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doi:10.1016/j.jcmg.2010.02.007 2010;3;761-771 J. Am. Coll. Cardiol. Img.

Sijbrands, Folkert J. ten Cate, and Steven B. Feinstein Steen, Jess D. Reed, Christian Krueger, Kai E. Thomenius, Dan Adam, Eric J.

Daniel Staub, Arend F.L. Schinkel, Blai Coll, Stefano Coli, Antonius F.W. van der Atherosclerosis to the Identification of Unstable Plaques

Contrast-Enhanced Ultrasound Imaging of the Vasa Vasorum: From Early

This information is current as of July 12, 2010

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ontrast-Enhanced Ultrasound Imagingf the Vasa Vasorumrom Early Atherosclerosis to the Identification of Unstable Plaques

aniel Staub, MD,*† Arend F. L. Schinkel, MD, PHD,*‡ Blai Coll, MD, PHD,¶tefano Coli, MD,# Antonius F. W. van der Steen, PHD,§** Jess D. Reed, PHD,††hristian Krueger, BS,†† Kai E. Thomenius, PHD,‡‡ Dan Adam, PHD,§§ric J. Sijbrands, MD, PHD,� Folkert J. ten Cate, MD, PHD,‡ Steven B. Feinstein, MD*

hicago, Illinois; Basel, Switzerland; Rotterdam and Utrecht, the Netherlands; Lleida, Spain;arma, Italy; Madison, Wisconsin; Niskayuna, New York; and Haifa, Israel

roliferation of the adventitial vasa vasorum (VV) is inherently linked with early atherosclerotic plaque

evelopment and vulnerability. Recently, direct visualization of arterial VV and intraplaque neovascular-

zation has emerged as a new surrogate marker for the early detection of atherosclerotic disease. This

linical review focuses on contrast-enhanced ultrasound (CEUS) as a noninvasive application for identify-

ng and quantifying carotid and coronary artery VV and intraplaque neovascularization. These novel

pproaches could potentially impact the clinician’s ability to identify individuals with premature cardio-

ascular disease who are at high risk. Once clinically validated, the uses of CEUS may provide a method to

oninvasively monitor therapeutic interventions. In the future, the therapeutic use of CEUS may include

ltrasound-directed, site-specific therapies using microbubbles as vehicles for drug and gene delivery

ystems. The combined applications for diagnosis and therapy provide unique opportunities for clinicians

o image and direct therapy for individuals with vulnerable lesions. (J Am Coll Cardiol Img 2010;3:

61–71) © 2010 by the American College of Cardiology Foundation

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therosclerotic cardiovascular disease andeath remain the leading cause of morbiditynd mortality in the Western world (1). There-ore, it is increasingly important to identifyat-risk” individuals, referred to as “vulnerable”atients (2). Over the last few years, it has been

rom the *Department of Internal Medicine, Section of CardiologDepartment of Internal Medicine, Division of Angiology, Uniepartment of Cardiology, §Biomedical Engineering Departmeetabolic Diseases, Department of Internal Medicine, Erasmus Meiagnòstic i Tractament de Malalties Aterotrombòtiques (UDET

Division of Cardiology, Department of Heart and Lung, Aziend*Interuniversity Cardiology Institute of the Netherlands, Utrecht,niversity of Wisconsin, Madison, Wisconsin; ‡‡GE Global Reseaiomedical Engineering, Technion–Israel Institute of Technology,rant from the Swiss National Science Foundation (Grant PBZr. Feinstein has received speaker’s honorarium fees from Takedahomenius is an employee of GE Global Research.

anuscript received November 3, 2009; revised manuscript received Ja

by Simaging.onlinejacc.orgDownloaded from

roposed that the use of noninvasive screeningmaging systems provides safe and reliable

ethods for the early detection of surrogatearkers of atherosclerosis, and helps to identify

ndividuals exhibiting an unstable or vulnerablelaque (2,3).

ush University Medical Center, Chicago, Illinois;ty Hospital, Basel, Switzerland; ‡Thoraxcenter,and �Division of Pharmacology, Vascular andl Center, Rotterdam, the Netherlands; ¶Unitat de), Hospital Arnau de Vilanova, Lleida, Spain;

spedaliero-Universitaria di Parma, Parma, Italy;Netherlands; ††Department of Animal Sciences,Niskayuna, New York; and the §§Department ofa, Israel. Dr. Staub was supported by a fellowship-120997) and the Swiss Society of Angiology.Abbott, and research funding from Abbott. Dr.

nuary 20, 2010, accepted February 18, 2010.

teven Feinstein on July 12, 2010


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Staub et al.

Contrast-Enhanced Ultrasound and Vasa Vasorum

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The list of current noninvasive imaging methodsncludes carotid ultrasound as well as cardiovascularomputed tomography (CT) and cardiac magneticesonance (CMR) (2,4,5). Furthermore, the use ofltrasound contrast agents is emerging as a potentiallymportant diagnostic tool to complement and enhanceoutine, vascular ultrasound imaging (6). Importantly,ontrast-enhanced ultrasound (CEUS) can visualizeasa vasorum (VV) in the adventitial layer as well asntraplaque neovascularization (7–12). These 2 micro-ascular networks are both thought to play a centralole in the early process of plaque progression andulnerability, and may also be involved in plaquenflammation (13,14).

Therefore, CEUS appears to be an emergingechnique serving as a valuable method for the earlyetection of premature atherosclerosis and for theetection of vulnerable plaques in at-risk popula-ions (7,8). This clinical review focuses on CEUS as

a noninvasive application for identifyingand quantifying VV and intraplaque neo-vascularization.

