Breath-hold FLASH and FISP cardiovascular MR imaging: left ventricular volume differences and reproducibility

From Compressed-Sensing to Deep Learning MR: Comparative Biventricular Cardiac Function Analysis in a Patient Cohort

BACKGROUND

Conventional segmented, retrospectively gated cine (Conv-cine) is challenged in patients with breath-hold difficulties. Compressed sensing (CS) has shown values in cine imaging but generally requires long reconstruction time. Recent artificial intelligence (AI) has demonstrated potential in fast cine imaging.

PURPOSE

To compare CS-cine and AI-cine with Conv-cine in quantitative biventricular functions, image quality, and reconstruction time.

STUDY TYPE

Prospective human studies.

SUBJECTS

70 patients (age, 39 ± 15 years, 54.3% male).

FIELD STRENGTH/SEQUENCE

3T; balanced steady state free precession gradient echo sequences.

ASSESSMENT

Biventricular functional parameters of CS-, AI-, and Conv-cine were measured by two radiologists independently and compared. The scan and reconstruction time were recorded. Subjective scores of image quality were compared by three radiologists.

STATISTICAL TESTS

Paired t-test and two related-samples Wilcoxon sign test were used to compare biventricular functional parameters between CS-, AI-, and Conv-cine. Intraclass correlation coefficient (ICC), Bland-Altman analysis, and Kendall's W method were applied to evaluate agreement of biventricular functional parameters and image quality of these three sequences. A P-value <0.05 was considered statistically significant, and standardized mean difference (SMD) < 0. 100 was considered no significant difference.

RESULTS

Compared to Conv-cine, no statistically significant differences were identified in CS- and AI-cine function results (all P > 0.05), except for very small differences in left ventricle end-diastole volumes of 2.5 mL (SMD = 0.082) and 4.1 mL (SMD = 0.096), respectively. Bland-Altman scatter plots revealed that biventricular function results were mostly distributed within the 95% confidence interval. All parameters had acceptable to excellent interobserver agreements (ICC: 0.748-0.989). Compared with Conv-cine (84 ± 13 sec), both CS (14 ± 2 sec) and AI (15 ± 2 sec) techniques reduced scan time. Compared with CS-cine (304 ± 17 sec), AI-cine (24 ± 4 sec) reduced reconstruction time. CS-cine demonstrated significantly lower quality scores than Conv-cine, while AI-cine demonstrated similar scores (P = 0.634).

CONCLUSION

CS- and AI-cine can achieve whole-heart cardiac cine imaging in a single breath-hold. Both CS- and AI-cine have the potential to supplement the gold standard Conv-cine in studying biventricular functions and benefit patients having difficulties with breath-holds.

LEVEL OF EVIDENCE

1 TECHNICAL EFFICACY STAGE: 1.

Evaluation of left ventricular and left atrial volumetric function from native MR multislice 4D flow magnitude data

OBJECTIVES

To assess the feasibility, precision, and accuracy of left ventricular (LV) and left atrial (LA) volumetric function evaluation from native magnetic resonance (MR) multislice 4D flow magnitude images.

MATERIALS & METHODS

In this prospective study, 60 subjects without signs or symptoms of heart failure underwent 3T native cardiac MR multislice 4D flow and bSSFP-cine realtime imaging. LV and LA volumetric function parameters were evaluated from 4D flow magnitude (4D flow-cine) and bSSFP-cine data using standard software to obtain end-diastolic volume (EDV), end-systolic volume (ESV), ejection-fraction (EF), stroke-volume (SV), LV muscle mass (LVM), LA maximum volume, LA minimum volume, and LA total ejection fraction (LATEF). Stroke volumes derived from both imaging methods were further compared to 4D pulmonary artery flow-derived net forward volumes (NFV). Methods were compared by correlation and Bland-Altman analysis.

RESULTS

Volumetric function parameters from 4D flow-cine and bSSFP-cine showed high to very high correlations (r = 0.83-0.98). SV, LA volumes and LATEF did not differ between methods. LV end-diastolic and end-systolic volumes were slightly underestimated (EDV: -2.9 ± 5.8 mL; ESV: -2.3 ± 3.8 mL), EF was slightly overestimated (EF: 0.9 ± 2.6%), and LV mass was considerably overestimated (LVM: 39.0 ± 11.4 g) by 4D flow-cine imaging. SVs from both methods correlated very highly with NFV (r = 0.91 in both cases) and did not differ from NFV.

CONCLUSION

Native multislice 4D flow magnitude data allows precise evaluation of LV and LA volumetric parameters; however, apart from SV, LV volumetric parameters demonstrate bias and need to be referred to their respective normal values.

CLINICAL RELEVANCE STATEMENT

Volumetric function assessment from native multislice 4D flow magnitude images can be performed with routinely used clinical software, facilitating the application of 4D flow as a one-stop-shop functional cardiac MR exam, providing consistent, simultaneously acquired, volume and flow data.

KEY POINTS

• Native multislice 4D flow imaging allows evaluation of volumetric left ventricular and atrial function parameters. • Left ventricular and left atrial function parameters derived from native multislice 4D flow data correlate highly with corresponding standard cine-derived parameters. • Multislice 4D flow-derived volumetric stroke volume and net forward volume do not differ.

Towards automatic classification of cardiovascular magnetic resonance Task Force Criteria for diagnosis of arrhythmogenic right ventricular cardiomyopathy

BACKGROUND

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is diagnosed according to the Task Force Criteria (TFC) in which cardiovascular magnetic resonance (CMR) imaging plays an important role. Our study aims to apply an automatic deep learning-based segmentation for right and left ventricular CMR assessment and evaluate this approach for classification of the CMR TFC.

METHODS

We included 227 subjects suspected of ARVC who underwent CMR. Subjects were classified into (1) ARVC patients fulfilling TFC; (2) at-risk family members; and (3) controls. To perform automatic segmentation, a Bayesian Dilated Residual Neural Network was trained and tested. Performance of automatic versus manual segmentation was assessed using Dice-coefficient and Hausdorff distance. Since automatic segmentation is most challenging in basal slices, manual correction of the automatic segmentation in the most basal slice was simulated (automatic^-basal). CMR TFC calculated using manual and automatic^-basal segmentation were compared using Cohen's Kappa (κ).

RESULTS

Automatic segmentation was trained on CMRs of 70 subjects (39.6 ± 18.1 years, 47% female) and tested on 157 subjects (36.9 ± 17.6 years, 59% female). Dice-coefficient and Hausdorff distance showed good agreement between manual and automatic segmentations (≥ 0.89 and ≤ 10.6 mm, respectively) which further improved after simulated correction of the most basal slice (≥ 0.92 and ≤ 9.2 mm, p < 0.001). Pearson correlation of volumetric and functional CMR measurements was good to excellent (automatic (r = 0.78-0.99, p < 0.001) and automatic^-basal (r = 0.88-0.99, p < 0.001) measurements). CMR TFC classification using automatic^-basal segmentations was comparable to manual segmentations (κ 0.98 ± 0.02) with comparable diagnostic performance.

CONCLUSIONS

Combining automatic segmentation of CMRs with correction of the most basal slice results in accurate CMR TFC classification of subjects suspected of ARVC.

Free-breathing cardiovascular cine magnetic resonance imaging using compressed-sensing and retrospective motion correction: accurate assessment of biventricular volume at 3T

PURPOSE

We applied a combination of compressed-sensing (CS) and retrospective motion correction to free-breathing cine magnetic resonance (MR) (FBCS cine MoCo). We validated FBCS cine MoCo by comparing it with breath-hold (BH) conventional cine MR.

MATERIALS AND METHODS

Thirty-five volunteers underwent both FBCS cine MoCo and BH conventional cine MR imaging. Twelve consecutive short-axis cine images were obtained. We compared the examination time, image quality and biventricular volumetric assessments between the two cine MR.

RESULTS

FBCS cine MoCo required a significantly shorter examination time than BH conventional cine (135 s [110-143 s] vs. 198 s [186-349 s], p < 0.001). The image quality scores were not significantly different between the two techniques (End-diastole: FBCS cine MoCo; 4.7 ± 0.5 vs. BH conventional cine; 4.6 ± 0.6; p = 0.77, End-systole: FBCS cine MoCo; 4.5 ± 0.5 vs. BH conventional cine; 4.5 ± 0.6; p = 0.52). No significant differences were observed in all biventricular volumetric assessments between the two techniques. The mean differences with 95% confidence interval (CI), based on Bland-Altman analysis, were - 0.3 mL (- 8.2 - 7.5 mL) for LVEDV, 0.2 mL (- 5.6 - 5.9 mL) for LVESV, - 0.5 mL (- 6.3 - 5.2 mL) for LVSV, - 0.3% (- 3.5 - 3.0%) for LVEF, - 0.1 g (- 8.5 - 8.3 g) for LVED mass, 1.4 mL (- 15.5 - 18.3 mL) for RVEDV, 2.1 mL (- 11.2 - 15.3 mL) for RVESV, - 0.6 mL (- 9.7 - 8.4 mL) for RVSV, - 1.0% (- 6.5 - 4.6%) for RVEF.

