Functional cardiac MR imaging with steady-state free precession (SSFP) significantly improves endocardial border delineation without contrast agents

Phenotyping heart failure by cardiac magnetic resonance imaging of cardiac macro- and microscopic structure: state of the art review

Heart failure demographics have evolved in past decades with the development of improved diagnostics, therapies, and prevention. Cardiac magnetic resonance (CMR) has developed in a similar timeframe to become the gold-standard non-invasive imaging modality for characterizing diseases causing heart failure. CMR techniques to assess cardiac morphology and function have progressed since their first use in the 1980s. Increasingly efficient acquisition protocols generate high spatial and temporal resolution images in less time. This has enabled new methods of characterizing cardiac systolic and diastolic function such as strain analysis, exercise real-time cine imaging and four-dimensional flow. A key strength of CMR is its ability to non-invasively interrogate the myocardial tissue composition. Gadolinium contrast agents revolutionized non-invasive cardiac imaging with the late gadolinium enhancement technique. Further advances enabled quantitative parametric mapping to increase sensitivity at detecting diffuse pathology. Novel methods such as diffusion tensor imaging and artificial intelligence-enhanced image generation are on the horizon. Magnetic resonance spectroscopy (MRS) provides a window into the molecular environment of the myocardium. Phosphorus (31P) spectroscopy can inform the status of cardiac energetics in health and disease. Proton (1H) spectroscopy complements this by measuring creatine and intramyocardial lipids. Hyperpolarized carbon (13C) spectroscopy is a novel method that could further our understanding of dynamic cardiac metabolism. CMR of other organs such as the lungs may add further depth into phenotypes of heart failure. The vast capabilities of CMR should be deployed and interpreted in context of current heart failure challenges.

Cardiac MRI: An Alternative Method to Determine the Left Ventricular Function

(1) Background: With the conventional contour surface method (KfM) for the evaluation of cardiac function parameters, the papillary muscle is considered to be part of the left ventricular volume. This systematic error can be avoided with a relatively easy-to-implement pixel-based evaluation method (PbM). The objective of this thesis is to compare the KfM and the PbM with regard to their difference due to papillary muscle volume exclusion. (2) Material and Methods: In the retrospective study, 191 cardiac-MR image data sets (126 male, 65 female; median age 51 years; age distribution 20-75 years) were analysed. The left ventricular function parameters: end-systolic volume (ESV), end-diastolic volume (EDV), ejection fraction (EF) and stroke volume (SV) were determined using classical KfW (syngo.via and cvi42 = gold standard) and PbM. Papillary muscle volume was calculated and segmented automatically via cvi42. The time required for evaluation with the PbM was collected. (3) Results: The size of EDV was 177 mL (69-444.5 mL) [average, [minimum-maximum]], ESV was 87 mL (20-361.4 mL), SV was 88 mL and EF was 50% (13-80%) in the pixel-based evaluation. The corresponding values with cvi42 were EDV 193 mL (89-476 mL), ESV 101 mL (34-411 mL), SV 90 mL and EF 45% (12-73%) and syngo.via: EDV 188 mL (74-447 mL), ESV 99 mL (29-358 mL), SV 89 mL (27-176 mL) and EF 47% (13-84%). The comparison between the PbM and KfM showed a negative difference for end-diastolic volume, a negative difference for end-systolic volume and a positive difference for ejection fraction. No difference was seen in stroke volume. The mean papillary muscle volume was calculated to be 14.2 mL. The evaluation with PbM took an average of 2:02 min. (4) Conclusion: PbM is easy and fast to perform for the determination of left ventricular cardiac function. It provides comparable results to the established disc/contour area method in terms of stroke volume and measures "true" left ventricular cardiac function while omitting the papillary muscles. This results in an average 6% higher ejection fraction, which can have a significant influence on therapy decisions.

Contrast-enhanced cine MR sequences in the assessment of myocardial hyperemia in acute myocarditis: can they help? A feasibility study

The study was designed to assess the accuracy of contrast-enhanced balanced steady-state free precession (cine-SSFP) CMR imaging sequences to exhibit myocardial hyperemia in acute myocarditis, which has for a long time been investigated in some centers using early gadolinium enhancement (EGE) sequence. Contrast-enhanced cine-SSFP (CESSFP) sequences were compared to precontrast cine-SSFP sequences to calculate the early cine-contrast enhancement in 36 consecutive patients with acute myocarditis and 36 controls matched for age and gender. Four-chamber views images were obtained in each subject before and after gadolinium injection. Absolute and relative left ventricular myocardial enhancement of the overall myocardium, then separately of the lateral wall and interventricular septum was analyzed in telediastole. Myocarditis patients displayed higher cine-SSFP absolute enhancement than controls (overall left ventricular myocardium 2.38 ± 0.33 vs 1.84 ± 0.31; lateral wall 2.45 ± 0.35 vs 1.83 ± 0.32; and septum 2.26 ± 0.29 vs 1.82 ± 0.29, p < 0.0001 for all). Less significant differences were observed for the relative enhancement (p < 0.05 for all). Using ROC curves, the optimal threshold value of absolute enhancement to diagnose acute myocarditis was 2.05 (sensitivity: 86%; specificity: 81%). Given the simplicity of use, contrast-enhanced cine-SSFP sequences should be used as an additional diagnostic tool to detect hyperemia in acute myocarditis patients.

A 72-channel receive array coil allows whole-heart cine MRI in two breath holds

BACKGROUND

A new 72-channel receive array coil and sensitivity encoding, compressed (C-SENSE) and noncompressed (SENSE), were investigated to decrease the number of breath-holds (BHs) for cardiac magnetic resonance (CMR).

METHODS

Three-T CMRs were performed using the 72-channel coil with SENSE-2/4/6 and C-SENSE-2/4/6 accelerated short-axis cine two-dimensional balanced steady-state free precession sequences. A 16-channel coil with SENSE-2 served as reference. Ten healthy subjects were included. BH-time was kept under 15 s. Data were compared in terms of image quality, biventricular function, number of BHs, and scan times.

RESULTS

BHs decreased from 7 with C-SENSE-2 (scan time 70 s, 2 slices/BH) to 3 with C-SENSE-4 (scan time 42 s, 4-5 slices/BH) and 2 with C-SENSE-6 (scan time 28 s, 7 slices/BH). Compared to reference, image sharpness was similar for SENSE-2/4/6, slightly inferior for C-SENSE-2/4/6. Blood-to-myocardium contrast was unaffected. C-SENSE-4/6 was given lower qualitative median scores, but images were considered diagnostically adequate to excellent, with C-SENSE-6 suboptimal. Biventricular end-diastolic (EDV), end-systolic (ESV) and stroke volumes, ejection fractions (EF), cardiac outputs, and left ventricle (LV)-mass were similar for SENSE-2/4/6 with no systematic bias and clinically appropriate limits of agreements. C-SENSE slightly underestimated LV-EDV (-6.38 ± 6.0 mL, p < 0.047), LV-ESV (-7.94 ± 6.0 mL, p < 0.030) and overestimated LV-EF (3.16 ± 3.10%; p < 0.047) with C-SENSE-4. Bland-Altman analyses revealed minor systematic biases in these variables with C-SENSE-2/4/6 and for LV-mass with C-SENSE-6.

CONCLUSIONS

Using the 72-channel coil, short-axis CMR for quantifying biventricular function was feasible in two BHs where SENSE slightly outperformed C-SENSE.

Bi-ventricular assessment with cardiovascular magnetic resonance at 5 Tesla: A pilot study

Background

Cardiovascular magnetic resonance (CMR) imaging at ultra-high fields (UHF) such as 7T has encountered many challenges such as faster T2* relaxation, stronger B₀ and B₁₊ field inhomogeneities and additional safety concerns due to increased specific absorption rate (SAR) and peripheral nervous stimulation (PNS). Recently, a new line of 5T whole body MRI system has become available, and this study aims at evaluating the performance and benefits of this new UHF system for CMR imaging.