Physiology of VV

Vasa vasorum are defined as small bloodvessels that supply or drain the walls of thelarger arteries and veins, and connect witha branch of the same vessel or a neighbor-ing vessel to form a network of small bloodvessels. These lesser known vessels arenormally present and represent a physio-logic mechanism designed to supply nutri-ents to the tissues within the arterial walls.The extent and distribution of neovascu-

arization within the arterial wall is dependent uponnumber of physiologic “drivers.” Perhaps one of

he leading candidates for the initiation of neovas-ularization focuses on vessel wall hypoxia andnflammation (15). Specifically, viable cells withinn arterial wall located in excess of 250 to 500 �mrom the lumen do not receive adequate nutrients;herefore, the adventitial VV supply an extrinsicource of nourishment (16). Based on substantialistorical and clinical observations, there is evidencehat supports the concept that the adventitial VV arentegrally involved in the origins of atherosclerosis, so

uch so that the development and destabilization oftheromatous plaques may be linked to intraplaqueemorrhage and/or inflammation (13,17). It is be-

ieved that initially, hyperplasia of the adventitial VVccurs in the early phases of the inflammation/

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therosclerosis, the appearance of new microvesselsxtends to the media and intima, constituting anctopic neovascularization. Supporting the concepthat VV appearance correlates with the extent oftherosclerosis, Moulton (18) reported a 9-fold in-reased incidence of intimal neovascularization indvanced atheromas of mouse aortas. Micro-CT im-ges of atherosclerotic aortas showed that VV com-unicate with intraplaque capillaries and correlateith progression of atherosclerosis. Furthermore, Dri-ane et al. (19) found that inhibition of VV growthsing truncated plasminogen activator inhibitor-1rotein in a similar mouse model leads to reducedtherosclerotic plaque growth. Similarly, neointimalormation (restenosis) after mechanical injury of aoronary artery in rats correlates with adventitial an-iogenesis, and can be influenced by angiogenesistimulators and inhibitors (20).

In an autopsy study, Fleiner et al. (14) identifiedhat VV hyperplasia characterized vulnerablelaques in patients who suffered mortal cardiovas-ular events. Importantly, the authors noted thathe presence of extensive hyperplasia of adventitialV was observed in symptomatic individuals in

dvance of the development of significant intimalhickening, and that arterial ectopic neovasculariza-ion and inflammation in iliac, carotid, and renalrteries characterized the vulnerable patient associ-ted with cardiovascular events.

Additionally, numerous clinical reports lend cre-ence to the hypothesis that plaque neovasculariza-ion serves to discriminate active versus nonactivevulnerable) plaques in symptomatic versus asymp-omatic subjects. The presence of VV (angiogenicessels) has been consistently observed in systemicrteries, including the aorta, coronaries, carotids,nd the femoral arteries (13,14,17,21,22). Dunmoret al. (23) recently published their results advancingheir previous reports in which they state thatymptomatic carotid plaques contain abnormal, im-ature microvessels, and such vessels could contrib-

te to plaque instability by acting as sites of vasculareakage and inflammatory cell recruitment.

isk Factors for VV-Derived Neovascularization

variety of local and systemic factors apparentlynfluences the development of neovascularization inhe artery wall, thus influencing the development oftherosclerosis and leading to subsequent destabili-ation of atheroma plaques. Cellular/tissue hypoxiacting as a local stimulus appears to be identified

B B R E V I A T I O N S

N D A C R O N YM S

D � 2-dimensional

D � 3-dimensional

EUS � contrast-enhanced

ltrasound

-IMT � carotid intima–med

hickness

MR � cardiac magnetic

esonance

T � computed tomography

VUS � intravascular ultraso

ith the development of nascent VV. Recently,

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luimer et al. (24) studied the presence of in-raplaque hypoxia, the molecules involved, and theole of hypoxia in the better characterization oftheroma plaques. They identified that the presencef cellular hypoxia, notably within the plaques, wasssociated with a high level of macrophages. Cel-ular hypoxia correlated with the presence of throm-us, angiogenesis, expression of CD68, hypoxianducible factor (HIF), and vascular endothelialrowth factor. The mRNA and protein expressionf HIF, its target genes, and microvessel densityncreased from early to stable lesions. These find-ngs demonstrated the link between cellular/tissueypoxia, atherosclerotic lesion progression, and in-raplaque angiogenesis.

Additionally, hypercholesterolemia is a well-stablished and recognized cardiovascular risk factornd is associated with hyperplasia of the VV in therterial wall. Kwon et al. (25) performed a series ofxperiments in which they used micro-CT to iden-ify coronary artery VV in swine. In their study,sing hypercholesterolemic swine, a dense and dis-rganized network of VV was created within thedventitia. Consistent with the clinical report ofleiner et al. (14), these structural changes (i.e.,

ncrease in the VV network) appear to precede theevelopment of endothelial dysfunction, often con-idered a initiating step in atherosclerosis develop-ent, as identified by Herrmann et al. (26). Wilson

t al. (27) noted that initiating treatment with aipid-lowering agent (statin) resulted in a substan-ial reduction in the observed coronary artery VVetwork. This statin effect occurred despite thebsence of a significant change in the serum lipidrofile. These observations support an additionalechanism for the vascular effects of lipid-reducing

gents, which appears to act independently of over-ll cholesterol lowering.

More recently, Kolodgie et al. (28) reviewedmerging therapeutic strategies that appear to blockeovascularization within the arterial wall. In-raplaque hemorrhage appears to result from theevelopment of immature neointimal VV (“leaky”essels). Therefore, the authors proposed that mo-ecular therapies focused on the elimination ofathologic neovascularization within developing le-ions reduce intraplaque hemorrhage. Apparently,he application of these therapeutic approachesrovided positive treatment results in studies thatnvolved similar neovascular-dependent diseasesincluding macular degeneration and malignancies)29,30). On the basis of their results, the authors
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elective local antiangiogenic agents could contrib-te to prevention of plaque progression and itslinical consequences (28).

oninvasive Imaging of VV in Experimental Models

oninvasive imaging techniques provide a uniquepportunity to monitor the serial, progressive patho-hysiologic developments associated with experimen-al atherosclerosis in animal models. Often, mechan-cal approaches are combined with metabolic stimuliuch as hypercholesterolemia or hyperglycemia,nd/or physiological stimuli such as hypertension or aelatively hypoxic state to induce atherosclerosis andeovascularization experimentally (25,31–33). The 3ost promising noninvasive imaging strategies that

re currently available are microscopic 3-dimensional3D) CT, CMR, and CEUS.

As earlier noted, Kwon et al. (25) studied the 3Dnatomy of the VV in early coronary atherosclerosissing microscopic CT in normal and experimentalypercholesterolemic porcine coronary arteries. Ad-itionally, high-resolution CMR can be used inonjunction with a gadofluorine-based contrastgent for characterization of atheroscleroticlaques. Sirol et al. (31) studied aortic plaques inabbits with contrast-enhanced CMR. Atheroscle-otic plaque enhancement correlated with his-opathological neovessel density. This may be re-ated to the increased permeability of VV intherosclerotic plaques, promoting exchange ofontrast agent between the blood pool and thetherosclerotic plaque. Cornily et al. (32) reportedimilar findings with a novel gadolinium-basedontrast agent and CMR. CMR showed a signifi-ant plaque enhancement in the atheroscleroticabbit aortas that correlated with neovessel andacrophage density at histopathological examina-

ion. Hence, CMR can be used to quantify markersf plaque vulnerability, including neovascularizationnd macrophage content.

