Coronary Magnetic Resonance Angiography Research Articles

Fat signal suppression for coronary MRA at 3T using a water‐selective adiabatic T2‐preparation technique

PurposeTo improve fat saturation in coronary MRA at 3T by using a spectrally selective adiabatic T2‐Prep (WSA‐T2‐Prep).MethodsA conventional adiabatic T2‐Prep (CA‐T2‐Prep) was modified, such that the excitation and restoration pulses were of differing bandwidths. On‐resonance spins are T2‐Prepared, whereas off‐resonance spins, such as fat, are spoiled. This approach was combined with a CHEmically Selective Saturation (CHESS) pulse to achieve even greater fat suppression. Numerical simulations were followed by phantom validation and in vivo coronary MRA.ResultsNumerical simulations demonstrated that augmenting a CHESS pulse with a WSA‐T2‐Prep improved robustness to B1 inhomogeneities and that this combined fat suppression was effective over a broader spectral range than that of a CHESS pulse in a conventional T2‐Prepared sequence. Phantom studies also demonstrated that the WSA‐T2‐Prep+CHESS combination produced greater fat suppression across a range of B1 values than did a CA‐T2‐Prep+CHESS combination. Lastly, in vivo measurements demonstrated that the contrast‐to‐noise ratio between blood and myocardium was not adversely affected by using a WSA‐T2‐Prep, despite the improved abdominal and epicardial fat suppression. Additionally, vessel sharpness improved.ConclusionThe proposed WSA‐T2‐Prep method was shown to improve fat suppression and vessel sharpness as compared to a CA‐T2‐Prep technique, and to also increase fat suppression when combined with a CHESS pulse. Magn Reson Med 72:763–769, 2014. © 2013 Wiley Periodicals, Inc.

Postmortem magnetic resonance imaging of the heart ex situ: development of technical protocols.

Postmortem MRI (PMMR) examinations are seldom performed in legal medicine due to long examination times, unfamiliarity with the technique, and high costs. Furthermore, it is difficult to obtain access to an MRI device used for patients in clinical settings to image an entire human body. An alternative is available: ex situ organ examination. To our knowledge, there is no standardized protocol that includes ex situ organ preparation and scanning parameters for postmortem MRI. Thus, our objective was to develop a standard procedure for ex situ heart PMMR examinations. We also tested the oily contrast agent Angiofil® commonly used for PMCT angiography, for its applicability in MRI. We worked with a 3 Tesla MRI device and 32-channel head coils. Twelve porcine hearts were used to test different materials to find the best way to prepare and place organs in the device and to test scanning parameters. For coronary MR angiography, we tested different mixtures of Angiofil® and different injection materials. In a second step, 17 human hearts were examined to test the procedure and its applicability to human organs. We established two standardized protocols: one for preparation of the heart and another for scanning parameters based on experience in clinical practice. The established protocols enabled a standardized technical procedure with comparable radiological images, allowing for easy radiological reading. The performance of coronary MR angiography enabled detailed coronary assessment and revealed the utility of Angiofil® as a contrast agent for PMMR. Our simple, reproducible method for performing heart examinations ex situ yields high quality images and visualization of the coronary arteries.

Repositioning precision of coronary arteries measured on X-ray angiography and its implications for coronary MR angiography.

To test the hypothesis that intervals with superior beat-to-beat coronary artery repositioning precision exist in the cardiac cycle, to design a coronary MR angiography (MRA) methodology in response, and to ascertain its performance. Coronary repositioning precision in consecutive heartbeats was measured on x-ray coronary angiograms of 17 patients and periods with the highest repositioning precision were identified. In response, the temporal order of coronary MRA pulse sequence elements required modification and the T2 -prep now follows (T2 -post) rather than precedes the imaging part of the sequence. The performance of T2 -post was quantitatively compared (signal-to-noise [SNR], contrast-to-noise [CNR], vessel sharpness) to that of T2 -prep in vivo. Coronary repositioning precision is <1 mm at peak systole and in mid diastole. When comparing systolic T2 -post to diastolic T2 -prep, CNR and vessel sharpness remained unchanged (both P = NS) but SNR for muscle and blood increased by 104% and 36% (both P < 0.05), respectively. Windows with improved coronary repositioning precision exist in the cardiac cycle: one in peak systole and one in mid diastole. Peak-systolic imaging necessitates a re-design of conventional coronary MRA pulse sequences and leads to image quality very similar to that of conventional mid-diastolic data acquisition but improved SNR.