Methods

Gradient echo (GRE) CINE imaging was performed on healthy volunteers at both 5 and 3T, and was compared to balanced steady-state-free-procession (bSSFP) CINE imaging at 3T as reference. Higher spatial resolution GRE CINE scans were additionally performed at 5T. All scans at both fields were performed with ECG-gating and breath-holding. Image quality was blindly evaluated by two radiologists, and the cardiac functional parameters (e.g., EDV/ESV/mass/EF) of the left and right ventricles were measured for statistical analyses using the Wilcoxon signed-rank test and Bland-Altman analysis.

Results

Compared to 3T GRE CINE imaging, 5T GRE CINE imaging achieved comparable or improved image quality with significantly superior SNR and CNR, and it has also demonstrated excellent capability for high resolution (1.0 × 1.0 × 6.0 mm³) imaging. Functional assessments from 5T GRE CINE images were highly similar with the 3T bSSFP CINE reference.

Conclusions

This pilot study has presented the initial evaluation of CMR CINE imaging at 5T UHF, which yielded superior image quality and accurate functional quantification when compared to 3T counterparts. Along with reliable ECG gating, the new 5T UHF system has the potential to achieve well-balanced performance for CMR applications.

Implementation and prospective clinical validation of AI-based planning and shimming techniques in cardiac MRI

PURPOSE

Cardiovascular magnetic resonance (CMR) is a vital diagnostic tool in the management of cardiovascular diseases. The advent of advanced CMR technologies combined with artificial intelligence (AI) has the potential to simplify imaging, reduce image acquisition time without compromising image quality (IQ), and improve magnetic field uniformity. Here, we aim to implement two AI-based deep learning techniques for automatic slice alignment and cardiac shimming and evaluate their performance in clinical cardiac magnetic resonance imaging (MRI).

METHODS

Two deep neural networks were developed, trained, and validated on pre-acquired cardiac MRI datasets (>500 subjects) to achieve automatic slice planning and shimming (implemented in the scanner) for CMR. To examine the performance of our automated cardiac planning (EasyScan) and AI-based shim (AI shim), two prospective studies were performed subsequently. For the EasyScan validation, 10 healthy subjects underwent two identical CMR protocols: with manual cardiac planning and with AI-based EasyScan to assess protocol scan time difference and accuracy of cardiac plane prescriptions on a 1.5 T clinical MRI scanner. For the AI shim validation, a total of 20 subjects were recruited: 10 healthy and 10 cardio-oncology patients with referrals for a CMR examination. Cine images were obtained with standard cardiac volume shim and with AI shim to assess signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), overall IQ (sharpness and MR image degradation), ejection fraction (EF), and absolute wall thickening. A hybrid statistical method using of nonparametric (Wilcoxon) and parametric (t-test) assessments was employed for statistical analyses.

RESULTS

CMR protocol with AI-based plane prescriptions, EasyScan, minimized operator dependence and reduced overall scanning time by over 2 min (∼13 % faster, p < 0.001) compared to the protocol with manual cardiac planning. EasyScan plane prescriptions also demonstrated more accurate (less plane angulation errors from planes manually prescribed by a certified cardiac MRI technologist) cardiac planes than previously reported strategies. Additionally, AI shim resulted in improved B0 field homogeneity. Cine images obtained with AI shim revealed a significantly higher SNR (12.49%; p = 0.002) than those obtained with volume shim (volume shim: 32.90 ± 7.42 vs. AI shim: 37.01 ± 8.87) for the left ventricle (LV) myocardium. LV myocardium CNR was 12.48% higher for cine imaging with AI shim (149.02 ± 39.15) than volume shim (132.49 ± 33.94). Images obtained with AI shim resulted in sharper images than those obtained with volume shim (p = 0.012). The LVEF and absolute wall thickening also showed that differences exist between the two shimming methods. The LVEF by AI shim was shown to be slightly larger than LVEF by volume shim in two groups: 2.87% higher with AI shim for the healthy group and 1.70% higher with AI shim for the patient group. The LV absolute wall thickening (in mm) also showed that differences exist between shimming methods for each group with larger changes observed in the patient group (healthy: 3.31%, p = 0.234 and patient group: 7.29%, p = 0.059).

CONCLUSIONS

CMR exams using EasyScan for cardiac planning demonstrated accelerated cardiac exam compared to the CMR protocol with manual cardiac planning. Improved and more uniform B0 magnetic field homogeneity also achieved using AI shim technique compared to volume shimming.

Feasibility of Three-Dimensional Balanced Steady-State Free Precession Cine Magnetic Resonance Imaging Combined with an Image Denoising Technique to Evaluate Cardiac Function in Children with Repaired Tetralogy of Fallot

Objective

To investigate the feasibility of cine three-dimensional (3D) balanced steady-state free precession (b-SSFP) imaging combined with a non-local means (NLM) algorithm for image denoising in evaluating cardiac function in children with repaired tetralogy of Fallot (rTOF).

Materials and Methods

Thirty-five patients with rTOF (mean age, 12 years; range, 7–18 years) were enrolled to undergo cardiac cine image acquisition, including two-dimensional (2D) b-SSFP, 3D b-SSFP, and 3D b-SSFP combined with NLM. End-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV), and ejection fraction (EF) of the two ventricles were measured and indexed by body surface index. Acquisition time and image quality were recorded and compared among the three imaging sequences.

Results

3D b-SSFP with denoising vs. 2D b-SSFP had high correlation coefficients for EDV, ESV, SV, and EF of the left (0.959–0.991; p < 0.001) as well as right (0.755–0.965; p < 0.001) ventricular metrics. The image acquisition time ± standard deviation (SD) was 25.1 ± 2.4 seconds for 3D b-SSFP compared with 277.6 ± 0.7 seconds for 2D b-SSFP, indicating a significantly shorter time with the 3D than the 2D sequence (p < 0.001). Image quality score was better with 3D b-SSFP combined with denoising than with 3D b-SSFP (mean ± SD, 3.8 ± 0.6 vs. 3.5 ± 0.6; p = 0.005). Signal-to-noise ratios for blood and myocardium as well as contrast between blood and myocardium were higher for 3D b-SSFP combined with denoising than for 3D b-SSFP (p < 0.05 for all but septal myocardium).

Conclusion

The 3D b-SSFP sequence can significantly reduce acquisition time compared to the 2D b-SSFP sequence for cine imaging in the evaluation of ventricular function in children with rTOF, and its quality can be further improved by combining it with an NLM denoising method.

Cardiovascular Magnetic Resonance in Right Heart and Pulmonary Circulation Disorders

Right heart and pulmonary circulation disorders are generally caused by right ventricle (RV) pressure overload, volume overload, and cardiomyopathy, and they are associated with distinct clinical courses and therapeutic approaches, although they often may coexist. Cardiac magnetic resonance (CMR) provides a noninvasive accurate and reproducible multiplanar anatomic and functional assessment, tissue characterization, and blood flow evaluation of the right heart and pulmonary circulation. This article reviews the current status of the CMR, the most recent techniques, the new parameters and their clinical utility in diagnosis, prognosis, and therapeutic management in the right heart and pulmonary circulation disorders.

A pilot study of bladder voiding with real-time MRI and computational fluid dynamics

Lower urinary track symptoms (LUTS) affect many older adults. Multi-channel urodynamic studies provide information about bladder pressure and urinary flow but offer little insight into changes in bladder anatomy and detrusor muscle function. Here we present a novel method for real time MRI during bladder voiding. This was performed in a small cohort of healthy men and men with benign prostatic hyperplasia and lower urinary tract symptoms (BPH/LUTS) to demonstrate proof of principle; The MRI urodynamic protocol was successfully implemented, and bladder wall displacement and urine flow dynamics were calculated. Displacement analysis on healthy controls showed the greatest bladder wall displacement in the dome of the bladder while men with BPH/LUTS exhibited decreased and asymmetric bladder wall motion. Computational fluid dynamics of voiding showed men with BPH/LUTS had larger recirculation regions in the bladder. This study demonstrates the feasibility of performing MRI voiding studies and their potential to provide new insight into lower urinary tract function in health and disease.