Real-time CEUS provides a unique opportunityor the evaluation of VV in living animal models.ltrasound contrast agents consist of gas-filledicrospheres that serve as true intravascular tracers

nd can be visualized using ultrasound as theicrospheres transit the VV (8). Our group studied

he development of atherosclerosis and density ofhe VV network in Rapacz familial hypercholester-lemia swine (33). Percutaneous transluminal injec-ions of an atherogenic suspension were directlynjected into the femoral arteries along with
alloon-induced mechanical injury of the endothe-
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ium. This combined approach led to the develop-ent of atherosclerotic lesions. The progression of

he VV network was monitored by CEUS and lateronfirmed by histology (Fig. 1). In the future, thisnimal model in combination with CEUS mayrovide useful insights into the role of VV associ-ted with atherosclerosis and may help to test novelharmacological and device therapies for the treat-ent of atherosclerosis.

oninvasive Imaging Techniques in thelinical Setting

arotid B-mode ultrasound. Measurement of carotidntima–media thickness (c-IMT) and determininghe presence of focal atherosclerotic plaques usingarotid ultrasonography did emerge as widely ac-epted surrogate markers of atherosclerosis4,34,35). Numerous studies have shown that in-reased c-IMT and the presence of carotid plaquere associated with traditional coronary risk factors,nd several clinical trials support the role of c-IMTeasurements and carotid plaque assessments for

redicting cardiovascular events (36–38). Accord-ngly, c-IMT has become a meaningful surrogatend point for interventional trials (39,40).

The c-IMT is defined as the distance betweenhe lumen–intima interface and the media–dventitia interface (41). Today, c-IMT is mostommonly measured in the common carotid arteryn the far wall from B-mode (2-dimensional [2D])mages with linear ultrasound transducers typicallytilizing frequencies between 7.5 and 10 MHz (34).he arterial wall segment should be assessed in a

5 weeks 12 week

A B

Figure 1. Progression of VV on CEUS

Contrast-enhanced ultrasound (CEUS) still frames demonstrating anfemoral artery during follow-up in a Rapacz hypercholesterolemia sfollow-up, (B) shows limited VV at 12 weeks, and (C) shows extensi
is indicated by the white arrow. Reproduced, with permission, from Sch

ongitudinal view, and semiautomated c-IMT mea-urement may be performed along a minimum of0-mm length of the selected segment using andge detection algorithm.

In addition to the c-IMT, discrete carotidlaques, commonly defined as a focal structure thatncroaches into the arterial lumen of at least 50% ofhe surrounding c-IMT value or demonstrates ahickness of �1.5 mm as measured from the me-ia–adventitial interface to the intima–lumen inter-ace, can be assessed by through scanning of thextracranial carotid arteries (41). However, givenhe variable and complex 3D morphology oflaques, precise quantification of plaque burdensing 2D B-mode ultrasound imaging is problem-tic (4). Furthermore, the use of ultrasound contrastgents provides direct information on arterial walliology and inflammation through the detection ofessel wall angiogenesis (VV) (7).EUS. The clinical applications of CEUS for vas-ular use include enhancement of the carotid arteryumen, which results in improved visualization ofuminal irregularities including soft plaques, dissec-ions, and ulcerations (Fig. 2) (7,42,43). Moreover,EUS techniques provide superior enhancement of

he proximal walls, leading to improved efficiencynd precision of measurements for the c-IMT (42).ased on the knowledge that the acoustically reflec-

ive microspheres serve as ideal intravascular tracers,he real-time, microvascular assessment of the spa-ial and temporal heterogeneity of adventitial andntraplaque VV was revealed (7,44). Subsequent tohese pioneering observations, several independenteports similarly using CEUS techniques confirmed

43 weeks

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he initial discoveries, including the observationshat CEUS permitted direct visualization of adven-itial VV and intraplaque angiogenesis (Fig. 3)9–12,45–48).

A variety of commercially available ultrasoundontrast agents have been used for VV imaging,ncluding perflutren protein type-A microspheresOptison, GE Healthcare, Little Chalfont, Buck-nghamshire, UK), perflutren lipid microspheresDefinity, Bristol-Myers Squibb Medical Imaging,illerica, Massachusetts), and phospholipid-

tabilized microspheres of sulfur hexafluorideSonoVue, Bracco Altana Pharma, Konstanz, Ger-any) (6). Typically, these agents are routinely

njected via a peripheral vein as a bolus, followed bysaline flush. CEUS imaging of the carotid artery

s generally practiced using a linear array vascularrobe with transmission frequencies ranging from 4o 10 MHz and dedicated contrast imaging soft-are utilizing pulse inversion or harmonic tech-iques. Of importance, the mechanical index used

Figure 2. Contrast-Enhanced Carotid Ultrasound Imaging Witho

Carotid artery with intraluminal plaque on B-mode ultrasound imagsound (left panel). The intima–media complex (IMT) is depicted asintraluminal plaque.

Figure 3. Carotid Artery With Intraplaque Neovascularization on

Plaque at the origin of the internal carotid artery on B-mode ultraso
enhanced ultrasound (CEUS) (left panel) with visible microbubbles with

or CEUS in carotid vascular clinical studies wasowered and ranged between 0.06 and 0.2; allettings were considerably reduced as comparedith the mechanical index used in unenhanced

tudies. Therefore, when using a reduced mechan-cal index for imaging, the plaques and correspond-ng intima–media complex appear hypoechoic,hereas the adventitial layer is observed as echo-enic (Fig. 2). The dynamic flow patterns of theasculature are represented by the presence of in-ravascular tracers (acoustic microspheres), whichass unhindered through the adventitial and thentraplaque VV (Fig. 3).

uantification of VV andntraplaque Neovascularization

EUS. Quantification of the VV remains a majorssue confronting the future development and im-lementation of CEUS as a clinically useful imag-

ntraplaque Neovascularization

(right panel). Corresponding artery on contrast-enhanced ultra-poechoic line. No visible microbubbles are seen within the

US

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ng technique. Clearly, the advent of 3D/4-imensional volumetric imaging will provide theecessary foundation for the detection and quanti-cation of angiogenesis within the vascular systemsadventitial and intraplaque VV). Further, the util-ty of providing a volumetric assessment of tumorlood volume will promote the future diagnosticnd therapeutic clinical utility of CEUS.

