This document addresses use of electron beam computed tomography (EBCT), helical CT and multi-slice spiral CT scanning to detect coronary artery calcium (CAC).  The rapid image acquisition time of these CT scanning techniques eliminates motion artifact related to the beating heart and thus, permits visualization of coronary artery calcium.  In asymptomatic individuals, CAC has been investigated as a risk factor for coronary artery disease and has been used to further evaluate individuals with known coronary artery disease.    

Note: This document only addresses CT detection of CAC.  Assessment of CAC may also be done in conjunction with CT scanning to visualize the coronary arteries, (referred to as CT angiography, or CCTA).  CCTA is addressed in RAD.00035 Coronary Artery Imaging: Contrast-Enhanced Coronary Computed Tomography Angiography (CCTA) and Coronary Magnetic Resonance Angiography (MRA).

Investigational and Not Medically Necessary:

The use of electron beam computed tomography (EBCT), helical CT or multi-slice spiral (also known as multi-row detector) CT (MSCT) is considered investigational and not medically necessary for the detection of coronary artery calcium, including, but not limited to, the following indications:

• as part of a cardiac risk assessment in asymptomatic or symptomatic individuals;
• as a diagnostic test in individuals considered at intermediate risk for coronary artery disease, where other cardiac tests have been inconclusive;
• as a diagnostic test in symptomatic individuals;
• in conjunction with a coronary CT angiography (CCTA).

General Considerations:
Diagnostic technologies are commonly evaluated according to a sequential three step assessment of analytic validity, clinical validity and clinical utility.  Analytic validity refers to the ability of a CT scan to accurately and reliably detect coronary artery calcium (CAC).  The data is typically reported as a "calcium score," which represents the total atherosclerotic plaque burden.  Clinical validity refers to the relationship between the detected CAC and coronary artery disease (CAD).  Finally, clinical utility refers to how CAC scores can be used to improve treatment management of CAD. 

While it is recognized that electron beam or helical CT scans can detect and quantify CAC, the major questions regarding these techniques relate to clinical validity and utility.  For example, in the United States cardiac risk assessment is currently based on the Framingham Risk Score (FRS), which is used as the basis for various prevention strategies for CAD.  The FRS is derived from various, easily obtained, clinical and laboratory values, such as age, lipid profile, blood pressure and smoking status.  Therefore, a key question is whether an assessment of CAC will improve these traditional risk assessment techniques.  Additionally, it is important to understand how CAC risk assessment will be integrated into overall treatment management, particularly in those who are considered at intermediate risk.  For example, epidemiologic and observational studies may demonstrate that CAC is an independent risk factor for CAD, but improved risk assessment is not clinically meaningful if this information cannot be used to improve treatment management. 

CAC has also been used to evaluate symptomatic individuals as an initial test to guide further cardiac function or imaging tests, based on the calcium score.  For example, a low calcium score may be used to rule out CAD in symptomatic individuals, potentially deselecting these people for angiography.  Again, in this setting it is important to understand how measurement of CAC will be integrated into the management of the individual, particularly given the wide variety available of noninvasive diagnostic techniques, ranging from different types of exercise tests, echocardiography and nuclear medicine tests. 

The following discussion is based primarily on review of a variety of consensus documents, scientific statements and guidelines addressing the clinical validity and clinical utility of CT detection of CAC.       

Consensus Reports, Guidelines and Scientific Statements:
In 2000, an American College of Cardiology/American Heart Association Expert Consensus paper stated that EBCT measurement of coronary artery calcium is not recommended for diagnosing obstructive CAD, because of the imaging device's low specificity (high percentage of false-positive results) or for screening of asymptomatic individuals, because of the lack of incremental value in EBCT screening over other readily available risk assessment methods (O'Rourke, 2000).

In 2004, the United States Preventive Services Task Force (USPSTF) issued updated recommendations on screening asymptomatic adults for coronary heart disease (CHD, also known as CAD) seen in primary care settings.  The USPSTF gave a "D"* recommendation against routine screening with EBCT scanning for CAC, for either the presence of severe coronary artery stenosis or the prediction of CHD events in adults at low risk for CHD.

This recommendation was supported by at least fair evidence that screening asymptomatic adults for CHD is ineffective or that harms outweigh benefits.  The USPSTF gave an "I"** recommendation to support or reject EBCT scanning for CAC for either the presence of severe coronary artery stenosis or the prediction of CHD events, in adults at increased risk for CHD events.  This recommendation was based on insufficient evidence to recommend for or against routinely providing screening services in this adult population (USPSTF, Feb 2004; see the Definitions section for an explanation of the rating system).