Feasibility of ventricular volumetry by cardiovascular MRI to assess cardiac function in the fetal sheep

KEY POINTS

The application of fetal cardiovascular magnetic resonance imaging (CMR) to assess fetal cardiovascular physiology and cardiac function through the quantification of ventricular volumes has previously been investigated, but the approach has not yet been fully validated. Ventricular output measurements calculated from heart rate and stroke volumes (SV) of the right and left ventricles measured by ventricular volumetry (VV) exhibited a high level of agreement with phase-contrast (PC) blood flow measurements in the main pulmonary artery and ascending aorta, respectively. Ejection fraction of the right ventricle, which is lower than that of the left ventricle in postnatal subjects, was similar to the left ventricular ejection fraction in the fetus; probably due to the different loading conditions present in the fetal circulation. This study provides evidence to support the reliability of VV in the sheep fetus, providing evidence for its use in animal models of human diseases affecting the fetal circulation.

ABSTRACT

The application of ventricular volumetry (VV) by cardiovascular magnetic resonance imaging (CMR) in the fetus remains challenging due to the small size of the fetal heart and high heart rate. The reliability of this technique in utero has not yet been established. The aim of this study was to assess the feasibility and reliability of VV in a fetal sheep model of human pregnancy. Right and left ventricular outputs by stroke volume (SV) measured using VV were compared with 2D phase-contrast (PC) CMR measurements of blood flow in the main pulmonary artery (MPA) and ascending aorta (AAo). At 124-140 days (d) gestation, singleton bearing Merino ewes underwent CMR under general anaesthesia using fetal femoral artery catheters, implanted at 109-117d, to trigger cine steady state free precession acquisitions of ventricular short-axis stacks. The short-axis cine stacks were segmented at end-systole and end-diastole, yielding right and left ventricular SV, ejection fraction, and cardiac outputs (SV × heart rate). PC cine acquisitions of MPA and AAo were analysed to measure blood flow, which served as comparators for the right and left cardiac outputs by VV. There was good correlation and agreement between VV and PC measures of ventricular outputs with no significant bias (r²  = 0.926; P < 0.0001; Bias = -4.7 ± 10.5 ml min^-1  kg^-1 ; 95% limits of agreement: -15.9 to 25.2 ml min^-1  kg^-1 ). This study validates fetal VV by CMR in a large animal model of human pregnancy and provides preliminary reference values of fetal sheep right and left ventricles in late gestation.

Simple Identification of Cerebrospinal Fluid Turbulent Motion Using a Dynamic Improved Motion-sensitized Driven-equilibrium Steady-state Free Precession Method Applied to Various Types of Cerebrospinal Fluid Motion Disturbance

The motion of cerebrospinal fluid (CSF) within the subarachnoid space and ventricles is greatly modulated when propagating synchronously with the cardiac pulse and respiratory cycle and path through the nerves, blood vessels, and arachnoid trabeculae. Water molecule movement that propagates between two spaces via a stoma, foramen, or duct presents increased acceleration when passing through a narrow area and can exhibit “turbulence.” Recently, neurosurgeons have started to perform fenestration procedures using neuroendoscopy to treat hydrocephalus and cystic lesions. As part of the postoperative evaluation, a noninvasive diagnostic technique to visualize the water molecules at the fenestrated site is necessary. Because turbulence is observed at this fenestrated site, an imaging technique appropriate for observing this turbulence is essential. We therefore investigated the usefulness of a dynamic improved motion-sensitized driven-equilibrium steady-state free precession (Dynamic iMSDE SSFP) sequence of magnetic resonance imaging that is superior for ascertaining turbulent motions in healthy volunteers and patients. Images of Dynamic iMSDE SSFP from volunteers revealed that CSF motion at the ventral surface of the brainstem and the third ventricle is augmented and turbulent. Moreover, our findings confirmed that this technique is useful for evaluating treatments that utilize neuroendoscopy. As a result, Dynamic iMSDE SSFP, a simple sequence for visualizing CSF motion, entails a short imaging time, can extensively visualize CSF motion, does not require additional processes such as labeling or trigger setting, and is anticipated to have wide-ranging clinical applications in the future.

Atrial mechanics and their prognostic impact in Takotsubo syndrome: a cardiovascular magnetic resonance imaging study

Aims

The exact pathophysiology of Takotsubo syndrome (TTS) remains not fully understood with most studies focussing on ventricular pathology. Since atrial involvement may have a significant role, we assessed the diagnostic and prognostic potential of atrial cardiovascular magnetic resonance feature tracking (CMR-FT) in TTS.

Methods and results

This multicentre study recruited 152 TTS patients who underwent CMR on average within 3 days after hospitalization. Reservoir [total strain εs and peak positive strain rate (SR) SRs], conduit (passive strain εe and peak early negative SRe), and booster pump function (active strain εa and peak late negative SRa) were assessed in a core laboratory. Results were compared with 21 control patients with normal biventricular function. A total of 20 patients underwent follow-up CMR (median 3.5 months, interquartile range 3–5). All patients were approached for general follow-up. Left atrial (LA) but not right atrial (RA) reservoir and conduit function were impaired during the acute phase (εs: P = 0.043, εe: P < 0.001, SRe: P = 0.047 vs. controls) and recovered until follow-up (εs: P < 0.001, SRs: P = 0.04, εe: P = 0.001, SRe: P = 0.04). LA and RA booster pump function were increased in the acute setting (LA-εa: P = 0.045, SRa: P = 0.002 and RA-εa: P = 0.004, SRa: P = 0.002 vs. controls). LA-εs predicted mortality [hazard ratio 1.10, 95% confidence interval (CI) 1.01–1.20; P = 0.037] irrespectively of established cardiovascular risk factors (P = 0.019, multivariate analysis) including left ventricular ejection fraction (LVEF) (area under the curve 0.71, 95% CI 0.55–0.86, P = 0.048).

Conclusion

TTS pathophysiology comprises transient impairments in LA reservoir and conduit functions and enhanced bi-atrial active booster pump functions. Atrial CMR-FT may evolve as a superior marker of adverse events over and above established parameters such as LVEF and atrial volume.

Magnetic Resonance Imaging of Contracting Ultrathin Cardiac Tissue

OBJECTIVE

Integrating cardiac-tissue patches into the beating heart and evaluating the long-term effects of such integration on cardiac contractility are two challenges in an emerging field of regenerative medicine. This pilot study presents tools for the imaging of contracting multicellular cardiac tissue constructs (MTCs) in vitro and demonstrates the feasibility of tracking the early development of strand geometry and contractions in ultrathin strands and layers of cardiac tissue using CINE MRI.

APPROACH

Cultured, ultrathin (~50-100-micron) MTCs of rat neonatal cardiomyocytes were plated in rectangular cell chambers (4.5 × 2.0 cm) with and without ultrathin, carbon EP electrodes embedded in the floor of the cell chamber. Two-dimensional, steady-state free precession (SSFP) CINE MRI, cell microscopy, and tissue photography were performed on Days 5-9 of cell development. Potential confounders and MRI artifacts were evaluated using non-contracting cardiac tissues and cell-free chambers filled with the cell-culture medium.

MAIN RESULTS

Synchronized contractions formed by Day 7; individual contracting tissue strands became identifiable by Day 9. The global patterns and details of the strand geometry and movement patterns in the SSFP images were in excellent agreement with microscopic and photographic images. No synchronized movement was identifiable by either microscopy or CINE MRI in the non-contracting MTCs or the cell-free medium. The EP recordings revealed well-defined depolarization and repolarization waveforms; the imaging artifacts generated by the carbon electrodes were small.

SIGNIFICANCE

This pilot study demonstrates the feasibility of imaging cardiac-strand patterns and contractile activity in ultrathin, two-dimensional cardiac tissue in commonly used clinical scanners.

