Noninvasive detection of coronary artery stenosis using contrast-enhanced three-dimensional breath-hold magnetic resonance coronary angiography

Recent Advances in Cardiac Magnetic Resonance Imaging

Cardiac magnetic resonance (CMR) imaging provides accurate anatomic information and advanced soft contrast, making it the reference standard for assessing cardiac volumes and systolic function. In this review, we summarize the recent advances in CMR sequences. New technical development has widened the use of CMR imaging beyond the simple characterization of myocardial scars and assessment of contractility. These novel CMR sequences offer comprehensive assessments of coronary plaque characterization, myocardial fiber orientation, and even metabolic activity, and they can be readily applied in clinical settings. CMR imaging is able to provide new insights into understanding the pathophysiologic process of underlying cardiac disease, and it can help physicians choose the best treatment strategies. Although several limitations, including the high cost and time-consuming process, have limited the widespread clinical use of CMR imaging so far, recent advances in software and hardware technologies have made the future more promising.

Cardiovascular Imaging: The Past and the Future, Perspectives in Computed Tomography and Magnetic Resonance Imaging

Today's noninvasive imaging of the cardiovascular system has revolutionized the approach to various diseases and has substantially affected prognostic information. Cardiovascular magnetic resonance (MR) and computed tomographic (CT) imaging are at center stage of these approaches, although 5 decades ago, these technologies were unheard of. Both modalities had their inception in the 1970s with a primary focus on noncardiovascular applications. The technical development of the various decades, however, substantially pushed the envelope for cardiovascular MR and CT applications. Within the past 10-15 years, MR and CT technologies have pushed each other in cardiac applications; and without the "rival" modality, neither one would likely not have reached its potential today. This view on the history of MR and CT in the field of cardiovascular applications provides insight into the story of success of applications that once have been ideas only but are at prime time today.

MR imaging of the coronary vasculature: imaging the lumen, wall, and beyond

The characteristics of coronary artery disease are gradual thickening of the coronary walls and narrowing of the vascular lumen by the buildup of atherosclerosis plaques. These morphologic changes can be noninvasively detected by coronary magnetic resonance (MR) imaging/MR angiography (MRA). In addition, functional changes, such as coronary wall distensibility and flow changes, may also be evaluated with MR imaging. However, the application of current MR imaging/MRA techniques is limited in clinical practice because of several adverse technical and physiologic factors, such as cardiac and respiratory motion. Many technical innovations have been adopted to address these problems from multiple aspects.

Magnetic resonance coronary angiography: where are we today?

Although cardiovascular magnetic resonance allows the non-invasive and radiation free visualization of both the coronary arteries and veins, coronary vessel wall imaging is still undergoing technical development to improve diagnostic quality. Assessment of the coronary vessels is a valuable addition to the analysis of cardiac function, cardiac anatomy, viability and perfusion which magnetic resonance imaging reliably allows. However, cardiac and respiratory motion and the small size of the coronary vessels present a challenge and require several technical solutions for image optimization. Furthermore, the acquisition protocols need to be adapted to the specific clinical question. This review provides an update on the current clinical applications of cardiovascular magnetic resonance coronary angiography, recent technical advances and describes the acquisition protocols in use.

Coronary imaging with cardiovascular magnetic resonance: current state of the art

Cardiovascular magnetic resonance allows noninvasive and radiation-free visualization of both the coronary arteries and veins, with the advantage of an integrated assessment of cardiac function, viability, perfusion, and anatomy. This combined approach provides valuable integrated information for patients with coronary artery disease and patients undergoing cardiac resynchronization therapy. Moreover, magnetic resonance offers the possibility of coronary vessel wall imaging, therefore assessing the anatomy and pathology of the normal and diseased coronary vessels noninvasively. Coronary magnetic resonance angiography is challenging because of cardiac and respiratory motion and the small size and tortuous path of the coronary vessels. Several technical solutions have been developed to optimize the acquisition protocol to the specific clinical question. The aims of this review are to provide an update on current technical improvements in coronary magnetic resonance angiography, including how to optimize the acquisition protocols, and to give an overview of its current clinical application.

Noninvasive coronary angiography focusing on calcification: multislice computed tomography compared with magnetic resonance imaging

OBJECTIVE

Calcification is a principal problem in noninvasive coronary angiography (CA) performed with multislice computed tomography (MSCT). Magnetic resonance imaging (MRI) supposedly neglects calcium. We compared both modalities.

METHODS

Sixty-eight patients admitted for CA underwent MSCT- and MRI-based noninvasive CA the day before. Stenosis detection (>or=50%) was visually performed and validated by quantitative CA.

RESULTS

The patient-based overall sensitivity, specificity, positive predictive value, and negative predictive value were 96.2%, 95.2%, 92.6%, and 97.6% for MSCT versus 69.2%, 64.3, 54.5%, 64.3%, and 77.1% for MRI, respectively. The segment-based overall results were 74.7%, 97.8%, 75.7%, and 97.6% for MSCT versus 40%, 93.8%, 37.5%, and 94.4% for MRI, respectively. Investigating the impact of coronary calcifications in the patient group with a volume score of 300 microL or greater resulted in 100%, 80%, 92.3%, and 100% for MSCT versus 70.8%, 86.7%, 89.5%, and 65% for MRI, respectively. The segment group with considerable hardening artifacts resulted in 85.3%, 83.9%, 76.3%, and 90.4% for MSCT versus 52.9%, 92.9%, 81.8%, and 76.5% for MRI, respectively.

CONCLUSIONS

There are no major advantages of MRI in cases of advanced coronary calcification.

Assessment of subclinical atherosclerosis and cardiovascular risk

Conventional cardiac risk factors do not fully explain the incidence of coronary artery disease and coronary events. Risk stratification and therapy based solely on these conventional risk factors may exclude a population who would otherwise benefit from lifestyle and risk factor modification. Recent efforts to improve our ability to recognize individuals and populations at increased risk of coronary events have focused on the noninvasive imaging of atherosclerosis, both in coronary and extracoronary arterial beds, or the identification of "non-traditional" serum markers. We review the complimentary role of these newer methods of risk stratification in the context of conventional risk factor evaluation.