In 2005, the American Heart Association published a consensus statement regarding the role of noninvasive testing of women with suspected CAD (Mieres, 2006).  The consensus statement considered the incremental value of CAC scores, compared to traditional risk factor assessment, and focused on one observational study that included a large number of women.  The report concluded that additional studies were needed to establish female-specific cut points of CAC scores defining high risk status in women.  The consensus statement offered the following conclusion:

Additional high-quality data are needed from larger cohorts that specifically address CAD outcomes in women to more precisely establish female specific CAC risk cut points and to more precisely quantify the incremental prognostic value beyond the measurement of conventional coronary risk factors.  Until then, consistent with recent consensus statements, CAC testing for CAD risk detection should be limited to clinically selected women at intermediate risk.  

In 2006, the American College of Cardiology Foundation Quality Strategic Directions Committee Appropriateness Criteria Working Group published appropriateness criteria for cardiac computed tomography, including evaluation of CAC (Hendel, 2006).  This report took a consensus approach to the evaluation of test performance of these technologies within specific clinical scenarios. A total of four CT indications addressing CAC were rated as follows:

For risk assessment in the general population of asymptomatic individuals, CAC measurements were rated:

• Inappropriate for low CHD risk (on FRS scoring);
• Uncertain for moderate CHD risk (on FRS);
• Uncertain for high CHD risk (FRS).   

For risk assessment with prior test results when patient is asymptomatic, CAC measurements were rated:

• Inappropriate if prior calcium score was within the previous 5 years.

In 2006, the American Heart Association published a scientific statement on the assessment of CAD by cardiac computed tomography (Budoff, 2006).  Most of the document reviewed the clinical utility of CAC scoring for determining prognosis and diagnosis.  Within this document, there were no Class I* or IIa** recommendations regarding coronary artery calcium detection by CT.  The following IIb recommendations were offered:

• Patients with equivocal or normal EKG and negative cardiac enzymes;
• Determination of the etiology of cardiomyopathy;
• Symptomatic patients with equivocal results of treadmill or functional tests;
• Asymptomatic patients with intermediate (10-20%) risk of CAD.

A 2007 clinical consensus document co-written by the American College of Cardiology Foundation and the American Heart Association provided updated information on CAC measurement (Greenland, 2007).  This document notes that Clinical Expert Consensus Documents concern topics for which, "The evidence base, the experience with the technology and/or the clinical practice are not considered sufficiently well developed to be evaluated by the formal American College of Cardiology/American Heart Association (ACC/AHA) Guidelines process.  Often the topic is the subject of considerable ongoing investigation."  Therefore, this document acknowledged the lack of rigorous evidence addressing the clinical utility of CAC measurement.       

The findings of this expert panel were consistent with the prior AHA scientific statement (Budoff, 2006), in that the Committee judged that it may be reasonable to consider use of CAC measurement in asymptomatic individuals with intermediate CHD risk.  This was based on the possibility that such persons might be reclassified to a higher risk status if high CAC scores are found, thereby subsequent treatment management may be modified.  However, there was inadequate data to show that changes in management result in improved health outcome.  The Committee did not recommend use of CAC measurement in other selected groups, such as those with low or high CHD risk (based on the FRS).  However, this paper noted, "In general, CAC measurement has not been compared to alternative approaches to risk assessment in head-to-head studies.  Therefore, the question of whether there is evidence that CAC measurement is better than other potentially competing tests for intermediate risk patients for modifying cardiovascular disease risk estimate cannot be adequately answered from the available data."

The USPSTF issued another recommendation statement on using nontraditional risk factors in CHD risk assessment in 2009 which concluded that, "The current evidence is insufficient to assess the balance of benefits and harms of using the nontraditional risk factors discussed in this statement to screen asymptomatic men and women with no history of CHD to prevent CHD events." (Grade: I [Insufficient] Statement, current evidence is insufficient to assess the balance of benefits and harms of the service. Evidence is lacking, of poor quality, or conflicting, and the balance of benefits and harms cannot be determined.)

The nontraditional risk factors included in this recommendation are high-sensitivity C-reactive protein (hs-CRP), ankle–brachial index (ABI), leukocyte count, fasting blood glucose level, periodontal disease, carotid intima–media thickness (carotid IMT), coronary artery calcification (CAC) score on electron-beam computed tomography (EBCT), homocysteine level, and lipoprotein(a) level.

Conclusions:
The 2006 AHA scientific statement noted that there is growing evidence that CAC scores are an independent predictor of CAD, (i.e., proof of clinical validity).  However, it is still unknown how this information can be integrated into treatment management to improve health outcomes, (i.e., clinical utility).  This gap in the data is reflected by the consensus, rather than evidence-based, approach in developing recommendations and appropriateness criteria (Budoff, 2006).

