The American Journal of Medicine
Volume 122, Issue 1, Supplement , Pages S15-S25, January 2009

Diagnosis of Atherosclerosis by Imaging

  • Borja Ibañez, MD
    • ,
  • Juan J. Badimon, PhD
    • ,
  • Mario J. Garcia, MD

      Affiliations

    • Corresponding Author InformationRequests for reprints should be addressed to Mario J. Garcia, MD, Zena and Michael A. Wiener Cardiovascular Institute, Mount Sinai School of Medicine, One Gustave Levy Place, New York, New York 10029

Zena and Michael A. Wiener Cardiovascular Institute, Mount Sinai Hospital and School of Medicine, New York, New York, USA

Article Outline

Abstract 

New and experimental imaging techniques are being developed that will permit better visualization and compositional characterization of atheromatous plaques. This review provides discussion of techniques that are currently used in clinical practice, as well as techniques that are investigational only, including coronary angiography, intravascular ultrasound, computed tomography, magnetic resonance imaging, positron emission tomography, and single-photon emission computed tomography. Types of atheromatous plaque are reviewed, and the value of examining vascular calcification in risk assessment is discussed. Experimental use of these imaging techniques in animal models and in clinical studies will enhance our understanding of the development of plaque and will determine whether these techniques would be useful and practical for predicting disease course. Early detection and identification of the type of plaque that is present may generate novel opportunities for primary prevention through changes in lifestyle or even through drug therapy, especially in patients at high cardiovascular risk.

Keywords: Atherosclerosis, Cardiac magnetic resonance, Computed tomography, Vascular ultrasound

 

Atherosclerosis is a systemic process that can begin to develop as early as the second or third decade of life. Moreover, the lesions that provoke symptoms often are not stenotic and thus are not detectable by conventional contrast angiography. For this reason, the visualization and composition of the plaque are more important than the degree of stenosis. The ideal goal for imaging is to determine for individual patients their plaque burden as defined by the size, histology, chemical composition, and biological activity of plaque, with the use of quantitative measurements of lipid metabolism and of inflammation. The goal for imaging is similar to that for examination of plaque by pathologic techniques.

Over the past few years, great advances have been made in imaging techniques that enable visualization and characterization of atheromatous plaques, as well as monitoring of their progression or regression.1 Moreover, once atherosclerosis is detected in a single territory, given the diffuse nature of the disease, it can be assumed that other vascular territories are affected. Its early detection would generate novel opportunities for primary prevention through changes in lifestyle or even through drug therapy, especially in patients at high cardiovascular risk.

The purpose of this report is to briefly review established and newly developed imaging methods in terms of image generation, validation, applications in clinical research, and current use in clinical practice. Although outcomes are still lacking for many of these methods, most experts believe that imaging of atherosclerotic plaque will become increasingly useful, justified, and available to practitioners and their consultants for managing individual patients. The practitioner must therefore stay abreast of advances in plaque imaging that are increasing its usefulness.

A glossary of the terms used in this article is provided in Table 1.

Table 1. Glossary of terms
TermDefinition
Agatston calcium scoreThe Agatston technique involves measuring the total area of calcified coronary plaque in pixels, slice by slice, and assigning it a score. The Agatston calcium score is obtained by multiplying the area of the calcified lesion by a factor that depends on peak attenuation in the lesion.
AngiographyX-ray to visualize the lumen
Calcium score (also known as calcium volume score)With either EBCT or MDCT, calcium score is based on a radiographic density-weighted volume of plaques with pixel numbers of ≥130 HU.
Contrast microbubblesUltrasound contrast agents consisting of inert perfluorocarbon gases encapsulated in a biodegradable shell. Contrast microbubbles have a small diameter (<10 μm) that allows them to cross the pulmonary capillary bed. When exposed to ultrasound, these microbubbles act as strong reflectors produced by their liquid-gas interface. Interest has been growing in the potential application of contrast microbubbles for assessment of myocardial perfusion, delivery of therapeutic agents, and targeted imaging through molecular binding.
ABIAnkle brachial index
FDGFluorodeoxyglucose
IMTIntima-media thickness
IVUSIntravascular ultrasound
MIMyocardial infarction
MRIMagnetic resonance imaging
OCTOptical coherence tomography
PETPositron emission tomography
SPECTSingle-photon emission computed tomography

EBCT = electron beam computed tomography; HU = Hounsfield units; MDCT = multidetector computed tomography.