Three-dimensional breathhold magnetization-prepared TrueFISP: a pilot study for magnetic resonance imaging of the coronary artery disease

PURPOSE

X-ray angiography is currently the standard test for the assessment of coronary artery disease. A substantial minority of patients referred for coronary angiography have no significant coronary artery disease. The purpose of this work was the evaluation of the accuracy of a three-dimensional (3D) breathhold coronary magnetic resonance angiography (MRA) technique in detecting hemodynamically significant coronary artery stenoses in a patient population with x-ray angiographic correlation.

MATERIALS AND METHODS

Sequential subjects (n = 33, M/F = 22/11, average age = 57) who were referred for conventional coronary angiography were enrolled in the study. The study protocol was approved by our institutional review board. Each subject gave written informed consent. Volume-targeted 3D breathhold coronary artery scans with ECG-triggered, segmented True Fast Imaging with Steady-state Precession (TrueFISP) were acquired for the left main (LM), left anterior descending (LAD), and right coronary arteries (RCAs). Coronary MRA was evaluated with conventional angiography as the gold standard.

RESULTS

The overall sensitivity, specificity, accuracy, positive predictive value (PPV), and negative predictive value (NPV) for diagnosing any hemodynamically significant coronary artery disease (> or =50% diameter reduction) with coronary MRA was 87%, 57%, 72%, 68%, and 80%, respectively. The sensitivity of the technique in the LM, LAD, and RCA was 100%, 83%, and 100%, respectively. The NPV of the technique in the LM, LAD, and RCA was 100%, 82%, and 100%, respectively.

CONCLUSIONS

Three-dimensional breathhold True Fast Imaging with Steady-state Precession is a promising technique for coronary artery imaging. It has a relatively high sensitivity and NPV. Results of this study warrant further technical improvements and clinical evaluation of the technique.

Noninvasive imaging of anomalous coronary arteries

Anomalous coronary arteries are a rare but recognized cause of myocardial ischemia and sudden death. Most patients with coronary anomalies remain asymptomatic because the anomaly either does not produce any symptoms during life or the first manifestation is sudden death. Noninvasive imaging plays crucial role in diagnosis of the potentially life threatening coronary anomalies.

Pathophysiology of coronary artery in-stent restenosis

In-stent restenosis reflects the interaction of a cascade of molecular and cellular events occurring within the vessel wall. Coronary stenting induces localized injury to the vessel wall, which leads to the release of thrombogenic, vasoactive, and lymphocytes mitogenic factors that result in processes causing re-narrowing at the injured site. Three major processes have been identified that lead to the in-stent restenosis: neointimal hyperplasia, elastic recoil, and negative arterial remodeling. The most important one is intimal hyperplasia. As the time course of neointimal hyperplasia is unknown, a causal relationship between the development of new blood vessels and clinical restenosis cannot be firmly established.

Magnetic resonance coronary angiography with Vasovist: in-vivo T1 estimation to improve image quality of navigator and breath-hold techniques

The purpose of the study was to estimate T1 values of blood and myocardium after a single injection of Vasovist and to assess Vasovist for magnetic resonance coronary angiography (MRCA). For all exams 0.05 mmol/kg of Vasovist was injected. T1 values of blood and myocardium were estimated over 30 min after injection. Twelve volunteers were examined on a 1.5-T Siemens system using a SSFP sequence with incrementally increasing inversion times for T1-estimation and a breath-hold 3D IR-FLASH sequence for MRCA. Eleven examinations were performed on 1.5-T Philips system using the Look-Locker approach for T1 estimation and a whole-heart inversion-prepared, 3D SSFP sequence for MRCA. SNR, CNR and image quality were assessed. T1 values of blood (5 min: 230 ms vs. 30 min: 275 ms) and myocardium (5 min: 99 ms vs. 30 min: 130 ms) increased over time. Whereas the blood SNR (1 min: 23.6 vs. 30 min: 21.2) showed no significant differences, the blood-to-myocardium CNR (1 min: 18.1 vs. 30 min: 13.8) and the image quality (1 min: 2.9 vs. 30 min: 3.8) degraded over time. Due to long plasma half-time the T1-shortening effect of Vasovist remains effective over 30 min, which allows for multiple breath-hold or high-resolution MRCA.

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.

Magnetic resonance imaging for ischemic heart disease

Cardiac MRI has long been recognized as an accurate and reliable means of evaluating cardiac anatomy and ventricular function. Considerable progress has been made in the field of cardiac MRI, and cardiac MRI can provide accurate evaluation of myocardial ischemia and infarction (MI). Late gadolinium (Gd)-enhanced MRI can clearly delineate subendocardial infarction, and the assessment of transmural extent of infarction on late enhanced MRI has been shown to be useful in predicting functional recovery of dysfunctional myocardium in patients after MI. Stress first-pass contrast-enhanced (CE) myocardial perfusion MRI can be used to detect subendocardial ischemia, and recent studies have demonstrated the high diagnostic accuracy of stress myocardial perfusion MRI for detecting significant coronary artery disease (CAD). Free-breathing, whole-heart coronary MR angiography (MRA) was recently introduced as a method that can provide visualization of all three major coronary arteries within a single three-dimensional (3D) acquisition. With further improvements in MRI techniques and the establishment of a standardized study protocol, cardiac MRI will play a pivotal role in managing patients with ischemic heart disease.