Clinical Studies:
A literature search focused on studies published since the 2005 review period noted in the 2007 clinical consensus document (Greenland, 2007).  While these studies have further assessed CAC as a risk assessment tool, there are still no studies detailing how this information can be used to improve treatment management.  Representative studies are reviewed below.

In 2006, Anand and colleagues published a study specifically evaluating CAC scores as a risk stratification tool in 510 subjects with uncomplicated type II diabetes (Anand, 2006).  Myocardial perfusion studies were performed in all subjects with high CAC scores and in a random sample of the remaining subjects.  The trial participants were followed for a mean of 2.2 years for cardiovascular events.  The authors reported that CAC scores were superior to established cardiovascular risk factors for predicting silent myocardial ischemia and short-term outcome.  It should be noted that the CAC scores were not used to direct treatment management.

The MESA Trial (Multi-Ethnic Study of Atherosclerosis) is an ongoing, multi-center, prospective longitudinal study of asymptomatic individuals across four racial/ethnic groups to evaluate the long-term cardiovascular outcomes with a ten year follow-up of 6,772 asymptomatic participants after baseline risk assessment (including CAC measurement).  The MESA study was launched in 2000.

Interim results (median follow-up 3.9 years) suggest that the coronary artery calcium score is a predictor of subsequent clinically significant CHD and may provide predictive information beyond that provided by standard risk factors, (i.e., the FRS). (Detrano, 2008)  The authors reported that after adjustment for standard risk factors, a doubling of the CAC score resulted in a 20% increase in the risk of a major coronary event (myocardial infarction/death from CHD) and a 25% increase in the risk of any coronary event.  A limitation of this study was variation in CT acquisition and reading methods across the six study centers.  The authors also caution against using the absolute calcium scores cited in the study and note that ethnic-specific calibrations of CAC scores are needed to adjust for baseline differences between different ethnic groups.  Another limitation of this interim report is the small number of measured clinical events (72 non-fatal MI, 17 fatal coronary events, 73 angina pectoris).

The data, collected thus far, from the MESA Trial have been studied and reported in multiple published articles, one of which was conducted by Lakoski and colleagues who looked at CAC scores and risk of future coronary events in women.  This MESA cohort study included 3,601 asymptomatic women, age 45 to 84 years, and judged to be at low risk for coronary disease based on FRS.  The authors concluded that the presence of coronary artery calcium in women at low FRS risk was predictive of future CHD and cardiovascular events.  Compared with women with no detectable coronary artery calcium, low risk women with a CAC score greater than 0 were at increased risk for CHD (HR 6.5, 95%; CI 2.6-16.4) and cardiovascular events (HR 5.2, 95%; CI 2.5-10.8).  Low risk women with advanced coronary artery calcium (CAC score ≥ 300) had a risk of 8.6% for having a cardiovascular event over a 3.75 year period, compared with 0.6% in low risk women with CAC score of 0 and 1.9% in low risk women with CAC score 1-99.

Another recent publication reported on a cohort of 5,878 asymptomatic subjects taken from the MESA population with a median follow-up of 5.8 years.  Analysis of risk for coronary events was conducted comparing use of the conventional FRS System alone to inclusion of CAC scores, as part of the risk stratification model.  With the addition of CAC to the model, an additional 23% of those who experienced events were reclassified as high risk, and an additional 13% who did not experience events were reclassified as low risk. In total, only 5.1% of the total MESA population was reclassified as a result of CAC scores. Limitations of this study include the need for validation of the results in broader trial populations.  The authors acknowledge that higher event rates and different rates of reclassification may have been seen if the study population contained a larger proportion of higher risk individuals.  Trial results may have changed with longer follow-up; also the fact that all CAC scores were revealed to both participants and their treating physicians may have impacted the five-year results seen in this trial (Polonsky, 2010).   

Budoff and colleagues used a large observational data base of 25,253 asymptomatic patients undergoing CAC scoring to develop risk-adjusted multivariable models incorporating CAC scores to predict all cause mortality (Budoff, 2007).  The authors reported that the CAC score provided incremental information, in addition to traditional risk factors in the prediction of all-cause mortality.

Conclusions:
The role of CAC scoring, particularly for determining its incremental value for risk stratification in those with intermediate FRS, continues to be studied.  Although observational studies suggest that CAC scores may predict risk for future coronary events, there is insufficient evidence in the literature, to date, to demonstrate how screening with CAC will impact treatment management and clinical outcomes (Bonow, 2009).  Also, the evidence continues to show variability in the accuracy of test results from various CT scanners, as well as ongoing concerns about the variable amounts of radiation exposure delivered by these scans (Gibbons, 2009; Gerber, 2009; Bluemke, 2008; Kramer, 2007; Budoff, 2006). 