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Imaging methods 

Invasive Imaging 

Coronary Angiography 

Coronary angiography (Figure 1) was the first modality to become available for in vivo assessment of the coronary arteries. This procedure consists of injection of an iodinated contrast agent through a catheter placed at the ostium of the coronaries. The contrast agent is visible through x-ray fluoroscopic examination of the heart. Coronary angiography depicts “only” a luminogram of the vessel (the vessel space occupied by blood); the actual extent of atherosclerotic plaque volume in the wall cannot be assessed with this technique. Therefore, its usefulness is restricted to evaluation of concentric remodeling of the vessel and resultant luminal stenosis. Examples of coronary artery stenoses are indicated by arrows in Figure 1.

Intravascular Ultrasound 

Intravascular ultrasound (IVUS) is a catheter-based examination that, beyond depicting coronary luminal size, provides images of the thickness and the acoustic density of the entire vessel wall. Intracoronary ultrasound can depict the presence of atherosclerotic plaques not visible with contrast coronary angiography (Figure 2), and may reveal signs of recent disruption.2 Serial coronary ultrasound imaging studies, which can accurately reveal the volumetric extent of atheroma in a prespecified arterial segment at different times, have been used to assess the effects of various therapies.3, 4 IVUS has long been considered the “gold standard” for the study of the anatomy of the vessel wall and has also been applied to examine the composition of atherosclerotic lesions.5 IVUS allows one to discriminate with a moderate degree of accuracy plaque areas with calcium from those rich in lipids (soft plaques) and from fibrotic lesions.

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  • Figure 2. 

    Intravascular ultrasound (IVUS) obtained from the left anterior descending coronary artery in a patient with minimal obstructive disease by angiography. The yellow dashed line indicates the external elastic membrane of the vessel, and the blue dashed line indicates the lumen. The red arrow indicates the position of the catheter in the vessel lumen, and the yellow arrow shows an area of eccentric remodeling caused by noncalcified plaque.

A recently introduced IVUS-derived technique, palpography, provides information beyond that attained with classic IVUS. Palpography differentiates deformable from nondeformable tissue; this distinction potentially enables use of the technique for detecting “vulnerable plaques.” A second development of IVUS, called “virtual histology” IVUS, reveals different tissue types through spectral analysis of the radiofrequency of ultrasound backscatter signals.6, 7 Virtual histology IVUS has been shown to be more accurate than conventional IVUS in differentiating the various types of components of atherosclerotic plaque.7

Optical Coherence Tomography 

Optical coherence tomography (OCT) is a new catheter-based technology that produces high-resolution (10 to 15 μm vs. 120 to 150 μm with IVUS) images from backscattered reflections, similar to IVUS, but with the use of a high-bandwidth infrared light source instead of an ultrasound-emitting crystal. Major limitations include its attenuation by blood and its limited penetration in tissue. Although various approaches have been used to overcome these limitations,8 OCT may be most useful as a research tool.

Noninvasive Imaging 

Ultrasound 

High-frequency ultrasound transducers produce the high spatial resolution required to measure intima-media thickness (IMT) in vessel walls, the region that will show thickening with atherosclerotic plaque. However, higher frequency also limits depth of penetration into the body. Therefore, when surface ultrasound transducers are used, examination of vessels is limited to those that are close to the skin. Accordingly, ultrasound has been used primarily to evaluate the presence and burden of atherosclerotic plaque within the carotid arteries (Figure 3). In addition, contrast agents have been developed to further delineate the endovascular interphase. Recently, the clinical usefulness of carotid ultrasound as an adjunct in determining risk for future coronary events has been demonstrated, as has its use in predicting coronary disease.9, 10 Although there is controversy regarding the implementation of carotid IMT measurements in routine clinical practice, many experts recommend that it be used as a screening test in selected intermediate-risk populations.

