High-resolution selective three-dimensional magnetic resonance coronary angiography with navigator-echo technique: segment-by-segment evaluation of coronary artery stenosis

Reduced artifacts and improved diagnostic value of 640-slice computed tomography in patients with cardiac pacemakers

Objective

The aim of this study was to compare the feasibility of 640-slice with 64-slice computed tomography (CT) coronary angiography for diagnosing coronary lesions in patients with pacemakers.

Methods

Forty-five and 50 patients with pacemakers and with suspected or known coronary artery disease underwent 64-slice (64 group) and 640-slice (640 group) CT scans, respectively. All segments of the vessels were evaluated according to the 15-segment model recommended by the American Heart Association.

Results

The incidence of moderate or severe artifacts was significantly lower (7.27% vs. 32.17%) and the diagnosable rate for coronary lesions was higher (98.91% vs. 94.19%) in the 640 compared with the 64 group. In the 64 group, the incidence of artifacts in patients with a heart rate >65 bpm (20.98%) was higher than in those with a heart rate <65 bpm (15.67%), although the difference was not significant, while the incidence of artifacts was significantly higher in patients with heart arrhythmia (21.40%) compared with in those with normal heart rhythm (15.09%).

Conclusions

Among patients with pacemakers and a higher heart rate or heart arrhythmia, 640-slice CT may be more effective than 64-slice CT for diagnosing coronary lesions, by reducing moderate and severe artifacts.

Optimization of acquisition trajectories for 3D rotational coronary venography

OBJECTIVE

Rotational coronary X-ray imaging on C-arm systems provides a multitude of diagnostic projections from the vascular tree with a single contrast agent bolus. The acquisition trajectory is typically limited to a circular arc with a fixed caudo-cranial angulation. This may cause sub- optimal projection directions for specific vessel segments for all acquired views, e.g., those segments orthogonal to the axis of rotation. In this paper, a method is presented to calculate a patient-independent acquisition trajectory with respect to vessel foreshortening and overlap for multiple vessel segments of the coronary tree. This method can be applied to artery as well as vein anatomy.

METHODS

Rotational coronary venograms of 14 patients have been used to generate three-dimensional mesh representations with a semi-automatic two view modeling algorithm. The venous tree is divided into seven different vessel segments. Foreshortening and overlap of every segment are calculated and combined for all patients in a measure called obstruction value. The weighted obstruction values of all vessel segments define a cost function for the entire two-dimensional angular range of the C-arm system. Viterbi's algorithm is used to calculate an optimal trajectory with respect to this cost function. The method is validated by leave-one-out cross-validation on the 14 rotational venography data sets and on simulated venograms of a segmented computed tomography (CT) data set. Projection images with a foreshortening value below 10% and overlap below 20% are rated 'optimal'.

RESULTS

In 12 (85.7%) data sets, 43% more optimal images were acquired using the presented method compared to the standard circular arc trajectory. As well, in 13 (92.8%) data sets 38% more vessel segments can be optimally visualized in the acquired images. The test on the CT data set showed that the resulting average root-mean-square error of the extracted centerline points of the segmented CT data set compared to the error based on the views from the circular arc was reduced from 2.52 to 1.55 mm.

CONCLUSION

In a first test, the method proved to deliver improved image quality by reducing foreshortening and overlap of vessel segments and may therefore also improve the centerline extraction accuracy of the semi-automatic two view modeling method.

Noninvasive imaging for coronary artery disease: a technology assessment for the Medicare Coverage Advisory Commission

This report describes a review of the available scientific evidence through 2005 on direct noninvasive imaging tests (NITs) for coronary artery disease. In particular, the report addresses 6 key questions provided by the Agency for Healthcare Research and Quality and the Centers for Medicare and Medicaid Services. The questions examine the degree to which current evidence supports confident judgments about the use of NITs in the assessment of native coronary artery stenosis in clinical practice. The 2 NITs that are examined in detail in this report are 16 (and higher)-multidetector computed tomography angiography and 1.5-T magnetic resonance angiography to evaluate for stenosis in native coronary arteries. Reported sensitivity of NITs ranged from 68% to 100%; reported specificity ranged from 57% to 100% (patient-based analysis). Limitations include the exclusion of significant numbers of segments and patients, with often only the proximal coronary segments visualized. There is no direct evidence assessing the clinical use of NITs in terms of the incremental benefits or risks compared to alternative testing strategies. Although the ability of noninvasive direct coronary imaging technologies is promising-particularly the 64-multidetector computed tomography angiography-the evidence does not provide strong guidance on whether and how such technologies should be used in the population generally, or for Medicare beneficiaries specifically. Informed clinical and policy decision making will require further study of these technologies in well-characterized clinical contexts, in typical practice settings, and with attention to impact on management and health outcomes.