CONCLUSION

FBCS cine MoCo can potentially replace multiple BH conventional cine MR and improve the clinical utility of cine MR.

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.

Comparative assessment of motion averaged free-breathing or breath-held cardiac magnetic resonance imaging protocols in a porcine myocardial infarction model

Breath-held (BH) cardiac magnetic resonance imaging (CMR) is the gold standard for volumetric quantification. However, large animals for pre-clinical research are unable to voluntarily breath-hold, necessitating general anaesthesia and mechanical ventilation, increasing research costs and affecting cardiovascular physiology. Conducting CMR in lightly sedated, free-breathing (FB) animal subjects is an alternative strategy which can overcome these constraints, however, may result in poorer image quality due to breathing motion artefact. We sought to assess the reproducibility of CMR metrics between FB and BH CMR in a porcine model of ischaemic cardiomyopathy. FB or BH CMR was performed in 38 porcine subjects following percutaneous induction of myocardial infarction. Analysis was performed by two independent, blinded observers according to standard reporting guidelines. Subjective and objective image quality was significantly improved in the BH cohort (image quality score: 3.9/5 vs. 2.4/5; p < 0.0001 and myocardium:blood pool intensity ratio: 2.6-3.3 vs. 1.9-2.3; p < 0.001), along with scan acquisition time (4 min 06 s ± 1 min 55 s vs. 8 min 53 s ± 2 min 39 s; p < 0.000). Intra- and inter-observer reproducibility of volumetric analysis was substantially improved in BH scans (correlation coefficients: 0.94-0.99 vs. 0.76-0.91; coefficients of variation: < 5% in BH and > 5% in FB; Bland-Altman limits of agreement: < 10 in BH and > 10 in FB). Interstudy variation between approaches was used to calculate sample sizes, with BH CMR resulting in greater than 85% reduction in animal numbers required to show clinically significant treatment effects. In summary, BH porcine CMR produces superior image quality, shorter scan acquisition, greater reproducibility, and requires smaller sample sizes for pre-clinical trials as compared to FB acquisition.

Feasibility of Cardiac Computed Tomography for the Evaluation of Ventricular Function in Postoperative Children With Congenital Heart Disease: Comparison With Cardiac Magnetic Resonance Imaging

OBJECTIVE

We explored the feasibility of cardiac computed tomography (CCT) to evaluate postoperative ventricular function in children with congenital heart disease (CHD) and evaluated the accuracy and reproducibility of CCT using cardiac magnetic resonance (CMR) as a reference.

METHODS

Thirty-two postoperative children with CHD (20 boys and 12 girls) who underwent CMR and CCT were enrolled. Left and right ventricular ejection fraction, end-diastolic volume, end-systolic volume, stroke volume, and cardiac index were measured using cardiac function analysis software. Cardiac function data were compared between CMR and CCT. The agreement between the 2 modalities was assessed using a Bland-Altman analysis. Intraclass correlation coefficients were used to assess intraobserver and interobserver reproducibility in CCT functional measurements.

RESULTS

All functional parameters showed no significant difference (P > 0.05) and were well-correlated (r > 0.5, P < 0.05) between CMR and CCT. The mean values of all ventricular function parameters in CCT were higher compared with CMR. As indicated by 95% limits of agreement, left ventricular function parameters showed a better level of agreement compared with right ventricular function parameters between the 2 modalities. Intraobserver and interobserver reproducibility were excellent in CCT measurements for all functional parameters (intraclass correlation coefficient > 0.9).

CONCLUSIONS

Compared with the criterion standard of CMR, CCT is feasible for assessing postoperative ventricular function with sufficient diagnostic accuracy and reproducibility in children with CHD. In addition to its important role regarding anatomical characterization, CCT is a suitable alternative and convenient follow-up tool that can be used to functional evaluation in children who are intolerant with CMR or have contraindications to CMR.

Comparison of the early cardiac electromechanical remodeling following transcatheter and surgical secundum atrial septal defect closure in adults

Background

Secundum atrial septal defect (ASD) closure leads to electrical and mechanical remodeling that occurs early after shunt disappearance. The relationship between electromechanical remodeling using electrocardiogram (ECG) and cardiac magnetic resonance (CMR) after percutaneous and surgical closure has not yet been recorded in prospective studies.

Objective

We thought to study right atrium (RA) and right ventricle (RV) changes by CMR 3 months after transcatheter and surgical closure and their comparison with electrical remodeling by ECG.

Results

We prospectively evaluated 30 consecutive adult patients with isolated secundum ASD who were referred for (transcatheter and surgical) ASD closure.

There was significant reduction in all of the electrical parameters within the same group as compared to the baseline values, except P wave dispersion (Pd). (P max was 97.33 ± 16.67 (pre closure) to 76 ± 15.49 (post closure) in the device group and 97.33 ± 12.79 (preclosure) to 73.33 ± 16.32 (post closure) in the surgical group, QRS complex was 104 ± 18.82 (preclosure) to 80 ± 18.51 (post closure) in the device group and 106.67 ± 14.47 (preclosure) to 86.67 ± 17.99 (post closure) in the surgical group. QTc maximum was 478.53 ± 36.79 (preclosure) to 412.53 ± 38.03 (post closure) in the device group and 470.53 ± 65.70 (preclosure) to 405.93 ± 63.08 (post closure) in the surgical group, and QTc dispersion was 70.33 ± 24.04 (preclosure) to 60.26 ± 28.56 (post closure) in the device group and 80.73 ± 30.38 (preclosure) to 60.27 ± 28.57 (post closure) in the surgical group).There was no significant difference between two groups indicating that transcatheter and surgical closure had led to equivalent value of electrical remodeling.

In CMR study, we measured RA maximal volume and right ventricle end diastolic volume (RVEDV), RA maximal volume decreased significantly as compared to the base line values post closure in both groups (P value < 0.001). The reduction in RA max volume was more in the transcatheter closure group; however, this difference was not statistically significant when compared with the surgical arm (P value = 0.5).RVEDV decreased significantly in both groups as compared to the baseline values (P value < 0.001). Transcatheter closure resulted in more significant reduction in the RVEDV than the surgical closure (P value = 0.03).

Conclusion

Our study showed early significant electromechanical reverse remodeling in most of the study parameters from the baseline values after ASD closure. We found no significant differences in all of the electrical and RA mechanical remodeling parameters with significantly better mechanical remodeling of RV in the device group.

Comparison of cine and real-time cardiac MRI in rhesus macaques

Cardiac MRI in rhesus macaques, a species of major relevance for preclinical studies on biological therapies, requires artificial ventilation to realize breath holding. To overcome this limitation of standard cine MRI, the feasibility of Real-Time (RT) cardiac MRI has been tested in a cohort of ten adult rhesus macaques using a clinical MR-system. In spite of lower tissue contrast and sharpness of RT-MRI, cardiac functions were similarly well assessed by RT-MRI compared to cine MRI (similar intra-subject repeatability). However, systematic underestimation of the end-diastolic volume (31 ± 9%), end-systolic volume (20 ± 11%), stroke volume (40 ± 12%) and ejection fraction (13 ± 9%) hamper the comparability of RT-MRI results with those of other cardiac MRI methods. Yet, the underestimations were very consistent (< 5% variability) for repetitive measurements, making RT-MRI an appropriate alternative to cine MRI for longitudinal studies. In addition, RT-MRI enabled the analysis of cardio-respiratory coupling. All functional parameters showed lower values during expiration compared to inspiration, most likely due to the pressure-controlled artificial ventilation. In conclusion, despite systematic underestimation of the functional parameters, RT-MRI allowed the assessment of left ventricular function in macaques with significantly less experimental effort, measurement time, risk and burden for the animals compared to cine MRI.

Deep learning-based cardiac cine segmentation: Transfer learning application to 7T ultrahigh-field MRI

PURPOSE

Artificial neural networks show promising performance in automatic segmentation of cardiac MRI. However, training requires large amounts of annotated data and generalization to different vendors, field strengths, sequence parameters, and pathologies is limited. Transfer learning addresses this challenge, but specific recommendations regarding type and amount of data required is lacking. In this study, we assess data requirements for transfer learning to experimental cardiac MRI at 7T where the segmentation task can be challenging. In addition, we provide guidelines, tools, and annotated data to enable transfer learning approaches by other researchers and clinicians.

METHODS

A publicly available segmentation model was used to annotate a publicly available data set. This labeled data set was subsequently used to train a neural network for segmentation of left ventricle and myocardium in cardiac cine MRI. The network is used as starting point for transfer learning to 7T cine data of healthy volunteers (n = 22; 7873 images) by updating the pre-trained weights. Structured and random data subsets of different sizes were used to systematically assess data requirements for successful transfer learning.

