Coronary artery anomalies and variants: technical feasibility of assessment with coronary MR angiography at 3 T

Motion robust coronary MR angiography using zigzag centric ky-kz trajectory and high-resolution deep learning reconstruction

PURPOSE

To develop a new MR coronary angiography (MRCA) technique by employing a zigzag fan-shaped centric ky-kz k-space trajectory combined with high-resolution deep learning reconstruction (HR-DLR).

METHODS

All imaging data were acquired from 12 healthy subjects and 2 patients using two clinical 3-T MR imagers, with institutional review board approval. Ten healthy subjects underwent both standard 3D fast gradient echo (sFGE) and centric ky-kz k-space trajectory FGE (cFGE) acquisitions to compare the scan time and image quality. Quantitative measures were also performed for signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) as well as sharpness of the vessel. Furthermore, the feasibility of the proposed cFGE sequence was assessed in two patients. For assessing the feasibility of the centric ky-kz trajectory, the navigator-echo window of a 30-mm threshold was applied in cFGE, whereas sFGE was applied using a standard 5-mm threshold. Image quality of MRCA using cFGE with HR-DLR and sFGE without HR-DLR was scored in a 5-point scale (non-diagnostic = 1, fair = 2, moderate = 3, good = 4, and excellent = 5). Image evaluation of cFGE, applying HR-DLR, was compared with sFGE without HR-DLR. Friedman test, Wilcoxon signed-rank test, or paired t tests were performed for the comparison of related variables.

RESULTS

The actual MRCA scan time of cFGE with a 30-mm threshold was acquired in less than 5 min, achieving nearly 100% efficiency, showcasing its expeditious and robustness. In contrast, sFGE was acquired with a 5-mm threshold and had an average scan time of approximately 15 min. Overall image quality for MRCA was scored 3.3 for sFGE and 2.7 for cFGE without HR-DLR but increased to 3.6 for cFGE with HR-DLR and (p < 0.05). The clinical result of patients obtained within 5 min showed good quality images in both patients, even with a stent, without artifacts. Quantitative measures of SNR, CNR, and sharpness of vessel presented higher in cFGE with HR-DLR.

CONCLUSION

Our findings demonstrate a robust, time-efficient solution for high-quality MRCA, enhancing patient comfort and increasing clinical throughput.

Similarity-driven motion-resolved reconstruction for ferumoxytol-enhanced whole-heart MRI in congenital heart disease

A similarity-driven multi-dimensional binning algorithm (SIMBA) reconstruction of free-running cardiac magnetic resonance imaging data was previously proposed. While very efficient and fast, the original SIMBA focused only on the reconstruction of a single motion-consistent cluster, discarding the remaining data acquired. However, the redundant data clustered by similarity may be exploited to further improve image quality. In this work, we propose a novel compressed sensing (CS) reconstruction that performs an effective regularization over the clustering dimension, thanks to the integration of inter-cluster motion compensation (XD-MC-SIMBA). This reconstruction was applied to free-running ferumoxytol-enhanced datasets from 24 patients with congenital heart disease, and compared to the original SIMBA, the same XD-MC-SIMBA reconstruction but without motion compensation (XD-SIMBA), and a 5D motion-resolved CS reconstruction using the free-running framework (FRF). The resulting images were compared in terms of lung-liver and blood-myocardium sharpness, blood-myocardium contrast ratio, and visible length and sharpness of the coronary arteries. Moreover, an automated image quality score (IQS) was assigned using a pretrained deep neural network. The lung-liver sharpness and blood-myocardium sharpness were significantly higher in XD-MC-SIMBA and FRF. Consistent with these findings, the IQS analysis revealed that image quality for XD-MC-SIMBA was improved in 18 of 24 cases, compared to SIMBA. We successfully tested the hypothesis that multiple motion-consistent SIMBA clusters can be exploited to improve the quality of ferumoxytol-enhanced cardiac MRI when inter-cluster motion-compensation is integrated as part of a CS reconstruction.

Coronary Artery Fistulas: A Review of the Current and Future Roles of Imaging

Coronary artery fistulas are uncommon but clinically important entities that may produce symptoms and significant complications such as angina, myocardial infarction, coronary artery aneurysm formation, and congestive heart failure. Multiple fistula types have been recognized, and classification uses factors such as etiology, coronary artery origin, and drainage site. Both invasive and noninvasive imaging play an important role in the management and treatment of these patients, and often times, more than one modality is necessary for comprehensive evaluation of coronary fistulas. Recent advances in both functional and anatomic imaging will likely also play a growing role in fistula evaluation. The purpose of this article is to review the classification, pathophysiology, clinical presentations, imaging findings, treatment, and future imaging directions of coronary artery fistulas.

Diagnostic Accuracy of Noncontrast Self-navigated Free-breathing MR Angiography versus CT Angiography: A Prospective Study in Pediatric Patients with Suspected Anomalous Coronary Arteries

RATIONALE AND OBJECTIVES

To evaluate the diagnostic accuracy of a prototype noncontrast, free-breathing, self-navigated 3D (SN3D) MR angiography (MRA) technique for the assessment of coronary artery anatomy in children with known or suspected coronary anomalies, using CT angiography (CTA) as the reference standard.