Cardiorespiratory motion-tracking via self-refocused rosette navigators

PURPOSE

To develop a flexible method for tracking respiratory and cardiac motions throughout MR and PET-MR body examinations that requires no additional hardware and minimal sequence modification.

METHODS

The incorporation of a contrast-neutral rosette navigator module following the RF excitation allows for robust cardiorespiratory motion tracking with minimal impact on the host sequence. Spatial encoding gradients are applied to the FID signal and the desired motion signals are extracted with a blind source separation technique. This approach is validated with an anthropomorphic, PET-MR-compatible motion phantom as well as in 13 human subjects.

RESULTS

Both respiratory and cardiac motions were reliably extracted from the proposed rosette navigator in phantom and patient studies. In the phantom study, the MR-derived motion signals were additionally validated against the ground truth measurement of diaphragm displacement and left ventricle model triggering pulse.

CONCLUSION

The proposed method yields accurate respiratory and cardiac motion-state tracking, requiring only a short (1.76 ms) additional navigator module, which is self-refocusing and imposes minimal constraints on sequence design.

Prevalence of left ventricle non-compaction criteria in adult patients with bicuspid aortic valve versus healthy control subjects

Objective

The aim of this study was to compare the prevalence of left ventricle non-compaction (LVNC) criteria (or hypertrabeculation) in a cohort of patients with bicuspid aortic valve (BAV) and healthy control subjects (CTL) without cardiovascular disease using cardiovascular MR (CMR).

Methods

79 patients with BAV and 85 CTL with tricuspid aortic valve and free of known cardiovascular disease underwent CMR to evaluate the presence of LVNC criteria. The left ventricle was assessed at end-systole and end-diastole, in the short-axis, two-chamber and four-chamber views and divided into the 16 standardised myocardial segments. LVNC was assessed using the non-compacted/compacted (NC/C) myocardium ratio and was considered to be present if at least one of the myocardial segments had a NC/C ratio superior to the cut-off values defined in previous studies: Jenni et al (>2.0 end-systole); Petersen et al (>2.3 end-diastole); or Fazio et al (>2.5 end-diastole).

Results

15 CTL (17.6%) vs 8 BAV (10.1%) fulfilled Jenni et al’s criterion; 69 CTL (81.2%) vs 49 BAV (62.0%) fulfilled Petersen et al’s criterion; and 66 CTL (77.6%) vs 43 BAV (54.4%) fulfilled Fazio et al’s criterion. Petersen et al and Fazio et al’s LVNC criteria were met more often by CTL (p=0.006 and p=0.002, respectively) than patients with BAV, whereas this difference was not statistically significant according to Jenni et al’s criterion (p=0.17). In multivariable analyses, after adjusting for age, sex, the presence of significant valve dysfunction (>mild stenosis or >mild regurgitation), indexed LV mass, indexed LV end-diastolic volume and LV ejection fraction, BAV was not associated with any of the three LVNC criteria.

Conclusion

Patients with BAV do not harbour more LVNC than the general population and there is no evidence that they are at higher risk for the development of LVNC cardiomyopathy.

CMR First-Pass Perfusion for Suspected Inducible Myocardial Ischemia

Cardiovascular magnetic resonance (CMR) has evolved from a pioneering research tool to an established noninvasive imaging method for detecting inducible myocardial perfusion deficits. In this consensus document, experts of different imaging techniques summarize the existing body of evidence regarding CMR perfusion as a viable complement to other established noninvasive tools for the assessment of perfusion and discuss the advantages and pitfalls of the technique. A rapid, standardized CMR perfusion protocol is described, which is safe, clinically feasible, and cost-effective for centers with contemporary magnetic resonance equipment. CMR perfusion can be recommended as a routine diagnostic tool to identify inducible myocardial ischemia.

Cardiac Magnetic Resonance Imaging Using an Open 1.0T MR Platform: A Comparative Study with a 1.5T Tunnel System

Background

Cardiac magnetic resonance imaging (cMRI) has become the non-invasive reference standard for the evaluation of cardiac function and viability. The introduction of open, high-field, 1.0T (HFO) MR scanners offers advantages for examinations of obese, claustrophobic and paediatric patients.The aim of our study was to compare standard cMRI sequences from an HFO scanner and those from a cylindrical, 1.5T MR system.

Material/Method

Fifteen volunteers underwent cMRI both in an open HFO and in a cylindrical MR system. The protocol consisted of cine and unenhanced tissue sequences. The signal-to-noise ratio (SNR) for each sequence and blood-myocardium contrast for the cine sequences were assessed. Image quality and artefacts were rated. The location and number of non-diagnostic segments was determined. Volunteers' tolerance to examinations in both scanners was investigated.

Results

SNR was significantly lower in the HFO scanner (all p<0.001). However, the contrast of the cine sequence was significantly higher in the HFO platform compared to the 1.5T MR scanner (0.685±0.41 vs. 0.611±0.54; p<0.001). Image quality was comparable for all sequences (all p>0.05). Overall, only few non-diagnostic myocardial segments were recorded: 6/960 (0.6%) by the HFO and 17/960 (1.8%) segments by the cylindrical system. The volunteers expressed a preference for the open MR system (p<0.01).

Conclusions

Standard cardiac MRI sequences in an HFO platform offer a high image quality that is comparable to the quality of images acquired in a cylindrical 1.5T MR scanner. An open scanner design may potentially improve tolerance of cardiac MRI and therefore allow to examine an even broader patient spectrum.

Image Quality of Cardiac Magnetic Resonance Imaging in Patients With an Implantable Cardioverter Defibrillator System Designed for the Magnetic Resonance Imaging Environment

BACKGROUND

Recently, magnetic resonance (MR)-conditional implantable cardioverter defibrillator (ICD) systems have become available. However, associated cardiac MR image (MRI) quality is unknown. The goal was to evaluate the image quality performance of various cardiac MR sequences in a multicenter trial of patients implanted with an MR-conditional ICD system.

METHODS AND RESULTS

The Evera-MRI trial enrolled 275 patients in 42 centers worldwide. There were 263 patients implanted with an Evera-MRI single- or dual-chamber ICD and randomized to controls (n=88) and MRI (n=175), 156 of whom underwent a protocol-required MRI (9-12 weeks post implant). Steady-state-free-precession (SSFP) and fast-gradient-echo (FGE) sequences were acquired in short-axis and horizontal long-axis orientations. Qualitative and quantitative assessment of image quality was performed by using a 7-point scale (grades 1-3: good quality, grades 6-7: nondiagnostic) and measuring ICD- and lead-related artifact size. Good to moderate image quality (grades 1-5) was obtained in 53% and 74% of SSFP and FGE acquisitions, respectively, covering the left ventricle, and in 69% and 84%, respectively, covering the right ventricle. Odds for better image quality were greater for right ventricle versus left ventricle (odds ratio, 1.8; 95% confidence interval, 1.5-2.2; P<0.0001) and greater for FGE versus SSFP (odds ratio, 3.5; 95% confidence interval, 2.5-4.8; P<0.0001). Compared with SSFP, ICD-related artifacts on FGE were smaller (141±65 versus 75±57 mm, respectively; P<0.0001). Lead artifacts were much smaller than ICD artifacts (P<0.0001).

CONCLUSIONS

FGE yields good to moderate quality in 74% of left ventricle and 84% of right ventricle acquisitions and performs better than SSFP in patients with an MRI-conditional ICD system. In these patients, cardiac MRI can offer diagnostic information in most cases.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT02117414.

When should we use contrast material in cardiac MRI?

