From the Institute of Clinical Physiology, CNR, and Department of
Medicine (C.P., M.K., C.M.), and the Institute of Neurosurgery (G.P.),
University of Pisa; Esaote S.p.A., Florence (F.A., A.T., P.P.), Italy; and New
England Medical Center, Tufts University School of Medicine, Boston, Mass
(G.M., N.G.P.).
Correspondence to Carlo Palombo, MD, Institute of Clinical Physiology, CNR, via Savi 8, 56 126 Pisa, Italy. E-mail palombo{at}nsifc.ifc.pi.cnr.it
Methods—The quantitative analysis of focal
atherosclerotic lesions was validated in vitro on 27 phantoms of
fibroadipous plaques of known volume (range, 100 to 600
mm3). In vivo reproducibility of plaque volume measurement
was tested in 33 patients who had a total of 47 predominantly
fibroadipous carotid plaques. Distensibility assessment was validated
indirectly through the evaluation of age-related changes in
distensibility of common carotid artery in healthy and hypertensive
subjects (25 men in each group).
Results—The volume of plaque phantoms measured from the 3-D data
set showed a very close correlation with the true volume
(r=0.99; y=0.96x+12.38;
P<0.01), with the mean difference between the 2
measurements being -3.12±15.1 mm3. High
reproducibility was found for measurement of carotid plaque volume in
vivo: the mean difference between measurements from 2 observers for the
same data set was 0.60±11.2 mm3. Indexes of
arterial distensibility decreased with age in healthy
population, whereas this relationship was lost in hypertensive
subjects.
Conclusions—Ultrafast 3-D ultrasound imaging of carotid artery
demonstrates good accuracy and reproducibility for atherosclerotic
plaque volume measurements. The system also allows the study of
age-related degenerative vascular changes.
3-D vascular imaging can be expected to improve assessment of luminal
geometry and disease process, since a 3-D data set can be freely
rotated and examined along multiple planes and tomographic sections.
3-D vascular ultrasound may also contribute to assessment of the
progression of atherosclerosis and age-related
degenerative vascular changes through plaque volume quantification and
evaluation of regional arterial distensibility.
This study was designed to address the following objectives: (1) to
develop a prototype of a 3-D ultrasound system for vascular imaging
capable of fast and simple acquisition and elaboration of data, (2) to
assess the accuracy of the 3-D system for quantitative measurements in
an in vitro phantom model of atherosclerosis, and (3)
to assess the clinical applicability of the system in the evaluation of
carotid artery morphology and distensibility.
In our system, a controlled sequential tomographic data acquisition is
performed by scanning in a fanlike motion. Linear array of the
high-frequency transducer (7.5/10 MHz) sweeps over an arc up to 65°
in programmable steps. In each step, which can be as narrow as 1°, a
2-D vascular image is acquired. During acquisition, the long axis of
the probe is aligned with the long axis of the vessel (Figure 1
Image acquisition can be either asynchronous or synchronous with ECG.
Asynchronous acquisition takes about 2 seconds, since it depends only
on frame rate and velocity of the stepper motor of the probe (<10 ms
per step). Acquisition synchronous with ECG is an acquisition of
sequences of 2-D images temporally located in the cardiac cycle at
different angular positions of the probe. The number of images captured
in 1 cardiac cycle depends on heart rate and frame rate and varies from
16 to 8, with heart rate varying from 55 to 100 bpm. The time required
for synchronous acquisition is about 1 minute because it depends on
heart rate and the angle of acquisition. The sequential tomographic 2-D
images are stored in a digital format using a small pixel matrix of
512x512 and 8-bit gray scale to preserve high image definition. During
image processing, which is immediate, a realignment of 2-D images
according to their position in space and in the cardiac cycle is
performed, and volume data set information is calculated.
The 3-D data set is reconstructed with a reference system relative to
the alignment of the probe. When a section through the volume data is
chosen, coordinates are transformed to generate the reference system
relative to the selected section. Any desired section independent of
the position of the probe during data acquisition ("any plane"
sectioning), as well as a number of parallel and equidistant cross
sections in selected vessel segments ("paraplane" sectioning), can
be computed and reconstructed by a digital processing board in nearly
real time.10 Interpolation is used to fill the
gaps between tomographic sections.