Note:
The presence of extensive coronary artery calcium precludes the use of CT coronary angiogram (CCTA).  Therefore, an assessment of CAC is often performed in combination with CCTA.  Many of the recently published studies of CAC explore its role in conjunction with CCTA.  These studies are not considered in this document.  CCTA is considered separately in RAD.00035.

Computerized axial tomography, also called CT, CT scan, or CAT scan, is an x-ray technique that uses an x-ray-sensing unit which rotates around the body, along with a computer to create cross-sectional images.  The images are generated by a computer synthesis of x-ray transmission data obtained for many different directions in a given plane.  Electron beam CT and spiral or helical CT scans are types of CT scans that have very high speeds of image acquisition which eliminate the motion artifact of the beating heart, and thus, permit imaging of coronary artery calcium.  Since CAD may remain silent until a major catastrophic event occurs, it has been hypothesized that detection of coronary calcium in asymptomatic individuals could provide additional data on cardiac risk; this could potentially lead to changes in diet, lifestyle, and treatment management.  It is thought that these changes could potentially reduce the risk of myocardial infarction (MI).

Computed tomography (CT): an imaging technique that creates multiple cross-sectional images of the body by using special X-rays and computer enhancement to detect disease or abnormalities

Coronary artery disease: a disease characterized by narrowing or blockage of the blood vessels that supply blood to the heart

Electron beam CT (also known as Ultrafast CT): is a type of CT that uses an electron gun rather than a standard x-ray tube to generate x-rays, thus permitting very rapid scanning, on the order of 50-100 milliseconds per image

Framingham Risk Scoring System (FRS): the most-commonly used, multi-variable scoring system (in the U.S.) and the most extensively validated quantitative assessment tool for determining an individual's potential risk of developing CHD and of experiencing a significant coronary event; it includes the following major risk factors: gender, total cholesterol, high-density lipoprotein (HDL) cholesterol, systolic blood pressure (or on treatment for hypertension), cigarette smoking, and age

Helical CT (also known as spiral CT scanning): is a type of CT that creates images at greater speed than conventional CT by continuously rotating a standard x-ray tube around the individual so that data are gathered in a continuous spiral or helix rather than individual slices

Multislice spiral CT (MSCT) (also known as multi-row detector CT or MDCT): is a technical evolution of helical CT, and uses CT machines equipped with an array of multiple x-ray detectors that can simultaneously image multiple sections during a rapid volumetric image acquisition; currently available MDCT machines may have 4, 8, 16, 32, 40 or 64 detectors

Tomograph: an apparatus for moving an x-ray source in one direction as the film is moved in the opposite direction, thus showing in detail a predetermined plane of tissue while blurring or eliminating detail in other planes

Note: According to the USPSTF Task Force ratings on strength of recommendations, the U.S. Preventive Services Task Force (USPSTF) grades its recommendations according to one of five classifications (A, B, C, D, I) reflecting the strength of evidence and magnitude of net benefit (benefits minus harms) as follows:

A.— The USPSTF strongly recommends that clinicians provide [the service] to eligible patients. The USPSTF found good evidence that [the service] improves important health outcomes and concludes that benefits substantially outweigh harms.
B.— The USPSTF recommends that clinicians provide [this service] to eligible patients. The USPSTF found at least fair evidence that [the service] improves important health outcomes and concludes that benefits outweigh harms.
C.— The USPSTF makes no recommendation for or against routine provision of [the service]. The USPSTF found at least fair evidence that [the service] can improve health outcomes but concludes that the balance of benefits and harms is too close to justify a general recommendation.
*D.— The USPSTF recommends against routinely providing [the service] to asymptomatic patients. The USPSTF found at least fair evidence that [the service] is ineffective or that harms outweigh benefits.
**I.— The USPSTF concludes that the evidence is insufficient to recommend for or against routinely providing [the service]. Evidence that the [service] is effective is lacking, of poor quality, or conflicting and the balance of benefits and harms cannot be determined. (USPSTF, 2004)

According to the American College of Cardiology/American Heart Association/European Society of Cardiology (ACC/AHA/ESC) guideline recommendations documents, the following are the definitions of Classifications of Recommendations, as expressed in the ACC/AHA/ESC format:

*Class I: Conditions for which there is evidence and/or general agreement that a given procedure or treatment is beneficial, useful, and effective.
Class II: Conditions for which there is conflicting evidence and/or divergence of opinion about the usefulness/efficacy of a procedure or treatment.
**Class IIa: Weight of evidence/opinion is in favor of usefulness/efficacy.
***Class IIb: Usefulness/efficacy is less well established by evidence/opinion.
Class III: Conditions for which there is evidence and/or general agreement that a procedure/treatment is not useful/effective and in some cases may be harmful.  (Hendel, 2006)

The following codes for treatments and procedures applicable to this document are included below for informational purposes.  Inclusion or exclusion of a procedure, diagnosis or device code(s) does not constitute or imply member coverage or provider reimbursement policy. Please refer to the member's contract benefits in effect at the time of service to determine coverage or non-coverage of these services as it applies to an individual member.