Coronary magnetic resonance angiography using magnetization-prepared contrast-enhanced breath-hold volume-targeted imaging (MPCE-VCATS)

OBJECTIVES

Coronary artery x-ray angiography (XRA) is currently the gold standard for the assessment of coronary artery disease. A substantial minority of patients referred for coronary angiography have no significant coronary artery disease. The purpose of this study is to evaluate magnetization-prepared contrast-enhanced breath-hold volume-targeted imaging (MPCE-VCATS), a new 3-dimensional breath-hold coronary magnetic resonance angiography (MRA) technique, in detecting hemodynamically significant coronary artery stenoses in a patient population, with XRA correlation.

MATERIALS AND METHODS

A total of 19 subjects who were referred for conventional coronary angiography were enrolled in the study. ECG-triggered MPCE-VCATS coronary artery scans were acquired for the left main coronary artery (LCA), left anterior descending (LAD), and right coronary artery (RCA). Coronary MRA and XRA results were compared.

RESULTS

The overall sensitivity, accuracy, and negative predictive value for diagnosing any hemodynamically significant coronary artery disease (> or =50% diameter reduction) was 91%, 80%, and 90%, respectively. The sensitivity of the technique in the LCA, LAD, and RCA was 100%, 100% and 78%, respectively. The negative predictive value of the technique was 100%, 100%, and 71%, respectively.

DISCUSSION

MPCE-VCATS is a promising technique for coronary artery imaging. It has a relatively high sensitivity as well as a high NPV. The results of the study may indicate a future role for the technique in obviating the need for some patients to undergo XRA.

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.

Cardiac CT in emergency department patients with acute chest pain

Current strategies for the triage of patients who have chest pain but normal initial cardiac enzyme levels and nondiagnostic electrocardiograms do not permit efficient risk stratification. The potentially fatal consequences and high malpractice costs of missed acute coronary syndromes lead every year to the unnecessary hospital admission of about 2.8 million patients who present with acute chest pain in emergency departments in the United States. Most of these patients are at very low risk for an acute coronary syndrome. However, the standard clinical work-up does not provide information about the presence and extent of coronary artery disease. In most patients (80%-94%) with an acute coronary syndrome, a significant coronary artery stenosis can be detected with selective coronary angiography. High levels of diagnostic accuracy also have been established for the detection of significant coronary artery stenosis with the use of 16- and 64-section multidetector computed tomography (CT) in patients with stable angina. Preliminary data indicate that multidetector CT also can help quantify and characterize coronary atherosclerotic plaque and that the CT findings are in good agreement with those at intravascular ultrasonography. Although multidetector CT provides accurate information about the presence of coronary artery disease, large blinded observational studies are warranted to identify CT characteristics with high accuracy for diagnosis of acute coronary syndromes. Such information would enable the conduct of randomized controlled trials to determine whether the detection of coronary stenosis and plaque with multidetector CT improves triage and reduces the costs or increases the cost-effectiveness of management of acute chest pain.

Breath-hold 3D steady-state free precession coronary MRA compared with conventional X-ray coronary angiography

PURPOSE

To evaluate the use of breath-hold three-dimensional (3D) steady-state free precession (SSFP) coronary magnetic resonance angiography (MRA) in patients with coronary artery disease (CAD) in comparison with conventional coronary x-ray angiography (XRA).

MATERIALS AND METHODS

Twenty-eight patients with suspected CAD were examined with the use of a breath-hold 3D-SSFP-MRA sequence and conventional XRA. To assess the accuracy of MRA, two clinicians who were blinded to patient information independently reviewed the MRA and XRA data, which were presented in a randomized order. To identify discrepancies between MRA and XRA, and assess features of coronary lesions on MRA, two additional clinicians examined MRA and XRA data that were presented side by side, divided into proximal, mid, and distal segments, and compared them segment by segment.

RESULTS

The sensitivity and specificity for diagnosing significant coronary stenoses (> 50% diameter narrowing) were 64% and 94%, respectively. At sites of coronary lesions identified on XRA, bright signals and enlarged vessel profiles, in addition to the characteristic narrow lumen, were frequently observed on MRA.

CONCLUSION

Breath-hold SSFP coronary MRA has good specificity but inconclusive sensitivity in diagnosing significant coronary stenoses, and provides important image features for depicting coronary lesions.

Emergency cardiac imaging: state of the art

Multiple strategies and testing modalities are available to evaluate patients presenting to the emergency department with cardiac complaints. Many provide anatomic and prognostic information about coronary stenosis and long-term out-comes. Although nuclear and stress echo imaging have the ability to predict outcomes in patients in the emergency department population, the newer modalities of cardiac imaging (EBCT, MDCT,and CMR) continue to show promising results and may soon be incorporated into emergency department chest pain centers. Protocols can be developed within an institution to meet the needs of the patient population while minimizing risk and improving outcomes for all patients.

3D MR coronary angiography: optimization of the technique and preliminary results

OBJECTIVE

Current clinical full MR angiography with multiple breathhold multiple thin slab acquisition (MTS) is difficult and arduous. This study describes the optimisation of the whole heart free - breathing balanced turbo field echo (B-TFE) protocol. A high-resolution image of the whole heart is produced in less or comparable time to MTS acquisition and allows for reconstruction afterwards to visualise the individual coronary arteries. The scan is easily performed because the volume has to be targeted only once.

DESIGN AND SETTING

Eighteen healthy adults without a history of cardiovascular disease underwent free-breathing 3D MR angiography with the B-TFE protocol. The whole-heart data set was reformatted in identical orientations in all subjects to visualise the major coronary arteries.

MAIN OUTCOME MEASURES

Vessel length, signal and contrast to noise ratio were determined and compared for each vessel.

RESULTS

Mean visible vessel lengths were 116 mm for the right, 102 mm for the left main and left descending and 76 mm for the left circumflex coronary artery. The average signal to noise ratio was 7.5 and contrast to noise ratio was 4.9. Because of the need for synchronised cardiac and respiratory triggering the coronaries could not be judged in 25% of the subjects.