Currently, all the observational studies that useEUS for VV detection and quantification employD ultrasound imaging and semiquantitative ap-roaches (Table 1) (6,10,45,47,48).Coli et al. (11), using a clinically accepted dichot-

mous grading system, categorized CEUS enhance-ent as no contrast effect or high based on the visual

etection of the contrast effect within the plaque (Figs.and 3). A similar grading system was applied by

ther researchers in their studies (10,12,47).Subsequent authors provided additional quanti-

ative approaches, including a case report by Papa-oannou et al. (46) in which the authors quantified

ean gray-level and entropy measurements in thelaque region. The authors demonstrated that fol-

owing an intravenous injection of ultrasound con-rast agents, there exist quantifiable alterations inhe reflectivity of the carotid plaque obtained usingarmonic software. Similarly, clinical researchersrom China described the enhancement of carotidlaques after injection of contrast material usingignal-time intensity curve analysis. The region ofnterest was established based on visual recognitionnd a semiquantitative categorization for eachlaque (48).Two recent studies using a systematic, his-

opathological validation revealed a direct, positiveorrelation between contrast enhancement and his-ology (Table 1) (10,11). In a case report, Vicenzinit al. (45) described visualization of contrast-agenticrobubbles within the plaques as a marker of

eovascularization and confirmed, corresponding tohe CEUS image, the presence of the microvesselithin the plaque at histology after endarterectomy.Additional semiquantitative measurement of VV

as reported by Magnoni et al. (9). In their work, theuthors performed a quantitative determination ofdventitial VV by measuring periadventitial signalhickness using contrast-enhanced, B-flow imaging.

Thus, although there is independent confirma-ion and clinical consensus regarding the clinicalses of CEUS for identifying adventitial and in-raplaque VV in patients, a true, quantifiable volu-etric analysis of VV remains elusive. Clearly, as
EUS imaging moves into the future, the ability to s

erform an analysis of tumor blood flow (includingarotid atherosclerotic plaques) remains a criticalomponent for both diagnostic and therapeuticpplications.V: Intravascular ultrasound (IVUS). Imaging of thearotid VV using CEUS is a promising develop-ent. Imaging of the VV of coronary arteries using

ransthoracic ultrasound seems a bridge too far.ith limited resolution and associated motion

rtifact, these impediments limit the potential tochieve an acceptable contrast-to-tissue ratio forV coronary imaging.With the recent interest in VV of the carotid

rteries using CEUS, there is accompanying inter-st in developing an IVUS application for measure-ent of coronary VV. IVUS systems generally

perate at acoustic frequencies in the range of 20nd 50 MHz. Although these parameters provideigh spatial resolution (�150 to 300 �m) withross-sectional images of the lumen and walls ofarger blood vessels, these specifications may notrovide optimization of the harmonic contrast effectesulting in visualization of the coronary artery VV.nown clinically, the applications of IVUS include

ssessment of atherosclerotic coronary lesions, siteuidance for stent deployment, and monitoringtherosclerosis lesions for clinical trials. In order toccommodate the acoustic parameters associatedith CEUS, ultrasound contrast agents have pri-arily been designed to be used at low frequencies,

rom 1 to 5 MHz. Despite conventional belief tohe contrary, Goertz et al. (49) have shown that it isossible to identify CEUS signals at the higherrequencies used specifically for IVUS.

Carlier et al. (50) reported that bolus injections ofontrast agents could give rise to IVUS echogenicitynhancement in the adventitia of coronary arteries,onsistent with the detection of VV. However, thispproach uses linear IVUS, is restricted to a singlemaging plane, and is critically sensitive to thessumption that images acquired at the same pointf successive cardiac cycles are not affected by tissueotion. Small deviations from this will result in

ignificant artifact enhancement of the signal.Harmonic IVUS seems a more fruitful approach

51). Conventional IVUS elements have a band-idth that is too limited for optimal harmonic

maging though. A new generation of IVUS ele-ents based on dual resonance layers, capacitiveicromachined ultrasound transducers, single crys-

al technology, or composite transducers is underevelopment (52). Granada and Feinstein (8)
howed enhanced adventitial signal in coronary


Table 1. Overview of Clinical Studies Using CEUS Imaging for Assessment of Carotid Artery VV

Reference (No.)No. of Patients/

Plaques PopulationVasa Vasorum

Quantification on CEUSVasa Vasorum

Quantification on Histology Main Results

Shah et al., 2007 (10) 15/17 Age NR, 59% male, 6symptomatic (TIA/stroke)

Intraplaque neovascularizationgrade 0 (not present),grade 1 (limited), grade 2(moderate), and grade 3(pulsating arterial vessel)

17 CEA specimens, neovascularization(CD31, CD34, vWF) grade 0 (none),grade 1 (minimal), grade 2(moderate), and grade 3(extensive)

Neovascularization on CEUS correlateswith histology (Spearman rank: 0.68)

Vicenzini et al., 2007 (45) 23/NR Age 70� 3.5 yrs, 70% male,asymptomatic for stroke/TIAand MI

Intraplaque neovascularizationpresent/not present

1 CEA specimen, microvessel withinthe plaque (descriptive)

Neovascularization on CEUS correlateswith plaque echogenicity andcorresponds to histology

Coli et al., 2008 (11) 32/52 Age 70 � 8 yrs, 84% male, 6symptomatic (stroke/TIAwithin 6 months)

Intraplaque neovascularizationgrade 1 (not present) andgrade 2 (present)

17 CEA specimens, no. of VV/mm2

(CD31, CD34)Intraplaque neovascularization correlates

with histology (VV density 3.24/mm2

in plaque grade 2 vs. 1.82/mm2 ingrade 1; p � 0.005), and with plaqueechogenecity (higher degree ofcontrast enhancement in echolucentplaques, p � 0.001)

Magnoni et al., 2008 (9) 40/NR 25 with carotid atherosclerosis(age 65.5 � 12 yrs, 80%male), 15 control withoutstenosis (age 71 � 8 yrs,77% male)

Quantitative analysis ofadventitial VV(periadventitial flow signalthickness using contrast-enhanced, B-flow imaging)

NR Adventitial VV is more pronounced inthe atherosclerotic group than in thecontrol group (1.10 � 0.11mm vs.0.80 � 0.06 mm; p � 0.0001);adventitial VV correlates with c-IMT(r � 0.88; p � 0.0001)

Papaioannou et al.,2009 (46)