MATERIALS AND METHODS

Twenty-one children (15 male, 12.3 ± 2.6 years) were prospectively enrolled between July 2014 and August 2016 in this IRB-approved, HIPAA-compliant study. Patients underwent same-day unenhanced SN3D-MRA and contrast-enhanced CTA. Two observers rated the visualization of coronary artery segments and diagnostic confidence on a 3-point scale and assessed coronary arteries for anomalous origin, as well as interarterial and intramural course. Sensitivity, specificity, positive (PPV) and negative predictive values (NPV) of SN3D-MRA for the detection of coronary artery abnormalities were calculated. Interobserver agreement was assessed using Intraclass Correlation Coefficients (ICC).

RESULTS

Fourteen children showed coronary artery abnormalities on CTA. The visualization of coronary segments was rated significantly higher for CTA compared to MRA (p <0.015), except for the left main coronary artery (p = 0.301), with good to excellent interobserver agreement (ICC = 0.62-0.94). Diagnostic confidence was higher for CTA (p = 0.046). Sensitivity, specificity, PPV, and NPV of MRA were 92%, 92%, 96%, and 87% for the detection of coronary artery anomalies, 85%, 85%, 74%, and 92% for high origin, 71%, 92%, 82%, and 87% for interarterial, and 41%, 96%, 87%, and 80% for intramural course.

CONCLUSIONS

Noncontrast SN3D-MRA is highly accurate for the detection of coronary artery anomalies in pediatric patients while diagnostic confidence and coronary artery visualization remain superior with CTA.

Right Coronary Artery-Superior Vena Cava Fistula Manifesting as NSTEMI: Case Report, Review of Imaging, and Summary of Guidelines

Coronary artery fistulas (CAFs) represent a spectrum of abnormal connections between a coronary artery and another coronary artery, vein, or major blood vessel, known as coronary-vascular fistulas, or between a coronary artery and a cardiac chamber, known as coronary-cameral fistulas. While CAFs generally remain asymptomatic into the fifth decade of adult life, they can present with a diverse symptomatic profile, typically with angina from abnormal myocardial perfusion, or in the setting of larger fistulas, as right- or left-heart failure from pulmonary or left ventricular circulatory overload. CAFs rarely manifest as myocardial infarction in the absence of thrombosis within the fistula. When clinically suspected based on a continuous murmur on physical exam or an accidental finding on radiology, computed tomography angiography (CTA) and coronary angiography are the preferred diagnostic imaging modalities. Fistula anatomic and patient specific characteristics guide clinical decisions on transcatheter or surgical management strategies. We present the case of a right coronary artery-superior vena cava fistula manifesting as a non-ST elevation myocardial infarction. We also present a review of the imaging techniques available for evaluation of CAFs, and a summary of the major national and international cardiology society guidelines on the diagnosis and management of CAFs.

Computational Assessment of Blood Flow Heterogeneity in Peritoneal Dialysis Patients' Cardiac Ventricles

Dialysis prolongs life but augments cardiovascular mortality. Imaging data suggests that dialysis increases myocardial blood flow (BF) heterogeneity, but its causes remain poorly understood. A biophysical model of human coronary vasculature was used to explain the imaging observations, and highlight causes of coronary BF heterogeneity. Post-dialysis CT images from patients under control, pharmacological stress (adenosine), therapy (cooled dialysate), and adenosine and cooled dialysate conditions were obtained. The data presented disparate phenotypes. To dissect vascular mechanisms, a 3D human vasculature model based on known experimental coronary morphometry and a space filling algorithm was implemented. Steady state simulations were performed to investigate the effects of altered aortic pressure and blood vessel diameters on myocardial BF heterogeneity. Imaging showed that stress and therapy potentially increased mean and total BF, while reducing heterogeneity. BF histograms of one patient showed multi-modality. Using the model, it was found that total coronary BF increased as coronary perfusion pressure was increased. BF heterogeneity was differentially affected by large or small vessel blocking. BF heterogeneity was found to be inversely related to small blood vessel diameters. Simulation of large artery stenosis indicates that BF became heterogeneous (increase relative dispersion) and gave multi-modal histograms. The total transmural BF as well as transmural BF heterogeneity reduced due to large artery stenosis, generating large patches of very low BF regions downstream. Blocking of arteries at various orders showed that blocking larger arteries results in multi-modal BF histograms and large patches of low BF, whereas smaller artery blocking results in augmented relative dispersion and fractal dimension. Transmural heterogeneity was also affected. Finally, the effects of augmented aortic pressure in the presence of blood vessel blocking shows differential effects on BF heterogeneity as well as transmural BF. Improved aortic blood pressure may improve total BF. Stress and therapy may be effective if they dilate small vessels. A potential cause for the observed complex BF distributions (multi-modal BF histograms) may indicate existing large vessel stenosis. The intuitive BF heterogeneity methods used can be readily used in clinical studies. Further development of the model and methods will permit personalized assessment of patient BF status.