Data are displayed as a 3-D data set, which can be freely rotated along
3 orthogonal axes, and 2-D tomographic sections, which can be obtained
along longitudinal, transverse, and oblique planes (Figure 2
Quantitative Analysis
In Vitro Study
Clinical Study
The performance of the 3-D prototype for arterial
distensibility assessment was tested in 25 healthy control subjects
(all men; mean age, 42.8±18.4 years) and in 25 hypertensive subjects
(all men; mean age, 59.1±13.6 years; P<0.05 versus
control) without regional atherosclerotic changes in carotid vessels.
At the time of the study, blood pressure in hypertensive subjects was
controlled by ß-blocker therapy, since our goal was to compare the 2
groups at the same level of distending
pressure.16 In all subjects, the right common
carotid artery was studied at 2 different segments, the first 1 cm and
the second 3 cm distal to flow divider. In both segments, a dynamic
sequence of transverse sections in 1 cardiac cycle was displayed, and
in each frame the luminal area was manually traced (Figure 3
Before the acquisition, all subjects were allowed to relax in the
supine position for at least 20 minutes, and 3-D acquisition was
performed when blood pressure, monitored at the site of brachial artery
(Dinamap 845-XT), was stable. Intraindividual variability of
measurements was assessed in 20 subjects, with an interval of at least
1 month between the readings of the same 3-D data set. Interindividual
variability was assessed in 12 subjects. In both populations studied,
the correlations of age with systolic blood pressure, pulse
pressure, intima-media thickness, diastolic cross-sectional
area, carotid strain, and pressure-strain elastic modulus were
evaluated.
Data Analysis
Intraobserver and interobserver agreement was good (for both,
r=0.99 and P<0.01) with a mean percent
difference of 3.5±2.9% and 5.8±4.7%, respectively. A plot of the
differences between the 2 observers in each volume measurement against
the mean of the 2 measurements showed a mean difference of
-0.81±15.2 mm3 (range, -18.7 to 33.7
mm3), with good agreement (all points but 3
within ±2 SD of the mean difference).
Clinical Study
Carotid plaque volume ranged from 7.4 to 435.1
mm3, with a mean value of 109.4±101.4
mm3, when measured by the first observer and from
7.7 to 449.0 mm3, with a mean value of
109.7±104.2 mm3, according to the second
observer. The correlation between the 2 observers was high
(r=0.99, y=1.02x-2.03;
P<0.01). Mean difference was 0.60±11.2
mm3 (range, -32.3 to 27.0
mm3) or 6.4±4.1%, respectively, with good
agreement, since all points but 4 were within ±2SD of the mean
difference.
Intraobserver agreement was high (r=0.99,
y=1.03x-1.89; P<0.01), with a mean
difference of -1.44±6.2 mm3 (range, -17.2
to 14.3 mm3) or 4.0±2.7%, respectively,
and good agreement between the 2 readings (all points but 4 were within
±2SD of the mean difference).
Agreement for plaque volume measured by the same observer in 2
different data sets (or acquisitions, respectively) was also good
(r=0.99; y=1.01x+0.47); mean
difference was 1.36±4.8 mm3 or 6.1±4.1%,
respectively.
Assessment of Arterial Distensibility
The values of carotid strain and pressure-strain elastic modulus, as
well as intima-media thickness, are reported in the Table
Intraindividual variability of measurements was 6.3±4.8% for carotid
strain and 6.4±4.6% for pressure-strain elastic modulus. The
correlation between the 2 measurements was good (r=0.96 and
r=0.97, P<0.01 for both), and the mean
difference was -0.17±1.31% (range, -3.4% to 2.6%) and 0.84±5.35
kPa (range, -6.79 to 15.59 kPa).
Interindividual variability was 9.6±8.0% for carotid strain and
9.8±8.5% for pressure-strain elastic modulus. Correlation between the
2 observers was r=0.94 and r=0.98
(P<0.01 for both). Mean difference was 1.06±1.91% (range,
-1.1% to 4.6%) and 0.65±7.99 kPa (range, -9.87 to 17.86 kPa), with
good agreement (all points but 1 within ±2SD of the mean
difference).