At present, most of the cardiac magnetic resonance imaging (MRI) examinations rely on contrast-enhanced protocols, but noncontrast alternatives are emerging. Late gadolinium enhancement (LGE) imaging for the detection of myocardial scar can be considered the main cause for the embedding of cardiac MRI into the clinical routine. The novel noncontrast technique of native T₁ mapping shows promise for tissue characterization in ischemic and nonischemic cardiomyopathy and may provide additional information over conventional LGE imaging. Technical issues, including measurements variability, still need to be resolved to facilitate a wide clinical application. Ischemia detection can be performed with contrast-based stress perfusion and contrast-free stress wall motion imaging. For coronary magnetic resonance angiography (MRA), protocols with and without contrast material have been developed. Research on coronary atherosclerotic plaque characterization has introduced new applications of contrast material. For MRA of the aorta, which traditionally relied on contrast administration, several noncontrast protocols have become available. This review provides an overview of when to use contrast material in cardiac and cardiac-related vascular MRI, summarizes the major imaging building blocks, and describes the diagnostic value of the available contrast-enhanced and noncontrast techniques. Contrast material in cardiac MRI should be used for LGE imaging for tissue characterization in ischemic or nonischemic cardiomyopathy and may be used for stress perfusion imaging for the detection of ischemia. In cardiac-related vascular MRI, use of contrast material should be avoided, unless high-quality angiography is required that cannot be obtained with noncontrast protocols.

LEVEL OF EVIDENCE

5 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2017;46:1551-1572.

Flip angle optimization for balanced SSFP: Cardiac cine imaging following the application of standard extracellular contrast agent (gadobutrol)

PURPOSE

To investigate the effect of the flip angle (FA) on the blood-myocardium contrast and to define the FA leading to highest image quality in contrast-enhanced balanced steady-state free precession (bSSFP) images. bSSFP images provide excellent contrast between myocardium and blood with high signal-to-noise and contrast-to-noise ratios (SNR, CNR). In clinical practice, bSSFP images are typically acquired following the injection of extracellular contrast agents (ECAs), although ECAs decrease the blood-myocardium contrast.

MATERIALS AND METHODS

First, a theoretical optimization was performed to determine the FA that maximizes CNR in bSSFP imaging 2-20 minutes after application of ECA. Second signal-ratios, contrast, SNR, and CNR were assessed in vivo in 25 patients in bSSFP images at 1.5T acquired before (FA = 50°) and 10-15 minutes after (FAs = 50°, 80°, 90°, 100°) application of a double-dose contrast agent. Image quality was assessed by two readers.

RESULTS

Simulations yielded FAs in the range of 85-100° for optimal CNR in contrast-enhanced images. In vivo comparison of conventionally acquired cine images (FA 50°) showed an increase in CNR between blood and myocardium by 57% in diastole and 78% in systole in adapted contrast-enhanced bSSFP images (FA 100°). Contrast-enhanced images with an FA of 100° were rated highest in image quality assessment.

CONCLUSION

By means of FA adaptation a similar blood-myocardium contrast can be achieved in contrast-enhanced bSSFP as in unenhanced bSSFP imaging with an increase in CNR.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;47:255-261.

Cardiovascular magnetic resonance in systemic sclerosis: "Pearls and pitfalls"

Systemic sclerosis (SSc) is an autoimmune disease characterized by vascular dysfunction and excessive fibrosis, involving internal organs including the heart. The estimated prevalence of cardiac involvement in SSc is high and remains subclinical until the late stages. It is either primary, related to myocardial inflammation and fibrosis, or secondary, due to pulmonary arterial hypertension (SSc-PAH) or systemic hypertension, in those patients with renal involvement. Cardiovascular magnetic resonance (CMR) is a useful tool for the early assessment of cardiac involvement in SSc. It is the gold standard technique to assess ventricular volumes,ejection fraction, and in particular is very useful to reliably and non-invasively detect myocardial inflammation, early perfusion defects, and myocardial fibrosis. However, the CMR evaluation in SSc may be problematic, because of cardiac and respiratory artefacts, commonly found in these patients. Therefore, a high level of expertise is necessary for both acquisition and interpretation of CMR images in SSc.

Considerations for Imaging the Inferior Vena Cava (IVC) with/without IVC Filters

Deep venous thrombosis (DVT), thrombosis of the inferior vena cava, and pulmonary embolism (PE) constitute a continuum that includes venous thromboembolic (VTE) disease. VTE is the third most common cardiovascular disorder that affects all races, ethnicities, gender, and ages. VTE predominantly affects the elderly population, exponentially increasing in incidence with increasing age. Venous thromboembolism is not only a singular event but a chronic disease and has been found to have a rate of recurrence approaching 40% among all patients after 10 years. Whether symptomatic or asymptomatic, once thromboembolism is suspected, objective methods are required for the accurate and confirmatory presence of a thrombus with imaging as the next step in the diagnostic algorithm. Imaging also allows for the determination of the extent of clot burden, clot propagation, occlusive versus nonocclusive thrombus, acute versus chronic thrombus, or in some cases thrombus recurrence versus thrombophlebitis. Vena caval filter placement is, in some instances, required to prevent a significant subsequent VTE event. Placement of these therapeutic devices paradoxically promotes thrombus formation, and other sequelae may arise from the placement of inferior vena cava filters. In this article, the authors provide an overview of available techniques for imaging the vena cava with or without a filter and discuss advantages and drawbacks for each.

Historical Evolution of Imaging Techniques for the Evaluation of Pulmonary Embolism

As we celebrate the 100th anniversary of the founding of the Radiological Society of North America (RSNA), it seems fitting to look back at the major accomplishments of the radiology community in the diagnosis of pulmonary embolism. Few diseases have so consistently captured the attention of the medical community. Since the first description of pulmonary embolism by Virchow in the 1850s, clinicians have struggled to reach a timely diagnosis of this common condition because of its nonspecific and often confusing clinical picture. As imaging tests started to gain importance in the 1900s, the approach to diagnosing pulmonary embolism also began to change. Rapid improvements in angiography, ventilation-perfusion imaging, and cross-sectional imaging modalities such as computed tomography (CT) and magnetic resonance imaging have constantly forced health care professionals to rethink how they diagnose pulmonary embolism. Needless to say, the way pulmonary embolism is diagnosed today is distinctly different from how it was diagnosed in Virchow's era; and imaging, particularly CT, now forms the cornerstone of diagnostic evaluation. Currently, radiology offers a variety of tests that are fast and accurate and can provide anatomic and functional information, thus allowing early diagnosis and triage of cases. This review provides a historical journey into the evolution of these imaging tests and highlights some of the major breakthroughs achieved by the radiology community and RSNA in this process. Also highlighted are areas of ongoing research and development in this field of imaging as radiologists seek to combat some of the newer challenges faced by modern medicine, such as rising health care costs and radiation dose hazards.

Role of Imaging Techniques for Diagnosis, Prognosis and Management of Heart Failure Patients: Cardiac Magnetic Resonance

Cardiac magnetic resonance (CMR) has evolved into a major tool for the diagnosis and assessment of prognosis of patients suffering from heart failure. Anatomical and structural imaging, functional assessment, T1 and T2 mapping tissue characterization, and late gadolinium enhancement (LGE) have provided clinicians with tools to distinguish between non-ischemic and ischemic cardiomyopathies and to identify the etiology of non-ischemic cardiomyopathies. LGE is a useful tool to predict the likelihood of functional recovery after revascularization in patients with CAD and to guide the left ventricular (LV) lead placement in those who qualify for cardiac resynchronization (CRT) therapy. In addition, the presence of LGE and its extent in myocardial tissue relate to overall cardiovascular outcomes. Emerging roles for cardiac imaging in heart failure with preserved ejection fraction (HFpEF) are being studied, and CMR continues to be among the most promising noninvasive imaging alternatives in the diagnosis of this disease.

[Prognostic value of cardiovascular MRI in diabetics]

CLINICAL/METHODICAL ISSUE

Despite an increased cardiovascular risk in patients with diabetes mellitus they are a heterogeneous population with very different individual manifestation of diseases; therefore, a profound stratification is recommended.

STANDARD METHODS

Clinical examinations and blood biomarkers are typically used in diabetic patients to determine the risk for developing cardio-cerebrovascular events.