Utility of late gadolinium enhancement in pediatric cardiac MRI

Late gadolinium enhancement (LGE) cardiac magnetic resonance (MR) imaging sequence is increasingly used in the evaluation of pediatric cardiovascular disorders, and although LGE might be a normal feature at the sites of previous surgeries, it is pathologically seen as a result of extracellular space expansion, either from acute cell damage or chronic scarring or fibrosis. LGE is broadly divided into ischemic and non-ischemic patterns. LGE caused by myocardial infarction occurs in a vascular distribution and always involves the subendocardial portion, progressively involving the outer regions in a waveform pattern. Non-ischemic cardiomyopathies can have a mid-myocardial (either linear or patchy), subepicardial or diffuse subendocardial distribution. Idiopathic dilated cardiomyopathy can have a linear mid-myocardial pattern, while hypertrophic cardiomyopathy can have fine, patchy enhancement in hypertrophied and non-hypertrophied segments as well as right ventricular insertion points. Myocarditis and sarcoidosis have a mid-myocardial or subepicardial pattern of LGE. Fabry disease typically affects the basal inferolateral segment while Danon disease typically spares the septum. Pericarditis is characterized by diffuse or focal pericardial thickening and enhancement. Thrombus, the most common non-neoplastic cardiac mass, is characterized by absence of enhancement in all sequences, while neoplastic masses show at least some contrast enhancement, depending on the pathology. Regardless of the etiology, presence of LGE is associated with a poor prognosis. In this review, we describe the technical modifications required for performing LGE cardiac MR sequence in children, review and illustrate the patterns of LGE in children, and discuss their clinical significance.

Simulated annealing approach to vascular structure with application to the coronary arteries

Do the complex processes of angiogenesis during organism development ultimately lead to a near optimal coronary vasculature in the organs of adult mammals? We examine this hypothesis using a powerful and universal method, built on physical and physiological principles, for the determination of globally energetically optimal arterial trees. The method is based on simulated annealing, and can be used to examine arteries in hollow organs with arbitrary tissue geometries. We demonstrate that the approach can generate in silico vasculatures which closely match porcine anatomical data for the coronary arteries on all length scales, and that the optimized arterial trees improve systematically as computational time increases. The method presented here is general, and could in principle be used to examine the arteries of other organs. Potential applications include improvement of medical imaging analysis and the design of vascular trees for artificial organs.

Coronary anomalies: what the radiologist should know

Coronary anomalies comprise a diverse group of malformations, some of them asymptomatic with a benign course, and the others related to symptoms as chest pain and sudden death. Such anomalies may be classified as follows: 1) anomalies of origination and course; 2) anomalies of intrinsic coronary arterial anatomy; 3) anomalies of coronary termination. The origin and the proximal course of anomalous coronary arteries are the main prognostic factors, and interarterial course or a coronary artery is considered to be malignant due its association with increased risk of sudden death. Coronary computed tomography angiography has become the reference method for such an assessment as it detects not only anomalies in origination of these arteries, but also its course in relation to other mediastinal structures, which plays a relevant role in the definition of the therapeutic management. Finally, it is essential for radiologists to recognize and characterize such anomalies.

Beyond ultrasound: advances in multimodality cardiac imaging

The rapid technological evolution accomplished in noninvasive cardiac imaging techniques over the past few decades has provided physicians with a large armamentarium for the evaluation of patients with known or suspected coronary heart disease. Noninvasive assessment of coronary artery calcium or noninvasive coronary angiography may be performed using computed tomography or magnetic resonance imaging. These techniques evaluate the presence of atherosclerosis rather than ischemia. Conversely, nuclear cardiology is the most widely used noninvasive approach for the assessment of myocardial perfusion and function. These techniques coupled with the development of dedicated image fusion software packages to merge data sets from different modalities have paved the way for hybrid imaging. This article provides a description of the available noninvasive imaging techniques in the assessment of coronary anatomy, myocardial perfusion, and cardiac function in patients with known or suspected coronary heart disease.

Optimization of free-breathing whole-heart 3-dimensional cardiac magnetic resonance imaging at 3 tesla to identify coronary vein anatomy and to compare with multidetector computed tomography

OBJECTIVE

This study optimizes use of 3-T magnetic resonance imaging (MRI) to delineate coronary venous anatomy and compares 3-T MRI with multidetector computed tomography (MDCT) measurements.

METHODS

The study population included 37 consecutive subjects (22 men, 19-71 years old). Whole-heart contrast-enhanced MRI images at 3 T were acquired using segmented k-space gradient echo with inversion recovery prepared technique. The MDCT images were obtained using nonionic iodinated contrast.

