southern California (USC), Keck School of Medicine, USC University Hospital, Los Angeles, CA 90033, USA.
Ultrasound Quarterly (Impact Factor: 1.19). 12/2003; 19(4):190-8. DOI: 10.1097/00013644-200312000-00005
Source: PubMed
ABSTRACT
The Society of Radiologists in Ultrasound convened a multidisciplinary panel of experts in the field of vascular ultrasonography (US) to come to a consensus regarding Doppler US for assistance in the diagnosis of carotid artery stenosis. The panel's consensus statement is believed to represent a reasonable position on the basis of analysis of available literature and panelists' experience. Key elements of the statement include the following: First, all internal carotid artery (ICA) examinations should be performed with grayscale, color Doppler, and spectral Doppler US. Second, the degree of stenosis determined at grayscale and Doppler US should be stratified into the categories of normal (no stenosis), less than 50% stenosis, 50 to 69% stenosis, > or =70% stenosis to near occlusion, near occlusion, and total occlusion. Third, ICA peak systolic velocity (PSV) and the presence of plaque on grayscale and/or color Doppler images are primarily used in the diagnosis and grading of ICA stenosis. Two additional parameters (the ICA-to-common carotid artery PSV ratio and ICA end diastolic velocity) may also be used when clinical or technical factors raise concern that ICA PSV may not be representative of the extent of disease. Fourth, ICA should be diagnosed as normal when ICA PSV is less than 125 cm/second and no plaque or intimal thickening is visible, less than 50% stenosis when ICA PSV is less than 125 cm/second and plaque or intimal thickening is visible, 50 to 69% stenosis when ICA PSV is 125 to 230 cm/second and plaque is visible, > or =70% stenosis to near occlusion when ICA PSV is more than 230 cm/second and visible plaque and lumen narrowing are seen, near occlusion when there is a markedly narrowed lumen on color Doppler US, and total occlusion when there is no detectable patent lumen on grayscale US and no flow on spectral, power, and color Doppler US. Fifth, the final report should discuss velocity measurements and grayscale and color Doppler findings. Study limitations should be noted when they exist. The conclusion should state an estimated degree of ICA stenosis as reflected in these categories. The panel also considered various technical aspects of carotid US and methods for quality assessment, and identified several important unanswered questions meriting future research.

Full-text

Available from: Edward I Bluth
Edward G. Grant, MD
Carol B. Benson, MD
Gregory L. Moneta, MD
Andrei V. Alexandrov, MD, RVT
J. Dennis Baker, MD
Edward I. Bluth, MD
Barbara A. Carroll, MD
Michael Eliasziw, PhD
John Gocke, MD, MPH, RVT
Barbara S. Hertzberg, MD
Sandra Katanick, RN, RVT
Laurence Needleman, MD
John Pellerito, MD
Joseph F. Polak, MD
Kenneth S. Rholl, MD
Douglas L. Wooster, MD, RVT
Eugene Zierler, MD
Index terms:
Carotid arteries, flow dynamics
Carotid arteries, stenosis or
obstruction, 172.4311, 172.4312,
172.721
Carotid arteries, US, 172.12981,
172.12983, 172.12984
Special Reports
Published online before print
10.1148/radiol.2292030516
Radiology 2003; 229:340–346
1
From the Dept of Radiology, Univ of South-
ern California, Keck School of Medicine, USC
University Hospital, 1500 San Pablo St, Los
Angeles, CA 90033 (E.G.G.); Dept of Radiol-
ogy, Brigham and Women’s Hosp, Harvard
Med School, Boston, Mass (C.B.B., J.F.F.);
Dept of Surgery, Oregon Health and Science
Univ, Portland, Ore (G.L.M.); Cerebrovascu-
lar Ultrasound and Stroke Treatment Team,
Univ of Texas Houston Med School (A.V.A.);
Dept of Surgery, West Los Angeles VA Med
Ctr, Calif (J.D.B.); Dept of Radiology,
Ochsner Clinic, New Orleans, La (E.I.B.);
Dept of Radiology, Duke Univ Med School,
Durham, NC (B.A.C., B.S.H.); Dept of Biosta-
tistics, Univ of Calgary, Alberta, Canada
(M.E.); Midwest Heart Specialists Vascular
Lab and La Grange Memorial Vascular Labo-
ratory, Downers Grove, Ill (J.G.); Intersocietal
Accreditation Commission, Columbia, Md
(S.K.); Dept of Radiology, Thomas Jefferson
Univ, Philadelphia, Pa (L.N.); Dept of Radiol-
ogy, North Shore Univ Hosp, New York Univ
School of Med, NY (J.P.); Dept of Radiology,
Inova Alexandria Hosp, Va (K.S.R.); Dept of
Surgery, Univ of Toronto, Ontario, Canada
(D.L.W.); and Dept of Surgery, Univ of Wash-
ington Med School, Seattle (R.E.Z.). Received
Apr 1, 2003; revision requested May 7; revi-
sion received May 21; accepted May 22. Ad-
dress correspondence to E.G.G. (e-mail:
edgrant@usc.edu).
©
RSNA, 2003
Carotid Artery Stenosis:
Gray-Scale and Doppler US
Diagnosis—Society of
Radiologists in Ultrasound
Consensus Conference
1
The Society of Radiologists in Ultrasound convened a multidisciplinary panel of
experts in the field of vascular ultrasonography (US) to come to a consensus
regarding Doppler US for assistance in the diagnosis of carotid artery stenosis. The
panel’s consensus statement is believed to represent a reasonable position on the
basis of analysis of available literature and panelists’ experience. Key elements of the
statement include the following: (a) All internal carotid artery (ICA) examinations
should be performed with gray-scale, color Doppler, and spectral Doppler US.
(b) The degree of stenosis determined at gray-scale and Doppler US should be
stratified into the categories of normal (no stenosis), 50% stenosis, 50%– 69%
stenosis, 70% stenosis to near occlusion, near occlusion, and total occlusion.
