Atherosclerosis: the evolving role of vascular image analysis
Computerized Medical Imaging and Graphics
Atherosclerosis: The evolving role of vascular image analysis
National Technical University of Athens, School of Electrical and Computer Engineering, Biomedical Simulations and Imaging (BIOSIM) Laboratory,
Iroon Polytechniou 9, Zografos 15780, Athens, Greece
Atherosclerosis, a chronic systemic degenerative disease involv-
hemorrhage, large lipid cores, and heterogeneous material distri-
ing the aorta, coronary, carotid, and peripheral arteries, has plagued
bution are among the candidate “suspects” for abrupt progression
mankind since the beginning of time. Surprisingly enough, it
of the disease and plaques prone to rupture. Plaque inﬂammation
has been recently proved that even Egyptian mummies, ancient
is also believed to be a main driver of clinical events
humans of high social status, had established atherosclerosis in
The aforementioned difﬁculties in current decision making for
atherosclerosis hold major risks for patient safety considering that
Although atherosclerotic lesions (plaques) may remain “silent”
atherosclerosis may not be detected at an early stage, vulnerable
for decades, they are considered the leading underlying cause of
plaques may not be identiﬁed, while patients with stable plaques
cardiovascular disease (CVD) which covers a wide range of fatal
may unnecessarily undergo a surgical procedure with potential
disorders related to the circulatory system, such as coronary heart
complications. Furthermore, due to the high cost of revascula-
disease (CHD) and stroke. Each year, CVD causes over 1.9 million
rization and bypass surgery already unbearable cost of
deaths in the European Union (EU); CHD by itself accounts for 15%
atherosclerosis is further increased; note that it has recently been
and 13% of all deaths among men and women, respectively, while
shown that unnecessary carotid revascularization procedures in
around one in every twelve men (8%) and one in ten women (11%)
asymptomatic patients in the US cost health-care providers US$2
die from stroke same report highlights that CVD costs EU
some D 196 billion a year due to healthcare costs (54%), productivity
With atherosclerosis being a major cause of morbidity and mor-
losses (24%) and spending on informal care (22%). Similar statistics
tality, as well as an economic burden worldwide, it is obvious that
have also been reported for the United States (US) causes
early detection and valid risk stratiﬁcation for the disease consti-
approximately 1.3 million deaths each year in the US, with CHD
tute a crucial public health challenge. In recent decades, advances
and stroke accounting for 17% and 6% of all deaths, respectively.
in medical imaging technology and computer vision have allowed
The annual direct and indirect ﬁnancial cost of CVD in the US is
for valuable contribution of image analysis toward this direction. By
estimated $297.7 billion due to healthcare expenditures (60%) and
continuously revealing several new morphological or composition-
related markers, vascular image analysis plays a multifaceted role
In current clinical practice, atherosclerotic patients are offered
which focuses on accurately detecting the presence of atheroscle-
either an invasive procedure, such as artery revascularization
rosis in individuals, deﬁning the burden of the disease before they
(endarterectomy or angioplasty with stenting) and bypass surgery,
develop clinical events, and evaluating the efﬁcacy of therapies.