When services are Investigational and Not Medically Necessary:

When services are also Investigational and Not Medically Necessary:

Peer Reviewed Publications:

1. Anand DV, Lim E, Hopkins D, et al.  Risk stratification in uncomplicated type 2 diabetes: prospective evaluation of the combined use of coronary artery calcium imaging and selective myocardial perfusion scintigraphy.  Eur Heart J. 2006; 27(6):713-721.
2. Arad Y, Goodman KJ, Roth M, et al. Coronary calcification, coronary disease risk factors, C-reactive protein, and atherosclerotic cardiovascular disease events: the St. Francis Heart Study. J Am Coll Cardiol. 2005; 46:158-165.
3. Arad Y, Spadaro LA, Roth M, Newstein D, Guerci AD. Treatment of asymptomatic adults with elevated coronary calcium scores with atorvastatin, vitamin C, and vitamin E: the St. Francis Heart Study randomized clinical trial. J Am Coll Cardiol. 2005; 46:166-172.
4. Becker A, Leber AW, Becker C, et al. Predictive value of coronary calcifications for future cardiac events in asymptomatic patients with diabetes mellitus: a prospective study in 716 patients over 8 years. BMC Cardiovasc Disord. 2008; 8:(27).
5. Bild DE, Detrano R, Peterson D, et al. Ethnic differences in coronary calcification: the Multi-Ethnic Study of Atherosclerosis (MESA). Circulation. 2005; 111:1313-1320.
6. Bild DE, Folsom AR, Lowe LP, et al. Prevalence and correlates of coronary calcification in black and white young adults: the Coronary Artery Risk Development in Young Adults (CARDIA) Study. Arterioscler Thromb Vasc Biol. 2001; 21:852-857.
7. Blumenthal RS, Becker DM, Yanek LR, et al. Comparison of coronary calcium and stress myocardial perfusion imaging in apparently healthy siblings of individuals with premature coronary artery disease. Am J Cardiol. 2006; 97(3):328-333.
8. Bonow RO. Should coronary calcium screening be used in cardiovascular prevention strategies. N Engl J Med. 2009; 361:990-997.
9. Budoff MJ, Shaw LJ, Liu ST, et al. Long-term prognosis associated with coronary calcification: observations from a registry of 25,253 patients. J Am Coll Cardiol. 2007; 49(18):1860-1870.
10. Budoff MJ, Nasir K, McClelland RL, et al. Coronary calcium predicts events better with absolute calcium scores than age-sex-race/ethnicity percentiles: MESA (Multi-Ethnic Study of Atherosclerosis). J Am Coll Cardiol. 2009; 53:345-352.
11. Budoff MJ, McClelland RL, Nasir K, et al. Cardiovascular events with absent or minimal coronary calcification: the Multi-Ethnic Study of Atherosclerosis (MESA).  Am Heart J. 2009; 158(4):554-561.
12. Chang SM, Nabi F, Xu J, et al.  The coronary artery calcium score and stress myocardial perfusion imaging provide independent and complementary prediction of cardiac risk. J Am Coll Cardiol. 2009; 54(20):1872-1882.
13. Detrano R, Guerci AD, Carr JJ, et al. Coronary calcium as a predictor of coronary events in four racial or ethnic groups. N Engl J Med. 2008; 358(13):1336-1345.
14. Dewey M, Vavere AL, Arbab-Zadeh A, et al. Patient characteristics as predictors of image quality and diagnostic accuracy of MDCT compared with conventional coronary angiography for detecting coronary artery stenoses: CORE-64 Multicenter International Trial. AJR Am J Roentgenol. 2010; 194(1):93-102.
15. Folsom AR, Kronmal RA, Detrano RC, et al. Coronary artery calcification compared with carotid intima-media thickness in the prediction of cardiovascular disease incidence: the Multi-Ethnic Study of Atherosclerosis (MESA).  Arch Intern Med. 2008; 168(12):1333-1339.
16. Gibbons R, Gerber T.  Calcium scoring with computed tomography.  What is the radiation risk?  Arch Int Med. 2009; 169(13):1185-1187.
17. Greenland P, Kizilbash MA. Coronary computed tomography in coronary risk assessment. J Cardiopulm Rehabil. 2005; 25:3-10.
18. Greenland P, LaBree L, Azen SP, et al. Coronary artery calcium score combined with Framingham score for risk prediction in asymptomatic individuals. JAMA. 2004; 291:210-215.
19. Henneman MM, Schuijf JD, Pundziute G, et al. Noninvasive evaluation with multislice computed tomography in suspected acute coronary syndrome: plaque morphology on multislice computed tomography versus coronary calcium score. J Am Coll Cardiol. 2008; 52(3):216-222.
20. Ioannidis JPA, Tzoulaki I.  What makes a good predictor?  The evidence applied to coronary artery calcium score.  JAMA. 2010; 303(16):1646-1647.
21. Johnson KM, Dowe DA.  The detection of any coronary calcium outperforms Framingham Risk Score as a first step in screening for coronary atherosclerosis.  AJR. 2010; 194:1235-1243.
22. Kalia NK, Miller LG, Nasir K, et al.  Visualizing coronary calcium is associated with improvements in adherence to statin therapy. Atherosclerosis. 2006; 185:394-399.
23. Kim KP, Einstein AJ, Berrington de GA. Coronary artery calcification screening: estimated radiation dose and cancer risk. Arch Intern Med. 2009; 169:1188-1194.
24. Kondos GT, Hoff JA, Sevrukov A, et al. Coronary artery calcium and cardiac events electron-beam tomography coronary artery calcium and cardiac events: A 37-Month follow-up of 5,635 initially asymptomatic low to intermediate risk adults. Circulation. 2003; 107:2571-2576.