(c) ICA peak systolic velocity (PSV) and presence of plaque on gray-scale and/or
color Doppler images are primarily used in diagnosis and grading of ICA stenosis;
two additional parameters, ICA-to–common carotid artery PSV ratio and ICA end-
diastolic velocity may also be used when clinical or technical factors raise concern
that ICA PSV may not be representative of the extent of disease. (d) ICA should be
diagnosed as (i) normal when ICA PSV is less than 125 cm/sec and no plaque or
intimal thickening is visible; (ii) 50% stenosis when ICA PSV is less than 125 cm/sec
and plaque or intimal thickening is visible; (iii) 50%– 69% stenosis when ICA PSV is
125–230 cm/sec and plaque is visible; (iv) 70% stenosis to near occlusion when
ICA PSV is greater than 230 cm/sec and visible plaque and lumen narrowing are
seen; (v) near occlusion when there is a markedly narrowed lumen at color Doppler
US; and (vi) total occlusion when there is no detectable patent lumen at gray-scale
US and no flow at spectral, power, and color Doppler US. (e) The final report should
discuss velocity measurements and gray-scale and color Doppler findings. Study
limitations should be noted when they exist. The conclusion should state an esti-
mated degree of ICA stenosis as reflected in the above categories. The panel also
considered various technical aspects of carotid US and methods for quality assess-
ment and identified several important unanswered questions meriting future re-
search.
©
RSNA, 2003
A panel of experts from a variety of medical specialties was convened under the auspices
of the Society of Radiologists in Ultrasound to arrive at a consensus about the performance
of Doppler ultrasonography (US) to aid in diagnosis of internal carotid artery (ICA)
stenosis. The panel met in San Francisco, Calif, October 22–23, 2002, and drew up a
consensus statement. Although there are several facets of carotid disease that could be
considered by such a panel, carotid stenosis (and by extension, carotid occlusion) is by far
the most common pathologic process involving carotid arteries. Furthermore, the clinical
suspicion of ICA stenosis is responsible for most of the referrals for carotid imaging.
Authors of recent major studies have shown a decrease in stroke risk when carotid
endarterectomy is performed for carotid stenosis (1–4).
The performance of carotid US and the interpretation of US results vary considerably
340
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from laboratory to laboratory (5). Accred-
itation of vascular laboratories has re-
sulted in an increased degree of standard-
ization of the carotid US examination,
but a wide range of practice patterns still
exist. The goal of the conference was to
develop recommendations for the perfor-
mance of Doppler US and interpretation
of the results in the diagnosis of ICA ste-
nosis. The panel limited its discussion to
atherosclerotic stenosis of the ICA at or
just beyond the carotid bifurcation and
to vessels without prior intervention.
METHODS AND CONFERENCE
PREPARATIONS
Conference Participants
Prior to the meeting, 30 representative
articles were selected by the moderator
(E.G.G.) and sent to conference partici-
pants, along with a summary spreadsheet
with such information as the purpose of
the research, the statistical methods
used, and the pertinent results and con-
clusions (Tables 1, 2) (6 26). The panel
consisted of a moderator and 16 panelists
from various medical specialties.
Background and Summary of the
Literature
Historically, clinical studies of carotid
artery disease have classified patients in
two groups: symptomatic and asymp-
tomatic. The former group of patients
typically has had a neurologic event
(stroke, transient ischemic attack, or am-
aurosis fugax) secondary to cerebral isch-
emia, likely as a result of an embolic
event arising from atherosclerotic disease
at the carotid bifurcation. Patients in this
group have formed the basis for such
well-known studies as the North Ameri-
can Symptomatic Carotid Endarterec-
tomy Trial (1) and the European Symp-
tomatic Carotid Trial (3).
The asymptomatic group includes pa-
tients who have not had a neurologic
event. The seminal investigation in this
population, the Asymptomatic Carotid
Artery Study (2), included patients who,
though they had not had a neurologic
event, typically had clinical markers for
diffuse atherosclerosis. Overall, the prev-
alence of significant (50%) stenotic dis-
ease in symptomatic patients is stated as
being in the range of 18%–20% (27,28),
while the prevalence in asymptomatic
patients referred for carotid imaging is
14% (29). The prevalence of ICA disease
in the asymptomatic group, therefore,
approaches that found in symptomatic
patients.
Doppler US is by far the most common
imaging examination performed world-
wide to aid in the diagnosis of carotid
disease. Given the prevalence of patients
with carotid disease and the frequency
with which patients are referred for ca-
rotid imaging, the number of carotid US
examinations performed annually is con-
siderable (22). This imaging modality is
increasingly becoming the only exami-
nation performed before surgical inter-
vention. It was estimated by the panelists
that as many as 80% of patients in the
United States undergo carotid endarter-
ectomy after a US examination as the
only preoperative imaging study. There-
fore, it is of utmost importance that in-
formation provided by the US examina-
tion be reproducible and reliable.
Considerable gains have been made in
the quality of US examinations of the
carotid arteries over the past 2 decades.
The technology has experienced great ad-
vances in equipment, ranging from con-
tinued improvements in gray-scale reso-
lution to landmark advances in Doppler
methods, including color Doppler imag-
ing. The imaging community has gained
expertise in performance of carotid US
and interpretation of the results through
widespread use of technology, research,
and continuing medical education. In
addition, various accrediting bodies have
been established by groups such as the
Intersocietal Commission for Accredita-
tion of Vascular Laboratories, the Ameri-
can Institute of Ultrasound in Medicine,
and the American College of Radiology
in an attempt to improve and standard-
ize the quality of vascular US examina-
tions.