1/1 73-year-old male with acutecoronary syndrome

Quantitative analysis ofintraplaqueneovascularization byplaque gray-scale level andentropy

NR Increased plaque gray level and entropyafter contrast agent injection,indicating intraplaqueneovascularization

Giannoni et al.,2009 (47)

77/73 Age 67 � 6 yrs, 66% male, 64asymptomatic, 9symptomatic (stroke/TIA inprevious 6 months)

Intraplaqueneovascularization, type I(rare discrete), type II(diffuse contrastenhancement)

73 CEA specimens, neovascularization(VEGF, MMP3, CD31, CD34)

Neovascularization type II in 1/64asymptomatic plaques, and in 9/9symptomatic plaques (p � 0.001);neovascularization on CEUScorresponds to histology (highdensity of microvessels)

Xiong et al., 2009 (48) 104/104 Age 63 � 9 yrs, 80% male, 35symptomatic (stroke/TIA),69 asymptomatic

Intraplaque neovascularizationgrade 1 (not present) andgrade 2 (present), andquantitative measurementby signal intensity analysis

NR Neovascularization grade 2 in 80% ofsymptomatic vs. 30% inasymptomatic patients (p � 0.001);enhanced intensity in the plaque isgreater in symptomatic thanasymptomatic patients (13.9 � 6.4 dBvs. 8.8 � 5.2 dB; p � 0.001)

Staub et al., 2010 (12) 147/111 Age 64�11, 61% male, 89with cardiovascular diseaseand 37 with history ofcardiovascular events (MI,stroke/TIA)

Adventitial VV grade 1 (notpresent) and grade 2(present), intraplaqueneovascularization grade 1(not present) and grade 2(present)

NR Adventitial VV (grade 2) is associatedwith cardiovascular disease (OR: 2.3,95% CI: 1.1–4.8), and intraplaqueneovascularization (grade 2) isassociated with history ofcardiovascular events (OR: 4.0, 95%CI: 1.3–12.6)

CEA � carotid endarterectomy; CEUS � contrast-enhanced ultrasound; CI � confidence interval; MI � myocardial infarction; MMP3 � matrix metalloproteinase 3; NR � not reported; OR � odds ratio; TIA � transient ischemic attack; VEGF � vascularendothelial growth factor; VV � vasa vasorum; vWF � von Willebrand factor.

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rteries in a swine model for atherosclerosis usingarmonic IVUS approach.Goertz et al. reported detailed detection and

ocalization of VV in an atherosclerotic rabbit aortaodel using a dual-frequency IVUS element and

ulse inversion followed by filtering out the har-onic (53) or subharmonic (54) signals. Figure 4

hows an example of VV detection in this model.IVUS VV detection is not ready for clinical use

et. Quantification and a thoughtful strategy for 3Deconstruction of the VV remain to be developed.n the near future, perhaps, IVUS imaging of theoronary VV could serve as an additional biomarkerf plaque vulnerability along with gray-scale analy-is, plaque burden assessment, quantitative flowssessment, and radio frequency–based tissue typ-ng (virtual histology) and palpography (55).omparative imaging modalities of VV. A plethora ofeports have described the applications of otheron-CEUS imaging modalities for visualization ofV and associated atherosclerosis; these includeMR, CT, positron emission tomography, single-hoton emission CT, and hybrid technologies5,56) along with molecular imaging techniques57,58).

Kerwin et al. (59,60) analyzed carotid atheroscle-otic plaques using dynamic contrast-enhancedMR for adventitial VV and intraplaque neovas-

ulature in patients scheduled for endarterectomynd in subjects with moderate carotid atheroscle-otic disease. The extent of neovascularizationithin the plaque was quantified using a kineticodel to estimate fractional blood flow (59) and

ransfer constant (60) based on changes in signal

Figure 4. In Vivo Results in an Atherosclerotic Rabbit Aorta Usi

Left: fundamental mode at 20 MHz, 10 s after injection, in which chafter injection, the harmonic mode (transmit at 20 MHz, receive atthe detection of adventitial microvessels. The white dots are contracontrast agents attached to the luminal border (asterisk). Scale of i
harmonic image is 40 and 25 dB, respectively.

ntensity over time after gadolinium-based contrastgent injection. Because the transfer of the contrastgent to the adventitia is dependent on the VV,hey concluded that adventitial transfer constantikely indicates the extent of the VV. Evidence forhis hypothesis was provided by the fact that quan-itative analysis of VV neovascularization was sig-ificantly correlated with the histological fraction oficrovessel density and macrophages (60). Further-ore, the extent of plaque neovascularization de-

ermined by CMR imaging was positively corre-ated with serum marker of inflammation linked totherosclerotic complications, and was associatedith more advanced plaques. In line with thesendings, Lombardo et al. performed contrast-nhanced carotid CMR in patients with acuteoronary syndrome and in controls with carotidtherosclerosis (61). In these subjects, all withcute coronary syndromes, an enhancement withadolinium indicated increased neovasculariza-ion was noted in 89% of carotid plaques, whereasnly 8% revealed similar enhancement in theontrol group. These studies support the concepthat plaque neovascularization is associated withulnerability and represent a uniformly distrib-ted marker of inflammation throughout theystemic vascular bed (14).

Furthermore, newer molecular imaging technol-gies using targeted contrast agents have beenmerged for inflammation imaging in atherosclero-is (5). Specifically, for CMR and contrast ultra-ound molecular imaging, different sophisticatedontrast agents, such as paramagnetic nanoparticlesargeted to �v�3-integrin that are selectively up-

ecanted Definity

es in adventitial enhancement are not evident. Right: at 10 sHz) shows significant adventitial enhancement, consistent withents in the vasa vasorum (white arrows), and the bright ring,es is 12 mm across. The dynamic range of the fundamental and

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egulated by the neovascular endothelium (62), asell as �v�3-integrin–targeted microbubbles andicrobubbles targeted to growth factor receptors

xpressed during vascular remodeling (58), haveeen evaluated in animal models for imaging ath-rosclerotic and tumor angiogenesis. Furthermore,maging-guided therapy of atherosclerosis has beenvaluated using the combination of magnetic reso-ance molecular imaging and antiangiogenic drugelivery with �v�3-integrin–targeted paramagneticanoparticles in cholesterol-fed rabbits (63). A sin-le application of a minimal drug dosage resulted insignificant reduction of neovasculature within the

rteriosclerotic aortic wall assessed by magneticesonance enhancement and histology. However,one of these techniques have been advanced tovaluate VV neovascularization in clinical studies.

linical impact: VV

dventitial and intraplaque VV remain as distinct,icrovascular nutrient networks intimately associatedith vessel wall diseases and plaque vulnerability (13).herefore, the implications of detecting adventitial

nd ectopic intraplaque VV using CEUS imaging int-risk patients is an important clinical goal.