RESULTS

Inconsistencies in the publically available data set were corrected, labels created, and a neural network trained. On 7T cardiac cine images the model pre-trained on public imaging data, acquired at 1.5T and 3T, achieved DICE_LV = 0.835 and DICE_MY = 0.670. Transfer learning using 7T cine data and ImageNet weight initialization improved model performance to DICE_LV = 0.900 and DICE_MY = 0.791. Using only end-systolic and end-diastolic images reduced training data by 90%, with no negative impact on segmentation performance (DICE_LV = 0.908, DICE_MY = 0.805).

CONCLUSIONS

This work demonstrates and quantifies the benefits of transfer learning for cardiac cine image segmentation. We provide practical guidelines for researchers planning transfer learning projects in cardiac MRI and make data, models, and code publicly available.

Exaggerated Cardiac Contractile Response to Hypoxia in Adults Born Preterm

Individuals born prematurely have smaller hearts, cardiac limitations to exercise, and increased overall cardiometabolic risk. The cardiac effects of acute hypoxia exposure as another physiologic stressor remain under explored. The purpose of this study was to determine the effects of hypoxia on ventricular function in adults born preterm. Adults born moderately to extremely preterm (≤32 weeks gestation or <1500 g, N = 32) and born at term (N = 18) underwent cardiac magnetic resonance imaging under normoxic (21% O₂) and hypoxic (12% O₂) conditions to assess cardiovascular function. In normoxia, cardiac function parameters were similar between groups. During hypoxia, the right ventricular (RV) contractile response was significantly greater in participants born premature, demonstrated by greater increases in RV ejection fraction (EF) (p = 0.002), ventricular-vascular coupling (VVC) (p = 0.004), and strain (p < 0.0001) measures compared to term-born participants, respectively. Left ventricular contractile reserve was similar to term-born participants. Adults born preterm exhibit an exaggerated contractile response to acute hypoxia, particularly in the RV. This suggests that adults born preterm may have contractile reserve, despite the lack of volume reserve identified in previous exercise studies. However, this exaggerated and hyper-adapted response may also increase their risk for late RV failure.

Comparison between conventional and compressed sensing cine cardiovascular magnetic resonance for feature tracking global circumferential strain assessment

BACKGROUND

Feature tracking (FT) has become an established tool for cardiovascular magnetic resonance (CMR)-based strain analysis. Recently, the compressed sensing (CS) technique has been applied to cine CMR, which has drastically reduced its acquisition time. However, the effects of CS imaging on FT strain analysis need to be carefully studied. This study aimed to investigate the use of CS cine CMR for FT strain analysis compared to conventional cine CMR.

METHODS

Sixty-five patients with different left ventricular (LV) pathologies underwent both retrospective conventional cine CMR and prospective CS cine CMR using a prototype sequence with the comparable temporal and spatial resolution at 3 T. Eight short-axis cine images covering the entire LV were obtained and used for LV volume assessment and FT strain analysis. Prospective CS cine CMR data over 1.5 heartbeats were acquired to capture the complete end-diastolic data between the first and second heartbeats. LV volume assessment and FT strain analysis were performed using a dedicated software (ci42; Circle Cardiovasacular Imaging, Calgary, Canada), and the global circumferential strain (GCS) and GCS rate were calculated from both cine CMR sequences.

RESULTS

There were no significant differences in the GCS (- 17.1% [- 11.7, - 19.5] vs. - 16.1% [- 11.9, - 19.3; p = 0.508) and GCS rate (- 0.8 [- 0.6, - 1.0] vs. - 0.8 [- 0.7, - 1.0]; p = 0.587) obtained using conventional and CS cine CMR. The GCS obtained using both methods showed excellent agreement (y = 0.99x - 0.24; r = 0.95; p < 0.001). The Bland-Altman analysis revealed that the mean difference in the GCS between the conventional and CS cine CMR was 0.1% with limits of agreement between -2.8% and 3.0%. No significant differences were found in all LV volume assessment between both types of cine CMR.

CONCLUSION

CS cine CMR could be used for GCS assessment by CMR-FT as well as conventional cine CMR. This finding further enhances the clinical utility of high-speed CS cine CMR imaging.

The 4D B-spline method of calculating left ventricular functional parameters of cardiac MRI to evaluate myocardial injury of the apical segment in patients with myocarditis: a case-controlled observational study

Background

Myocarditis does not have typical clinical manifestations and thus is difficult to accurately diagnose by virtue of infection history, and electrocardiogram (EKG) and peripheral blood abnormalities. Endomyocardial biopsy is the gold standard for diagnosis of myocarditis, but is invasive, high risk, and has an observational blind area. Cardiac magnetic resonance imaging (CMRI) is multiparameter and multidirectional with high spatial resolution and high contrast of soft tissue. However, the optimal method of calculating left ventricular (LV) function in patients with apical-segment-injured myocarditis is unresolved. We compared and analyzed the differences between two different methods (Simpson and 4D B-spline surface model (known as the 4D method)) of measuring LV function by CMRI in patients with myocarditis in the 17th segment of the left ventricle.

Methods

The basic clinical data of two groups (myocarditis and non-myocarditis) were statistically analyzed, and differences in the LV function parameters by the two imaging methods were compared in the myocarditis group. Receiver-operating characteristic curves of single parameters and combined parameters based on the Simpson and 4D methods were drawn and the area under the curve, diagnostic threshold, maximum sensitivity interval, and maximum specificity interval were calculated.

Results

In the myocarditis and non-myocarditis groups the respective number of patients was 22 and 17, the percentage of males was 54.55% and 47.06%, and the average age was 32.20±11.59 and 43.06±11.62 years. The difference in LV ejection fraction (LVEF) (P=0.033) and LV end systolic volume (LVESV) (P=0.030) in the myocarditis group was statistically significant. The respective AUCs based on the Simpson and 4D methods were LVEF 0.602 vs. 0.778, LVESV 0.556 vs. 0.751, LVEF-and-LVESV 0.634 vs. 0.775. Based on the 4D method, the diagnostic thresholds of LVEF and LVESV were 34.965 (sensitivity 0.882, specificity 0.591) and 69.090 (sensitivity 0.727, specificity 0.706), the maximum sensitivity intervals of LVEF and LVESV were (24.610, 27.450) and (35.355, 37.200), and the maximum specificity intervals of LVEF and LVESV were (60.530, 65.625) and (91.625, 95.835), respectively.

Conclusions

Compared with the Simpson method, the 4D method might be more effective for CMRI diagnosis of apical-segment-injured myocarditis. When the Simpson method is used, LVEF combined with LVESV is recommended for comprehensive evaluation to improve diagnostic efficiency. When the 4D method is used, LVEF might be the preferred parameter for evaluation of LV function.

Cardiac Magnetic Resonance Quantification of Structure-Function Relationships in Heart Failure

Classification of heart failure is based on the left ventricular ejection fraction (EF): preserved EF, midrange EF, and reduced EF. There remains an unmet need for further heart failure phenotyping of ventricular structure-function relationships. Because of high spatiotemporal resolution, cardiac magnetic resonance (CMR) remains the reference modality for quantification of ventricular contractile function. The authors aim to highlight novel frameworks, including theranostic use of ferumoxytol, to enable more efficient evaluation of ventricular function in heart failure patients who are also frequently anemic, and to discuss emerging quantitative CMR approaches for evaluation of ventricular structure-function relationships in heart failure.

Test–retest reliability of left and right ventricular systolic function by new and conventional echocardiographic and cardiac magnetic resonance parameters

Aims 

Reproducible evaluation of left (LV) and right ventricular (RV) function is crucial for clinical decision-making and risk stratification. We evaluated whether speckle-tracking echocardiography (STE) and cardiac magnetic resonance feature-tracking (cMR-FT) global longitudinal (GLS) and circumferential strains allow better test–retest reproducibility of LV and RV systolic function than conventional cMR and echocardiographic parameters.

Methods and results 

Thirty healthy volunteers and 20 chronic heart failure patients underwent cMR and STE twice on separate days to evaluate test–retest coefficient of variation (CV), intraclass correlation coefficient (ICC) and estimated sample sizes for significant changes in LV and RV function. Among LV parameters, cMR-left ventricular ejection fraction (LVEF) had the highest reproducibility (CV = 6.7%, ICC = 0.98), significantly better than cMR-FT-GLS (CV = 15.1%, ICC = 0.84), global circumferential strains (CV = 11.5%, ICC = 0.94) and echocardiographic LVEF (CV = 11.3%, ICC = 0.93). STE-LV-GLS (CV = 8.9%, ICC = 0.94) had significantly better reproducibility than cMR-FT-LV-GLS. Among RV parameters, STE-RV-GLS (CV = 7.3%, ICC = 0.93) had significantly better CV than cMR-right ventricular ejection fraction (RVEF) (CV = 13%, ICC = 0.82). cMR-FT-RV-GLS (CV = 43%, ICC = 0.39) performed poorly with significantly lower reproducibility than all other RV parameters. Owing to their superior interstudy reproducibility, cMR-LVEF (n = 12), cMR-RVEF (n = 41), STE-LV-GLS and STE-RV-GLS (both n = 14) were the parameters allowing the lowest calculated sample sizes to detect 10% change in LV or RV systolic function.