Despite improvements and advances,
TABLE 1
Literature Review of Doppler US Thresholds and Performance in Diagnosis of ICA Stenosis
Study and Year
Threshold Performance
Stenosis
(%)
PSV
(cm/sec)
EDV
(cm/sec) Ratio
Sensitivity
(%)
Specicity
(%)
PPV
(%)
NPV
(%)
Accuracy
(%)
Huston et al (6), 2000 50 130 . . . 1.6 92 90 90 91 91
70 230 70 3.2 86 90 83 92 89
Grant et al (7), 1999 60 200 . . . 3 AP* AP* AP* AP* AP*
70 175 . . . 2.5 SP* SP* SP* SP* SP*
Abu Rahma et al (8), 1998 50 140 . . . . . . 92 95 97 89 93
60 150 65 . . . 82 97 96 86 90
70 150 90 . . . 85 95 91 92 92
Carpenter et al (9), 1996 70 210 . . . . . . 94 77 68 96 83
70 . . . 70 . . . 92 60 73 86 77
70 . . . . . . 3.3 100 65 65 100 79
Hood et al (10), 1996 70 130 100 . . . 78 97 88 94 93
Carpenter et al (11), 1995 60 170 . . . . . . 98 87 88 98 92
60 . . . 40 . . . 97 52 86 86 86
60 . . . . . . 2.0 97 73 78 96 76
60 230 40 2.0 100 100 100 100 100
Browerman et al (12), 1995 70 175 . . . . . . 91 60 . . . . . . . . .
Moneta et al (13), 1995 60 260 70 3.23.5 84 94 92 88 90
Neale et al (14), 1994 70 270 110 . . . 96 91 . . . . . . 93
Moneta et al (15), 1993 70 325 130 . . . 83 90 80 92 88
Note.EDV end diastolic velocity in ICA, NPV negative predictive value, PPV positive predictive value, PSV peak systolic velocity in ICA. Ratio
is ICA PSV to distal common carotid artery (CCA) PSV.
*AP asymptomatic patients, SP symptomatic patients. Thresholds based on outcome sensitivity/specicity accuracy.
Volume 229
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the consensus panel agreed that, overall,
carotid US is often performed inconsis-
tently within a given laboratory, and
there is nonuniformity in practice from
one laboratory to the next. In many set-
tings, interpretive criteria for carotid ste-
nosis are either indiscriminately applied
or the interpreters are uncertain about
exactly how to make the diagnosis of ca-
rotid stenosis.
CONSENSUS CONFERENCE
The results of the consensus conference
regarding performance of carotid US and
interpretation of the results and the diag-
nosis of ICA stenosis can be summarized
into six key areas: (a) technical consider-
ations, (b) diagnostic strata, (c) imaging
and Doppler parameters, (d) Doppler di-
agnostic thresholds; (e) the nal report of
the gray-scale and Doppler US examina-
tions, and (f) quality assessment. The
panel identied a number of issues re-
lated to performance of carotid US and
interpretation of the results and made
recommendations to address these issues.
Technical Considerations
Standardization
Issue.The performance of carotid US
examinations is not standardized from
laboratory to laboratory. Even within a
given laboratory, there is often a failure
to follow a consistent protocol.
Recommendation.Examinations of the
ICA should be performed with gray-scale,
color Doppler, and spectral Doppler US in
a standardized fashion, according to a rig-
idly applied laboratory protocol, in accor-
dance with the standards of one of the
accrediting bodies. The panel encourages
all sonographers performing carotid US to
become credentialed as vascular technolo-
gists.
Positioning and Angulation
Issue.Errors in positioning the Dopp-
ler gate and in accounting for the Dopp-
ler angle are common in current clinical
practices. Since interpretative criteria for
carotid stenosis are heavily based on
Doppler velocities, errors in Doppler po-
sition and angle correction will lead to
serious errors in diagnosis.
Recommendation.The Doppler wave-
form should be obtained with an angle of
insonation less than or equal to 60°,as
measurements obtained with an angle of
insonation greater than 60° are likely to
be inaccurate, even with appropriate an-
gle adjustment, because of the physical
properties of Doppler.
Conflicting opinions.Some believed
that maintaining a constant angle of in-
sonation of exactly 60° would provide
greater consistency. Other panelists did
not agree that a xed angle of insonation
for all carotid US examinations is re-
quired and instead expressed that it is
necessary only to maintain an angle of
less than or equal to 60°. It was thought
that further investigation on this matter
is warranted.
Sample Volume Position
Issue.Other common technical short-
comings in ICA examinations include in-
correct positioning of the sample volume,
incomplete sampling through an area of
stenosis, and failure to depict the distal end
of a carotid plaque.
Recommendation.Care should be taken
to position the sample volume within the
area of greatest stenosis. The ICA must be
sampled through the region of stenosis
completely until the distal end of the
plaque is visualized, to ensure that the site
of highest velocity has been located.
Patient Considerations
Issue.Several errors may result from
problems inherent to the patient, such as
extensive plaque calcication, severe ICA
tortuosity, and tandem lesions.
Recommendation.It is important to
recognize these patient conditions and
understand that, in such cases, the exam-
ination may be limited.
TABLE 2
Other Pertinent Literature on ICA Stenosis
Study and Year
Threshold Chosen*
Assessment and ResultsStenosis (%) PSV (cm/sec) Ratio
Umemura and Yamada
(16), 2001
NA NA NA Evaluated results of B-ow imaging without Doppler
Perkins et al (17), 2000 NA NA NA Survey results show that laboratories use inconsistent
thresholds
Grant et al (18), 2000 NA NA NA Doppler US cannot be used to estimate a single degree of
stenosis but is better for differentiating less than or
more than a single degree of stenosis
Beebe et al (19), 1999 NA NA NA Color and gray scale perform well alone; Doppler helps
for midrange lesions
Soulez et al (20), 1999 70, 60 NA 3.4, 2.9 Ratio of ICA PSV at and distal to stenosis performs better
than ICA/CCA ratio
Ranke et al (21), 1999 70 NA NA Ratio of ICA PSV at stenosis to that distal to stenosis:
sensitivity, 97%, specicity, 98%
Derdeyn and Powers
(22), 1996
60 230 NA Evaluation of cost-effectiveness of asymptomatic screening
Griewig et al (23), 1996 NA NA NA Power Doppler better than color Doppler (not quantied)
Srinivasan et al (24),
1995
NA NA NA Doppler poor for differentiating degree of 50% stenosis
Hunink et al (25), 1993 70 230 NA PSV best parameter for predicting 70% stenosis
Bluth et al (26), 1988 NA NA NA EDV best Doppler parameter; did not use NASCET
angiography criteria
*NA not applicable.