Reduction of respiratory motion artifacts for free-breathing whole-heart coronary MRA by weighted iterative reconstruction.

To combine weighted iterative reconstruction with self-navigated free-breathing coronary magnetic resonance angiography for retrospective reduction of respiratory motion artifacts. One-dimensional self-navigation was improved for robust respiratory motion detection and the consistency of the acquired data was estimated on the detected motion. Based on the data consistency, the data fidelity term of iterative reconstruction was weighted to reduce the effects of respiratory motion. In vivo experiments were performed in 14 healthy volunteers and the resulting image quality of the proposed method was compared to a navigator-gated reference in terms of acquisition time, vessel length, and sharpness. Although the sampling pattern of the proposed method contained 60% more samples with respect to the reference, the scan efficiency was improved from 39.5 ± 10.1% to 55.1 ± 9.1%. The improved self-navigation showed a high correlation to the standard navigator signal and the described weighting efficiently reduced respiratory motion artifacts. Overall, the average image quality of the proposed method was comparable to the navigator-gated reference. Self-navigated coronary magnetic resonance angiography was successfully combined with weighted iterative reconstruction to reduce the total acquisition time and efficiently suppress respiratory motion artifacts. The simplicity of the experimental setup and the promising image quality are encouraging toward future clinical evaluation.

Magnetic Resonance of Coronary Arteries

The assessment of luminal narrowing and altered blood flow in the coronary artery is challenging because of the small size of the vessel and the complex motion caused by cardiac contraction and respiration. Free-breathing, whole-heart coronary magnetic resonance angiography (MRA) has been introduced as a method that can provide visualization of all 3 major coronary arteries within a single 3-dimensional acquisition, either by using 1.5 T steady-state free precession or 3 T gradient-echo sequences. Recent studies have indicated that coronary MRA has sufficient diagnostic accuracy for excluding coronary artery disease (CAD) in patients with suspected CAD. Furthermore, coronary MRA can provide risk stratification for future cardiac events. In addition to the morphologic assessment of the coronary artery, phase-contrast cine MR imaging has unique advantages because it allows for measurement of blood flow and flow reserve in the coronary arteries. Comprehensive assessment of the morphology and blood flow in the coronary artery has a great potential in noninvasive detection of physiologically significant CAD that requires revascularization. The aim of this review is to provide an update on current technical improvements in coronary MRA and MR flow measurement of coronary arteries.

High Spatial Resolution Coronary Magnetic Resonance Angiography at 7 T

The aim of this study was to compare bright blood high spatial resolution (HR) coronary magnetic resonance angiography (MRA) with low spatial resolution (LR) bright blood coronary MRA at 7 T. Twenty-four healthy volunteers underwent navigator-gated 3-dimensional imaging of the right coronary artery at 7 T using 2 sequences: HR bright blood and LR bright blood. Image postprocessing involved newly developed multiplanar reformatting to straighten the right coronary artery. Image quality was determined by vessel edge sharpness, signal-to-noise ratio, contrast-to-noise ratio, visible vessel length, and vessel diameter. Vessel edge sharpness was statistically significantly higher in HR as compared with LR (0.57 ± 0.1 vs 0.46 ± 0.06; P < 0.001), at the cost of lower signal-to-noise ratio (HR, 32.9 ± 11.0 vs LR, 112.5 ± 48.9; P < 0.001) and contrast-to-noise ratio (HR, 17.9 ± 7.4 vs LR, 50.5 ± 26.1; P < 0.001). Visible vessel length and vessel diameter were similar for both sequences (P > 0.05). High spatial resolution bright blood coronary MRA at 7 T is feasible and improves vessel edge sharpness as compared with LR bright blood imaging.