RESULTS

The coronary sinus and great cardiac, posterior interventricular, and anterior interventricular veins were visualized in 100% of cases by both MRI and MDCT. Detection of the posterior vein of the left ventricle and the left marginal vein by MRI was 97% and 81%, respectively. Bland-Altman plots showed agreement in ostial diameter measured by both modalities with correlation coefficients ranging from 0.5 to 0.76. Vein length and distances also agreed closely.

CONCLUSIONS

Free-breathing whole-heart 3-dimensional MRI at 3 T provides high-spatial-resolution images and could offer an alternative imaging technique instead of MDCT scans.

2014 korean guidelines for appropriate utilization of cardiovascular magnetic resonance imaging: a joint report of the korean society of cardiology and the korean society of radiology

Cardiac magnetic resonance (CMR) imaging is now widely used in several fields of cardiovascular disease assessment due to recent technical developments. CMR can give physicians information that cannot be found with other imaging modalities. However, there is no guideline which is suitable for Korean people for the use of CMR. Therefore, we have prepared a Korean guideline for the appropriate utilization of CMR to guide Korean physicians, imaging specialists, medical associates and patients to improve the overall medical system performances. By addressing CMR usage and creating these guidelines we hope to contribute towards the promotion of public health. This guideline is a joint report of the Korean Society of Cardiology and the Korean Society of Radiology.

2014 Korean guidelines for appropriate utilization of cardiovascular magnetic resonance imaging: a joint report of the Korean Society of Cardiology and the Korean Society of Radiology

Cardiac magnetic resonance (CMR) imaging is now widely used in several fields of cardiovascular disease assessment due to recent technical developments. CMR can give physicians information that cannot be found with other imaging modalities. However, there is no guideline which is suitable for Korean people for the use of CMR. Therefore, we have prepared a Korean guideline for the appropriate utilization of CMR to guide Korean physicians, imaging specialists, medical associates and patients to improve the overall medical system performances. By addressing CMR usage and creating these guidelines we hope to contribute towards the promotion of public health. This guideline is a joint report of the Korean Society of Cardiology and the Korean Society of Radiology.

Feasibility of coronary artery wall thickening assessment in asymptomatic coronary artery disease using phase-sensitive dual-inversion recovery MRI at 3T

OBJECTIVES

The purpose of this study was to (a) investigate the image quality of phase-sensitive dual-inversion recovery (PS-DIR) coronary wall imaging in healthy subjects and in subjects with known coronary artery disease (CAD) and to (b) investigate the utilization of PS-DIR at 3T in the assessment of coronary artery thickening in subjects with asymptomatic but variable degrees of CAD.

MATERIALS AND METHODS

A total of 37 subjects participated in this institutional review board-approved and HIPAA-compliant study. These included 21 subjects with known CAD as identified on multidetector computed tomography angiography (MDCT). Sixteen healthy subjects without known history of CAD were included. All subjects were scanned using free-breathing PS-DIR magnetic resonance imaging (MRI) for the assessment of coronary wall thickness at 3T. Lumen-tissue contrast-to-noise ratio (CNR), signal-to-noise ratio (SNR) and quantitative vessel parameters including lumen area and wall thickness were measured. Statistical analyses were performed.

RESULTS

PS-DIR was successfully completed in 76% of patients and in 88% of the healthy subjects. Phase-sensitive signed-magnitude reconstruction, compared to modulus-magnitude images, significantly improved lumen-tissue CNR in healthy subjects (26.73±11.95 vs. 14.65±9.57, P<.001) and in patients (21.45±7.61 vs. 16.65±5.85, P<.001). There was no difference in image CNR and SNR between groups. In arterial segments free of plaques, coronary wall was thicker in patients in comparison to healthy subjects (1.74±0.27 mm vs. 1.17±0.14 mm, P<.001), without a change in lumen area (4.51±2.42 mm2 vs. 5.71±3.11mm2, P=.25).

CONCLUSIONS

This is the first study to demonstrate the feasibility of successfully obtaining vessel wall images at 3T using PS-DIR in asymptomatic patients with known variable degrees of CAD as detected by MDCT. This was achieved with a fixed subject-invariant planning of blood signal nulling. With that limitation alleviated, PS-DIR coronary wall MRI is capable of detecting arterial thickening and positive arterial remodeling at 3T in asymptomatic CAD.

Pulmonary vein morphology by free-breathing whole heart magnetic resonance imaging at 3 Tesla versus breathhold multi-detector computed tomography

PURPOSE

To compare pulmonary vein and left atrial anatomy using three-dimensional free-breathing whole-heart magnetic resonance imaging (MR) at 3 Tesla (T) and multi-detector computed tomography (MDCT).

MATERIALS AND METHODS

Thirty-three subjects (19 male, age 49 ± 12 years) underwent free-breathing 3T MR and contrast-enhanced MDCT during inspiratory breath hold. Pulmonary vein parameters (ostial areas, diameters, angles) were measured.