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  • Figure 3. 

    Ultrasound obtained from (A) normal and (B) atherosclerotic carotid arteries. The layer indicated by the 2 parallel lines in A of the normal carotid artery is the intima-media thickness. The thick yellow arrow in B shows a large noncalcified plaque.

Computed Tomography 

Multidetector computed tomography (MDCT) technology recently has overcome many of the limitations of conventional computed tomography (CT) that prevented useful imaging of coronary vessels. Electrocardiogram (ECG)-gated image acquisition with short acquisition time, submillimeter spatial resolution, and adequate temporal resolution (50 to 220 msec) now can be provided, thus allowing excellent visualization of the coronary arteries.11 Moreover, the rate of technological advancement leading to improved coronary angiography with MDCT has rapidly exceeded that of electron-beam computed tomography (EBCT) and magnetic resonance imaging (MRI).12 Image quality is undergoing constant refinement, with 64-detector systems producing the highest proportion of interpretable coronary studies. X-ray attenuation may be used to characterize the composition of atherosclerotic plaque. Thus, calcified plaque appears as a bright, high-attenuation signal, whereas lipid-rich or fibrous plaque appears as hypoattenuated dark signals within the vessel wall. The relatively high radiation dose associated with MDCT is one limitation of this approach. However, in the near future, newer generations of CT scanners may reduce the required radiation exposure sufficiently to make this technology more attractive for screening asymptomatic patients.

Magnetic Resonance Imaging 

MRI is an example of promising technology that can be used to noninvasively gain information about blood vessel wall structure and composition. The rapidly spinning motion of positively charged protons produces a magnetic signal. Normally, the magnetic fields of protons are randomly oriented. When placed within an MRI scanner, however, protons within the body align themselves with the stronger external magnetic field of the scanner. Through application of specific radiofrequency waves, some of these protons change their alignment to a more excited state. As these protons relax and return to their original alignment, they give off a radiofrequency signal that can be measured by a receiver coil and used to generate a clinical image.

Because hydrogen (1H) is the most abundant atom in the body that is capable of generating a clinically useful image, 1H protons form the basis of clinical MRI. Pulse sequences are combinations of different types of radiofrequency pulses that are placed together to create images with specific characteristics. Combinations of different pulse sequences have been used for a variety of purposes in cardiovascular imaging13 and can be used to evaluate the composition of tissue (e.g., water vs fat). Paramagnetic contrast agents such as gadolinium and iron oxide derivatives may be targeted to specific tissues. Thus, MRI provides a unique opportunity for characterization of plaque composition.

Scintigraphic Techniques 

Targeted imaging through nuclear scintigraphic methods relies on administration of a radionuclide isotope that is accumulated by targeted tissue. Nuclear perfusion imaging is performed with the use of single-photon emission computed tomography (SPECT) or positron emission tomography (PET). The efficiency of PET is much greater, and the technique provides higher resolution, less noise, and lower radiation exposure than SPECT. In addition, PET can be used for the detection of positron emission of certain radionuclides, such as 18F-fluorodeoxyglucose (FDG), that accumulate in proportion to metabolic activity.14, 15 Thus, PET offers great potential for the visualization of atherosclerotic plaques.