METHODICAL INNOVATIONS

Cardiac as well as whole-body magnetic resonance imaging (MRI) including cardiovascular sequences are established methods for clinical diagnostics. Their significance in predicting the outcome and the corresponding risk stratification for patients with diabetes is becoming increasingly more important based on recent study results.

PERFORMANCE

Late gadolinium enhancement (LGE) in cardiac MRI detects silent myocardial ischemia in up to 30% of diabetic patients, which is associated with a hazard ratio of 3-6 for cardiovascular events. Regional left ventricular wall motion abnormalities and decreased ejection fraction also have a prognostic value in diabetics. Based on whole-body MRI, the vessel score as well as carotid artery stenosis have been evaluated as additional predictors for cardio-cerebrovascular events.

ACHIEVEMENTS

The MRI-based predictors have independent and incremental prognostic value beyond traditional risk stratification for cardio-cerebrovascular events; however, only the comprehensive assessment of whole-body MRI including angiography allows the identification of patients who remain free of cardio-cerebrovascular events over a period of 6 years.

PRACTICAL RECOMMENDATIONS

Cardiac MRI, particularly the detection of LGE, can be recommended for risk stratification of patients with diabetes mellitus. The clinical relevance of the added prognostic value of whole-body MRI needs to be clarified in further studies.

Whole-Body MR Imaging in the German National Cohort: Rationale, Design, and Technical Background

PURPOSE

To detail the rationale, design, and future perspective of implementing whole-body magnetic resonance (MR) imaging in the German National Cohort, a large multicentric population-based study.

MATERIALS AND METHODS

All institutional review boards approved the study, and informed consent is obtained before study enrollment. Participants are enrolled from a random sample of the general population at five dedicated imaging sites among 18 recruitment centers. MR imaging facilities are equipped with identical 3.0-T imager technology and use uniform MR protocols. Imager-specific hardware and software settings remained constant over the study period. On-site and centralized measures of image quality enable monitoring of completeness of the acquisitions and quality of each of the MR sequences. Certified radiologists read all MR imaging studies for presence of incidental findings according to predefined algorithms.

RESULTS

Over a 4-year period, six participants per day are examined at each center, totaling a final imaging cohort of approximately 30 000 participants. The MR imaging protocol is identical for each site and comprises a set of 12 native series to cover neurologic, cardiovascular, thoracoabdominal, and musculoskeletal imaging phenotypes totaling approximately 1 hour of imaging time. A dedicated analysis platform as part of a central imaging core incorporates a thin client-based integrative and modular data handling platform to enable multicentric off-site image reading for incidental findings. Scientific analysis will be pursued on a per-project hypothesis-driven basis.

CONCLUSION

Population-based whole-body MR imaging as part of the German National Cohort will serve to compile a comprehensive image repository, will provide insight into physiologic variants and subclinical disease burden, and has the potential to enable identification of novel imaging biomarkers of risk.

High-dose dobutamine stress steady-state free precession (SSFP) cine MRI at 3T with patient adaptive local radiofrequency (RF) shimming using dual-source RF transmission

PURPOSE

To prospectively assess the feasibility, image quality, and diagnostic accuracy of high-dose dobutamine stress magnetic resonance imaging (DSMR) using steady-state free precession (SSFP) cine imaging at 3T applying a dual-source radiofrequency (RF) excitation magnetic resonance imaging (MRI) system with parallel transmission and patient adaptive local RF shimming.

MATERIALS AND METHODS

DSMR using SSFP cine imaging was performed in 44 patients at 3T scheduled for a clinically indicated coronary angiography. The effect of conventional versus dual-source RF transmission was assessed regarding homogeneity of the B1 field, contrast-to-noise ratios (CNRs) at rest, image quality, and diagnostic accuracy of DSMR using long and short axis.

RESULTS

The mean percentage of the intended flip angle within the heart increased from 88 ± 9.1% with single-source to 103 ± 5.6% (P < 0.001) dual-source RF transmission. CNR increased for dual-source particularly at the apex (63.4 ± 24.2 vs. 36.5 ± 16.5, P < 0.001) but also at the base of the left ventricle (LV) (50.1 ± 14.8 vs. 39.3 ± 15.8, P < 0.001). Image quality of dual-source was higher both at rest (2.8 ± 0.5 vs. 2.6 ± 0.7, P < 0.001) and stress (2.5 ± 0.7 vs. 2.0 ± 1.0, P < 0.001). The number of segments with severe artifacts or nondiagnostic image quality at stress was lower with dual-source RF transmission (8% vs. 27%, P < 0.001). The diagnostic accuracy of DSMR in coronary territories using dual-source RF transmission was significantly higher (77% vs. 65%, P = 0.04).

CONCLUSION

Patient adaptive local RF shimming using dual-source RF transmission provided significantly improved image quality and higher diagnostic accuracy of SSFP during DSMR at 3T compared to conventional RF transmission.

Usefulness of cardiac MRI in the prognosis and follow-up of ischemic heart disease

Cardiac magnetic resonance imaging (MRI) is an important tool that makes it possible to evaluate patients with cardiovascular disease; in addition to infarction and alterations in myocardial perfusion, cardiac MRI is useful for evaluating other phenomena such as microvascular obstruction and ischemia. The main prognostic factors in cardiac MRI are ventricular dysfunction, necrosis in late enhancement sequences, and ischemia in stress sequences. In acute myocardial infarction, cardiac MRI can evaluate the peri-infarct zone and quantify the size of the infarct. Furthermore, cardiac MRI's ability to detect and evaluate microvascular obstruction makes it a fundamental tool for establishing the prognosis of ischemic heart disease. In patients with chronic ischemic heart disease, cardiac MRI can detect ischemia induced by pharmacological stress and can diagnose infarcts that can be missed on other techniques.

Dual-source RF transmission in cardiac SSFP imaging at 3 T: systematic spatial evaluation of image quality improvement compared to conventional RF transmission

The purpose of this investigation was to systematically evaluate the spatial distribution of image quality improvement with dual-source radiofrequency (RF) transmission in cardiac steady-state free precession sequences at 3.0 T. Imaging with and without dual-source RF transmission was performed in 30 patients. Contrast-to-noise ratio for the left ventricular myocardium was significantly higher using dual-source RF transmission, but improvement was not uniformly distributed. The posterior myocardium showed significantly less contrast-to-noise ratio gain than all other cardiac regions. Signal-to-noise ratio increase was higher in the right than in the left ventricle. Subjective image quality was significantly enhanced by parallel RF transmission.

Characteristics of trabeculated myocardium burden in young and apparently healthy adults

Increased myocardial trabeculations define noncompaction cardiomyopathy (NCC). Imaging advancements have led to increasingly common identification of prominent trabeculations with unknown implications. We quantified and determined the impact of trabeculations' burden on cardiac function and stretch in a population of healthy young adults. One hundred adults aged 18 to 35 years (28±4 years, 55% women) without known cardiovascular disease were prospectively studied by cardiovascular magnetic resonance. Left ventricular (LV) volumes, segmental function, and ejection fraction (EF) and left atrial volumes were determined. Thickness and area of trabeculated (T) and dense (D) myocardium were measured for each standardized LV segment. N-terminal pro-brain natriuretic peptide (Nt-pro-BNP) was measured. Eighteen percent of the subjects had ≥1 positive traditional criteria for NCC, and 11% meet new proposed NCC cardiovascular magnetic resonance criteria. Trabeculated over dense myocardium ratio (T/D) ratios were uniformly greater at end-diastole versus end-systole (0.90±0.25 vs 0.42±0.13, p<0.0001), in women versus men (0.85±0.24 vs 0.72±0.19, p=0.006), at anterior versus nonanterior segments (1.41±0.59 vs 0.88±0.35, p<0.0001), and at apical versus nonapical segments (1.31±0.56 vs 0.87±0.38, p<0.0001). The largest T/D ratios were associated with lower LVEF (57.0±5.3 vs 62±5.5, p=0.0001) and greater Nt-pro-BNP (203±98 vs 155±103, p=0.04). Multivariable regression identified greater end-systolic T/D ratios as the strongest independent predictor of lower LVEF, beyond age and gender, left atrial or LV volumes, and Nt-pro-BNP (β=-9.9, 95% CI -15 to 4.9, p<0.001). In conclusion, healthy adults possess variable amounts of trabeculations that regularly meet criteria for NCC. Greater trabeculations are associated with decreased LV function. Apparently healthy young adults with increased trabecular burden possess evidence of mildly impaired cardiac function.