Conclusion 

STE-LV-GLS and STE-RV-GLS showed higher test–retest reliability than other echocardiographic measurements of LV and RV function. They also allowed smaller calculated sample sizes, supporting the use of STE-LV and RV-GLS for longitudinal follow-up of LV and RV function.

Assessment of cardiac function, blood flow and myocardial tissue relaxation parameters at 0.35 T

A low field strength (B0) system could increase cardiac MRI availability for patients otherwise contraindicated at higher field. Lower equipment costs could also broaden cardiac MR accessibility. The current study investigated the feasibility of cardiac function with steady-state free precession and flow assessment with phase contrast (PC) cine images at 0.35 T, and evaluated differences in myocardial relaxation times using quantitative T1, T2 and T2* maps by comparison with 1.5 and 3 T results in a small cohort of six healthy volunteers. Signal-to-noise ratio (SNR) differences across systems were characterized with proton density-weighted spin echo phantom data. SNR at 0.35 T was lower by factors of 5.5 and 15.0 compared with the 1.5 and 3 T systems used in this study. All cine images at 0.35 T scored 3 or greater on a five-point image quality scale. Normalized blood-myocardium contrast in cine images, left ventricular volumes (end diastolic volume, end systolic volume) and function (ejection fraction and stroke volume) measures at 0.35 T matched 1.5 and 3 T results. Phase-to-noise ratio in 0.35 T PC images (11.7 ± 1.9) was lower than 1.5 T (18.7 ± 5.2) and 3 T (44.9 ± 16.5). Peak velocity and stroke volume determined from PC images were similar across systems. Myocardial T1 increased (564 ± 13 ms at 0.35 T, 955 ± 19 ms at 1.5 T and 1200 ± 35 ms at 3 T) while T2 (59 ± 4 ms at 0.35 T, 49 ± 3 ms at 1.5 T and 40 ± 2 ms at 3 T) and T2* (42 ± 8 ms at 0.35 T, 33 ± 6 ms at 1.5 T and 24 ± 3 ms at 3 T) decreased with increasing B0. Despite SNR deficits, cardiovascular function, flow assessment and myocardial relaxation parameter mapping is feasible at 0.35 T using standard cardiovascular imaging sequences.

Diagnostic efficacy of 2-shot compressed sensing cine sequence cardiovascular magnetic resonance imaging for left ventricular function

Background

Cardiac magnetic resonance cine images are conventionally acquired in breath-hold with a segmented balanced steady-state free precession (bSSFP) sequence, which requires a relatively long acquisition time and high patient cooperation. The single-shot compressed sensing (ss CS) cine sequence is a real-time sequence that has reasonable spatial and temporal resolution and can be applied during free breathing. However, the contrast between the myocardium and surrounding soft tissue is relatively reduced, and the epicardial delineation results are not as accurate with the ss CS cine sequence compared with the bSSFP sequence. In this study, we evaluated the use of a 2-shot CS cine technique in quickly acquiring high-quality images and accurately assessing cardiac function in clinical practice.

Methods

The patients enrolled in the study underwent cardiovascular magnetic resonance (CMR) on a 3T scanner from Jul. to Dec. 2018. Cine imaging was performed with 3 different methods: a standard segment cine sequence, a real-time ss CS cine sequence, and a 2-shot CS cine sequence prototype. Quantitative analysis of image quality was performed using a 0-4 scoring system, and also edge sharpness was measured, and cardiac function analysis was performed for all 3 types of cine images.

Results

Thirty-eight patients underwent imaging with the three types of cine sequences. The average scan time of the standard cine sequence was 101±20 s, the average scan time of the ss CS cine sequence was 20±4 s, and the average scan time of the 2-shot CS cine sequence was 30±6 s. The standard cine sequence image score was 3.68±0.64 and edge sharpness was (2.47±0.18) mm, the ss CS cine sequence image score was 3.13±0.35 and edge sharpness was (4.69±0.02) mm, and the 2-shot cine sequence image score was 3.54±0.51 and the edge sharpness was (2.51±0.13) mm. In terms of the quantitative study of cardiac function, the differences between the standard cine sequence and the ss CS cine sequence were not statistically significant, except for those of the imaging score and LV mass. There were no significant differences in the cardiac function parameters between the standard cine sequence and the 2-shot cine sequence. There was a strong correlation between the standard cine and ss CS cine sequences and between the standard cine and 2-shot CS cine sequences (P<0.01) of all the cardiac function parameters.

Conclusions

The 2-shot CS cine sequence can acquire images with a level of quality comparable to that of the standard cine sequence in a significantly shorter period of time. The functional parameters are similar between the 2-shot CS cine sequence and the standard cine sequence.

Variability in echocardiography and MRI for detection of cancer therapy cardiotoxicity

Objectives

To compare variability of echocardiographic and cardiovascular magnetic resonance (CMR) measured left ventricular (LV) function parameters and their relationship to cancer therapeutics-related cardiac dysfunction (CTRCD).

Methods

We prospectively recruited 60 participants (age: 49.8±11.6 years), 30 women with human epidermal growth factor receptor 2-positive breast cancer (15 with CTRCD and 15 without CTRCD) and 30 healthy volunteers. Patients were treated with anthracyclines and trastuzumab. Participants underwent three serial CMR (1.5T) and echocardiography studies at ~3-month intervals. Cine-CMR for LV ejection fraction (LVEF), myocardial tagging for global longitudinal strain (GLS) and global circumferential strain (GCS), two-dimensional (2D) echocardiography for strain and LVEF and three-dimensional (3D) echocardiography for LVEF measurements were obtained. Temporal, interobserver and intraobserver variability were calculated as the coefficient of variation and as the SE of the measurement (SEM). Minimal detected difference (MDD) was defined as 2xSEM.

Results

Patients with CTRCD demonstrated larger mean temporal changes in all parameters compared with those without: 2D-LVEF: 4.6% versus 2.8%; 3D-LVEF: 5.2% vs 2.3%; CMR-LVEF: 6.6% versus 2.7%; 2D-GLS: 1.9% versus 0.7%, 2D-GCS: 2.5% versus 2.2%; CMR-GCS: 2.7% versus 1.6%; and CMR-GLS: 2.1% versus 1.4%, with overlap in 95% CI for 2D-LVEF, 2D-GCS, CMR-GLS and CMR-GCS. The respective mean temporal variability/MDD in healthy volunteers were 3.3%/6.5%, 1.8%/3.7%, 2.2%/4.4%, 0.8%/1.5%, 1.9%/3.7%, 1.8%/3.6% and 1.4%/2.8%. Although the mean temporal variability in healthy volunteers was lower than the mean temporal changes in CTRCD, at the individual level, 2D-GLS, 3D-LVEF and CMR-LVEF had the least overlap. 2D-GLS and CMR-LVEF had the lowest interobserver/intraobserver variabilities.

Conclusion

Temporal changes in 3D-LVEF, 2D-GLS and CMR LVEF in patients with CTRCD had the least overlap with the variability in healthy volunteers; however, 2D-GLS appears to be the most suitable for clinical application in individual patients.

Measuring the link between cardiac mechanical function and metabolism during hyperpolarized 13C-pyruvate magnetic resonance experiments

PURPOSE

The goal of this study was to develop a methodology to investigate the relationship between contractile function and hyperpolarized (HP) [1-¹³C]pyruvate metabolism in a small animal model. To achieve sufficient signal from HP ¹³C compounds, HP ¹³C MRS/MRSI has required relatively large infusion volumes relative to the total blood volume in small animal models, which may affect cardiac function.

METHODS

Eight female Sprague Dawley rats were imaged on a 4.7T scanner with a dual tuned ¹H/¹³C volume coil. ECG and respiratory gated k-t spiral MRSI and an IDEAL based reconstruction to determine [1-¹³C]pyruvate metabolism in the myocardium. This was coupled with ¹H cine MRI to determine ventricular volumes and mechanical function pre- and post-infusion of [1-¹³C]pyruvate. For comparison to the [1-¹³C]pyruvate experiments, three female Sprague Dawley rats were imaged with ¹H cine MRI to determine myocardial function pre- and post-saline infusion.

RESULTS

We demonstrated significant changes in cardiac contractile function between pre- and post-infusion of [1-¹³C]pyruvate. Specifically, there was an increase in end-diastolic volume (EDV), stroke volume (SV), and ejection fraction (EF). Additionally, the ventricular vascular coupling ratio (VVCR) showed an improvement after [1-¹³C]pyruvate infusion, indicating increased systolic performance due to an increased arterial load. There was a moderate to strong relationship between the downstream metabolic conversion of pyruvate to bicarbonate and a strong relationship between the conversion of pyruvate to lactate and the cardiac mechanical function response.