Combination of free-breathing and breathhold steady-state free precession magnetic resonance angiography for detection of coronary artery stenoses

PURPOSE

To analyze the incremental diagnostic value of a combination of two approaches (free-breathing and breathhold) vs. the sole free-breathing approach to coronary magnetic resonance angiography (CMRA) for detection of significant stenoses.

MATERIALS AND METHODS

Thirty patients were consecutively included in this prospective trial. CMRA was performed on a 1.5-T MR scanner (Magnetom Sonata, Siemens) using a balanced steady-state free precession (SSFP) sequence during free-breathing (2.4 x 0.9 x 0.7 mm3). Breathholding acquisitions (3.0 x 1.5 x 0.7 mm3) were only performed in cases in which the quality of free-breathing CMRA precluded assessment. Patients with contraindications to CMRA, claustrophobia, or nonassessable images were not excluded from the assessment of diagnostic accuracy (intention-to-diagnose design).

RESULTS

In 60% of all free-breathing coronary acquisitions the image quality was adequate for diagnostic assessment. For the remaining 40% of the cases, breathhold acquisitions were obtained. The sensitivity, specificity, nonassessable rate, and accuracy in identifying main coronary branches with significant stenoses using the combination of both breathing approaches and the free-breathing approach alone were 65% vs. 32%, 73% vs. 53%, 24% vs. 52%, and 71% vs. 46%, respectively (P < 0.001).

CONCLUSION

In this consecutive cohort of patients, the combination of free-breathing and breathhold CMRA significantly improved diagnostic accuracy. Nevertheless, even this combination did not reach accuracies sufficient for routine clinical application.

Meta-analysis of comparative diagnostic performance of magnetic resonance imaging and multislice computed tomography for noninvasive coronary angiography

BACKGROUND

Magnetic resonance imaging (MRI) and multislice computed tomography (MSCT) have emerged as potential noninvasive coronary imaging techniques. The objective of the present study was to clarify the current accuracy of both modalities in the detection of significant coronary artery lesions (compared to conventional angiography as the gold standard) by means of a comprehensive meta-analysis of the presently available literature.

METHODS

A total of 51 studies on the detection of significant coronary artery stenoses (> or = 50% diameter stenosis) and comparing results with conventional angiography were identified by means of a MEDLINE search. Weighted sensitivities, specificities, and predictive values, all with 95% CIs, as well as summary odds ratios, were calculated for both techniques. In addition, the relationship between diagnostic specificity and disease prevalence was determined using metaregression analysis.

RESULTS

A comparison of sensitivities and specificities revealed significantly higher values for MSCT (weighted average 85% [95% CI 86%-88%] and 95% [95% CI 95%]) as compared with MRI (weighted average 72%, 95% CI 69%-75% and 87%, 95% CI 86%-88%). A significantly higher odds ratio (16.9-fold) for the presence of significant stenosis was observed for MSCT as compared with MRI (6.4-fold) (P < .0001). Linear regression analysis revealed a better specificity for MSCT versus MRI in lower disease prevalence populations (P = .056).

CONCLUSION

Meta-analysis of the available studies with MRI and MSCT for noninvasive coronary angiography indicates that MSCT has currently a significantly higher accuracy to detect or exclude significant coronary artery disease.