Imaging of the right heart--CT and CMR

Right ventricular (RV) structure and function is of substantial importance in a broad variety of clinical conditions. Cardiac magnetic resonance (CMR) and computed tomography (CT) each provide three-dimensional RV imaging, high-resolution evaluation of RV structure/anatomy, and accurate functional assessment without geometric assumptions. This is of particular significance for the RV, where complex geometry compromises reliance on indices derived from two-dimensional (2D) imaging planes. CMR flow-based imaging can be applied to right-sided heart valves, enabling evaluation of hemodynamic and valvular dysfunction that may contribute to or result from RV dysfunction. Tissue characterization imaging by both CMR and CT provides valuable complementary assessment of the RV. Changes in myocardial tissue composition provide a mechanistic substrate for RV dysfunction and cardiac arrhythmias. This review provides an overview of RV imaging by both CMR and CT, with focus on assessment of RV structure/function, flow, and tissue characterization. Emerging evidence and established guidelines are discussed in the context of imaging contributions to diagnosis, prognostic risk stratification and disease management of clinical conditions that impact the right ventricle.

Tools for cardiovascular magnetic resonance imaging

In less than fifteen years, as a non-invasive imaging option, cardiovascular MR has grown from a being a mere curiosity to becoming a widely used clinical tool for evaluating cardiovascular disease. Cardiovascular magnetic resonance imaging (CMRI) is now routinely used to study myocardial structure, cardiac function, macro vascular blood flow, myocardial perfusion, and myocardial viability. For someone entering the field of cardiac MR, this rapid pace of development in the field of CMRI might make it difficult to identify a cohesive starting point. In this brief review, we have attempted to summarize the key cardiovascular imaging techniques that have found widespread clinical acceptance. In particular, we describe the essential cardiac and respiratory gating techniques that form the backbone of all cardiovascular imaging methods. It is followed by four sections that discuss: (I) the gradient echo techniques that are used to assess ventricular function; (II) black-blood turbo spin echo (SE) methods used for morphologic assessment of the heart; (III) phase-contrast based techniques for the assessment of blood flow; and (IV) CMR methods for the assessment of myocardial ischemia and viability. In each section, we briefly summarize technical considerations relevant to the clinical use of these techniques, followed by practical information for its clinical implementation. In each of those four areas, CMRI is considered either as the benchmark imaging modality against which the diagnostic performance of other imaging modalities are compared against, or provides a complementary capability to existing imaging techniques. We have deliberately avoided including cutting-edge CMR imaging techniques practiced at few academic centers, and restricted our discussion to methods that are widely used and are likely to be available in a clinical setting. Our hope is that this review would propel an interested reader toward more comprehensive reviews in the literature.

Application of single shot free-breathing fast imaging employing steady state sequence in cardiac magnetic resonance imaging

OBJECTIVE

To investigate the imaging quality of single shot (SS) fast imaging employing steady state (FIESTA) sequence in contrast-enhanced cardiac magnetic resonance (MR) examination, in comparison with the segmented inversion recovery 2D fast gradient echo (IR FGRE) sequence.

MATERIALS AND METHODS

Fifty-two cases with suspected or known heart disease were enrolled in this study, including 24 patients who had enhanced myocardium in myocardial delayed enhancement (MDE). We analyzed the imaging quality of the sequences by measuring the myocardium and blood pool signal-to-noise ratios (SNR) and the contrast-to-noise ratios (CNR) of blood pool relative to normal myocardium and of enhanced myocardium relative to normal myocardium and compared the new sequences with traditional sequence.

RESULTS

The scanning time of SS FIESTA was significantly shortened as compared to IR FGRE. The differences in the image quality scores, enhanced myocardium (EM) mass and percentages, SNR(bp), SNR(myo), CNR(myo/bp) and CNR(l/bg) were not statistically significant between SS FIESTA and IR FGRE (P > 0.05). However, the difference in CNR(em/myo) was statistically significant between SS FIESTA and IR FGRE (P < 0.0001), with CNR(em/myo) of IR FGRE higher than SS FIESTA.

CONCLUSION

Single shot FIESTA speeded up the acquisition time, halving it to (27.6 ± 1.8 s) instead of 146 + 13.8 s (IR FGRE), it had higher SNR and CNR, and its image quality did not differ significantly from IR FGRE. The SS FIESTA is more suitable for patients with severely heart diseases or those unable to hold breath. 3D IR FGRE sequence had higher SNR(myo) than the others and it is suitable for displaying the subendocardial scar. However, it has more artefacts and poor imaging quality than IR FGRE.

MR imaging of cardiac tumors and masses: a review of methods and clinical applications

Cardiac masses are usually first detected at echocardiography. In their further evaluation, cardiac magnetic resonance (MR) imaging has become a highly valuable technique. MR imaging offers incremental value owing to its larger field of view, superior tissue contrast, versatility in image planes, and unique ability to enable discrimination of different tissue characteristics, such as water and fat content, which give rise to particular signal patterns with T1- and T2-weighted techniques. With contrast material-enhanced MR imaging, additional tissue properties such as vascularity and fibrosis can be demonstrated. MR imaging can therefore contribute to the diagnosis of a cardiac mass as well as be used to detail its relationship to other cardiac and extracardiac structures. These assessments are important to plan therapy, such as surgical intervention. In addition, serial MR studies can be used to monitor tumor regression after surgery or chemotherapy. Primary cardiac tumors are very rare; metastases and pseudotumors (eg, thrombus) are much more common. This article provides an overview of cardiac masses and reviews the optimal MR imaging techniques for their assessment.

Assessment of cardiac volumes using an isotropic whole-heart dual cardiac phase sequence in pediatric patients

PURPOSE

To evaluate the accuracy of a three-dimensional dual phase (3D DP) whole-heart technique for cardiac volumetric assessment in pediatric patients with cardiac abnormalities.

MATERIALS AND METHODS

The institutional approved this study, and informed consent was obtained from patients or their guardians. This prospective study involved 31 pediatric patients (mean age, 7.9 years; range, 15 days to 15 years) for the assessment of cardiac abnormalities using cardiovascular MR. A standard protocol was performed for assessing cardiac anatomy and function. For evaluating the 3D DP technique, statistical comparison with a 2D cine multi-slice technique (2D steady-state free-precession [SSFP]) was performed using linear regression, intraclass correlation coefficient, and Bland Altman plots.

RESULTS

Left (LV) and right (RV) ventricular cardiac volumes obtained with the 3D DP technique were in strong agreement with those obtained with the 2D SSFP technique for small and large ventricular volumes. The intraclass correlation coefficients (ICC) between both techniques were 0.992 for the LV end-diastolic volume (EDV), 0.983 for the LV end-systolic volume (ESV), 0.952 for the LV-systolic volume (SV), 0.992 for the RV-EDV, 0.992 for the RV-ESV, 0.928 for the RV-SV. Interobserver analysis indicated good reproducibility for both the 2D SSFP and the 3D DP techniques.

CONCLUSION

The 3D DP technique provides as accurate cardiac volumes as the 2D SSFP technique in the pediatric population, but with the added benefits of easier data acquisition and detailed anatomical information of the whole heart and great vessels in a single free-breathing scan.