The ability to slice and reslice the acquired 3-D data set in any
desired plane and segment and to rotate the data set along 3 orthogonal
axes allows the assessment of luminal geometry and vascular pathology
from a single data acquisition (Figures 2
Carotid Atherosclerosis
Thus far, B-mode vascular ultrasound has presented
methodological difficulties for serial evaluation of the extent of
atherosclerosis, since the slight differences in probe
position in consecutive examinations of the same patient may influence
spatial definition of atherosclerotic plaque and hence its
quantification.6 23 Acquisition of an entire 3-D
data set containing information about spatial distribution of the
plaque should overcome this problem. In an in vitro validation on
plaque phantoms, very good accuracy and reproducibility of volume
measurements were achieved. The reproducibility of measurements also
was confirmed in the clinical study on carotid atherosclerotic
process.
Arterial Distensibility
Because no gold standard method exists for distensibility assessment,
we performed an indirect validation of the system by comparing the
mechanical properties of the common carotid artery and their
relationship with age in normotensive and hypertensive subjects.
Age and hypertension are reported to increase large-artery
stiffness.16 27 28 29 30 31
Our results are in agreement with previous
data.13 14 25 26 27 30 31 In healthy populations,
carotid intima-media thickness and cross section increased and indexes
of carotid distensibility worsened with advancing age. In hypertensive
populations, the relationship between age and morphological or
functional characteristics of the carotid artery was not
significant, since the correlation observed between age and
pressure-strain elastic modulus was probably related only to
age-dependent increase in pulse pressure. These findings suggest that
chronically elevated blood pressure accelerates the degenerative
process in arterial wall and modifies age-related changes
in large arteries.
Furthermore, regional carotid distensibility was significantly
decreased in hypertensive subjects compared with a healthy population,
and the difference between the 2 populations was much greater than the
reproducibility limits of the technique. However, looking at these
results, we must take into account the fact that elastic modulus can
change significantly with distending
pressure,32 33 and pulse pressure was still
significantly higher in hypertensive subjects compared with healthy men
despite pretreatment with ß-blockers.
Comparison With Other Diagnostic Systems
Echo-tracking systems were used recently for assessment of
arterial
distensibility.13 16 25 29 31 The advantages of
these systems are high temporal and spatial resolution. On the other
hand, they evaluate pulse pressure–dependent changes of the vessel in
1 dimension only, assuming isotropic behavior of the
arterial segment. This assumption is not completely met
because the vessel has a complex 3-D structure that can have different
pressure-strain relationships in different
directions.32 A dynamic 3-D system evaluating
changes in arterial luminal cross section may provide more
accurate information; however, its temporal resolution is lower because
it allows the acquisition of no more than 16 frames per cardiac
cycle.
System and Study Limitations
When a dynamic presentation of data volume is used, the
image acquisition should be synchronized with respiration. In
The implementation of an automated or semiautomated border detection
technique in the assessment of plaque volume and arterial
distensibility can be expected to reduce the time of analysis
and subjectivity of manual tracing and to provide a further advance in
collection of volumetric data for distensibility measurement.
In the present study, the feasibility of plaque volume measurement
was evaluated in minor predominantly fibroadipous plaques, since we
believe that assessment of the progression or regression of
atherosclerotic process can be studied in this type of atherosclerotic
alterations. Therefore, on the basis of our results, we cannot comment
on the accuracy of the system in quantification of severe and calcified
atherosclerotic changes.
Conclusion
However, further improvements are needed to increase the feasibility
and accuracy of the system, including automated border detection
technique, synchronization with respiratory wave, and superimposition
of the blood pressure curve on digitized vascular images.
Received January 16, 1998;
revision received April 7, 1998;
accepted May 14, 1998.
2.
Craven TE, Ryu J, Espeland MA, Kahl FR, McKinney WM,
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© 1998 American Heart Association, Inc.
Original Contributions
Ultrafast Three-Dimensional Ultrasound
Application to Carotid Artery Imaging
Abstract
Top
Abstract
Introduction
Methods
Results
Discussion
References
Background and
Purpose—Three-dimensional (3-D) vascular ultrasound can be
expected to improve qualitative evaluation of vessel pathology and to
provide quantitative data on vascular morphology and function. The
objective of this study was to develop an ultrafast 3-D vascular system
and to validate its performance for quantitation of
atherosclerosis and assessment of regional
arterial distensibility.