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Noninvasive imaging of the anatomy and composition of atherosclerotic plaque 

Carotid Plaque 

B-mode ultrasound has been established as the imaging modality of choice for visualizing IMT. Abnormal thickening of carotid IMT is considered and has been validated as a marker of generalized atherosclerotic disease.16 In fact, it correlates linearly with the number of atherosclerotic risk factors.17 Arterial wall thickness can also be measured and the structure and composition of atheromatous plaques analyzed with the use of MRI and transthoracic or transesophageal ultrasound, among other techniques. An 8-MHz or a higher frequency ultrasound transducer can be used to measure this index in medium-sized to large arteries, such as the carotid, femoral, and radial arteries. This instrument also can be used to characterize the composition of atheromatous plaque on the basis of its echogenicity: a heterogeneous hypoechoic plaque (image from reflected signals is mottled and weak) is associated with the presence of lipids, whereas a homogeneous hyperechoic plaque (“bright”) is mainly fibrous.18 IMT measurement has proved to be a useful research technique when quality can be rigorously controlled and many patients are involved; however, it is less useful in a clinical setting for monitoring an individual patient.

In studies in which ultrasonographic measurements were compared with histologic findings, it has been shown that posterior (far) wall IMT of the carotid artery as measured with the use of ultrasound reflects the true thickness of the wall,19, 20 although measurements recorded with ultrasound may be slightly greater than estimates attained by histology. Values attained by measurement of the anterior (near) carotid wall are less accurate. In clinical trials, the measurement most frequently used is that of the common carotid artery21 because (1) this is the most reproducible approach, and (2) this technique has been shown to have a capability for predicting events similarly to more complex and complete methods. However, the combination of information from several different segments can enhance the accuracy of this index.

It must be kept in mind that IMT is a continuous variable, and that no clear upper cutoff value defines an atherosclerotic plaque. Normal carotid IMT has been established arbitrarily as approximately 0.5 to 1.1 mm; thus, values >1.1 mm are considered to indicate the presence of an atherosclerotic plaque. The use of this index as a vascular marker is based in part on the premise that carotid IMT >75th percentile for age indicates generalized atherosclerosis.22 Increased carotid IMT correlates with atherosclerosis in the abdominal aorta23 and in the arteries of the lower limbs24 and has been reported to be associated with increased left ventricular mass.25

Studies have shown that atherosclerosis in the carotid artery and in the aorta is a marker of coronary atherosclerosis.26 Patients with symptomatic coronary artery disease have increased carotid IMT when compared with asymptomatic controls.27 Although a relation between carotid IMT and severity of coronary artery disease has been noted, this association is weak.28 Carotid IMT may be useful as a marker of disease progression, as has been seen in prospective epidemiologic studies.16 The Cardiovascular Health Study of patients aged >65 years found that an increase in IMT increased the relative risk of acute coronary syndromes or acute stroke.29 Future prevention trials involving lipid-lowering treatments may show that a decrease in IMT may be associated with a reduction in the incidence of cardiovascular events.30 Given that the value correlates well with atherosclerosis, measurement of IMT of the carotid artery can serve as a good method for studies conducted to monitor the effects of treatment on progression/regression of carotid atherosclerosis.31, 32, 33

MRI, which has been used for evaluation of the carotid vessels, makes it possible not only to quantify the size of the atherosclerotic plaque but also to assess intraplaque hemorrhage and the integrity of the fibrous cap.34, 35 A close association has been observed between thinning or rupture of the fibrous cap of the carotid plaque as detected by MRI and a recent history of transient ischemic attack (TIA) or acute stroke.35 It is technically possible to combine magnetic resonance angiography (quantification of degree of stenosis and its spatial distribution) with high-resolution MRI (characterization of the arterial wall and the composition of plaque)36, 37 (Figure 4).

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  • Figure 4. 

    Magnetic resonance angiogram in an asymptomatic patient with atherosclerosis. (A) Contrast-enhanced angiogram shows bilateral common carotid artery stenosis (arrows). (B) Black blood cross-sectional image reveals atherosclerotic plaques in the left external and internal carotid arteries (arrows).