RESULTS

All pulmonary veins and anomalies were identified by 3T MR and by MDCT. The right-sided pulmonary veins were directed more posteriorly, the right superior pulmonary vein more inferiorly, and the right inferior pulmonary vein more superiorly by 3T MR when compared with MDCT. The cross-sectional area, perimeters and minimum diameters of right-sided pulmonary vein ostia were significantly larger by MR, as were the maximum diameters of right and left inferior pulmonary veins. There were no significant differences between techniques in distance to first pulmonary vein branch.

CONCLUSION

Pulmonary vein measurements demonstrated significant differences in angulations and dimensions when 3T MR is compared with MDCT. These differences likely represent hemodynamic and respiratory variation during free-breathing with MR versus breath-holding with MDCT. MR imaging at 3T during free-breathing offers an alternate method to define pulmonary vein and left atrial anatomy without exposure to radiation.

Coronary vessel wall 3-T MR imaging with time-resolved acquisition of phase-sensitive dual inversion-recovery (TRAPD) technique: initial results in patients with risk factors for coronary artery disease

PURPOSE

To develop a technique for time-resolved acquisition of phase-sensitive dual-inversion recovery (TRAPD) coronary vessel wall magnetic resonance (MR) images, to investigate the success rate in coronary wall imaging compared with that of single-frame imaging, and to assess vessel wall thickness in healthy subjects and subjects with risk factors for coronary artery disease (CAD).

MATERIALS AND METHODS

Thirty-eight subjects (12 healthy subjects, 26 subjects with at least one CAD risk factor) provided informed consent for participation in this institutional review board-approved and HIPAA-compliant study. The TRAPD coronary vessel wall imaging sequence was developed and validated with a flow phantom. Time-resolved coronary artery wall images at three to five cine phases were obtained in all subjects. Qualitative and quantitative comparisons were made between TRAPD and conventional single-image wall measurements. Measurement reproducibility also was assessed. Statistical analysis was performed for all comparisons.

RESULTS

The TRAPD sequence successfully restored the negative polarity of lumen signal and enhanced lumen wall contrast on the cine images of the flow phantom and in all subjects. Use of three to five frames increased the success rate of acquiring at least one image of good to excellent quality from 76% in single-image acquisitions to 95% with the TRAPD sequence. The difference in vessel wall thickness between healthy subjects and subjects with CAD risk factors was significant (P < .05) with the TRAPD sequence (1.07 vs 1.46 mm, respectively; 36% increase) compared with single-frame dual inversion-recovery imaging (1.24 vs 1.55 mm, respectively; 25% increase). Intraobserver, interobserver, and interexamination agreement for wall thickness measurement were 0.98, 0.97, and 0.92, respectively.

CONCLUSION

TRAPD imaging of coronary arteries improved arterial wall visualization and quantitative assessment by increasing the success rate of obtaining good- to excellent-quality images and sections orthogonal to the longitudinal axis of the vessel. This also resulted in vessel wall thickness measurements that show a more distinct difference between healthy subjects and those with CAD risk factors.

SUPPLEMENTAL MATERIAL

http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12120068/-/DC1.

Anomalous aortic origin of coronary arteries from the opposite sinus: a critical appraisal of risk

Background

Anomalous aortic origin of the coronary artery (AAOCA) from the opposite sinus of Valsalva with an interarterial course has received much attention due to its association with sudden death in otherwise healthy individuals. AAOCA is relatively common and may have significant public health implications. While our knowledge of its pathophysiology and natural history remains incomplete, an emphasis has been placed on surgical correction.

Discussion

In 2005 we published a review examining the rates of sudden death with AAOCA, as well as complications of surgical management. Evidence now points even more strongly to lower rates of sudden death, while surgical outcomes data now better documents associated risks.

Summary

Armed with this updated information, we agree with the need for a national registry to better track patients with AAOCA. We submit that the risks of surgical management outweigh any benefits in the asymptomatic patient with anomalous right coronary artery, and expectant management should also be strongly considered even in asymptomatic patients with anomalous left coronary artery.

High rate of coronary artery abnormalities in adolescents and young adults infected with human immunodeficiency virus early in life

We completed a cross-sectional study of individuals infected with human immunodeficiency virus in early childhood using cardiac magnetic resonance imaging and magnetic resonance angiography. Coronary artery abnormality (CAA) was defined by the presence of luminal narrowing and irregularity of the coronary vessel wall. More than 50% of participants (14/27) had evidence of CAA. Individuals had a high rate of CAA, suggesting possible early atherosclerosis.

Free-breathing single navigator gated cine cardiac magnetic resonance at 3 T: feasibility study in patients

BACKGROUND

Cardiac magnetic resonance imaging (CMRI) is an important tool to assess cardiac function. However, one of the limitations of CMRI is the need for frequent breath-holding (BH) steps. This may be inconvenient to some patients and limit the use of this modality in patients unable to cooperate because of cognitive reasons or physically incapable of performing the required BH steps. The purpose of this study is to overcome the intrinsic timing and computation limitations of dual-navigator cine imaging and demonstrate the feasibility of free-breathing (FB) cine cardiac left ventricular function with a single-respiratory-navigator gating at 3 T.