CONCLUSIONS

The optimised B-TFE protocol had equal judgeability and vessels could be judged over longer contiguous distances compared to earlier implementations of the B-TFE protocol. We conclude whole heart free breathing navigator-gated and slice-tracked 3D coronary MR angiography with use of the adjusted B-TFE protocol is possible, but still suboptimal for clinical use.

Multidetector computed tomography for the diagnosis of coronary artery disease: a systematic review

PURPOSE

The study's purpose was to determine the sensitivity and specificity of contrast-enhanced multidetector computed tomography (CT) for the detection of coronary artery disease.

SUBJECTS AND METHODS

A search of the literature in all languages was performed incorporating both electronic and manual components. Manual reference checks of recent reviews and all original investigations supplemented the electronic searches.

RESULTS

Average sensitivity for patient-based detection of significant (>50% or > or =50%) stenosis was 61 of 64 (95%) with 4-slice CT, 276 of 292 (95%) with 16-slice CT, and 47 of 47 (100%) with 64-slice CT. Average specificity was 84% for 4-slice CT, 84% for 16-slice CT, and 100% for 64-slice CT. The sensitivity for a significant stenosis in evaluable segments was 307 of 372 (83%) with 4-slice CT, 1023 of 1160 (88%) with 16-slice CT, and 165 of 176 (94%) with 64-slice CT. Average specificity was 93% or greater with all multidetector CT. Seventy-eight percent of segments were evaluable with 4-slice CT, 91% with 16-slice CT, and 100% with 64-slice CT. Stenoses in proximal and mid-segments were shown with a higher sensitivity than distal segments. Left main stenosis was identified with high sensitivity with all multidetector CT, but sensitivity in other vessels increased with an increasing number of detectors.

CONCLUSION

Multidetector CT has the potential to be used as a screening test in appropriate patients. Contrast-enhanced 16-slice CT seems to be reasonably sensitive and specific for the detection of significant coronary artery disease but has shortcomings. Preliminary data with 64-slice CT suggest that it is more sensitive and specific.

Coronary MR imaging: breath-hold capability and patterns, coronary artery rest periods, and beta-blocker use

PURPOSE

To prospectively evaluate breath-hold capability and patterns, coronary artery rest periods, and beta-blocker use in coronary magnetic resonance (MR) imaging.

MATERIALS AND METHODS

Ethics committee approval and informed consent were obtained. In 210 consecutive patients (mean age, 61.8 years +/- 10.3 [standard deviation]; 146 men, 64 women), breath-hold patterns and maximal capability were assessed at expiration with dynamic navigator MR imaging (temporal resolution, 1 second). Left coronary artery (LCA) and right coronary artery (RCA) rest periods were determined at transverse cine imaging (steady-state free precession, retrospective gating, 40 phases per cycle). Before and after beta-blockade, rest periods were assessed in 25 additional patients (mean age, 61.4 years +/- 7.1; 20 men, five women). Differences were tested within groups with paired Student t test and between groups with unpaired Student t test (continuous variables) and chi(2) test (categoric variables). Pearson correlation was used to test the relationship between rest period and heart rate.

RESULTS

Four distinct breath-hold patterns, characterized by diaphragmatic motion, were identified: pattern 1, steady plateau (55% of patients); 2, initial drift followed by plateau (12%); 3, continuous drift (19%); and 4, irregular, unsteady behavior (14%). Mean breath-hold capability with patterns 1 and 2 was 29 seconds +/- 13 (range, 10-64 seconds). The rest period of LCA was longer than that of RCA (163 msec +/- 75 vs 123 msec +/- 60; P < .01) and began earlier in the cardiac cycle (521 msec +/- 149 vs 540 msec +/- 160; P < .01); In a minority of patients, LCA rest period began later (21%) or was shorter (14%). With no pharmacologic intervention, correlation between rest period duration and heart rate was weak (LCA, r = -0.52; RCA, r = -0.38; P < .01). However, beta-blockade significantly lowered heart rate (61.3 beats/min +/- 7.2 vs 82.6 beats/min +/- 12.5, P < .001) and increased rest duration (LCA, 201.8 msec +/- 83.6 vs 111.8 msec +/- 44.55; RCA, 134.8 msec +/- 57.3 vs 83.1 msec +/- 35.8; P < .001).

CONCLUSION

In 33% of patients (patterns 3 and 4), breath-hold pattern was unsuitable for high-spatial-resolution breath-hold MR imaging. LCA and RCA rest periods showed large variability in starting point and duration, with no correlation to heart rate.

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.

Magnetic resonance angiography of coronary arteries with a 3-dimensional magnetization-prepared true fast imaging with steady-state precession sequence compared with conventional coronary angiography

BACKGROUND

The aim of the study was to compare the detection of clinically significant coronary artery stenosis using a magnetic resonance 3-dimensional (3D) breath-hold true fast imaging with steady-state precession (trueFISP) sequence with conventional coronary angiography.

METHODS

Twenty-nine patients who were scheduled to undergo or had recently undergone diagnostic conventional coronary angiogram participated in this study. The left main, left anterior descending, left circumflex, and right coronary arteries were studied using the 3D breath-hold trueFISP technique. Each artery was imaged with 1 acquisition in 16 to 32 heartbeats. The image quality, vessel length, and presence or absence of stenosis were evaluated. A score of 1 to 3 (1 = noninterpretable, 2 = good, 3 = excellent) was used to assess image quality. The sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of magnetic resonance angiography in detecting significant coronary artery stenosis (> 50% luminal narrowing) on conventional coronary angiogram were calculated.

RESULTS

Of 116 vessels, 108 were assessed in 29 patients. Twenty vessels that had image quality score of 1 were excluded from further evaluation. The mean lengths of vessels visualized were the following: left anterior descending 3.6 cm, left circumflex 3.4 cm, and right coronary 6.6 cm. The entire length of the left main coronary artery was visualized. For the visualized arterial segments, the sensitivity, specificity, accuracy, positive predictive value, and negative predictive value for detecting significant coronary artery stenosis were 92.8%, 95.3%, 95.0%, 68.4%, and 99.2%, respectively.