Aortic Plaque 

Atheromatous plaque in the thoracic aorta may be evaluated with the use of high-resolution (submillimeter spatial resolution) MRI or transesophageal echocardiography. MRI is more reliable than transesophageal ultrasound with respect to characterization of plaque, although findings with both techniques have been shown to have a strong correlation in terms of plaque thickness.38 In a study conducted in rabbits, contrast-enhanced magnetic resonance angiography of the thoracoabdominal aorta and its branches provided spatial information on the distribution of plaques and on renal artery involvement.1 In a study of 21 asymptomatic patients with hypercholesterolemia, serial MRI images demonstrated significant regression of aortic and carotid artery plaques in association with lipid-lowering therapy.39 Preliminary results suggest that MRI may prove to be an ideal tool for monitoring plaque regression after lipid-lowering treatment has been initiated (Figure 5).39, 40, 41, 42

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  • Figure 5. 

    Magnetic resonance cross-sectional images at the same level of the aorta in a patient treated with 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins). The similar pattern of the coronary vessels at each time indicates that the images were well matched. The aorta is indicated by yellow arrows in the top row. In the detailed view of the descending aorta (bottom row), arrows indicate maximal atherosclerotic plaque size. Note that after 6 months of treatment, the plaque volume is similar, revealing a halt in plaque progression. At 12 months, plaque volume shrinkage is seen. (Reprinted with permission from Circulation.42)

Coronary Atherosclerosis 

Coronary Calcification 

Some atherosclerotic plaques develop calcified nodules (see Figure 3 on atherosclerotic progression in the article by Insull in this supplement43) that can be detected by noninvasive imaging. In epidemiologic studies, coronary artery calcification was associated with a higher risk for myocardial infarction (MI), even in patients with asymptomatic disease.44 Assessment of coronary calcium burden through noninvasive CT techniques provides a useful marker for coronary artery disease. Growing evidence suggests that measurement of coronary calcium may be particularly valuable in therapy decisions for patients at intermediate risk for coronary events.45 Recently, MDCT has been shown to provide reproducible results that are comparable to those attained by EBCT calcium scoring.45, 46

With both scanners, the most widely used measure of calcium burden is the Agatston calcium score.44 Very high calcium scores impart increased cardiovascular risk, even though they do not always imply a tight coronary stenosis.44 In patients with intermediate risk based on clinical factors, but not those at low risk, a calcium score >300 significantly increased the rate of MI or coronary death.44 A coronary calcium Agatston score >100 was an independent predictor (odds ratio = 1.88) of death and nonfatal MI at 7 years' follow-up.47

The fifth conference on the prevention of cardiovascular disease (Prevention V) sponsored by the American Heart Association (AHA)48 addressed the use of the calcium score and other noninvasive tests in selected populations of asymptomatic patients. The use of the calcium score has been recognized by the National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III).49 For example, asymptomatic patients at intermediate risk (10-year risk of 10% to 20% and ≥2 coronary risk factors according to the Framingham criteria) constitute the group that could benefit the most from changes in treatment and lifestyle; thus, in this group, the quantification of calcium score would be indicated most clearly. Calcium scoring also may be useful in patients who cannot undergo traditional noninvasive testing (e.g., treadmill exercise, stress test) because of physical or medical restrictions50 and in certain low-risk subgroups, such as young patients with a family history of early-onset ischemic heart disease.51

The value of screening asymptomatic individuals as part of a comprehensive assessment based on clinical risk factors and serum biomarkers has been debated.52 Some authors argue that the combination of calcium score with conventional risk factors would provide a better approach to estimating risk in asymptomatic patients.53 Moreover, in those patients with cardiovascular risk factors and a high calcium score, stress perfusion imaging or ventricular function testing can provide diagnostic and prognostic information.54 Nonetheless, recent data suggest that serial monitoring of the calcium score to observe the progression or regression of atherosclerosis is of questionable utility.39, 55