Histologic analyses and observational clinicaltudies support the concept that hyperplasia ofdventitial VV represents a viable surrogate markerf atherosclerosis that likely presages untowardardiovascular events (14). Based upon the currentiterature, pronounced enhancement of periadven-itial VV associated with CEUS imaging appears toefine carotid atherosclerosis and symptomatic car-iovascular disease (Table 1).Different independent investigators reported thatore pronounced neovascularization assessed byEUS was predominantly observed in echolucent

esions (11,45,48). Importantly, the presence of ancholucent plaque is known to be associated with anncreased risk of cardiovascular events (64,65).hese observations are wholly consistent with the

oncept that more vulnerable plaques contain aigher degree of neovascularization.Additionally, recently published observational

tudies revealed the association between plaquenhancement on CEUS imaging and clinical symp-oms in patients with carotid atherosclerosis12,47,48). Giannoni et al. (47) described thatymptomatic patients showed a specific pattern ofiffuse contrast enhancement on CEUS at the basef the carotid plaque, and a correspondingly high
ensity of microvessels on subsequent histology. 6

Another independent research group used CEUSo assess carotid plaques in patients associated witheurological symptoms (48). An increased preva-

ence of carotid plaque enhancement was observedn symptomatic patients when compared withsymptomatic patients. These findings support theoncept that the VV-derived intraplaque neovascu-arization is associated with plaque instability, per-aps leading to clinical events.Recently, the current authors performed an anal-

sis of consecutive subjects who received carotidEUS. The presence and degree of CEUS for

dventitial and intraplaque VV was significantlyorrelated with the presence of cardiovascular dis-ase and with prior cardiovascular events (12). Thisecent observational study indicated that the risk ofcerebrovascular event assessed from carotid plaquengiogenesis is generalizable to other vascular beds,ncluding coronary events.

Based on these retrospective studies and withppropriate prospective studies, CEUS examinationf the carotid artery may provide a novel, noninva-ive clinical tool to identify and quantify the pres-nce and the extent of the VV network and arteriallaque neovascularization in patients at risk foreveloping symptomatic atherosclerosis, permittingmore reliable assessment of cardiovascular risk.owever, further prospective studies will be re-

uired to establish the scientific basis of usingEUS for the early detection of premature athero-

clerosis and for the detection of vulnerable plaquesn at-risk patients.

At the present time, continued experimental datan appropriate animal models of hypercholesterol-mia (27) and cross-sectional studies of carotidndarterectomy specimens (66) have demonstratedhat VV and intraplaque angiogenesis can be re-uced by antiatherosclerotic therapies. Therefore,uantification of VV and plaque neovascularizationy CEUS imaging may provide an excellent non-nvasive technique to monitor therapeutic interven-ions. In the future, the therapeutic use ofltrasound-directed, site-specific therapies with mi-robubbles for drug and gene delivery could poten-ially provide a unique opportunity for clinicians toirectly image and treat a vulnerable atherosclerotic

esion (67,68).

eprint requests and correspondence: Dr. Steven B. Fein-tein, Rush University, Medical Center, Section of Car-iology, Department of Internal Medicine, 1653 Westongress Parkway, Suite 1015 Jelke, Chicago, Illinois
0612. E-mail: [email protected].

mailto:[email protected]



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E F E R E N C E S

1. Lloyd-Jones D, Adams RJ, BrownTM, et al. Heart disease and strokestatistics—2010 update. A reportfrom the American Heart Association.Circulation 2010;121:948–54.

2. Naghavi M, Falk E, Hecht HS, et al.From vulnerable plaque to vulnerablepatient—Part III: Executive summaryof the Screening for Heart AttackPrevention and Education (SHAPE)Task Force report. Am J Cardiol2006;98:2H–15H.

3. Feinstein SB. Vascular imaging. In:Feinstein SB, editor. Non-invasiveSurrogate Markers of Atherosclerosis.London, UK: Informa Healthcare;2008:85–96.

4. Redberg RF, Vogel RA, Criqui MH,Herrington DM, Lima JA, RomanMJ. 34th Bethesda Conference: Taskforce #3—What is the spectrum ofcurrent and emerging techniques forthe noninvasive measurement of ath-erosclerosis? J Am Coll Cardiol 2003;41:1886–98.

5. Sanz J, Fayad ZA. Imaging of athero-sclerotic cardiovascular disease. Na-ture 2008;451:953–7.

6. Feinstein SB, Coll B, Staub D, et al.Contrast enhanced ultrasound imag-ing. J Nucl Cardiol 2010;17:106–15.

7. Feinstein SB. Contrast ultrasound im-aging of the carotid artery vasa vaso-rum and atherosclerotic plaque neo-vascularization. J Am Coll Cardiol2006;48:236–43.

8. Granada JF, Feinstein SB. Imaging ofthe vasa vasorum. Nat Clin Pract Car-diovasc Med 2008;5 Suppl 2:S18–25.

9. Magnoni M, Coli S, Marrocco-TrischittaM, et al. Contrast-enhanced ultrasoundimaging of periadventitial vasa vasorumin human carotid arteries. Eur J Echo-cardiogr 2009;10:260–4.

0. Shah F, Balan P, Weinberg M, et al.Contrast-enhanced ultrasound imag-ing of atherosclerotic carotid plaqueneovascularization: a new surrogatemarker of atherosclerosis? Vasc Med2007;12:291–7.

1. Coli S, Magnoni M, Sangiorgi G, et al.Contrast-enhanced ultrasound imagingof intraplaque neovascularization in ca-rotid arteries: correlation with histologyand plaque echogenicity. J Am CollCardiol 2008;52:223–30.

2. Staub D, Patel MB, Tibrewala A, etal. Vasa vasorum and plaque neovas-cularization on contrast-enhanced ca-rotid ultrasound imaging correlateswith cardiovascular disease and pastcardiovascular events. Stroke 2010;41:41–7.

3. Moreno PR, Purushothaman KR,Sirol M, Levy AP, Fuster V. Neovas-

imaging.onliDownloaded from

cularization in human atherosclerosis.Circulation 2006;113:2245–52.