RESULTS

Eight participants underwent cine CMRI with both the conventional 2-dimensional cine BH and FB navigator-gated techniques. Scan parameters were identical, except in the FB technique, in which a respiratory navigator and only 2 signal averages were used. Images were scored for quality. Left ventricular end-systolic volume and end-diastolic volume were calculated. The differences in the end-systolic volume and end-diastolic volume assessed by the BH and FB were not statistically significant with P = 0.9 and 0.2, respectively. There was a good agreement between LV volumes with the limits of agreement (± 2 SD = ± 22.36 mL). Image quality score was not significantly different (P = 0.76).

CONCLUSIONS

Free-breathing cine imaging utilizing a single-respiratory-navigator gating technique is comparable to conventional BH technique in both qualitative and quantitative imaging measures. Therefore, the FB cine technique can be used as an alternative for children and patients who are unable to hold their breath.

Clinical applications for cardiovascular magnetic resonance imaging at 3 tesla

Cardiovascular magnetic resonance (CMR) imaging has evolved rapidly and is now accepted as a powerful diagnostic tool with significant clinical and research applications. Clinical 3 Tesla (3 T) scanners are increasingly available and offer improved diagnostic capabilities compared to 1.5 T scanners for perfusion, viability, and coronary imaging. Although technical challenges remain for cardiac imaging at higher field strengths such as balanced steady state free precession (bSSFP) cine imaging, the majority of cardiac applications are feasible at 3 T with comparable or superior image quality to that of 1.5 T. This review will focus on the benefits and limitations of 3 T CMR for common clinical applications and examine areas in development for potential clinical use.

Coronary artery abnormalities in Hyper-IgE syndrome

OBJECTIVE

Hyper-IgE syndrome (HIES) is a rare primary immunodeficiency caused by autosomal dominant STAT3 mutations resulting in recurrent infections and connective tissue abnormalities. Coronary artery abnormalities have been reported infrequently. We aimed to determine the frequency and characteristics of coronary artery abnormalities.

DESIGN

STAT3-mutated HIES patients (n=38), ranging in age from 8 to 57 years, underwent coronary artery imaging by computed tomography or magnetic resonance imaging. Images were evaluated for tortuosity, dilation, and aneurysm. Charts were reviewed for cardiac risk factors. To allow blinded image interpretation, an age- and gender-matched non-HIES group was also evaluated (n=33).

RESULTS

Coronary artery tortuosity or dilation occurred in 70% of HIES patients, with aneurysms present in 37%, incidences much higher than in the literature and in our non-HIES group, in which 21% had tortuosity or dilation and 3% had aneurysms. Hypertension was more common in the HIES group than in the general population and was associated with vessel abnormalities. Atherosclerosis was uncommon and mild.

CONCLUSIONS

Coronary artery aneurysms and tortuosity are common in HIES, despite a paucity of atherosclerosis, suggesting that STAT3 plays an integral role in human vascular remodeling and atherosclerosis.

Contrast-enhanced whole-heart coronary magnetic resonance angiography at 3 T using interleaved echo planar imaging

OBJECTIVES

The goal of this work was to reduce the scan time of contrast-enhanced whole-heart coronary magnetic resonance angiography (MRA) by using a gradient echo interleaved echo planar imaging (GRE-EPI) sequence at 3 T field strength.

MATERIALS AND METHODS

A GRE-EPI sequence was optimized to acquire contrast-enhanced whole-heart coronary MRA at 3 T. First-order phase correction was used for alignment of the odd and even echoes in the GRE-EPI echo train. Single and dual reference scan techniques for estimation of the linear phase correction parameters were evaluated using both phantom and volunteer studies. The GRE-EPI readout was combined with parallel imaging for a further reduction in scan time. To avoid image distortions, calibration signals for coil sensitivity estimation were acquired in a separate low resolution GRE scan before the whole-heart GRE-EPI scan. Eight healthy volunteers were scanned with the optimized contrast-enhanced GRE-EPI sequence. GRE-EPI images were acquired during slow infusion (0.3 mL/s) of 0.1 mmol/kg body weight of Gd-BOPTA. For comparison purposes, the same 8 volunteers were scanned again in a separate scan session using a traditional GRE sequence with double the dose (0.2 mmol/kg body weight) of the same contrast agent with the same injection rate. The contrast-enhanced GRE-EPI and contrast-enhanced GRE techniques were compared in terms of relative signal-to-noise ratio (rSNR), relative contrast-to-noise ratio (rCNR), image quality scores, and visualized vessel lengths.

RESULTS

Both, phantom and volunteer studies demonstrated that the dual reference scan phase correction technique was a key step for obtaining satisfactory image quality using GRE-EPI at 3 T. Whole-heart coronary MRA with a spatial resolution of 1.0 x 1.0 x 2.0 mm3 was acquired with the GRE-EPI sequence in an average scan time of 2.5 +/- 0.6 minutes, compared with 8.6 +/- 2.7 minutes for the GRE technique. The GRE-EPI technique had lower rCNR compared with the GRE sequence. The image quality and coronary artery visualization with the GRE-EPI technique were adequate, and there was no statistically significant difference in the image quality scores, rSNR, and visualized coronary artery lengths between the GRE-EPI and GRE techniques.