CONCLUSIONS

The 3D breath-hold trueFISP technique, which uses the endogenous contrast of blood, is potentially useful in ruling out significant coronary artery stenosis but not yet sensitive enough as a screening tool.

Non-invasive coronary angiography with multi-detector computed tomography: comparison to conventional X-ray angiography

Selective coronary angiography introduced clinical coronary imaging in the late 1950s. The angiographic identification of high-grade coronary lesions in patients with acute and chronic symptomatic coronary artery disease (CAD) led to the development of surgical and percutaneous coronary revascularization. However, the fact that CAD remains the major cause of death in North America and Europe demonstrates the need for novel, complementary diagnostic strategies. These are driven by the need to characterize both increasingly advanced disease stages but also early, asymptomatic disease development. Complex revascularization techniques for patients with advanced disease stages will initiate a growing demand for 3-dimensional coronary imaging and integration of imaging modalities with new mechanical therapeutic devices. An emerging focus is atherosclerosis imaging with the goal to identify subclinical disease stages as the basis for pharmacological intervention aimed at disease stabilization or reversal. Non-invasive coronary imaging with coronary multidetector computed tomographic angiography (MDCTA) allows both assessment of luminal stenosis and subclinical disease of the arterial wall. Its complementary role in the assessment of early and advanced stages of CAD is increasingly recognized.

CT for imaging coronary artery disease: defining the paradigm for its application

Current generation multidetector-row CT (MDCT) enables high-resolution, motion-free imaging of the heart within a single, short breath-hold. MDCT allows highly accurate and reproducible quantification of coronary artery calcium, a marker that has been used for the detection, exclusion and monitoring of coronary atherosclerosis. The exact role of coronary calcium measurements for cardiac risk stratification remains unclear to date. At contrast enhanced MDCT coronary angiography coronary arteries can be visualized with unprecedented detail. The accurate non-invasive assessment of the presence and degree of coronary artery stenosis appears within reach. With increasing accuracy MDCT enables non-invasive patency evaluation of coronary artery bypass grafts and coronary stents. The cross-sectional nature of contrast enhanced MDCT coronary angiography allows assessment of the vessel wall and may permit more accurate quantification of total atherosclerotic plaque burden than measuring calcified components alone. For a limited time, future technical improvement will be pursued mainly by accelerated gantry rotation speed and additional detector rows. However, novel concepts of CT image acquisition are already under investigation and may bring about yet another quantum leap for medical CT. This communication discusses potential approaches for the beneficial utilization of MDCT for the assessment of patients with known or suspected coronary heart disease.

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.

Assessment of non-ST-segment elevation acute coronary syndromes with cardiac magnetic resonance imaging

OBJECTIVES

The goal of this study was to determine: 1) if the presence of significant coronary stenosis in patients presenting with non-ST-segment elevation acute coronary syndromes (NSTE-ACS) can be predicted by cardiac magnetic resonance (CMR) imaging; and 2) if the analysis of several CMR methods improves its diagnostic yield compared with analysis of individual methods.

BACKGROUND

With modern acquisition techniques, several CMR methods for the assessment of coronary artery disease (CAD) can be combined in a single noninvasive scanning session. Such a multicomponent CMR examination has not previously been applied to a large patient population, in particular those with a high prevalence of CAD in an acute situation.

METHODS

Sixty-eight patients presenting with NSTE-ACS underwent CMR imaging of myocardial function, perfusion (rest and adenosine-stress), viability (by late contrast enhancement), and coronary artery anatomy. Visual analysis of CMR was carried out. First, all CMR data were reviewed in combination ("comprehensive analysis"). In further separate analyses, each CMR method was analyzed individually. The ability of CMR to detect coronary stenosis >/=70% on X-ray angiography was determined.

RESULTS

Comprehensive CMR analysis yielded a sensitivity of 96% and a specificity of 83% to predict the presence of significant coronary stenosis and was more accurate than analysis of any individual CMR method; CMR was significantly more sensitive and accurate than the Thrombolysis In Myocardial Infarction risk score (p < 0.001).

CONCLUSIONS

Cardiac magnetic resonance imaging accurately predicts the presence of significant CAD in patients with NSTE-ACS. In this study, a comprehensive analysis of several CMR methods improved the accuracy of the test.

Improved three-dimensional free-breathing coronary magnetic resonance angiography using gadocoletic acid (B-22956) for intravascular contrast enhancement

PURPOSE

To evaluate gadocoletic acid (B-22956), a gadolinium-based paramagnetic blood pool agent, for contrast-enhanced coronary magnetic resonance angiography (MRA) in a Phase I clinical trial, and to compare the findings with those obtained using a standard noncontrast T2 preparation sequence.

MATERIALS AND METHODS

The left coronary system was imaged in 12 healthy volunteers before B-22956 application and 5 (N = 11) and 45 (N = 7) minutes after application of 0.075 mmol/kg of body weight (BW) of B-22956. Additionally, imaging of the right coronary system was performed 23 minutes after B-22956 application (N = 6). A three-dimensional gradient echo sequence with T2 preparation (precontrast) or inversion recovery (IR) pulse (postcontrast) with real-time navigator correction was used. Assessment of the left and right coronary systems was performed qualitatively (a 4-point visual score for image quality) and quantitatively in terms of signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), vessel sharpness, visible vessel length, maximal luminal diameter, and the number of visible side branches.

RESULTS

Significant (P < 0.01) increases in SNR (+42%) and CNR (+86%) were noted five minutes after B-22956 application, compared to precontrast T2 preparation values. A significant increase in CNR (+40%, P < 0.05) was also noted 45 minutes postcontrast. Vessels (left anterior descending artery (LAD), left coronary circumflex (LCx), and right coronary artery (RCA)) were also significantly (P < 0.05) sharper on postcontrast images. Significant increases in vessel length were noted for the LAD (P < 0.05) and LCx and RCA (both P < 0.01), while significantly more side branches were noted for the LAD and RCA (both P < 0.05) when compared to precontrast T2 preparation values.