Key Words: ultrasonics • carotid arteries • atherosclerosis • imaging
Introduction
Top
Abstract
Introduction
Methods
Results
Discussion
References
Severity of
extracranial carotid atherosclerosis has been shown to
be not only a major cause of ischemic cerebral events but also
a reliable marker of systemic
atherosclerosis.1 2 3 Ultrasound
is increasingly used as the primary method for assessing the severity
of disease in carotid artery, since it represents a noninvasive
and inexpensive method, is easy to perform with adequate
reproducibility, and is capable of delineation of intraluminal
anatomy and assessment of the extent of the atherosclerotic
process.4 5 However, because the vessel and the
plaque it contains represent a complex 3-D structure, and since
plaque commonly develops asymmetrically, plaque severity and luminal
narrowing may be overestimated or underestimated with 2-D
imaging.6 Further improvement in the qualitative
and quantitative capabilities of ultrasound may be based on the 3-D
approach.7 8 9
Methods
Top
Abstract
Introduction
Methods
Results
Discussion
References
Description of the System
We developed a system for controlled acquisition of multiple
sequential tomographic 2-D images of the vessel and consequent
elaboration of acquired data. This system was integrated into
conventional US equipment (Esaote S.p.A., Florence, Italy) so that no
external or additional carriage motion device or image processing board
is required. 
). The movement of the 3-D transducer is
guided by a stepper motor built in inside the probe and controlled by
the ultrasound equipment; no external motion device is required. The
dimensions of the probe are comparable to those of the conventional
linear probe.
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Figure 1. Scheme of data acquisition with 3-D vascular
probe. See text for explanation. ). The presentation of the
3-D data set and 2-D sections is static for the acquisition
asynchronous with ECG and dynamic (cine-loop display) for the
acquisition synchronous with ECG. The latter type of acquisition allows
the frame-by-frame overview of a dynamic sequence of cross sections in
1 cardiac cycle, representing the
systo-diastolic expansion and contraction of the
vessel.
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Figure 2. Data display: 3-D data set (upper left quadrant),
longitudinal display of the vessel (upper right quadrant), and 2
reconstructed transverse sections (lower quadrants). Selected
transverse sections are indicated by 2 dotted lines. Top, Internal
carotid artery with several plaques. The luminal geometry of the plaque
can be seen in reconstructed transverse sections, where the external
carotid artery and its atherosclerotic changes are also evident, even
though the vessel is not displayed in 3-D data set and longitudinal
section. Rotation of the entire data set along the x
axis displays the external carotid artery in 3-D data set and long axis
(bottom). In the 3-D data set shown in the bottom panel, the internal
carotid artery is hidden behind the external; however, its
reconstructed cross sections are visualized in the lower
quadrants.
Volume measurement is performed through computer-guided direct
planimetry.11 12 The system automatically divides
the length of the measured vessel segment into N parallel and
equidistant slices. The thickness of slices is programmable and can be
as low as 0.5 mm. Each slice is displayed in the corresponding
transverse plane, where area (Ai) can be manually
traced. Final volume represents the sum of N cylinders of
different shape and equal height (H):
Dynamic presentation of the 3-D data set and any
selected transverse section allows frame-by-frame display of the
sequence of 2-D cross sections in 1 cardiac cycle (from 8 to 16 frames
depending on heart rate) and the evaluation of the luminal area in each
frame (Figure 3
). This feature can be
used to assess the changes in vessel area during 1 cardiac cycle (ie,
in relation to systo-diastolic changes in distending
pressure) so that indexes of arterial distensibility can be
calculated as follows13 14 : Carotid Strain
(%)=
Area/Aread, and Pressure-Strain Elastic
Modulus (kPa)=(p/Area)xAreaavg, where
Area indicates systo-diastolic difference in
arterial area; Aread, smallest
arterial area in cardiac cycle; p,
systo-diastolic difference in arterial
pressure; and Areaavg, average value of
arterial area throughout cardiac cycle.
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Figure 3. Two of 16 frames displaying changes in
arterial cross-sectional area during 1 cardiac cycle in a
selected segment of the vessel. Frame 1 (top) corresponds to the
minimum cross section (21.6 mm2), while frame 5
(bottom) represents maximum area (25.4
mm2).