Ratio is ICA PSV to distal CCA PSV.
NASCET North American Symptomatic Carotid Endarterectomy Trial.
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November 2003 Grant et al
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Page 3
Equipment
Issue.There is substantial variability
in equipment from machine to machine,
from manufacturer to manufacturer, and
between older and newer equipment
(3033). This variability in equipment
may explain, in part, the lack of agree-
ment and inconsistency in the literature
concerning Doppler thresholds for the
diagnosis of carotid stenosis.
Recommendation.The panel encourages
US equipment manufacturers to mini-
mize equipment variability by establish-
ing industry-wide standards for Doppler
measurement and calibration and the de-
velopment of a reliable Doppler phan-
tom that can be made readily available to
industry and to vascular laboratories.
Diagnostic Strata
Methods of Reporting
Issue.Methods by which the degree
of ICA stenosis is reported vary from lab-
oratory to laboratory, as well as within
some laboratories. Some report an esti-
mate of the specic percentage of steno-
sis, others stratify their estimates into ve
or six diagnostic categories or gradations
of stenosis.
Recommendation.Doppler US cannot
be used to predict a single percentage of
stenosis. Therefore, the consensus panel-
ists strongly recommend the use of de-
ned diagnostic strata. Laboratories
should establish protocols for stratifying
the degree of ICA stenosis, and, once es-
tablished, these criteria should be consis-
tently applied.
Doppler Measurement Variability
Although investigators have conrmed
that the average Doppler velocity rises in
direct proportion to the degree of steno-
sis as determined with angiography
(18,26), there are very wide ranges of
Doppler values around those means,
which makes it impossible to classify le-
sions into gradations as narrow as 10%
(Figure) (18,34). Even in evaluations of
the ability of Doppler US to help estimate
the degree of stenosis by using more ex-
panded strata (eg, 50%, 50%69%, and
70% stenosis), the ndings have been
disappointing. US is most accurate when
lesions are classied as being above or
below a single level, such as 60% stenosis
or 70% stenosis (18).
Stenosis of Less than 50%
Issue.In many laboratories, stratica-
tion or diagnosis of minor (50%) de-
grees of ICA stenosis is based on Doppler
ndings.
Recommendation.Because Doppler is
inaccurate for subcategorizing stenoses
less than 50%, these stenoses should be
reported under a single category as
50% stenosis. Subcategories for mi-
nor degrees of stenosis should not be
used.
Stratification of Stenoses
Issue.How should reporting of ICA
stenosis be stratied?
Recommendation.The consensus panel
recommends stratication of the degree
of stenosis on the basis of gray-scale and
Doppler US results into the following
strata: normal (no stenosis), 50% steno-
sis, 50% 69% stenosis, 70% stenosis
but less than near occlusion, near occlu-
sion, and total occlusion.
Discussion.The threshold of 70% ste-
nosis was chosen because it was believed
to be the threshold currently used by
most major vascular centers for surgical
intervention. The panel agreed, however,
that in some laboratories, there may be a
compelling reason to choose a different
stratication scheme. The diagnoses of
near occlusion and total occlusion are
usually not based primarily on the Dopp-
ler measurement of velocity but rather on
gray-scale and color and/or power Dopp-
ler imaging.
Imaging and Doppler Parameters
Key Components of ICA
Examination
Issue.What are the key components
of the US examination of the ICA?
Recommendation.The ICA US exami-
nation should consist of gray-scale imag-
ing, color Doppler imaging, and spectral
Doppler velocity determination. Because
stenosis is typically an area of narrowing
caused by plaque, with a focal area of
increased velocity and a poststenotic dis-
turbed ow, the location and character-
istics of plaque in the ICA should be de-
termined. The color Doppler appearance
of the lumen should also be assessed.
Primary US Parameters
Issue.Numerous imaging and Dopp-
ler parameters are currently used at vari-
ous laboratories for the evaluation of ICA
stenosis, including ICA PSV, ICA EDV
and ICA/CCA PSV ratio, CCA EDV, and
ICA/CCA EDV ratio. The application of
these parameters for diagnosis of ICA ste-
nosis varies from laboratory to laboratory
and sometimes within a given labora-
tory.
Recommendation.The panel suggested
that the ICA PSV and the presence of
plaque on gray-scale and/or color Dopp-
ler US images are the parameters that
should be used when diagnosing and
grading ICA stenosis.
Discussion.The ICA PSV is easy to ob-
tain and has good reproducibility and
should be used in conjunction with avail-
able gray-scale and color Doppler informa-
tion to ensure concordance of diagnostic
information. The degree of stenosis esti-
mated by using ICA PSV and the degree
of narrowing of the ICA lumen on gray-
scale and color Doppler images should be
similar.
Graph demonstrates the relationship between mean PSV and percent-
age of stenosis as measured arteriographically. PSV increases with
increasing severity of stenosis. Note marked overlap in adjacent cat-
egories of stenosis. Error bars 1 SD about the mean. (Reprinted, with
permission, from reference 18.)
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Additional US Parameters
Issue.Should other Doppler parame-
ters be used and, if so, when?
Recommendation.Two additional pa-
rameters, ICA/CCA PSV ratio and ICA
EDV, are useful for internal checks or
may be used when ICA PSV may not be
representative of the extent of disease
owing to technical or clinical factors such
as in the presence of tandem lesions, con-
tralateral high-grade stenosis, discrep-
ancy between visual assessment of
plaque and ICA PSV, elevated CCA veloc-
ity, hyperdynamic cardiac state, or low
cardiac output. For example, in a patient
with low cardiac output, the ICA PSV
may be disproportionately low when
compared with the ICA/CCA PSV ratio.
This discrepancy should prompt the in-
terpreter to consider all gray-scale and
Doppler information when stratifying
the degree of ICA stenosis. In particular
in such cases, the interpretation should
be based more heavily on the ICA/CCA
PSV ratio than on absolute values such as
the ICA PSV or ICA EDV. The panel be-
lieved that outlining the reasons for mak-
ing diagnostic choices that are not in
keeping with usual practice should be in-
cluded in the nal report.