CONCLUSIONS

Contrast-enhanced whole-heart coronary MRA using the GRE-EPI technique resulted in excellent delineation of all the major coronary arteries and compared with current GRE techniques demonstrated a factor of 2 reduction in contrast agent dose and a factor of 3 reduction in scan time.

Contrast-enhanced whole-heart coronary magnetic resonance angiography at 3 T with radial EPI

Whole-heart coronary magnetic resonance angiography is a promising method for detecting coronary artery disease. However, the imaging time is relatively long (typically 10-15 min). The goal of this study was to implement a radial echo planar imaging sequence for contrast-enhanced whole-heart coronary magnetic resonance angiography, with the aim of combining the scan efficiency of echo planar imaging with the motion insensitivity of radial k-space sampling. A self-calibrating phase correction technique was used to correct for off-resonance effects, trajectory measurement was used to correct for k-space trajectory errors, and variable density sampling was used in the partition direction to reduce streaking artifacts. Seven healthy volunteers and two patients were scanned with the proposed radial echo planar imaging sequence, and the images were compared with a traditional gradient echo and X-ray angiography techniques, respectively. Whole-heart images with the radial EPI technique were acquired with a resolution of 1.0 × 1.0 × 2.0 mm(3) in a scan time of 5 min. In healthy volunteers, the average image quality scores and visualized vessel lengths of the RCA and LAD were similar for the radial EPI and gradient echo techniques (P value > 0.05 for all). Anecdotal patient studies showed excellent agreement of the radial EPI technique with X-ray angiography.

Detection of coronary artery anomalies by dual-source CT coronary angiography

AIM

To retrospectively evaluate the clinical value of dual-source computed tomography (DSCT) coronary angiography in the diagnosis of coronary artery anomalies.

MATERIALS AND METHODS

A large cohort of 3625 consecutive patients, who underwent DSCT coronary angiography in our institute, was reviewed for coronary artery anomalies. All images were evaluated by two experienced readers using axial source images, multi-planar reformations (MPR), maximum intensity projections (MIP) and volume rendering (VR). Coronary artery anomalies were found in 36 patients (male 20, female 16, mean age 48 years, range 15-76 years). Of the 36 patients, 19 patients also underwent conventional coronary angiography (CCA).

RESULTS

The incidence of coronary artery anomalies was 0.99% (36/3625). Six different types of coronary artery anomalies were diagnosed by DSCT coronary angiography: (1) 11 anomalies of the right coronary artery; (2) five anomalies of the left coronary artery; (3) 10 anomalies of the left circumflex artery; (4) two single coronary artery; (5) one anomalous pulmonary origin of the coronary artery; (6) seven coronary artery fistula. Evaluation of the CCA resulted in a precise diagnosis in 53% (10/19) patients.

CONCLUSION

DSCT coronary angiography is a good diagnostic tool to examine coronary artery anomalies.

Self-gating MR imaging of the fetal heart: comparison with real cardiac triggering

PURPOSE

To investigate the self-gating technique for MR imaging of the fetal heart in a sheep model.

MATERIAL AND METHODS

MR images of 6 fetal sheep heart were obtained at 1.5 T. For self-gating MRI of the fetal heart a cine SSFP in short axis, two and four chamber view was used. Self-gated images were compared with real cardiac triggered MR images (pulse-wave triggering). MRI of the fetal heart was performed using both techniques simultaneously. Image quality was assessed and the left ventricular volume and function were measured and compared.

RESULTS

Compared with pulse-wave triggering, the self-gating technique produced slightly inferior images with artifacts. Especially the atrial septum could not be so clearly depicted. The contraction of the fetal heart was shown in cine sequences in both techniques. The average blood volumes could be measured with both techniques with no significant difference: at end-systole 3.1 ml (SD±0.2), at end-diastole 4.9 ml (±0.2), with ejection fractions at 38.6%, respectively 39%.

CONCLUSION

Both self-gating and pulse-wave triggered cardiac MRI of the fetal heart allowed the evaluation of anatomical structures and functional information. Images obtained by self-gating technique were slightly inferior than the pulse-wave triggered MRI.

Influence of applying nitroglycerin in whole-heart free-breathing 3D coronary MR angiography

OBJECTIVE

The purpose of our study was to assess the impact of sublingual nitroglycerin (NTG) spray on free-breathing 3D whole-heart coronary MR angiography (MRA).

SUBJECTS AND METHODS

We compared the timing parameters; measured the lumen diameter of the major coronary arteries; calculated coronary vasodilation, apparent signal-to-noise ratio (SNR), and apparent contrast-to-noise ratio (CNR); and evaluated the image quality on pre- and post-NTG coronary MRA in 15 volunteers. Statistical analysis was performed with p value less than 0.05 considered significant.

