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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5770_Библиотеки_им_академика_М_И_Перельмана.pdf
208
H. J. Welkoborsky
a
Fig. 10.4 B-scan sonography in axial (a; b, left) and longitudinal (b,
right) sections of the caudal parts of the neck. In the median parts of the
neck, landmarks include the sternocleidomastoid muscle (SCM) and
the common carotid artery (acc), with the carotid artery bifurcation (b,
left). In the cranial parts of the neck can be seen the sternocleidomastoid
This is easier in tall and slim patients. The vessel’s patency,
ow direction, and ow velocity are recorded (Fig.10.8).
Both the common carotid artery (CCA) and the internal
carotid artery (ICA) are low-resistance vessels; both have a
signicant diastolic ow, but it is greater in the ICA. In contrast, the external carotid artery (ECA) is a high-resistance
b
and digastric muscles and the external carotid artery (ECA) and internal
carotid artery (ICA). Note that the external carotid artery is smaller than
the internal carotid artery and has some branches. In this area, some
lymph nodes (lk) typically occur. SD thyroid gland, IJV internal jugular
vein
vessel that exhibits almost no diastolic ow, so the Doppler
spectrum of these vessels has signicant morphologic and
sound differences. The blood ow velocity in the CCA is
about 45–60cm/s, in the ECA 60–90 cm/s, and in the ICA
55–90cm/s (Fig.10.9; Video 10.3). Peak systolic velocities
of more than 100cm/s must be considered pathologic [1–3].
10 Sonography oftheLarge Neck Vessels andofTumors withSuspected Inltration oftheLarge Neck Vessels
Fig. 10.5 Color-coded
duplex sonography of the
internal carotid artery, carotid
artery bifurcation, and
ICA.Note that red color
means bloodstream toward
the transducer, whereas blue
color means bloodstream
away from the transducer.
Yellow or orange can signify
some turbulence. (a) vert
vertebral artery, acc common
carotid artery, ECA external
carotid artery, ICA internal
carotid artery, bulb carotid
artery bulb, wk. vertebral
bodies
aci
209
Fig. 10.6 High-resolution
section of the common carotid
artery (acc), in which the
tissue layers (intima,
muscularis, adventitia) can be
identied. IJV, internal
jugular vein; Wandung, vessel
wall
The vertebral artery is also a low-resistance vessel in which
the Doppler waveform resembles that of the ICA.However,
normal peak systolic velocities in the vertebral artery are
lower than in the ICA and are more variable than in the CCA
or ICA.They normally range between 20 and 40cm/s, and
peak systolic velocities below 10–20cm/s are considered to
be abnormal [1]. Peak systolic velocities exceeding 40cm/s
might be due to an occlusion or stenosis of the contralateral
vertebral artery; velocities may be normal in the dominant
vertebral artery in cases of signicant asymmetries of these
arteries.
For accurate examination of the carotid artery, ow
velocities are to be measured in the proximal, middle, and
distal (just proximal to the carotid artery bifurcation) parts
of the CCA; in the proximal, middle, and distal parts of the
ICA; and in the proximal part of the ECA.The following
hemodynamic parameters are derived from the single measurements and used for interpretation: peak systolic velocity
210
Fig. 10.7 (a) The internal
jugular vein (IJV) has a
triangular shape in axial
sections and a band-like shape
in transverse section. Here the
vessel is located anterior to
the carotid (acc). Note that the
vagal nerve appears as a
small, round, hypoechoic
structure between the carotid
artery and the jugular vein.
The vein is compressed by the
ultrasound transducer. (b)
Following a Valsalva
maneuver, the internal jugular
vein “blows up” and gets a
roundish shape in axial
sections. This maneuver is
suitable for purposes of
orientation or in cases in
which an inltration of the
vein is suspected
H. J. Welkoborsky
a
(PSV), end-diastolic velocity (EDV), mean ow velocity
(MFV), peak systolic and end-diastolic ICA/CCA velocity
ratios, resistance index (dened as (PSV-EDV)/PSV), pulsatility index (dened as (PSV-EDV)/MFV) and spectral
characteristic [4–6].
b
To estimate tumor perfusion, the ultrasound machine must
be able to detect slow blood ow velocities. The mass is
visualized in conventional B-mode, and the vessels supplying
the tumor with blood are detected by color-coded C-mode.
Peak systolic velocities are variable (Table 10.1); those of
10 Sonography oftheLarge Neck Vessels andofTumors withSuspected Inltration oftheLarge Neck Vessels
211
Fig. 10.8 Color duplex sonography of a right vertebral artery in a
healthy person. The vessel is identied in the intravertebral segments.