14. Fleiner M, Kummer M, Mirlacher M,et al. Arterial neovascularization andinflammation in vulnerable patients:early and late signs of symptomaticatherosclerosis. Circulation 2004;110:2843–50.

15. Sluimer JC, Daemen MJ. Novel con-cepts in atherogenesis: angiogenesisand hypoxia in atherosclerosis.J Pathol 2009;218:7–29.

16. Heistad DD, Marcus ML. Role ofvasa vasorum in nourishment of theaorta. Blood Vessels 1979;16:225–38.

17. Kolodgie FD, Gold HK, Burke AP, etal. Intraplaque hemorrhage and pro-gression of coronary atheroma.N Engl J Med 2003;349:2316–25.

18. Moulton KS. Angiogenesis in athero-sclerosis: gathering evidence beyondspeculation. Curr Opin Lipidol 2006;17:548–55.

19. Drinane M, Mollmark J, ZagorchevL, et al. The antiangiogenic activity ofrPAI-1(23) inhibits vasa vasorum andgrowth of atherosclerotic plaque. CircRes 2009;104:337–45.

20. Khurana R, Zhuang Z, Bhardwaj S, etal. Angiogenesis-dependent and inde-pendent phases of intimal hyperplasia.Circulation 2004;110:2436–43.

21. McCarthy MJ, Loftus IM, ThompsonMM, et al. Angiogenesis and the ath-erosclerotic carotid plaque: an associ-ation between symptomatology andplaque morphology. J Vasc Surg 1999;30:261–8.

22. Kumamoto M, Nakashima Y, SueishiK. Intimal neovascularization in hu-man coronary atherosclerosis: its ori-gin and pathophysiological signifi-cance. Hum Pathol 1995;26:450–6.

23. Dunmore BJ, McCarthy MJ, NaylorAR, Brindle NP. Carotid plaque insta-bility and ischemic symptoms are linkedto immaturity of microvessels withinplaques. J Vasc Surg 2007;45:155–9.

24. Sluimer JC, Gasc JM, van Wanroij JL,et al. Hypoxia, hypoxia-inducible tran-scription factor, and macrophages inhuman atherosclerotic plaques are cor-related with intraplaque angiogenesis.J Am Coll Cardiol 2008;51:1258–65.

25. Kwon HM, Sangiorgi G, Ritman EL,et al. Enhanced coronary vasa vasorumneovascularization in experimentalhypercholesterolemia. J Clin Invest1998;101:1551–6.

26. Herrmann J, Lerman LO, Rodriguez-Porcel M, et al. Coronary vasa vaso-rum neovascularization precedes epi-cardial endothelial dysfunction in
experimental hypercholesterolemia.Cardiovasc Res 2001;51:762–6.
by Steven Feinstein on July 1nejacc.org

7. Wilson SH, Herrmann J, LermanLO, et al. Simvastatin preserves thestructure of coronary adventitial vasavasorum in experimental hypercholes-terolemia independent of lipid lower-ing. Circulation 2002;105:415–8.

8. Kolodgie FD, Narula J, Yuan C,Burke AP, Finn AV, Virmani R.Elimination of neoangiogenesis forplaque stabilization: is there a role forlocal drug therapy? J Am Coll Cardiol2007;49:2093–101.

9. Do DV. Antiangiogenic approachesto age-related macular degeneration inthe future. Ophthalmology 2009;116:S24–6.

0. Wagner AD, Arnold D, Grothey AA,Haerting J, Unverzagt S. Anti-angiogenic therapies for metastaticcolorectal cancer. Cochrane DatabaseSyst Rev 2009:CD005392.

1. Sirol M, Moreno PR, PurushothamanKR, et al. Increased neovasculariza-tion in advanced lipid-rich atheroscle-rotic lesions detected by gadofluorine-M-enhanced MRI: implications forplaque vulnerability. Circ CardiovascImaging 2009;2:391–6.

2. Cornily JC, Hyafil F, Calcagno C, etal. Evaluation of neovessels in athero-sclerotic plaques of rabbits using analbumin-binding intravascular con-trast agent and MRI. J Magn ResonImaging 2008;27:1406–11.

3. Schinkel AFL, Krueger CG, TellezA, et al. Contrast-enhanced ultra-sound for imaging vasa vasorum: com-parison with histopathology in a swinemodel of atherosclerosis. Eur J Echo-cardiogr 2010 Apr 12 [E-pub ahead ofprint].

4. Coll B, Feinstein SB. Carotid intima-media thickness measurements: tech-niques and clinical relevance. CurrAtheroscler Rep 2008;10:444–50.

5. Jaeger KA, Staub D. Did you measurethe intima-media thickness? Ultras-chall Med 2009;30:434–7.

6. Touboul PJ, Hernandez-Hernandez R,Küçükoglu S, et al. Carotid artery in-tima media thickness, plaque and Fram-ingham cardiovascular score in Asia,Africa/Middle East and Latin America:the PARC-AALA study. Int J Cardio-vasc Imaging 2007;23:557–67.

7. Lorenz MW, Markus HS, Bots ML,Rosvall M, Sitzer M. Prediction ofclinical cardiovascular events with ca-rotid intima-media thickness: a sys-tematic review and meta-analysis. Cir-culation 2007;115:459–67.

8. Prati P, Tosetto A, Vanuzzo D, et al.Carotid intima media thickness andplaques can predict the occurrence of
ischemic cerebrovascular events.Stroke 2008;39:2470–6.
2, 2010


3

4

4

4

4

4

4

4

4

4

4

6

6

6

6

6

6

6

6

Kca


J U L Y 2 0 1 0 : 7 6 1 – 7 1

Staub et al.


771

9. Bots ML. Carotid intima-mediathickness as a surrogate marker forcardiovascular disease in interventionstudies. Curr Med Res Opin 2006;22:2181–90.

0. Taylor AJ, Villines TC, Stanek EJ, et al.Extended-release niacin or ezetimibeand carotid intima-media thickness.N Engl J Med 2009;361:2113–22.

1. Touboul PJ, Hennerici MG, MeairsS, et al. Mannheim intima-mediathickness consensus. Cerebrovasc Dis2004;18:346–9.

2. Macioch JE, Katsamakis CD, RobinJ, et al. Effect of contrast enhancementon measurement of carotid artery in-timal medial thickness. Vasc Med2004;9:7–12.

3. Kono Y, Pinnell SP, Sirlin CB, et al.Carotid arteries: contrast-enhanced USangiography—preliminary clinical expe-rience. Radiology 2004;230:561–8.