RESULTS

The mean trigger delay and optimal acquisition window were shortened significantly and the mean scanning time was prolonged statistically after NTG administration. There was no significant alteration in terms of apparent SNR and apparent CNR. The lumen diameters were significantly larger in coronary MRA post-NTG than in that of pre-NTG, with an average 25.35% +/- 6.51% (SD) increase, and the left circumflex coronary artery (LCX) had slightly lower vasodilation in comparison with the right coronary artery. Image quality scores of 53 (39.3%, 53/135) segments were increased and 15 segments (11.1%, 15/135) decreased after NTG administration, and the remaining 67 segments (49.6%, 67/135) were unchanged.

CONCLUSION

In general, sublingual NTG is useful for improving visualization of the coronary artery lumen and alleviating the impact of artifact. However, several alterations and disadvantages should be taken into consideration in view of the disturbed assessment of vasodilatory response in the LCX and the impaired quality in a minority of segments after NTG administration. Further studies are needed to evaluate the effect of beta-blockade on eliminating the disadvantages of sublingual NTG.

Whole-heart contrast-enhanced coronary magnetic resonance angiography using gradient echo interleaved EPI

Whole-heart coronary MR angiography (MRA) is a promising method for detecting coronary artery disease. However, the imaging time is relatively long (on the order of 10-15 min). Such a long imaging time may result in patient discomfort and compromise the robustness of whole-heart coronary MRA due to increased respiratory and cardiac motion artifacts. The goal of this study was to optimize a gradient echo interleaved echo planar imaging (GRE-EPI) acquisition scheme for reducing the imaging time of contrast-enhanced whole-heart coronary MRA. Numerical simulations and phantom studies were used to optimize the GRE-EPI sequence parameters. Healthy volunteers were scanned with both the proposed GRE-EPI sequence and a 3D TrueFISP sequence for comparison purposes. Slow infusion (0.5 cc/sec) of Gd-DTPA was used to enhance the signal-to-noise ratio (SNR) of the GRE-EPI acquisition. Whole-heart images with the GRE-EPI technique were acquired with a true resolution of 1.0 x 1.1 x 2.0 mm(3) in an average scan time of 4.7 +/- 0.7 min with an average navigator efficiency of 44 +/- 6%. The GRE-EPI acquisition showed excellent delineation of all the major coronary arteries with scan time reduced by a factor of 2 compared with the TrueFISP acquisition.

Coronary MR imaging: lumen and wall

Coronary MR imaging is a promising noninvasive technique for the combined assessment of coronary artery anatomy and function. Anomalous coronary arteries and aneurysms can reliably be assessed in clinical practice using coronary MR imaging and the presence of significant left main or proximal multivessel coronary artery disease detected. Technical challenges that need to be addressed are further improvements in motion suppression and abbreviated scanning times aimed at improving spatial resolution and patient comfort. The development of new and specific contrast agents, high-field MR imaging with improved spatial resolution, and continued progress in MR imaging methods development will undoubtedly lead to further progress toward the noninvasive and comprehensive assessment of coronary atherosclerotic disease.

Noninvasive assessment of coronary anatomy and myocardial perfusion: going toward an integrated imaging approach

Many noninvasive imaging techniques are available for the evaluation of patients with known or suspected chronic coronary artery disease. Among these, computed tomography-based techniques allow the quantification of coronary atherosclerotic calcium and noninvasive imaging of coronary arteries, whereas nuclear cardiology is the most widely used noninvasive approach for the assessment of myocardial perfusion. The available single-photon emission computed tomography flow agents are characterized by a cardiac uptake proportional to myocardial blood flow. In addition, different positron emission tomography tracers may be used for the quantitative measurement of myocardial blood flow and coronary flow reserve. Extensive research is currently being performed in the development of noninvasive coronary angiography and myocardial perfusion imaging using cardiac magnetic resonance. Finally, new multimodality imaging systems have been recently developed, bringing together anatomical and functional information. This review sought to provide a description of the relative merits of noninvasive imaging techniques in the assessment of coronary anatomy and myocardial perfusion in patients with known or suspected coronary artery disease.

Cardiac magnetic resonance at high field: promises and problems

Cardiac magnetic resonance imaging (CMRI) at high magnetic field (3 Tesla) is rapidly evolving with many promising results. However, the challenges of field inhomogeneities and specific absorption rate limitations need to be addressed before reaping the benefits of high magnetic field for CMRI. This review focuses on the methods to overcome some of these challenges and the current and potential applications of this technology.

Diagnosis of variants of single right coronary trunk using 64 multidetector computed tomography

Single coronary anomalies are one of the rarest variants of coronary anatomy. Widespread use of coronary CT angiography has made it possible to diagnose these variants with increasing incidence. We report two cases of single right coronary trunk with different anatomic course of the left coronary artery; one anterior to the main pulmonary artery and the second between the main pulmonary artery and ascending aorta and then coursing within the interventricular septum.