Patency and blood ow are recorded (Courtesy of Dr. Silke
Hörnschemeyer-Decker, Dept. of Neurology, Nordstadt Clinic,
Hannover, Germany)
Fig. 10.9 Doppler spectrum of the common carotid artery (a, b) inter-
nal carotid artery (c) and external carotid artery (d). (Figures 10.9 a-c:
Courtesy of Dr. Silke Hörnschemeyer-Decker, Dept. of Neurology,
Nordstadt Clinic, Hannover, Germany). Note that the external carotid
a
artery is a high-resistance vessel with a very low end- diastolic ow,
whereas the internal carotid artery is a low-resistance vessel with a
higher end-diastolic ow. The Doppler spectrum of the common carotid
artery comprises both
212
H. J. Welkoborsky
Fig. 10.9 (continued)
b
10 Sonography oftheLarge Neck Vessels andofTumors withSuspected Inltration oftheLarge Neck Vessels
c
213
Fig. 10.9 (continued)
d
214
H. J. Welkoborsky
Table 10.1 Normal peak systolic blood ow velocities in different
extracranial vessels and vessels for blood supply of cervical masses
Vessel Peak systolic velocity (PSV)
Common carotid artery (CCA) 45–60cm/s
Internal carotid artery (ICA) 55–90cm/s
External carotid artery (ECA) 60–90cm/s
Vertebral artery 20–40cm/s
Tumor vessels Variable; 2.5–10–30cm/s
Fig. 10.10 Visualization of small vessels supplying a neck mass with
blood. The vascularization comes from the periphery into the mass. By
Doppler sonography, peak systolic velocities of 2.5–5 cm/s in these
small vessels can be estimated
2.5–10cm/s can also be observed in the small tumor vessels
as velocities exceeding 20cm/s (Fig.10.10; Video 10.4).
10.4 Indications forUltrasound Imaging
oftheLarge Neck Vessels
Basically the indications for ultrasound examinations of the
extracranial vessels and vertebral arteries, according to the
latest advice from the American Institute of Ultrasound in
Medicine (AIUM) and the society of radiologists in ultrasound (SRU) [7], can be divided into neurological and nonneurological indications:
• Neurological indications
– Hemispheric neurologic symptoms, such as stroke,
transient ischemic attacks, and amaurosis fugax
– Unexplained or non-hemispheric neurologic
symptoms
– Cervical bruit
• Non-neurologic indications
– Diseases of the large vessels themselves
• Suspected carotid artery dissection or
pseudoaneurysms
• Suspected arteriovenous malformations (arteriovenous shunts)
• Atherosclerotic plaques and suspected carotid
artery stenosis
• Follow-up in patients with proven carotid artery
disease
• Suspected subclavian steal syndrome
• Follow-up after cerebrovascular revascularization,
carotid endarterectomy, carotid stenting, or carotidto- subclavian bypass
– Other indications
• Pulsatile neck masses
• Preoperative examination before major cardiovascular surgery
• Intraoperative monitoring of vascular surgery
• Large neck masses with suspected vessel
inltration
• Estimation of the perfusion of a given neck mass
The last two points are not advised by the AIUM and
SRU, but for head and neck surgeons, it is of great importance to determine the relation between a given tumor and
the large neck vessels and to estimate suspected tumor
inltration of the vessels, in order to decide whether the
tumor can be resected with little risk for the patient. As
many neck masses, such as lymph node metastases, reactive neck lymph nodes, and masses related to malignant
lymphoma, paraganglioma, and hemangioma, have a characteristic perfusion pattern, it is reasonable to conclude
that duplex and triplex examination of these lesions provides very important information that will inuence therapeutic strategy.
The following sections focus on the description of typical
sonographic ndings in diseases of the large vessels themselves and on ways to exclude inltration by examining the
relation between given tumors and the large vessels.
10.5 Diseases oftheLarge Neck Vessels
10.5.1 Carotid Artery Pathology
Carotid ultrasonography is the most useful imaging technique in the evaluation of patients with symptomatic and
asymptomatic carotid artery stenosis. Carotid sonography
provides data on the extent, site, and degree of stenosis,
according to the distribution of abnormal blood ow patterns within, proximal to, and distal to a narrowed arterial
segment. Carotid artery ultrasonography has been shown to
achieve a sensitivity of 92–100% and specicity of
93–100% to assess the degree of stenosis, which is comparable to or even better than other imaging techniques, such
as CT scans. Conventional angiography attains important
information about the diameter of the vessel, whereas ultrasonography provides important information on the length
10 Sonography oftheLarge Neck Vessels andofTumors withSuspected Inltration oftheLarge Neck Vessels
215
of the lesion and on blood ow; the two methods partially
correlate [8].