Robust volume-targeted balanced steady-state free-precession coronary magnetic resonance angiography in a breathhold at 3.0 Tesla: a reproducibility study.

BackgroundTransient balanced steady-state free-precession (bSSFP) has shown substantial promise for noninvasive assessment of coronary arteries but its utilization at 3.0 T and above has been hampered by susceptibility to field inhomogeneities that degrade image quality. The purpose of this work was to refine, implement, and test a robust, practical single-breathhold bSSFP coronary MRA sequence at 3.0 T and to test the reproducibility of the technique.MethodsA 3D, volume-targeted, high-resolution bSSFP sequence was implemented. Localized image-based shimming was performed to minimize inhomogeneities of both the static magnetic field and the radio frequency excitation field. Fifteen healthy volunteers and three patients with coronary artery disease underwent examination with the bSSFP sequence (scan time = 20.5 ± 2.0 seconds), and acquisitions were repeated in nine subjects. The images were quantitatively analyzed using a semi-automated software tool, and the repeatability and reproducibility of measurements were determined using regression analysis and intra-class correlation coefficient (ICC), in a blinded manner.ResultsThe 3D bSSFP sequence provided uniform, high-quality depiction of coronary arteries (n = 20). The average visible vessel length of 100.5 ± 6.3 mm and sharpness of 55 ± 2% compared favorably with earlier reported navigator-gated bSSFP and gradient echo sequences at 3.0 T. Length measurements demonstrated a highly statistically significant degree of inter-observer (r = 0.994, ICC = 0.993), intra-observer (r = 0.894, ICC = 0.896), and inter-scan concordance (r = 0.980, ICC = 0.974). Furthermore, ICC values demonstrated excellent intra-observer, inter-observer, and inter-scan agreement for vessel diameter measurements (ICC = 0.987, 0.976, and 0.961, respectively), and vessel sharpness values (ICC = 0.989, 0.938, and 0.904, respectively).ConclusionsThe 3D bSSFP acquisition, using a state-of-the-art MR scanner equipped with recently available technologies such as multi-transmit, 32-channel cardiac coil, and localized B0 and B1+ shimming, allows accelerated and reproducible multi-segment assessment of the major coronary arteries at 3.0 T in a single breathhold. This rapid sequence may be especially useful for functional imaging of the coronaries where the acquisition time is limited by the stress duration and in cases where low navigator-gating efficiency prohibits acquisition of a free breathing scan in a reasonable time period.

Coronary Magnetic Resonance Angiography in Heterotopic Heart Transplant Recipient

Coronary allograft vasculopathy remains the main limiting survival factor after heart transplantation and the major cause of mortality after the first year post-transplant, ultimately leading to graft loss.1 Coronary x-ray angiography is the clinical gold standard and the most widely used diagnostic technique for coronary allograft vasculopathy in the majority of transplant centers. However, repeated x-ray procedures have inherent risks related to the cumulative radiation dose. Coronary magnetic resonance angiography2 (CMRA) has emerged as a useful imaging modality in pediatric patients as a noninvasive and radiation-free approach and appears very promising for imaging the coronary arteries in heart transplant recipients, although it has yet to be clinically established. A 16-year-old girl who had received a heterotopic heart transplant (HHT) at 5 months of age because of an undersized graft attended our follow-up clinic. She had been diagnosed with dilated cardiomyopathy at 3.5 months of age. Heterotopic heart transplant can be used in rare cases in which orthotopic heart transplantation is contraindicated, such as for elevated pulmonary …

A new framework for interleaved scanning in cardiovascular MR: Application to image‐based respiratory motion correction in coronary MR angiography