25. Kronmal RA, McClelland RL, Detrano R, et al. Risk factors for the progression of coronary artery calcification in asymptomatic subjects: results from the Multi-Ethnic Study of Atherosclerosis (MESA). Circ. 2007; 115(21):2722-2730.
26. Lakoski SG, Greenland P, Wong ND, et al. Coronary Artery Calcium Scores and Risk for Cardiovascular Events in Women Classified as "Low Risk" Based on Framingham Risk Score: the multi-ethnic study of atherosclerosis (MESA). Arch Intern Med. 2007; 167(22):2437-2442.
27. LaMonte MJ, FitzGerald SJ, Church TS, et al. Coronary artery calcium score and coronary heart disease events in a large cohort of asymptomatic men and women. Am J Epidemiol. 2005; 162(5):421-429.
28. McClelland RL, Nasir K, Budoff M, et al. Arterial age as a function of coronary artery calcium (from the Multi-Ethnic Study of Atherosclerosis [MESA]).  Am J Cardiol. 2009; 103(1):59-63.
29. Michos ED, Nasir K, Braunstein JB, et al. Framingham risk equation underestimates subclinical atherosclerosis risk in asymptomatic women. Atherosclerosis. 2006; 184:201-206.
30. Nasir K, Budoff MJ, Post WS, et al. Electron beam CT versus helical CT scans for assessing coronary calcification: current utility and future directions. Am Heart J. 2003; 146:969-977.
31. Nasir K, McClelland R, Blumenthal RS, et al. Coronary artery calcium in relation to initiation and continuation of cardiovascular preventative medications: The Multi-Ethnic Study of Atherosclerosis (MESA). Circ Cardiovasc Qual Outcomes. 2010; 3(3): 228-235.
32. O'Malley PG, Feuerstein IM, Taylor AJ. Impact of electron beam tomography, with or without case management, on motivation, behavioral change, and cardiovascular risk profile: a randomized controlled trial. JAMA. 2003;  289(17):2215-2223.
33. Orakzai RH, Nasir K, Orakzai SH, et al. Effect of patient visualization of coronary calcium by electron beam computed tomography on changes in beneficial lifestyle behaviors. Am J Cardiol. 2008; 101:999-1002.
34. Park R, Detrano R, Xiang M, et al. Combined use of computed tomography coronary calcium scores and C-reactive protein levels in predicting cardiovascular events in nondiabetic individuals. Circulation. 2002; 106:2073-2077.
35. Polonsky TS, McClelland RL, Jorgensen NW, et al.  Coronary artery calcium score and risk classification for coronary heart disease prediction.  JAMA. 2010; 303(16):1610-1616.
36. Preis SR, Hwang SJ, Fox CS, et al. Eligibility of individuals with subclinical coronary artery calcium and intermediate coronary heart disease risk for reclassification (from the Framingham Heart Study). Am J Cardiol. 2009; 103(12):1710-1715.
37. Raggi P, Callister TQ, Shaw LJ. Progression of coronary artery calcium and risk of first myocardial infarction in patients receiving cholesterol-lowering therapy. Arterioscler Thromb Vasc Biol. 2004a; 24(7):1272-1277.
38. Raggi P, Gongora MC, Gopal A, et al.  Coronary artery calcium to predict all-cause mortality in elderly men and women. J Am Coll Cardiol. 2008; 52(1):17-23.
39. Raggi P, Shaw LJ, Berman DS, Callister TQ. Gender-based differences in the prognostic value of coronary calcification. J Womens Health (Larchmt ). 2004b; 13(3):273-283.
40. Schenker MP, Dorbala S, Hong EC, et al. Interrelation of coronary calcification, myocardial ischemia, and outcomes in patients with intermediate likelihood of coronary artery disease: a combined positron emission tomography/computed tomography study.  Circ. 2008; 117(13):1693-1700.
41. Shaw LJ, Raggi P, Schisterman E, et al. Prognostic value of cardiac risk factors and coronary artery calcium screening for all-cause mortality. Radiology. 2003; 228(3):826-833.
42. Shaw LJ, Taylor A, Raggi P, Berman DS. Role of noninvasive imaging in asymptomatic high-risk patients. J Nucl Cardiol. 2006; 13(2):156-162.
43. Taylor AJ, Bindeman J, Feuerstein I, et al. Coronary calcium independently predicts incident premature coronary heart disease over measured cardiovascular risk factors: mean three-year outcomes in the Prospective Army Coronary Calcium (PACC) project. J Am Coll Cardiol. 2005; 46:807-814.
44. Taylor AJ, Bindeman J, Feuerstein I, et al. Community-based provision of statin and aspirin after the detection of coronary artery calcium within a community-based screening cohort. J Am Coll Cardiol. 2008; 51:1337-1341.
45. Vliegenthart R, Oudkerk M, Song B, et al. Coronary calcification detected by electron-beam computed tomography and myocardial infarction. The Rotterdam Coronary Calcification Study. Eur Heart J. 2002; 23(20):1596-1603.
46. Vliegenthart R, Oudkerk M, Hofman A, et al. Coronary calcification improves cardiovascular risk prediction in the elderly. Circulation. 2005; 112:572-577.
47. Wang L, Jerosch-Herold M, Jacobs DR Jr, MESA Study Investigators, et al. Coronary artery calcification and myocardial perfusion in asymptomatic adults: the MESA (Multi-Ethnic Study of Atherosclerosis). J Am Coll Cardiol. 2006; 48(5):1018-1026.