Noncalcified Plaque Burden 

Observational studies have shown an association between noncalcified coronary plaques and high cholesterol levels and other risk factors, including the presence of diabetes mellitus56, 57; lipid-lowering therapy has been shown to reduce noncalcified plaque burden.58 Assessment of noncalcified plaque burden may be useful in risk stratification for certain patients.56 Until recently, IVUS was the only diagnostic tool capable of detecting the presence, extent, and composition of noncalcified atherosclerotic plaques in the coronary arteries in vivo.53, 59 The wide application of IVUS as a screening tool for risk assessment is impractical because of the need for and high cost of invasive catheterization. MDCT angiography is an alternative method of imaging the vessel wall that may be used in addition to visualization of the lumen of coronary arteries. Recent studies have documented the ability of MDCT to facilitate visualization of atherosclerotic coronary plaques and differentiation of calcified from noncalcified lesions (Figure 6).11, 60, 61, 62 Whether MDCT could be used in clinical practice as a screening test remains to be proved, but in selected patients at low to intermediate risk, it could help to justify lifelong aggressive preventive intervention. MDCT plaque characterization can guide researchers in devising optimal revascularization strategies.

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  • Figure 6. 

    (A) Multidetector computed tomography (MDCT) axial image obtained from an asymptomatic patient shows mild narrowing of the proximal left anterior descending coronary artery caused by a noncalcified plaque (arrow). (B) MDCT oblique axial image obtained from a patient with atypical chest pain reveals eccentric calcified plaques (arrow) with mild stenosis of the proximal left anterior descending coronary artery.

Cardiac CT is similar to invasive angiography in that it requires radiation exposure. The “effective dose,” expressed in milliSieverts (mSv), depends on multiple factors, including the physical extent, duration, and radiation intensity of the scan. Acquiring adequate images in obese individuals requires larger amounts of radiation energy because of scattering and attenuation. The latest 64-detector MDCT coronary angiography systems provide a dose of about 8 to 14 mSv. This compares with 2 to 6 mSv for invasive angiography, 15 to 25 mSv for nuclear stress myocardial perfusion studies, and 3.6 mSv for yearly background radiation exposure. Thus, long-term risks associated with radiation as opposed to the potential benefits derived should be taken into consideration, particularly in younger individuals who are at higher risk.

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Functional and molecular imaging through noninvasive methods: Future modalities 

New techniques based on molecular imaging that are currently under development may make it possible for the clinician to visualize inflammatory and other activities of atheromatous plaque. Such techniques would greatly enhance our ability to understand and assess mechanisms of the atherosclerotic disease process and monitor the efficacy of treatment. Several techniques with sufficient spatial resolution have been developed to facilitate molecular imaging; these include MRI with targeted contrast agents, ultrasound with contrast microbubbles, optical imaging techniques (fluorescent and bioluminescent), and nuclear medicine techniques (PET and SPECT).

Molecular imaging can be considered an in vivo equivalent to immunohistochemical techniques. The goal of this technique is to identify specific molecules and cells with the use of a radiolabeled marker as the contrast agent. This contrast agent must have high specificity and an isotope signal intense enough to be detected and differentiated from unlabeled zones.37 Results of a recent study showed that macrophages present in atherosclerotic plaques of animals can be detected with a 64-slice CT scanner after intravenous injection of an iodinated contrast agent that specifically binds these cells.63

Inflammatory Activity 

Inflammation is an important component of atherosclerotic disease progression, but it is not as easily visualized as wall thickening or lipid accumulation. New methods, for example, the use of FDG, show great promise for visualization of vascular inflammation. In addition to several reports on research in animals, a recent study in humans involving FDG-PET suggested that macrophages were responsible for FDG uptake.14