CONCLUSION

The use of the intravascular contrast agent B-22956 substantially improves both objective and subjective parameters of image quality on high-resolution three-dimensional coronary MRA. The increase in SNR, CNR, and vessel sharpness minimizes current limitations of coronary artery visualization with high-resolution coronary MRA.

Imagerie non invasive des artères coronaires : TDM et IRM

The advent of helical multidetector CT has significantly modified several traditional clinical approaches to cardiovascular diagnosis. The current availability of rapid image acquisition has provided the basis for investigating direct imaging in real time of cardiac structures using CT. Application of thin-section submillimetric image acquisitions to three-dimensional (3D) reconstruction algorithms produces 3D data sets from which images of the coronary arteries may be obtained in any anatomic plane. The advantage of the submillimetric isotropic spatial resolution is partly offset by reduced temporal resolution as well as reduced contrast resolution compared to MRI. This lack in contrast sensitivity prevents accurate perfusion imaging and restricts the clinical use to coronary artery imaging. Moreover, the large amount of iodinated contrast medium injected has potential nephrotoxic effects, which can be deleterious if coronary artery angiography must to be performed. On the other hand, MRI has less spatial resolution, and acquisitions must be performed in the plane of each coronary artery because of reduced volume coverage. Both techniques play a role in the non-invasive assessment of coronary artery disease, by providing complementary information already useful in a growing number of clinical situations.

Gadopentetate dimeglumine-enhanced three-dimensional MR-angiography: dosing, safety, and efficacy

Noninvasiveness, inherent three-dimensionality allowing reformations in any desired plane, and safe contrast agents, coupled with high diagnostic accuracy have driven the rise in popularity of contrast-enhanced MR angiography (CE-MRA) within the medical community. Reflecting its dominant market share as a paramagnetic contrast agent, gadopentetate dimeglumine (Gd-DTPA) has been used for the majority of clinically-performed MRA exams. Over the period January 1994 to February 2002, a total of 172 original studies describing the use of gadolinium-enhanced MRA in more than three human subjects were identified. Of these, 117 described the use of Gd-DTPA as the contrast agent for MRA. A total of 4046 subjects who received Gd-DTPA for MRA are described in these studies. Analysis of these data demonstrate Gd-DTPA to be a safe contrast agent for MRA when applied in a dose ranging from 0.1 to 0.3 mmol/kg of bodyweight. The documented clinical results show Gd-DTPA to be efficacious in the assessment of the arterial system. The effectiveness of Gd-DTPA-enhanced MRA extends beyond the detection, localization, and characterization of arterial disease, and encompasses choice and planning of appropriate therapy, as well as evaluation of therapeutic effectiveness.

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.

Coronary MR angiography with steady-state free precession: individually adapted breath-hold technique versus free-breathing technique

PURPOSE

To compare image quality and coronary artery stenosis detection with breath-hold (BH) and free-breathing navigator-gated (NAV) coronary magnetic resonance (MR) angiography performed with the same imaging sequence (steady-state free precession) and identical spatial resolution in patients suspected of having coronary artery disease.

MATERIALS AND METHODS

Forty consecutive patients suspected of having coronary artery disease underwent steady-state free precession MR imaging of the left or the right coronary artery twice. Correction of breathing motion was performed once with NAV and again with BH. Maximal BH duration and coronary artery rest period were individually determined, and duration of data acquisition was adapted (parallel imaging with different sensitivity encoding factors was used). Quantitative analysis of coronary MR angiography data was performed with multiplanar reformatting software to determine visual score for image quality, vessel sharpness, visible vessel length, and number of visible side branches. Diagnostic accuracy for detection of coronary stenosis of 50% or greater was determined in comparison with results of conventional invasive angiography. The two techniques were compared regarding differences in angiographic parameters with paired Student t testing. chi(2) or Fisher exact testing was used when appropriate.

RESULTS

More coronary artery segments were assessable with NAV than with BH MR angiography (254 [79.4%] vs 143 [44.7%] of 320 segments). Overall sensitivity and specificity with NAV were 72% (26 of 36 segments) and 91.7% (200 of 218 segments), versus 63% (12 of 19 segments) and 82.3% (102 of 124 segments) with BH; NAV enabled correct diagnosis in 13% more segments. BH yielded nondiagnostic images in 14 patients, while NAV yielded diagnostic images in all patients. When these 14 patients were excluded, there was a significant increase in visual score for left (3.0 vs 2.4, P <.01) and right (3.3 vs 3.0, P <.05) coronary arteries and no significant difference in vessel sharpness but significant improvement in visible vessel length in left coronary artery (85.9 vs 71.4 mm, P =.003) and number of visible side branches in left (4.9 vs 3.9, P =.04) and right (2.8 vs 2.4, P =.04) coronary arteries on NAV images as compared with BH images.

CONCLUSION

Free-breathing NAV was superior to BH coronary MR angiography in terms of image quality and diagnostic accuracy of stenosis detection.

CT of coronary artery disease

The socioeconomic importance of heart disease provides considerable motivation for development of radiologic tools for noninvasive imaging of the coronary arteries. Current computed tomographic (CT) techniques combine high speed and spatial resolution with sophisticated electrocardiographic synchronization and robustness of use. Application of these modalities for evaluation of coronary artery disease is a topic of active current research. Coronary artery calcium measurements with different CT techniques have been used for determining the risk of coronary events, but the exact role of this marker for cardiac risk stratification remains unclear pending results of population-based studies. Contrast material-enhanced CT coronary angiography has become an established clinical indication for some scenarios (eg, coronary artery anomalies, bypass patency, surgical planning). With current technology, the accuracy of CT coronary angiography for detection of coronary artery stenoses appears promising enough to warrant pursuit of this application, but sensitivity is still not high enough for routine diagnostic needs. The high negative predictive value of a normal CT coronary angiogram, however, may be useful for reliable exclusion of coronary artery stenosis. The cross-sectional nature of CT may allow noninvasive assessment of the coronary artery wall. Use of contrast-enhanced CT coronary angiography for detection, characterization, and quantification of atherosclerotic changes and total disease burden in coronary arteries as a potential tool for cardiac risk stratification is currently being investigated.