Doppler Diagnostic Thresholds
Issue.Published literature is replete
with velocity thresholds for categorizing
ICA stenosis (Table 1). Tremendous vari-
ation exists among these studies in the
methods used to assess individual Dopp-
ler parameters and in the thresholds rec-
ommended for diagnosing ICA stenosis
(7).
Recommendation.The consensus panel
developed recommendations for diagnosis
and stratication of ICA stenosis (Table 3).
These recommendations were derived
from analysis of numerous studies and
do not represent the results of any one
laboratory or study. For a particular lab-
oratory setting, internal validation is en-
couraged when possible. This may yield
alternative diagnostic criteria that can be
used successfully at that facility. How-
ever, each laboratory should have a sin-
gle set of diagnostic criteria that is ap-
plied uniformly. The following points are
included in Table 3 and should be con-
sidered in the diagnosis of ICA stenosis:
1. The ICA is considered normal when
ICA PSV is less than 125 cm/sec and no
plaque or intimal thickening is visible
sonographically. Additional criteria in-
clude ICA/CCA PSV ratio 2.0 and ICA
EDV 40 cm/sec.
2. A <50% ICA stenosis is diagnosed
when ICA PSV is less than 125 cm/sec
and plaque or intimal thickening is visi-
ble sonographically. Additional criteria
include ICA/CCA PSV ratio 2.0 and
ICA EDV 40 cm/sec.
3. A 50%– 69% ICA stenosis is diag-
nosed when ICA PSV is 125230 cm/sec
and plaque is visible sonographically. Ad-
ditional criteria include ICA/CCA PSV ra-
tio of 2.0 4.0 and ICA EDV of 40 100
cm/sec.
4. A >70% ICA stenosis but less than
near occlusion of the ICA is diagnosed
when the ICA PSV is greater than 230
cm/sec and visible plaque and luminal
narrowing are seen at gray-scale and
color Doppler US. Additional criteria in-
clude ICA/CCA PSV ratio 4 and ICA
EDV 100 cm/sec. The higher the Dopp-
ler parameter lies above the threshold of
230 cm/sec, the greater the likelihood of
severe disease.
5. In cases of near occlusion of the
ICA, the velocity parameters may not ap-
ply, since velocities may be high, low, or
undetectable. This diagnosis is estab-
lished primarily by demonstrating a
markedly narrowed lumen at color or
power Doppler US (35).
6. Total occlusion of the ICA should
be suspected when there is no detectable
patent lumen at gray-scale US and no
ow with spectral, power, and color
Doppler US. Magnetic resonance (MR)
angiography, computed tomographic (CT)
angiography, or conventional angiogra-
phy may be used for conrmation in this
setting (35).
Final Report of the Gray-Scale and
Doppler US Examination
Issue.The structure and content of -
nal reports of carotid US examinations
vary greatly from laboratory to labora-
tory, as well as within given laboratories.
Recommendation.The nal report of
the gray-scale and Doppler US interpreta-
tion of the ICA examination should in-
clude the following:
Body of the report.(a) Pertinent US
ndings, including velocity measure-
ments and gray-scale ndings (presence,
location, and characteristics of ICA
plaque), as well as color Doppler ndings
when appropriate; (b) comments about
limitations of the study or deviations
from usual interpretive criteria due to
technical factors or hemodynamic con-
siderations; and (c) comparison with re-
sults of prior studies.
Conclusion or impression.Estimated
degree of ICA stenosis, categorized by the
laboratorys established diagnostic crite-
ria (modied, as appropriate, by techni-
cal factors or hemodynamic consider-
ations).
Quality Assessment
Need for Quality Assessment
Issue.Should every laboratory have a
system for quality assessment?
Recommendation.All laboratories should
institute a program of quality assessment.
Internal Validation of Doppler
Thresholds
Issue.Development of internally val-
idated Doppler thresholds may be dif-
cult given the infrequency of correlative
angiograms at most institutions.
Recommendation.The panel agreed
that it may not always be feasible to ob-
tain angiographic or clinical correlation
for quality assessment of US studies at
TABLE 3
Consensus Panel Gray-Scale and Doppler US Criteria for Diagnosis
of ICA Stenosis
Degree of
Stenosis (%)
Primary Parameters Additional Parameters
ICA PSV
(cm/sec)
Plaque Estimate
(%)*
ICA/CCA PSV
Ratio
ICA EDV
(cm/sec)
Normal 125 None 2.0 40
50 125 50 2.0 40
5069 125230 50 2.04.0 40100
70 but less than
near occlusion
230 50 4.0 100
Near occlusion High, low, or
undetectable
Visible Variable Variable
Total occlusion Undetectable Visible, no
detectable
lumen
Not applicable Not applicable
* Plaque estimate (diameter reduction) with gray-scale and color Doppler US.
344
Radiology
November 2003 Grant et al
R
adiology
Page 5
each laboratory. For this reason, the con-
sensus panel developed the table of rec-
ommended Doppler thresholds for diag-
nosis of ICA stenosis (Table 3), which can
be applied at laboratories that cannot val-
idate their own Doppler thresholds on
the basis of correlative imaging or clinical
information.
Discussion: Although angiography has
historically been considered the gold
standard for assessing Doppler thresh-
olds for various degrees of ICA stenosis,
few angiographic examinations are still
performed. Those that are performed at a
given institution are probably not repre-
sentative cases, but rather those cases in
which the US results were equivocal or
otherwise problematic. The use of CT an-
giography and MR angiography for cor-
relation has not, as yet, been fully vali-
dated (36).
Reference Standard
Issue.When angiography is used as
the reference standard for assessment of
Doppler criteria for ICA stenosis, differ-
ent techniques for measuring ICA steno-
sis have been used.
Recommendation.The panel recom-
mended that the NASCET method of ca-
rotid stenosis measurement should be
employed when angiography is used to
correlate the US ndings.