Efficacy of Cardiac MRI in the Evaluation of Ischemic Heart Disease

With the development of fast scan techniques and technical advances in software, cardiac MRI can now be used for morphological and functional evaluation of the heart with good reliability and high spatial and temporal resolution. Cardiac MRI is employed at many institutions, mainly for assessing ischemic heart disease. Cardiac MRI can be used to identify coronary artery stenosis, evaluate myocardial viability, assess left ventricular wall motion and function, measure coronary blood flow and flow reserve, and obtain other useful information for the diagnosis of ischemic heart disease in a single examination, serving as a true comprehensive cardiac study. With regard to the evaluation of coronary artery stenosis, new techniques, such as whole-heart coronary MRA, permit visualization of the coronary arteries to their peripheral branches without contrast agent. Good results have been reported for whole-heart MRA as compared with X-ray coronary angiography (CAG). Attempts to evaluate plaque characteristics by visualizing the walls of the coronary arteries have also been reported recently. Technical improvements have been made in myocardial perfusion MRI to detect myocardial ischemia and in delayed contrast-enhanced MRI to assess myocardial viability, and some researchers have recently reported that the diagnostic capabilities of these techniques match or surpass those of cardiac nuclear medicine studies. We outline the features of the latest MR imaging techniques for the diagnosis of ischemic heart disease, discuss their practical applications, and compare them with other imaging modalities.

Assessment of coronary arteries with total study time of less than 30 minutes by using whole-heart coronary MR angiography

This study had institutional review board approval, and all patients gave informed consent. The purpose of this study was to prospectively evaluate the use of whole-heart three-dimensional (3D) coronary magnetic resonance (MR) angiography in patients suspected of having coronary artery disease. Whole-heart coronary MR angiography was performed in 39 patients (30 men and nine women; mean age, 63.9 years +/- 15.6 [standard deviation]) by using a steady-state free precession sequence with free breathing. Twenty patients (16 men and four women; mean age, 64.9 years +/- 11.7) also underwent conventional coronary angiography. MR angiography was successfully completed in 34 of 39 patients (87%); the average imaging time was 13.8 minutes +/- 3.8. Sensitivity and specificity of MR angiography for detecting significant stenosis were 82% (14 of 17 arteries) and 91% (39 of 43 arteries), respectively. Whole-heart coronary MR angiography with a navigator-gated steady-state sequence can enable reliable 3D visualization of the coronary arteries in patients suspected of having coronary artery disease.

Head-to-Head Comparison of Three-Dimensional Navigator-Gated Magnetic Resonance Imaging and 16-Slice Computed Tomography to Detect Coronary Artery Stenosis in Patients

OBJECTIVES

The purpose of this research was to compare the diagnostic accuracy of three-dimensional navigator-gated magnetic resonance (MR) imaging and 16-slice multidetector row computed tomography (MDCT) versus quantitative coronary angiography (QCA) for the detection of coronary artery stenosis in patients.

BACKGROUND

Both MR and MDCT are novel non-invasive tests, which have been proposed for noninvasive detection of coronary artery disease. Yet their diagnostic accuracy has not been directly compared in the same population.

METHODS

Fifty-two patients underwent coronary MR and 16-slice MDCT before invasive coronary angiography. Diameter stenosis (DS) severity in vessels >1.5-mm reference diameter were graded visually and measured quantitatively on both MR and MDCT images. Diagnostic accuracy of both methods was compared using QCA as the reference test.

RESULTS

According to QCA, 81 of 452 (18%) coronary segments with >1.5 mm diameter had >50% DS. By visual analysis, MR and MDCT had similar sensitivity (75% vs. 82%, p = NS), specificity (77% vs. 79%, p = NS), and diagnostic accuracy (77%, vs. 80%, p = NS) for detection of >50 % DS. Quantitative measures of DS by MR (r = 0.60, p < 0.001) and MDCT (r = 0.75, both p < 0.001) correlated well with QCA. Receiver-operating characteristic analysis demonstrated that quantification of DS severity improved the diagnostic accuracy of MDCT (area under curve [AUC] 0.81 vs. 0.92, p < 0.001) but not that of MR (AUC 0.78 vs. 0.83, p = NS).

CONCLUSIONS

Visual assessment of coronary diameter stenosis severity by MR or MDCT allows identification of significant coronary artery disease with a similar high diagnostic accuracy. Quantitative analysis significantly further improves the diagnostic accuracy of MDCT but not that of MR.

Diagnostic performance of coronary magnetic resonance angiography as compared against conventional X-ray angiography: a meta-analysis

OBJECTIVES

This study was designed to define the current role of coronary magnetic resonance angiography (CMRA) for the diagnosis of coronary artery disease (CAD).