Contrast-enhanced MR imaging of the heart: overview of the literature

The use of magnetic resonance (MR) imaging for cardiac diagnosis is expanding, aided by the administration of paramagnetic contrast agents for a growing number of clinical applications. This overview of the literature considers the principles and applications of cardiac MR imaging with an emphasis on the use of contrast media. Clinical applications of contrast material-enhanced MR imaging include the detection and characterization of intracardiac masses, thrombi, myocarditis, and sarcoidosis. Suspected myocardial ischemia and infarction, respectively, are diagnosed by using dynamic first-pass and delayed contrast enhancement. Promising new developments include blood pool contrast media, labeling of myocardial precursor cells, and contrast-enhanced imaging at very high fields.

Noninvasive imaging of coronary arteries: current and future role of multi-detector row CT

While invasive imaging techniques, especially selective conventional coronary angiography, will remain vital to planning and guiding catheter-based and surgical treatment of significantly stenotic coronary lesions, the comprehensive and serial assessment of asymptomatic or minimally symptomatic stages of coronary artery disease (CAD) for preventive purposes will eventually need to rely on noninvasive imaging techniques. Cardiovascular imaging with tomographic modalities, including computed tomography (CT) and magnetic resonance imaging, has great potential for providing valuable information. This review article will describe the current and future role of cardiac CT, and in particular that of multi-detector row CT, for imaging of atherosclerotic and other pathologic changes of the coronary arteries. It will describe how tomographic coronary imaging may eventually supplement traditional angiographic techniques in understanding the patterns of atherosclerotic CAD development.

Multisegment and halfscan reconstruction of 16-slice computed tomography for detection of coronary artery stenoses

RATIONALE AND OBJECTIVES

To compare the diagnostic accuracy and image quality of 2 reconstruction algorithms (multisegment and halfscan) for computed tomography (CT) coronary angiography in patients without beta-blocker medication.

MATERIALS AND METHODS

Thirty-four patients with 42 significant coronary stenoses in 136 main coronary branches were examined using a 16-slice CT scanner (Aquilion, Toshiba, Otawara, Japan). Twenty-seven patients (79%) had heart rates above 65 beats/min.

RESULTS

Without exclusion of branches the sensitivity, specificity, accuracy, and rate of nonassessable segments with multisegment versus halfscan reconstruction were 88 versus 74%, 91 versus 71%, 90 versus 72%, and 2 versus 21% (P < 0.01), respectively. Multisegment reconstruction improved the average vessel length free of motion artifacts by 56% compared with halfscan reconstruction (P < 0.01). Image quality in terms of vessel continuity and visibility of side branches (P < 0.005) was significantly better using multisegment reconstruction.

CONCLUSIONS

Multisegment reconstruction has superior diagnostic accuracy and image quality compared with halfscan reconstruction in patients with normal heart rates.

The use of CTA in the chest pain center: a perspective

Suitable imaging methods to reliably rule out coronary artery disease as the underlying condition might be beneficially applied in the workup of patients with acute chest pain. The temporal and spatial resolution of computed tomgraphy and electron beam computed tomography has seen continuous improvements over the past years. Current scanner generations permit relatively reliable visualization of the coronary arteries and several studies have demonstrated a high negative predictive value to rule out coronary artery stenoses. Even though applications in the context of acute coronary syndromes have not yet been specifically evaluated, it seems likely that computed tomography imaging may develop into a tool that can be integrated into the workflow in chest pain centers once appropriate studies have been performed.

Simple detection of occluded coronary artery using retrograde flow in septal branch and left anterior descending coronary artery by transthoracic doppler echocardiography at rest

BACKGROUND

We hypothesized that coronary flow assessment by transthoracic Doppler echocardiography (TTDE) for both intramyocardial collateral channel and epicardial channels would be useful for identifying occluded left anterior descending coronary artery (LAD).

METHODS

We assessed flow direction in the LAD and the septal branch (SEP) by TTDE in 302 consecutive patients who were suggested to have ischemic heart disease. We defined antegrade LAD flow as a direction from the base to the apex of the left ventricle in the anterior groove area, and antegrade SEP flow as a direction from anterior to inferior in the anterior interventricular septum. By contrast, we defined retrograde LAD and SEP flow as an inverse direction. We performed angiography on all patients.

RESULTS

Retrograde flow was detected in 22 (LAD, 16 patients; SEP, 6 patients) of 23 patients with occluded LAD, and antegrade flow was detected in all patients without occluded LAD. The sensitivity and specificity for identification of occluded LAD by TTDE were 96% and 100%, respectively.

CONCLUSIONS

Assessment of flow direction in both LAD and SEP by TTDE is a useful method in identification of occluded LAD.

Coronary artery magnetic resonance angiography

Coronary magnetic resonance angiography (coronary MRA) continues to advance rapidly from both a technical and clinical perspective. Coronary MRA has benefited directly from improvements in spatial resolution, contrast definition, and advances in motion correction, which have furthered its routine use in evaluating coronary artery bypass grafts and anomalous coronary arteries. Work in refining the techniques for more accurate identification of coronary artery disease (CAD) continues, with advances in navigator-gated and breath-hold motion correction techniques, novel k-space strategies (e.g., spiral and radial k-space filling), development and application of intravascular contrast agents, and imaging at higher field strengths. Ultimately, these developments may lead to the routine application of coronary MRA as a screening tool for CAD. This article reviews the development of coronary MRA, discusses the requirements and tools necessary for optimal visualization of the coronary arteries, and describes the application of coronary MRA to acquired and congenital CAD.