4. Feinstein SB. The powerful micro-bubble: from bench to bedside, fromintravascular indicator to therapeuticdelivery system, and beyond. Am JPhysiol Heart Circ Physiol 2004;287:H450–7.

5. Vicenzini E, Giannoni MF, PuccinelliF, et al. Detection of carotid adventitialvasa vasorum and plaque vascularizationwith ultrasound cadence contrast pulsesequencing technique and echo-contrastagent. Stroke 2007;38:2841–3.

6. Papaioannou TG, Vavuranakis M, An-droulakis A, et al. In-vivo imaging ofcarotid plaque neoangiogenesis withcontrast-enhanced harmonic ultra-sound. Int J Cardiol 2009;134:e110–2.

7. Giannoni MF, Vicenzini E, Citone M,et al. Contrast carotid ultrasound for thedetection of unstable plaques with neo-angiogenesis: a pilot study. Eur J VascEndovasc Surg 2009;37:722–7.

8. Xiong L, Deng YB, Zhu Y, Liu YN,Bi XJ. Correlation of carotid plaqueneovascularization detected by usingcontrast-enhanced US with clinicalsymptoms. Radiology 2009;251:583–9.

9. Goertz DE, Frijlink ME, de Jong N,van der Steen AF. High frequencynonlinear scattering from a microme-ter to submicrometer sized lipid en-capsulated contrast agent. Ultrasound
Med Biol 2006;32:569–77.
Downloade

50. Carlier S, Kakadiaris IA, Dib N, et al.Vasa vasorum imaging: a new windowto the clinical detection of vulnerableatherosclerotic plaques. Curr Athero-scler Rep 2005;7:164–9.

51. Frijlink ME, Goertz DE, van DammeLC, Krams R, van der Steen AF.Intravascular ultrasound tissue har-monic imaging in vivo. IEEE TransUltrason Ferroelectr Freq Control2006;53:1844–52.

52. van der Steen AF, Baldewsing RA,Levent Degertekin F, et al. IVUSbeyond the horizon. EuroIntervention2006;2:132–42.

53. Goertz DE, Frijlink ME, Tempel D,et al. Contrast harmonic intravascularultrasound: a feasibility study for vasavasorum imaging. Invest Radiol 2006;41:631–8.

54. Goertz DE, Frijlink ME, Tempel D,et al. Subharmonic contrast intravas-cular ultrasound for vasa vasorum im-aging. Ultrasound Med Biol 2007;33:1859–72.

55. Van Mieghem CA, McFadden EP, deFeyter PJ, et al. Noninvasive detectionof subclinical coronary atherosclerosiscoupled with assessment of changes inplaque characteristics using novel in-vasive imaging modalities: the Inte-grated Biomarker and Imaging Study(IBIS). J Am Coll Cardiol 2006;47:1134–42.

56. Raman SV, Winner MW 3rd, TranT, et al. In vivo atherosclerotic plaquecharacterization using magnetic sus-ceptibility distinguishes symptom-producing plaques. J Am Coll CardiolImg 2008;1:49–57.

57. Choudhury RP, Fisher EA. Molecu-lar imaging in atherosclerosis, throm-bosis, and vascular inflammation. Ar-terioscler Thromb Vasc Biol 2009;29:983–91.

58. Piedra M, Allroggen A, Lindner JR.Molecular imaging with targeted con-trast ultrasound. Cerebrovasc Dis2009;27 Suppl 2:66–74.

59. Kerwin WS, Hooker A, Spilker M, etal. Quantitative magnetic resonanceimaging analysis of neovasculaturevolume in carotid atheroscleroticplaque. Circulation 2003;107:851–6.

60. Kerwin WS, Oikawa M, Yuan C,
Jarvik GP, Hatsukami TS. MR imag- m
by Stevenimaging.onlinejacc.orgd from

ing of adventitial vasa vasorum incarotid atherosclerosis. Magn ResonMed 2008;59:507–14.

1. Lombardo A, Rizzello V, Natale L, etal. Magnetic resonance imaging ofcarotid plaque inflammation in acutecoronary syndromes: a sign of multi-site plaque activation. Int J Cardiol2009;136:103–5.

2. Winter PM, Morawski AM, Caruth-ers SD, et al. Molecular imaging ofangiogenesis in early-stage atheroscle-rosis with alpha(v)beta3-integrin-targeted nanoparticles. Circulation2003;108:2270–4.

3. Winter PM, Neubauer AM, Caruth-ers SD, et al. Endothelial alpha(v)beta3 integrin-targeted fumagillinnanoparticles inhibit angiogenesis inatherosclerosis. Arterioscler ThrombVasc Biol 2006;26:2103–9.

4. Honda O, Sugiyama S, Kugiyama K,et al. Echolucent carotid plaques pre-dict future coronary events in patientswith coronary artery disease. J AmColl Cardiol 2004;43:1177–84.

5. Mathiesen EB, Bønaa KH, JoakimsenO. Echolucent plaques are associatedwith high risk of ischemic cerebrovas-cular events in carotid stenosis: theTromsø study. Circulation 2001;103:2171–5.

6. Koutouzis M, Nomikos A, Nikoli-dakis S, et al. Statin treated patientshave reduced intraplaque angiogenesisin carotid endarterectomy specimens.Atherosclerosis 2007;192:457–63.

7. Sinusas AJ. Targeted imaging offersadvantages over physiological imagingfor evaluation of angiogenic therapy.J Am Coll Cardiol Img 2008;1:511–4.

8. Barreiro O, Aguilar RJ, Tejera E, etal. Specific targeting of human in-flamed endothelium and in situ vascu-lar tissue transfection by the use ofultrasound contrast agents. J Am CollCardiol Img 2009;2:997–1005.

ey Words: vasa vasorum yontrast-enhanced ultrasound ytherosclerosis y surrogate
arker.


doi:10.1016/j.jcmg.2010.02.007 2010;3;761-771 J. Am. Coll. Cardiol. Img.

Sijbrands, Folkert J. ten Cate, and Steven B. Feinstein Steen, Jess D. Reed, Christian Krueger, Kai E. Thomenius, Dan Adam, Eric J.

Daniel Staub, Arend F.L. Schinkel, Blai Coll, Stefano Coli, Antonius F.W. van der Atherosclerosis to the Identification of Unstable Plaques

Contrast-Enhanced Ultrasound Imaging of the Vasa Vasorum: From Early

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