Government Agency, Medical Society, and Other Authoritative Publications:

1. Agency of Health Technology Assessment (DAHTA) at German Institute for Medical Documentation and Information (DIMDI). Computed tomography for the measurement of coronary calcification in asymptomatic risk patients [summary]. Technology Assessment. Cologne, Germany; DIMDI; 2006.
2. American College of Radiology Practice Guideline for the performance and interpretation of Cardiac Computed Tomography (CT). Effective 10/01/06. Available at:  http://acr.org/SecondaryMainMenuCategories/quality_safety/guidelines/dx.aspx.  Accessed on March 11, 2010.
3. Bluemke DA, Achenbach S, Budoff M, et al. Noninvasive Coronary Artery Imaging. Magnetic Resonance Angiography and Multidetector Computed Tomography Angiography. A Scientific Statement from the American Heart Association Committee on Cardiovascular Imaging and Intervention of the Council on Cardiovascular Radiology and Intervention, and the Councils on Clinical Cardiology and Cardiovascular Disease in the Young. Circulation 2008; 118:586-606.
4. Budoff MJ, Achenbach S, Blumenthal RS, et al. Assessment of Coronary Artery Disease by Cardiac Computed Tomography. A Scientific Statement from the American Heart Association Committee on Cardiovascular Imaging and Intervention, Council on Cardiovascular Radiology and Intervention, and Committee on Cardiac Imaging, Council on Clinical Cardiology.  Circ. 2006; 114:1761-1791.  Available at: http://circ.ahajournals.org/cgi/reprint/114/16/1761?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=Assessment+of+Coronary+Artery+Disease+by+Cardiac+Computed+&searchid=1&FIRSTINDEX=0&resourcetype=HWCIT.   Accessed on March 11, 2010.
5. California Technology Assessment Forum (CTAF). Utility of Coronary Artery Calcium Measurements in Cardiovascular Disease. February 2005. Available at: http://www.ctaf.org/content/assessment/detail/570.  Accessed on March 11, 2010.
6. Centers for Medicare and Medicaid Services. National Coverage Determination for Computerized Tomography. NCD #220.1. Effective March 13, 2008. Available at: http://www.cms.hhs.gov/MCD/viewncd.asp?ncd_id=220.1&ncd_version=2&basket=ncd%3A220%2E1%3A2%3AComputed+Tomography.  Accessed on March 11, 2010.
7. Fowler-Brown A, Pignone M, Pletcher M, Tice JA, U.S. Preventive Services Task Force, et al. Exercise tolerance testing to screen for coronary heart disease: a systematic review for the technical support for the U.S. Preventive Services Task Force. Ann Intern Med. 2004; 140(7):W9-24.
8. Gerber TC, Carr JJ, Arai AE, et al. Ionizing radiation in cardiac imaging: a science advisory from the American Heart Association Committee on Cardiac Imaging of the Council on Clinical Cardiology and Committee on Cardiovascular Imaging and Intervention of the Council on Cardiovascular Radiology and Intervention. Circulation. 2009; 119(7):1056-1065.
9. Graham I, Atar D, Borch-Johnsen K, Boysen G, European Society of Cardiology (ESC) Committee for Practice Guidelines (CPG), et al. European guidelines on cardiovascular disease prevention in clinical practice: executive summary: Fourth Joint Task Force of the European Society of Cardiology and Other Societies on Cardiovascular Disease Prevention in Clinical Practice (Constituted by representatives of nine societies and by invited experts). Eur Heart J. 2007; 28(19):2375-2414.