Clinical utility of computed tomography and magnetic resonance techniques for noninvasive coronary angiography

OBJECTIVE

The purpose of this study was to provide a comprehensive review of the literature relating to electron beam angiography (EBA), magnetic resonance angiography, and spiral computed tomography, currently the three most promising noninvasive methods to visualize obstructions in the coronary tree.

BACKGROUND

Given the high costs and invasiveness of coronary angiography, there is increased interest in noninvasive coronary angiography, which has made great strides to become a clinically useful tool to augment conventional coronary angiography (CCA).

METHODS

MEDLINE searches were performed to include all articles related to noninvasive angiography utilizing either magnetic resonance imaging (MRI), multi-row detector spiral computed tomography (MDCT), and electron beam tomography (EBT). Weighted analysis was performed to define the published sensitivity and specificity for each technique.

RESULTS

Electron beam angiography (EBA) provides an overall sensitivity of 87% and specificity of 91% for the detection of obstructive coronary artery disease (CAD). Four-level MDCT data demonstrated an overall sensitivity of 59% and specificity of 89%, with higher accuracy in two recent studies of 16-level detector devices. Magnetic resonance angiography demonstrated sensitivity for detection of obstructive CAD of 77% and specificity of 71%.

CONCLUSIONS

Noninvasive coronary angiography is a rapidly developing technique and currently not an alternative to CCA in all cases. All three methods are currently used clinically in certain centers with appropriate expertise. Selective use should prove both cost-effective and provide a safer, less-invasive method for patients to determine the need for medical versus revascularization therapy.

Clinical results of minimally invasive coronary angiography using computed tomography

Fast, high-resolution CT techniques, such as EBCT and MDCT permit imaging of the coronary arteries. Continuous improvements in the capabilities of both technologies for visualization of the coronary lumen and detection of coronary artery stenoses are being made. Image quality currently is not robust enough in all patients to consider non-invasive coronary angiography by EBCT and MDCT a routine clinical tool. In selected patients and carefully performed, however, they show promise as means to exclude the presence of coronary artery stenoses in a non-invasive fashion. This may become a beneficial and important application of these technologies. Other possible applications pertain to smaller patient subsets, such as patients with anomalous coronary arteries, fistulas or aneurysms. The development of techniques to visualize non-calcified plaque is interesting with respect to assessment of coronary risk, but this requires further investigation.

Three-dimensional navigator coronary MRA with the aid of a blood pool agent in pigs: Improved image quality with inclusion of the contrast agent first-pass

PURPOSE

To evaluate the effect of including the first-pass of a blood pool agent (BPA) on the image quality of three-dimensional navigator coronary MRA.

MATERIALS AND METHODS

A pig model was used to perform: 1) T1 simulation of the BPA, based on actual blood samples, and 2) BPA-enhanced three-dimensional navigator coronary MRA, with or without inclusion of the first-pass of the BPA. The acquisitions with inclusion of the first-pass were timed with the use of a test bolus. The acquisitions without first-pass were started one minute after bolus injection (steady-state). A gradient echo acquisition technique with centric k-space sampling was applied. Comparison of both acquisitions was based on determination of contrast-to-noise ratio (CNR), signal-to-noise ratio (SNR), and vessel length.

RESULTS

T1 simulation shows a distinct T1 reduction during first-pass (to a level below 50 msec), increasing to 190 msec during steady-state. Images obtained with first-pass inclusion showed improved CNR (8.6 +/- 1.7 vs. 4.5 +/- 1.8), SNR (11.9 +/- 1.6 vs. 7.4 +/- 2.0), and vessel length (99.2 +/- 10.9 mm vs. 60.5 +/- 21.8 mm) as compared to the acquisitions during steady-state only (all: P< 0.05).

CONCLUSION

The image quality of three-dimensional navigator coronary MRA combined with a gadolinium BPA in pigs is improved when starting the image acquisition during first-pass of the bolus.

Relation of thoracic aorta calcification on computed tomography and coronary risk factors to obstructive coronary artery disease on angiography

The aim of this study was to investigate whether thoracic aorta calcification (TAC) on computed tomography (CT) and coronary risk factors had any correlation with obstructive coronary artery disease (CAD) on angiography. A total of 225 consecutive Japanese patients underwent both thoracic conventional helical CT and coronary angiography. The thoracic aorta was divided into 4 locations according to the aortic anatomy (inner curve of the aortic arch, aortic arch but not on the inner curve, ascending aorta, and thoracic descending aorta). The classified TAC and coronary risk factors were evaluated for the presence or absence of obstructive CAD. TAC was detected in 185 patients; 141 of 225 patients had significant obstructive CAD. All of the 13 patients with no TAC and no coronary risk factors had no CAD. The obstructive CAD rate with 1 thoracic calcified location and with no, 1, or 2 coronary risk factors was 10%, 58%, and 90%, respectively, and each showed a significant difference (p < 0.0001). The combinations of TAC and coronary risk factors with obstructive CAD were 1 or 2 thoracic calcified locations with 3 coronary risk factors, and 3 thoracic calcified locations with more than 2 coronary risk factors. Increasing thoracic calcified locations and increasing coronary risk factors indicated a higher likelihood of CAD.

Simultaneous magnetic resonance gadolinium-enhanced 2D perfusion and 3D angiographic imaging

A method was implemented and tested that allows the simultaneous acquisition of magnetic resonance 2D slice selective perfusion and 3D angiographic data during a single bolus injection of a contrast agent. High quality contrast-enhanced perfusion images and angiograms of the lung, kidney and heart were obtained in healthy volunteers. Combined perfusion and angiography provided additional information with an acceptable increase in acquisition time. No image artifacts were attributed to the technique. The combined information may be useful in detecting, as well as characterizing, vascular abnormalities.