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CT More Accurate Than MRI for Ruling out Coronary Artery Disease

  • Authors: News Author: Michael O'Riordan
    CME Author: Laurie Barclay, MD
  • CME Released: 2/5/2010
  • Valid for credit through: 2/5/2011
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Target Audience and Goal Statement

This article is intended for primary care clinicians, cardiologists, radiologists, and other specialists caring for patients at risk for or with suspected coronary artery disease.

The goal of this activity is to provide medical news to primary care clinicians and other healthcare professionals in order to enhance patient care.

Upon completion of this activity, participants will be able to:

  1. Compare the sensitivity and specificity of multislice computed tomography and magnetic resonance imaging vs the gold standard of conventional coronary angiography for a diagnosis of coronary artery disease.
  2. Describe factors affecting the sensitivity of computed tomography for a diagnosis of coronary artery disease.


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  • Michael O'Riordan

    Michael O'Riordan is a journalist for Medscape. Before becoming a journalist for, now part of the WebMD Professional Network, he worked for WebMD Canada. Michael studied at Queen's University in Kingston and the University of Toronto and has a master's degree in journalism from the University of British Columbia, where he specialized in medical reporting. He can be contacted at [email protected]


    Disclosure: Michael O'Riordan has disclosed no relevant financial relationships.


  • Brande Nicole Martin

    CME Clinical Editor, Medscape, LLC


    Disclosure: Brande Nicole Martin has disclosed no relevant financial relationships.

CME Author(s)

  • Laurie Barclay, MD

    Freelance writer and reviewer, Medscape, LLC


    Disclosure: Laurie Barclay, MD, has disclosed no relevant financial relationships.

CME Reviewer(s)

  • Sarah Fleischman

    CME Program Manager, Medscape, LLC


    Disclosure: Sarah Fleischman has disclosed no relevant financial relationships.

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CT More Accurate Than MRI for Ruling out Coronary Artery Disease

Authors: News Author: Michael O'Riordan CME Author: Laurie Barclay, MDFaculty and Disclosures

CME Released: 2/5/2010

Valid for credit through: 2/5/2011


February 5, 2010 — Computed tomography (CT) is a better noninvasive imaging test than magnetic resonance imaging (MRI) for detecting and ruling out coronary artery disease, according to the results of a new meta-analysis [1]. The newer CT scanners are also more sensitive than older scanners and involve less iodinated contrast agent but higher radiation exposure, report the researchers.

"Our meta-analysis suggests that CT has better sensitivity and specificity than MRI and is therefore advantageous for detecting and ruling out clinically relevant coronary stenoses," according to lead investigator Georg Schuetz (Charité Medical School, Berlin, Germany) and colleagues. "CT should be considered the foremost noninvasive alternative to coronary angiography" in selected patient populations.

The results of the study are published online February 2, 2010 in the Annals of Internal Medicine.

Up Against the Gold Standard

As the authors point out, including senior investigator Dr Marc Dewey (Charité Medical School, Berlin, Germany), CT and MRI are attractive alternatives to invasive coronary angiography for clinical decision making. Although conventional angiography is the gold standard, noninvasive coronary angiography with CT and MRI are used to rule out coronary artery disease in patients with a low pretest likelihood of disease, such as patients with inconclusive stress tests and atypical angina.

The meta-analysis included 89 CT studies and 19 MRI studies directly comparing the noninvasive imaging test with conventional coronary angiography. Most of the studies were performed in Europe at university hospitals and included only state-of-the-art CT scanners and MRI approaches. Significant coronary artery stenosis was defined as a reduction of 50% or greater in the coronary artery for CT, MRI, and conventional angiography.

The sensitivity and specificity for CT was 97.2% and 87.4%, respectively, and 87.1% and 70.3%, respectively, for MRI. An analysis restricted only to CT studies used to rule out coronary artery disease resulted in a similar sensitivity and specificity to the overall findings, whereas a subgroup analysis of scanners with more than 16 detector rows resulted in a significantly higher sensitivity than that for scanners with a maximum of 16 rows.

Diagnostic Accuracy for CT and MRI

Imaging test Mean sensitivity (95% CI) Mean specificity (95% CI)
MRI 87.1 (83.0–90.3) 70.3 (58.8–79.7)
CT 97.2 (96.2–98.0) 87.4 (84.5–89.8)
Used to rule out coronary artery disease (45 studies) 97.6 (96.1–98.5) 89.2 (86.0–91.8)
Used to rule out acute coronary syndrome (7 studies) 95.6 (87.2–98.6) 76.6 (50.9–91.2)
CT scanners >16 rows 98.1 (97.0–99.0) 89.4 (86.0–92.0)
CT scanners 12 to 16 rows 98.1 (94.0–97.0) 84.7 (80.0–89.0)

The researchers note that although technical advances have improved image quality for CT and MRI, multislice CT is more sophisticated and easier to perform, particularly since the CT examination is shorter than MRI, requires reduced breath-hold time, and doesn't constrain the patient to the same extent as MRI. "Thus, CT is more accepted, more widely available, and more favored by patients, and it has become reasonably cost-effective," write Schuetz and colleagues.