To describe a new framework for interleaving scans and demonstrate its usefulness for image-based respiratory motion correction in whole heart coronary MR angiography (CMRA). Scan interleaving using the proposed approach was achieved by switching between separately defined, independent scans at arbitrary time points during their execution, using a generic function call. The scan interleaving framework was used to perform scan interleaving for image-based respiratory navigation of CMRA with spiral, radial, and Cartesian echo-planar imaging (EPI) navigator k-space trajectories. Eight healthy volunteers were scanned. Improved coronary vessel sharpness and visual scores were obtained using spiral and Cartesian EPI navigators compared with radial navigators. The usefulness of the proposed scan interleaving framework was demonstrated for image-based respiratory motion correction. It facilitated more direct comparisons of image navigator acquisitions with different k-space trajectories. Furthermore, we could demonstrate that spiral and Cartesian EPI navigators may be particularly suitable for image-based motion correction, as they provide improved motion correction and high navigator apparent signal-to-noise ratio while spending very little magnetization, thereby minimizing saturation effects.

Highly efficient respiratory motion compensated free‐breathing coronary mra using golden‐step Cartesian acquisition

To develop an efficient 3D affine respiratory motion compensation framework for Cartesian whole-heart coronary magnetic resonance angiography (MRA). The proposed method achieves 100% scan efficiency by estimating the affine respiratory motion from the data itself and correcting the acquired data in the reconstruction process. For this, a golden-step Cartesian sampling with spiral profile ordering was performed to enable reconstruction of respiratory resolved images at any breathing position and with different respiratory window size. Affine motion parameters were estimated from image-based registration of 3D undersampled respiratory resolved images reconstructed with iterative SENSE and motion correction was performed directly in the reconstruction using a multiple-coils generalized matrix formulation method. This approach was tested on healthy volunteers and compared against a conventional diaphragmatic navigator-gated acquisition using quantitative and qualitative image quality assessment. The proposed approach achieved 47 ± 12% and 59 ± 6% vessel sharpness for the right (RCA) and left (LAD) coronary arteries, respectively. Also, good quality visual scores of 2.4 ± 0.74 and 2.44 ± 0.86 were observed for the RCA and LAD (scores from 0, no to 4, excellent coronary vessel delineation). A not statically significant difference (P = 0.05) was found between the proposed method and an 8-mm navigator-gated and tracked scan, although scan efficiency increased from 61 ± 10% to 100%. We demonstrate the feasibility of a new 3D affine respiratory motion correction technique for Cartesian whole-heart CMRA that achieves 100% scan efficiency and therefore a predictable acquisition time. This approach yields image quality comparable to that of an 8-mm navigator-gated acquisition with lower scan efficiency. Further evaluation of this technique in patients is now warranted to determine its clinical use.

Accelerated whole‐heart coronary MRA using motion‐corrected sensitivity encoding with three‐dimensional projection reconstruction

To achieve whole-heart coronary magnetic resonance angiography (MRA) with (1.0 mm)(3) spatial resolution and 5 min of free-breathing scan time. We used an electrocardiograph-gated, T2-prepared and fat-saturated balanced steady state free precession sequence with 3DPR trajectory for free-breathing data acquisition with 100% gating efficiency. For image reconstruction, we used a self-calibrating iterative SENSE scheme with integrated retrospective motion correction. We performed healthy volunteer study to compare the proposed method with motion-corrected gridding at different retrospective undersampling levels on apparent signal-to-noise ratio (aSNR) and subjective coronary artery (CA) visualization scores. Compared with gridding, the proposed method significantly improved both image quality metrics for undersampled datasets with 6000, 8000, and 10,000 projections. With as few as 10,000 projections, the proposed method yielded good CA visualization scores (3.02 of 4) and aSNR values comparable to those with 20,000 projections. Using the proposed method, good image quality was observed for free breathing whole-heart coronary MRA at (1.0 mm)(3) resolution with an achievable scan time of 5 min.