Twenty-seven phantoms of fibroadipous plaque were prepared. They
consisted of pieces of bovine fibro-fatty tissue of known volume
(range, 100 to 600 mm3) measured by
Archimedes' principle. Phantoms were inserted into cylindrical tubes
(polyurethane) of known diameter (range, 4.5 to 8 mm; ie,
corresponding to the wide diameter range of extracranial carotid
vessels), and tubes were filled with saline. Each tube was placed into
a block of 1.2% agar-agar15 in such a way that
the distance of the tube from the superior surface of the agar block
was 1.5 cm and that from 1 of the lateral surfaces was 2.5 cm. 3-D
acquisition was performed twice, once with the probe placed on the
superior surface of the agar block and once with the probe placed on
its lateral surface; during both acquisitions, the long axis of the
probe was aligned with the long axis of the tube (Figure 4). Thus, 54 data sets were used for
validation. Intraindividual variability of measurement was assessed in
45 phantom volumes with an interval between the 2 readings of at least
1 month. Interindividual variability was tested in 32 phantom
volumes.
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Figure 4. Example of fibroadipous plaque phantom volume
measurement. Top, 3-D data set, longitudinal section, and 2 different
reconstructed transverse sections. Bottom, Direct planimetry of 1
parallel slice at the level of the yellow dotted line.
Interindividual and intraindividual variability of in vivo
carotid plaque volume measurement was assessed in 33 patients (21 men;
mean age, 65±14 years) who had a total of 47 plaques (range, 7 to
450 mm3) in either right or left common,
internal, or external carotid artery. Plaques were classified as minor
(lumen reduction 
50%) and predominantly fibroadipous (Figure 5). In the entire data set of 47 plaques,
repeated measurements were performed on the same 3-D data set; in 16
plaques (range, 12 to 237 mm3), repeated
measurements also were performed on 2 different data acquisitions.
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Figure 5. Example of plaque volume measurement in vivo. The
length of the plaque (indicated by 2 green dotted lines) was
electronically divided into 13 equidistant slices. Each slice was
displayed in transverse section, and plaque area was manually
traced. 
). The
intima-media thickness of the far wall of the common carotid artery was
measured at the same vascular level as area changes, but in
longitudinal display.17
Data are expressed as mean±1SD. For multiple comparisons, ANOVA
was used as appropriate; to assess statistical significance between
groups, Scheffé's t test was applied, with
P<0.05 considered significant. Regression analysis
was performed using a simple linear model. The agreement between 2
readings was evaluated by estimating the consistent bias
between readings, as recommended by Bland and
Altman18 for comparison of 2 methods of clinical
measurements. Statistical analysis was performed using
commercially available software (StatView SE+Graphics, Abacus Concepts
Inc).
Results
Top
Abstract
Introduction
Methods
Results
Discussion
References
In Vitro Study
In all phantoms, high-quality images were obtained (Figure 4). The
phantom volume ranged from 100 to 600 mm3,
with a mean value of 264.8±157.7 mm3 by
Archimedes' principle, and from 92.2 to 597.5
mm3, with a mean value of 267.5±152.6
mm3 by direct planimetry from 3-D data set. The
correlation between the 2 measurements was high (r=0.99,
y=0.96x+12.38; P<0.01). Mean
difference was -3.12±15.1 mm3 (range,
-29.1 to 28.0 mm3) or 6.9±6.7%,
respectively, with good agreement between the 2 measurements, since all
points but 2 were within ±2SD of the mean difference. No differences
in phantom volume were observed between 2 different acquisitions of the
same phantom (269.2±153.8 versus 265.8±154.2
mm3, P=0.45).
Plaque Volume Measurement
In all patients, good-quality 3-D images and tomographic sections
were obtained. The ability to scroll through the 3-D data set and to
stop at any desired segment facilitated the evaluation of the luminal
geometry (Figure 6). The rotation of the
entire data set along 3 orthogonal axes facilitated the visualization
of both internal and external carotid arteries independently of their
spatial relationship (Figure 2).
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Figure 6. Reconstructed transverse sections obtained at the
level of common carotid artery (top), carotid bulb (middle), and
internal carotid artery (bottom). Concentric fibroadipous plaque at the
level of the carotid bulb is responsible for lumen reduction of 35%,
while an eccentric plaque is evident within the internal carotid artery
in the transverse section only. Displayed transverse sections are
indicated by yellow dotted lines in each longitudinal view. Green
dotted lines indicate sections selected but not actually displayed in
the Figure.
Good-quality dynamic 3-D volume sets and 2-D tomographic sections
were obtained in 19 of 25 healthy control subjects and 19 of 25
hypertensive subjects; in 12 of 50 subjects (24%), the presence of
respiratory artifacts prevented the accurate measurement of vessel area
changes. Even during therapy, systolic pressure of hypertensive
subjects was still higher than that of control subjects, whereas no
difference was observed for diastolic pressure. As a
result, pulse pressure was higher in hypertensive subjects
(Table).