Commenting on the results of the study, Dr Roger Blumenthal (Johns Hopkins University, Baltimore, MD) agreed that CT angiography is much more accessible to clinicians than coronary magnetic resonance angiography. "The database with CT angiography is rapidly growing, and the amount of ionizing radiation associated with CT angiography in academic centers is steadily coming down," he said.

In the meta-analysis, the mean amount of contrast agent required was 37.8 g for the studies of CT scanners with <16 rows and 31.3 g for those with >16 rows. The mean radiation exposure, however, was significantly less, 9.4 mSv vs 13.0 mSv, for scanners with 16 rows or fewer compared with those with more than 16 rows, respectively.

Blumenthal noted that most clinicians consider only a standard coronary angiogram or noninvasive CT angiography in a patient with a low probability of obstructive coronary artery disease. He referred to the COURAGE trial, however, a study in patients with predominantly mild angina, and noted that "in many cases a treadmill stress echo can rule out significant inducible ischemia, and the clinician does not need to proceed with an angiogram."


  1. Schuetz GM, Zacharopoulou M, Schlattmann P, Dewey M. Meta-analysis: noninvasive coronary angiography using computed tomography versus magnetic resonance imaging. Ann Intern Med 2010; 152:167-177.

Clinical Context

Coronary artery disease is a major cause of morbidity and mortality in the United States. Although coronary artery disease is usually diagnosed through conventional coronary angiography, this test is invasive and is associated with potential harms.

There are several options for less invasive imaging procedures to visualize the coronary arteries. However, CT and MRI offer image quality superior to that of other noninvasive modalities. These noninvasive tests may be particularly helpful to reliably exclude coronary artery disease in patients with a low to moderate likelihood of the disease, thereby avoiding an unnecessary invasive test.

Study Highlights

  • The objective of this meta-analysis was to compare the efficacy of CT and MRI for ruling out clinically significant coronary artery disease in adults with suspected or known coronary artery disease.
  • The reviewers searched MEDLINE, EMBASE, and ISI Web of Science from inception through June 2, 2009, as well as reference lists of identified reviews.
  • Inclusion criteria were prospective English- or German-language studies comparing CT or MRI vs conventional coronary angiography in all patients studied, in which sufficient data were included for compilation of 2-x-2 tables.
  • 2 of the reviewers independently extracted patient data and study characteristics.
  • Differences were resolved by consensus opinion.
  • 89 studies of CT enrolled a total of 7516 patients and 20 studies of MRI, a total of 989 patients.
  • Coronary angiography was used as the gold standard.
  • For CT, mean sensitivity was 97.2% (95% confidence interval [CI], 96.2% - 98.0%), and specificity was 87.4% (CI, 84.5% - 89.8%), based on bivariate analysis of data.
  • For MRI, mean sensitivity was 87.1% (95% CI, 83.0% - 90.3%), and specificity was 70.3% (95% CI, 58.8% - 79.7%).
  • Studies including only patients with suspected coronary artery disease yielded a sensitivity of 97.6% for CT (95% CI, 96.1% - 98.5%) and a specificity of 89.2% (95% CI, 86.0% - 91.8%).
  • CT scanners with more than 16 rows had a significantly higher sensitivity (98.1%; 95% CI, 97.0% - 99.0%) than older-generation scanners (95.6%; 95% CI, 94.0% - 97.0%), based on covariate analysis of data (P < .050).
  • Compared with higher heart rates, heart rates of less than 60 beats/minute during CT yielded significantly better values for sensitivity (P < .001).
  • The investigators concluded that for ruling out coronary artery disease, CT is more accurate than MRI and that CT scanners with more than 16 rows improve sensitivity, as do slowed heart rates.
  • They recommended that CT be considered the foremost noninvasive alternative to conventional coronary angiography for detecting and ruling out coronary artery stenoses in selected patient populations.
  • They also recommended randomized studies to address the potential of coronary CT angiography for use in triage to positively affect management and outcomes in patients with suspected coronary artery disease.
  • Limitations of this meta-analysis include few studies that investigated coronary angiography with MRI, only 5 studies in which there were direct head-to-head comparisons of CT vs MRI, and observed heterogeneity explained only in part by covariate analyses.

Clinical Implications

  • For ruling out coronary artery disease, CT is more sensitive and specific than MRI, according to the results of a meta-analysis. CT should be considered the foremost noninvasive alternative to conventional coronary angiography for detecting and ruling out coronary artery stenoses in selected patient populations.
  • Factors improving the sensitivity of CT for detecting coronary artery disease include use of CT scanners with more than 16 rows and slowed heart rates during testing.

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