CONCLUSION

The infusion of [1-¹³C]pyruvate resulted in demonstrable increases in contractile function which was related to pyruvate conversion to bicarbonate and lactate. The combined effects of the infusion volume and inotropic effects of pyruvate metabolism likely explains the augmentation in myocardial mechanical function seen in these experiments. Given the relationship between pyruvate metabolism and contractile function observed in this study, this methodological approach may be utilized to better understand cardiac metabolic and functional remodeling in heart disease.

Clinical and Advanced MRI Techniques for Detection of Checkpoint Inhibitor Associated Myocarditis

Purpose of Review

With the advent of immune checkpoint inhibitors (ICIs), cancer treatment has been revolutionized; however, these agents are associated with immune-related adverse events, including myocarditis, which ranges from mild to fulminant in severity. Currently, there are no established guidelines in diagnosing ICI-associated myocarditis, and the gold standard test for diagnosis of myocarditis in general is invasive endomyocardial biopsy (EMB). Cardiac magnetic resonance (CMR) imaging is a noninvasive test with the advantage of providing structural, functional and tissue characterization information. Additionally, it provides high spatial and temporal resolution without exposure to ionizing radiation, iodinated contrast, or radioactive isotopes.

Recent Findings

With an increasing number of reported cases of ICI associated myocarditis, understanding of the disease process and associated CMR findings is growing. Diagnostic testing with cardiac biomarkers, electrocardiogram, and echocardiogram can be nonspecific and EMB can have sampling errors. CMR as a diagnostic tool can provide functional assessment of biventricular ejection fraction, myocardial strain, tissue characterization of myocardial edema and inflammation as well as fibrosis. Furthermore, with advanced parametric mapping techniques, CMR provides even more sensitive and quantitative information about myocardial inflammation and fibrosis, including measurements of extracellular volume.

Summary

ICI-associated myocarditis is a serious immune adverse event, and CMR plays a vital role in establishing its diagnosis, providing prognostic information, and has the potential for use as a tool for screening and serial monitoring in patients exposed to ICIs.

Clinical evaluation of left ventricular function and morphology using an accelerated k-t sensitivity encoding method in cardiovascular magnetic resonance

Objectives

To provide clinical validation of a recent 2D SENSE-based accelerated cardiovascular magnetic resonance (CMR) sequence (accelerated k-t SENSE), investigating whether this technique accurately quantifies left ventricle (LV) volumes, function, and mass as compared to 2D cine steady-state free precession (2D-SSFP).

Methods

Healthy volunteers (n = 16) and consecutive heart failure patients (n = 26) were scanned using a 1.5 T MRI system. Two LV short axis (SA) stacks were acquired: (1) accelerated k-t SENSE (5–6 breath-holds; temporal/spatial resolution: 37 ms/1.82 × 1.87 mm; acceleration factor = 4) and (2) standard 2D-SSFP (10–12 breath-holds; temporal/spatial resolution: 49 ms/1.67 × 1.87 mm, parallel imaging). Ascending aorta phase-contrast was performed on all volunteers as a reference to compare LV stroke volumes (LVSV) and validate the sequences. An image quality score for SA images was used, with lower scores indicating better quality (from 0 to 18).

Results

There was a high agreement between accelerated k-t SENSE and 2D-SSFP for LV measurements: bias (limits of agreement) of 2.4% (− 5.4% to 10.1%), 6.9 mL/m² (− 4.7 to 18.6 mL/m²), − 1.5 (− 8.3 to 5.2 mL/m²), and − 0.2 g/m² (− 11.9 to 12.3 g/m²) for LV ejection fraction, end-diastolic volume index, end-systolic volume index, and mass index, respectively. LVSV by accelerated k-t SENSE presented good agreement with aortic flow. Interobserver and intraobserver variabilities for all LV parameters were also high.

Conclusion

The accelerated k-t SENSE CMR sequence is clinically feasible and accurately quantifies LV volumes, function, and mass, with short acquisition time and good image quality.

Increased Left Ventricular Trabeculation Is Associated With Increased B-Type Natriuretic Peptide Levels and Impaired Outcomes in Nonischemic Cardiomyopathy

BACKGROUND

The clinical significance of left ventricular (LV) trabeculation remains unknown in cardiomyopathies. B-Type natriuretic peptide (BNP) strongly reflects LV end-diastolic wall stress and is a useful prognostic marker of cardiovascular diseases. The enhanced identification of LV trabeculae (T) with the use of cardiac magnetic resonance and the evaluation of its relationship with BNP may elucidate the biologic significance and clinical impact of trabeculation in patients with nonischemic cardiomyopathy (NICM).

METHODS

The LV volume and mass of 515 patients with NICM and 36 control subjects were analyzed with the use of a steady-state free precession sequence, and individual T mass was planimetred. Major adverse cardiac events (MACE) were assessed.

RESULTS

T mass index correlated with LV end-diastolic volume index (EDVI), LV mass index, and papillary muscle mass index (all P < 0.001). Also, T mass index was positively correlated with BNP level (R = 0.381; P < 0.001) and was an independent determinant of BNP after adjusting for age, sex, body mass index (BMI), etiology, LV ejection fraction, and LV EDVI (P < 0.001). Kaplan-Meier analysis during a median follow-up of 17.3 months showed that higher T mass index and increased BNP level correlated with MACE. On multivariate analysis, T mass index (P = 0.031) and BNP (P < 0.001) remained associated with poor outcomes when combined with age, sex, BMI, and etiology.

CONCLUSIONS

Increased LV trabeculation was associated with LV dysfunction/remodelling and impaired outcomes in NICM of various etiologies. This may support the biologic significance of LV trabeculation and could be attributed to its association with BNP through LV wall stress.

CT compared to MRI for functional evaluation of the right ventricle: a systematic review and meta-analysis

OBJECTIVE

Right ventricular function (RVF) is a strong predictor of adverse cardiac events; however, the reference standard for RVF assessment, MRI, is limited in some patients for whom accurate evaluation of RVF is essential, like those with COPD or non-MR compatible metal implants. We conducted this meta-analysis to evaluate whether CT was as accurate as MRI for the assessment of RVF.

METHOD

We conducted a meta-analysis of studies retrieved from PubMed, Embase, and Cochrane Central searches to evaluate the differences and correlations between the following RVF parameters as measured by CT and MRI: end diastole volume (EDV), end systole volume (ESV), right ventricular ejection fraction (RVEF), and stroke volume (SV).

RESULTS

Sixteen studies that used disk summation (637 subjects) and three studies that used three-dimensional reconstruction were included. For the 16 studies, the pooled standard mean differences (95% confidence interval) were 1.04 (- 2.59, 4.67) for EDV, 1.22 (1.50, 3.95) for ESV, - 0.65 (- 2.60, 1.29) for RVEF, and - 0.37 (- 3.64, 2.90) for SV. The overall correlation coefficient (r) values were 0.98 for EDV, 0.95 for ESV, 0.98 for RVEF, and 0.97 for SV. The mean difference between the two methods was not statistically significant (overall effect Z test, p > 0.1).

CONCLUSION

CT can assess RVF with accuracy comparable to that of MRI. Thus, CT is a valid alternative to MRI.

KEY POINTS

• CT could help clinicians to assess RVF as accurately as MRI can, with satisfactory repeatability.

Effect of Dual-Source Radiofrequency Transmission on Left Ventricular Measurements and Measurement Reproducibility at 3.0 T Cardiac MR Imaging: Comparison with Conventional Single-Source Transmission Reference

RATIONALE AND OBJECTIVES

To prospectively assess effect of dual-source radiofrequency (RF) transmission on left ventricular (LV) measurements and measurements reproducibility at 3.0 T MR using balanced steady-state free precession (b-SSFP) cine imaging, compared to the conventional single-source RF transmission reference approach.

MATERIALS AND METHODS

Cardiac b-SSFP cine imaging was performed in 19 subjects at 3.0 T MR equipped with dual-source RF transmission. All images were analyzed to obtain LV end-diastolic volume, end-systolic volume, stroke volume, ejection fraction, mass, LV end-diastolic inferior wall thickness, and interventricular septal thickness. The difference of all LV measurements between the two imaging techniques was tested with the paired t test and the intertechnique agreement was tested through linear regression and Bland-Altman analyses. Additionally, repeated LV measurements were performed to determine intra and interobserver variability with the Bland-Altman method, the 95% limits of agreement, the coefficient of variation (CV) and the intraclass correlation coefficient.