or a more conservative therapy with medications, physical exercise
Computed tomography (CT) of the chest, in particular, has pro-
and dietary therapeutic decision is traditionally made judg-
vided a real breakthrough in the evaluation of coronary artery
ing on symptom status and the image-measured degree of artery
calciﬁcation (CAC) used for detecting the presence of atheroscle-
stenosis, which, however, is not always sufﬁcient Speciﬁ-
rosis in the artery. Furthermore, CAC score has been shown to be
cally, it has been observed that severe carotid artery stenosis may
able to assess cardiovascular risk, adding prognostic information
remain asymptomatic carotid atherosclerotic plaques
to the Framingham risk score CT image analy-
causing a low degree of stenosis can result in symptoms
sis has also shown great potential in detecting signiﬁcant coronary
nary atherosclerotic plaques being less than 50% occlusive have
artery stenoses identifying the composition of plaques
also been reported to cause acute coronary and cerebrovascular
and assessing the response to anti-inﬂammatory drugs
syndromes observations arise from the fact that plaque’s
Similar ﬁndings have been reported regarding the role of mag-
material (calcium, ﬁbers, blood components, lipids, etc.) composi-
netic resonance imaging (MRI) in optimal management of the
tion appears to be a critical determinant of the risk for future events
disease. Besides the ability of MRI image analysis to clearly identify
the absence of calciﬁcation, thin ﬁbrous caps, intra-plaque
vessel boundaries, thereby allowing highly accurate measurements
of plaque burden histological studies have shown that it
also offers a comprehensive structural plaque characterization
More interestingly, experiments have associated the iden-
tiﬁcation of a ruptured ﬁbrous cap in MRI images with a recent
K.S. Nikita / Computerized Medical Imaging and Graphics 37 (2013) 1–3
history of ischemic event MRI image analysis of
would offer optimal data management, knowledge discovery and
atherosclerosis can also provide useful information about the effect
sharing, as well as easy comparisons with similar prior cases for
Nuclear imaging modalities, i.e. positron emission tomogra-
However, translating biomedical research into beneﬁcial com-
phy (PET) and single-photon emission computed tomography
mercial and proﬁtable products is often difﬁcult due to different
(SPECT), can provide a valuable tool for functional evaluation of
expertise and the mutual understanding of objectives and
the atherosclerotic disease. PET and SPECT can demonstrate signif-
requirements of the scientiﬁc community, clinicians and indus-
icant artery stenoses, while co-registration with other modalities
try. Therefore, partnerships and information exchange among
(PET-CT, PET-MRI, SPECT-CT) is widely used enabling a com-
academic, medical and industrial institutions are necessary in
bined study of plaques’ structure and function
developing systems which will be incorporated in current clin-
18F-ﬂuorodeoxyglucose nuclear image analysis has been used to
ical practice, thereby optimizing the delivery of healthcare for
identify inﬂamed atherosclerotic plaques detect signs of
atherosclerosis. Such systems are expected to signiﬁcantly con-
biological effects of experimental drugs
tribute to the vision of occidental countries to manage prevalent
Intravascular ultrasound (IVUS) has emerged as a valuable imag-
chronic diseases, enhance patient safety through prediction, opti-
ing modality for atherosclerosis, especially for the assessment of
mized treatments, and fewer medical errors, halt the rising cost of
ambiguous lesions, as those located in the left main coronary artery
healthcare without compromising quality and efﬁciency, bridge the
or at bifurcation sites. Measurements on IVUS images are able to
gap between research and medical practice, and realize the health
demonstrate changes in plaque lesion size with time and treatment
IVUS studies are more limited because of the ﬁnan-
To conclude, given that atherosclerosis holds a major risk for
cial cost, the increase in the time of the procedure, and the fact that
both public health and state economies, and the current ‘one-size-
it is considered an interventional procedure.
ﬁts-all’ approach has been shown to be inadequate and inefﬁcient,
Because of its low cost, non-invasiveness and short time of
it is crucial to reveal novel, personalized and low-cost markers that
examination, duplex ultrasound is commonly used in monitor-
will upgrade the medical practice for the disease. Computerized
ing and tracking progression of atherosclerotic disease. Analysis of
analysis of vascular images, and particularly ultrasound ones, plays
ultrasound images of the neck allows measurements of (i) the thick-
a valuable role in this ﬁeld and is expected to continue receiving
ness of two layers of the wall of the carotid artery (the so-called
signiﬁcant attention by future research.
carotid intima-media thickness) which has emerged as one of the
most powerful tools for the evaluation of subclinical atherosclero-
sis drug response (ii) texture indices of carotid
plaques which in several studies have been correlated with plaque
stability symptom status motion-based features
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