Discussion.In this method, the nar-
rowest portion of the vascular lumen was
compared with the normalized lumen
distally (37). In the European Symptom-
atic Carotid Trial study and studies per-
formed prior to the NASCET study, the
degree of stenosis was determined by
comparing the narrowest diameter of the
residual lumen to an estimate of the orig-
inal lumen in the same area. Because the
original lumen cannot be depicted on the
angiogram, exact measurement is impos-
sible. While the NASCET method of mea-
surement may not reect the burden of
atherosclerosis in the proximal ICA, it
does minimize the amount of interob-
server variability.
OTHER CONSIDERATIONS
Patient Surveillance
The panel discussed the issue of appro-
priate follow-up of asymptomatic pa-
tients with known ICA stenosis, as well as
of patients at high risk for ICA stenosis or
stroke. The panelists agreed that patients
with a 50% stenosis of the ICA who do
not undergo carotid endarterectomy and
who may be candidates for prophylactic
carotid endarterectomy should be fol-
lowed up at 6 12-month intervals, and
high-risk patients with visible plaque and
50% stenosis should be evaluated every
12 years. Patients who have normal ca-
rotid US studies but marked risk factors
might be evaluated every 35 years. In all
cases of follow-up or surveillance, a com-
plete examination should be performed.
Follow-up studies should be compared
with results from prior examinations.
Research Topics
The panel identied several important
unanswered questions that merit future
research.
1. What is the role of ICA plaque char-
acterization in carotid disease?
2. What is the role of the ICA intimal-
medial thickness? There are several ongo-
ing large clinical trials in which the inti-
mal-medial thickness is being evaluated
as a marker of atherosclerotic disease, but
there are not yet enough data to establish
the role of this measurement in the as-
sessment of carotid disease in individual
patients.
3. At follow-up examination, how
much of a change in estimated ICA ste-
nosis or ICA PSV should be considered
relevant?
4. What criteria should be used to as-
sess patients after ICA surgery or stent
placement?
5. Should US be used to screen for ca-
rotid disease?
Other issues that need to be addressed
include the following:
1. There is considerable variation in
Doppler measurements from machine to
machine and manufacturer to manufac-
ture. This should be rectied, because
such variation leads to inconsistencies
and inaccuracies in diagnosing ICA ste-
nosis.
2. Phantoms for Doppler US need to
be developed to facilitate calibration of
Doppler US equipment.
3. Improved methods for calculating
velocity with angle correction should be
developed to eliminate or minimize the
inconsistency in velocity measurements
as the Doppler angle of insonation is
changed.
4. Reliable quality assessment meth-
ods should be developed so that labora-
tories can assess their performance of the
carotid US examination. This should lead
to greater consistency in the performance
of carotid US within each laboratory, as
well as from laboratory to laboratory.
References
1. North American Symptomatic Carotid
Endarterectomy Trial collaborators. Bene-
cial effect of carotid endarterectomy in
symptomatic patients with high-grade ca-
rotid stenosis. N Engl J Med 1991; 325:
445453.
2. Executive Committee for the Asymptom-
atic Carotid Atherosclerosis Study. Endar-
terectomy for asymptomatic carotid ar-
tery stenosis. JAMA 1995; 273:1421
1428.
3. European Carotid Surgery Trialists Collab-
orative Group. MRC European Carotid Sur-
gery Trial: interim results for symptomatic
patients with severe (7099%) or with mild
(029%) carotid stenosis. Lancet 1991; 337:
12351243.
4. Barnett HJM, Taylor DW, Eliasziw M, et
al. Benet of carotid endarterectomy in
patients with symptomatic moderate or
severe stenosis. N Engl J Med 1998; 339:
14151425.
5. Byrd S, Robless P, Baxter A, Emson M,
Halliday A. Carotid duplex ultrasonogra-
phy: importance of standardisation. Int
Angiol 1998; 17:248254.
6. Huston J III, James EM, Brown RD Jr, et al.
Redened duplex ultrasonographic crite-
ria for diagnosis of carotid artery stenosis.
Mayo Clin Proc 2000; 75:11331140.
7. Grant EG, Duerinckx AJ, El Saden S, et al.
Doppler sonographic parameters for de-
tection of carotid stenosis: is there an op-
timum method for their selection? AJR
Am J Roentgenol 1999; 172:11231129.
8. AbuRahma AF, Robinson PA, Strickler DL,
Alberts S, Young L. Proposed new duplex
classication for threshold stenoses used
in various symptomatic and asymptom-
atic carotid endarterectomy trials. Ann
Vasc Surg 1998; 12:349358.
9. Carpenter JP, Lexa FJ, Davis JT. Determi-
nation of duplex Doppler ultrasound cri-
teria appropriate to the North American
Symptomatic Carotid Endarterectomy
Trial. Stroke 1996; 27:695699.
10. Hood DB, Mattos MA, Mansour A, et al.
Prospective evaluation of new duplex cri-
teria to identify 70% internal carotid ar-
tery stenosis. J Vasc Surg 1996; 23:254
261.
11. Carpenter JP, Lexa FJ, Davis JT. Determi-
nation of sixty percent or greater carotid
artery stenosis by duplex Doppler ultra-
sonography. J Vasc Surg 1995; 22:697
703.
12. Browman MW, Cooperberg PL, Harrison
PB, Marsh JI, Mallek N. Duplex ultrasonog-
raphy criteria for internal carotid stenosis
of more than 70% diameter: angiographic
correlation and receiver operating charac-
teristic curve analysis. Can Assoc Radiol J
1995; 46:291295.
13. Moneta GL, Edwards JM, Papanicolaou G,
et al. Screening for asymptomatic inter-
nal carotid artery stenosis: duplex criteria
for discriminating 60% to 99% stenosis. J
Vasc Surg 1995; 21:989994.
14. Neale ML, Chambers JL, Kelly AT, et al.
Reappraisal of duplex criteria to assess sig-
nicant carotid stenosis with special refer-
ence to reports from the North American
Symptomatic Carotid Endarterectomy Trial
and the European Carotid Surgery Trial. J
Vasc Surg 1994; 20:642649.