RESULTS

Compared to conventional single-source, dual-source slightly overestimated end-diastolic volume, end-systolic volume, and stroke volume (mean differences, 3.9 mL ± 9.7, 1.1 mL ± 2.6, and 2.8 mL ± 9.1, respectively; p > 0.05), resulting in a small but significant positive bias in ejection fraction (1.5% ± 2.6; p = 0.021). Mass was significantly smaller with dual-source than with single-source (-4.0 g ± 6.5, p = 0.001). Dual-source slightly underestimated interventricular septal thickness (-0.29 mm ± 0.6, p = 0.067) and significantly underestimated LV end-diastolic inferior wall thickness (-0.55 mm ± 0.4, p < 0.0001). The two techniques in measurements correlated highly (r² = 0.81 to 0.96, p < 0.0001). Intra and interobserver variability in dual-source measurements was much lower than that in single-source, and variability values were <14.0%.

CONCLUSION

Improved image quality of b-SSFP cine imaging at 3.0 T MR with dual-source RF transmission may provide more reproducible LV measurements compared to conventional single-source approach. Dual-source RF transmission also provides a reasonable estimate of the LV measurements.

Retrospective Electrocardiography-Gated Real-Time Cardiac Cine MRI at 3T: Comparison with Conventional Segmented Cine MRI

Objective

Segmented cardiac cine magnetic resonance imaging (MRI) is the gold standard for cardiac ventricular volumetric assessment. In patients with difficulty in breath-holding or arrhythmia, this technique may generate images with inadequate quality for diagnosis. Real-time cardiac cine MRI has been developed to address this limitation. We aimed to assess the performance of retrospective electrocardiography-gated real-time cine MRI at 3T for left ventricular (LV) volume and mass measurement.

Materials and Methods

Fifty-one patients were consecutively enrolled. A series of short-axis cine images covering the entire left ventricle using both segmented and real-time balanced steady-state free precession cardiac cine MRI were obtained. End-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV), ejection fraction (EF), and LV mass were measured. The agreement and correlation of the parameters were assessed. Additionally, image quality was evaluated using European CMR Registry (Euro-CMR) score and structure visibility rating.

Results

In patients without difficulty in breath-holding or arrhythmia, no significant difference was found in Euro-CMR score between the two techniques (0.3 ± 0.7 vs. 0.3 ± 0.5, p > 0.05). Good agreements and correlations were found between the techniques for measuring EDV, ESV, EF, SV, and LV mass. In patients with difficulty in breath-holding or arrhythmia, segmented cine MRI had a significant higher Euro-CMR score (2.3 ± 1.2 vs. 0.4 ± 0.5, p < 0.001).

Conclusion

Real-time cine MRI at 3T allowed the assessment of LV volume with high accuracy and showed a significantly better image quality compared to that of segmented cine MRI in patients with difficulty in breath-holding and arrhythmia.

Paravalvular Regurgitation After Transcatheter Aortic Valve Replacement: Is the Problem Solved?

Paravalvular regurgitation is a frequent complication after transcatheter aortic valve replacement and its association with worse outcomes depends on the degree of its severity. Despite substantial improvement in transcatheter heart valve design, sizing and implantation technique, moderate or severe paravalvular regurgitation still occurs in 2% to 7% of patients and is associated with a more than 2-fold increase in mortality. This review provides a state-of-the-art approach to (i) paravalvular regurgitation prevention by optimizing patient selection, valve sizing, and positioning and (ii) the detection, quantitation and management of paravalvular regurgitation during and after valve implantation.

High-throughput gadobutrol-enhanced CMR: a time and dose optimization study

BACKGROUND

Reducing time and contrast agent doses are important goals to provide cost-efficient cardiovascular magnetic resonance (CMR) imaging. Limited information is available regarding the feasibility of evaluating left ventricular (LV) function after gadobutrol injection as well as defining the lowest dose for high quality scar imaging. We sought to evaluate both aspects separately and systematically to provide an optimized protocol for contrast-enhanced CMR (CE-CMR) using gadobutrol.

METHODS

This is a prospective, randomized, single-blind cross-over study performed in two different populations. The first population consisted of 30 patients with general indications for a rest CE-CMR who underwent cine-imaging before and immediately after intravenous administration of 0.1 mmol/kg body-weight of gadobutrol. Quantitative assessment of LV volumes and function was performed by the same reader in a randomized and blinded fashion. The second population was composed of 30 patients with indication to late gadolinium enhancement (LGE) imaging, which was performed twice at different gadobutrol doses (0.1 mmol/kg vs. 0.2 mmol/kg) and at different time delays (5 and 10 min vs. 5, 10, 15 and 20 min), within a maximal interval of 21 days. LGE images were analysed qualitatively (contrast-to-noise ratio) and quantitatively (LGE%-of-mass).

RESULTS

Excellent correlation between pre- and post-contrast cine-imaging was found, with no difference of LV stroke volume and ejection fraction (p = 0.538 and p = 0.095, respectively). End-diastolic-volume and end-systolic-volume were measured significantly larger after contrast injection (p = 0.008 and p = 0.001, respectively), with a mean difference of 3.7 ml and 2.9 ml, respectively. LGE imaging resulted in optimal contrast-to-noise ratios 10 min post-injection for a gadobutrol dose of 0.1 mmol/kg body-weight and 20 min for a dose of 0.2 mmol/kg body-weight. At these time points LGE quantification did not significantly differ (0.1 mmol/kg: 11% (16.4); 0.2 mmol/kg: 12% (14.5); p = 0.059), showing excellent correlation (ICC = 0.957; p < 0.001).

CONCLUSION

A standardized CE-CMR rest protocol giving a dose of 0.1 mmol/kg of gadobutrol before cine-imaging and performing LGE 10 min after injection represents a fast low-dose protocol without significant loss of information in comparison to a longer protocol with cine-imaging before contrast injection and a higher dose of gadobutrol. This approach allows to reduce examination time and costs as well as minimize contrast-agent exposure.

CNR considerations for rapid real-time MRI tumor tracking in radiotherapy hybrid devices: Effects of B0 field strength

PURPOSE

This work examines the subject of contrast-to-noise ratio (CNR), specifically between tumor and tissue background, and its dependence on the MRI field strength, B0. This examination is motivated by the recent interest and developments in MRI/radiotherapy hybrids where real-time imaging can be used to guide treatment beams. The ability to distinguish a tumor from background tissue is of primary importance in this field, and this work seeks to elucidate the complex relationship between the CNR and B0 that is too often assumed to be purely linear.

METHODS

Experimentally based models of B0-dependant relaxation for various tumor and normal tissues from the literature were used in conjunction with signal equations for MR sequences suitable for rapid real-time imaging to develop field-dependent predictions for CNR. These CNR models were developed for liver, lung, breast, glioma, and kidney tumors for spoiled gradient-echo, balanced steady-state free precession (bSSFP), and single-shot half-Fourier fast spin echo sequences.

RESULTS

Due to the pattern in which the relaxation properties of tissues are found to vary over B0 field (specifically the T1 time), there was always an improved CNR at lower fields compared to linear dependency. Further, in some tumor sites, the CNR at lower fields was found to be comparable to, or sometimes higher than those at higher fields (i.e., bSSFP CNR for glioma, kidney, and liver tumors).

CONCLUSIONS

In terms of CNR, lower B0 fields have been shown to perform as well or better than higher fields for some tumor sites due to superior T1 contrast. In other sites this effect was less pronounced, reversing the CNR advantage. This complex relationship between CNR and B0 reveals both low and high magnetic fields as viable options for tumor tracking in MRI/radiotherapy hybrids.

Cardiac Imaging in Heart Failure with Comorbidities

Imaging modalities stand at the frontiers for progress in congestive heart failure (CHF) screening, risk stratification and monitoring. Advancements in echocardiography (ECHO) and Magnetic Resonance Imaging (MRI) have allowed for improved tissue characterizations, cardiac motion analysis, and cardiac performance analysis under stress. Common cardiac comorbidities such as hypertension, metabolic syndromes and chronic renal failure contribute to cardiac remodeling, sharing similar pathophysiological mechanisms starting with interstitial changes, structural changes and finally clinical CHF. These imaging techniques can potentially detect changes earlier. Such information could have clinical benefits for screening, planning preventive therapies and risk stratifying patients. Imaging reports have often focused on traditional measures without factoring these novel parameters. This review is aimed at providing a synopsis on how we can use this information to assess and monitor improvements for CHF with comorbidities.