Magnetic resonance angiography (MRA) is reported to
achieve a higher overall accuracy of 70–99% for diagnosis of
a stenosis, compared with ultrasound, but the techniques are
comparable for detecting complete or incomplete carotid
artery occlusion. As ultrasonography provides additional
information about the vessel’s wall and morphology, some
authors conclude that the combination of ultrasound and
MRA seems most accurate in diagnosing carotid artery diseases [9]. Ultrasound examinations provide important information regarding the severity of stenosis, but the correlation
between its results and the results of conventional intraarterial angiography and CT angiography is uncertain in
many cases [10]. In a Cochrane meta-analysis, the threshold
of ultrasound-determined peak systolic velocity >130cm/s
showed a sensitivity of 98% and a specicity of 95% for
grading an ICA stenosis of >50% in angiography, and a peak
systolic velocity >200cm/s revealed a sensitivity of 90% and
a specicity of 94% in diagnosing an angiographic stenosis
>70% [11].
Several studies have been conducted to answer the
question whether the degree of carotid stenosis in asymptomatic patients predicts the risk for a transient ischemic
attack or a stroke. In general, the overall annual risk of a
stroke is about 3–4% in patients with asymptomatic stenosis of 80–99% and below 1% in patients with a stenosis
<80% [12].
Atherosclerotic plaques are the most common cause for
carotid artery stenosis. An atherosclerotic plaque is dened
as an area of a focal wall protrusion greater than 1.5mm or a
focal vessel wall thickening of more than 50% greater than
the surrounding wall thickness [1] (Fig.10.11). If an atherosclerotic plaque is present, the maximal carotid plaque thickness is determined by measurement in the highest plaque
prominence in any of the three carotid artery segments
assessed in multiangled images [1]. The plaque size, plaque
surface, and plaque composition can be determined by
B-mode sonography, and three additional morphologic
parameters can be evaluated:
• The intima-media thickness (IMT)
• The carotid plaque burden and total plaque area (TPA)
• The three-dimensional estimation of plaque volume
TPA and three-dimensional plaque volume are highly
correlated with the risk of cardiovascular disease and stroke.
Morphologically, several features are determined by a
combination of B-mode ultrasonography and duplex sonography [13]:
• Plaque size. It is measured in axial and longitudinal scans.
It correlates directly with the degree of stenosis and has
some impact as an independent predictor for future cere-
brovascular events and as a predictor for myocardial
infarction.
• Plaque ulceration and plaque surface irregularities. The
estimation of plaque surface irregularities is sometimes
challenging by B-mode sonography, but it has some pre-
dictive value for the stroke risk.
Fig. 10.11 Atherosclerotic
plaque in the ICA with a focal
wall protrusion >1.5mm and
a focal thickening more than
50% greater than the
surrounding wall thickness
216
H. J. Welkoborsky
• Plaque echogenicity. The basic difference is between
hyperechoic (echodense) and hypoechoic (echolucent)
plaques. Hyperechoic plaques contain more calcium and
are therefore calcied. In B-mode sonography, they are
seen as bright areas attached to the vessel’s lumen, with
acoustic shadowing (Fig. 10.12). Hypoechoic plaques
contain more lipid or blood. They are seen as masses that
are hypoechoic compared with the surrounding tissue,
and they lack acoustic shadowing (Fig.10.13). Several
studies revealed that hypoechoic, lipid-rich plaques are
associated with the risk of plaque progression and with
increased risk for future cerebrovascular events. In cases
of inammatory lesions, hypoechoic plaques also occur
with a smooth or slightly irregular surface [14]. Calcied
hyperechoic plaques may induce instability at the border
with soft tissues in the vessel’s wall, with a risk for plaque
rupture, but several investigations have shown that plaques
with a higher calcication percentage have a smaller
lipid-rich necrotic core, which probably decreases plaque
vulnerability [1].
• Distal turbulence intensity in the carotid bifurcation [13].