Recently, FDG/PET-CT was shown to be highly reproducible in assessing the degree of FDG uptake within the vessel wall.15 Aortic uptake of FDG was reduced after treatment with a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor (statin) in asymptomatic patients undergoing cancer screening.64 This suggested a reduction in atherosclerotic plaque inflammation with statin treatment. FDG/PET-CT technology offers a promising technique for monitoring serial changes in plaque inflammation. However, a major drawback of this modality is the still relatively low spatial resolution of PET, which limits its use in coronary arteries. In animal models, MRI with contrast agents targeted against antigens present during inflammatory processes has been used to demonstrate inflammatory activity in atherosclerotic plaque.65, 66, 67, 68

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Current trials to test the broad clinical usefulness of vascular imaging 

The Multi-Ethnic Study of Atherosclerosis (MESA) enrolled (between July 2000 and August 2002) a total of 6,814 men and women aged 45 to 84 years of diverse ethnic origin who were free of clinically apparent cardiovascular disease.69 Baseline data obtained included measurements of the following: coronary calcium by CT; ventricular mass and function by MRI; and flow-mediated brachial artery endothelial vasodilation, carotid IMT, and peripheral vascular disease assessed by means of ankle-brachial index (ABI) blood pressures. Standard cardiovascular disease risk factors and serum biomarkers also were assessed. Follow-up is expected to be completed by the end of 2008. The High-Risk Plaque (HRP) BioImage study will enroll >6,000 asymptomatic patients at intermediate cardiovascular risk whose carotid IMT measurements and calcium score will be assessed by CT and ABI testing.70 A subset of these patients will undergo contrast-enhanced CT coronary angiography, carotid and aortic MRI, and PET-FDG. Clinical events will be followed over 3 years to determine the predictive usefulness of these imaging tests. The authors anticipate that the outcomes of these studies will guide clinicians in identifying the populations for whom screening by imaging is most clinically useful and cost-effective.

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Summary 

Atherosclerosis plaque imaging represents a new paradigm in cardiovascular medicine. At a research level, plaque imaging is a powerful tool for evaluating the mechanisms and efficacy of novel drug therapies. At a clinical level, plaque imaging may help clinicians to identify patients at risk who may benefit from secondary prevention strategies. The specific roles of different imaging modalities must be clearly defined. Significant evidence supports the role of the calcium score scan as a screening test in patients at intermediate clinical risk. Several ongoing studies are addressing whether other imaging modalities will have a role in clinical practice.

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Pearls for clinical guidance 


•Common characteristics of atherosclerotic plaques may be determined noninvasively.

•Carotid ultrasound provides a measurement of IMT, which has been related to cardiovascular events and risk factors.

•MRI can reveal total plaque burden across different vascular beds. Resolution most often is limited to large-caliber vessels.

•CT can be used to determine coronary plaque burden and type. In contrast to MRI and ultrasound, this technique requires ionizing radiation.

•Molecular imaging with MRI and/or PET may reveal inflammatory activity in atherosclerotic plaques.

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Author disclosures 

The authors who contributed to this article have disclosed the following industry relationships:

Borja Ibañez, MD, has no financial arrangement or affiliation with a corporate organization or a manufacturer of a product discussed in this article.

Juan J. Badimon, PhD, has served as an advisory board participant (honorarium) for AstraZeneca Pharmaceuticals LP, Lilly-Sankyo, Pfizer Inc, and sanofi aventis.

Mario J. Garcia, MD, is a consultant for Philips Medical Systems and BG Medicine and has received honoraria from Abbott Laboratories and AstraZeneca Pharmaceuticals LP.

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Acknowledgments 

We thank Michael Theisen, Dolores Matthews, and Marsha Hall from Scientific Connexions, Newtown, Pennsylvania, who provided editorial assistance funded by AstraZeneca Pharmaceuticals LP.

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Supplementary data 

Supplementary material cited in this article is available online.

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Supplementary data 

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PII: S0002-9343(08)01018-8

doi:10.1016/j.amjmed.2008.10.014

The American Journal of Medicine
Volume 122, Issue 1, Supplement , Pages S15-S25, January 2009

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