Imaging the Carotid
Bifurcation: Toward Standardization
Michael R. Jaff, DO
Treatment of extracranial carotid artery disease has been one of the most hotly debated
topics in vascular medicine. Imaging of the carotid bifurcation remains an important ﬁrst
step in the therapeutic decision-making process. Successful determination of the severity
of carotid artery stenosis depends on several factors, including the skill and expertise of the
technologists obtaining the images and the physicians providing an interpretation of the
data; knowledge of the advantages and pitfalls of the speciﬁc technology; and the need for
correlative imaging based on initial test ﬁndings. This article will highlight the current
strategies for carotid bifurcation imaging and will provide a diagnostic algorithm useful for
centers involved in the management of carotid artery disease.
Semin Vasc Surg 21:73-79 © 2008 Elsevier Inc. All rights reserved.
AROTID DUPLEX ULTRASONOGRAPHY (CDUS) is
the standard of care for the initial diagnosis of carotid
artery bifurcation disease. Not only does signiﬁcant internal
carotid artery stenosis increase the risk for both transient and
permanent neurologic events,
but also represents an in-
creased risk for coronary atherosclerosis, myocardial infarc-
tion, and cardiovascular death.
The physics of sound, based
on the Doppler equation, use the variables of the velocity of
sound in tissue, the difference between the frequency of
transmitted and reﬂected sound, and the cosine of the angle
of the ultrasonography beam to the direction of ﬂowing
blood, to determine the velocity of blood in vessels. This is
the basis for all vascular ultrasonography, and allows modern
ultrasonography to quantify degrees of carotid artery stenosis
based on the velocity of blood in various segments of vessels.
Initial Doppler criteria proposed by Fel and colleagues
utilized frequency measurements of the spectral waveform to
predict internal carotid artery stenosis.
nate criteria were developed that have resulted in excellent
sensitivity and speciﬁcity of duplex ultrasonography to de-
termine high-grade stenosis
(Table 1). Meta-analyses of
published criteria for carotid duplex ultrasonography have
demonstrated sensitivities of 98% and speciﬁcities of 88% for
detecting Ն50% internal carotid artery stenosis; and 94%
and 90%, respectively, for detecting Ն70% internal carotid
artery stenosis (Fig 1).
Many centers have proposed speciﬁc
diagnostic criteria, and this variability prompted a multispe-
cialty consensus conference that determined optimal criteria
based on a review of the published literature
The carotid duplex examination identiﬁes plaque, steno-
sis, and occlusion in the common, internal, and external
carotid arteries. The exam also identiﬁes the direction of ﬂow
in the vertebral arteries. This examination is routinely per-
formed for patients with a history of transient ischemic at-
tacks or stroke, after surgical or endovascular revasculariza-
tion, and in patients deemed to be at high risk for presence of
carotid stenosis. The most common indication for CDUS is
the ﬁnding on physical examination of a cervical bruit. Cer-
vical bruits result from several causes, including carotid
artery stenosis, transmitted cardiac murmur, thyrotoxico-
sis, arteriovenous ﬁstulae, and venous hums. Estimates of
the prevalence of asymptomatic carotid bruits in adults range
to 2.3 % in patients aged 45 to 54 years and 8.2% in
patients 75 years of age or older.
However, in a selected series of
patients scheduled to undergo vascular surgical procedures, the
incidence of cervical bruits ranged from 6%
mean prevalence of 10%.
Risk of developing a carotid bruit in
patients older than age 65 is approximately 1% per year, nearly
twice the rate found in patients aged 45 to 54 years.
There are speciﬁc components of carotid duplex ultra-
sonography that are critical to test accuracy. These include:
1. Waveforms obtained from a long axis view of the artery,
using a small sample volume placed in the center stream
of ﬂow or center to the ﬂow “jet”;
2. Alignment of the cursor parallel to the vessel wall;
3. Standardization of the Doppler angle to be 60 degrees
or less. A correct Doppler angle is required to calculate
Harvard Medical School and Vascular Center, Massachusetts General Hos-
pital, Boston, MA.
Address reprint requests to Michael R. Jaff, Harvard Medical School and
Vascular Center, Massachusetts General Hospital, 55 Fruit Street, Gray-
Bigelow 832, Boston, MA 02114. E-mail: email@example.com
0895-7967/08/$-see front matter © 2008 Elsevier Inc. All rights reserved.