15. Moneta GL, Edwards JM, Chitwood RW,
et al. Correlation of North American
Symptomatic Carotid Endarterectomy
Trial (NASCET) angiographic denition
of 70% to 99% internal carotid artery ste-
Volume 229
Number 2 Society of Radiologists in Ultrasound Consensus Conference
345
R
adiology
Page 6
nosis with duplex scanning. J Vasc Surg
1993; 17:152159.
16. Umemura A, Yamada K. B-mode ow im-
aging of the carotid artery. Stroke 2001;
32:20552057.
17. Perkins JM, Galland RB, Simmons MJ,
Magee TR. Carotid duplex imaging: vari-
ation and validation. Br J Surg 2000; 87:
320322.
18. Grant EG, Duerinckx AJ, El Saden SM, et
al. Ability to use duplex US to quantify
internal carotid arterial stenoses: fact or
ction? Radiology 2000; 214:247252.
19. Beebe HG, Salles-Cunha SX, Scissons RP,
et al. Carotid arterial ultrasound scan im-
aging: A direct approach to stenosis mea-
surement. J Vasc Surg 1999; 29:838 844.
20. Soulez G, Therasse E, Robillard P, et al.
The value of internal carotid systolic ve-
locity ratio for assessing carotid artery ste-
nosis with Doppler sonography. AJR Am J
Roentgenol 1999; 172:207212.
21. Ranke C, Creutzig A, Becker H, Trappe HJ.
Standardization of carotid ultrasound: a
hemodynamic method to normalize for
interindividual and interequipment vari-
ability. Stroke 1999; 30:402406.
22. Derdeyn CP, Powers WJ. Cost-effective-
ness of screening for asymptomatic ca-
rotid artery disease. Stroke 1996; 27:
19441950.
23. Griewig B, Morgenstern C, Driesner F, Kall-
wellis G, Walker ML, Kessler C. Cerebrovas-
cular disease assessed by color-ow and
power Doppler ultrasonography: compari-
son with digital subtraction angiography in
internal carotid artery stenosis. Stroke
1996; 27:95100.
24. Srinivasan J, Mayberg MR, Weiss DG, Esk-
ridge J. Duplex accuracy compared with
angiography in the Veterans Affairs Co-
operative Studies Trial for Symptomatic
Carotid Stenosis. Neurosurgery 1995; 36:
648653.
25. Hunink MG, Polak JF, Barlan MM,
OLeary DH. Detection and quantica-
tion of carotid artery stenosis: efcacy of
various Doppler velocity parameters. AJR
Am J Roentgenol 1993; 160:619625.
26. Bluth EI, Stavros AT, Marich KW, Aufrich-
tig D, Baker JD. Carotid duplex sonogra-
phy: a multicenter recommendation for
standardized imaging and Doppler crite-
ria. RadioGraphics 1988; 8:487506.
27. Brown PB, Zwiebel WJ, Call GK. Degree of
cervical carotid artery stenosis and hemi-
spheric stroke: duplex US ndings. Radi-
ology 1989; 170:541543.
28. Carroll BA. Duplex sonography in pa-
tients with hemispheric symptoms. J Ul-
trasound Med 1989; 8:535540.
29. de Virgilio C, Toosie K, Arnell T, et al.
Asymptomatic carotid artery stenosis
screening in patients with lower extrem-
ity atherosclerosis: a prospective study.
Ann Vasc Surg 1997; 11:374377.
30. Alexandrov AV, Brodie DS, McLean A,
Hamilton P, Murphy J, Burns PN. Corre-
lation of peak systolic velocity and angio-
graphic measurement of carotid stenosis
revisited. Stroke 1997; 28:339342.
31. Fillinger MF, Baker RJ Jr, Zwolak RM, et al.
Carotid duplex criteria for a 60% or
greater angiographic stenosis: variation
according to equipment. J Vasc Surg
1996; 24:856864.
32. Howard G, Baker WH, Chambless LE,
Howard VJ, Jones AM, Toole JF. An ap-
proach for the use of Doppler ultrasound
as a screening tool for hemodynamically
signicant stenosis (despite heterogene-
ity of Doppler performance): a multi-
center experienceAsymptomatic Ca-
rotid Atherosclerosis Study Investigators.
Stroke 1996; 27:19511957.
33. Kuntz KM, Polak JF, Whittemore AD,
Skillman JJ, Kent KC. Duplex ultrasound
criteria for the identication of carotid
stenosis should be laboratory specic.
Stroke 1997; 28:597602.
34. Zweibel WJ, Austin CW, Sackett JF,
Strother CM. Correlation of high-resolu-
tion, B-mode, and continuous-wave
Doppler sonography with arteriography
in the diagnosis of carotid stenosis. Radi-
ology 1983; 149:523532.
35. El-Saden SM, Grant EG, Hathout GM,
Zimmerman PT, Cohen SN, Baker JD. Im-
aging of the internal carotid artery: the
dilemma of total versus near total occlu-
sion. Radiology 2001; 221:301308.
36. Pan XM, Saloner D, Reilly LM, et al. Assess-
ment of carotid artery stenosis by ultra-
sonography, conventional angiography,
and magnetic resonance angiography: cor-
relation with ex vivo measurement of
plaque stenosis. J Vasc Surg 1995; 21:82
88.
37. Johnston DC, Eastwood JD, Nguyen T,
Goldstein LB. Contrast-enhanced mag-
netic resonance angiography of carotid
arteries: utility in routine clinical prac-
tice. Stroke 2002; 33:28342838.
38. Ozaki CK, Irwin PB, Flynn TC, Huber TS,
Seeger JM. Surgical decision making for
carotid endarterectomy and contempo-
rary magnetic resonance angiography.
Am J Surg 1999; 178:182184.
39. Marcus CD, Ladam-Marcus VJ, Bigot JL,
Clement C, Baehrel B, Menanteau BP. Ca-
rotid arterial stenosis: evaluation at CT
angiography with the volume-rendering
technique. Radiology 1999; 211:775780.