Cardiovascular magnetic resonance artefacts

The multitude of applications offered by CMR make it an increasing popular modality to study the heart and the surrounding vessels. Nevertheless the anatomical complexity of the chest, together with cardiac and respiratory motion, and the fast flowing blood, present many challenges which can possibly translate into imaging artefacts. The literature is wide in terms of papers describing specific MR artefacts in great technical detail. In this review we attempt to summarise, in a language accessible to a clinical readership, some of the most common artefacts found in CMR applications. It begins with an introduction of the most common pulse sequences, and imaging techniques, followed by a brief section on typical cardiovascular applications. This leads to the main section on common CMR artefacts with examples, a short description of the mechanisms behind them, and possible solutions.

Left ventricular stroke volume quantification by contrast echocardiography - comparison of linear and flow-based methods to cardiac magnetic resonance

BACKGROUND

Echocardiography (echo)-quantified LV stroke volume (SV) is widely used to assess systolic performance after acute myocardial infarction (AMI). This study compared 2 common echo approaches - predicated on flow (Doppler) and linear chamber dimensions (Teichholz) - to volumetric SV and global infarct parameters quantified by cardiac magnetic resonance (CMR).

METHODS

Multimodality imaging was performed as part of a post-AMI registry. For echo, SV was measured by Doppler and Teichholz methods. Cine-CMR was used for volumetric SV and LVEF quantification, and delayed-enhancement (DE) CMR for infarct size.

RESULTS

Overall, 142 patients underwent same day echo and CMR. On echo, mean SV by Teichholz (78 ± 17 mL) was slightly higher than Doppler (75 ± 16 mL; Δ = 3 ± 13 mL; P = 0.02). Compared to SV on CMR (78 ± 18 mL), mean difference by Teichholz (Δ = -0.2 ± 14; P = 0.89) was slightly smaller than Doppler (Δ = -3 ± 14; P = 0.02), but limits of agreement were similar between CMR and echo methods (Teichholz: -28, 27 mL, Doppler: -31, 24 mL). For Teichholz, differences with CMR SV were greatest among patients with anteroseptal or lateral wall hypokinesis (P < 0.05). For Doppler, differences were associated with aortic valve abnormalities or root dilation (P = 0.01). SV by both echo methods decreased stepwise in relation to global LV injury as assessed by CMR-quantified LVEF and infarct size (P < 0.01).

CONCLUSIONS

Teichholz and Doppler calculated SV yield similar magnitude of agreement with CMR. Teichholz differences with CMR increase with septal or lateral wall contractile dysfunction, whereas Doppler yields increased offsets in patients with aortic remodeling.

Impact of the Advisa MRI pacing system on the diagnostic quality of cardiac MR images and contraction patterns of cardiac muscle during scans: Advisa MRI randomized clinical multicenter study results

BACKGROUND

The Advisa MRI system is designed to safely undergo magnetic resonance imaging (MRI). Its influence on image quality is not well known.

OBJECTIVE

To evaluate cardiac magnetic resonance (CMR) image quality and to characterize myocardial contraction patterns by using the Advisa MRI system.

METHODS

In this international trial with 35 participating centers, an Advisa MRI system was implanted in 263 patients. Of those, 177 were randomized to the MRI group and 150 underwent MRI scans at the 9-12-week visit. Left ventricular (LV) and right ventricular (RV) cine long-axis steady-state free precession MR images were graded for quality. Signal loss along the implantable pulse generator and leads was measured. The tagging CMR data quality was assessed as the percentage of trackable tagging points on complementary spatial modulation of magnetization acquisitions (n=16) and segmental circumferential fiber shortening was quantified.

RESULTS

Of all cine long-axis steady-state free precession acquisitions, 95% of LV and 98% of RV acquisitions were of diagnostic quality, with 84% and 93%, respectively, being of good or excellent quality. Tagging points were trackable from systole into early diastole (360-648 ms after the R-wave) in all segments. During RV pacing, tagging demonstrated a dyssynchronous contraction pattern, which was not observed in nonpaced (n = 4) and right atrial-paced (n = 8) patients.

CONCLUSIONS

In the Advisa MRI study, high-quality CMR images for the assessment of cardiac anatomy and function were obtained in most patients with an implantable pacing system. In addition, this study demonstrated the feasibility of acquiring tagging data to study the LV function during pacing.

Dynamic imaging of the fetal heart using metric optimized gating

PURPOSE

Advances in fetal cardiovascular magnetic resonance imaging have been limited by the absence of a reliable cardiac gating signal. The purpose of this work was to develop and validate metric-optimized gating (MOG) for cine imaging of the fetal heart.

THEORY AND METHODS

Cine MR and electrocardiogram data were acquired in healthy adult volunteers for validation of the MOG method. Comparison of MOG and electrocardiogram reconstructions was performed based on the image quality for each method, and the difference between MOG and electrocardiogram trigger times. Fetal images were also acquired, their quality evaluated by experienced radiologists, and the theoretical error in the MOG trigger times were calculated.

RESULTS

Excellent agreement between electrocardiogram and MOG reconstructions was observed. The experimental errors in adult MOG trigger times for all five volunteers were ± (7, 25, 17, 8, and 13) ms. Fetal images captured normal and diseased cardiac dynamics.

CONCLUSION

MOG for cine imaging of the fetal myocardium was developed and validated in adults. Using MOG, the first gated MR images of the human fetal myocardium were obtained. Small moving structures were visualized during radial contraction, thus capturing normal fetal cardiac wall motion and permitting assessment of cardiac function.

Evaluation of cardiac function by magnetic resonance imaging during the follow-up of patients with Kawasaki disease

BACKGROUND

Although histopathologic studies suggest persistent myocardial abnormalities after Kawasaki disease (KD), the long-term effects on cardiac function remain to be revealed. We investigated biventricular volumes, function, and the presence of myocardial fibrosis by cardiac magnetic resonance imaging during long-term follow-up of KD.

METHODS AND RESULTS

Sixty patients with a history of KD (mean age, 16.9 years; 67% men; median interval after KD onset, 11.6 years) and 20 healthy control subjects (mean age, 17.9 years; 55% men) 12 to 24 years of age underwent cardiac magnetic resonance imaging. Biventricular end-diastolic volume, end-systolic volume, stroke volume, and ejection fraction were determined. Volumetric measurements were indexed for body surface area. Late contrast enhancement was used to detect areas of myocardial fibrosis. Biventricular volumes and function did not differ significantly between patients and control subjects. There were also no significant differences between patients with and without a history of left ventricular dysfunction resulting from KD-associated myocarditis or between patients with and without coronary artery aneurysms. Only those with prior ischemic heart disease had a significantly lower left ventricular ejection fraction compared with unaffected KD cases (left ventricular ejection fraction, 51% versus 57%; P=0.012). Late contrast enhancement was observed in only 2 patients with severe coronary artery aneurysms and was typical for myocardial infarction.

CONCLUSIONS

In this cardiac magnetic resonance imaging study evaluating the cardiac function of patients with KD at long-term follow-up, we did not observe a difference in cardiac function between KD patients and control subjects, except for a subgroup of patients with ischemic heart disease as a result of severe coronary artery pathology.

MRI of acute vascular syndromes: the emerging role of cardiovascular MRI in the diagnosis and treatment of AMI and stroke

MRI is a safe and reproducible noninvasive method of obtaining high-resolution images of the heart and vascular system. As MRI has developed a more widespread clinical application over the last decade, attention has been increasing on how this technique can be used to aid the diagnosis of cardio- and cerebro-vascular diseases in the acute setting. While much of the initial development of cardiac MRI was based around describing the myocardium in the chronic stable state, much recent research has investigated the use of MRI to assess acute coronary syndromes. Similarly, arterial wall imaging using MRI was initially confined to relatively stable research populations; however, more recent work has suggested a possible future clinical role for vascular MRI techniques in acute settings. This study highlights recent advances in MRI of the cardiovascular system, with a particular emphasis on those techniques that can be of use in the setting of acute vascular syndromes, namely acute coronary syndrome, transient ischemic attack and stroke.