Usefulness of Combined Functional Assessment by Cardiac Magnetic Resonance and Tissue Characterization Versus Task Force Criteria for Diagnosis of Arrhythmogenic Right Ventricular Cardiomyopathy

Current task force criteria (TFC) of cardiac magnetic resonance (CMR) for the diagnosis of arrhythmogenic right ventricular cardiomyopathy (ARVC/D) were generated by comparing probands (mean age of 44 years) to healthy participants of the multi-ethnic study of atherosclerosis (mean age of 60 years). These age differences may be a selection bias because right ventricular end-diastolic volume index decreases 4.6% per decade. Moreover, fat infiltration and late gadolinium enhancement were not included. We evaluated the diagnostic accuracy of TFC using the same methodology used by the task force but comparing probands and age- and gender-matched healthy controls and considering also other morphofunctional and tissue abnormalities detected by CMR. Forty-seven probands with previous diagnosis of ARVC/D (excluding probands if CMR was used for diagnosis) were compared with 216 age- and gender-matched healthy controls. TFC had optimal specificity (100%) but poor sensitivity (20% for major and 13% for minor criteria). The presence of any pre- and post-contrast signal abnormalities had 100% specificity and 81% sensitivity. The best diagnostic accuracy (98%) was achieved by the combined evaluation of any right ventricular wall motion abnormality (excluding hypokinesia) with any signal abnormality (including left ventricular fat infiltration and late gadolinium enhancement) yielding a 100% specificity and 96% sensitivity. Left ventricular was involved in 45% of the probands. Current TFC for CMR presented optimal specificity but poor sensitivity to identify patient with ARVC/D. Signal and wall motion parameters of CMR should be considered together to achieve the best diagnostic accuracy for the diagnosis of ARVC/D.

Myocardial T1-mapping at 3T using saturation-recovery: reference values, precision and comparison with MOLLI

BACKGROUND

Myocardial T1-mapping recently emerged as a promising quantitative method for non-invasive tissue characterization in numerous cardiomyopathies. Commonly performed with an inversion-recovery (IR) magnetization preparation at 1.5T, the application at 3T has gained due to increased quantification precision. Alternatively, saturation-recovery (SR) T1-mapping has recently been introduced at 1.5T for improved accuracy. Thus, the purpose of this study is to investigate the robustness and precision of SR T1-mapping at 3T and to establish accurate reference values for native T1-times and extracellular volume fraction (ECV) of healthy myocardium.

METHODS

Balanced Steady-State Free-Precession (bSSFP) Saturation-Pulse Prepared Heart-rate independent Inversion-REcovery (SAPPHIRE) and Saturation-recovery Single-SHot Acquisition (SASHA) T1-mapping were compared with the Modified Look-Locker inversion recovery (MOLLI) sequence at 3T. Accuracy and precision were studied in phantom. Native and post-contrast T1-times and regional ECV were determined in 20 healthy subjects (10 men, 27 ± 5 years). Subjective image quality, susceptibility artifact rating, in-vivo precision and reproducibility were analyzed.

RESULTS

SR T1-mapping showed <4 % deviation from the spin-echo reference in phantom in the range of T1 = 100-2300 ms. The average quality and artifact scores of the T1-mapping methods were: MOLLI:3.4/3.6, SAPPHIRE:3.1/3.4, SASHA:2.9/3.2; (1: poor - 4: excellent/1: strong - 4: none). SAPPHIRE and SASHA yielded significantly higher T1-times (SAPPHIRE: 1578 ± 42 ms, SASHA: 1523 ± 46 ms), in-vivo T1-time variation (SAPPHIRE: 60.1 ± 8.7 ms, SASHA: 70.0 ± 9.3 ms) and lower ECV-values (SAPPHIRE: 0.20 ± 0.02, SASHA: 0.21 ± 0.03) compared with MOLLI (T1: 1181 ± 47 ms, ECV: 0.26 ± 0.03, Precision: 53.7 ± 8.1 ms). No significant difference was found in the inter-subject variability of T1-times or ECV-values (T1: p = 0.90, ECV: p = 0.78), the observer agreement (inter: p > 0.19; intra: p > 0.09) or consistency (inter: p > 0.07; intra: p > 0.17) between the three methods.

CONCLUSIONS

Saturation-recovery T1-mapping at 3T yields higher accuracy, comparable inter-subject, inter- and intra-observer variability and less than 30 % precision-loss compared to MOLLI.

Compressed sensing real-time cine cardiovascular magnetic resonance: accurate assessment of left ventricular function in a single-breath-hold

BACKGROUND

Cardiovascular cine magnetic resonance (CMR) accelerated by compressed sensing (CS) is used to assess left ventricular (LV) function. However, it is difficult for prospective CS cine CMR to capture the complete end-diastolic phase, which can lead to underestimation of the end-diastolic volume (EDV), stroke volume (SV), and ejection fraction (EF), compared to retrospective standard cine CMR. This prospective study aimed to evaluate the diagnostic quality and accuracy of single-breath-hold full cardiac cycle CS cine CMR, acquired over two heart beats, to quantify LV volume in comparison to multi-breath-hold standard cine CMR.

METHODS

Eighty-one participants underwent standard segmented breath-hold cine and CS real-time cine CMR examinations to obtain a stack of eight contiguous short-axis images with same high spatial (1.7 × 1.7 mm(2)) and temporal resolution (41 ms). Two radiologists independently performed qualitative analysis of image quality (score, 1 [i.e., "nondiagnostic"] to 5 [i.e., "excellent"]) and quantitative analysis of the LV volume measurements.

RESULTS

The total examination time was 113 ± 7 s for standard cine CMR and 24 ± 4 s for CS cine CMR (p < 0.0001). The CS cine image quality was slightly lower than standard cine (4.8 ± 0.5 for standard vs. 4.4 ± 0.5 for CS; p < 0.0001). However, all image quality scores for CS cine were above 4 (i.e., good). No significant differences existed between standard and CS cine MR for all quantitative LV measurements. The mean differences with 95 % confidence interval (CI), based on Bland-Altman analysis, were 1.3 mL (95 % CI, -14.6 - 17.2) for LV end-diastolic volume, 0.2 mL (95 % CI, -9.8 to10.3) for LV end-systolic volume, 1.1 mL (95 % CI, -10.5 to 12.7) for LV stroke volume, 1.0 g (95 % CI, -11.2 to 13.3) for LV mass, and 0.4 % (95 % CI, -4.8 - 5.6) for LV ejection fraction. The interobserver and intraobserver variability for CS cine MR ranged from -4.8 - 1.6 % and from -7.3 - 9.3 %, respectively, with slopes of the regressions ranging 0.88-1.0 and 0.86-1.03, respectively.

CONCLUSIONS

Single-breath-hold full cardiac cycle CS real-time cine CMR could evaluate LV volume with excellent accuracy. It may replace multi-breath-hold standard cine CMR.

Comparison of 3 T and 1.5 T for T2* magnetic resonance of tissue iron

BACKGROUND

T2* magnetic resonance of tissue iron concentration has improved the outcome of transfusion dependant anaemia patients. Clinical evaluation is performed at 1.5 T but scanners operating at 3 T are increasing in numbers. There is a paucity of data on the relative merits of iron quantification at 3 T vs 1.5 T.

METHODS

A total of 104 transfusion dependent anaemia patients and 20 normal volunteers were prospectively recruited to undergo cardiac and liver T2* assessment at both 1.5 T and 3 T. Intra-observer, inter-observer and inter-study reproducibility analysis were performed on 20 randomly selected patients for cardiac and liver T2*.

RESULTS

Association between heart and liver T2* at 1.5 T and 3 T was non-linear with good fit (R (2) = 0.954, p < 0.001 for heart white-blood (WB) imaging; R (2) = 0.931, p < 0.001 for heart black-blood (BB) imaging; R (2) = 0.993, p < 0.001 for liver imaging). R2* approximately doubled between 1.5 T and 3 T with linear fits for both heart and liver (94, 94 and 105 % respectively). Coefficients of variation for intra- and inter-observer reproducibility, as well as inter-study reproducibility trended to be less good at 3 T (3.5 to 6.5 %) than at 1.5 T (1.4 to 5.7 %) for both heart and liver T2*. Artefact scores for the heart were significantly worse with the 3 T BB sequence (median 4, IQR 2-5) compared with the 1.5 T BB sequence (4 [3-5], p = 0.007).

CONCLUSION

Heart and liver T2* and R2* at 3 T show close association with 1.5 T values, but there were more artefacts at 3 T and trends to lower reproducibility causing difficulty in quantifying low T2* values with high tissue iron. Therefore T2* imaging at 1.5 T remains the gold standard for clinical practice. However, in centres where only 3 T is available, equivalent values at 1.5 T may be approximated by halving the 3 T tissue R2* with subsequent conversion to T2*.