40. Fox AJ. How to measure carotid stenosis.
Radiology 1993; 186:316318.
346
Radiology
November 2003 Grant et al
R
adiology
Page 7
  • Source
    • "on two large population studies [35, 36] and intima-media thicknesses over 0, and 81 mm was considered as IMT. Any thickening above 1.5 mm with narrowing of lumen above 50 % or 0.5 mm was classified as plaque3435363738. "
    [Show abstract] [Hide abstract] ABSTRACT: Introduction: Intima-media thickening (IMT), which is the early finding of carotid artery atherosclerosis, has been shown to be associated with obstructive sleep apnea syndrome (OSAS). In our study, we aimed to assess prospectively the effect of severity of OSAS and snoring on carotid artery IMT. Methods: A total of 102 patients who were admitted to sleep laboratory between May 2011 and May 2012 were included in the study. All patients were examined by polysomnography. Common carotid arteries (CCA) and internal carotid arteries (ICA) were evaluated for IMT by carotid Doppler ultrasonography. Results: The mean age was 45.9 ± 11.1, with 40 (39.2 %) women and 62 (60.8 %) men. Of 88 OSAS patients who had an apnea-hypopnea index (AHI) of >5, 33 (37.5 %) had mild, 20 (22.7 %) had moderate, and 35 (39.8 %) had severe disease. Fourteen patients who had AHI <5 were designated as the habitual snoring group. IMT was detected in 17 (16.7 %) of all patients. In patients with severe OSAS, CCA walls were thicker (p = 0.040) and IMT ratios were higher (p = 0.019) compared to mild/moderate OSAS patients. In patients with IMT, age, AHI, oxygen desaturation index (ODI), and snoring index were higher compared to patients without IMT (p < 0.05). Conclusion: Carotid artery IMT, which is an early finding of atherosclerosis, was found to be highly correlated with OSAS and snoring severity.
    Full-text · Article · May 2014 · Sleep And Breathing
  • Source
    • "The same calculations were carried out for all the cardiac cycles observed on the arterial diameter variation waveforms and averages were taken. Normalized and un-normalized plaque GSM and surface irregularity indices (SII) were obtained using previously described methods [8,10] while the degree of stenosis of the corresponding arteries were measured using criteria consistent with the NASCET method utilizing blood flow velocities in conjunction with the B-Mode and colour flow imaging303132. "
    [Show abstract] [Hide abstract] ABSTRACT: Systolic dilation of the atherosclerotic carotid artery depends on several factors including arterial compliance and the haemodynamic environment. The purpose of this study was to quantify wall motion in stenotic carotid arteries and investigate any associations with the ultrasound greyscale plaque characteristics, the degree of stenosis, and the presence of cerebrovascular symptoms. Variations in the lumen diameters of 61 stenotic carotid arteries (stenosis range 10%-95%) from 47 patients were measured before the proximal shoulder of the atherosclerotic plaque using ultrasound image sequences over several cardiac cycles. Absolute and percentage diameter changes from diastole to systole were calculated and their relationship to the degree of stenosis, greyscale plaque characteristics, and the presence of ipsilateral hemispheric symptoms were studied. The mean absolute diameter change from diastole to systole was 0.45 mm (s.d. 0.17), and the mean percentage diameter change was 6.9% (s.d. 3.1%). Absolute and percentage diameter changes did not have a statistically significant relationship to the degree of stenosis, greyscale plaque characteristics, or the presence of ipsilateral hemispheric symptoms (p > 0.05). Parameters significantly correlated with the presence of symptoms were the degree of stenosis (p = 0.01), plaque greyscale median (p = 0.02) and the plaque surface irregularity index (p = 0.02). Our study confirmed the degree of stenosis, plaque greyscale median and our surface irregularity index were significant predictors of symptoms, but found no significant correlation between diameter changes of stenosed carotid arteries and the presence of ipsilateral hemispheric symptoms.
    Full-text · Article · Oct 2013 · Cardiovascular Ultrasound
  • Source
    • "The image sequences used were of up to 10 seconds in length (average 4.4 seconds) and were acquired with a mean frame rate of 32 frames per second. The degrees of stenosis of the corresponding arteries were measured using criteria consistent with the NASCET methodology utilizing blood flow velocities in conjunction with the B-Mode and colour flow imaging [2,13,14]. Eleven of the plaques studied were found to be asymptomatic and the remaining sixteen symptomatic after assessment at the University Hospitals of Leicester NHS Trust's Rapid Access Transient Ischemic Attack (TIA) Clinic. The use of the clinical data for our research had been approved by the National Research Ethics Service (NRES) Committee East Midlands - Northampton (reference 11/EM/0249), and each patient gave informed consent before participating in the study. "
    [Show abstract] [Hide abstract] ABSTRACT: Background Several studies have found that the ultrasound greyscale median (GSM) of carotid artery plaques may be useful for predicting the risk of cerebrovascular events. However, measurements of GSM are typically performed on still ultrasound images ignoring any variations that may be observed on a frame-by-frame basis. The aim of this study was to establish the existence and investigate the nature and extent of these variations. Methods Employing a novel method that enabled plaque boundaries to be tracked semi-automatically, variations in the plaque GSM and observed cross-sectional area were measured for 27 carotid artery plaques (19 consecutive patients, stenosis range 10%-80%) over image sequences of up to 10 seconds in length acquired with a mean frame rate of 32 frames per second. Results Our results showed a mean inter-frame coefficient of variation (CV) of 5.2% (s.d. 2.5%) for GSM and 4.2% (s.d. 2.9%) for the plaque area. Thirteen of the 27 plaques (48%) exhibited CV in GSM greater than 5% whereas only six plaques (22%) had CV in plaque area of greater than 5%. There was no significant correlation between the CV of GSM and plaque area. Conclusions Inter-frame variations in the plaque GSM such as those found in this study have implications on the reproducibility of GSM measurements and their clinical utility. Studies assessing the GSM of carotid artery plaques should consider these variations.
    Full-text · Article · Jun 2013 · Cardiovascular Ultrasound
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