High-resolution 3D whole-heart coronary MRA: a study on the combination of data acquisition in multiple breath-holds and 1D residual respiratory motion compensation

To study a scan protocol for coronary magnetic resonance angiography based on multiple breath-holds featuring 1D motion compensation and to compare the resulting image quality to a navigator-gated free-breathing acquisition. Image reconstruction was performed using L1 regularized iterative SENSE. The effects of respiratory motion on the Cartesian sampling scheme were minimized by performing data acquisition in multiple breath-holds. During the scan, repetitive readouts through a k-space center were used to detect and correct the respiratory displacement of the heart by exploiting the self-navigation principle in image reconstruction. In vivo experiments were performed in nine healthy volunteers and the resulting image quality was compared to a navigator-gated reference in terms of vessel length and sharpness. Acquisition in breath-hold is an effective method to reduce the scan time by more than 30% compared to the navigator-gated reference. Although an equivalent mean image quality with respect to the reference was achieved with the proposed method, the 1D motion compensation did not work equally well in all cases. In general, the image quality scaled with the robustness of the motion compensation. Nevertheless, the featured setup provides a positive basis for future extension with more advanced motion compensation methods.

Coronary magnetic resonance angiography of coronary artery total occlusion: imaging findings and success rates of percutaneous coronary intervention according to intraluminal signal intensity patterns

Background We hypothesized that intraluminal signal intensity (SI) of coronary total occlusion (CTO) lesions at coronary MR angiography (CMRA) may reflect the degree of the softness of the lesion with or without the presence of microvessels. The purposes of our study were to report the CMRA findings of CTO lesions and to compare success rates of percutaneous coronary intervention (PCI) for CTO lesions according to different SI patterns at CMRA. Methods Ninety-one consecutive CTO patients who underwent steady-state free precession CMRA (free-breathing whole-heart and breath-hold volume-targeted) and late gadolinium enhancement imaging using a 1.5-T scanner before PCI were included. We analyzed the images of CMRA and PCI results of the patients. Ninety-three CTO lesions were analyzed for this study. Lesions were graded according to CMRA findings of CTO segment: (Gr. 1) tubular appearance with homogeneously high SI (HSI), (Gr. 2) continuous HSI areas with moderate irregularity in contour, (Gr. 3) heterogeneous SI lesion with interrupted HSI areas, (Gr. 4) intermediate or low SI lesion. Lesions were classified into two groups with regard to the presence of the continuity of HSI areas. Angiographic findings including lesion length, collateral grades, and thrombolysis in myocardial infarction (TIMI) grades were recorded at invasive coronary angiography. Multivariable statistical test was performed to identify variables associated with successful PCI. Results Seventy-three lesions (78%) of 93 CTO lesions were successfully treated with PCI. On CMRA images, the presence of continuity of HSI areas was found in 60 lesions (64.5%) including lesions of Gr. 2 (n = 13). Fifty-four lesions (90%) of the 60 lesions were successfully treated with PCI. The others (Gr. 3 or 4) were 33 lesions (Gr. 3, 14; Gr. 4, 19). Nineteen lesions (58%) of the 33 lesions were successfully treated with PCI. At multivariable analysis, the presence of continuity of HSI areas in CTO segments proved to be the only independent predictor of PCI success (odds ratio, 6.65: 95% confidence interval, [2.09, 21.11]; P = 0.001), while angiographic findings did not significantly correlate with PCI outcomes. Conclusions

CMRA with 100% navigator efficiency with 3D self navigation and interleaved scanning

Background In recent years many novel self navigation techniques have been proposed to solve the problems associated with cardiac motion in coronary MR angiography (CMRA). A new method of interleaved scanning (iScan) allows more flexibility in designing and testing novel imaging sequences as independent scans, with different imaging parameters including k-space trajectories, can be interleaved. We compared the performance of a 3D self navigator (3DSN) with 100% scan efficiency to traditional 1D navigators, whereby the 3DSN scan was setup as a single shot scan and was called by the high resolution segmented multishot CMRA scan each cardiac cycle. We have shown in previous work that correcting all acquired data in foot-head (FH) and left-right direction (LR) can provide equivalent image quality to traditional gated scans (J Powell et al. 2013 Proc. ISMRM). Here we sought to investigate and compare the effect of correcting data in 3 dimensions (FH, LR and AP).

Long-term follow-up of coronary MR and CT angiography for prediction of cardiac events

Background Although some studies have shown the potential utility of coronary magnetic resonance angiography (CMRA) for the detection of coronary artery disease (CAD), almost no information exists regarding its prognostic value. Aim of our study was to compare the predictive value of CMRA and coronary multislice computed tomography angiography (CCTA) for prediction of cardiovascular events at long-term follow-up, with invasive coronary angiography (ICA) as the reference method.