View this table:
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Table 1. Blood Pressure, Carotid Geometry, and Distensibility Indexes
in Healthy and Hypertensive Subjects . No
differences were observed between the 2 segments of right carotid
artery evaluated, whereas significant differences were found between
healthy control and hypertensive subjects. In healthy control subjects,
age correlated directly with systolic blood pressure
(r=0.52, P<0.05) but not with pulse pressure,
and with intima-media thickness (r=0.69,
P<0.01), diastolic carotid cross section
(r=0.48, P<0.05), and pressure-strain elastic
modulus (r=0.79, P<0.01), and it correlated
inversely with carotid strain (r=0.86, P<0.01).
In hypertensive subjects, age correlated directly with systolic
blood pressure (r=0.56, P<0.05), pulse pressure
(r=0.57, P<0.05), and pressure-strain elastic
modulus (r=0.50, P<0.05) but not with
intima-media thickness, carotid cross section, and carotid strain.
Discussion
Top
Abstract
Introduction
Methods
Results
Discussion
References
This study of a prototype of a 3-D vascular system demonstrates
that such a system (1) can be of clinical interest in patients with
carotid artery disease because it delineates the presence and extent of
carotid atherosclerosis, (2) yields reliable and
reproducible quantitative data, and (3) may be used for assessment of
regional arterial distensibility. and 6). In this way, the
distribution and shape of atherosclerotic lesions can be better
appreciated. In addition to its use in qualitative evaluation of the
disease process, a 3-D system allows the collection of quantitative
data on vascular morphology and function, thus offering a more
comprehensive insight into carotid artery disease.
An important clinical contribution of the 3-D vascular approach is
represented by the opportunity to study the progression and
regression of the atherosclerotic process. Quantitative
analysis of atherosclerotic plaque may provide information on
the natural history of atherosclerosis and the
effectiveness of lifestyle and pharmacological
interventions,19 20 21 22 potentially useful for
epidemiological and follow-up studies.
Assessment of arterial compliance or distensibility is
supposed to provide clinically relevant information on biological age,
early atherosclerotic changes, vascular changes associated with
systemic hypertension, and the effectiveness of lifestyle and drug
interventions.13 16 24 25 26 27 28 29 30 31 Compliance
represents the change in vessel volume per unit change in
pressure. Because the change in arterial long axis during
the cardiac cycle is minimal, the monitoring of arterial
cross section may be adequate for estimation of arterial
distensibility.
3-D reconstruction of the vessels and atherosclerotic plaques has
been attempted using other systems,7 8 19 20 34
some of which also applied volume-rendering methods to display vessels
and plaques in a 3-D perspective. These systems required external
carriage motion devices and image processing boards; consequently, data
acquisition and elaboration were much more demanding and
time-consuming. We suppose that the most important contribution of a
3-D approach for vascular diagnosis is the possibility of electronic
"any plane" and "paraplane" sectioning of the 3-D data set.
However, a volume-rendering algorithm can be easily applied to the data
set collected by our system, since all needed information is already
available.
The lateral resolution of the system is inferior to
axial resolution because the transverse focalization of the linear
array is controlled by the silicon lens only and thus is fixed, whereas
a longitudinal focalization is dynamically swept in electronic
way. 
25%
of subjects, appropriate dynamic images could not be obtained because
of respiratory artifacts. A significant improvement may be expected
from the superimposition of the arterial pressure curve
captured during dynamic 3-D acquisition.
A 3-D vascular approach capable of fast and easy volume data
acquisition and real-time interactive tomographic sectioning in any
desired plane, together with quantitative estimation of plaque volume
and arterial distensibility, allows better evaluation and
quantification of vascular morphology and function. Above all, this
approach may be promising for the study of the atherosclerotic process
in humans because it allows accurate quantitative assessment of
atherosclerotic lesions together with evaluation of regional
arterial distensibility. Changes in local distensibility of
the vessel are known to anticipate the development of macroscopic
lesions.35
References
Top
Abstract
Introduction
Methods
Results
Discussion
References
1.
Gomez CR. Carotid plaque morphology and risk for
stroke. Stroke. 1990;21:148–151.
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