Cardiac magnetic resonance 'virtual catheterization' for the quantification of valvular regurgitations and cardiac shunt

Cardiac magnetic resonance (CMR) is considered the gold-standard noninvasive technique for the quantification of ventricular volumes by cine-imaging and of vascular flows by velocity-encoded phase contrast (VENC). In routine CMR scans, it is common to found clinical conditions, as valve regurgitations and cardiac shunts, producing a volume overload and significant mismatch between the right and left ventricular stroke volumes (RSV and LSV). In the presence of a valve regurgitation, the volume overload involves the respective ventricular chamber, whereas in cardiac shunts, the location of the volume overload depends on the site of the anatomic defect. Moreover, when a cardiac shunt is present, pulmonary and systemic cardiac outputs are different (Qp/Qs < 1 or Qp/Qs > 1), whereas in the presence of valve regurgitation, Qp/Qs = 1. Therefore, by combining the cine-imaging with the VENC technique, it is possible to investigate the cardiac physiology underlying different pathological conditions producing volume overload, and to quantify this overload (the regurgitant volume and/or shunt volume). In this report, we discussed the technical, theoretical and methodological aspects of this sort of 'virtual catheterization' by CMR, providing a simple algorithm to make the correct diagnosis.

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

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

Assessment of the precision and reproducibility of ventricular volume, function, and mass measurements with ferumoxytol-enhanced 4D flow MRI

PURPOSE

To compare the precision and interobserver agreement of ventricular volume, function, and mass quantification by 3D time-resolved (4D) flow MRI relative to cine steady-state free precession (SSFP).

MATERIALS AND METHODS

With Institutional Research Board approval, informed consent, and HIPAA compliance, 22 consecutive patients with congenital heart disease (CHD) (10 males, 6.4 ± 4.8 years) referred for 3T ferumoxytol-enhanced cardiac MRI were prospectively recruited. Complete ventricular coverage with standard 2D short-axis cine SSFP and whole chest coverage with axial 4D flow were obtained. Two blinded radiologists independently segmented images for left ventricular (LV) and right ventricular (RV) myocardium at end systole (ES) and end diastole (ED). Statistical analysis included linear regression, analysis of variance (ANOVA), Bland-Altman (BA) analysis, and intraclass correlation (ICC).

RESULTS

Significant positive correlations were found between 4D flow and SSFP for ventricular volumes (r = 0.808-0.972, P < 0.001), ejection fraction (EF) (r = 0.900-928, P < 0.001), and mass (r = 0.884-0.934, P < 0.001). BA relative limits of agreement for both ventricles were between -52% to 34% for volumes, -29% to 27% for EF, and -41% to 48% for mass, with wider limits of agreement for the RV compared to the LV. There was no significant difference between techniques with respect to mean square difference of ED-ES mass for either LV (F = 2.05, P = 0.159) or RV (F = 0.625, P = 0.434). Interobserver agreement was moderate to good with both 4D flow (ICC 0.523-0.993) and SSFP (ICC 0.619-0.982), with overlapping confidence intervals.

CONCLUSION

Quantification of ventricular volume, function, and mass can be accomplished with 4D flow MRI with precision and interobserver agreement comparable to that of cine SSFP. J. Magn. Reson. Imaging 2016;44:383-392.

Regional ejection fraction and regional area strain for left ventricular function assessment in male patients after first-time myocardial infarction

In this work, we present a method to assess left ventricle (LV) regional function from cardiac magnetic resonance (CMR) imaging based on the regional ejection fraction (REF) and regional area strain (RAS). CMR scans were performed for 30 patients after first-time myocardial infarction (MI) and nine age- and sex-matched healthy volunteers. The CMR images were processed to reconstruct three-dimensional LV geometry, and the REF and RAS in a 16-segment model were computed using our proposed methodology. The method of computing the REF was tested and shown to be robust against variation in user input. Furthermore, analysis of data was feasible in all patients and healthy volunteers without any exclusions. The REF correlated well with the RAS in a nonlinear manner (quadratic fit-R(2) = 0.88). In patients after first-time MI, the REF and RAS were significantly reduced across all 16 segments (REF: p < 0.05; RAS: p < 0.01). Moreover, the REF and RAS significantly decreased with the extent of transmural scar obtained from late gadolinium-enhanced CMR images. In addition, we show that the REF and RAS can be used to identify regions with compromised function in the patients with preserved global ejection fraction with reasonable accuracy (more than 78%). These preliminary results confirmed the validity of our approach for accurate analysis of LV regional function. Our approach potentially offers physicians new insights into the local characteristics of the myocardial mechanics after a MI.

Cardiotoxicity due to chemotherapy: role of cardiac imaging

The identification of patients at risk of cardiac toxicity (cardiotoxicity) from cancer therapy is challenging. There is an increasing focus on early detection of cardiotoxicity such that interventions can be instituted to prevent advanced heart failure. Clinical risk prediction tools are limited and clinical symptoms are not specific. Direct assessment of myocardial function before and during cancer treatment using cardiac imaging appears to be an objective method to identify patients at risk. Although, multiple imaging modalities and measures of cardiac function are available, the best modality or the optimal measure of function is unknown. Measurement of left ventricular ejection fraction is most commonly used; however, growing literature suggests that it is inadequate for the detection of early cardiac injury. Other measures include left ventricular diastolic function, myocardial deformation, and myocardial tissue characterization. This review will provide an overview of the clinically available measures for the assessment of cardiotoxicity.

Relationship of T2-Weighted MRI Myocardial Hyperintensity and the Ischemic Area-At-Risk

RATIONALE

After acute myocardial infarction (MI), delineating the area-at-risk (AAR) is crucial for measuring how much, if any, ischemic myocardium has been salvaged. T2-weighted MRI is promoted as an excellent method to delineate the AAR. However, the evidence supporting the validity of this method to measure the AAR is indirect, and it has never been validated with direct anatomic measurements.

OBJECTIVE

To determine whether T2-weighted MRI delineates the AAR.

METHODS AND RESULTS

Twenty-one canines and 24 patients with acute MI were studied. We compared bright-blood and black-blood T2-weighted MRI with images of the AAR and MI by histopathology in canines and with MI by in vivo delayed-enhancement MRI in canines and patients. Abnormal regions on MRI and pathology were compared by (a) quantitative measurement of the transmural-extent of the abnormality and (b) picture matching of contours. We found no relationship between the transmural-extent of T2-hyperintense regions and that of the AAR (bright-blood-T2: r=0.06, P=0.69; black-blood-T2: r=0.01, P=0.97). Instead, there was a strong correlation with that of infarction (bright-blood-T2: r=0.94, P<0.0001; black-blood-T2: r=0.95, P<0.0001). Additionally, contour analysis demonstrated a fingerprint match of T2-hyperintense regions with the intricate contour of infarcted regions by delayed-enhancement MRI. Similarly, in patients there was a close correspondence between contours of T2-hyperintense and infarcted regions, and the transmural-extent of these regions were highly correlated (bright-blood-T2: r=0.82, P<0.0001; black-blood-T2: r=0.83, P<0.0001).

CONCLUSION

T2-weighted MRI does not depict the AAR. Accordingly, T2-weighted MRI should not be used to measure myocardial salvage, either to inform patient management decisions or to evaluate novel therapies for acute MI.

Three-dimensional cardiac cine imaging using the kat ARC acceleration: Initial experience in clinical adult patients at 3T

OBJECTIVE

Three-dimensional cardiac cine imaging has demonstrated promising clinical 1.5-Tesla results; however, its application to 3T scanners has been limited because of the higher sensitivity to off-resonance artifacts. The aim of this study was to apply 3D cardiac cine imaging during a single breath hold in clinical patients on a 3T scanner using the kat ARC (k- and adaptive-t auto-calibrating reconstruction for Cartesian sampling) technique and to evaluate the interchangeability between 2D and 3D cine imaging for cardiac functional analysis and detection of abnormalities in regional wall motion.

METHODS

Following institutional review board approval, we obtained 2D cine images with an acceleration factor of two during multiple breath holds and 3D cine images with a net scan acceleration factor of 7.7 during a single breath hold in 20 patients using a 3T unit. Two readers independently evaluated the wall motion of the left ventricle (LV) using a 5-point scale, and the consistency in the detection of regional wall motion abnormality between 2D and 3D cine was analyzed by Cohen's kappa test. The LV volume was calculated at end-diastole and end-systole (LVEDV, LVESV); the ejection fraction (LVEF) and myocardial weight (LVmass) were also calculated. The relationship between functional parameters calculated for 2D and 3D cine images was analyzed using Pearson's correlation analysis. The bias and 95% limit of agreement (LA) were calculated using Bland-Altman plots. In addition, a qualitative evaluation of image quality was performed with regard to the myocardium-blood contrast, noise level and boundary definition.

RESULTS

Despite slight degradation in image quality for 3D cine, excellent agreement was obtained for the detection of wall motion abnormalities between 2D and 3D cine images (κ=0.84 and 0.94 for each reader). Excellent correlations between the two imaging methods were shown for the evaluation of functional parameters (r>0.97). Slight differences in LVEDV, LVESV, LVEF and LVmass were observed, with average values of 1.6±8.9mL, -0.6±5.9mL, 1.4±3.6%, and 1.3±8.7g, respectively.

CONCLUSIONS

Images obtained using the kat ARC 3D and conventional 2D cine techniques were equivalent in the detection of regional wall motion abnormalities and the evaluation of cardiac functional parameters.