10. Greenland P, Bonow RO, Brundage BH, et al. ACCF/AHA 2007 Clinical Expert Consensus Document on Coronary Artery Calcium Scoring by CT in Global Cardiovascular Risk Assessment and in Evaluation of Patients with Chest Pain: A Report of the American College of Cardiology Foundation Clinical Expert Consensus Task Force (ACCF/AHA Writing Committee to update the 2000 Expert Consensus Document on Electron Beam Computed Tomography). J Am Coll Cardiol. 2007; 49:378-402.  (Co-published in Circulation. Jan. 23, 2007.)  Available at: http://www.americanheart.org/downloadable/heart/1168626471943CECD%20on%20EBCT%20rev3.pdf. Accessed on March 10, 2010.
11. Grundy SM, Cleeman JI, Merz CN, et al. Implications of recent clinical trials for the National Cholesterol Education Program Adult Treatment Panel III guidelines.  Circ. 2004; 110:227-239. Erratum:  Circ. 2004; 110:763.
12. Hendel RC, Patel MR, Kramer CM, et al. ACCF/ACR/SCCT/SCMR/ASNC/NASCI/SCAI/SIR Appropriateness Criteria for Cardiac Computed Tomography and Cardiac Magnetic Resonance Imaging: A report of the American College of Cardiology Foundation Quality Strategic Directions Committee Appropriateness Criteria Working Group, American College of Radiology, Society of Cardiovascular Computed Tomography, Society for Cardiovascular Magnetic Resonance, American Society of Nuclear Cardiology, North American Society for Cardiac Imaging, Society for Cardiovascular Angiography and Interventions and Society of Interventional Radiology.  J Am Col Cardiol. 2006; 48(7):1475-1497.
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1. American Heart Association (AHA). Information by disease.  Available at: http://www.americanheart.org.  Accessed on March 11, 2010.
2. Multi-Ethnic Study of Atherosclerosis (MESA) Coordinating Center, University of Washington, Seattle, WA.  Available at: http://www.mesa-nhlbi.org/CACReference.aspx and http://www.mesa-nhlbi.org/Publications.aspx.  Accessed on March 11, 2010.
3. National Heart, Lung, and Blood Institute. Facts about Coronary Heart Disease. Available at: http://www.nhlbi.nih.gov.  Accessed on March 11, 2010.
4. Radiological Society of North America, Inc. RadiologyInfo™. Cardiac CT for Calcium Scoring. June 26, 2009.  Available at:  http://www.radiologyinfo.org/en/pdf/ct_calscoring.pdf.  Accessed on March 11, 2010.
5. Additional information available:  Redberg RF, Benjamin EJ, American Academy of Family Physicians, American Association of Cardiovascular and Pulmonary Rehabilitation, Preventive Cardiovascular Nurses Association. ACCF/AHA 2009 performance measures for primary prevention of cardiovascular disease in adults: a Report of the American College of Cardiology Foundation/American Heart Association Task Force on performance measures (writing committee to develop performance measures for primary prevention of cardiovascular disease): developed in collaboration with the American Academy of Family Physicians; American Association of Cardiovascular and Pulmonary Rehabilitation; and Preventive Cardiovascular Nurses Association: endorsed by the American College of Preventive Medicine, American College of Sports Medicine, and Society for Women's Health Research. Circ. 2009; 120(13):1296-1336.  Available at:  http://content.onlinejacc.org/cgi/reprint/54/14/1364.pdf.  Accessed on March 11, 2010.

Cine Computed X-Ray Tomography
Computed Tomography, Electron Beam
Helical CT
High-Speed Computed X-Ray Tomography
Multirow Detector CT (MDCT)
Multislice Spiral CT (MSCT)
Rapid Acquisition X-Ray Computed Tomography
Ultrafast^® Computed Tomography (CT)

The use of specific product names is illustrative only.  It is not intended to be a recommendation of one product over another, and is not intended to represent a complete listing of all products available.