BACKGROUND

Coronary magnetic resonance angiography has been proposed as a promising noninvasive method for diagnosis of CAD, but individual studies evaluating its clinical value have been of limited sample size.

METHODS

We identified all studies (MEDLINE and EMBASE) that evaluated CAD by both CMRA and conventional angiography in >/=10 subjects during the period 1991 to January 2004. We recorded true and false positive and true and false negative CMRA assessments for detection of CAD using X-ray angiography as the reference standard. Analysis was done at segment, vessel, and subject level.

RESULTS

We analyzed 39 studies (41 separate comparisons). Across 25 studies (27 comparisons) with data on 4,620 segments (993 subjects), sensitivity and specificity for detection of CAD were 73% and 86%, respectively. Vessel-level analyses (16 studies, 2,041 vessels) showed sensitivity 75% and specificity 85%. Subject-level analyses (13 studies, 607 subjects) showed sensitivity 88% and specificity 56%. At the segment level, sensitivity was 69% to 79% for all but the left circumflex (61%) coronary artery; specificity was 82% to 91%. There was considerable between-study heterogeneity, but weighted summary receiver-operating characteristic curves agreed with these estimates. There were no major differences between subgroups based on technical or population characteristics, year of publication, reported blinding, or sample size.

CONCLUSIONS

In evaluable segments of the native coronary arteries, CMRA has moderately high sensitivity for detecting significant proximal stenoses and may have value for exclusion of significant multivessel CAD in selected subjects considered for diagnostic catheterization.

Role of magnetic resonance imaging in visualizing coronary arteries

Ischemic heart disease is the leading cause of death worldwide. At present, coronary angiography is the gold standard for the diagnosis of coronary artery disease. Conventional coronary angiography is an invasive procedure with a small, yet inherent risk of myocardial infarction, stroke, potential arrhythmias, and death. Other noninvasive diagnostic tools, such as electrocardiography, echocardiography, and nuclear imaging are now widely available but are limited by their inability to directly visualize and quantify coronary artery stenoses and predict the stability of plaques. Coronary magnetic resonance angiography (MRA) is a technique that allows visualization of the coronary arteries by noninvasive means; however, it has not yet reached a stage where it can be used in routine clinical practice. Although coronary MRA is a potentially useful diagnostic tool, it has limitations. Further research should focus on improving the diagnostic resolution and accuracy of coronary MRA. This review summarizes results from several studies comparing coronary MRA with conventional coronary angiography. Current two-dimensional and three-dimensional coronary MRA techniques and their limitations are also discussed.

Cardiovascular magnetic resonance imaging

Recent advancements in magnetic resonance imaging hardware and software permit the assessment of cardiovascular structure and function at rest and during exercise or pharmacology-induced cardiac stress. With these developments, knowledge of cardiovascular imaging protocols in the magnetic resonance imaging environment is critical for nursing personnel. The purpose of this article is to review information pertinent to working in a magnetic resonance imaging environment and to describe the requirements of nursing personnel performing cardiovascular magnetic resonance imaging examinations.

MR imaging in ischemic heart disease

This article reviews the current MR imaging literature with respect to ischemic heart disease and focuses on the clinical practicalities of cardiac MR imaging today.

Direct monitoring of coronary artery motion with cardiac fat navigator echoes

Navigator echoes (NAVs) provide an effective means of monitoring physiological motion in magnetic resonance imaging (MRI). Motion artifacts can be suppressed by adjusting the data acquisition accordingly. The standard pencil-beam NAV has been used to detect diaphragm motion; however, it does not monitor cardiac motion effectively. Here we report a navigator approach that directly measures coronary artery motion by exciting the surrounding epicardial fat and sampling the signal with a k-space trajectory sensitized to various motion parameters. The present preliminary human study demonstrates that superior-inferior (SI) respiratory motion of the coronary arteries detected by the cardiac fat NAV highly correlates with SI diaphragmatic motion detected by the pencil-beam NAV. In addition, the cardiac fat navigator gating is slightly more effective than the diaphragmatic navigator gating in suppressing motion artifacts in free-breathing 3D coronary MR angiography (MRA).