According to a meta-analysis and review of the literature
[15], there is some evidence that some plaque features,
including echolucency, neovascularization, ulceration,
and intraplaque motion, are associated with high risk for
ischemic symptoms, but the sensitivity and specicity of
sonography in detecting lipid-rich necrotic core, intra-
Fig. 10.12 Hyperechoic (echodense) plaque in the internal carotid
artery (ICA). The plaque contains calcium and appears as a bright area
attached to the vessel’s lumen. Note the acoustic shadowing behind the
plaque, a sign of calcication
Fig. 10.13 Hypodense (echolucent) plaque in the ICA.It displays as a hypoechoic mass attached to the vessel’s lumen. Longitudinal planes (left),
axial plane (top right), and Doppler spectrum (bottom right)
10 Sonography oftheLarge Neck Vessels andofTumors withSuspected Inltration oftheLarge Neck Vessels
217
plaque hemorrhage, and ulceration (predictors for risk
stratication) are limited, so additional MRI is recommended in some cases [16].
Carotid Intima-Media Thickness (IMT)
Much effort has been made in the past to investigate carotid
IMT and to elucidate its potential impact on atherosclerosis
and vascular events. The IMT measurements are performed
in longitudinal (transverse) scans (Fig.10.14), with measurements performed at the following standardized carotid artery
segments [1]:
• The near and the far wall of the carotid segment from
10mm to 20 mm proximal to the tip of the ow divider
into the CCA
• The near and the far wall of the carotid artery bifurcation,
beginning at the tip of the ow divider and extending
10mm proximal to the ow divider tip
• The near and the far wall of the proximal 10mm of the ICA
It is important to note that the IMT is measured out of
plaque areas. A total carotid IMT is calculated as a composite measure (the mean of the twelve sites described above).
Although several studies have established a clear association
between IMT, plaque size, and vascular events and between
a decrease of IMT inuenced by the intake of medications
and a decrease of risk for vascular events, normal values for
IMT in different populations and age groups are lacking, and
the importance of these ndings in regard to clinical practice
is still unclear. As a result, IMT and plaque measurement are
regarded only as useful tools in estimation of risks of vascular events in patients with risk factors. An increased CCA
wall thickness especially might be associated with rapid progression of carotid stenosis [17]. It is considered that the
advantage of B-mode ultrasonography lies in its costeffectiveness and lack of patient inconvenience, so that it can
be applied for risk assessment and monitoring of drug
therapy [1, 18].
Carotid Artery Stenosis
There are three basic pathogenetic mechanisms for cerebral
ischemia caused by a carotid artery stenosis due to atherosclerotic plaques: (1) embolization, in which parts of the plaque
ow from the carotid artery into the intracerebral vessels; (2)
thrombosis of the carotid artery due to plaque and propagation
of thrombosis to the intracerebral vessels; and (3) downregulation of cerebral perfusion due to blood ow impairment.
B-mode and color Doppler sonography is used to estimate
carotid artery stenosis, but blood ow velocities and other criteria used for diagnostic purposes and estimation of the degree
of stenosis vary signicantly between different laboratories
and different studies. These differences may be due to differences in the study population, the sonographer’s expertise, the
variability of vascular anatomy, and the ultrasound equipment
[4–6, 19, 20]. Much effort has been made to search for a perfect ultrasonic classication in assessing carotid artery stenosis. A multiparametric approach that has been implemented
includes as its criteria the maximal peak systolic velocity
(PSV), end-diastolic velocity, and the ICA- to- CCA ratio [4, 5,
21, 22]. According to the North American Symptomatic
Carotid Endarterectomy Trial (NASCET), a carotid stenosis is
dened as an occlusion of more than 20% of the vessel’s
lumen, and a signicant stenosis is dened as an occlusion of
more than 50% [23]. Doppler velocity criteria can successfully be applied for classifying the severity of an ICA stenosis.
On the other hand, the simplied greyscale/mosaic protocol
has a high negative predictive value for detection of carotid
artery stenosis with an occlusion of more than 50% [23]. The
correlation between the parameter “maximum peak systolic
velocity” and artery stenosis is moderate [23]. Additional criteria that could be used include the prestenotic ow in the
CCA and the extent of poststenotic disturbances (Video 10.5)
[5]. By using this multiparametric approach, the correlation
between sonography and conventional angiography in describing the degree of stenosis can be improved [5]. A meta-analysis of 19 publications revealed a signicant variability of these
Doppler velocity stenosis criteria, compared with conventional angiography in both native and stented ICAs [6].
Fig. 10.14 Sites for measuring the carotid
intima-media-thickness (IMT). (1) In a segment
of10–20mm proximal to the ow divider in the
CCA. (2) In the carotid artery bifurcation up to
10mm proximal to the ow divider. (3) The near
and the far wall in the proximal 10mm of the
ICA[1]
ECA
ICA
3
10 mm
10 mm210 mm
1
CCA
Intima
Media
Adventitia