High-resolution whole-heart contrast-enhanced coronary MRA in 5 minutes with self-navigation and 100% gating efficiency

Background Contrast-enhanced (CE) whole-heart coronary MRA is a promising technique for CAD detection [1]. However, the current imaging time is relatively long and variable, and the spatial resolution is limited. The aim of this work is to develop and evaluate a 3D projection reconstruction (3DPR) based CE coronary MRA technique that achieves (1.0 mm) spatial resolution and 5-minute scan time, which has been previously validated on non-contrast coronary MRA [2]. Similar to the previous work, we compare the apparent SNR of two undersampling levels with 10,000 and 20,000 radial projections to explore the impact of undersampling on image quality in the context of CE imaging.

Dynamic self-navigated 3D whole-heart radial coronary MRA with retrospective acquisition window selection

Background Navigator gated coronary MRA is highly time inefficient as the data collection duty cycle (DC) is only 2% [1]. Here, we report a new, dynamic self-navigated coronary MRA technique with isotropic spatial resolution that a) further improves DC by continuously acquiring image data without ECG triggering and that b) enables retrospective, flexible, and individual selection of the acquisition window in the cardiac cycle.

Contribution of cardiovascular magnetic resonance in the evaluation of coronary arteries.

Cardiovascular magnetic resonance (CMR) allows the nonradiating assessment of coronary arteries; to achieve better image quality cardiorespiratory artefacts should be corrected. Coronary MRA (CMRA) at the moment is indicated only for the detection of abnormal coronary origin, coronary artery ectasia and/or aneurysms (class I indication) and coronary bypass grafts (class II indication). CMRA utilisation for coronary artery disease is not yet part of clinical routine. However, the lack of radiation is of special value for the coronary artery evaluation in children and women. CMRA can assess the proximal part of coronary arteries in almost all cases. The best results have been observed in the evaluation of the left anterior descending and the right coronary artery, while the left circumflex, which is located far away from the coil elements, is frequently imaged with reduced quality, compared to the other two. Different studies detected an increase in wall thickness of the coronaries in patients with type I diabetes and abnormal renal function. Additionally, the non-contrast enhanced T1-weighed images detected the presence of thrombus in acute myocardial infarction. New techniques using delayed gadolinium enhanced imaging promise the direct visualization of inflamed plaques in the coronary arteries. The major advantage of CMR is the potential of an integrated protocol offering assessment of coronary artery anatomy, cardiac function, inflammation and stress perfusion-fibrosis in the same study, providing an individualized clinical profile of patients with heart disease.

心臓MRI：負荷パーフュージョンMRI と冠動脈MRA

心臓MRI：負荷パーフュージョンMRI と冠動脈MRA

Gadofosveset trisodium in coronary magnetic resonance angiography at 3 Tesla

Background Coronary magnetic resonance angiography (MRA) at 3T suffers from imaging inconsistencies compared to 1.5T despite the use of gadolinium-based contrast agents (GBCAs). Gadofosveset Trisodium (Ablavar ® ,L antheus Medical Imaging), with its high relaxivity and long intravascular residence time, offers greater potential over standard GBCAs to improve evaluation of the coronary arteries. Compared to its validation in larger arteries, the optimum dosage for coronary MRA has yet to be assessed. The purpose of the study was to evaluate the diagnostic potential of a 0.06 mmol/kg dose of Gadofosveset compared to a standard clinical dose of 0.03 mmol/kg, using a free-breathing whole-heart coronary MRA protocol with 1.0 mm3 spatial resolution and 100% navigator efficiency. The injection protocol was optimized for the prolonged pharmacokinetics of Gadofosveset. Methods Twenty two contrast enhanced CMR scans were performed in 11 subjects [2 (18.2%) male; 27.3 ± 6 years; BMI = 23.1 ± 3 kg/m2] on a 3.0T Verio Siemens scanner, using